What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Fuselage level

Av8torTom

Av8torTom

Well Known Member
Hello everyone,

With the wing spar carry through level, this is the situation at the 709 bulkhead in the tail. Is this acceptable; if not, can it be fixed?

Thanks,

Tom

 
N941WR said:
Aren't you supposed to level the fuselage using the longerons?
Click to expand...

Well I figured ultimately I want the wing and horizontal stabilizer to line-up/be in the same plane with each other, so I used the spar carry-through as a reference point. How would you suggest I check for unacceptable twist in the fuselage?

Thanks,

T.
 
Av8torTom said:
Well I figured ultimately I want the wing and horizontal stabilizer to line-up/be in the same plane with each other, so I used the spar carry-through as a reference point. How would you suggest I check for unacceptable twist in the fuselage?

Thanks,

T.
Click to expand...

I would call Van's and ask them. I leveled mine using the longerons because I figure the bolt holes were drilled in a jig and leveling to the top of them may not be accurate.
 
Top horizontal firewall stiffener, spar carry through, seat back bulkhead, and, if you bent them right, the longerons, should all be roughly level at the same time. Then, get the aft fuse deck as close as possible to that. It can easily be fixed depending on how the aft deck is clamped. If it is already riveted, then you're stuck with that twist.
 
The firewall stiffener, spar carry through and seat back are all parallel and level. Somewhere between the seat back and tail a little twist was entered (about one degree). Longerons are not yet riveted in place nor is the aft fuselage deck.

So the question remains: is this acceptable and if not how can I fix it?

Thanks...
 
If you haven't drilled the rear deck to the longerons (and hopefully not the longerons to the side skins), no worries.

Untwist it. Clamp the deck and drill. You may have to open the slots for the spar bars a bit to fudge the position of the deck to center between the longerons.

Precision "level" is not needed. All that's necessary is the rear deck, 704 or span across the longerons at all points, the firewall stiffeners, et al, are all parallel. Yeah, sorta level the fuse pitch-wise so the bubble level is sorta vertical to the ground. (You can imagine it would be useless if the fuse were standing on end.)

John Siebold
 
Cleco on the top fuselage skins and that should help get the twist out. It is all prepunched, so it should line up with all of the other holes and make a straight fuselage. Do this before you drill the aft deck and make the twist permanent.
 
The aft fucelage can be twisted relatively easy untill the aft deck is attached. If it's like mine you should be able to twist it until it's level. You want to be sure there isn't a twist before you drill the aft deck.
 
Last edited:
bruceh said:
Cleco on the top fuselage skins and that should help get the twist out. It is all prepunched, so it should line up with all of the other holes and make a straight fuselage. Do this before you drill the aft deck and make the twist permanent.
Click to expand...

Bruce's recommendation is spot-on. The aft fuselage will not be torsionally stiff until the top skins are attached. Better to chase this twist out early.

Any chance that the rotisserie contributed to this twist? Looks like the CG will be offset from the axis of the rotisserie support, tending to twist the fuselage when it is displaced sideways. Try rolling the fuselage to level from the opposite direction and see if the twist is reversed.

Please share results!

- Roger
 
Thanks

Thanks again everyone. Apparently the piece of plywood that I used to attache the tail to the aft rotisserie stand was slightly warped and it was causing a twist in the tail



After I unclamped the plywood and rested the tail on a saw horse, all was perfectly level



Whew!!!
 
I know people keep posting to the contrary, but the aft deck or the aft skins will will torsionally lock the position of the tail cone. Which ever goes on first will win. Since with a standard build sequence, the aft deck is intended to be first, what ever alignment you have when the aft deck is drilled and riveted, is what you are going to get. The aft top skins will not change it.

With the fuselage sitting on the saw horse and the aft deck clamped in place while the fuselage is straight, drill and rivet the aft deck. Your alignment will be locked in.
 
RKellogg said:
Bruce's recommendation is spot-on. The aft fuselage will not be torsionally stiff until the top skins are attached. Better to chase this twist out early.

Any chance that the rotisserie contributed to this twist? Looks like the CG will be offset from the axis of the rotisserie support, tending to twist the fuselage when it is displaced sideways. Try rolling the fuselage to level from the opposite direction and see if the twist is reversed.

Please share results!

- Roger
Click to expand...

+1 on this ... I'm starting to rivet up the tail cone and did so with the top skins cleco'ed on. What a difference it makes to have the tail cone fully constrained. Everything is straight and level and tight. It was suggested by one of our mentors here on VAF (don't remember who, tho) Thanks!
 
You must log in or register to reply here.
Back
Top