Author Topic: 150 l diesel tank holed near filling and vent inlet (Read 6103 times)

BARAKUDA81 · « **on:** February 01 2021, 17:36 »

I am the owner of a bavaria 33 ft, 2006 model and lately I had noticed a diesel fouling smell below deck. I had noted that after I had refueled, diesel was found in the bilges. After a series of inspections around pipe work and the plastic tank I had noted that the tank is damaged at the entry.

Did any one experience this type of damage? To my reasoning the tank has some stress point and it punctured from this point.

I have attached a photo of the inlet to tank. I have used 2 part mix epoy to fix this problem but it just held temporary. I will be doing some plastic welding on the area but would like to investigate further as if i do not fix the cause, the problem will re surface. It is a 150 lt diesel tank and to my knowledge it is made of PE.

The option of replacing the tank is the last resort.

Regards
Ian

Yngmar · « **Reply #1 on:** February 01 2021, 19:59 »

Can you mark the spot on the photo? Not quite sure where it is. If it's where I think it is, on the side along the hull, with some yellow-white epoxy repairs, it almost looks as if the tank had been kinked at that spot, causing the material to crack. This can really only have happened during installation.

The tank is HDPE, and should be marked as such (on the top, a bit aft of the fuel take-offs).

PEA-JAY · « **Reply #2 on:** February 01 2021, 20:59 »

I watched on u tube a successful plastic repair using bicarbonate of soda with super glue mixed in a paste. Haven’t tried it but perhaps worth an experiment when all else fails. The end repair could be filed down and looked strong!

BARAKUDA81 · « **Reply #3 on:** February 01 2021, 21:15 »

Thanks all for the information. Yes it is kinked at the top where the yellow stuff is. I was thinking that with the weight of the fuel the tank will deflect down and flex this part and the material will crack, so i will reinforce the tank with some expanding foam beforehand. Thanks for the info on the type of plastic but could not locate it on my tank.

The bicarbonate of soda experiment is another idea but i was thinking to perform plastic welding on the area, excep that i have to empty tank and properly vent it.

Klausen · « **Reply #4 on:** February 02 2021, 07:35 »

Hi, do it the right way and weld it.
Klaus

IslandAlchemy · « **Reply #5 on:** February 02 2021, 09:14 »

Quote from: Klausen on February 02 2021, 07:35

Hi, do it the right way and weld it.
Klaus

Go careful. You don't want to set the boat on fire.

Yngmar · « **Reply #6 on:** February 02 2021, 10:53 »

Quote from: BARAKUDA81 on February 01 2021, 21:15

Yes it is kinked at the top where the yellow stuff is. I was thinking that with the weight of the fuel the tank will deflect down and flex this part and the material will crack, so i will reinforce the tank with some expanding foam beforehand.

That's odd, our tank is bedded on PU foam. Now that you mentioned it, I see no sign of this being the case on yours. The tank is shaped to match the hull and there shouldn't be a gap between it and the hull where it could deflect down, or rather the gap is filled with the foam. Perhaps they forgot the foam when assembling the boat, which would explain how the tank bent and cracked.

Superglue does not bond well to HDPE. I would also go with plastic welding, although it's a bit of a tricky spot. Might help if you cut the glass tabbing, lift the tank off the hull a bit for easier access when welding. This would then also allow you to spray foam underneath the entire area before bedding it back down and glassing it back in.

artemis · « **Reply #7 on:** February 02 2021, 14:23 »

I don't know I think I would bite bullet and order a new tank rather than risk a leak mid ocean try contacting these lot for a price I know they have already done some Bavaria tanks.

https://www.tek-tanks.com/

Rgds
Mike

ICENI · « **Reply #8 on:** February 02 2021, 15:43 »

A friend of mine had a leaking fuel tank on his Bavaria sailboat.

He ordered a replacement tank and it sadly took ages to arrive from Germany. It ruined his cruising that year!

Dory to depress you but thought if you need to order a new one, you would be forewarned!

tiger79 · « **Reply #9 on:** February 02 2021, 16:41 »

As replacement would no doubt involve a massive amount of dismantling, I think I'd be tempted to try a repair first.

Markus · « **Reply #10 on:** February 03 2021, 06:14 »

If I am looking at the picture correctly, the crack is partially below the tank. And as it's caused by the bending of the tank, the crack will probably continue to propagate further if the cause is not fixed. Therefore I would just disassemble to lift the tank enough to do a proper weld and add PU-foam below the tank. I also usually find it that every hour spent on disassembling is two hours less work doing the actual job - applies to both cars and boats...

Narragansett · « **Reply #11 on:** February 05 2021, 02:02 »

I have the same boat, a 2006 33', and the exact same problem. Am preparing a plastic weld repair in the spring, but wonder if this is a more common problem than just these two boats?

Yngmar · « **Reply #12 on:** February 05 2021, 19:14 »

That looks like a pretty clear stress crack from the tank bending. Perhaps Bavaria had a PU foam shortage!

Here's a photo from a yard tour, where you can clearly see the bright yellow PU foam sticking out from under the diesel tank. Although it doesn't go all the way back either, so perhaps they did have problems with the foam running forward along the curved hull or something?

The photo also tells you that the tanks went in before any of the interior and will not be so easy to remove entirely $:-\$

Narragansett · « **Reply #13 on:** February 07 2021, 22:26 »

Very cool photo Yngmar. But in it the foam seems to stop well forward of the area where these stress fractures are occurring. My 2006 33 also has the foam further forward between hull and tank, but none aft, where it seems these ruptures occur, and where the hull is likely to see more stress and movement, as the result of waves or poorly placed lift straps.

