|Jan 04, 2009, 08:37 AM|
Superfly and Superflea clones KFm4 in depron
When a model is so popular it must be worth a go...Check out the superfly thread, which is thriving well ..
My first thoughts were where can I get one? and how much? ...
Then I looked at prices...and could not find them readily in the UK .. so
My second thoughts were how well can I build something very similar? and for how much?
Thats what started me off.
Designing... Shapes and sizes
I had just been using Sketchup to work out dimensions from an imported picture
So I used a top view of a superfly.bmp picture to measure the dimensions...It was pulled from the superfly instructions and was used as an image in the sketchup program
Use the dimensions tool to add all the sizes you require.
Then use the tape measure tool across a length...I picked the prop slot then inputed the value I required 9".
You are asked if you want to resize the model.. Select OK..
Your model is resized along with all the dimensions.
This gave me a basic starting point with all the lengths and shape of the original model
|Jan 04, 2009, 08:38 AM|
Wing Profile ..
I had a few choices here...but for simplicity and ease of construction I had decided to either use a KFm2 or KFm4 section..
Having just had really good results with a KFm4 wing I decided to give that a go first
My first build was at 30" span.. It followed the exact design from my worked out dimensions but was scaled up to the slightly larger span..
The nice thing with sketchup is that a full rescale takes about 30 seconds to do, from your decission to start the program to the end result, and all your sizes are done for you..
The build was exactly the same as for the following instructions, but I came across problems getting the COG back to where it was wanted..
To overcome this the engine / prop slot was moved rearward...twice.. untill an easy cog was acheived..
This rearward slot position can be seen in the final plans..
The 30" span delta flew extreemly well ..BUT it lacked the slow floating flight that is possible with the real Superflys.. I had made it just a bit small for the power system I was using and the wing loading came in too high...
Dont get me wrong here.. the plane is well fast and aggresive in its flight.. Highly manouverable, it just wouldnt get down to the real slow speeds I was wanting
here is the video for the 30" version
|Jan 04, 2009, 08:39 AM|
The KFm4 section had proved itself.. It glides well and is just about stall proof. Full up on low power and the plane would parachute down, still under control. A bit of power and away it would go again
To get the wing loading down and get a slower flight.. I kept the power system the same but worked out that I needed to go up to a 38" span..
EDIT after a lot of flight testing the 38" KFm4 version has proved to be just the best delta Ive ever flown I highly recomend it
So came the Megafly clone ... which was built and flown before the launch of the New 40" version from superfly rc.
The 38" version is built using 6mm depron all through..
The spar steps are 1/2 x 1/4 and were put 50% on top and 40% on the bottom..
Depron spacers in between the wing layers are from 6mm
Glue was uhu por for the laminating plus a bit of cool melt on the tailfin to body joins.
2" colored packing tape is used for decor and hinges.. this also adds loads of strength and stiffness, reinforcing the leading and trailing edges and elevons.. do not leave it off..
heres the video for the 38" version ...... which uses the same power setup
A hefty crash at the end is caused by overconfidence, It was going so well I had to push it. However it showed how strong the build is.. Despite snapping a motor shaft, only a few creases at the nose were the result. The undercarriage was ripped of but this is only held on with velcro so no problem..
The zip file below has the sketchup file so you can load it in and resize to whatever you like
|Jan 04, 2009, 08:40 AM|
Now for some build pictures..
Having a large fly I decided to try for a flea version...I used sketchup to resize to a 24" span.... the original flea is 22" and 7oz AUW max...so that was my target
This Flea version was made from 3mm depron except for the tailfins which I made with 6mm
Step/spars are 3/16 x 1/2 balsa
spacers are from 3mm depron
glue uhu por and the minimum of cool melt.
2" tape for strength and decor
The construction for all sizes is the same, just try to keep the weight down on the small versions...something I find hard to do..
I have made a further mod to this flea design .. to simplify cutting and construction I have made the top and bottom steps identical..
The step runs from the 50% position at the root to a 40% position at the tips. From the way the mega flies its as good either way up...50% / 40% ..so
I am trying a varying step %age.. I could have gone 50/50 or 40/40.. but honestly all the steps have been ok so this is just another experiment..
You can have your steps either way...
First job cut a set of parts for the main wing..
1x full shape main layer
2x (top and bottom) layers shape LE to step
4x half spars balsa ..angle the ends to just butt join at the centre
4x depron spacers
flight results.. a superb small delta, and boy does it go .. from super fast to a gentle plop down landing at the end.. no vices at all and so cheap to make
|Jan 04, 2009, 08:41 AM|
pic 1 the main wing shape cut out
At this stage it helps to mark out the slot size you want, depending on your choice of motor/prop... put in centre guide lines, aileron lines, and put in the lines for the tail positions..I opted for an 8" slot for this size plane
pic 2 top and botton layers cut out
Shape these to fit from the LE to the step position..depending on your choice of step location
pic3 3/16 x 1/2 balsa spars stripped and 1" x 3mm depron spacers cut
pic 4 starting the laminating.. cut trim and glue the spars along the step line.. note they are only butt joined, the layers give the strength here.
Depron spacers fit some where between the balsa spars and the glue line for the layers lamination.
uhu por is used for the laminating, on the small flea a strip of about 3/4 inch wide glue along the leading edges is enough plus of course that on the spars and spacers. Put a thin layer of the glue onto both surfaces, allow to dry then push together.
Fit the spars and spacers, to the main wing layer . then use more glue to fit the top or bottom layer.
