Hi there.

I have been thinking of scratch building a twin. I have a twinstar that I have been flying for some time now. The fuse got destroyed so I made a new one and did some mods to it. Took off the 25s and put on some 40 Ervins and had a ball. Love the plane.

What I am getting at is I was going to take the wing of the twinstar and blow it up to about 80” wing and go from there. But when I did that I found out that the airfoil is the same as a Robin hood 80” wing that I just happen to have. The more I looked in to it the more I liked what I was seeing. Now the twinstar is a great flying plane. And if I make this plane the same it seems that it should fly about the same. I hope.

Now the Twinstar has about 4 degrees of left thrust on the left engine and 5 degrees of right on the right engine. On this new one that I want to make should I do the same thing to it? I guess I should have said that I hope to put two 25cc weed eater conversation on it. (That is just the plan for now. That just mite change.) I plan on using gas so I can just run one tank in the fuse and not have to mess with tanks in the wings.
The wing is semisymmetrical and I have no idea on what the incidents should be. I have seen a lot of post on here about seting the engines at 0.0 so I thought I would just ask and get all info I can before I start cutting in to this wing. I will put pics up as I go. That is when I know what I am doing before I go. Lol

I am still in the planning part of this and all info or help would be nice

Paul

I would go with a symmetrical airfoil so you'll have good outside capability. It also makes it easier on the pitch trim when you over power.

I did the out thrust testing. The magic number is 8 degrees, from my testing. With this amount, you'll have negligable yaw with an engine out. If you don't use out thrust, consider pull-pull on rudder and a strong servo.

There are a lot of people here on the web who will tell you anything, but there are very, very few who have actually done any testing. The guys who'll tell you to use 0-0 are the same guys who don't use right thrust on a 3D plane. Look at all the really good 3D fliers and their planes have right thrust. I'll admit that 8 degrees looks like a lot. I think Hobbico put in enough out thrust to help, but not enough so it would look unusual to the novice twin flier. If they went to much more they might lose sales. If you do the math, 8 degrees out thrust will cost you less than 1% of your forward thrust (cosine 8).

Are you saying 8 each or 4 each to make 8? I run 2 % right on all my plans. Makes it so much ezer and takes out the work in flying. I am not going to go with 0.0 I know that just makes more work to fly and alot more trimming.

Thanks for the info.
Paul

I would think the the amount of out thrust would be porportional to the distance from the centerline of the aircraft for any given size craft? Closer to the center, less out thrust needed.