(Spare Parts) SP-2.5 F5J Model
I took a long break from building but here I am back with a bang!
In the resent Nats I saw my 1.8m Cumulus with S400 brushed motor is losing the technology war in the F5J competition and is not performing as well as in the past. I was flying this little model for 8 years now and will prolly pass it on to my little boy as it is still far from retirement.
I had a pair of beautiful built-up 2.5m wings from many years back of a model that flew well, but the fuz was useless and I disposed of it. The airfoil is the old E205 but still very useful for this purpose. The plan was designed round a 350-400 Watt setup. For F5J with brushless the launch time with motor on, should be not more than 15 seconds to be competitive. I believe as the technology is catching up (or is that the checkbook war) this time will decrease closer to 5 seconds. There is a balance between battery capacity and AUW of the model. One of my goals was to prove that I can build a competitive model on a relative low budget. The electric equipment now readily available do make this possible. An outrunner with a 3 sell 2100mAh Lipo would be the power train. The aim was a model weighing not more than 1.2kg. MotoCalc show that I can prolly go vertical with this setup. The logic is that a light airframe needs less power for launching which imply lower cost setup.
And so a model built from Spare Parts was born. The fuz consists of a boom and pod. The boom is from a Bubble Dancer which I replace after I found a small crack in it. The pod was made from fiber glass with the lost foam method. It was made wide enough to fit the battery pack and be able to move it around until the CG is spot on. It came out more spectacular than I expected. The tail feathers was built from the Bubble Dancer plan with all moving elevator. The servos for rudder and elevator were installed in the rudder to keep things simple. I used a pair of Graupner C2041 micro servos which I had for 8 years. It make sometimes sense to pay that little extra for a pair of servos as these servos received abuse in foam electric models for the past 8 years and is still slop free. The airframe with no electronics came out 680g which is not bad for a 2.5m wingspan. The original spring steel wing joiner was dropped for a light carbon replacement and as the battery can be utilised to get the CG right, no extra lead is required, even with servos in tail. All the bits and covering material came from my off-cuts box. I enjoyed working with balsa again and Oracover is still the best covering material I have used.
At the recent Nats I received two sets of epoxy as a prize sponsored by AMT. It is the "Smooth-on" Super Instant and Metalset A4. I am experimenting with it and find that it is far superior to the other similar epoxies from hardware shops. I used it in various applications like gluing the balsa rudder to the carbon boom, the boom to the fuz, the carbon V-mount for elevator to boom, firewall to fuz, wing mounting nuts to fuz and a box full of broken toys are also fixed now.
Test flights showed that this will become one of my favorites for any time flying. I did testing with a smaller prop as I am still waiting for the correct prop blades. With this 3 sizes smaller blades I put in only 220W and the model climbed very well to hight. With the correct prop this will change to 350W. The conditions were very windy on my first day of flight and I still have to finish a few thing on the model, but it flew beautifully. I will give it its first competition taste on the 3rd August as Lionel promised he will introduce one slot per round of F5J in the HTL. The one aspect I enjoy already is the small load traveling to the field and the easy setup to start chasing thermals. Once finished experimenting I will put up all the details of the electric setup on my Blog with more detailed photos.
So to summarize, if you have a Sagitta or Aqualla or Apogee or any 70's glider hanging in your garage, which you are to embarrassed to bring to the HTL ,then this is the method to restore its glory.
Cheers
Gert
The Motor setup at the moment is:
E-Flite Power 10 Outrunner 1100KV
FlightPower 2500 3S lite
12x6 prop for 1434g of thrust
This pull 30 A
In the resent Nats I saw my 1.8m Cumulus with S400 brushed motor is losing the technology war in the F5J competition and is not performing as well as in the past. I was flying this little model for 8 years now and will prolly pass it on to my little boy as it is still far from retirement.
I had a pair of beautiful built-up 2.5m wings from many years back of a model that flew well, but the fuz was useless and I disposed of it. The airfoil is the old E205 but still very useful for this purpose. The plan was designed round a 350-400 Watt setup. For F5J with brushless the launch time with motor on, should be not more than 15 seconds to be competitive. I believe as the technology is catching up (or is that the checkbook war) this time will decrease closer to 5 seconds. There is a balance between battery capacity and AUW of the model. One of my goals was to prove that I can build a competitive model on a relative low budget. The electric equipment now readily available do make this possible. An outrunner with a 3 sell 2100mAh Lipo would be the power train. The aim was a model weighing not more than 1.2kg. MotoCalc show that I can prolly go vertical with this setup. The logic is that a light airframe needs less power for launching which imply lower cost setup.
And so a model built from Spare Parts was born. The fuz consists of a boom and pod. The boom is from a Bubble Dancer which I replace after I found a small crack in it. The pod was made from fiber glass with the lost foam method. It was made wide enough to fit the battery pack and be able to move it around until the CG is spot on. It came out more spectacular than I expected. The tail feathers was built from the Bubble Dancer plan with all moving elevator. The servos for rudder and elevator were installed in the rudder to keep things simple. I used a pair of Graupner C2041 micro servos which I had for 8 years. It make sometimes sense to pay that little extra for a pair of servos as these servos received abuse in foam electric models for the past 8 years and is still slop free. The airframe with no electronics came out 680g which is not bad for a 2.5m wingspan. The original spring steel wing joiner was dropped for a light carbon replacement and as the battery can be utilised to get the CG right, no extra lead is required, even with servos in tail. All the bits and covering material came from my off-cuts box. I enjoyed working with balsa again and Oracover is still the best covering material I have used.
At the recent Nats I received two sets of epoxy as a prize sponsored by AMT. It is the "Smooth-on" Super Instant and Metalset A4. I am experimenting with it and find that it is far superior to the other similar epoxies from hardware shops. I used it in various applications like gluing the balsa rudder to the carbon boom, the boom to the fuz, the carbon V-mount for elevator to boom, firewall to fuz, wing mounting nuts to fuz and a box full of broken toys are also fixed now.
Test flights showed that this will become one of my favorites for any time flying. I did testing with a smaller prop as I am still waiting for the correct prop blades. With this 3 sizes smaller blades I put in only 220W and the model climbed very well to hight. With the correct prop this will change to 350W. The conditions were very windy on my first day of flight and I still have to finish a few thing on the model, but it flew beautifully. I will give it its first competition taste on the 3rd August as Lionel promised he will introduce one slot per round of F5J in the HTL. The one aspect I enjoy already is the small load traveling to the field and the easy setup to start chasing thermals. Once finished experimenting I will put up all the details of the electric setup on my Blog with more detailed photos.
So to summarize, if you have a Sagitta or Aqualla or Apogee or any 70's glider hanging in your garage, which you are to embarrassed to bring to the HTL ,then this is the method to restore its glory.
Cheers
Gert
The Motor setup at the moment is:
E-Flite Power 10 Outrunner 1100KV
FlightPower 2500 3S lite
12x6 prop for 1434g of thrust
This pull 30 A
New Toy
Yes I am guilty! Have not updated my blog for some time and I have not finished the Supra as promised. But I have a new toy. I took the plunge with last years bonus and bought a molded Supra. Any way here is some photos taken by Johan Snyman. Thanks Johan
I flew my postals on the Friday 1st Feb ! 14H30 the afternoon. My weekends
is very full and on the first day of February I saw we had good air and
decided to do it. At that stage my new moulded Supra (the homebuilt Supra is
still to be finished) was not properly setup for landings. The first landing
was 15m, then 10m, then 6 m short then I went 6 meter past the spot with the final landing on the spot. After each flight I was changing flap curves
until I got it "spot-on". At this stage I am very satisfied with the new
model and it suits my type of flying (slow and cautious) very well.
Cheers
Gert
I flew my postals on the Friday 1st Feb ! 14H30 the afternoon. My weekends
is very full and on the first day of February I saw we had good air and
decided to do it. At that stage my new moulded Supra (the homebuilt Supra is
still to be finished) was not properly setup for landings. The first landing
was 15m, then 10m, then 6 m short then I went 6 meter past the spot with the final landing on the spot. After each flight I was changing flap curves
until I got it "spot-on". At this stage I am very satisfied with the new
model and it suits my type of flying (slow and cautious) very well.
Cheers
Gert
Supra Fuz Building
By the time I am finished with this Supra there will prolly be a new toy on the horizon. It is part of the hobby/sport for me to do the building so I can just as well take my time, but I need a tool for next years HTL. I gave the league a skip this year but miss all the old friends and healthy competition atmosphere, so be warned I may be back soon!
