Split in 2008 37 cruiser fuel tank

[Craggles]

Hi all. A couple of sails ago I thought I could smell diesel down below. I looked all around but couldn't see any diesel anywhere. I was stowing some groceries under the floor today and I could see a slight residue under the plastic boxes that store the supplies. After looking around with a torch because it's hard to see anything due to the double skin I could see what looked like a thin film of diesel between the skins. No fuel to be seen under the engine of in front of the fuel tank which is under the starboard berth so I removed the hatch and poked my head around where the filler and breather is, expecting to see a leak around the breather or hose clamps. Nothing until I looked around the tank and found a small bulge and a split in the starboard vertical near where the filler and breather pipes go in. I poked a small knife through the split to confirm it was the cause, so along with a light film of diesel on the inner hull confirmed it was the culprit. To repair, I am thinking about epoxy resin and mat or sika flex with an aluminium patch screwed over it all.
Anyone had this problem or know of a better way to fix it?
Craggles

[Spirit of Mary]

The diesel and water tanks are made of PE. So almost nothing will sufficiently affix to this material. The best way for repair is to weld with a special hot air gun and PE welding material. I did my water tank like this and this worked very well. I don't know if your diesel which contaminated the split will prevent a good weld. If you can get the split closed by the hot air jet (execute with a lot of feeling) and then degrease the surface and next put a full weld bead on top to make it sufficiently strong.
I would look for a professional plastic welding gun to borrow somewhere.
Ger

[Craggles]

Hi Ger,
I searched the net and came up with a few repair kits which say they are impervious to diesel. They are an epoxy compound, some are a putty. I think I can clean the diesel out of the split sufficiently and if it leaks, I can redo. There is a bloke that makes poly tanks here in the marina. It might be worth talking to him.
Craggles

[Ripster]

Avoid using sikaflex as it doesn't like diesel.  Hylomar blue seems to work ok, but I agree plastic welding is a far better permanent solution.   There is stuff called Milliput which is supposed to be very good - there are different types of it.

[Spirit of Mary]

Hi Ger,
I searched the net and came up with a few repair kits which say they are impervious to diesel. They are an epoxy compound, some are a putty. I think I can clean the diesel out of the split sufficiently and if it leaks, I can redo. There is a bloke that makes poly tanks here in the marina. It might be worth talking to him.
Craggles

I recommend talking to the bloke of the poly tanks. He for sure knows if it can be repaired with epoxy. PE feels a little fatty and epoxy might not stick sufficiently to PE.
Ger

[patprice]

Disclaimer.....I know very little about PE tanks.
But I do know that if you do a botched repair it will become all the more difficult to fix.
Definitely speak to the local welder. Then also get a second opinion.
Maybe as a thought repair the damaged area then weld a patch over the whole repair. This might hold some of the stresses that caused the initial failure. But it may have been a faulty tank in the first place. In which case all the above still holds.
Just my thoughts.

[Tikitikitwo]

I had a similar problem.
See some pics here (foto_serb): https://drive.google.com/folderview?id=0BwCBNKs_H_f_R0pJSXVwemN2a00&usp=sharing

and my previous post http://www.bavariayacht.info/forum/index.php/topic,328.msg1680.html#msg1680

I repaired it with a plastic  welder using a reinforcing mesh stainless steel  and PE plate from http://www.az-reptec.de/

When the tank is full it bends because under it there is not enough foam. Give a look under it and fill it with more foam
Maurizio

[Craggles]

I ended up using "dynasteel plastic tank repair". It's designed for plastic, PE tanks with petrol or diesal. It has stopped the leak and if it leaks again when I fill it (I have about 100 ltrs out of 150 in the tank and usually have it full) I will clean it off and weld it. I believe the reason is bulged and cracked was point contact under the area where it cracked. The simple answer was for Bavaria to have a flexible material under the tank to stop the point contact.
Craggles

[Narragansett]

Have exactly this problem in my 2006 33 Cruiser with the 150 litre (40 gallon) tank. Curious how your dyna-flex repair held up. Having trouble finding anyone to plastic weld a fuel tank. Thanks!

[Yngmar]

If you're looking for someone to do the plastic welding, ask at a nearby kayak repair shop. Or just watch some videos on the subject and do it yourself.

[Narragansett]

Thanks for the tip. I'm up for most repair challenges DIY, but am a bit leery about bringing heat to a plastic diesel tank. From what I can determine the flash point of diesel is just about exactly the same as the melting point of PE. Anyone here taken on such a project (and lived to tell the tale!)?

[Yngmar]

The tank must be emptied before any welding, whether done by you or anyone else. Even if it was a water tank the fluid cooling would prevent a proper welding job.

[Narragansett]

Thanks Yngmar. It appears from previous posts that you are quite familiar with this tank. Is simply emptying the tank sufficient for a safe weld? I was considering running a mini-shop-vac through the fuel gauge port to eliminate fumes and draw fresh air through the filler/vent lines, which enter the tank directly adjacent to the 1-1.5 inch split.

[ICENI]

The origal poster had a Cruiser 37.   My friend had one of these boats and he had this problem.

He decided to replace the tank and had lots of problems getting it from Germany to his boat in the Ionian!

I really felt for him at the time on two counts:-   

1 the long wait and the resultant loss in sailing that year

2)   He and his partner living on board with the unpleasant smell of diesel!

He felt the cause with his tank was caused by the yard lifting with the straps not in the area of the supporting bulkheads.   BEWARE!

[Narragansett]

Thanks Chris. The pick-up tube in my tank had been replaced right before I took ownership of the boat and I wonder too if the yard did a pressure test that caused the split. They deny it. My winter project while the boat is on the hard is deciding whether to attempt an epoxy repair, knowing full well the incompatible properties of the PE plastic, or to find a way to safely weld it shut (preferred). I'm in the "what worked for you?" info gathering phase, with months to go before I need to decide.

[Salty]

Thanks Chris. The pick-up tube in my tank had been replaced right before I took ownership of the boat and I wonder too if the yard did a pressure test that caused the split. They deny it. My winter project while the boat is on the hard is deciding whether to attempt an epoxy repair, knowing full well the incompatible properties of the PE plastic, or to find a way to safely weld it shut (preferred). I'm in the "what worked for you?" info gathering phase, with months to go before I need to decide.

Maybe the thing to do is to get hold of an empty 5 gallon PE drum, put some diesel fuel into it and then empty it out and have a practice slicing a hole and welding it up at home in your back yard before attempting to do your boat fuel tank. If you leave the lid off the emptied drum, even if it catches fire, which I think would be pretty unlikely as diesel gives off very little vapour, so I think that as long as you follow any instructions provided either with the repair kit or the You Tube videos, its not going explode with any force enough to do any damage. At least this would give you chance to practice PE welding before you do it on something that might turn expensive if you make a hash of things.