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Steve Sampson

Well Known Member
I had one comment on my blog to the effect that the way I have organised the ally tube taking the fuel from the tank to the fuse' may cause an airlock.

The tank concerned is the left tank with a flop tube and I had the normal and difficult task of getting the fuel past the front F-463 support bracket while remaining inside the profile of the wing

Here is a picture. http://gikonwings.blogspot.com/2007/03/fuel-pipe-from-left-tank-flop-tube-side.html#links

The resultant bit of tube undoubtedly goes on a very convoluted path, and is no work of art. I was happy with it though, because unlike the many feet of tube I had destroyed before coming up with this piece, it provided a stress free connection, and it is hidden. Now I am worried. The genuinly concerned comment was to the effect that because I had a high point, if air got in, and the fuel was a little low, I might not get more fuel past this high point.

My logic is (was) that there are several high points in the fuel system, in fact the tank selector valve itself is one, and provided the good old fuel valves kept on sucking fuel would pass this point. In fact in a tail dragger the pumps are at a high point.

I would be very interested to hear more views since this is not an unimportant issue.
 
As long as the suction head of the pump is larger than local variation in elevation of the line, there is no problems. It is not the uphillness or downhillness the draw the fuel through the line, it is the pressure difference between the pump inlet and the fuel outlet of the tank. This is not a gravity fed siphon type of system.
 
I went through the exact same scenario you did. What a pain. I wished I'd just put a regular pickup in my tank!

Why not put a flexible aeroquip type hose on there with a 90deg. fitting for the tank end and a standard flared end for the bulkhead fitting? Just rotate your bulkhead fitting 180 deg. and thread it on.

There's a place here in town that custom makes hoses and that one would cost maybe $20. I've had all mine made there for about 1/5th the cost of the hoses on aircraft spruce or Van's and if you wonder about the quality, there's an F-86 and a bunch of local experimentals flying around with hoses from this place.

Send me a p.m. if you don't have a hose shop in your neighborhood and I'll be glad to help you out.

Chris
 
Yes, I agree if I were building again I would forget the flop tube.

Chris, thanks for the offer of help. Really kind. In fact I think SvingenB has it right and I do not have a problem. Possibly the objection came from someone who was thinking of a gravity system. Since I think the fuel will suck through I will stick with my very bent bit of pipe since it exists and fits well.

Thanks for the inputs.
 
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