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Dan raises a valid concern over stress concentration in the main spar web.
I probably would not have considered this mod if a friend, who has had his
320 flying for about 8 years, had not tried it first.
My understanding of the spar webs job is to remain stable while holding the
caps apart. With the forward spar web closeout and rib attachments plus
holes for wing mounting bolts, etc. adding stress concentrations to the
spar. I would think the 3/8" fuel line hole in the main spar web at BL52
would not be any different if reinforced with 1/4 x 2'' tapered phenolic
with 6 bid tapered from top to bottom of the web on both side of the web. I
am not recommending this mod to anyone since you would have to load test the
wing to failure or have a formal structural analysis to determine its
validity. We are all adding our little "improvements" as we build, I am
comfortable with this one.
Marv, to further describe this, the 3/8 line is bent 90 degrees inside the
outboard spar closeout web, routed thru the closeout web at the inboard
angled location and continued along the forward main spar web, angled uphill
until it turns up at the nose gear tunnel to the fuel selector valve.
Steve
PS: I have another friend with a 360 feeding direct from the wings who
routed his fuel line thru the aft spar phenolic at about BL52 and ran it aft
of the rear spar to avoid clearance problems in the wheel well.
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LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
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