Seat pan rubbing on control linkage

[Jerrytex]

I just recently bought a Classic 4 KF that was wrecked then rebuilt by a aircraft mechanic. Might have seen it on Barnstormers. Anyway, it was real close to being completed when the builder passed away. The builder's son sold it to me and I am diving it to finish it. Already ran into my first snarl and need advice. I went to put the seat pan in to get the "sitting in the cockpit of your new project picture", and I noticed that the seat pan totally restricts the movement of the control linkages both from the flap control linkage and the aileron contol linkage. In looking at the bottom of the seat pan, I can see where the flap control linkage has been rubbing but I don't see any rub marks from the aileron linkage. The linkage is actually holding the seat up probably 1/2". When you sit in the seat, you cannot move the control stick at all. I searched this site for an answer and didn't find my exact scenario. I read on another site that you have to bend this linkage to clear the pan. It is obvious that all this linkage has been replaced so I can't tell if the original was bent or not. The book doesn't say anything about it either. Just wanted to get a second opinion before I go bending on things. Thanks.

[HighWing]

Jerry,

I just measured mine and both flaps tube and aileron tube are bent about an inch total measuring with a straight edge along the length. This is my second Model IV and the first was bent as well.

Lowell

[Cwehner]

I'm finishing up my Kitfox IV. Heres a picture that might help ya out.


Chris Wehner
Tulsa Ok
Kitfox IV, 912UL

[CDE2FLY]

Jerry - A couple of thought on this:

1. Make sure the control rod "bends" are such that the rods are as low as possible (i.e., against the bottom fabric). The rods can be rotated into various positions and fixed in position with the jam nuts against the rod ends.

2. On my Model 7, I fabrcated several "slings" using perforated metal pipe hanging strap available at Lowes/Home Depot. It's 1/2 in or so wide and comes on a roll. Simply loop the strapping material over the structural tubing the seat pan rests on (front and back) and secure the loops with AN hardware. This will ensure that the seat pan does not shift down in the future and jam the controls.

3. Be sure to tie wrap the seat pan to the the structural tubing per the plans to be sure the seat does not slip off teh structural stub supporting it.

Hope this helps,

Chris

[cap01]

if the seat pan isnt secured properly , it will slip off the front cross tube and will jam up the controls . i had it happen during some taxi tests . ive installed adel camps on the fwd cross tube with clip nuts and installed screws thru the fiberglass along with tywraps at the back . also used a 2 inch web strap fore and aft under the pilots seat to keep it from jamming the controls incase it does slip off for some reason .

[Jerrytex]

So bending the rods it is! Thanks for all the info. I think I am going to use nylon webbing for supports under the pan to keep it from falling down on to the linkage. Boat winch straps are pretty thin and very strong. This will be in addition to the zip ties or metal clamps to hold the edges of the pan to the support tubes.

On a side note, does anyone else have dumb things happen to them while working on their plane? I manged to poke a small hole in the bottom of the fuselage fabric by accidently dropping a razor knife. My jaw dropped when it happened. It is a small slit but still, it messed up a beautiful finish and ruined my day. Thank god it was on the bottom of the fuselage so you really can't see it. Any pointers on fixing it. I put tape over it.

[catz631]

I have storage lockers in my seat pan(one on each side)Bought them from Merle Williams. These are also suppose to keep you from blocking the controls if the seat breaks.
Dick Maddux

[DanB]

Jerry,
I feel your pain...Take a little time to clean the area with MEK taking it down to the fabric or the polybrush. I picture an oversized round patch placed inside and out after your PolyBrush. Go through your painting steps and use a small touch up sprayer or an air brush. You will be the only one that could point it out.

[cap01]

for the time i was completing the construction i kept the belly covered under the seat pan to protect it from things i dropped . but things happen and i punched one hole with a screwdriver and another was already in it when i acquired the kit , the fuselage and wings were already covered . its easy patching from the inside , patching from the outside is the difficult repair . having to disturb and replace the paint is more of a challenge

[HighWing]

A couple of notes:

The repair from the inside sounds like the fix to me. Be cafeful, though if your final finish is aerothane. The solvents in the adhesive won't pass the aerothane, but can cause it to bubble. I think I would use polybrush for the fix. In fact, I did a fix over aerothane once and used the structural adhesive that came with the kit to avoid a previous experience with the bubbling.

Also, the seat pan failures - dropping in the controls - is pretty much confined to the later models where they shortened the forward lip of the seat to accommodate the cover over the control stick cross tube assembly. The IV and previous designs have a pronounced lip, and unless you tend to land awfully hard and are a big guy, I think the straps can be eliminated. I plan no straps on my IV and I know of at least one owner who doesn't even use the tiewraps for easy access to that area - many hundreds of hours with lots of dirt and grass landings. I don't recommend that, but doing what may be necessary on a Series six to a Model IV might be a bit of overkill. I had 900 hours on my first IV with no pan issues with only tiewraps every three inches or so.

Lowell

[DanB]

Yep, I agree w/ Lowell if the finish is aerothane. Polytone would not be too much trouble and should match easy. An inside patch would likely do fine if teh puncture was clean. Just my 2.5 cents

[Jerrytex]

The cut is very clean. The paint is aerothane. So with an inside patch, do I just cut a small piece of fabric and use structural adhesive (Hysol) to cover the cut and hold the patch in place? I guess on the outside I could use a piece of good quality clear tape? It is such a clean cut that this would make it almost invisible since the tape is clear.

[cap01]

dont think you want to use structural adheasive . even thou its aerothane , they would of used poly brush/ poly spray under it . the fabric guru on the field calls them dollar patchs . a piece of fabric cut and pinked in a circle about the size of a silver dollar or what ever it takes to cover the hole with a descent edge distance . on the inside i cleaned the area to be patched with mek and stuck the patch down with a mix of poly tack and poly brush . works good , drys fast and your done in 5 minutes

[HighWing]

One more thought on the structural adhesive fix. I have done it both ways, and the first try with polytac didn't work well for me - lots of distortion in the Aerothane finish, though it was not a simple cut, but a more complex repair - pulled seam on the lift strut fairing. The slow cure of the structural adhesive, gives a chance to manipulate the repair. The last time I did it was on a friends Model IV and we cut a couple of flat pieces of aluminum and covered them with vinyl sheet for a release and positioned them over the patch with a couple of strong magnets holding them to clamp the repair. It was on the side of the airplane behind the lift strut and the repair was flat and virtually invisible. To each his own though.

Lowell

[Breathless]

My control rods rub on the seat pan, my fix was to remove the area on the pan and change the conture of the hump to alaw enough clerance, and repair the fiberglass.

Jim H.

[t j]

I'm pretty sure my classic 4 builders manual says to bend the control rods if the seat interferes with them.

[Jerrytex]

I checked the manual that came with the plane and I might have overlooked it. It is a 1992 manual so the pics are not that great and is overall getting pretty salty. I have bent the rods and seat clears but with my big butt and another person in the seat I can still feel a little bit of resistance so I may make one more adjustment. There is a crack in the middle of the seat pan and another on one side so I think I will fix those to take the flex out of the pan. If it still rubs after that, I will add the nylon straps to help suspend the pan above the rods.

[Dorsal]

For what it is worth I put a small piece of wood next to the control rod such that if the pan let go it would sit on the wood not the rod. This is on a 7.

It's not very fancy but it will do the trick (held on by two dabs of Hysol).