Transfer from wing tanks

Fuel tanks, systems and parts
Holcombe
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Transfer from wing tanks

Post by Holcombe »

My Champ 7CCM has the 5 1/2 gallon wing tank and generally transfers in about 30 minutes while flying.

Recently, a couple of times the transfer has gone much slower. With the fuel guage bouncing on empty the fuel was still comming down, but not as fast as I was burning it.

I have been through the tank, clean, the fuel line and valve, clean, and blown through the vent and found no obstructions. The cap is a radiator cap with a one way vent which is working correctly. When the tank is empty, valve open, I can blow through the vent and immediately get bubbles in the main tan.

Am I missing something? Has anyone else encountered this?
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MikeB
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Post by MikeB »

I think this is why some of the tanks have a bent pipe brazed to tank cap which gives a 'ram air' effect. I noticed several at Oshkosh this year as I was paying particular attention to the fuel tank and valving set ups. Getting to that point on my L16 restoration project.

Mike
Paul Agaliotis
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Post by Paul Agaliotis »

It sounds like the cap vent. The wing tank needs to allow air to enter as the fuel transfers and also the main tank has to let the air vent out as the fuel from the wing tank enters. Either one will cause a slow to transfer condition.
Transfer should begin when the main tank is at 1/2.
Paul
One other thing. If you have been using Mogas the cap gaskets will crack pretty quick. This will allow the low pressure on the wing top surface to effect the air space in the wing tank.
Paul
Last edited by Paul Agaliotis on Thu Jul 30, 2009 21:57, edited 1 time in total.
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Holcombe
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Post by Holcombe »

The vent is the overflow which exits the bottom of the wing. It is clear. I know because I can blow through it. The cap is on the top of the wing in a low pressure area and is unvented.
This slow transfer has happened a couple of times recently, and may have been when I waited till the main tank was well down, possibly letting air get up into the line from the main tank. But this still shouldn't be a problem. Gravity and air pressure from the wing tank should just push through.
The forward facing vent tube in the cap seems like an extreme solution that shouldn't be necessary, and from time to time these caps get put on backwards causing immediate grief. I don't want to go that route.
Thanks for the responses, still looking for more ideas.
Tail winds are a "Good Thing"
Captgrumps
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Post by Captgrumps »

Wing tank vent needs a forwad facing vent--looks like a bent peice of tubing brazed to the cap and the main tank needs a vented cap. My old Champ had a wing tank with the forward facing vent and used a J-3 type wire guage in the main tank.

Doug
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MikeB
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Post by MikeB »

Paul does make a good point, though. If the main tank vent is restricted some way I'm guessing it would creat a light pressure in the tank when trying to fill it from the wing tank. Easiest was to check would be to make a fuel flow check from the wing tank by removing line from main tank.

Mike
CptKelly
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Re: Transfer from wing tanks

Post by CptKelly »

Gail's Champ had the same problem when we first got it, it took a LONG time to transfer to the main tank. No, nothing wrong with the vents. I asked one of my IA buddies about the problem, and he brazed a small piece of tubing onto the wing tank cap, and bent it forward, into the airstream. He also flared the opening of the tube. Now, the fuel transfers really fast, much faster than fuel is being used up. In my opinion, if this worked for me, it should also work for you.

Mike
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David Johnson
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Re: Transfer from wing tanks

Post by David Johnson »

On the 5.5 original tanks I have seen, the vent that comes out the bottom of the wing has a 45 degree cut facing forward. On the reproduction tanks, it is cut off square. Might make a big difference in the vent pressure, or lack of, to the tank. A square cut could produce suction instead of pressure. Just a thought from the back woods of North Georgia. David J.
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rkittine
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Re: Transfer from wing tanks

Post by rkittine »

I wish I would have read these posts before I pulled my hair out with the same issue. If you go to http://www.Aeronca.org and get on the forum, you will see that I posted a detailed account of what happened to my wing tank and what fixed it. A full article with pictures will be in their January News Letter.
Last edited by rkittine on Mon Nov 15, 2010 17:08, edited 1 time in total.
Robert P. Kittine, Jr.WA2YDV
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joea
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Re: Transfer from wing tanks

Post by joea »

Robert,

Posting something on the other forum is not going to help a whole lot I am guessing. They have a total of less than 2000 total posts, while we are chugging right along with over 30,000 posts in far less time than their bulletin board has been around.

More viewers and posters means more ideas and chances to solve things. Its up to you where you post but you will get more help here...

Joe A
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rkittine
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Re: Transfer from wing tanks

Post by rkittine »

Hi Joe,

There are 72 posts on the other Forum about my Fuel Transfer problem. I just tried to upload a Word Document that tells the whole story, but I got a message that the Exntension "doc" is not allowed. Any thoughts? I have uploaded a picture of the cap (just sitting on the cowl of my Champ) prior to priming and painting it red.

Ciao - Robert
Attachments
NEW CAP READY TO INSTALL - RS.jpg
NEW CAP READY TO INSTALL - RS.jpg (50.38 KiB) Viewed 5558 times
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
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rkittine
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Re: Transfer from wing tanks

Post by rkittine »

In short form, the addition of Vortex Generators on my Champ and the replacement of the fabric over the wing tank with a sheet of aircraft aluminum for easy access in the future (the wing tank cap then sat down into the metal and was not above the wing surface as much as it was when sitting on wavey fabric) is thought to have increased the negative pressure over my wing tank cap, which in 9 out of 10 fuel transfer attemps would not allow fuel to flow. Every time I raised the tail in the hanger and tried transfering, it transfered flawlessly. Once in a lot of turbulence (probably broke the low pressure area over the cap long enough to get it started) the fuel did flow and once it started it did it ok, though it was slow.

This cap, puts the vent (I used an unvented cap as suggested by Bill Pancake to me to fabricate this) above the boundry layer and into the airstream. It now transfers 100% of the time (at least so far during at least 6 tests) and transfers 5 gallons in about 4.5 minutes.

Headspace in the main tank is not a problem, which I learned by trying to transfer when there was less than 5 gallons burned off the main tank and during the tranfer, fuel started coming out of the main tank's cap.
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
rkittine@aol.com
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rkittine
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Re: Transfer from wing tanks

Post by rkittine »

If anyone wants the Whole story on my Wing Tank Transfer, E-mail me at rkittine at sign aol dot com and I will send you a complete Word Document along with photos.
Robert P. Kittine, Jr.WA2YDV
West Nyack Aviation, L.L.C.
New York, New York 631-374-9652
rkittine@aol.com
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joea
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Re: Transfer from wing tanks

Post by joea »

Robert,

Easy solution. Open the word document and "cut and paste" the information.

Then open a new window/reply here and "paste it" onto the new reply.

Joe A
Holcombe
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Re: Transfer from wing tanks

Post by Holcombe »

If you make the ram air vent for the fuel cap to presureize the tank, do you close off the overflow so the air from the cap vent doesn't just blow out the lower vent on the underside of the wing.
When I started this thread it was because I had had a problem once or twice, but not generally. What I want to know is why the wing tank would drain slowly occasionally, but not cause a problem most of the time. For me the cap ram air vent is overkill.
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