TOPMODEL CZ GRAFAS glider - Page 2 - RC Groups
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Feb 03, 2011, 03:44 PM
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mikmerl's Avatar
Further work to the fuselage

Trial fitted the elevator bellcrank in the fuselage and realized that the curved slot for the forward horizontal stabilizer actuator pin needed to be widened.
Go carefully and check continuously so that the stab dowl pin follows the curve without rubbing on the fin during its travel. I can’t understand why this could not have been done by the manufacturer to the correct width as they already prepared the slot.

I was not happy with the elevator servo to bellcrank linkage. The supplied ball link is in the right direction but the other link (fork type) cannot be successfully used. Due to the rotation of the servo arm the link on the elevator bellcrank suffers some serious binding as it can only operate linearly. (possibly if you go opposite to the method indicated on the drawings and install the ball link on the elevator bellcrank and the “fork” link on the servo arm you may have an acceptable result). I decided to discard all of these components and use ball links from my helicopters on both ends of a pushrod. (I am a model helicopter nut in one of my other life’s)

Fortunately the resulting linkage setup works silky smooth and with no slop.
I completed the linkage and glued the supplied PU foam servo mounts in position inside the fin. Ensure that servo arm is at 90 degrees and that the elevator bellcrank is also at zero degrees so that you have equal movement both up and down.

I used the outer most hole on the Hitec servo arm and the inner (closest to pivot point) on the elevator to ensure full elevator travel.

Recheck that everything is OK before progressing to the next step.

The balsa rudder tail post requires some tailoring so that it can fit into the fin. Smear the edges of the post with 5 min epoxy glues and slide it into place. Use clamps (with pressure distribution strips) to hold everything in place until the resin sets. I did not glue it flush with the ends of the fin but pushed the balsa inwards and allowed the fin ends to protrude about 1mm.
Last edited by mikmerl; Feb 03, 2011 at 04:17 PM.
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Feb 05, 2011, 01:47 PM
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Just came across these - I think your missing instructions though the model name is given slightly differently?
Feb 05, 2011, 02:45 PM
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mikmerl's Avatar
Thank you nsrj that’s very considerate of you to go to the trouble.
I have the instructions for the GRAFAS glider featured in this thread, in the earlier posts in this thread Graham was referring to my other new toys (Xplorer 4000e)
It is not uncommon for this type of glider to be supplied without instructions due to the high degree of prefabrication and the assumption of the manufacturer that anyone buying one of these knows his way around them.

Thanks again
Feb 05, 2011, 03:09 PM
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mikmerl's Avatar
More fuselage

Cut away the covering film from the hole in the center section where the carbon dowel pin must be glued in place. Then slightly roughen up the pin where it will be glued into the wing, clean the pin with acetone and epoxy glue it in place.

Mark the position in the fuselage where the hole must be opened and drill the hole through (I used a tapered reamer which allowed me to get a perfect slightly tight fit)

Wing bolts are another area that I deviated from the plan. Instead of the blind nuts I doubled the thickness of the supplied plywood plate by gluing an additional piece of aircraft plywood to it and then and then clamped this in place until the epoxy glue had set.

Then I carefully aligned the center panel of the wing in the fuselage. Years ago I made a very useful tool for this job. Using a piece 2m of 1.5mm piano wire I heated up the tip till it was bright red to soften it and turned a small loop in that end. Then using a T pin pushed into the very tip of the vertical fin as a reference point. Then I move the piano wire alternating from one wing tip to the other making small marks on the piano wire with a black marker and making small adjustments to the wing position until I get to the point where the mark on the piano wire perfectly aligns with both wing trailing edge tips.

Now that the wing is perfectly aligned in relation with the fuselage mark the two spots that have to be drilled through for the wing bolts. I did the drilling with the wing in place using it as a drill guide. During drilling, angle your drill so that it is perpendicular to the top side of the wing at that point.

I drilled through with a 3.75mm drill and then soaked the hole with thin Ca glue. Then using a 5x.8mm tap I carefully cut a thread into the wood, when this was done I soaked the new thread with Ca again and allowed it to dry completely. Now I have the threaded holes at the desired angle. I have been using this method for years and it works great even on giant scale gas models without a single problem. These threads will not pull out.

Open two slots in the bottom of the rudder and glue the two supplied control horns in place. Cut slots in the balsa fin rudder post adjacent to the slots precut in the rudder for the three supplied hinges. Make sure that everything aligns and works freely and glue the rudder in place. (BEWARE in my case the bottom hinge that protrudes into the fin did not allow the bellcrank to complete its travel limiting up elevator. That lead to a lot of swearing and some intricate surgery to cutaway the offending piece) Check that you don’t have tis situation before you glue this hinge in place, if necessary cut the hinge down before you glues it in so that it does not protrude through the balsa post.

