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Longeron length at firewall/770 skin forward

DAS

Member
Just drilling the longeron and at the firewall end, plans say to trim so that the longeron is 3/4 inch short of the 770 skin edge. (I do have all the sections cleco'd together at this point)

Question to all.

I'm just shy of 1/4 long of this measurement, or I mean, will have to trim off about 1/4 inch of the longeron....Is this common to y'all?

The location was set because I trimmed the longeron aft based on the F714 deck and DWG 19...which measurements are within 1/32 of the drawings on detail C...
so my concern is that the placement of the F721 aft canopy deck piece and the bend down at the 28 1/4 mark are all gonna be about 1/4 inch forward. Because it seems the longeron is 1/4 inch forward in position... bad news, is I don't see a fix if matters other than starting over with the longeron,
 
Pretty common. measure to 1/32 inch or better, then chop off the excess later on. I had to trim about a quarter inch off when I did mine too.
 
Me too. Exactly the same thing. The problem is that if you don't trim the longeron back a good 3/4, it will butt up against the firewall and you won't be able to set the firewall the specified distance aft of the forward edge of the side skins.
 
Error

Me too. Exactly the same thing. The problem is that if you don't trim the longeron back a good 3/4, it will butt up against the firewall and you won't be able to set the firewall the specified distance aft of the forward edge of the side skins.

I believe the OP has a slightly different problem. It sounds like the longerons are both forward of the ideal by 1/4". I'm guessing the slot for the F711C bars or the relief for the F712 may be off but he confirms they are correct so something has to be off by 1/4 for the longerons to be shifted forward that much. I don't have an answer except to double check everything. My bends landed exactly where the parts and plans show and I only trimmed a tiny bit for the firewall to clear.
 
thanks all,

I do believe that the measurements are off a little if you go by the drawing and trim the aft end just based on detail C of drawing 18....I measured from the first hole which is shown as 2 5/32, reality for me this needed to be about 2 5/16 inches. ..... obviously this adds about 1/4 inch shift aft and then all would look perfect.

What would be nice is to have the measurement from the forward end of the longeron to the forward edge of the F 711C, because everything is measured from there..

so those of you that did have to trim about 1/4 inch, did that create any problems down the road??

das
 
Build on

thanks all,

I do believe that the measurements are off a little if you go by the drawing and trim the aft end just based on detail C of drawing 18....I measured from the first hole which is shown as 2 5/32, reality for me this needed to be about 2 5/16 inches. ..... obviously this adds about 1/4 inch shift aft and then all would look perfect.

What would be nice is to have the measurement from the forward end of the longeron to the forward edge of the F 711C, because everything is measured from there..

so those of you that did have to trim about 1/4 inch, did that create any problems down the road??

das

David
I agree on the measurement. In my case, I measured from the parts and probably got lucky.
No one responded so I suggest you cut the forward end and reinstall them to see how that 1/4" effects things. I suspect it won't matter much.
Please post to the "Gotcha" thread for future builders.
 
This is what I had to trim off. I trimmed it the same angle as the skin. Worked out great.


DSCN1145.JPG
 
IIRC, that's about how much I trimmed my longerons at the forward end. I riveted the sides and bottom of the forward fuselage without issue. When I prepped the airplane for my relocation earlier this year, I clecoed all the top forward fuselage components in place, including the instrument panel and the forward top skin, and everything fit fine.
 
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