I have finished the fuz and all of its parts during the past 2 months. After much consideration and some experience from my previous Supra project I decided to change the pylon at the base of the wing. I have added a wider flange/faring. The reason is to improve the strength of the pylon. Due to torsional twist during hard landings the pylon is prone to damage. I have made a base for the wing from 200g Carbon which was done on the finished wing. The next step was to glue this base to the fuz and added a fairing with lots of carbon tow and some filler. The base have tows running 45 degrees and the carbon tows running parallel along the fuz sides. I hope this will add enough strength in the needed directions when the fuz stops movement and the 3.4m wing want to twist. The added weight for this modification was well worth it.
The push rods is 2mm carbon and sleeves supplied by Dion Liebenberg. I could
not get the teflon sleeves in time and decided to use the white sleeves. The rest of the installations is not rocket science and I think the pictures tell the story.
The completed fuz with rudder and elevator and servos is around 450g.
Cheers
Gert
I have finished the fuz and all of its parts during the past 2 months. After much consideration and some experience from my previous Supra project I decided to change the pylon at the base of the wing. I have added a wider flange/faring. The reason is to improve the strength of the pylon. Due to torsional twist during hard landings the pylon is prone to damage. I have made a base for the wing from 200g Carbon which was done on the finished wing. The next step was to glue this base to the fuz and added a fairing with lots of carbon tow and some filler. The base have tows running 45 degrees and the carbon tows running parallel along the fuz sides. I hope this will add enough strength in the needed directions when the fuz stops movement and the 3.4m wing want to twist. The added weight for this modification was well worth it.
The push rods is 2mm carbon and sleeves supplied by Dion Liebenberg. I could
not get the teflon sleeves in time and decided to use the white sleeves. The rest of the installations is not rocket science and I think the pictures tell the story.
The completed fuz with rudder and elevator and servos is around 450g.
Cheers
Gert
CNC Foam Cutter
Due to the extreme cold here in Secunda I can not continue with the Supra as my workshop is too cold in the evenings to work with epoxy resin. I decided to finish the CNC cutter as it is already a three year project. I have collected the parts over a long period but finally with a bit of effort in the warmth of my study I did the last few solder joints and it is working.
The cutter consists of a table which have the mechanics driven by 4 stepper motors, a electronics board which is the interface between the PC software and stepper motors, a old Pentium 100 which is still useful for this purpose and a powersupply for the foam cutter bow. For the interface board I used the MM2001 board design which was made for me by a electronic shop in Vdb. I had to solder all the components to the printed circuit board and program the PIC processor integrated circuit. Details of the electronics and
software I used is here http://gm.cnc.free.fr/en/index.html. This board is connected to the PC via a parallel cable. There is various sources for ready built or kit form stepper motor drivers.
I have seen and used other CNC foam cutters previously and I have tried to built other mechanics previously. It took me a while before I found this simple design which is also very solid (see photos). I am very happy with the results as it is very accurate and the cuts is very smooth. The stepper motors have 200 steps and one rotation on the screw will move the wire 1mm. The sliders is ordinary drawer slides supplied by cabinet makers (thanks Evan). It takes about 5 minutes on slow speed (accurate) to cut a wing of 150mm cord. A zaggi type wing is the most difficult cut with the sweepback and taper cord. I used this type of wing to do test cuts and was successful so I believe I will be able to do most any wing. The cutter can be used to do any other form like part of fuselages or what ever you can dream up. The 45 Euro for the software is an absolute bargain taking in to account what it can do. Obviously lots of improvements can be done depending on your budget, but with this simple cutter the results is stunning.
I still need to make it tidy and safe but attached is a few pictures of the final result.
Cheers
Gert
The cutter consists of a table which have the mechanics driven by 4 stepper motors, a electronics board which is the interface between the PC software and stepper motors, a old Pentium 100 which is still useful for this purpose and a powersupply for the foam cutter bow. For the interface board I used the MM2001 board design which was made for me by a electronic shop in Vdb. I had to solder all the components to the printed circuit board and program the PIC processor integrated circuit. Details of the electronics and
software I used is here http://gm.cnc.free.fr/en/index.html. This board is connected to the PC via a parallel cable. There is various sources for ready built or kit form stepper motor drivers.
I have seen and used other CNC foam cutters previously and I have tried to built other mechanics previously. It took me a while before I found this simple design which is also very solid (see photos). I am very happy with the results as it is very accurate and the cuts is very smooth. The stepper motors have 200 steps and one rotation on the screw will move the wire 1mm. The sliders is ordinary drawer slides supplied by cabinet makers (thanks Evan). It takes about 5 minutes on slow speed (accurate) to cut a wing of 150mm cord. A zaggi type wing is the most difficult cut with the sweepback and taper cord. I used this type of wing to do test cuts and was successful so I believe I will be able to do most any wing. The cutter can be used to do any other form like part of fuselages or what ever you can dream up. The 45 Euro for the software is an absolute bargain taking in to account what it can do. Obviously lots of improvements can be done depending on your budget, but with this simple cutter the results is stunning.
I still need to make it tidy and safe but attached is a few pictures of the final result.
Cheers
Gert
Supra building: Mold making
In previous installments I have shown the plug for the pod with the pylon. I have done the mold now after many roundabouts. At first I made the plug with two halves thinking that it would be easier not to make a parting board. The result was two plug halves which were skew. I had to glue the two pieces together and do the finishing again (read lots of elbow grease). So now you know I am really not an expert and learn all the way. I made a parting board and the rest can be seen in the photos. I did not cut the board very accurate so I had to fill the cavities with clay between the plug and parting board. The complete setup took me less then an hour. What worked for me is to wax the plug and parting board and buff it by hand until it is shiny. I cover it with PVA mold release from Mica using a foam brush. When Dry I coat it with epoxy resin and fill the corners with a Carbosil mix. I found the carbosil mix should not be to thick as the bubbles do not escape then. I wait some time for the epoxy to get sticky and start with the layers of glass. I use a brush to tap it into all the corners and to make sure there is no bubbles trapped between work piece and glass.
After many thought I made a six piece mold for the fuz, nosecone and the servotray. This helps when you have to join the halves as you have access to epoxy the seam. The servotray was still a difficult shape and I made a joggle plate in order to create a offset for the one halve to fit inside the other. I fitted the plug in one half of the mold and cut a piece of 5mm hardboard to fit round the plug on top of the mold half. The gap is the sealed with body putty in order to get the shape of the plug. Once this is cured the joggle plate can be cut at the nose end in two. Position the two pieces over the mold half to create a overhang just enough for the thickness of the skin. The joggle plate worked fine but did not survive. The nose cone and fuz main part did not need this as I have lots of access space.
I used the pretty Mantis fuz up to now with my Supra wing and have some experience with the pylon mounting. Due to the hard landings we experience at the local competitions the pylon is prone to damage when the wing twist on a hard landing. I saw in one of the RCgroup forums mention is made of solutions which includes a rubbery insert between wing and pylon base. This helps prevent the wing from twisting on its base. Meanwhile I found a rubber paint which is used for coating tool handles and applied this to the base of the wing. It helped so much that my wing broke next time, plastic bolt still in one piece. Additionally I fill the pylon with 12mm thick endgrain balsa (like the way the spar works) The grain runs 90 deg with the center line of the fuz, parallel with the wing and prevent any twisting which bursts the pylon open.
I used to use acetone to clean the brush and tool, but normally the brush and acetone did not last long. I tested the Polycell brush cleaner and it works fantastic. afterwards you can clean the brush with water and it is soft again. The solvents available nowadays is brilliant! The Brush cleaner is expensive but overall I get far with it and use less brushes.
Cheers
Gert
After many thought I made a six piece mold for the fuz, nosecone and the servotray. This helps when you have to join the halves as you have access to epoxy the seam. The servotray was still a difficult shape and I made a joggle plate in order to create a offset for the one halve to fit inside the other. I fitted the plug in one half of the mold and cut a piece of 5mm hardboard to fit round the plug on top of the mold half. The gap is the sealed with body putty in order to get the shape of the plug. Once this is cured the joggle plate can be cut at the nose end in two. Position the two pieces over the mold half to create a overhang just enough for the thickness of the skin. The joggle plate worked fine but did not survive. The nose cone and fuz main part did not need this as I have lots of access space.
