Trim Assist Kit Option

[Av8r3400]

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.

I put in a gated flap control since I added a trim tab to the elevator...




So, In theory, this should work on the way I have my IV set up.

[jrevens]

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.

ofergd,

Are you disregarding the relatively heavy ,unbalanced elevator, on the newer models especially, and the effect of gravity that pulls the elevator down, which must be overcome by aerodynamic forces, causing additional drag? Ideally, I would think that the spring could eliminate or diminish at least some of that additional drag. I think that the spring probably doesn't necessarily "pull the elevator up from it's trimmed position", but locates it in a more trimmed position to begin with. My understanding is that the spring should actually bring the elevator to the streamlined position on the ground, overcoming that "gravity droop", for lack of a better term. I'm certainly no aerodynamicist, and I'd welcome discussion of the "issue". Of course if you fly inverted it might not be so desirable.

The elevator is really quite "heavy" on the ground... it reminds me a little of a Skybolt I flew once. It took so much force to level the elevator when standing still without the engine running that I thought something was wrong. Of course I was used to flying many hours in my Thorp, which has a wonderfully light and balanced stabilator.

[ofergd]

You are probably right. the weight of the elevator does increase drag.
But that is only the Shape Drag. For cruise speed you can win some speed with the spring system.
In slow flight, the main drag component is the induced drag. The induced drag does not change because it depends on the total drag that the horizontal stab and elevator create.
In my plane the problem is not having enough trim when the flaps are down. It's a short time in the overall flight so the effect will be minimal if not installing the kit.
I have a classic IV.

[jdmcbean]

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

Absolutely!

[jrevens]

Thank you, John. BTW, installing the spring was no big deal... I made a hook out of a piece of piano wire and stretched it right on there. Don’t know why I thought it might be more difficult.

[Flybyjim]

What model Kitfox were you flying when this happened?

[Frontier Fox]

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Help TKF. I had a little time today to take care of some odds and ends. I adjusted the trim actuator and followed the procedure for setting up the elevator push/pull tubes. Went ahead and bonded the trim position sensor bracket also. Hey so far so good.
I thought I would install the Trim Assist Kit but ran into a snag.
The bracket that was in the Trim Assist Kit looks nothing like what is pictured in the instructions. The half round part on the bracket that I have does not fit the curvature of the bellcrank and I see no way to attach the spring.
Did I get the wrong part in the kit? Am I missing something?

[Esser]

Wrong part. I had that one sent to me too

[Frontier Fox]

Thank you Esser. That’s what I was thinking, glad someone could confirm. Looks like an email to KF is in order. Do you happen to know what that part is for?

[efwd]

I can't recall where you are at in your build but thought you could use the advice that John McBean gave me. Do all the flight control rigging without this connected. After rigging is complete throw the spring on. He says it just complicates the rigging process.