Trim system

Building a Wag Aero (PA-11), and I would like to know how to set-up the spring tension on the trim system. I bought the proper spring, pulley and support from Univair but I need some indication for the initial installation like, with full nose up trim, where should the elevator be without touching the control stick.

I realize that this trim is not mandatory on amateur built, but for certified PA-11 with EDO 1400, 90 hp.

Thank you in advance.

GDKL

do you mean the trim indicator or how to load the trim pulley cable spring? or do you mean the bungee spring ? Need just a little more info.

I mean the bungee spring to lessen the back pressure on stick when on final and full nose trim up. This cable and spring is connected above the elevator cable and through a pulley and spring to the trim yoke.

I hope this is enough info to figure out when I mean.

Thank you..GDKL

If you get an answer, I hope it addresses why the bungee is there in the first place. The J3 has no such system, and it is a delight to fly. Some PA-18s cannot be flown in the pattern without extensive trim changes, while others are almost as easy as the J3. I understand the difference is whether the bungee system is weak to non-existent, or very tight. I cannot imagine that the PA 11 is so different from the J3 that it needs a bungee for safe flight.

If you bought the parts from Univair what you have is fixed because the attached in defined places on the plans. The spring is X , the Cable is X, the place where they both attach is defined. There is no adjusting anything except making your own cable. Is that the question? The cable length.?

Are you needing the set up? Did you get the pulley horns for the pulley? Then the cable attaches to the jack screw assy.,then the cable to the elevator horn. The SUpercub plans show this perfectly. Do you need help finding the reference?

Bob, I like the bungee, some don't. It's a little assistance. The lower bungee was done away with sometime ago. Mark Drath wrote an article on it some time back in CUB CLUES. You don't need the upper but it does help in my opinion. Adds a little back pressure when trimming nose up. Works pretty good on the 12 as well.

trim system

The length of the cable from the yoke clamps to the spring is what I need since the spring will attach on the elevator bellcrank added bracket.

Thanks

Though I haven't measures exactly, I recall on my 12 that the Elevator is deflected up three quarters of it's full travel at full trim back. Placing a straight edge on the bottom of the HS,the trailing edge of the elevator is up four to six inches from the straight edge at full trim up. I try to check exactly today. This at least gives some reference. It's definitely up past level.

Some of us have replaced our yoke/pulley/jackscrew system with the Dakota Cub system. On my -11 the Dakota pulley is larger than the Piper Pulley that was on the jackscrew. Keep that in mind when figuring the length of the cable.

As an aside, the Dakota Cub system is superb and a significant improvement over the stock system.

trim system

Thank you Fortysix12. These info. are what I need to set the the spring tension for the initial set-up. With turnbuckles, I will leave some room for final ajustment.

GDKL

....I cannot imagine that the PA 11 is so different from the J3 that it needs a bungee for safe flight.

It's not dangerous, but try flying your 11 with and without the bungees. It makes a difference in comfort level when loaded forward.
JimC

Maybe that's it. The J3 is rarely loaded forward. My first solo was from the front seat, but I probably didn't notice any problems because my mind was on getting back safely. My Cub will go for hours without stick input of any kind.

I had a chance to measure my trim bungee influence on the elevator in the full nose up position and it is not what I thought. It may of been above the HS when it was new but it now only holds the elevator to within 2 inches of level with the horizontal stab. It is below not above. I placed a straight edge and took the measure.

Check this out - look almost to the bottom for Cub 90's informative post.

http://www.j3-cub.com/smf/index.php?topic=2342.0

trim system

Thank you all for your comments. Great help.

GDKL