American Nightmare

[Mowerman]

Has anyone else built Peters 'American Nightmare'?

I have just built one, converted to electric power.

(Photos will be in my album shortly)

Not flown yet as we have just lost our club flying field also I managed to kill a Lipo by leaving it connected after setting controls on another model

[Mowerman]

Here it is.

[Bob Cotsford]

I bought one off a clubmate, it came with 400 brushed motors so I swapped them for a pair of small Keda brushless from GC. It needed about 5 degrees of downthrust and a forward CofG to make it manageable but it gets of the ground double quick. It swallows a 3s 3000 LiPo in the nose nicely, with two 30A escs in the centresection and long motor wires out to the nacelles. It gives around 15 minutes of mixed flying. It doesn't like negative G manouvres though.

[Phil 9]

I like this model. The plan was in the very first RCM&E I bought.

 

being stupid and knowing nothing about aero modeling I thought I would build one but to make iy more for a begginer just put one engine in the middle. I didnt in the end (good job too) and bought an artf that did not last long. But i always remember the plam

[Mowerman]

Bob.

With 2 brushed 400 motors I suspect it would hardly fly.

I have fitted 2 180W outrunners with a 1000mah 3s lipo in each nacalle.

A 4.8 nmh in the nose for the radio.

Weight is 3.25 lbs so hopefully enough power (110W / lb)

Edited By Mowerman on 30/03/2011 19:06:02

[Bob Cotsford]

If I were to change anything it would be to extend the rear fuselage, enlarge the elevator, or both. It's not unstable, but it does need the c of g quite far forward and even then it doesn't need a lot of movement on the controls.

 

It does look and sound different in the air, in a good way!

[Bob Cotsford]

Just checked and in fact the motors I used were Keda 2834/16, 1100 kV, 290 W! No wonder I had to prop right down to 7*4s to stop it going vertical on 3S.

[Peter Miller]

Just checked my list of threads and found this.

 

Mine went like a rocket on two .15s. I saw one on Ebay where the builder had fitted two .25s. He had increased the span a little. Now that thought fills me with terror!

 

Mine was fine with the CG and everything else as shown and as shown one the plan

 

Can't understand the need for down thrust. The centre of drag is below the thrust line.

[Mowerman]

Peter

Thanks for your input.

A chap in my old club built one with 2x .15s, that went like a rocket untill it met a trainer going in the oposite direction! the resulting 'confetti' covered a large area

[Bob Cotsford]

It doesn't need downthrust any more! Last sunday I got caught out by what I assume was a stall on landing, the model dropping in and cartwheeling from about 2'. That was at our rugby pitch site where short approaches are the order of the day, in blustery conditions. It wasn't a particularly heavy impact, nothing drastic and at first glance it looked like minor damage but because of the way it had been finished with paint on bare wood everything developed cracks along the wood grain - fuselage sides, tailplane elevators and rudder. It really was more fragile than I'd expected, I guess that's what you get with second-hand models. I'm sure that if the balsa had been treated the traditional way with doped on tissue, it would have survived with hardly a mark.

 

I think the large amount of downthrust was needed because of the flat bottom wing section, without downthrust it flew fine as long as the speed was kept low, but with 300W + it just wanted to loop at more than half throttle and needed large trim adjustments with speed.

 

It's a shame as it did look nice in the air, and even with electric it had a distinctive sound on low passes.

[Peter Miller]

I can imagine the confetti. Ouch!

 

Bob

 

I suspect that there was something else out of line. The flat bottomed wing is set at 0 degrees incidence. This works just like a symmetrical section. On my baby rocket it needed no trim changes at any speed.

 

0 degrees means that the line drawn through the centre of curvature of the leading edg and the trailing edge is set at 0 in relation to the thrust line and tail plane.

 

Possibly the previous owner added positive incidence because he was flying on marginal power.

[Bob Cotsford]

I know the previous owner thought it was too 'invigorating' for him on two 400 brushed motors and 6 cell NiMh, and I found that if I moved the CofG back even a few mm it became unstable so I do question how accurately it had been built. It also had quite a small LE radius, which I always thought made a wing more pitch sensitive.

Anyway, it's sadly academic now.

I'll be interested to hear how Mowerman gets on.

 

Right, 2 * 30A esc, 2 * motors, 3000 3S LiPo, 4 micro servos - what next?

 

Anyone fancy drawing up something like a cartoon scale Henschel 219 or aKawasaki Ki45 just to be different?