Wing folding

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Wing folding

Postby barry767 » Mon Jul 13, 2015 12:07 am

Looks like I will have to start folding the wings of my Highlander to make room for another aircraft in my hangar. As a test I folded one of the wings with the fuel tank only about half full and found that the height of the fuel with the wing folded (and tailwheel on the ground) was still higher than the vented cap thereby allowing fuel to escape. Two possible solutions here:

1) fold the wings with the airplane in a level attitude - not practical or easy to do, or

2) prior to folding the wings, replace the vented caps with non vented ones. It seems to me that this would allow the wings to be folded even with a full tank and not worry about losing any gas overboard. Of course, it would be important to remember to change them back out prior to going flying. Has anyone tried this method?

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Re: Wing folding

Postby jak » Mon Jul 13, 2015 6:01 am

it the caps are not vented and it gets hot in the hanger the expanding gas will have nowhere to go and could damage the needle and seat in the carbs. drain the fuel. Jak
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Re: Wing folding

Postby barry767 » Mon Jul 13, 2015 1:43 pm

I was afraid you'd say that! How about this idea. Attach a clear plastic tube to the fuel cap vent whose end (oriented vertically) is higher (a lot higher) than the level of the fuel in the tank of the folded wing. From a physics standpoint, the fuel could not get any higher in the plastic tube than the highest level of the fuel in the tank, right? But the problem again may be it might be pressurised to rise above that level when the air in the tank heats up and expands.
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Re: Wing folding

Postby danerazz » Mon Jul 13, 2015 4:31 pm

Yes, if the fuel level is at the cap and things expand, fuel WILL be forced out even a high tube. Now if you plumbed that into a catch can with air gap you set on the wing, I doubt much fuel would escape merely through expansion, but it would be enough you would want to catch it. If you added vents at the top of the tank at the wing root, then capped them during normal ops but uncapped them when folding, the pressure would not build up and force the fuel out the cap vents. You still wouldn't want full tanks though.
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Re: Wing folding

Postby Gil T » Mon Jul 13, 2015 5:11 pm

Barry

I have been folding my wings since I started flying my airplane (S/N 28) because I keep it in my hanger(?) next to the house. I have it on a trailer which I tow 200 yards to a four wheeler track in the desert and that is my runway. The number to remember is 7.5 gallons. That will just about guarantee you won't overflow when it gets hot and the gas expands. You don't want a sealed system. You would end up with the fuel leaking out of the weakest fitting or carbs or wherever else it wanted to. I try to plan my flying so I end up home with that magic number or less. If I have think I may have a little too much I run a hose from the cap vent on each tank into a gas can. You must put a tee in this line just after where it is attached to the tank vent with a inch or so of tubing sticking straight up so you don't siphon the tank dry. You also have to do to both tanks or you run the risk of siphoning all the gas out of both tanks. If you have more than 8 gallons left its easy enough to stick a can with a funnel under the drain valve and drain what you need too. I think I posted several pictures of my setup. I'll see if I can find them.

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Re: Wing folding

Postby Gil T » Mon Jul 13, 2015 5:39 pm

IMG_0411.JPG
IMG_2293.JPG
Barry

Here is a picture of the tee arrangement. I just threw in the other picture for the hell of it.

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Re: Wing folding

Postby barry767 » Tue Jul 14, 2015 10:26 am

Thanks Gil and Dan. I suspect my critical number will be less than 7.5 because I've got the big Airstreaks installed which puts the wings more at an angle when folded, but I'm going to use your system.
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Re: Wing folding

Postby barry767 » Tue Jul 14, 2015 8:43 pm

Gil, what type/size of plastic tube did you use and where did you get it? Barry
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Re: Wing folding

Postby barry767 » Thu Jul 30, 2015 5:43 pm

Gil, I installed the plumping exactly as you described and it works great. Now that the wings are folded I discovered an unexpected benefit of now being able to easily clean the top of the wings!
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