Naca 0012 high wing, flat stab with no incidence and no engine offset. Would this setup benefit from any incidence on the wing? I'm thinking just a touch of positive on the wing. All replies appreciated.

That one is a symmetrical airfoil, which produces zero lift at zero AOA.

For level flight, that airfoil must have enough incidence angle respect to the airstream (AOA) as to generate a lift force equal to the static weight of the airplane.

The tail should be pretty close to zero AOA at the same time, since it needs to push down in order to balance the whole plane.
The downwash of the wing will suffice to provide a slight negative AOA and push down force for the tail.

Here comes the balance act: too much AOA for the wing will induce too much lift and a higher angle of downwash on the tail: both of which will induce a nose up pitch.

The opposite will be true as well, requiring you to trim the elevator up to induce a higher AOA for the wing, and resulting in a plane that flies like it hangs the tail down.

I would recommend testing 2~3 degree of AOA for a relatively slow/heavy plane and less than that for faster/lighter ones.

Also, a high wing without any engine down thrust will have an up pitch drag couple that will need countering by reducing wing incidence... so until its flown... its hard to say where the net incidence will trim it out.

I was glad to see some replies. Thank you.

What I'm doing is trying to build something similar to an old rubber powered design called the "Cruiser" by Charles Hollinger. Wing area will be around 320 sqin. Aspect ratio 5 to 1. No dihedral in the wing. I do intend to build in ailerons, however.

I have an O.S. OMA-3820-1200 electric motor for power, although I am starting to think this motor will be a bit much.

Thinking out loud here.

Maybe build in a little to much AOA. You can always shim the TE of the wing to reduce the AOA for testing purposes. Once you have it where you want it you can go back and "repair" the wing saddle to fill the gap between the wing and the fuse.

Ken

I would start with zero. You can always add it if needed. Generally fully symmetrical models are set up 0-0-0. One question, why the NACA 0012? It will be hard to slow down, have a relatively high stall speed, and be fast. If you keep the weight down and the area up, probably no problem. Just keep these things in mind.

The need for an angular difference between the wing and tail will depend on where you intend to place the balance point. If you intend the model to be close to neutrally stable then you need little or no angle between the wing and stabilizer. If you want more stability and locate the balance point more forward of the aircraft Neutral Point then you'll need more angle.

If you don't build the angle in then you'll get there eventually with elevator trim used to make the model fly level at cruise speed. However most folks don't like the elevator to be noticably trimmed up or down by some larger amount. Seems they think it makes the model look somehow "broken". So they like to put some angle in so the final elevator trim isn't so noticable.

As mentioned a high wing design generally ends up with the center of drag forces being above the true 3D location of the actual Center Of Gravity. So that alone produces a nose up torque stabilizing effect with an increase in speed. In effect the CoD being higher than the CoG acts like some positive wing incidence.

With all this in mind the answer to your question becomes "it depends". If you want a more stable model with a strong positive pitch stability you'll put your CoG somewhat forward and that'll require some positive wing incidence to counter balance the nose down torque from the CG. If you keep the CG back then you won't need as much built in angular incidence between the wing and tail.

Note that I keep saying "wing and tail". The fuselage center line is a purely imaginary thing. Its only use is as a reference line to compare angles. Once at the flight line the air cares not a whit for the fuselage center line. It only sees the angular difference between the wing and the stabilizer and elevator.

But all in all for a more casual sport model I would suggest that you include about 1.5 to 2 degrees of positive wing incidence. On the other hand if you want to fly it like a hot 3D stunter then go with 0-0-0 for thrust-wing-tail. Then balance and trim it back to where it has no tendency to want to recover from a 45 degree dive on its own but doesn't want to steepen the dive either.

I would like to know a little more information mainly because the airfoil choice and wing configuration are a little odd. Usually a high wing aircraft would have a cambered section and more thickness. Like a trainer.
What you are describing reminds me of a shoulder wing Q-500 design. 12% is the minimum thickness for these planes, and a good example of how fast a 12% airfoil is.
What is the objective of the design? Engine size, wing area, aspect ratio? I am genuinely curious.

The rather blunt leading edge of the NACA 00xx series gives them fairly gentle stall characteristics.

I've built probably 50+ planes over the years that had 00xx's ranging from the 0012 to 0023 and all were outstanding performers with mushy rather than violent stalls.

The 00xx's are my "go-to" airfoil when I design some new aerobatic plane from scratch. When you've got stump puller grunt to drag it around, the 0023 is incredible characteristics.

As an aside, Howard Rush's famous Nemesis II C/L combat plane used a 0012, as did its fully elliptical cousin Bob Burch's Bosta. Both set new standards for performance when they debuted.

I'm curious why I don't see the 0012 on more Q-500's. Whatever it might lose in the straights due to the blunt LE, it would gain back in spades in the turns, and give much nicer landings.

The Q-500's now have a more cigar shaped laminar airfoil. The CP is close 45-50%. They are very fast now.

I agree, I love the NACA 00xx series as well. I have used the 15 quite a bit. It is important to keep the wing loading down though. Great turning for sure and perfect for CL combat. I agree.

Well, Vertical Grimmace, I'm getting back into rc after a long absence. After looking around I located some YS and Jett engines. I decided to build something to fly in the back yard. Ordered the O.S. electric not knowing much about electrics. I don't think it will work on the size I plan to build.

The wing? I don't much care for flat bottom wings. Although most of the flat bottom wings on those old rubber powered jobs looked like maybe 10%. I picked the naca for speed and stability.I originally drew up a 0015, but liked the look of the 0012 better. I build high wings with no dihedral. This is so the spars, leading and trailing edge and sheeting can be one piece. Aspect ratio? I am pretty sure I can build a 5/1 lighter than a 6/1. Wing area? Probably too large for a backyard plane. We'll see. I like a plane with some speed and, as much as you can get in a high wing, neutral handling.

Again, thanks for the advice and taking the time to help.

Well, I didn't have much luck with those 0012 ribs. I'm thinking they are a little too fragile to work with. So I'll be using a NACA 0015. I have also decided to set this wing @ 1 degree positive as a starting point.

Thanks to all of you.

If you breaking 0012 ribs, consider using slightly heavier balsa or just doing a 1/64" ply lamination prior to cutting them. I've found gorilla glue to be outstanding for this sort of rib lamination. After setting for about 90 minutes its hard enough to start shooting through a router/sanders/bandsaw. I do this all the time with center section ribs.

I've also had success using gorilla glue to fab 3/32 "balsa plywood" ribs out of 3 layers of 1/32 balsa. With one of the veneers oriented vertical, any cracking tendency is virtually eliminated.