I have a hanger 9 alpha trainer and was thinking of taking the dihedral out. Has anybody done this before and how severe will it change the flight characteristics.

Are you an experienced flyer? Or a newbie?

If your experienced--then go for it. Don't remove ALL the dihedral. It makes the wing look funny. You can cut a new dihedral brace from hard aircraft ply and cut the angle down to 1/2 the stock angle. Even 1/2" of dihedral is okay. Set it up so that when one wing is flat on the table--the other wingtip is elevated 1/2" or up to 1" off the table. That will make the plane a LOT more responsive. Rolls will be smoother, and in general, the aircraft will be more responsive and less sluggish in aerobatic maneuvers.

If your a newbie--then glue the thing together stock and learn to fly first. Later, you can buy a kit and build it however you want. But, for now--just concentrate on learning to fly and don't mess with the dihedral.

The manufacturers build lots of dihedral into trainers for a reason. It makes the plane stable, and offers some self-correcting characteristics.

I've got another option for you. Leave the original wing alone and build a second wing for it. I'm doing that for a Sig Kadet Jr, with a few other modifications. The plane is designed for three channels, with out ailerons. I'm adding ailerons, 3" to each wing tip and a solid mainspar full span. I figure I'll get a little more lift, but have been told the plane will be more likely to sideslip any time it's banked.

with the flat bottom airfoil of the kadet ,when you add the airlerons set thgem up with differential,you want more up deflection than down.this will help with the yaw induced by the drag of the down airleron and help it turn better..only other question is why a solid spar?an upper and lower spar with shear webbing is not only easier to build but is one of the strongest of all wing designs.commonly called d-tube contruction.

I guess I kinda mistyped that. I'm using standard Sig construction, but instead of having two main spar doublers with the dihedral set up, I have a solid doubler running across the top going out toward the tip one extra rib. I have also moved the rear spar forward to allow for the ailerons. To strengthen the wing even more, at least the bottom wil be fully sheeted. It might add an ounce or two, but I'm running dual aileron servos with direct linkage as well, not torque arms or bellcranks. I figure I'm not trying to reinvent the wheel, just do a couple of mods for a more controllable aircraft.

I do this on a regular basis for students & for myself.

As to how much dihedral to remove -- it depends upon what you want the model to do. If it is a trainer type & you want to max its aerobatic capability, you may not only want to remove all of the dihedral, you may want to introduce anhedral &/or cut the wing down into the cabin, to bring the center of lift closer to the thrust line.

The more you take out, the closer to a point-&-shoot airframe you will get -- and the less auto-recovery it will have. A full-out mod will take constant flying (no hands off), but it will be rewarding flying.

I don't think I'm going to do any major work on the fuselage. I'm toying with adding a couple inches to the horizontal stab and adding counterbalances to the elevator, but I haven't really decided yet. Beyond that, it will stay a Kadet Jr. I'll try to post some pics when I get things a little further along

For now i'f I was you I would leave the wing alone ,considering its a 2 piece wing with a tube its not a simple matter of just adding a new center piece and going for it unless you want to recover most or all of it .I'd rather see you bolt the wing to the fuse and get rid of the bands before you to take the dihedral out of it.
BTW Hello Mike hope to see ya soon.

I'm ready almost any time. Just give me a call. We can meet and then I can show you what I was thinking.

I have done this to my trainer and did a thread on it if you are interested. What I immediately noticed was the near self correct characteristics were gone when completing a turn. In other words when you are exiting a turn you will have to use the ailerons to level out the plane. GL

I've probably done more experimenting with dihedral and anhedral than most people so here's how it works.

First, looks don't mean anything, aerodynamics do.

Next, for power planes, except for basic trainers where you want to turn the controls loose and have the plane right itself, you don't want roll stability. (The purist will call this neutral roll stability, but it's the same thing.) You want the plane to go where you point it. Believe me, when you start flying another plane that doesn't have a lot of dihedral and stays in the bank you set, you will love it. Full size planes that go from point to point like it roll stable so they don't have to concentrate on flying. We RCers fly back and forth and do acro so we want it neutral.

Third, the things that affect roll stability and roll coupling (rolling when you put the rudder in) are: wing location, high, mid or low; wing sweep, back or forward and dihedral or anhedral.

Stabilizes and rolls with rudder: High wing location, sweep back and dihedral.

Destabilizes and rolls opposite to rudder: Low wing location, sweep forward and anhedral.

Neutral: Mid wing location, straight wing and no dihedral.

A high wing plane needs about 3 degrees of anhedral on each side to cancel out the effect of the wing location and be neutral. Take just about any low wing sport plane like a 4*40 and put it upside down in your cradle and look at it. It's a high wing plane with anhedral. It flies inverted nicely, does outside loops flies fine. This is the same thing as flying a high wing plane with anhedral upright and doing inside loops. Take a high wing plane with dihedral and fly inverted and it's unstable, wants to roll over on you. Do an outside and you have to concentrate more so than with a low wing plane to keep the plane tracking in the maneuver.

If you can fly and want to experiment:

As for converting an ARF, it's not easy. I usually flip over or make a new dihedral brace and use a piece of aileron stock to fill the gap. Most guys are afraid to do this. I will say this, unless you change the dihedral/anhedral to 6 inches on each side, it won't make a drastic difference. You need an inch and a half on each side. Flat is better than nothing, but it won't correct roll with rudder. It will make it roll better.

Also take off the plastic wing tips, as I recall the plane has or cut the tips square and flat. Then stick on some downward plates extending 3/4" below the wing. This will usually cure roll in a flat wing.

Other things you can do:

Cut off at least 1 rib on each side. Works good on 4*'s, too.

Note: Look at any high wing jet and they have anhedral...

hmmm, I've been building and flying models for the last 42 years, and I have to say that is sound thinking. You got to expect different flight characteristics with dihedral mods. I'd have to agree with Ed Morgan. Interesting. Thanks Ed.

And to think I thought I knew a little about aerodynamics. I have to agree with you Ed, all the high wing Navy jets I've been around had a pronounced anhedral. The ones with the most that I've actually seen were the A-6E Corsair II and the F-8 Crusader, though the A-3 and A-6E/EA-6B(the one I worked on) also have an obvious droop going out to the wingtips. The one plane that DIDN'T was the F-14 Tomcat, but it's technically a midwing design