Trim Assist Kit Option

[n85ae]

I think the heavier nose IO-240 is a different airplane. With 22 degrees
flaperon you cannot trim out the back pressure, the spring just fools
you. I only jumped in to share my thoughts, likely with a Rotax there's
no problem ...

Jeff

[jrevens]

You may be right, Jeff. If you are flying with the CG closer to the forward limit than is usual for the lighter engines, then there is more downward force necessary from the tail assembly to trim the airplane. Since the tail is more heavily loaded to maintain that needed force, and at a higher angle of attack to do that, it seems it would be closer and more vulnerable to stalling for whatever reason.

[jiott]

I have enjoyed this discussion, have learned some things.
FWIW, my SS7 with Rotax 912, I cannot trim out all the backpressure even with the spring assist and 22 degrees (full) flaps. Half flaps no problem. As I mentioned on another thread, I screwed in my ballscrew rod eye so my horizontal stab goes all the way to the bottom of the slot in full nose up trim. This gets me close but not all the way to trim out full flap back pressure.

[Floog]

Do wheel landings. Then you won't have to pull so hard

[jrevens]

Any tips for stretching the spring to install it? It looks like a pretty hefty spring and a pretty good stretch. Also, what position are most using - the greater, or lesser distance between holes?

[ken nougaret]

I think i used a heavy duty tie-wrap to assist in pulling on the spring.

[bumsteer]

Hi John

Not familiar with the system (yet) so not sure what your dealing with but you could try what we use in gunsmithing. Take a cheap screwdriver and using a cutoff wheel in a Dremel tool cut a V or U notch in the blade and use it on the hook of the spring.

Rick

[jrevens]

One more question, for the Kitfox Aircraft crew... does the new Speedster that Kyle Franklin flew have the spring trim assist?

[ofergd]

Would this work on a IV? If not, why not. Same mixer and linkages as a 5-SS, right?

I think the difference is in the flaps operating handle. In the IV it is held by friction and in the others it is locked in different designated positions.
If the friction is not enough, the flaps will be lowered when pulling the stick.
If you can have a locking mechanism for the flaps, you probably can install it on the IV.

[ofergd]

Jeff brought up a point that got me thinking; when you trim the horizontal stab for hands off straight and level cruise flight with the spring assist what you are really doing is trimming for a constant back pressure equal to the spring force. Seems like this would add some drag to your cruise efficiency. I realize that the spring pressure is small with flaps up (the mixer system adds more spring back pressure as you add flaps, which is when you need it) but with flaps up there is still some spring pressure.

I disagree.
Well, it depends. If you have the full horizontal stab trim, you might be actually adding some drag. The spring pulls the elevator up from its' trimmed position and to compensate for that, you trim the stab down (leading edge up). this change of angle from the trimmed position might add a little drag.
BUT, if you have the small trim tab on the elevator, like I have, the spring reduces the required angle of the trim tab, and this reduces the drag.