I used the pretty Mantis fuz up to now with my Supra wing and have some experience with the pylon mounting. Due to the hard landings we experience at the local competitions the pylon is prone to damage when the wing twist on a hard landing. I saw in one of the RCgroup forums mention is made of solutions which includes a rubbery insert between wing and pylon base. This helps prevent the wing from twisting on its base. Meanwhile I found a rubber paint which is used for coating tool handles and applied this to the base of the wing. It helped so much that my wing broke next time, plastic bolt still in one piece. Additionally I fill the pylon with 12mm thick endgrain balsa (like the way the spar works) The grain runs 90 deg with the center line of the fuz, parallel with the wing and prevent any twisting which bursts the pylon open.
I used to use acetone to clean the brush and tool, but normally the brush and acetone did not last long. I tested the Polycell brush cleaner and it works fantastic. afterwards you can clean the brush with water and it is soft again. The solvents available nowadays is brilliant! The Brush cleaner is expensive but overall I get far with it and use less brushes.
Cheers
Gert
Supra building: Wing centre panel finishing
For those who is still following here we go with the wing center section. I am progressing slowly and hope to pick up speed and still make the Nats with this model. My available building time is only a fraction of what it used to be as I have endless lists of handyman jobs to do at my new house.
I have used 62g Kevlar as the main part of the skin on Supra #2. The center section have a double-up piece on top and bottom. The bottom center where the wing would rest on the fuz I have added a piece of 90g carbon and also on the top skins where the flap servos will be mounted for reinforcement.
Kevlar do not like to be sanded afterwards so in order to get a smooth leading edge I did the following. Add a carbon tow to the leading edge using spray glue. Cover that with a strip 2cm of 86g glass along the leading edge and iron the glass to the foam core with the spray glue. This will prevent it from sliding off when resin is applied. The Kevlar skin will be placed such that it is 2-3mm from the edge of the leading edge. So when the epoxy is cured after bagging you will not sand into the Kevlar, but only the glass. I tried to take pictures of this, but it do not show clearly how it come out. The small patches of Kevlar that did land under the sanding block I used foam safe cyno to harden the frays and sanded till smooth. Overall I was pleased with the outcome.
Back to the skins: I sprayed the maylars with the colour scheme I planned for this model. I was a bit too sparingly with the white this time and the yellow of the Kevlar did show through eventually :-( Any way this model is built for performance and not looks so I will live with it and hope you will only see it from the bottom most of the time. I may consider respraying the top skin later.
Once all the preparations was done I did the vacuumbag part same as the elevator and rudder in the previous installments. Putting a 1.6m wing piece in the bag is full of obstacles and do make sure all your equipment and procedures is tested before the time. One leak can ruin a lot of hard work.
The wing center panel came out at less than 700g which is about 200g less than the first one. The stab came out 42g and the Rudder 30g. The wing feels strong and ridged. This compares to the molded version which is around 622g for wing center section and 42g and 38g for elevator and rudder. The flaps do not show any signs of flexing although very thin and the Kevlar "live" hinge is solid but very flexible.
Taking into account that I take a lot of shortcuts and do not particularly work hard at reducing the weight, I am satisfied thus far. The aim would be to have a relative competitive model at low cost which would be able to live up to the HTL with its hard landing areas.
Cheers
Gert
Photos:
1. The centre panel as it came out of the bag before trimming.
2. Foam end rib partly removed. The LE partly sanded with Carbon tow coming out.
3. LE and End rib before trimming
4. Flap cut open. The flaps was done with facing in the bag.
5. LE finished
6. Flaps finished
I have used 62g Kevlar as the main part of the skin on Supra #2. The center section have a double-up piece on top and bottom. The bottom center where the wing would rest on the fuz I have added a piece of 90g carbon and also on the top skins where the flap servos will be mounted for reinforcement.
Kevlar do not like to be sanded afterwards so in order to get a smooth leading edge I did the following. Add a carbon tow to the leading edge using spray glue. Cover that with a strip 2cm of 86g glass along the leading edge and iron the glass to the foam core with the spray glue. This will prevent it from sliding off when resin is applied. The Kevlar skin will be placed such that it is 2-3mm from the edge of the leading edge. So when the epoxy is cured after bagging you will not sand into the Kevlar, but only the glass. I tried to take pictures of this, but it do not show clearly how it come out. The small patches of Kevlar that did land under the sanding block I used foam safe cyno to harden the frays and sanded till smooth. Overall I was pleased with the outcome.
Back to the skins: I sprayed the maylars with the colour scheme I planned for this model. I was a bit too sparingly with the white this time and the yellow of the Kevlar did show through eventually :-( Any way this model is built for performance and not looks so I will live with it and hope you will only see it from the bottom most of the time. I may consider respraying the top skin later.
Once all the preparations was done I did the vacuumbag part same as the elevator and rudder in the previous installments. Putting a 1.6m wing piece in the bag is full of obstacles and do make sure all your equipment and procedures is tested before the time. One leak can ruin a lot of hard work.
The wing center panel came out at less than 700g which is about 200g less than the first one. The stab came out 42g and the Rudder 30g. The wing feels strong and ridged. This compares to the molded version which is around 622g for wing center section and 42g and 38g for elevator and rudder. The flaps do not show any signs of flexing although very thin and the Kevlar "live" hinge is solid but very flexible.
Taking into account that I take a lot of shortcuts and do not particularly work hard at reducing the weight, I am satisfied thus far. The aim would be to have a relative competitive model at low cost which would be able to live up to the HTL with its hard landing areas.
Cheers
Gert
Photos:
1. The centre panel as it came out of the bag before trimming.
2. Foam end rib partly removed. The LE partly sanded with Carbon tow coming out.
3. LE and End rib before trimming
4. Flap cut open. The flaps was done with facing in the bag.
5. LE finished
6. Flaps finished
Supra building Not-continued
I have relocated with "Vrou, kind, hond en 'n wavrag aardse besittings" to Secunda during December. There was no house available with a 6x6m workshop/store room like I used to have in Vaalpark, so I still have to find holes for all my hobby equipment. In this process I found a few things which was gone for the past few years and I got rid of a few things which was never used.
Secunda is about 170km from Johannesburg and 150km from Pretoria on the way to Volksrust. It is mainly the Sasol petrochemical factory that provide income in this area with the Billions of $$$'s projects going on. It is a typical "kokolol" town, but very hobby friendly. The model RC car and airplane clubs is very active and both have excellent facilities. The weather is not that friendly towards thermal gliding as it is situated on the Highveld RIDGE. Wind is blowing most of the time and for some reason we have 4 seasons on a normal day.
I have joined the local TRMC club (TEKS Radio Model Club [TEKS = Trichardt, Evander, Kinross & Secunda the 4 towns in this area). This is mainly a power flying club, but there is some interest in glider thermal flying and slope flying. The club have a beautiful facility close to town with tar runway, clubhouse etc. I am in the process to locate a separate field for gliding. We will be flying the postals.
During this period I did not do nothing, as I built a Fokker DVII foamy with Depron and a Slope wing in order to have some social stick time and acquired a Jazz F5B model (see reference to wind above).
I am now about to continue again with the Supra building. I have finished the Rudder and Elevator and the Center section of wing. The plug for the fuz mold is with Mark Stockton where I think it got less priority at the moment due to Tabooish DLG production. The tips should be easy and I will take you through the process of alignment once I get started again soon.
Cheers
Gert
Secunda is about 170km from Johannesburg and 150km from Pretoria on the way to Volksrust. It is mainly the Sasol petrochemical factory that provide income in this area with the Billions of $$$'s projects going on. It is a typical "kokolol" town, but very hobby friendly. The model RC car and airplane clubs is very active and both have excellent facilities. The weather is not that friendly towards thermal gliding as it is situated on the Highveld RIDGE. Wind is blowing most of the time and for some reason we have 4 seasons on a normal day.
I have joined the local TRMC club (TEKS Radio Model Club [TEKS = Trichardt, Evander, Kinross & Secunda the 4 towns in this area). This is mainly a power flying club, but there is some interest in glider thermal flying and slope flying. The club have a beautiful facility close to town with tar runway, clubhouse etc. I am in the process to locate a separate field for gliding. We will be flying the postals.
During this period I did not do nothing, as I built a Fokker DVII foamy with Depron and a Slope wing in order to have some social stick time and acquired a Jazz F5B model (see reference to wind above).
I am now about to continue again with the Supra building. I have finished the Rudder and Elevator and the Center section of wing. The plug for the fuz mold is with Mark Stockton where I think it got less priority at the moment due to Tabooish DLG production. The tips should be easy and I will take you through the process of alignment once I get started again soon.
