Bigger wheels or smaller prop?
 

Need some help here guys. I've got an Avistar. I think the prop MAY be too big. I keep hitting grass at the field when I land or when I am starting. We keep the grass pretty short so that's not the problem. I'm running the stock wheels and an 11X6 prop. Not sure of the wheel size. Any help would be appreciated.

Thanks

RE: Bigger wheels or smaller prop?
 

Well, you could go with a 10x6 prop. Bigger wheels will also help a lot and make it easier to taxi.
Just be sure to re-check the CG if you go with larger wheels.

RE: Bigger wheels or smaller prop?
 

If it is only hitting the grass and not the ground it shouldn't hurt anything besides turning your prop green.

RE: Bigger wheels or smaller prop?
 

I would do neither... I would raise the height of the plane by an inch via landing gear. I purchased a new longer nose landing gear rod for $2 and bent the mains downward and anchored wire to wheel collars to keep them from flexing back outward. My LT-40 sits an inch higher than all others at the field. I wouldn't waste money on new wheels.
http://www.x-plane.org/users/hercdoc/DSC00039.jpg

http://www.x-plane.org/users/hercdoc/DSC00040.jpg

RE: Bigger wheels or smaller prop?
 

I used the Avistar with 11x6 prop.. And had no problems.. But
we have pavement.. If the grass is kept short, it should be no
problem if your just lightly touching the tops of the grass??
Do you have the nose wheel strut adjusted as far down as
possible? If not and you do readjust it make sure the mains
keep the plane at least level as it sits.

RE: Bigger wheels or smaller prop?
 

Over time or with a hard landing or two the landing gear will bend. Check to see if the nosegear is bent backwards a little. If so, bend it forward. It should be perpendicular to the ground. You can make the mains a little taller by bending the legs together some too.

RE: Bigger wheels or smaller prop?
 

Thanks all. I'll try the bending of the landing gear and try to lower (raise) the nosegear also.

RE: Bigger wheels or smaller prop?
 

I know what you mean about cutting grass,i did and using a wooden prop it was taking small slivers out,i went to a Dubro for the front wheel assembly,it's longer and cured my problem.

RE: Bigger wheels or smaller prop?
 

Start taxiing and taking off like it was a taildragger...with full up elevator until the plane is close to lift off speeds, then neutralize it. I do that with a Xtra Easy 2 and 11" prop. I taxi with full up elevator all the time and still cut a little grass. It doesn't hurt anything if I'm careful.

Also, maybe you should think of a new main gear asemblly. They are under $10 at the LHS. Glue pine blocks inside the fuselage and tap 1/4 x 20 nylon bolts. The gear won't bend easily and will shear the bolts if you hit hard, saving the plane. Someone at your club should be able to talk you thru it.

RE: Bigger wheels or smaller prop?
 

Gotta watch the Avistar's stance on the ground, though, should be level or even slightly nose down. Nose up and you'll bounce landings forever.....


Andy

RE: Bigger wheels or smaller prop?
 

I would replace the wheels with 3" light weight wheels. This size is the standard for our grass field. The larger wheels will also give you better ground handlying in the grass. Other than that there isn't a whole bunch that you can do. [8D]

RE: Bigger wheels or smaller prop?
 

The foam 3" wheels are great on grass. I went to those. They save a lot of weight too.

RE: Bigger wheels or smaller prop?
 

Look at the pictures in HerDoc's post. Simplest and best answer. Not a lot of work involved and it's almost fool proof.

RE: Bigger wheels or smaller prop?
 

You could bend the main gear apart, and leave the front alone, and it will raise the nose, but lower the tail. Be careful about the tail being too close ot hte ground

RE: Bigger wheels or smaller prop?
 

An altogether better fix is to convert the Avistar to a taildragger -- it is an easy mod & the problem goes away -- the plane also flies better as a taildragger, due to lowered weight & drag.

RE: Bigger wheels or smaller prop?
 

Bigger wheels will help, but I have a question on the prop size/engine combo? If this is a .40 size, perhaps a lower pitch will help. If it is a BB 46 size I have found 11X6 APC great. If it is a bushed engine, most perform best with 10X6.

RE: Bigger wheels or smaller prop?
 

I removed 3 wheel collars and put on the foam wheels. The weight of the rubber wheels and collars was almost equal to the battery pack, so it does help. I put fuel tubing behind the wheels instead of collars.

A guy at the field was using fuel tubing on the outside to hold his wheels, but I saw him lose both main gear wheels last weekend on a bouncing landing. The plane was a Jungmeister and flipped upside down, but nothing was damaged. I prompty gave up his idea of using fuel tubing on both sides.

RE: Bigger wheels or smaller prop?
 

The engine is a 46fx with an 11X6 prop. I was told I can get away with 10.5X6. I may try the new prop and new 3" wheels.

I don't want to try a taildragger just yet. Just soloed last week. However in the future I may just try it.

RE: Bigger wheels or smaller prop?
 

on my eagle II, i used T.T PRO 46 with 11/6 or 10/7 and the weels go to 3" because i land on grass.
3" or 2" don´t have problem with the CG, for me is better 3"

Sergio

RE: Bigger wheels or smaller prop?
 

Wwnt to the LHS and talked to the people there. Explained what was happening and went with a 10X8 prop first. We'll see how it works out and then if needed we'll try the 3" wheels.

RE: Bigger wheels or smaller prop?
 

Be prepared for your plane to fly much faster with that 10x8 prop. I think a 10x6 would be a better choice.

RE: Bigger wheels or smaller prop?
 

YOU FLY MUCH FASTER IF YUO OPEN YOUR TROTEL..............

use 10/7 or 11/6

with 11/6 my TT pro 46 lives for 7 years.

Sergio

RE: Bigger wheels or smaller prop?
 

Went with the 10X8 according to the LHS it would put more of a load on the motor and therefore wouldn't rev too high. He figures I'll pick up about 1-200 rpm. I normally fly at 3/4 or less throttle anyway. Haven't built up enough confidence to go WOT for extended periods......yet.

RE: Bigger wheels or smaller prop?
 

An 11 x 6 prop and 3 inch wheels are the simplest answer for a .46 powered trainer flying off grass. Works every time.

RE: Bigger wheels or smaller prop?
 

GJAUBIN,
What you need to understand is that a prop with an 8" pitch will fly the plane faster at any given throttle setting as compared to the 6" pitch that you had previously. Pitch designates how many inches forward the plane will move with one revolution of the prop. 8" pitch is not the best choice for your trainer, it will bog the engine down forcing you to give it more throttle which in turn will fly the plane faster than it should. Go with a 10x6 and run the engine a little on the rich side.