Grrr. Trim Tab (hinge) issues!

[SteelMike]

Hey guys, Guess what? I'm on my first trim tab! I think it's going to be fine, too (I made riblets - way too easy. What's with the bends? I didn't even try).

Anyway, I aligned the hinge per the plans - at least I think - and drilled them. When I disassembled the hinge, I realized that the holes are too close to the edge (?). What's the story? Did anyone else have this problem? Did I align it incorrectly, and if so how are you supposed to align it?

[Rupester]

Don't know what to tell ya. I didn't have that problem, but I also spent a ton of time clamping, measuring, marking, double checking, remarking etc. The trouble is there is not a lot of detail given in the 'structions about aligning the trim tab hinge.

[joeboisselle]

Personally, I think it'll fly.

[SteelMike]

Yeah, there's very little in the way of instructions here. I think it says to keep one end 3/8" from the center of the most outboard hole - but that's a lateral measurement (i.e. left or right down the length of the hinge), not forward and back. There's really no forward and back measurement given on the plans, at least as far as I can tell (can someone confirm this?) except that it looks to be flush with the hinge pin. That's how I set it up, did anyone do differently??

Thanks for reading,

MB

[DickDe]

Mike...

Too bad your hinge didn't turn out as you expected but that is the result of not knowing where you were drilling before actually drilling the hole. The technique to use is to draw a line on the undrilled part, the hinge in this case, where you want the holes to be using proper edge distance criteria. Put the assembly together and observe the line in the prepunched hole before you drill the hole so you know you will have edge distance before drilling.

As it stands right now to recover from this error is to find a way to get proper edge distance. The way I see it is you have some choices.

1. Move the hinge one eyelet distance right or left so new holes could be properly located... i.e. new holes 3 diameters from the incorrect holes previously drilled while maintaining 2D from all other edges.

2. Keep the hinge in the location you have selected but drill properly located holes between each existing hole doubling the rivets used. This would make the joint stronger than the designed strength but the rivet line would appear staggered. The only negative is driving the improper rivets could crack out the edge of the hinge because that is the reason for the 2D edge requirement however hinge stock is pretty soft so I don't think that would happen.

3. Replace the hinge with new hinge and redrill with proper spacing.

Another hint. Before riveting hinge material, always put the hinge pin in the hinge before you rivet. If you squeeze or drive a rivet and hit one of the eyelets it could bend the eyelet slightly putting a bind in your hinge or make it very difficult insert the pin later. The pin being in the eyelets will tend to support the eyelets and keep them aligned because once bent it is really tough to bend them back into alignment.

Dick DeCramer
RV6 N500DD flying
RV8 wings completed
Northfield, MN

[SteelMike]

Good tips - thanks.

I think I'll probably just replace the hinge, as annoying as that may be. Question, though: when you look at the plans, it looks like the hinge pin should be flush with the edge of the elevator skin. If I do as you said and draw the line where there is proper edge distance, that will make the hinge sit too far aft, and in any case, won't look like the plans... As mentioned earlier, the plans more or less stink in this area.

Should I just get the proper edge distance set, the forward/aft distance of the hinge be damned?

[Bob Ellis]

Mike

I agree with Dick about drawing a line along the hinge. If you see this entry in my log I have included some photos of where I believe the problem lies. Picture paints a thousand words.

Bob Ellis
www.rv-8.co.uk
Fuselage kit arrives next week

[smokyray]

Nice carpet...

[n2prise]

Van's offers hinges with a wider flange. We had to get a set of them to install the flaps on an RV-8 quickbuild. The alignment of the flap trailing edges worked perfectly with the ailerons using wider hinges. Only one hinge was needed. The original hinge was mounted to the wing. The new wider hinge was taken apart, with one piece fitted to each flap.

[jmartinez443]

Mike,

The standard (P3) hinges should work. Here's what I did for what it's worth: http://www.rv8alog.com/empennage/elevators/Left/e9.htm