Cheers
Gert
Rudder and Elevator
It is always wise to test your procedures and tools for vacuum bagging on a smaller piece like the Rudder. The booboo will be less painful that way and provides for a learning curve. I have sanded the Rudder and Elevator cores to shape as the CNC cutter can not do the rounded tips. The Elevator get an easy spar system. My first Supra had only unidirectional carbon on top and bottom for spar. The #2 get a carbon rod top and bottom. Both systems would work fine. A small block of balsa is layed in for the hold-on bolt and a balsa flange to fit the V-platform is added. The Rudder do not get a spar. A final finish with the sanding block and it is ready for the vacuum bag.
There is lots of info on the net for vacuum bagging and this is really not difficult to get under the belt with spectacular results. First the "mylars " is cut to size. I use clear PVC which I can get locally. I spray paint the mylars with colours I want the wings to appear, dark colour on bottom of elevator and white on top. Make sure you have cleaned the mylars before painting otherwise you will have some marks on the final finish. I used Plascon spray cans this time. Do not use the metallic colours as for some reason the result is awfull. It looks like the silver and colour seperates, I can show you an example in my booboo box.
I have some 60g Kevlar available and will use this on #2, 86g fiber glass will also work here. Cut the material to fit (yea right I said cut and not chew). I bought a cheap cissors and grinded the cutting edge square. This works well for cutting the kevlar. Kevlar is difficult to finish around the LE after bagging as it can not be sanded without going fuzzy. I use a piece of glass on the LE and make sure the Kevlar only starts a few millimeters in from the LE. A tow of Carbon can also be used under the fiber glass to make the LE harder. These additional pieces are fixed to the foam cores with a light mist of spray glue. All the pieces are cut at a 45 degree angle with the weave of the material.
Now starts the fun part. Get your vacuum pump ready and test it still works without tripping your main powers switch. I bought a fridge compressor at an electrical spares shop a few years ago. It is connected to a reservoir made from 150mm PVC pipe. The reservoir is fixed below my work bench out of the way. The fridge compressor have a built-in one way valve feature. I have a vacuum switch on the reservoir to switch compressor on and off and regulate the vacuum around 10 inch Hg. Pretty simple setup but effective. Lay the plastic bag and breather fabric out and get it ready to accept the wings. I normally lay everything out on tables with all tools and clean up paper towels etc. and do a dry run to make sure all will be fine. I used Epolam 2020 resin system on advice from Mark and Craig this time. Roll the resin on the kevlar which is laying on the painted side of the mylars. I use the roller to squash the kevlar strands and push the resin thoroughly through the Material. When all is wet use a layer of paper towels and roll with hard roller to remove excess of resin. The resin do not give strength but only add to the weight so this is the place where you build a light model.
Well carefully place the bottom mylar in the bag ( I open my bags 3 sides). Add the foam core on top alligned with kevlar on LE and add the top mylar with skin. Add breather cloth and seal bag. Pull the vacuum and check that most wrinkles is out of bag and things look straight. At this point you can still make adjustments. Weigh the cores down in the foam beds to make sure it comes out straight.
Twelve to 24 hours later you can open the bag and look at the results.
Photos to follow........
There is lots of info on the net for vacuum bagging and this is really not difficult to get under the belt with spectacular results. First the "mylars " is cut to size. I use clear PVC which I can get locally. I spray paint the mylars with colours I want the wings to appear, dark colour on bottom of elevator and white on top. Make sure you have cleaned the mylars before painting otherwise you will have some marks on the final finish. I used Plascon spray cans this time. Do not use the metallic colours as for some reason the result is awfull. It looks like the silver and colour seperates, I can show you an example in my booboo box.
I have some 60g Kevlar available and will use this on #2, 86g fiber glass will also work here. Cut the material to fit (yea right I said cut and not chew). I bought a cheap cissors and grinded the cutting edge square. This works well for cutting the kevlar. Kevlar is difficult to finish around the LE after bagging as it can not be sanded without going fuzzy. I use a piece of glass on the LE and make sure the Kevlar only starts a few millimeters in from the LE. A tow of Carbon can also be used under the fiber glass to make the LE harder. These additional pieces are fixed to the foam cores with a light mist of spray glue. All the pieces are cut at a 45 degree angle with the weave of the material.
Now starts the fun part. Get your vacuum pump ready and test it still works without tripping your main powers switch. I bought a fridge compressor at an electrical spares shop a few years ago. It is connected to a reservoir made from 150mm PVC pipe. The reservoir is fixed below my work bench out of the way. The fridge compressor have a built-in one way valve feature. I have a vacuum switch on the reservoir to switch compressor on and off and regulate the vacuum around 10 inch Hg. Pretty simple setup but effective. Lay the plastic bag and breather fabric out and get it ready to accept the wings. I normally lay everything out on tables with all tools and clean up paper towels etc. and do a dry run to make sure all will be fine. I used Epolam 2020 resin system on advice from Mark and Craig this time. Roll the resin on the kevlar which is laying on the painted side of the mylars. I use the roller to squash the kevlar strands and push the resin thoroughly through the Material. When all is wet use a layer of paper towels and roll with hard roller to remove excess of resin. The resin do not give strength but only add to the weight so this is the place where you build a light model.
Well carefully place the bottom mylar in the bag ( I open my bags 3 sides). Add the foam core on top alligned with kevlar on LE and add the top mylar with skin. Add breather cloth and seal bag. Pull the vacuum and check that most wrinkles is out of bag and things look straight. At this point you can still make adjustments. Weigh the cores down in the foam beds to make sure it comes out straight.
Twelve to 24 hours later you can open the bag and look at the results.
Photos to follow........
Core Prep
Ok I survived the Nats and all of my model as well, so there is no restoration work and I can make time to continue with the Supra wing before I move house in December. As you can see I spend time when available and it often happens that my workshop do not see me for days or weeks. I am lucky to have a family as well so priority is not always Supra only.
If your eyeball technique of sizing the spar worked then the wing cores will fit with the spar a little smaller in height than the beds. The first thing to do is to cut the channel for servo wiring in aft part of cores. I made a simple tool for my "Dremel" type tool so it can operate like a small router. It is made of a small piece of flat bar aluminum with appropriate holes at right places and screws onto the tool, look at the picture. Keep the slot size small as it may create a dent in the wing under vacuum. Test fit the cores and mark and cut, cut-outs for bolt beam. Glue the foam cores to the spar. Be careful with glue as you do not want the glue to seep trough to the other end and make a bulge and you do not want the glue to fill the slot for wiring harness. I like to keep the bottom of spar flush with the bottom of the cores with a small gap on the top. Usually I would first place a piece of packing tape on the foam core beds for incase the glue would run through. I have tried many types of glue for this process and had many booboo's. You do not need high strength here and obviously keep the weight low. Spray glue may work the best here.
The gap on top of the spar can be filled with a thin, soft piece of balsa. Glue it on with microbaloons and epoxy resin mix and sand smooth with contour of wing airfoil. I protect the foam with masking tape on the sides of the spar and sand until the masking tape starts to deteriorate. All the other dings that the foam have picked up in the mean time, by dropping tools and cyno etc can be covered with pre-mix fine crack filler (Pollyfilla type). Remember where you sand on the foam cores you will damage the profile so keep it to a minimum and approach with caution. It is at this point where you decide if you want a pretty model or a light competition glider. Once the top is finished turn the wing over and do the bottom. Use the foam blanks for the wing to rest in (Aah now you know why I cut the dihedral in the foam blanks). Fill the gaps below the bolt beam with soft balsa. I have added some end ribs made from hard balsa and shaped to airfoil. From the Genie construction manual I learned to add a fake foam rib about 10-20mm on the ends. This helps to keep the Mylar straight over the end ribs. Afterwards the fake foam ribs is cut off and it leaves a nice finish with the end ribs.
Next up is the flap/ailerons cut out. I do the flaps in this part of the process and this is described by Mark Drela's plans so I will not say more. Mark Stockton gave me the tip to cover the entire flap with one piece of material from top to bottom wrapped around the flap LE to form a C. This makes the flap more rigid and is maybe easier to do that the separate doublers pieces for reinforcement.
As you can see once the spar is ready the rest of the work is easy. The same procedure is followed to do the tips, but I will get to that later…
Next up is the vacuum bagging…. Ahh lekker!
