Testing the longeron bend/twist

Hi,

I have finished beating the longerons into submission (I think). Is there a way to test fit the 95.4 angle with the twist (the curve is easier to test fit, so that should be ok I think)? I'd rather not rivet the side skins on until I'm sure that the opening of the angle and the twist will fit whatever they are fitting against. I thought I could cleco the remaining parts together if that will help. Thanks!!

Measure from front carefully

If you have measured from the front to the start of the bend, you should be OK. The rear has no critcal stopping point. The front does.

John Bender

John,

I'm not concerned about the length as much as making sure whatever the "opened angled twist" has to attach to will fit. It's difficult to get it exact as the angle was not even a perfect 90 at the start. I just want to make sure that whatever it attaches to will fit.

Angle up front

It is the base for the shelf plate. Needs to be fairly accurate. 1 degree is not a problem I'd say.

John Bender

Paul,

I used a digital level (about $25 at Sears) to measure the twist and the opening of the angle to 95.4 degrees. The digital level reads to 0.1 degree. My fit was perfect. Without the side skins in place and the longeron drilled, I can't think of a way to test fit it.

JBPILOT said:

It is the base for the shelf plate. Needs to be fairly accurate. 1 degree is not a problem I'd say.

John Bender

Click to expand...

I agree with John. Get it as close as you can and call it good. You can tweak it alittle if you need to later.

Install fuel lines first

Paul, if you have not installed the fuel lines yet, now is a good time before putting those side skins and longeron in the way.
Joe

Page 23-02 Longerons

If you put a square against the angle, there should be about 1/16" gap at the vertex. Also, the top of the entire length of the longeron should be horizontal and flat and on the same plane. You could lay a straight edge across the two installed longerons without seeing much of a gap between the longeron and straight edge. The vertical side of the angle where you opened it up should be parallel with the side skin. The fuselage at that point is wider at the bottom and the side skin curves inward to meet the longeron. The purpose of opening the angle is to allow the the side skin to lay flat against it. Also, the end of the longeron should match the curvature of the upper firewall. There is a picture on page 29-01 that might help. If you are off one degree, I do not think that it will be noticeable. If it is off too much, you might see a bend in the side skin.
Joe

Paul,

I have just finished mine and had to make some small adjustments.

Here is what you need to do, get it as accurate as you can at this stage.
When you actually fit it to the fuse and match drill the longerons and the side fuse skins, before removing and deburring them do the following:

Fit as many cleckose to the forward portion of your side skins and longerons as possible to mimic rivets. Take your avionics shelf and upper fire wall and temporary fit them also to the fuse and top of the longeron. Now you will see how perfect your longeron bends were.

Take a measurement of how far you are out. Remove the skins and longerons to debur them as the plans say. Now put your longeron back into the vice to make that last small adjustment. Take a measurement to a fixed position, then make the adjustment to the longeron as measured while it was on the fuse.

I had to bend both my longerons in the front an additional 1/4" inboard to fit the avionics shelve without any force on them.

I hope it makes sense.

Regards
Rudi

Thanks and one more question

Rudi and all the people who gave advice,

First off, thanks. I really appreciate the help. I know I have to get this just right, so I'm going slowly. The shelf you guys refer to, what is the part number for that? Is it the shelf onto which the rudder pedals attach, or is that the firewall shelf that has been mentioned. There seems to be another shelf in the plans (for avionics?) If anybody has pictures in the blogs with a fitted piece could you point me in that direction? I still think I can be finished and ready when the finish kit shows up. Again, thanks!!!!!

Hi Paul,

They Are
F-1201A Firewall Upper
F-1202B Panel Base

See Page 29-04

The Panel Base was the shelve I was talking about, it is tapered and lies on TOP of the forward longerons. With those 2 items cleckos in place it will show you the exact width and bend required to tweak you longerons, before you remove to debur them

Regards
Rudi