Glue the plywood rudder servo mount into position (for whatever reason this is cut too narrow and sits too low down in the fuselage not allowing enough space for the servo. I was too wary to fabricate a new one and I simply glued it in place and added two ply spacers to raise the servo to the desired height. All the necessary cables and bits are supplied to make up the pull/pull rudder control system (take your time and get it right the first time, when you squeeze the brass tubes there’s no going back)
Adjust the cables until the rudder is neutral at mid stick (and trim), the cables do not have to be guitar string taut for a slop free setup. In fact the servo will appreciate it as well if you cut it some slack. Try to get all the throw that you can.
Last edited by mikmerl; Feb 05, 2011 at 03:29 PM.
Feb 06, 2011, 05:17 PM
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mikmerl's Avatar

I started by applying the hinge tapes to all three panels. Some years ago I ran out of the “special hinging tape” that I had been purchasing and out of desperation (I wanted to fly the next morning) decided to use what I had on hand.
I use transparent packaging tape which is very tough the adhesive is perfect on the plastic covering films that we use on our models, my only problem was the unusable width. I solved this by finding a suitable spacer block (according to the width of tape that I need and place a fresh sharp blade on top of that. Then with one hand holding firmly down the blade and spacer I gently press the roll of tape against the blade while at the same time rotating the roll a few times. This gives you a nice clean cut “hinge tape” at the desired width.
Next I turned my attention to installing the four wing servos (two for flaps and two for ailerons) The VOLZ servos I had were supplied with a very handy CNC routed plywood mounts that I used (I liked them so much that I cut a few new ones for some of my other projects). I could not use this type of mount with the Hitec HS-125MG on this glider as there was no space, in fact I had to cut a slot in the wing rib of the aileron servo bay to accommodate the mount lug on the bottom of the servo case so that the servo output arm is aligned with the aileron control horn.
Make up the necessary wiring extensions and route these through the preinstalled guide tubes then screw the servos in place. Make sure that the servo output arms are at the desired positions and the arm screw is firmly tightened before final servo installation.
The control horns need to be installed next, I cut a slot in the aileron (hand pin vices work great for these tasks) so that the hole of the horn is as close to the hinge line as possible. For the flap servo I simply used the provided slots. The holes in the control horns (and the servo arms) have to be drilled out to accommodate the pin of the pushrod linkage clevis.
Mark the desired length of the pushrod and create a “Z bend” then cut off the surplus wire. After doing that for all four servos you are ready to assemble the three pieces of the wing at adjust the travel direction of the servos, the differential of the aileron servos (about 50% usually works fine), the flap deflections and any combinations of all four of the above (five/six if you mix flap-elevator and or aileron-rudder).
Next I completely assembled the model and placed it on a balancer (adjusted to 80mm from the chord leading edge). Then I taped a light styrene cup to the top of the canopy above the position where the battery will be. I started adding lead shot to the cup until the glider balanced horizontal. Place the cup with the lead shot on a scale and record the weight. With this method I can now purchase flight batteries to this weight and the glider is be balanced without non productive ballast.
Feb 07, 2011, 03:54 PM
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mikmerl's Avatar
It just floats and floats and floats…………………………………

Today the weather was incredible not a cloud anywhere, perfect visibility (severe clear) zero wind and around 18 degrees Celsius.

I literally threw the last remaining items in the GRAFAS (ESC, battery, BEC etc) and headed off to the field.

I balanced the model at 80mm from the leading edge with a 3cell 2200mAh LiPo (and some ballast) did a radio check (took a few photos first, you never know) and launched the bird.

It flew positively out of my hand in a steady (about 40 degree climb) with absolutely no drama. I allowed it to climb for about 15 seconds more and cut the power, it leveled off and when into a straight as an arrow glide. It needed a few clicks of elevator trim and nothing else.

I allowed it to continue for a few hundred meters and initiated a gentle open turn using only rudder. It came around absolutely flat without the need for any elevator. I flew it around for awhile testing its response to all the controls, I noticed no bad characteristics or tendencies and very soon I was comfortable enough with the glider in any flight attitude. I even rolled it on its back and flew a circuit like that, I can’t say that it was very happy inverted and was trying its best to achieve normal (right side up) flight path.
After about 10 minutes of getting used to the model I realized that I was at about the same altitude that I was when I cut off the power after the initial climb. Without even bothering to try to find lift the glider was keeping its height on the light early afternoon lift that it was flying through. In the hands of an experienced thermal sniffer he would easily keep it up for a long time in light lift conditions.

I decided to bring it down for a look over so I dropped the flaps around 45 degrees and the glider reared up as it was flying quite fast. Down elevator brought it back to level flight and with a much lower air speed it settled into a glide that allowed full roll and pitch control. I can’t say that I was losing altitude fast even with the flaps deployed. When I finally lined it up for final landing approach it passed by me at about 4 meters altitude and just kept going and going.

I realized that I would have to come in even longer from further away. Possibly some flap aileron mixing would be beneficial in getting this clean, efficient glider down for spot landings.