Cheers
Gert
If your eyeball technique of sizing the spar worked then the wing cores will fit with the spar a little smaller in height than the beds. The first thing to do is to cut the channel for servo wiring in aft part of cores. I made a simple tool for my "Dremel" type tool so it can operate like a small router. It is made of a small piece of flat bar aluminum with appropriate holes at right places and screws onto the tool, look at the picture. Keep the slot size small as it may create a dent in the wing under vacuum. Test fit the cores and mark and cut, cut-outs for bolt beam. Glue the foam cores to the spar. Be careful with glue as you do not want the glue to seep trough to the other end and make a bulge and you do not want the glue to fill the slot for wiring harness. I like to keep the bottom of spar flush with the bottom of the cores with a small gap on the top. Usually I would first place a piece of packing tape on the foam core beds for incase the glue would run through. I have tried many types of glue for this process and had many booboo's. You do not need high strength here and obviously keep the weight low. Spray glue may work the best here.
The gap on top of the spar can be filled with a thin, soft piece of balsa. Glue it on with microbaloons and epoxy resin mix and sand smooth with contour of wing airfoil. I protect the foam with masking tape on the sides of the spar and sand until the masking tape starts to deteriorate. All the other dings that the foam have picked up in the mean time, by dropping tools and cyno etc can be covered with pre-mix fine crack filler (Pollyfilla type). Remember where you sand on the foam cores you will damage the profile so keep it to a minimum and approach with caution. It is at this point where you decide if you want a pretty model or a light competition glider. Once the top is finished turn the wing over and do the bottom. Use the foam blanks for the wing to rest in (Aah now you know why I cut the dihedral in the foam blanks). Fill the gaps below the bolt beam with soft balsa. I have added some end ribs made from hard balsa and shaped to airfoil. From the Genie construction manual I learned to add a fake foam rib about 10-20mm on the ends. This helps to keep the Mylar straight over the end ribs. Afterwards the fake foam ribs is cut off and it leaves a nice finish with the end ribs.
Next up is the flap/ailerons cut out. I do the flaps in this part of the process and this is described by Mark Drela's plans so I will not say more. Mark Stockton gave me the tip to cover the entire flap with one piece of material from top to bottom wrapped around the flap LE to form a C. This makes the flap more rigid and is maybe easier to do that the separate doublers pieces for reinforcement.
As you can see once the spar is ready the rest of the work is easy. The same procedure is followed to do the tips, but I will get to that later…
Next up is the vacuum bagging…. Ahh lekker!
Cheers
Gert
The Spar
The Wing Spar
Once the spar caps is cleaned with sanding paper the rest of the spar can be done. Cornelius cut the foam cores from Isoboard for me with his CNC cutter. The center panel consists of two parts with a dihedral break in the middle of 2.5 degrees each side according to the plan. To do the construction for this is most difficult as the center panel is 1.6m long. The way I do this is to cut the foam cores with the dihedral in the foam beds. Due to the thickness of the foam we had only 1.5 degrees was possible. This will effect the EDA slightly, (4.9 degrees i.s.o. 5.9 degrees) , but from my first Supra I found that it works fine. You line up the foam core beds on a work bench and glue with spray glue to the bench. Now this can be used for all the preparation work on the foam cores and spar and can also serve as the beds for the wing when vacuum bag is done. It is important to get this very accurate as this will determine if your wing comes out "straigh" or like a propellor. So spend some time to measure it out and adjust according to the plans. I cover the TE with a piece of masking tape for protection during the building process, and yes remeber that cyno eats the foam so be careful when you spill some on your perfectly cut cores! (more filling and sanding to do for me)
Next step is to measure the spar in the wing cores and cut the gaps in the cores for the spar with your foam cutter, wire running against a guide on the ends. Place the pieces of foam cut out for the spar, in the spar jig (see previous articles) and adjust the sides of the jig until it is flush with the foam. Take the foam out. I place a spacer from some 1.5mm thick plastic in the bottom of the spar jig, then put both the spar caps on top of each other in the jig. Now it is easy to make the web from "endgrain" balsa. Take some 12mm and 8mm planks or what ever you will be using as the web and place head on in the jig. Mark wood and cut useing a mitre box. It is not nessesary to do this accurate and the balsa should be slightly oversized and stick out above the jig.Once all pieces is more or less in, glue the balsa to the bottom spar cap in the jig. Once this is done and you have not glued the whole lot to your jig, then take a sanding block and sand the balsa down to be flush with the jig sides (an electric aparatus helps to save time and sweat here). Take the lot out and test fit on core beds and make sure that once the spar is finished (including a layer of glass) that it will fit in the wing cores [now you see why I use the jig]. It can rather be a bit smaller than sticking out which will cause a bump in the wing profile. I do not use balsa all the way for the web. Part of my web is made of foam, and yes my wing bends on a full pedal zoom. The wing joiners is made fit and glued in between the spar caps. A good bond is required here. Glue the top spar cap to the web while on the core beds with lots of weights in order to make sure the spar fits to the dehedral angle. I use laminating resin mixed with carbosil to glue the spar caps to the web. Next the spar is covered with a glass sock (I did not have a carbon sock which will be better here). The spar can be wraped with 2 layers of glass cut at a 45 degree as per the original plan instead of the sock. I make my bolt beam , the beam used to bolt the wing to the fuz, with 2 layes of plywood sanwitched between two layers of Unidirectional carbon tape. This bolt beam is installed in the spar and some kevlar is wrapped around the spar at the center and ends.
I do not go into all the details as the plans from Mark Drela indicate most of the information. When I can not source the same material I would take my own initiative. My intention is more to show one way of how these plans can become reality.
Safety tip: By a box of surgical gloves and masks at the pharmacy and use when you sand the carbon bits. The carbon dust will never come out of your lungs and system if inhaled.
Next time the wing core preparation......... I hope I can keep up with my building for a piece every month in SE.
Cheers
Gert
PS The photo of spar example is from another project which I do in parallel but is only to demonstrate the spar caps and web with "endgrain" balsa.
Once the spar caps is cleaned with sanding paper the rest of the spar can be done. Cornelius cut the foam cores from Isoboard for me with his CNC cutter. The center panel consists of two parts with a dihedral break in the middle of 2.5 degrees each side according to the plan. To do the construction for this is most difficult as the center panel is 1.6m long. The way I do this is to cut the foam cores with the dihedral in the foam beds. Due to the thickness of the foam we had only 1.5 degrees was possible. This will effect the EDA slightly, (4.9 degrees i.s.o. 5.9 degrees) , but from my first Supra I found that it works fine. You line up the foam core beds on a work bench and glue with spray glue to the bench. Now this can be used for all the preparation work on the foam cores and spar and can also serve as the beds for the wing when vacuum bag is done. It is important to get this very accurate as this will determine if your wing comes out "straigh" or like a propellor. So spend some time to measure it out and adjust according to the plans. I cover the TE with a piece of masking tape for protection during the building process, and yes remeber that cyno eats the foam so be careful when you spill some on your perfectly cut cores! (more filling and sanding to do for me)
Next step is to measure the spar in the wing cores and cut the gaps in the cores for the spar with your foam cutter, wire running against a guide on the ends. Place the pieces of foam cut out for the spar, in the spar jig (see previous articles) and adjust the sides of the jig until it is flush with the foam. Take the foam out. I place a spacer from some 1.5mm thick plastic in the bottom of the spar jig, then put both the spar caps on top of each other in the jig. Now it is easy to make the web from "endgrain" balsa. Take some 12mm and 8mm planks or what ever you will be using as the web and place head on in the jig. Mark wood and cut useing a mitre box. It is not nessesary to do this accurate and the balsa should be slightly oversized and stick out above the jig.Once all pieces is more or less in, glue the balsa to the bottom spar cap in the jig. Once this is done and you have not glued the whole lot to your jig, then take a sanding block and sand the balsa down to be flush with the jig sides (an electric aparatus helps to save time and sweat here). Take the lot out and test fit on core beds and make sure that once the spar is finished (including a layer of glass) that it will fit in the wing cores [now you see why I use the jig]. It can rather be a bit smaller than sticking out which will cause a bump in the wing profile. I do not use balsa all the way for the web. Part of my web is made of foam, and yes my wing bends on a full pedal zoom. The wing joiners is made fit and glued in between the spar caps. A good bond is required here. Glue the top spar cap to the web while on the core beds with lots of weights in order to make sure the spar fits to the dehedral angle. I use laminating resin mixed with carbosil to glue the spar caps to the web. Next the spar is covered with a glass sock (I did not have a carbon sock which will be better here). The spar can be wraped with 2 layers of glass cut at a 45 degree as per the original plan instead of the sock. I make my bolt beam , the beam used to bolt the wing to the fuz, with 2 layes of plywood sanwitched between two layers of Unidirectional carbon tape. This bolt beam is installed in the spar and some kevlar is wrapped around the spar at the center and ends.
