[yankee-flyer]

Tensioned the stab cables today and like everyone else, we found that at about 20 pounds tension the f-1203A bulkhead bent backwards amost 1/4 inch. The only way to achieve 35-45 pounds tension was to have the cover plate installed while the cables were tensioned. It seems that every time the cover plate is removed, (DAR inspection, condition inspection, etc) that bulkhead will deflect as soon as the screws are released and I wonder if the angle will be great enough to be able to get it back again without releasing the cable tension, then doing it all over again when the inspection is completed. What have you guys who have already had your airplanes inspected found to happen when you removed that angled cover plate under your thighs?

Wayne 120241

 

[Geico266]

Wayne, I think some thing is not right. Nothing on mine bends 1/4" and I have had mine on and off several times. All holes line up fine.

How I tensioned my cables was using the other part of the instructions that said if you don't have a tensiometer use the other method and tighten the cables until they do not slap around in the tail. After talking to other builders who used the tensiometer 3-4 threads showing in each ends of the turn buckle. I just set it to that and it's been good ever since. Another way to check it is to look at the pullies. The cable should not make marks in the groove / material of the pulley, and you should be able to turn the pully by hand with some a little effort.

I would check the routing of the cables if something is bending.

JHMO.

 

[Mich48041]

Wayne,
If you loosen the turnbuckles completely, then pull aft on the F-1203A under-thigh bulkhead with your fingers, you will see that it does not take much force to bend the bulkhead. The bulkhead obviously needs to be reinforced. The cover does that. Our concern is damaging the bulkhead by bending it every time the cover is removed. Another concern is getting the holes lined up to re-install the cover. If the bulkhead is not bent too much, then installing the screws first on the forward vertical surface of the cover should pull the bulkhead back into position. After my plane is inspected, I intend to reinforce the F-1203A bulkhead on the forward side with an angle made out of AA6-063 x 3/4 x 3/4 about 6 inches long to span the distance between the two ribs. If you will look at the forward side of F-1203A bulkhead, notice the 4 uppermost LP4-3 rivets. Two of them go through the control stick bearing bracket. My plan is to drill out those 4 rivets and rivet the angle reinforcement in place. There are already reinforcements on the outboard ends of the bulkhead. Another one should not present a problem. My attached pictures show that the cable tension is slightly above maximum with the thigh cover installed and is below minimum with the cover removed. And with the cover removed, the bulkhead is pulled aft a little over 1/32". Since yours is pulled back 1/4", perhaps your tensiometer is not calibrated. The way to do that is to hang a known weight on a 1/8" cable and measure the tension. If you do not have an accurate calibration weight, a 5 gallon container of water weighs about 45 pounds (8.34 lbs per gallon plus container).
http://public.bay.livefilestore.com/y1ptv6KDLlHTsHF9sOAC8NKtkeNDY8ViTpj_BnTKjCH9WJsE4icmXeq9l5tCGZVWzN5f46TGiH5gB3Jtb9fzmHyvA/DSCN4040.JPG
Now I have a problem. Even with the cable tension set at maximum, one turnbuckle has three threads showing and the other one has 6 threads showing. What should I do about that? I believe one of the cables is too short by 5/16". If I tighten the turnbuckle another 3 turns, it will over stress the control system.
Joe

 

[rvbuilder2002]

I think a plans revision is in the works to clarify the cable tensioning process.

The seat pan should be in place when doing the tensioning adjustments. If it is not, the cable tension will get even higher when you install the seat pan and remove any deflection in the bulkhead.

I have no problem reinstalling the seat pan with the cable tensioned. I insert a tapered punch in one of the screw holes common to the control column bracket and then install the other three screws.

I see your photos but I agree with Larry. A 1/4" movement sounds excessive.

I suggest you set it for a bit over 30 lbs with the cover on and see how it looks. The stick travel should feel very smooth and low in friction. If it is not, either the cables are too tight or you have friction in the control column pivot bearings (because of pre-load on the bearings from less than optimal shimming), or both.

 

[Mich48041]

Stabilator cable is too short

One of my control cables is too short. With the cable tension set above the maximum of 45 pounds using a calibrated tensiometer, the stabilator works smoothly with no binding or friction. The problem is that there are 6 threads showing on the turnbuckle. The plans specify that not more than 3 threads show. My concern is that the threaded end of the control cable will break at the turnbuckle if not enough threads are engaged. Does anyone else have this problem of too many threads exposed?
Joe