08-19-2012: 4 hrs
First, I drilled the strap made of 0.063" to F719 fwd stiffeners to fix the shord edge margin problem on both left and right sides. The additon of the strap should be enough to get the lost capability back, both for static load and fatigue load. I made sure the strap covers 4 rivets so the strap will be fully effective.
Then , lleft and right lower longerons are fabricated per plan. The lower longerons are twisted to fit the lower engine mount bracket. The fit is pretty good.
Moving on to drilling the hole for the AN3 bolts on the lower longerons. This puzzled me a bit. The 1/2" distance bewteen the hole center to the inboard edge of the lower flange of the lower longeron won't provide enough edge margin on the steel bracket. I searched and read about other builders sites, this is a common problem. Most builders changed the 1/2" dimension to 7/16" so the edge distance on the steel bracket is about 11/32, still not quite 2D for the 3/16" diameter of the AN3 bolt. But since steel shows better fatigue performance, mainly due to steel has a fatigue endurance limit when stress is below which, fatigue is not a concern. On the aluminum angle side, the edge distance meets the 2D requirement. With extra carefulness, I drilled the lower longerons. Results turned out to be pretty good.
After that, the F902 bulkheads are clecoed to the side skins. The fit is very good with all the longerons and stiffeners
A strap was fabricated to fix the short edge margin problem on the left fwd skin stiffener
Same methd is used on the right side
Instead of 1/2" as called out in drawing, 7/16" edge distance is used on the lower longeron bottom flange, to give better edge marge margin on steel bracket
#30 size holes on the longer are drilled
Right longeron is clamped to the engine mount bracket
The final hole is reammed using #3 reammer
The edge distance on the steel bracket looks good
Left side is drilled in the same way
F902 bulkhead is clecoed, the fit is pretty good
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