Tricycle main gear location from CG

[Dennis Toth]

Guys,
Is there a general location for the main gear back from the CG for stunt? I have built several different ships with tricycle gear and always just had the nose up just a few degrees which got them off the ground OK. Was just wondering if there is a better position that give good take-off and stable landings.

Best,          DennisT

[Crist Rigotti]

On my Thundervolt, the main gear was about 1 inch aft of the CG.  The nose gear length was adjusted to have a zero degrees to the ground.  The plane would tip on its tail with no battery installed.

[Tim Wescott]

Ted Fancher recommends that you project a line down from the CG point, 15 degrees back from vertical, and locate your LG such that the point where the wheels touch is the point where your sloped CG line meets level (damn that's not stated well -- I'll be smarter after the caffeine has a chance to work).

It's basically the same rule for conventional gear, only then you want to be 15 degrees in front of the CG.

I've only built one trike gear plane, but I just used that rule and it works a treat.  I think it's less important with a stunter than with other planes because if the plane is trimmed well then you're taking off level, with the flaps just helping you rise off the ground.

[Dennis Toth]

Tim,
Thanks for the info, any difference in angle for grass fields?

Best,    DennisT

[Jim Thomerson]

I asked Bob Palmer about this.  He told me the leading edge of the wing should sit 1/8 inch below level.  I set up an airplane this way, and it took off and landed on grass just fine. I think having the nose slightly down is a good thing. 

[Trostle]

I will add a bit here, but most of what has been said is good information.   A position of the gear about 15 degrees aft of the vertical CG works.  Netzeband showed this several times as well as a position 10 degrees aft.  On a stunt ship, the 10 degree aft position will give a bit softer landings.  

On a stunt ship, it makes sense to adjust the nose gear length so that there is no positive angle of attack or to have even a slightly negative angle of attack when rolling on the ground.  The airplane will have less tendency to jump off of the ground on the takeoff as in it is easier to hold on the ground and get a smooth liftoff.  

Just some thoughts based on some experience with trike gear.

Keith

[Tim Wescott]

Dennis, I'm certainly not the World Expert on this topic, or just about anything else control line related, but I'm pretty sure the answer is no.  With conventional gear you're finding a compromise between nosing over on landing, and bouncing on landing.  Grass tends to pull you into a nose-over, so you put the gear farther forward.

With trike gear, you don't have that problem, unless your front wheel is too far back.  If there is a consideration with grass fields and trike gear, it's that the nose gear takes a beating, and will take more of a beating if you're flying off of grass.  My current ride has trike gear, and about ever half a dozen flights I need to bend the nose gear forward.

[MikeyPratt]

Ted Fancher recommends that you project a line down from the CG point, 15 degrees back from vertical, and locate your LG such that the point where the wheels touch is the point where your sloped CG line meets level (damn that's not stated well -- I'll be smarter after the caffeine has a chance to work).

It's basically the same rule for conventional gear, only then you want to be 15 degrees in front of the CG.

I've only built one trike gear plane, but I just used that rule and it works a treat.  I think it's less important with a stunter than with other planes because if the plane is trimmed well then you're taking off level, with the flaps just helping you rise off the ground.
[/quote

Dennis,
Ted is spot on with this advice.  I've designed many C/L & R/C models and this works perfectly.

Later,
Mikey