I do not go into all the details as the plans from Mark Drela indicate most of the information. When I can not source the same material I would take my own initiative. My intention is more to show one way of how these plans can become reality.
Safety tip: By a box of surgical gloves and masks at the pharmacy and use when you sand the carbon bits. The carbon dust will never come out of your lungs and system if inhaled.
Next time the wing core preparation......... I hope I can keep up with my building for a piece every month in SE.
Cheers
Gert
PS The photo of spar example is from another project which I do in parallel but is only to demonstrate the spar caps and web with "endgrain" balsa.
Supra #3
Spar caps
The wing spar will consists of a web in the centre made of balsa and foam with carbon fibre runners called the "spar caps" and the whole lot is then covered with fibre glass whith strands running 45 degrees. The spar caps is used on the top and bottom of the wing spar to provide the pull and compression strength for the wing spar system. Taking into account the length of the wing and thickness this is one of the critical areas for failure. I have found in the past if the total spar weight can be kept low then the wing total weight will be low. This will also determine what type of launch you can achieve before failure, a fine balance!. The original plan call for prefabricated taper carbon fiber stock. This however is very expensive if you have to import. I use Uni-Directional Carbon Fiber tape and make my own roughly tapered. Obviously I compromise by doing so and it may be not of a similar uniform strength and weight, but hey! I am building a toy plane on a limited budget. See photo of the type of carbon I used this time. Now, I am not a structural engineer, so I use "What Looks Right" rules and previous experience (not a lot) to determine how much carbon is enough and how much I put in, is my secret, so do not ask.
In previous attempts I found it difficult to keep the tows straight when I vacuum the spar caps. The reason for vacuum curing is to force most of the unnecessary resin out. I made a jig from aluminum square tubing and flat bar. Take about 1h for center section (1.8m long) and one for the tips. I cover the surfaces exposed to resin with packing tape. See photo to get the idea. This jig is also used later on to get the spar accurately on correct size in a short time. I wet out the carbon and put it in the jig with a piece of foam on top and in the bag. Takes 15 minutes , next day you remove and put in the next one. 6 days later you have 6 spar caps , Top and bottom for centre section and top and bottom for each wing tip.
Wing Joiners
The wing joiners are used to plug the 2 tip panel in to the centre panel. Due to the fact that the Supra have the joint from Centre panel to the tips way down along the lenght of the wing, the joiners can be sized small as it will see less stress than if it were a centre wing joiner at the fuz. I use 3/8" carbon rods. If you can not get any locally, you can make your own from carbon tow. For the tubes I use brass tubes which fit tight over the rods. If you want to save a few grams you can make the tubes from Kevlar. Taking the easy route as always here is my method to create a joiner for the 5 degree dihedral. Print the plan for the "bend" available from the Supra plans and paste it to you working surface. Put a piece of clear plastic on top of it. Take two pieces of alluminium angle and bend in the middle to conform to the 5 degree bend on the plan. Screw the pieces of angle to the work bench on top of the plan. Use some clay to build a dam inside the anguled channel. Place your brass tube inside the channel (remember to plug the ends!). Mix some resin with carbosil and pour into the channel. Wait till next day and remove angles. The piece can now be sanded to fit between the spar caps and cut in 2 pieces, one for centre panel and one for tip panel side. Obviously you need to do this twice. Takes about 30 minutes on two days.
Building a few composite parts
You need a few carbon parts to complete your model. All these parts is made easily with simple molds. First up is the Elevator V - mount an platform. There is a few variations on this but I found my version to work just as well. See photo of molds/formers I used for the V-mount and elevator platform. Simple but effective. I simplified the platform a bit and on previous Bubble Dancer and Supra it worked perfectly and is more than strong enough. The weakest point is the thread of elevator hold on bolt. I use a small piece of kevlar now inside the fin around the bolt thread to try improve. I have read that the guys install a blind nut on the molded version. With left over carbon and resin I make a flat piece to be used later for the rudder horn. The parts come out very light and strong.
Tools
The tools you need up to this point is: Normal workshop hand tools including a pair of cissors to cut the material, clamps, packing tape and foam to make molds and a fridge compressor to do the vacuum compression.
A picture say a thousand words, so I have more photos , let me know if you need more.
Next is the wing ………..to be continued.
Cheers
Gert
PS I hope I can finish this before I have to pack up my workshop for the move to Secunda.
The wing spar will consists of a web in the centre made of balsa and foam with carbon fibre runners called the "spar caps" and the whole lot is then covered with fibre glass whith strands running 45 degrees. The spar caps is used on the top and bottom of the wing spar to provide the pull and compression strength for the wing spar system. Taking into account the length of the wing and thickness this is one of the critical areas for failure. I have found in the past if the total spar weight can be kept low then the wing total weight will be low. This will also determine what type of launch you can achieve before failure, a fine balance!. The original plan call for prefabricated taper carbon fiber stock. This however is very expensive if you have to import. I use Uni-Directional Carbon Fiber tape and make my own roughly tapered. Obviously I compromise by doing so and it may be not of a similar uniform strength and weight, but hey! I am building a toy plane on a limited budget. See photo of the type of carbon I used this time. Now, I am not a structural engineer, so I use "What Looks Right" rules and previous experience (not a lot) to determine how much carbon is enough and how much I put in, is my secret, so do not ask.
In previous attempts I found it difficult to keep the tows straight when I vacuum the spar caps. The reason for vacuum curing is to force most of the unnecessary resin out. I made a jig from aluminum square tubing and flat bar. Take about 1h for center section (1.8m long) and one for the tips. I cover the surfaces exposed to resin with packing tape. See photo to get the idea. This jig is also used later on to get the spar accurately on correct size in a short time. I wet out the carbon and put it in the jig with a piece of foam on top and in the bag. Takes 15 minutes , next day you remove and put in the next one. 6 days later you have 6 spar caps , Top and bottom for centre section and top and bottom for each wing tip.
Wing Joiners
The wing joiners are used to plug the 2 tip panel in to the centre panel. Due to the fact that the Supra have the joint from Centre panel to the tips way down along the lenght of the wing, the joiners can be sized small as it will see less stress than if it were a centre wing joiner at the fuz. I use 3/8" carbon rods. If you can not get any locally, you can make your own from carbon tow. For the tubes I use brass tubes which fit tight over the rods. If you want to save a few grams you can make the tubes from Kevlar. Taking the easy route as always here is my method to create a joiner for the 5 degree dihedral. Print the plan for the "bend" available from the Supra plans and paste it to you working surface. Put a piece of clear plastic on top of it. Take two pieces of alluminium angle and bend in the middle to conform to the 5 degree bend on the plan. Screw the pieces of angle to the work bench on top of the plan. Use some clay to build a dam inside the anguled channel. Place your brass tube inside the channel (remember to plug the ends!). Mix some resin with carbosil and pour into the channel. Wait till next day and remove angles. The piece can now be sanded to fit between the spar caps and cut in 2 pieces, one for centre panel and one for tip panel side. Obviously you need to do this twice. Takes about 30 minutes on two days.
Building a few composite parts
You need a few carbon parts to complete your model. All these parts is made easily with simple molds. First up is the Elevator V - mount an platform. There is a few variations on this but I found my version to work just as well. See photo of molds/formers I used for the V-mount and elevator platform. Simple but effective. I simplified the platform a bit and on previous Bubble Dancer and Supra it worked perfectly and is more than strong enough. The weakest point is the thread of elevator hold on bolt. I use a small piece of kevlar now inside the fin around the bolt thread to try improve. I have read that the guys install a blind nut on the molded version. With left over carbon and resin I make a flat piece to be used later for the rudder horn. The parts come out very light and strong.
Tools
The tools you need up to this point is: Normal workshop hand tools including a pair of cissors to cut the material, clamps, packing tape and foam to make molds and a fridge compressor to do the vacuum compression.
A picture say a thousand words, so I have more photos , let me know if you need more.
Next is the wing ………..to be continued.
Cheers
Gert
PS I hope I can finish this before I have to pack up my workshop for the move to Secunda.
