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adding 4th seatback piano hinge

cccjbr6

Well Known Member
This is a question from a non-builder. We are about to add the Almost 14 Seatback mod which will allow the seat to recline more, but I also want to add more legroom. Is there any reason structurally or otherwise we cannot add a fourth row of piano hinge to the seat pan on both sides to add another 1.5 inches or so of legroom? I don't know what is under the seat pan that might interfere with that new row of rivets. I would appreciate any thoughts and guidance.
 
I found that the seat belt brackets prevent much more aft movement of the seat hinge point. The additional recline does improve legroom as well. I am 6'4" and have long legs. I have the pedals as far forward as they can go, the 14 mod, plus thin back cushions, I fit great.

That said, there is nothing else to proclude adding another hinge. I bought some of the 20 degree bent triagle anchors to improve seat belt geometry.
 
Adding Hinge

I did it on my 6A. Just on the pilot side. Also did the almost a 14 kit. Seatbelt attach points are very close. You may need to change the attach brackets on the belts. Or, you could just go 1 inch instead of the 1 1/2 that would even space the 4 row. So far no adverse effects. W&B still within envelope.
 
Easily done but, as mentioned above, the seat belts are the limiting factor. I gained about 1.5" in my -7A with Crow harnesses.
 
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