What size engine should I use?
 

I have an old Ugly Stik that I bought from a guy who built it over ten years ago. It had been sitting in his son's barn since then. It had never flown even though it had all the servos, receiver, and battery installed.

I replaced the receiver with a new Spektrum and replaced the battery with a new NiMh. Everything is mounted about as far forward as possible.

The wing span is 58-1/2". I had intended to use an OS 46AX engine, but once I mounted the engine, as far forward as possible, the plane was very tail heavy (I set the CG at 3-3/4" from the LE as per instructions on the new Great Planes 40-size stik). I assume that plane is similar to mine.

The thing needed 12 ounces of lead in the nose to balance. That makes it weigh 8-1/4 pounds.

So, will the OS 46AX be strong enough to fly this thing?
Or, should I try my TSI 75 engine instead?

Jack

A stick has a fairly uniform chord. measure the chord and balance it about 1/3 from the leading edge if you don't know what brand it is. Usually fairly close to the main spar on a wing like that. Then see how much you need.

You have a 58 1/2 inch wingspan Stick that weighed 7 3/4 lbs without weight added? That seems extremely heavy. A stick is a pretty light airplane, basically a box with a wing on top. Why is this one so heavy or am I wrong about that?

If all your C/G calculations are correct and the plane will require 12oz of lead in the nose to balance, then yes, by all means put a larger (heavier) engine in the nose. I have a G.P. 40 size Stick (a rather old version) and it's wing cord is 12.5". If your cord also measures 12.5" then 3 3/4" is 30% of the MAC. That's a good number. This plane should fly when balanced between 25% and 33% of the mean aerodynamic cord (MAC). 30% is close to the middle of that spec. I have mine set at 29% (3 5/8") and it flys well, and is powered by an O.S. 46 FX but it doesn't weight anywhere near 8 lbs. Double check your numbers and if correct, go with the bigger engine.

I bit the bullet and installed the 75. Right now, with the 75 and the 12 ounces of lead removed, it balances perfectly on the main spar. I'm going to fly it that way and see.

That seems like a very large engine for that plane . It is over weight for some reason . Was the barn damp ?Can you see down into the tail and make sure a mouse did not make a nest in there ?Are the tail feathers solid wood ? If they are you might be able to remove them and replace them with a framed set that would be far lighter . The 46 should be the perfect engine for a plane that size . No doubt the 75 will fly it but its not going to be a nice flying plane .

The tail surfaces are solid. It appears the builder painted the entire fuselage with resin and then Monokote. I can't tell if he used any silk or fiberglass.

bikerbc brought up the point that I was headed for. A seriously overpowered plane will certainly fly but it won't be a relaxing few minutes. For some reason that airplane is seriously overweight. Find out why it is so heavy, fix it and fly it with the .46. It will be a much more satisfying experience.

Any suggestions on how to shave 2-3 pounds? Doesn't seem likely to me.

Well you could completly replace your tail feathers . There is no reason to have them made out of resin soaked solid wood . You could easily save some weight by going with framed tail feathers covered with a film of your choice.

How are you weighing this airplane? Are you weighing it all at one time by hanging it on a fish scale or some such thing or are you weighing each individual wheel and adding them together?

I have a 0-5 pound scale. I weighed the fuse and the wing separately and summed the two weights.
Then I stood on my digital bathroom scale with and without the whole plane.

OK, let's try this. With your 0 - 5 pound scale, weigh each wheel separately with the plane fully assembled then add the three readings together. To do this properly, you will need to prop each wheel up to the same height as the one being weighed. If your scale is, say, two inches high and you are weighing the right main wheel, prop the left main and the tail wheel up two inches. Record all three weights and advise. BTW, this is the way full size planes are weighed.

I tried that and here's what I measured, although I only got the right and left wheels within 1/4" of height of each other.

Nose wheel = 3 lb 0 oz
Left wheel = 2 lb 10 oz
Right wheel = 2 lb 14 oz

I don't know if the 1/4" difference would account for the 4 ounce difference. Interesting that they add up to 8-1/2 pounds.

I'm at a complete loss as to what to think. That plane is simply too heavy for what it is. Since the cg is as it should be now, I suppose the only thing you can do other than replace all that resin soaked wood is to fly it. I would be curious as to just how well it flies being that much over weight.

May I suggest there is one more thing to do before you cast your plane to the winds. Take you plane to an RC Club, find the resident "test pilot" (most clubs have one or two really knowledgeable guys) who can give an "eyes/hands on" inspection. Then, if it passes inspection, ask him to do the maiden flight. He then will be able to give you sound advice based on his experience.

Live long, and prosper
Jerry

That's my plan.

Good plan :rolleyes:

Something just occurred to me. You said this thing was stored in a barn for a period of time. I recall a couple planes I had that had been stored in a garage for an extended period of time and I discovered them to be stuffed full of mud daubers nests from a few inches behind the wing to the tail. Those mud structures are heavy. Just a thought.

I don't see any mud daubers.

It appears that the fuselage is solid plywood. If I could get up the energy, I'd strip the covering off and cut a bunch of holes in it. Probably do the same to the horizontal stab.

Unfortunately, I don't have the urge to do that. Too old and too lazy I guess.

What about just getting a new stik?
You already got everything you need for that.
Just a thought
http://www3.towerhobbies.com/cgi-bin...&I=LXBMM9&P=ML

$$$$
Retired, on a fixed income. I'd love to if I had the money.
That's what I thought I was getting when I bought this one. Oh, well.

Have you tried flying it with the 75 on the nose yet? Living in Fort Worth, you should be getting a day here and there of good weather. We're curious as to how it flies.

Really nice weather, but really high winds lately. No flights yet.

There's a solid bulkhead blocking sight into the rear of the fuselage. But, after closer inspection, it seems the entire fuselage is made of 1/4" extra hard balsa or perhaps even plywood. Tapping on the top, bottom, or sides sounds like good solid wood. That makes me think it's plywood.

The area of the fuselage where the wing opening is certainly looks and feels like plywood. It's been painted, but feels rough to the touch. That's why the plane is so heavy is my guess. So, I'd like to drill or cut some lightening holes in the rear portion of the fuselage. Maybe in the horizontal stab, too, since it's also solid and hard.

Anyone have any suggestions on how I can accomplish that?

Jack