Next I threw out the 3 cell LiPo and substituted with a 4 cell LiPo and the climb rate became more to my liking. It goes up vertically if you like or very briskly at about 70 degrees to any spot in the sky where you want to be quickly.

I have not loaded up (ballasted) the model to see how it handles with a higher wing loading and probably will not do so. I wanted a glider that could handle higher wind conditions than my AVA but less that my all Carbon/Glass molded gliders can fly in. In my opinion it fits perfectly in there and I believe it can be a fantastic allround weekend glider with entry level competition capability.

It has been a rewarding project that is within the scope of the average builder/flyer. I don’t think that an absolute beginner should start with this kit unless he has an accomplished modeler to oversee the assembly and instruct with the flying.

I hope this rudimentary introductory/build thread has been of some use to somebody.

If anybody needs more info I will be very happy to reply to any questions.
Thanks for listening

Happy landings
Feb 07, 2011, 08:01 PM
AMA 7224
Leadchucker's Avatar
Nice job on the build log and the plane Mike. I fly the Avia inverted too, usually after doing a hammerhead,a roll then a split S into inverted. Hope you have a blast with her!
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Feb 15, 2011, 01:56 PM
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vulpina's Avatar
I might get this one as my AVIA just snaped its wing at the dihedral ...
Does this GRAFA got aluminium wing joiner and not wood glued like the AVIA ?
Feb 16, 2011, 07:54 AM
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mikmerl's Avatar
There is no aluminum wing joiner on the GRAFAS.
It has a strong one piece center panel about 1330mm long with a carbon fiber tube spar.
The outboard panels slide are attached by one 130mm long by 8mm diameter glass fiber rod that slides into both panels and there is a small carbon incidence locating pin towards the rear to keep the two panels aligned.
Personally I would have liked to for this rod to be longer and extend to at least the next wing ribs on both inboard and outboard panels.
I imagine that for normal electric power flight loads it is adequate but I would not recommend doing anything extreme with this bird.
It was designed to be a graceful thermal floater.
Hope this answers your question.
Feb 16, 2011, 09:05 AM
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vulpina's Avatar
Thanks mike , it look alot stronger thant what used on the avia with the wood plate inserted in both carbon spar .
Feb 16, 2011, 10:18 AM
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mikmerl's Avatar
The AVIA is a bit smaller and lighter so I imagine that the design is adequate for that bird.
The solid rod supplied with the GRAFAS is very strong (possibly stronger than the slots in the wings)
In general I don't know how you like to fly but if it is gentle thermal hunting then the GRAFAS is very good.

May 09, 2011, 12:50 PM
Gravity is patient............
So mikmerl, how are you liking this sailplane? Any updates?
May 10, 2011, 12:20 PM
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mikmerl's Avatar
The Grafas has more than 60 hours air time and I have enjoyed every minute. It is very predictable and has displayed no bad characteristics

The large wing area (light wing loading) allows the glider to float on the lightest of lift (makes the lousiest pilot look great). Mine weighs 1900grams with a 4 cell 2200 Li-Po, heavy Align 60A helicopter type ESC and a separate BEC. (and some lead as well for balance)

I have had the glider to speck in the sky heights many times. One day I imagine that Eolus (the god of the winds) will take his revenge, I must resist the temptation of riding thermals to such heights. I recently purchased a small GPS to use onboard my gliders to see what speck in the sky translates to in meters but have not had the opportunity to use it yet.

Battery access is very easy through the huge canopy and you can really play around with battery size as the space is carnivorous. Some sort of battery tray must be made to keep the battery from sliding back and forth.
The motor that I have installed can literally yank the glider vertically out of sight so you could use a tamer unit but you would still need weight up front so it may as well be productive.

The construction is of good quality and is so far showing no signs of stress, fatigue etc. Even after a dunking in sea water. Yes I hang my head in shame, I made a low level swooping turn over the sea and a wing tip touched the surface. The glider nosed into the water and I went for a very cold winter swim. I thought that was the end of the Grafas but to my surprise very little water had entered the wing, only the bays where the servos reside.

I of course threw away all the servos, the receiver, motor ESC and all wiring and redid a complete installation with new ones. The glider has more than 50 hours since that idiot mishap.

To sum it up.
Good quality components that go together easily.

Flies beautifully and is great for fun flying or F5J competition flying.

I would purchase it again and recommend it to anybody contemplating a glider in this class/price range.

May 28, 2011, 08:32 PM
USA: LakeGeorge, New York
Do you recommend any other 3m sailplanes that similiar performance to the Grafas?
May 30, 2011, 02:57 AM
Registered User

Very beautiful model. I started to assemble the Topmodel Fascination.
MAy i consider to buy a Grafas wing for it, i think they have the same fuselage.

Could you measuere me the wing root chord and the 2 screws position from the leading edge?

Thank you

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