Tailcone belly skin

[Bryan Cotton]

Hi all,
I am cutting the big mixer access hole in the big triangular tailcone bottom skin. Plans show the rivet hole layout to pick up mixer mount stuff. The mixer mount stuff has CNC holes. Would it not be better to just cut the big access hole and transfer the CNC holes from the mixer mount to the skin?

[Rynoth]

That's what I did Bryan.. I cut the access hole first, then transferred the laser cut holes from the channel to the skin later on, after I had the skin clecoed in place and the mixer mount fully located.

I did this step (rivet holes) after having updrilled the entire aft fuselage box, so I basically tore down everything (removed clecoes) for deburring until I had just the skin, mixer mount and the adjacent formers left. Then I transferred the holes. Basically just be sure the mixer mount is in its final resting place before you drill the holes.

I've followed the philosophy of not drilling holes until I've eliminated all possibility that there's a laser cut part to match the holes to... the parts are newer than the plans, and especially if you don't have machined angle components, marking and making holes per the plans can run you (me) into trouble if there's a laser part to match. Thankfully I learned that lesson with my very first angle part fabrication, though I've still had to remake a part or 2 due to this.

[Bryan Cotton]

Thanks Ryan, sounds good.