[RCFlyingKnight]

Hello,

I built a SIG wonder, put a OS 25FX in it, weighs about 2lbs 5oz. standard servoes, and a Berg 7ch rx. The test flight was one of the craziest I've had yet

A few things, first when I give full throttle the plane will climb drasticly to remedy this after verifying the wing and stab incidence,I was thinking of putting down thrust into the engine. Also, it was very pitch sensitive I know being short coupled it would be, but the elevator throw was less than the recommended for test flying. I will be reducing the throw by half. It balanced ok, could it be a bit tail heavy causing some of the pitch problems? Furthermore, it would yaw to the right. The fins are parallel to each other and the center line of the fuse, could the yaw be caused by thr right side being heavier, I didn't balance this way but will be doing so. Finally, the ailerons were set to the recommended throws but I found them to be a bit mushy (the complete opposite of the elevator) I've checked for binding and interference limiting control arm movement found nothing so I'll increase the throw just a bit.

All this flying 1/4 - 1/2 throttle

If anyone has any suggestions on how to cure some of these problems I'd appreciate the input.

M. Smerdon

M.A.A.C. # 38451

[JimMcIntyre]

Originally Posted by RCFlyingKnight

... could it be a bit tail heavy causing some of the pitch problems?

That would be my guess but, the wonder is very maneuverable if you're not used to it. My choice for combat when we used to fly it;

[moo]

25FX?!?!

Originally Posted by sig

with a snarlin’ .15 or .19 up front it’s a hand- launched hot rod

[AJCoholic]

I have flown two Wonders, my own had a piped Rossi 15 and was pretty quick - yet very stable.

On a plane this small and short, the CG is quite unforgiving and had to be accurately placed within an 1/8 of an inch. You should be using some kind of balancer (like a few dowels with the ends tapered to a blunt point set into a wooden block) rather than your finger tips for this one.

The WOnder should fly rock stable with the right CG position. It is extremely maneuverable and quite wild if you have increased throws yet very stable when cruising with the sticks neutral.

I also find the plane very affected by the wind so trim it out when its calm.

AJC

[bavl]

I think 25 is big engine for Wonder. I had a SIG Wonder with OS 15FP on it and it was really fast. It was the wildest plane I ever had. I remember Sig used to advertise it in early 90s as adrenaline booster or something like that.
Andrew is right you have to set the CG and control troughs exactly the way described in the manual. Even after that it will respond to the smallest touch of the control sticks and amazingly it can fly so slowly as well and land in front your feet dead stick.
I had about 15 flights with wonder, all of them were challenging and full of excitement.
I had lots of fun with it until I had a minor crash, I repaired the plane but after that, flying it was mostly struggling to keep it in a straight line.
I sold the airframe in a swap meet I guess for five dollar.
Still have a NIB Wonder kit that Andrew has sent me the construction plans few years ago.

[RCFlyingKnight]

Thanks for the responses,

Moo The 25FX I had sitting on the shelf NIB and didn't think it would matter that much after all you can always throttle back, perhaps an under estimation Otherwise it gives me an excuse to buy a O.S. 15CVA

I'm going have to go buy parts to make the suggested tool to check the cg, dowel and erasers.

I also find the plane very affected by the wind so trim it out when its calm

I wish the wind caused the yaw effect but not the case here. It was a calm evening.

Being that manuverable I hope my flying skills haven't got that rusty. (I had a fool idea a two years ago to start a family and buy a house )

I'll be rechecking everything again. The next flight will be in a week or two since I have to wait for a rx xtal.

[Guest]

A 25FX is no big deal for the Wonder, I've had multiple wonder's over the years, my first ones were powered with OS25FP's, then I had one with an OS32SX-H, then I built the stupid fast wonder with a Nelson 40 F1 engine. I never had one I'd call unstable, the Nelson powered one was harder to fly simply due to the extra weight of the engine and all the mod's I made to it not to mention I clipped the wing and used a thinner airfoil on that one (it was scratch built from the original plans).
CG is pretty important on that plane, but I never had a pitch change at different throttles on any of the ones I've had.

[Guest]

Since some people will probably be interested in what I did on the Nelson wonder, here is a copy and paste from a thread on RCU where I explained what I did differently.

I believe I clipped the wing by about 3" total (didn't bother with the carved wingtips) and cut my own core from foam which was a little thinner, I think it was a quickie airfoil I used. Then I used solid carbon fiber spars, they were actually guitar neck reinforcing rods, they measure .250" x .200" I think. fully sheeted wing as well. I don't remember what I did with the tail, I'm sure I must have used some carbon tow or tape or something on it span wise but I don't remember. I cowled the engine in as best as I could (not a cheek going over it or anything).

I didn't modify the wing hold down which was eventually what led to the airplanes destruction, wing parted company, I also could not fit a bladder tank in there so the engine was a pain in the butt to set.
We had it on a radar reading of 270 which the guy swore up and down was mph and back then I was nieve enough to believe that (and even argued it online like an idiot) but there's no way, I could see it being in kph which would still be a very respectable 165mph-ish.
I think you'd be faster with a JETT50 or something like that though since the Nelson uses such a small prop at such a high rpm, it's just slipping through the air mostly IMO. A lower RPM with a bigger prop would probably work better on an airframe that draggy.

Yes, you can balance it, I split my battery pack in half and put half on each side of the elevator pushrod in the very back,
Would I do it again? no, would I recommend it probably not, would I like to see somebody else do it, sure!

[RCFlyingKnight]

Well, its been longer than a couple of weeks on Saturday I balanced my Wonder more accuratly and added some downthurst in the engine. On Sunday I took it out for another flight. It was alot more controlable but at full throttle it still wanted to climb alot, when trimmed to fly level, upon reducing throttle the plane dives steeply. I'm thinking add more down thrust? I may also need to put some right thrust because it's yawing? Also, it's weight is now up to 2 1/2lbs


On another note, on my other plane I have a OS46AX. It seems to consume the fuel faster than the OS46FX I had on the same plane. Anyone notice this or is it my imagination?

Out of the 8 planes I've built and many others I helped build this is the first one to give me so much trouble.

M. Smerdon
M.A.A.C. 38451

[pianodude]

i might be in for the same excitement.. i am just putting the finishing touches on my wonder and i also will be putting an OS FX.25 on it as it is what i have on hand. i will triple check the balance and throws. wish me luck!!!