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Apr 19, 2020, 04:09 PM
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Build Log

GP Super Decathlon 40


I was in need of a project during the current lockdown and I found this kit in the RCG classifieds. It should keep me busy for a while. My plan is to convert it to electric and I will be looking for ways to reduce weight during every step of the build. The goal is a ready to fly weight of under 6 lbs. on a 5s power setup.
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Apr 19, 2020, 06:49 PM
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I built one of these around 25 years ago. It's a fun plane to fly once you tame the ground handling. I found that my wing had 3 degrees of positive incidence with the stab at 0 degrees. With it being so short coupled, on take off runs, as soon as the wing got light, all that weight transferred to the tail wheel and would ground loop. I found that a quick touch of down elevator got the tail up quick and all was ok. Does wicked spins.
Edwin
Apr 20, 2020, 01:08 AM
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That plane has 1/4" holes in the ribs for a jig. The plans don't call for it but it would be easy to add 3/8" or so of washout by propping up the aft outboard rod. I was given one that was partially built and I took part of the wing apart to add the washout. It will tame the landings and mitigate the stall tendencies.
Last edited by David2011; Apr 20, 2020 at 02:25 AM. Reason: Added photo
Apr 20, 2020, 10:45 AM
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Edwin, I will watch the incidence, the plan calls for one degree positive on the wings and zero for the stab.

David, I think I'm going to use the wing jig method for the wings, if I can find some good straight 1/4" rods. I'm hoping to avoid having to add washout by keeping the overall weight down. About every plane I've ever seen with tip stall problems were also over weight.

Construction starts with the rudder. I substituted some of the wood for smaller, lighter weight pieces, such as the leading edge and cross braces. I also tapered the trailing edge.
Apr 20, 2020, 10:57 AM
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I also substituted some of the wood in the stab and elevator

I used a hardwood joiner with dowel pins (toothpicks) to join the elevators instead of the wire joiner provided with the kit. Lightening holes were cut and the trailing edges tapered.
Apr 20, 2020, 12:35 PM
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Just my opinion, I'd take the wing to 0 degrees.
Edwin
Apr 20, 2020, 04:08 PM
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Starting on the wings, I took all of the die cut ribs and bolted them together. I then used a sanding block to true them up. I replaced a few of the ribs because some of the wood was very hard and heavy. No big deal though.

The strip aileron material provided is barely over an inch wide and the ailerons run almost the full length of the wing. I know that they often did it this way back in the day when this kit was made, but I don't really like it, so I plan to resize the ailerons and make them wider and not as long.
Apr 21, 2020, 11:13 AM
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Mielnic's Avatar
Mine is 8 year's old (although she was brand new at the time of the posted photos ). Nice kit to build and great plane to fly.

One thing I've always regretted in my build was not getting rid of the strip ailerons. Indeed, she will look a lot better with scale-like ones.

I did follow the advice on the washout, and I can say I've never experienced a tip stall. However, the opposite is not necessarily true...
Apr 21, 2020, 11:26 AM
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That's a good looking airplane Meilnic, I may have to borrow your color scheme. Do you know the ready to fly weight? I'm still thinking about the washout but haven't decided yet. I'm working on the wing jig now.
Apr 21, 2020, 12:18 PM
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Mielnic's Avatar
Thank you! I guess I was tired of the standard red-blue-white scheme of every ARFs and I found some pics in the internet of full scale Decathlon's with those colors....

Weight without fuel is 3.150 Kg. OS FS-62 glow & 1.300 NiMH onboard. TOW should be around 3.400 Kg. It is on the heavy side. Definitively handling would be better on the 3.1-3.2 Kg. TOW range, but it's not bad at all. My mistake, I didn't pay attention to weight saving details during the build, as I see you're doing!
Apr 22, 2020, 07:32 PM
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Coincidentally, Iím also working on a Super Decathlon 40. I decided to make it an electric and with advice from members and local hobby shop Iíve installed an eflite 52 motor, a 6S-5200mAh battery, and an ESC-80. At 7# itís heavy, mostly from the battery. Iím debating as to if I need the wing struts. R they just for looks
Apr 22, 2020, 07:33 PM
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Coincidentally, I’m also working on a Super Decathlon 40. I decided to make it an electric and with advice from members and local hobby shop I’ve installed an eflite 52 motor, a 6S-5200mAh battery, and an ESC-80. At 7# it’s heavy, mostly from the battery. I’m debating as to if I need the wing struts. R they just for looks
Apr 22, 2020, 11:59 PM
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I built one of these planes in 1992 and flew it several years with a .61 two-stroke. Still have it, and it's actually in great shape. Very fun plane.

Even though I finished the struts(used Aerotrend foil-shaped tubing), I don't think I ever put them on for anything other then a few pictures. The struts aren't needed for flight. If the wing is built well you can surf on it, they're very strong.
Apr 23, 2020, 01:54 PM
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Superken, I agree with DGrant about the struts, they're just for looks. Why don't you post some pictures of your plane, I would like to see how you're doing your battery hatch.

DGrant, That is a strong wing if you can surf on it,haha!
Apr 23, 2020, 03:05 PM
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I trimmed 1/2" from the trailing edge of the ribs to allow for larger ailerons to be used.

Wing jig is set up and ready.

Ribs are in position with leading and trailing edge spars ready for glue.


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