So the question post-repair becomes, should I add foam all the way back and make a positive connection between hull and tank? From my discussions with the US Bavaria rep, it is clear these 150 liter tanks were tucked into a wide range of yachts to avoid having to produce multiple sizes of tanks, and the shorter boats, like the 33 are now experiencing these ruptures. (Your picture seems to show a 40-ish looking hull). Would having foam that directly connects hull and tank increase the stress on the tank, or distribute it more evenly to avoid repeated ruptures?

Steve

Markus · « **Reply #14 on:** February 08 2021, 06:59 »

Fully agree with Yngmar that there's probably been not sufficient support for the tank. That combined with the shape of the tank creates a "hinge line" where the tank has ruptured. I bet if either the support was ok or if the tank cross section did have a chamfer rather than that 90 degree inner corner at the top it would work fine. Maybe it would be best to put PU foam only to the right of the "hinge line" to be sure it does not break again when boat is deflected in lifting, etc...?

Edit:
Second thought: the tabbing at the upper end of the tank creates a rigid attachment point at this end which is not good. Maybe it would be best not to re-tab after repair but to strap down the tank from the middle section.

Narragansett · « **Reply #15 on:** February 08 2021, 16:47 »

Good point about that tab. I'll be making the repair with the tank (emptied and vented) in place, thanks to great access via that huge hatch to the rear of the starboard locker, but in these shorter boats that tab looks like what might be torquing the tank at exactly that point when the stern shifts, from wave action, lift straps or even the pull of a backstay. So maybe chisel the tab off, and bring foam to that hinge line? Then strap the tank midway to the bottom of the locker?

Yngmar · « **Reply #16 on:** February 09 2021, 11:24 »

I'm pretty sure the tank is supposed to be bedded on foam over the entire area resting on the hull. PU foam is fairly flexible and will absorb stresses from tank expansion, deflection (when filled) and hull flex. The foam is however quite runny before expanding, so I think the missing foam is due to it running down along the hull when it originally was installed and not intentional.

It needs to be tabbed on so the ~130 kg of a full diesel tank do not break away in rough seas or in case of a knockdown - it would easily smash through the furniture if it came loose.

Markus · « **Reply #17 on:** February 09 2021, 12:56 »

Personally I would have no problem just using a sufficient number of quality straps. Of course the mounting points need to be robust as well. It's a bit difficult to tell from the photo, but if you want to tab, how about tabbing from the center of the tank to avoid connecting the "weak end" of the tank rigidly to the hull. Of course after putting PU-foam under the tank to make sure it is not supported only at the far ends...

Narragansett · « **Reply #18 on:** February 11 2021, 22:04 »

Another piece of the puzzle. This picture is from a 2005 Bavaria 36, courtesy of another poster here. The tab at the rear seems to have been cut away, then PU foam added beneath a good portion of the rear of the tank, and then a smaller piece of matting glassed back over the end. The owner (since 2015) has not reported any problems with the tank. Does that PU foam pad look factory installed or would you say it is an attempt to address the sort of problems that I and a few other folks here have experienced?

Narragansett · « **Reply #19 on:** February 25 2021, 23:07 »

So, plastic weld complete--not pretty, but not visible either. Would like to do a basic pressure test before refilling tank--considering soapy water on the patch and pumping air in via: bicycle tire pump/dinghy foot pump/shop vac? Anyone done a DIY pressure test?

And finally a photo of the underside of the tank. As you can see the tank sits on two fairly small dollops of PU foam, and the last two-thirds of the tank are completely unsupported until it terminates with the glassed over cap. That this tank twisted and ruptured is no surprise, or shouldn't have been. Am leaning toward pouring a couple of quarts of two-part 6 pound PU foam in the center and then back at the end--tips on how to avoid putting unnecessary pressure on the tank when the foam expands?

Been putting to good use all the advice here, thanks.

Steve

SYJetzt · « **Reply #20 on:** February 26 2021, 10:53 »

Great job, well done

Ronald · « **Reply #21 on:** February 26 2021, 11:19 »

Narrangansett

Slightly of topic but looking at the picture you shared on the question foam added or not.
I noticed that the exhaust of the heater runs underneath the filling lines of the tank. And leaking liquid has a chance the land on the exhaust drain de layer and catch 🔥.

Not sure if it you boat but I would not like this set up.

RGDS Ronald.

sy_Anniina · « **Reply #22 on:** February 26 2021, 13:58 »

Look at different types of PU foam at local well-stock hardware store. I have seen some low-expansion foam types im my local store, planning to use them on fridge insulation improvement Job.

BR,

Tommi
s/y Anniina

joerg.rau · « **Reply #23 on:** May 16 2023, 09:13 »

@Narragansett your post and your fix is now some years ago. We have the exact same problem at the exact same position. Could you please explain how you did the plastic welding? Also, did the fix last over the years?

Narragansett · « **Reply #24 on:** June 14 2023, 21:51 »

I used a mid-range plastic welder from Harbor Freight. I emptied the tank and used my electric dinghy pump to suction fumes from the port with the sensing unit out of the boat. I did not use the stainless mesh patch that came with the kit and after melting the split together with the iron I covered the seam with the plastic welding rods that came with the iron, which I learned later were LDPE. All to say that the repair lasted until my final very vigorous sail last season. I will be repairing with West Systems G Flex 655 and diapering the hull below the area with Sorbent pads for this season until I find the time and fortitude to replace the tank. Will be putting a smaller tank directly above the current 150 liter (am leaving it in) and then adding a plywood floor above that. Crappy tanks for sure but enough room in that huge locker for some improvisation. It was a bit nerve wracking applying heat to the fuel tank and I could not find a professional who would touch it, and I will not be doing it again.