Supra building #2
The Supra have a pod and boom design for fuselage. The carbon boom help to keep the total weight to a minimum and with sufficient strength for the application. Booms are available from Polecatearo.com for around R300 landed cost. The pod design of Mark Drela is optimised for F3J gliders but can be used for many other purposes. You may even use this for a RES model and by changing the layup materials you have a means to control the strength and weight for your application.
I am no expert and document as I learn for my own future use. There are many ways to achieve the same or better results and I will be glad to hear of the other ways.
Ok to do the pod you first find a pensioner in Potchefstroom with a lathe. Some Yellowtong wood and instructions to the oldtoppie who is complaining heavily, only used to do coffee table legs, and a week later you go for inspection. To make things even more interesting I want the pod to consist of two pieces split in the middle, length wise. Any way it came out close to the original plan. With some wood filler you cover most of the grain and holes in the round plug. Add the pylon and file it nice round to blend in with the fuz. Sand the plug as smooth as you can. Cover with varnish to seal the wood. Spray paint it with epoxy paint. By now it should be fairly smooth if you do some fine sanding (600 grit paper) but there will still be some imperfections and wood grain showing only slightly. Now for the final step to sand and buff the thing for a week until it shines like a mirror. Yeah right! That’s why lazy people become engineers. The other way is you pour Pratliglo over the lot and control the temperature to let if flow over the pod and cover it with a smooth glass like layer. It removes any of the grain and last of the imperfections. If this is cured hard you can even sand places which had some imperfections and add more Pratliglow or sand and polish it with burnishing compound. Some waxing and there you have it shining like a mirror and smooth!
Split the two halves and you are ready to make a mold with any of the many procedures that are available.
Till next time when I do the Spar Caps.
Cheers
Gert
I am no expert and document as I learn for my own future use. There are many ways to achieve the same or better results and I will be glad to hear of the other ways.
Ok to do the pod you first find a pensioner in Potchefstroom with a lathe. Some Yellowtong wood and instructions to the oldtoppie who is complaining heavily, only used to do coffee table legs, and a week later you go for inspection. To make things even more interesting I want the pod to consist of two pieces split in the middle, length wise. Any way it came out close to the original plan. With some wood filler you cover most of the grain and holes in the round plug. Add the pylon and file it nice round to blend in with the fuz. Sand the plug as smooth as you can. Cover with varnish to seal the wood. Spray paint it with epoxy paint. By now it should be fairly smooth if you do some fine sanding (600 grit paper) but there will still be some imperfections and wood grain showing only slightly. Now for the final step to sand and buff the thing for a week until it shines like a mirror. Yeah right! That’s why lazy people become engineers. The other way is you pour Pratliglo over the lot and control the temperature to let if flow over the pod and cover it with a smooth glass like layer. It removes any of the grain and last of the imperfections. If this is cured hard you can even sand places which had some imperfections and add more Pratliglow or sand and polish it with burnishing compound. Some waxing and there you have it shining like a mirror and smooth!
Split the two halves and you are ready to make a mold with any of the many procedures that are available.
Till next time when I do the Spar Caps.
Cheers
Gert
Supra Building #1 (material list)
Ok here we start.
The plans are at: http://www.charlesriverrc.org/articles/supra/supra.htm
A building thread with many ideas and photo ilustrations are at: http://www.rcgroups.com/forums/showthread.php?t=437733
Material list with options available locally:
Foam Cores: Cornelius du Plessis for Isoboard CNC cut cores [Cordup@telkomsa.net]
Fuz mold and plug: I am busy with a plug according to the Drela F3J plan, will be ready by mid Aug.
Composites: Talk to AMT
Wing Spar:
Carbon UD 2LM x 600 wide. See what is available. Even carbon tow can be used, it is just more work.
Glass sock 3m x (35mm dia)? Light stuff Should fit over spar.
Or Carbon sock (heavier but stronger)
Or rap with 2 layers 49g glass (from off-cuts)
10mm Balsa x 1 sheet (will be cut for endgrain spar in sections)
Wing Skins: (see layout diagram) <<...>>
Option 1 (glass)
Centre 1 layer 86g + 1 layer 49g and some dubble layers for centre,servo bays and flap
Tips 1 layer 86g and some dubble layers for root,servo bays and ailerons
86g = 1m x 2.7Lm , 49g = 1m x 2Lm
Option 2 (kevlar)
61g with some double layers for root,servo bays and ailerons 1m wide by 2.7Lm long
(I find that this come out quite soft with Isoboard and dents easily, and would personally use CF doublers iso. Kevlar)
Otion 3 (Carbon)
90g with some double layers for root,servo bays and ailerons 1m wide by 2.7Lm long
(Obiously many derivatives in between can be done)
You would need some extra pieces 2" wide 45deg cut of glass for the LE and root ribs and flap/aileron facing.
I used peel ply previously for the live hinge, but kevlar is better.
The joiners is 3/8" carbon rods and I used brass tubes. You can make this from 2 thin wall Alu tubes which fit tight and pull carbon tow in the smaller one to make a rod.
Rudder and Elevator
Will fit in with wing material but need 1m x 0.75LM
Fuz pod
Off cuts of about 1m x 1.5m of kevlar or glass or combinations. Add some/or lots of carbon on strategic places.
Boom
www.Polecataero.com R300
V mount and elevator platform
2m Carbon tow
Small pieces of 86g glass
Small pieces of 90-200g Carbon or UD can also work
Other
LR20 Laminating Resin 1kg & LH281 Hardner worked fine for me
Carbosill
Mylar (I use clear PVC from Mayzies)
Paint (I use Duco in cans)
The plans are at: http://www.charlesriverrc.org/articles/supra/supra.htm
A building thread with many ideas and photo ilustrations are at: http://www.rcgroups.com/forums/showthread.php?t=437733
Material list with options available locally:
Foam Cores: Cornelius du Plessis for Isoboard CNC cut cores [Cordup@telkomsa.net]
Fuz mold and plug: I am busy with a plug according to the Drela F3J plan, will be ready by mid Aug.
Composites: Talk to AMT
Wing Spar:
Carbon UD 2LM x 600 wide. See what is available. Even carbon tow can be used, it is just more work.
Glass sock 3m x (35mm dia)? Light stuff Should fit over spar.
Or Carbon sock (heavier but stronger)
Or rap with 2 layers 49g glass (from off-cuts)
10mm Balsa x 1 sheet (will be cut for endgrain spar in sections)
Wing Skins: (see layout diagram) <<...>>
Option 1 (glass)
Centre 1 layer 86g + 1 layer 49g and some dubble layers for centre,servo bays and flap
Tips 1 layer 86g and some dubble layers for root,servo bays and ailerons
86g = 1m x 2.7Lm , 49g = 1m x 2Lm
Option 2 (kevlar)
61g with some double layers for root,servo bays and ailerons 1m wide by 2.7Lm long
(I find that this come out quite soft with Isoboard and dents easily, and would personally use CF doublers iso. Kevlar)
Otion 3 (Carbon)
90g with some double layers for root,servo bays and ailerons 1m wide by 2.7Lm long
(Obiously many derivatives in between can be done)
You would need some extra pieces 2" wide 45deg cut of glass for the LE and root ribs and flap/aileron facing.
I used peel ply previously for the live hinge, but kevlar is better.
The joiners is 3/8" carbon rods and I used brass tubes. You can make this from 2 thin wall Alu tubes which fit tight and pull carbon tow in the smaller one to make a rod.
Rudder and Elevator
Will fit in with wing material but need 1m x 0.75LM
Fuz pod
Off cuts of about 1m x 1.5m of kevlar or glass or combinations. Add some/or lots of carbon on strategic places.
Boom
www.Polecataero.com R300
V mount and elevator platform
2m Carbon tow
Small pieces of 86g glass
Small pieces of 90-200g Carbon or UD can also work
Other
LR20 Laminating Resin 1kg & LH281 Hardner worked fine for me
Carbosill
Mylar (I use clear PVC from Mayzies)
Paint (I use Duco in cans)
Supra Scratch build series
I always wanted to fly a full house glider. You see, here in upcountry you must keep up with the neighbors flashy "glass slippers". The cost of these "babies" however made my wife think twice, taking into account the unknown expire date of these models with my flying skills. I have been following the evolvement of the Supra design after building my Bubble Dancer from the same designer Dr Mark Drela of MIT and AG airfoil fame. Mark designed the Allegro and Allegro Light 2m gliders and followed that up with the 3m Bubble Dancer. I am not sure what was first but in the same time the SuperGee DLG glider was designed by him and many of the lessons learned in the DLG was carried to the designs that followed and hence the "big" gliders that looks like overgrown chukies. Mark designed a 2m full house glider and called it the Aegea. He was requested by club mates to stretch this wing to 3.2m for the Manis which was very successful in USA TD competitions. The Mantis design ideas originated in a car traveling back from a seminar by Dr Selig which Tom Kiesling attended. Anyway the 3.2m Aegea wing together with a "Pretty Mantis" fuselage was used by a few scratch builders. One of the ideas from the Dr Selig talk was to mount the wing on a pylon. It was found during launches with the 3.2m Aegea wing that due to the spar not being straight that wing would twist and cause washout and hence launched not optimal.
