CafeenMan

OK, I have a set of ribs for the wings. There are 42 ribs and 32 half-ribs. The chord is 7". The Airfoil is a 15% symmetrical that I made up.

I'm planning on about a 36" span with ribs spaced 2" apart. I cut extra ribs to give me leeway.

This model is intended to be as light as possible. I'm not making a scale aircraft. I want a plane that flies light and is extremely aerobatic. The rib set weighs 0.75 ounces so I'm off to a good start. Both wings will have full span webs between the spars. I haven't decided on balsa or spruce spars, but probably spruce because they're small (1/8" x 3/16")

The engine I want to use is an OS .26 FS. But it's an old engine that was given to me and when I put it on my test stand I was really underwhelmed with its power. It seemed weary. I don't have anything else in that range other than old .40 2-strokes, a wankel and an old .28 2-stroke. I want to swing a large prop, so I may have to break down and buy a .40 4-stroke which would be pushing the limits of the airframe.

The fuselage and tail feathers will be completely built up. I will use pull-pulls for rudder and elevator with HS-85's on all flight surfaces. Both wings will have built-up strip ailerons with a servo in each panel of the bottom wing. Probably an HS-55 for the throttle.

So the questions are:

2 straight wings?

Top wing swept, bottom wing straight?

2 swept wings?

Nose and tail moment?

Distance between wings?

Vertical location of thrust line. I'm thinking the horizontal stab will be on the thrust line.

The whole model will be set up 0-0-0-0 (wings, stab, engine)

Tall Paul

A .25 would be kinda poopy with that much wing.
The .40 is a better choice.
These two use .40 FPs and are quite manuverable even though heavy..
For your aerobat..
Wings about .8 to 1.0 chord apart.
Stagger looks good, but not too much, maybe 3/4".
Nose about 1 chord, tail 2 chords.
0-0-0, horizontal on thrust line.
Build in lots of lightness.
Try for around 3 lb.
Ailerons can be on both wings, but lowers only with lots of chord are effective.
If on both wings, use two servos, connecting the lowers to the uppers with pushrods.

CafeenMan

Thanks TallPaul. I'm actually shooting for 30 ounces. I doubt I'll hit it, but I want to stay well under 3 lbs. I know there's lots of drag, but I'm not concerned about that. Speed isn't an issue. But I also don't want to have to dive to loop. In fact, I'd like enough power to go vertical.

CafeenMan

Moving right along...

I decided to make the wings straight to save the weight of joiners. This is the top wing having full span spruce spars and 1/16" shear webs. It will be difficult to break, but I expect it to weigh about 4-5 ounces complete. Span will be about 40" for both wings giving it a wing area in the neighborhood of 560 square inches.

Target weight of the completed model has been revised to 40 ounces ready to fly (dry).

The curve you see in one of these photos is an effect of the lens. The wing is straight.