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Flying Scotsman

Well Known Member
I'm getting ready to measure and order flexible fuel lines for the runs from the fuel selector to the tanks.

Right side - no worries, Brett at Bonaco has the length for a "standard" Van's fuel pickup.

Left side - flop tube. Need to go selector to side/skin, 90 degree AN fitting, fitting to flop tube.

Trouble is, as I'm sure you're aware, that side skin area has a second, "inner" doubler which is separated from the skin by about 1/8". No way to get in there now to put any kind of washer or filler (should have thought of this back when I was building the fuselage, but I'm here now...).

So...I see three options:
1. Fill the gap with some sort of something (epoxy, fuel tank sealant, some sort of other goop); ick.
2. Drill the doubler to correct size for the fitting, and the skin big enough to take the washer/nut.
3. Same as 2, but drill the skin and open up the doubler.

I think option 2 is best, but am I missing something down the road (when I put the wings on again) which will bite me?

TIA

Steve
 
I think option 3 would be better; the bulkhead nut would seal the hole at the skin and prevent anything from coming inside. With #2 you've opened up a route for things like cold air or anything at the wing root to migrate into the cabin. On the other hand, these airframes are not airtight so it probably doesn't matter that much. I'd say option #1 is right out but you could probably make a shim from aluminum stock to slide in there, which might be the best solution of all.
 
flion said:
I think option 3 would be better; the bulkhead nut would seal the hole at the skin and prevent anything from coming inside. With #2 you've opened up a route for things like cold air or anything at the wing root to migrate into the cabin. On the other hand, these airframes are not airtight so it probably doesn't matter that much. I'd say option #1 is right out but you could probably make a shim from aluminum stock to slide in there, which might be the best solution of all.
Click to expand...

That's a pretty good thought on sealing the skin...thanks.

No way to slide anything in between them that I can see...sealed on all four sides by bulkheads, stringers, etc.

My only concern with option 3 was that the skin is thinner than the "doubler", and might flex more...but you have a good point.

Thanks...

Steve
 
Aluminum line

I am not familiar with your situation, but hard lines would be the normal way to plumb this part of your airplane. A couple of grommets would do the job if you cant use a bulk head fitting. Making these lines is not too tough.

Cm
 
Suction specs on hoses

If using hoses on a suction line (which you are) check the specs for the hose to make sure they will not collapse if you draw a vacuum. Some hoses will collapse, others require a spring inside to prevent collapse. Aluminum lines are better for this.
 
5 responses, of which one actually answered the question. :)

I *know* hard lines are one way to go, I just don't *want* to...I reached my patience limit doing the brake lines, and I just want to finish sometime in this lifetime. I've heard of no reported issues with Bonaco's fuel lines, either.
 
Flying Scotsman said:
I'm getting ready to measure and order flexible fuel lines for the runs from the fuel selector to the tanks.

Right side - no worries, Brett at Bonaco has the length for a "standard" Van's fuel pickup.

Left side - flop tube. Need to go selector to side/skin, 90 degree AN fitting, fitting to flop tube.

Trouble is, as I'm sure you're aware, that side skin area has a second, "inner" doubler which is separated from the skin by about 1/8". No way to get in there now to put any kind of washer or filler (should have thought of this back when I was building the fuselage, but I'm here now...).

So...I see three options:
1. Fill the gap with some sort of something (epoxy, fuel tank sealant, some sort of other goop); ick.
2. Drill the doubler to correct size for the fitting, and the skin big enough to take the washer/nut.
3. Same as 2, but drill the skin and open up the doubler.

I think option 2 is best, but am I missing something down the road (when I put the wings on again) which will bite me?

TIA

Steve
Click to expand...

#3 should NOT give you any problems down the line.
 
FWIW

I am going the same route as you describe, flexible (Bonaco) fuel lines from the tanks to an Andair selector. I haven't drilled the holes yet but I am planning on your option 3.
 
stevemcgirr said:
I am going the same route as you describe, flexible (Bonaco) fuel lines from the tanks to an Andair selector. I haven't drilled the holes yet but I am planning on your option 3.
Click to expand...

Any reason why you chose to open up the thicker doubler, rather than the thiinner skin? I was thinking the fitting would be more rigid if tightened to the doubler, which why was planning on doing that...
 
To be honest, I saw it done that way on someone's web site when I was in the process of measuring lengths for Brett at Bonaco, and really hadn't considered other potential install variations. The fuse skin is plenty strong. There are too many decisions in this process to overthink ALL of them!
 
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