How much twist to twist?

I'm looking at the f-713's, f-719's, and F714's in th forward fuse these are the fwd aux. longerons, the skin stiffeners and the lower longerons.

Construction manual says "twist slightly" and "bit of twist." WHY

I'm spoiled I guess and I really want to measure the parts in some way, that way I know I've done it correctly (or incorrectly)

so, my question is... how much twist to twist?

can I just twist to what matches section K-K

Section K-K shows the ends where they meet the lower firewall weldments

do I measure the angular difference between the vertical leg of the longerons and the lower firewall angle and shoot for that?

I just went though these steps this week. I clamped the longeron in the vise and measured the angle of the flange before and after twisting. At first I added about 3 degrees of twist, put the part back in the fuselage and found that twist insufficient. I ended up in the 7 to 9 degree neighborhood for a good fit.

Longeron twist

Of course you want to get the longeron bends and twists as close as possible to exact (the plans say 17 deg of twist), but if I remember correctly, and I am certainly losing that capability, the longeron lays against the upper engine mount brackets. If it is not quite right, you can finish it up slightly when you get to that point so that it lays just perfectly on those corner brackets.

the twist of the upper longerons is fine

It's the lower and aux. Longerons that don't have a spec to refer to. Do you see my frustration?

so...

turns out, that the measurement is about 7-10 degrees.

I over-thought this one.