[Av8torTom]

Hello again,

I'm preparing to rivet the center fuselage. Did you dimple or machine countersink the 705A bulkhead flange where the bottom skin is riveted... and where the side skins attach too for that matter?

Thanks,

Tom

 

[airguy]

Hello again,

I'm preparing to rivet the center fuselage. Did you dimple or machine countersink the 705A bulkhead flange where the bottom skin is riveted... and where the side skins attach too for that matter?

Thanks,

Tom

I dimpled the skin and countersunk the 705A, the material thickness of the 705A will cause it to distort if you dimple it.

 

[Av8torTom]

Bueno

Thanks Greg. How about the vertical sections of the 705 bulkhead, can't recall if they are the same thickness?

 

[longranger]

I generally dimple 0.040 and under (wing rear spar for example), and countersink 0.050 and up, unless otherwise directed (like where the forward floor stiffeners intersect the forward half of the 704 bulkhead).

 

[Av8torTom]

Thanks Miles

 

[airguy]

Thanks Greg. How about the vertical sections of the 705 bulkhead, can't recall if they are the same thickness?

I believe they are - I know that I did the same on the vertical as the horizontal portions. There is no real hard line between countersink and dimple - you can countersink material as thin as .025" if you are extremely careful about it, but it's not really a good idea as the material gets quite thin and is likely to crack. Likewise you can dimple material past .040", but again if you get too thick you'll have trouble with distortion. I did some sample dimples on .063 and about 2/3 of them were distorted badly enough I would not have used them on the airplane. As Miles said, somewhere between .032 and .040 generally is the dividing line between dimpling and countersinking, but there are always exceptions.