new fuel tank

dick seiders · #1 10-13-2014, 03:31 PM

As I said earlier in another thread (new vent install) I am now testing a fully welded tank. It is constructed of 5052 H32 .090 aluminum. I have mounted the sending unit door and of course the Moeller gage on the top skin. I have used Van's cork buna gaskets for all three mounting plates, and was hopeful that they would seal the fastening screws, but no way. The soap bubbled air freely. So I had to make a concession to the Flamemaster tank sealant for the screws. That appears to have done the job still using the cork gaskets. Should further testing indicate any air leaking I will remove the 3 plates and the cork gaskets and apply tank sealant directly to the 3 contact surfaces w/o the use of the gaskets. The good news is all the leaking air was associated with the 3 plates. There are no leaks in the heli-arc welds.
It's been a while since I have conducted the air test and would appreciate any thoughts from your own experiences as to how long the balloon should hold the air and what is an acceptable rate of shrinkage?
Upon completion of satisfactory leak testing I will install the tank and run/flight test it. Following a successful test period I will send photos and tell all who are interested about what I have learned in this process about tank making for the RV12.
Dick Seiders

rgmwa · #2 10-13-2014, 03:44 PM

Dick, as I understand it, the only purpose of the balloon is to pressurise the tank while you check for leaks using soapy water. It's immaterial how long it stays inflated, except that if you have leaks it will obviously deflate a lot faster.

JBPILOT · #3 10-13-2014, 05:20 PM

Put the balloon test in place, and spray a mixture of 50/50 dishwashing detergent and water on it right away - ALL OVER. You will know if you have ANY leaks. Works great. Wash it off once satisfied.

rvbuilder2002 · #4 10-13-2014, 05:47 PM

Correct.

The intent of the balloon is to only use it as a very sensitive pressure indicator so that people don't blow up their fuel tank.
The pressure is so low, that judging the existence on a leak by the appearance of the balloon is not a valid test. Ambient temp change can cause a big change in the appearance of the balloon. It could actually hide the existence of a leak, if the temp was climbing while the air was slowly leaking out.

You can confirm this your self. Pressurize the tank the same as for a leak test, with tank at room temp. (~70 deg F.). Put the tank in the shower and spray cold water on it... the balloon will go flat almost instantly.

dick seiders · #5 10-13-2014, 07:24 PM

Thanks for getting back. Van's tech agrees . The balloon is to limit pressure. However, if it's still inflated, albeit at a smaller size after 6 hrs or so you have a leak free tank. I have that result, and in addition submerged it in my pool to look for bubbles and there were none. On to the next step. Thanks.
Dick Seiders

JBPILOT · #6 10-14-2014, 06:13 AM

Try the soap mix. You might be surprised. Will wash off easily. A tiny leak may not be seen in a few hours of sitting. Will not hurt anything, and you might be surprised.

dick seiders · #7 10-29-2014, 02:38 PM

New welded tank was installed last week. Have flown about 6 hrs since and there are no leaks, no fumes, no problems thus far. The Moller gage is a good fuel indicator once you have calibrated the gage by noting levels and needle position. It worked fine on a trip to FL. this past weekend. Also learned that the new vent is a positive FULL indicator when a little fuel drips out of the vent line. (wasteful maybe but a very accurate indication of full tank). I will attempt to get some pics posted if anyone is interested, and will be happy to answer any questions about the tank anyone cares to post, My initial re-action to the welded tank vs the original is roughly 10 times more positive at the very least.

Dick Seiders

rockwoodrv9 · #8 10-29-2014, 04:50 PM

Nice. I would love to see pictures. Thanks

Driftdown · #9 10-29-2014, 07:06 PM

Quote:

Originally Posted by dick seiders

New welded tank was installed last week. Have flown about 6 hrs since and there are no leaks, no fumes, no problems thus far. The Moller gage is a good fuel indicator once you have calibrated the gage by noting levels and needle position. It worked fine on a trip to FL. this past weekend. Also learned that the new vent is a positive FULL indicator when a little fuel drips out of the vent line. (wasteful maybe but a very accurate indication of full tank). I will attempt to get some pics posted if anyone is interested, and will be happy to answer any questions about the tank anyone cares to post, My initial re-action to the welded tank vs the original is roughly 10 times more positive at the very least.

Dick Seiders

Dick, any possibility the tank will be sold commercially?
If so, any other possibility the capacity could be slightly increased, like maybe 5-7 gallons?

Jetguy · #10 10-29-2014, 07:14 PM

Ok here is a few questions that I'm sure guys are thinking of asking.

How much would it cost per welded tank?

How much does it weigh compared to Vans Tank?

Do you still have the access hole in the front with the resistance fuel tank indicator?

Does it still have the baffles in it and are they welded in?

Is the threaded hardware on the bottom of the tank now welded on?

And yes pics of everything would be great. Thanks