Do your laminating on a hard flat surface to get the best results.
pic 5 When adding the outer layers first position the rear edge accurately onto the balsa spar. Start at the centre and push the outer layer down to the nose. work outwards from the centre using two hands to equally push the outer layer down onto the depron spacers and then the main layer.
pic 6 Dont worry if the LE doesnt line up accurately this can be trimmed later, but if youve been accurate and a bit lucky it wont be too far out..
Now youve done one side turn it over and do the other.
pic 7 With both side done your wingtips will look like this...
trim all the ends up flat to each other
pic 8 Add a bit of depron as a tip protector and a fence to keep the air on the wing
Shape and smooth your leading edges
|Jan 04, 2009, 08:41 AM|
pic 9 Tails ...cut and fit... champhered and butt joined ..then use a cool melt glue to reinforce and fill any gaps the fitting has left behind
It takes a bit of thought to fit these well but its not too hard.. keep the slope out angles the same and line all up parallel..
pic 9 and pic 11 .. I used a tube type motor mount fitted in a depron block. which was just laminated to the rear part of the main wing..
On examination this fixing left too much flex at this point, so I have added an extra keel spline under the wing which goes from the nose to the front of the prop slot. It uses two 6mm layers and is just butt joined to the wing
Cut out the elevons from the main wing
see pic 10
I use the colored packing tape to totally cover them, one color on top and a different one below.. this stiffens and strengthens them. More of the tape is used to hinge them, which also reinforces the trailing edge of the main wing, especially arround the prop slot where it is quite narrow
More colored tape is used on the leading edges, for both strength and decor
Servos are fitted into the top layer, fixed with cool melt adhesive.
Control horns are fitted. I use a bit of CF flat to give them a better pull on the elevons see pic 11
|Jan 04, 2009, 11:39 AM|
This multi layered and taped construction will produce a very very tough wing. Without the need for CF spars or extra reinforcing.
No way will this wing fail due to G forces, I had a job to snap one, putting my knee in the centre and pulling on the tips.. I did break it, but flying never will
The KFm4 profile results in a wing which glides well and is stall resistant. It seems to me, to perform better than a proper airfoil. But this is subjective..I love it..
Now for the end result
The mega fly can be made from one large sheet of 6mm.. a few strips of balsa, some glue , some tape , a few horns and control rods.. total £6.00 or 9.00$
You can build 2x fleas for the same cost.
From superfly the Flea is 65$ with motor
the Mega is 89$ with motor
Build one to suit the power system you already have..just scale up or down using sketchup.....They will fly great
|Jan 05, 2009, 07:58 AM|
Oh yes indeed....check the videos
I used the setup below on the 30" and it went very well
superfly 38" clone
motor http://www.overlander.co.uk/product....id=83&pid=2581 this has a stick mount but also can be bought with a radial mount
prop gws 9x5 speed type
Battery 1250 mA 11.1v Rhino.. esc20A any ..sevos 2x 9gm sg9 or similar..
I was talking to Dick kline today via mail and he was saying the KF steps seem to give less drag over the rear of the wing, so that using these might be a good way to go faster... certainly worth a try... hovever the 30" as above was more than fast enough for me, NOTE the motor used above is only a 1000kv job... I dread to think how fast you could get it going with a faster reving and more powerfull motor...For speed freeks check out the motors being used on the twinjet...worth a look ..just make the controll surfaces and connections strong enough and the motor mount fixing sturdy and pushing onto the rear of the steps
|Jan 06, 2009, 12:20 AM|
for some reason i cant watch utube videos i have installed the flash player 10 times but if it is linked into another web site like on here they play just fine ?? wierd
|Jan 06, 2009, 05:51 AM|
theres a program which will download the youtube videos to your pc ..it uses the link adress like that above to find the correct video
.you can then watch them on media player at any time...
On my one they get downloaded as a .flv file which you then re"name" as you like to "name".flv
you have to rename each one or the next download will overwrite the previous
just google youtube downloader
|Jan 08, 2009, 12:04 PM|
Between my tx and crashed aircraft
Joined Mar 2006
|Jan 09, 2009, 05:28 AM|
Oh yes...whoops.... I altered the positions but forgot to redo the text...
please note it is suposed to be 50% at the root and 40% at the tips on that drawing
However you can have all at 50 or 40 if you like it will still be ok, or even like my first build a 50 top and 40 bottom...This flew very well..
So far ive had steps at all sorts of positions ..on my first KFm2 builds I used 50% top steps, but forgot to include the ailerons.. then I had 50% top steps including the ailerons.. Then I tried KFm3...
Step depths went from very shallow to deepish (max wing depth including step 12% of chord thickness)
Everything works....Except having a step right up close to an aileron hinge line..which is why I brought the step at the tips for this one forward slightly
edit just changed the pic....thanks
edit2.. if it looks right it will be ok... ive tried various step locations and now put mine around the 30-50% mark top and bottom and have the same top and bottom...
..If you check out the 24" size pics the step was at about 50% at the root..... but, so that it was away from the hinge line, only 30% at the tip..it works just fine..
I like to make sure I keep steps at least couple of inches away from the hinge lines
|Jan 28, 2009, 03:53 AM|
Hi Dave, thanks for the great build thread, I am making a 30" version and just got all parts on the sheet of depron except for one vertical stab. When you mentioned the Megafly could be built on one piece of depron, what size was the sheet of depron and what KF airfoil was on it. Also what was the wingspan of the megafly? 38" or something else?