From your experiences, what would be the best general shape of the fuse on a profile to provide the best knife edge performance? I'm planning a new electric fanfold plane for indoor and I want to make it easy to knife edge but not hurt the spin, hover, and tumbling performance.
Thanks for your ideas,,,basmntdweller

I can't believe no one here has any ideas. I know there are several "designers" here. Or, does everybody just draw a aesthetically looking shape and call it a fuse? I guess what I'm after is best placement of fuse side area. Would a fuse with a lot of area forward and nothing but rudder in the back be better than say a straight fuse 7" tall from nose to tail?
Thanks,,,basmntdweller

I would say it would high alpha knife edge better than a staright fuse given you had the same amount of fuselage area.

Yes, much better in my opinion.

That's one thing. Most people want an airplane that.. well.. looks like an airplane.

If you want good knife edge with no rudder induced roll, build it the same on the top and bottom. More area up front near the CG gives a lot of lift.
The less vertical stab you have the better for "kicking" the plane around or in high alpha.

Below is my design with this type of thinking.
Note that my vetical stab runs full length of the rudder. On my first design of the same plane I used large counter balances and it did a little better KE loops and also high alpha KE.

Bill

I think the key to this question is what are you looking for? if you want something that will knife edge well, surface area is important. And you need lots... I dont think it's that critical that you put more up front than back... but you need to balance the amount of surface area above and below the wing to reduce coupling. the verticle stab area must be considered as well... That's why the rudder is normally tapered... to give some surface area below the thrust line.. Horizontal stab to wing coupling is important too for high alph knife edge. if the plane is too short coupled, knife edge wont be as stable.... But spins will be tigher... Everything is a trade off.

Hey Bill - That's a pretty interesting looking bird... How does she fly? is Knife edge pretty clean?

Gotta agree with Swany on this one.....

Have tried many fuse shapes in the past year or so...

I have tried purely scale shapes... and shapes that were pulled from the air...

Wing and horizontal placement relative to thrust line end up being critical factors as well as amount of vertical stab and rudder above and below the thrustline

When I designed the HalfWit, I wanted to get a small airplane to knife edge well on relatively low power. To achieve this I tried to get almost as much rudder and vert stab below and above the thrust line. Additionally, it has the wing, engine and stab on a common centerline. Consequently it knife edges very cleanly and with almost no coupling at all. It also knife edge loops better than any plane I have flown before. (all this on a .061 engine)

The other consideration I have been playing with is where the balance of the side area resides on the fuse (nose to tail). Many pattern ships have canopies well forward to increase the side area up front. On the other hand some have it behind the trailing edge of the wing. Both will knife edge, but one will do it with less effort, and one will require more.....

As Swany said, it depends heavily on what you want to do with the plane.

Flies great. I've flown lots of stuff, and I find the Symmetry to be the best. It's only bad charateristic is tumbling. It's pretty big for a .46 power fun fly and therfore not the best at tumbling. But it does everything else so well that I don't care. If I get the urge to tumble a lot I'll grab one of my shorter coupled profiles.
Knife edge is dead solid.
You can fly it knife edge from one end of the field to the other with your right hand off the Transmitter.

basmntdweller,
For my foamie electric I'm thinking about using the outline of a Yak fuse, but omitting the bottom part and mirror imaging the top profile line for the bottom. And then stretching the canopy area forward.
I guess one thing to consider is not making the fuse height to large, because of it's tendency to add roll stability to the design.

Bill