Today I'm going to start building my Sig Mid Star 40 powered by a TT Pro 46. I'm thinking of modifying a couple things on it already and I want to get your thoughts.

The first thing is, I don't want the exhaust going directly onto the wing. Should I: 1) get a tuned pipe or muffler to get the exhaust beyond the leading edge of the wing, or 2) mount the engine 90 degree's off to put the exhaust beneath the plane?

The second thing is the wingtip's. Should I keep them as the are or get rid of them? What purpose do they serve?

The third thing is the ailerons. I have an extra servo and I was wondering if it's worth the extra weight to get rid of the torque rods. I will be building the plane as a taildragger so I won't have the weight of the nosewheel.

strikerone,

The Midstar 40 and a TT Pro 46 sounds like a great combination. I have three TT 46's and absolutely love them.

To keep the exhaust off the wing, I'd rotate the engine 90 deg. You'll have plenty of power without a tuned pipe.

It's been a while since I've flown a Midstar (flew someone elses back in 95), so I don't have an opinion on the wingtips.

Going to two aileron servos is definitely worthwhile. The weight increase is insignificant, but you gain alot of flexibility. For example, you can mix in differential aileron to reduce adverse yaw.

Good luck with the Midstar.


Rob

I built my Midstar with an OS46FX. I would recommend rotating the engine 90 degrees. These are a dirty plane even with an exhaust diverter. I left the wingtips, I cant really tell you if they serve an important purpose but I think they look good. I also went with the dual airelon servos as you are thinking of. Even as a tri gear with the 46 the plane came in around 5-5 1/2 lbs. Light plane once complete. It will fly great with the PRO46.

The Mid-star is an excellent plane. I built one and flew it for awhile before just recently selling it. I built mine stock but there were some mods that'd I'd put on one if I built another. In order of importance;

Must do things I had to do;
1. Put a small piece of triangle stock on top and bottom of the horizonal stabilizer to beef it up.
2. Put a Sullivan tail wheel on it.

Basic mods I wish I'd done.
1. Loose the wingtips.
2. Put dual aileron servos in it.

Wilder mods;
3. Take at least half of the dihedral out.
4. Cut the Rudder so that's it's vertical to the thrust line and double it's length.

If you really want to get wild;
5. Increase elevator about 1/2 inch.
6. Increase aileron by about 1/8 inch.

Mounting the engine sideways is also a good idea as the exhaust does tend to creep under the cockpit and into the servo area. I put an exhaust extension on mine and it helps but..

The Mid-star though flys fine without ANY mods. I could even knife edge mine with a Super Tiger .40 but it took a LOT of stick to hold it there.

Oh, also toss the Sig easy hinges and get some other brand (I ended up using Great Planes) as the ONLY easy hinges that ever broke on me where Sig's.

Rob, how do you mix in differential aileron and can you give an example of adverse yaw? I've never heard of it before.

Doug, I've been to you website and seen your pictures. Where and how did you put in your aileron servos? Do you have a diagram or picture of it? It looks like you drilled a hole for the servo lead in the inner most 4 ribs.

lnorris, did you want to lose the wingtip's because of it's looks?

****
When I went home at lunch I did find something out. I won't be able to mount the 46 exactly 90 degree's and still be centered on the thrust line. The stock muffler on the TTPro 46 would go through the fuselage. As I see it I have 3 options: 1)use different muffler, 2) mount the engine about 75 degrees or maybe 105 degree's off vertical, or 3) drop the engine 1/2"-1" below the thrust line.

What would happen if the engine was 3/4" below the thrust line?

Striker

There's a picture of mine at "unioncityrc.com" with my mods. Look under the first photo pages. I turned the engine so the exaust was under the plane and used an extension on the stock muffler. It had a Tower 46, BTW I had no problems with that engine, and wheel pants.
If you balance a Mid-Star at the rear most balance point and in crease the deflections a little past the recomended range you will have a plane that will do things that will leave you in awe! It would do a tail over nose flip in level flight and the prettiest flat spin you have ever seen. In fact one of those pretty flat spins was what got the best of her. It went down behind some trees and when I got it stopped it was inverted and I pulled it into the ground! RIP :cry:

I would like to build another soon, I love this plane! I have had 3 of them and all have ended in tragic accidents. Not the fault of the plane I take a lot of chances with this plane because it flys so good! I'll take it over a 4* any day!!!

I would leave off the wingtips to increase the roll rate. I loved the way mine flew but I felt it didn't have enough aileron authority.

Of course that was after really getting used to my Dazzler so take that with a grain of salt...

Oh, and you're other option is to modify the body of the plane around the muffler. Basically indent the body to fit the muffler.

strikerone,

Adverse yaw occurs because the aileron that deflects downward increases both lift and drag on that wing of the airplane. If you feed in left aileron, the right aileron deflects down and the left one up. Drag on an airplane has two major components, drag from the shape of the aircraft and lift induced drag. In straight and level flight, the lift induced drag is the same on both wings of the aircraft. Aileron deflection changes the lift induced drag. It increases it on the right wing (in our left roll example) and reduces it on the left wing. This difference in induced drag creates a yaw force that tends to pull the nose of the aircraft opposite the direction of the roll. Roll left induces a yaw to the right. Hence the term adverse yaw.

Onbe technique to reduce this adverse yaw is to set up the ailerons to have more up deflection than down deflection. This can be dome mechanically. However, with torque rods, you are limited to the off center holes in your servo arms. With independent aileron servos, you can set the differential mechanically by adjusting the position of the output arm and with a radio with mixing, you can fine tune it electronically.

Hope this helps.


Rob

I love my Midstar
I would highly recommend sheeting the leading edge. I have experienced out of trim conditions from one flight to another in the hot summer days. I would also say build it as a Taildragger it behaves very well. I have been flying mine without tips
here's a pic

hey, rcpilotsteve just reminded me of another must-do. Don't use the ny-rod setup that comes with the kit. Replace the rod with solid steel rods. You can run them down the same tube and they don't expand/contract with the temp.

Here is a pix of mine.

And another.

I didn't use the stock rods. I used Sullivan Nylon Gold-n-Rod Semi flex blue. The same for all my ships. I really attributed the out of trim to the Monocoted unsheeted wing.
Over the Winter I'm sheeting it for my son.
Do ya think I'm thinking wrong Do the blue Sulli's cause this to ???

Dunno about the Sullivans. I do know that MY constant re-trim problem was solved when I replaced them with wire. You may be experiencing something different.

That would be a good idea though to sheet it to keep a more consitant airfoil.

I'm gonna do both. Sheet the wing and swap rods

Striker,

I insstalled rails on the ribs and then cut 1/16 inch ply for hatches. The airelon servos are mounted to the hatches. I believe I may have pics of how zI di this at home. I'll check after work and let you know. I tried to e-mail you but couldn't

Striker,

You have it.....

uciflylow,

How did you route your throttle cable with your engine mounted sideways?
Where did you put the battery and Rx?
Did you have to rebalance your midstar laterally?

thanx

Nathan

Guys,

Looking at the plans and kit, how hard do you think it would be to drop the wing down a little more to make it more of a mid-wing design (Kind of like and Edge with with a constant cord wing).?

Marcus

Uciflylow...... what engine did you use? I like the racer look and plan something very close. More info would be great.

Thanks.