Rapido

[kc]

About 5 years ago i scaled up the Das Liddle Stik design from RC Modeler May 1968 to make a 50 inch span electric model. Liddle Stik was 46 inch span for glow. I scaled up the plan in the magazine by ruler and calculator- dead easy for straight line models. Scaled up by a convenient factor about 8.5 times the magazine plan to make a about 9.percent bigger plane at 50 inch span.

I used Profilli to get an accurate airfoil - the Liddle Stik and Ugly Stik seem very similar to ' Trainer 60'

I eliminated all the Ugly Stik features like scalloped TE, funny fin and rudder shape and simplified the wing tips. I also used LE sheeting - a big mistake as that takes much time and materials, but a nice stiff but light wing resulted. Spars were 6mm pine from B&Q.

The nose was extended for electric and motor bulkhead ended up 8.25 inches from LE. Probably 7.25 would have been better as the  3S2200 sits well back. F2 was raised to allow a dowel for wing fixing, This gave a chance to taper the nose to a nicer shape.

Edited By kc on 26/04/2020 11:55:29

[kc]

2 mini servos sunk into wing were used for ailerons. Ailerons are straight not tapered or scalloped.

[Bob Cotsford]

That's a nice Stick kc, what motor did you use on it?

[kc]

Thanks Bob.

Motor is a Turnigy 3536/6 1250kv with 3S2200. weight is 3.5pounds with 2200 Lipo. Performance is OK but flight times are rather short - i need to experiment with props.

At the moment it's a 'gentlemans' plane - a bit staid and steady so it's not exciting to fly. Experimenting with CG is needed to make it more responsive and also it's rather reluctant to unstick on take off which is related to cg I reckon.   It's a taildragger and the wheel centre is about 1/4 inch in front of LE  ( whats your thoughts Bob? )

As a Mode 1 flyer in a Mode 2 club there is only 1 other pilot I could ask for an opinion and he is an expert but was not there on the few occasions I brought this model with me, so nobody else has flown it.   Maybe I should get one of my expert pals who fly Mode2 to put it on their TX with a buddy lead!

Edited By kc on 26/04/2020 14:22:30

[kc]

Correction the mag plan was scaled up 4.25 times not 8.5 - the plan was nearly full A4 so very clear detail and larger than most magazine plans that's why everyone liked RC Modeler USA.

( I forgot that only half the wing was shown and compared it to the full 46 inch span!)

[Bob Cotsford]

kc, I suspect that the u/c position isn't far off, but you are probably getting around 90W/lb with that motor depending on your prop. The motor is rated at 34A max and is a slightly higher kv version of the Wot4 Foam-E motor, and that model is around a pound lighter. E-calc says your largest prop will be 11*4 or 10*6, even these are on the limit for that motor but you could probably go up a size for short bursts such as taking off. My UltraStick 60 is very similar but 60" and I run a 4250 ish motor on 6 cells in it. I think you really need to go up a size on the motor to get nearer a 400W setup, maybe 3542 1000kv on a 12*6, still with 3 S. If you could step up to a 3000mAh pack you would get an extra couple of minutes flying time.

If you don't want to upgrade the power system then I'd try bigger wheels, works well for my Wots on grass.  Certainly moving the CofG back may well aid with unsticking but it usually helps more with reducing landing speed.

UltraStick 60:

Edited By Bob Cotsford on 26/04/2020 16:29:52

[kc]

The 3536/6 was tried with a 9x6 APC prop and gave 350 watts at 33 amps

10x5 APC prop gave 462 watts at 46 amps ( too much for the 40amp ESC)

eventually settled on a 10 x 4.5 APC which gave 408 watts at 37 amps. At 3.5 pounds that should be sufficient power.

At 534 sq inches it probably has much greater wing area than the Wot4 Foam E. It would be quite difficult to build this model any lighter, so I don't feel the power to weight or wing area is the take off problem. More likely the wheel position is causing the prop to dip into the grass, so rebending the u/c is due. Easy enough as its a torque rod style.