Mark was approached by Tom Kiesling (member of USA F3J team) to design a glider for F3J use and so followed the 3.4m Supra in 2004. The Supra wing was basically a Aegea wing with straightened spar and a redesigned pod and boom fuselarge. Tom built two foam bagged wing models for the F3J WC in 2004 and flew it there. The pilots attending the competion all relished that this "scratch built" glider had a L/D superior to the rest of the field although Tom did not make the fly-offs. He did however win all the USA competions to follow for the next 2 years running up to this years WC.
Comments from Mark Drela on the design:
Following the SuperGee philosophy, the fuselage pod is minimal, and the wing is on a pylon mount. I think it works, because the glider is amazingly quiet in a fast flyby.
The Supra's EDA of 6 degrees is typical on DLGs, but is quite large for this type of glider. The idea was to give it approximately neutral spiral stability at moderate glide speeds. This makes it extremely easy to fly precise thermal circles with little pilot workload. Once a moderate-bank circle was established, and I fed in the usual up-elevator trim, I could take my hands off the TX for almost a minute with the glider holding the circle nicely. Like with a DLG, using mainly the rudder for thermal circle adjustments works very well. It remains to be seen whether the large dihedral impairs landing precision in gusts.
I also tried hard to get the extremities light. I tapered the tip spars in width and used 1.0 oz Kevlar on the tails and wingtips.
Not only did Mark design the glider in theory but he gave thought to the construction and structural design with exact details of how to achieve the desired strength and weight and the best is, all this information is available for free.
The plans and information can be found here: http://www.charlesriverrc.org/articles/supra/supra.htm
In the mean time a molded version become available (See ads from Cape Sailplanes) but as one of the guys said : "Liewe ouers!" it is expensive.
Now why would you want to build anything else than this glider? So I built my first Supra but used the Pretty Mantis fuz. I did not keep to the original design regarding materials and weight as I was still learning and wanted to build a strong glider which I can use for learning to fly in competitions. My first attemp came out 2.1kg in stead of 1.5kg. It do fly fantastic and is very easy to launch and land.
I have started with my second Supra which I will document for SE to "let the sun shine on all". Most of the parts I make from simple forms and molds and local available materials. I have made a new plug for the fuz according to the Drela F3J plan. The only item I have imported is the boom.
When I use to run the Comrades marathon there was a saying : "get to the start line"
To be continued..........
Cheers
Gert
Mark was approached by Tom Kiesling (member of USA F3J team) to design a glider for F3J use and so followed the 3.4m Supra in 2004. The Supra wing was basically a Aegea wing with straightened spar and a redesigned pod and boom fuselarge. Tom built two foam bagged wing models for the F3J WC in 2004 and flew it there. The pilots attending the competion all relished that this "scratch built" glider had a L/D superior to the rest of the field although Tom did not make the fly-offs. He did however win all the USA competions to follow for the next 2 years running up to this years WC.
Comments from Mark Drela on the design:
Following the SuperGee philosophy, the fuselage pod is minimal, and the wing is on a pylon mount. I think it works, because the glider is amazingly quiet in a fast flyby.
The Supra's EDA of 6 degrees is typical on DLGs, but is quite large for this type of glider. The idea was to give it approximately neutral spiral stability at moderate glide speeds. This makes it extremely easy to fly precise thermal circles with little pilot workload. Once a moderate-bank circle was established, and I fed in the usual up-elevator trim, I could take my hands off the TX for almost a minute with the glider holding the circle nicely. Like with a DLG, using mainly the rudder for thermal circle adjustments works very well. It remains to be seen whether the large dihedral impairs landing precision in gusts.
I also tried hard to get the extremities light. I tapered the tip spars in width and used 1.0 oz Kevlar on the tails and wingtips.
Not only did Mark design the glider in theory but he gave thought to the construction and structural design with exact details of how to achieve the desired strength and weight and the best is, all this information is available for free.
The plans and information can be found here: http://www.charlesriverrc.org/articles/supra/supra.htm
In the mean time a molded version become available (See ads from Cape Sailplanes) but as one of the guys said : "Liewe ouers!" it is expensive.
Now why would you want to build anything else than this glider? So I built my first Supra but used the Pretty Mantis fuz. I did not keep to the original design regarding materials and weight as I was still learning and wanted to build a strong glider which I can use for learning to fly in competitions. My first attemp came out 2.1kg in stead of 1.5kg. It do fly fantastic and is very easy to launch and land.
I have started with my second Supra which I will document for SE to "let the sun shine on all". Most of the parts I make from simple forms and molds and local available materials. I have made a new plug for the fuz according to the Drela F3J plan. The only item I have imported is the boom.
When I use to run the Comrades marathon there was a saying : "get to the start line"
To be continued..........
Cheers
Gert
Introduction
Hi. My name is Gert and I fly mainly RC gliders in South Africa. I live in Sasolburg in the Freestate and work as a control system engineer for petrochemical projects. I like building my airplanes and spend a lot of time in the workshop. I have built all sorts of gliders and other airplanes over the years. Below is a few photos of the latest airplanes still in service.
I have scratch built a Supra from the Mark Drela plans and is currently busy with #2. I enjoy flying this model most of my fleet. I use it in the local TD competitions. I may add info of the local building group later to this area.
I have built a Bubble dancer. First with a builtup wing and then later upgrade with a foam and glass bagged wing. I flew this model for 2 years in the local competitions.
I also have a 2m RES glider with a Kevlar wing and a glass fuz which perform very well. This model was built light but strong for "dork" landings in competitions and have special reinforcement to handle rough abuse. It can take full pedal zooms (almost).
I use a modified Graupner Cumulus for F5J S400 competition. The motor is a S400 6V with 4.5:1 GB and 12x7.5 carbon prop. I use a 3S 1500mah Lipo battery which works well and seems the motor lasts with this setup.
I like to play with a DL50 DLG when on the beach during holidays. A really nice kit for building a DLG which was well thought out and performs well for the low cost.
I have recently completed a Minimoa scale glider of 2.8m wingspan which I must still maiden. This is my pride and joy! To be saved for special occasions.
We have no local mountains but do some slope soaring 289km from here on Tamatieberg. Except for the normal foam wings I do not have any purpose built slope gliders at the moment.
From time to time I play with electrical airplanes as well and have found the F15 parkjet lots of fun. I made a few mistakes with the paint job, but it flys very nicely and easy.
Cheers
Gert
(gnieuwoudt at telkomsa dot net)
I have scratch built a Supra from the Mark Drela plans and is currently busy with #2. I enjoy flying this model most of my fleet. I use it in the local TD competitions. I may add info of the local building group later to this area.
I have built a Bubble dancer. First with a builtup wing and then later upgrade with a foam and glass bagged wing. I flew this model for 2 years in the local competitions.
I also have a 2m RES glider with a Kevlar wing and a glass fuz which perform very well. This model was built light but strong for "dork" landings in competitions and have special reinforcement to handle rough abuse. It can take full pedal zooms (almost).
I use a modified Graupner Cumulus for F5J S400 competition. The motor is a S400 6V with 4.5:1 GB and 12x7.5 carbon prop. I use a 3S 1500mah Lipo battery which works well and seems the motor lasts with this setup.
I like to play with a DL50 DLG when on the beach during holidays. A really nice kit for building a DLG which was well thought out and performs well for the low cost.
I have recently completed a Minimoa scale glider of 2.8m wingspan which I must still maiden. This is my pride and joy! To be saved for special occasions.
We have no local mountains but do some slope soaring 289km from here on Tamatieberg. Except for the normal foam wings I do not have any purpose built slope gliders at the moment.
From time to time I play with electrical airplanes as well and have found the F15 parkjet lots of fun. I made a few mistakes with the paint job, but it flys very nicely and easy.
Cheers
Gert
(gnieuwoudt at telkomsa dot net)
