250 gram airplane build comparison

[model14]

I'm just getting back into RC after 15 years away. I just completed building a TF Mini Tiny Trainer for 3 channels. This was my first-time using foam and hot glue. The plane went together easily. Final weight of the foam structure was 184 grams. Final flying weight with electronics and 900 mah battery came to 302 grams.
Since I had to wait for my new transmitter (arrives today), I built two additional planes: one using Elmer's foam and one using Readi board. I also constrained my build to one 30 x 20 sheet per plane, necessitating a 30" wingspan down from 36". I followed the same technics as used in building the FT trainer.
The Elmer's plane came out to 341 grams, the Readi plane came out to 231 grams. In all three planes the servos used are the heavier 9gms vice 5gms.
The Readi plane is way under the 250 gram FAA stupid limit and the Elmer's is way over, as expected. Looking back at my building experience I believe I could build a 250 gram TF trainer by using 5gm servos and cutting way back on the glue (I know I used way too much) and dropping the battery to a 400 -.600 mah.
I liked working with the Elmer's foam. It is a lot more solid and easier to work with. I believe the Elmer's plane will take a lot more abuse, and with a little more power fly better in windy conditions. The Readi board is really cheap, more "flimsy", and has ripples in the surface. I don't view it as very crash resistant. The proof will be in how they fly, of course. I expect to let you know by the end of the week. I would appreciate your comments about your own experience building and flying such small and light planes.

 

[model14]

Still haven't been able to test fly the planes. Hopefully soon. I did a water test on the Elmer's and was pleased to see the covering is water resistant. I wet a piece down pretty good and no wrinkles or delamination. The paper covering is permanent. It can't be removed without destruction.

 

[model14]

Just got back from flying the Tiny Trainer. Flew perfect, and I did pretty well for being away 15 years. I had someone else make the initial trimming flight and then I took over. It all came back quick. The Tiny flies straight and gentle and is very stable. It is underpowered with the A pack motor, but that is okay with me. Wind picked up and I decided to wait on testing the other two planes. Hopefully tomorrow.

 

[quorneng]

Model14
That is interesting.
Keeping within the 250g weight limit is quite a challenge and is subject to foam used and the design involved.
Using a suitable foam (2mm Depron?) and some careful reinforcing it is possible to achieve some serious deigns.

 

[model14]

Flew the 230-gram Readi plane this morning. The plane is very sensitive to control inputs and aft CG. First flight was a wild ride. First up elevator after launch sent her straight up and over. That got my attention, but I recovered okay. Landed and changed endpoints to 50% and expo to 50% and moved the CG forward. That tamed things down pretty good. It is capable of quite slow flight at low throttle. I'm very pleased with the outcome. Anxious to install ailerons. This plane is going to be a lot of fun.

 

[model14]

Recent testing ( (8) Power Pack A wattage | FliteTest Forum ) shows the Tiny Trainer to be powered at about 75 watts per pound. It is underpowered for sure. I am trying a 3S pack today.

 

[Piotrsko]

Not watts, thrust. A "C" class motor spinning a 6-3 won't generate much thrust but it will be fast.

 

[quorneng]

This is probably my most successful and long lived sub 250g plane. A scratch built Super Cub.

Using just about every light weight trick I could think of it is quite big at 40" (1150 mm) span yet only weighs 242g with a 1000 mAh 2s on board. Its weight is displayed in big letters just so you know!
3.7 g servos for the ailerons, elevator and rudder. It uses an Emax 2805 1500 kV turning a 7x6 prop.

The wings are skinned in 2 mm Depron over 2 mm Depron ribs. There is no spar making the balsa wing struts fully operational. The fuselage and formers are also 2 mm Depron. The 60 mm diameter wheels have tyres in grey Depron over printed hubs.

Each wheel weighs just under 3g,
The undercarriage wires pass through acetate plates glued to the sides of the fuselage.

A light but strong way to pass the landing loads to an area of Depron.
The wing struts are also anchored to the rear undercarriage wire.
The end result is remarkably strong.
Supported just by its wing tips it can carry an additional centre weight of 18 oz (510g).

Flexing a bit but it is roughly the equivalent of pulling a 8g manoeuvre.
Maybe not everyone idea of simple and quick it was actually built in 2013 when the 250g limit was no more than a proposal.
I still fly it but only on those really calm days.

 

[model14]

Good looking build there Quorneng. I see numerous good ideas used in your build that I will use in the future. I wasn't able to try out the 3S pack in the Tiny Trainer yesterday. Maybe Tuesday.