Small Cub Thrustline

[Leniuk]

I have a quick question regarding thrustline. Everyone talks about the thrustline mod on the supercub, but how about the little cubs, specifically the wag aero sport trainer?? I believe this fuselage has the same thrustline as the J-3 which has no thrustline issue. Is that correct?? Does the factory PA-11 have a different angle than the factory J-3 and therefore would benefit from the thrustline mod?? Has anyone done this mod on the small cubs, the PA-11 or the PA-18-95?? Info greatly appreciated. Plan on building the sport trainer like a factory PA-11, closed cowl, 0-200, etc. Just wondering about Thrustline issues.

 

[gbflyer]

From previous conversations, I recall that the J3 is 0 degrees and the PA11 is 3 or 4 degrees down. I don't know of a legal option to change a certified PA11 to 0, but of course that's a non - issue for your experimental. I have it on good authority that it really helps a PA11 style airplane to change it to 0 degrees.

gb

 

[Roger Peterson]

If I member correctly, the 11 sits 4" lower for better visibility over the cowl, than a 3 and has a 4 deg look down angle. If you put a 0 deg mount on it, your visibility is almost as bad as the 3 was. You can't get the dang thing to fly like a fast plane regardless what you do so I don't think it matters much what angle you put the motor at. I tried both and couldn't tell any difference.

 

[willyb]

The specs call for 4 degrees down on the PA-11 but if you measure one after the rubber cushions take a set you will see 5-51/2 down.Changing mine to 0 made a big difference.I picked up a solid 4mph in cruise.The plane handles better all around.It is perfectly rigged and wing angle of incidence is where it belongs which is critical for it to work.I am fairly tall and vis over the nose was no issue.

Bill

 

[Jerry Burr]

Thrustline

Hi Willy B. Do you have flaps on your -11? Thanks. Jerry B.

 

[Leniuk]

I have one more question that may sound stupid, but here it goes. Comparing the J-3 to the PA-11 that apparently have a different thrust line, was the difference in the thrust-line between the two airplanes built into the fuselage or just the engine mount?? When I look at the piper drawings for the J-3 and PA-11 fuselages I don't see any differences. Firewall is parallel to datum line and top of engine mount bolt is 1.5 inches below datum line. So therefore, is the difference all in the mount?? If this is the case I just need to make sure I buy a J-3 mount for my experimental PA-11??

 

[S2D]

Unless a guy is using his 11 for some extreme stuff, its hard to beat the visibility over the nose. Flew one the other day for the first time in ages. felt like I was in a helicopter with all that visibility out front, compared to my supercub.

 

[behindpropellers]

I have one more question that may sound stupid, but here it goes. Comparing the J-3 to the PA-11 that apparently have a different thrust line, was the difference in the thrust-line between the two airplanes built into the fuselage or just the engine mount?? When I look at the piper drawings for the J-3 and PA-11 fuselages I don't see any differences. Firewall is parallel to datum line and top of engine mount bolt is 1.5 inches below datum line. So therefore, is the difference all in the mount?? If this is the case I just need to make sure I buy a J-3 mount for my experimental PA-11??

Correct, it is the mount.