Airflow under Fuel Tank

[DougP]

I have the diesel tank out of the boat for repairs, and I'm considering adding some airflow under the tank when I put it back. The plywood shelf the tank sits on is poorly glassed and part of the tank sits in moisture. The shelf also has a raw edge that has soaked some diesel, so I can't glass over it without removing & rebuilding, which I won't have time to do until Fall.

I'd like to get some airflow under the tank when I put it back in. I'm considering putting a thin, hard commercial rubber doormat with holes or channels molded in under the tank. Should be easy to cut, resistant to oil/ fuel, free of electrical/ galvanic corrosion issues, and provide some airflow without introducing anything that would rattle or bang around.

Anyone see a downside to this?

[kh3412]

Sounds like a plan. I coated my tank with truck bedliner when it was out.

[Ron Hill]

Doug : It sounds to me like you have a fuel leak problem if the shelf is diesel soaked!!

While the tank is out I'd chase down and fix that leak - filler hose connection? fuel gage gasket? overflow vent/hose? OR pinhole in the tank itself??

A few thoughts

[DougP]

Definitely a pinhole leak in the fuel tank. A low spot in the shelf collected just enough water from condensation and probably leaks from the port locker to allow the tank to sit in a film of water. The actual leak was very small, but even a small drip over a long winter can cause problems. I suspect there the amount of fuel lost was well under a gallon, which is all it took to make a mess and give my boat and everything in is a lovely eau de diesel.

[Stu Jackson]

.....................................and give my boat and everything in is a lovely eau de diesel.

www.pureayre.com

It can work wonders.

IIRC, since it's been a while since I've had the wall off, my fuel tank rests on a few two by fours.  I'll see if I can find the photos.

[Dave Spencer]

Doug,
Here's a post with pictures of my fuel tank.  http://c34.org/bbs/index.php/topic,9355.msg69460.html#msg69460  I removed and cleaned my tank with acetone several years ago as recommended by Ron Hill in his Mainsheet article.

Pictures below show the space in the hull after I removed the tank.  There were no  pads or lumber supporting my tank but there is certainly room for some with lots of clearance between the top of the tank and the floor of the port lazarette.  In the pictures below, you can see what looks like rubber weatherstripping on the hull outboard of the fuel tank.  No doubt, this is to prevent noise from vibration if the tank ends up too close to the hull.  I didn't touch the weatherstripping when I pulled my tank out.   

Since you have gone to all the trouble of accessing the tank to repair a leak and clean up the spill and the odeur de diesel , it makes a lot of sense to clean the inside of the tank as well.  Ron's method with acetone or, the very creative  method used in Reply #7 here http://c34.org/bbs/index.php/topic,9731.0.html will do the trick for you. 

Good luck with your repair and cleanup.

[Ron Hill]

Doug : Look in WiKi as there are a number of articles (Mainsteet tech notes & this message board) on ordering a new metal tank. 
Not too sure I'd even try and patch the old tank - especially now going thru all the work of having to cleaning up & battle the smell.

Too bad the PO didn't use more "Water Absorber" made by MDR!!

A thought

[Noah]

I saw a"new" tank for sale on our websire's parts and pieces section...
http://c34.org/bbs/index.php/topic,9815.0.html

[DougP]

Had the tank professionally (Precision Fuels in Seattle) cleaned out, etched, and coated with two coats of epoxy & fiber for $300. Tank went into a roto-molding device that spun & rotated it for a couple days with acetone and hard media (which I assume was a fancy/ expensive term for a handful of nuts & bolts) until it was scrubbed clean. Another spin with a coat of epoxy, a spin with chopped fiber, and a final spin with another coat of epoxy. At this point they tell me that other than the fittings the interior tank is stronger than the original exterior aluminum. Before re-installing I'll be gluing (5200) 1"X1/4" strips of semi-hard (not foam) neoprene down the hull side and across the bottom of the tank. This should allow an air gap, space for leaks to flow, and a vibration buffer between the tank and the shelf or hull.

Also ordered and doused everything with PureAyre. Not 100% sold yet, but it's already vastly better than Fabreeze.  Once the epic level rains we've been experiencing stop and I can air the boat out a bit we might just be OK.

Thanks for the ideas an suggestions everyone!