Leaking Diesel Tank Vol II

[chas]

Thank you to all who advised me on how to repair the 1/2 inch by 1/4 inch hole in the bottom of my mild steel diesel tank. Although I can (just) manovre the tank in the cockpit locker, it is too large to come out though the lid. Armed with this advice, I went down to the boat and re examined the situation. I first spoke to a couple of welders who were very unwilling to attempt a repair because od the constrictions of the locker and the fact that diesel had leaked into the bottom of it and the fumes could still be smelled. I tried the sealed 'penny washer' suggestion but the ergonomics of tank and locker make it impossible to reach both sides of the hole and, whatever I did, I could not get a nut on the bolt.

This left the patch idea. As I am reluctant to drill and tap more holes in the tank to bolt a patch on, it ocurred to me that I might be able to glue one on? I know that several people advised against filling the hole with propriety gunge, but does anyone know of a glue that would hold a mild (or stainless) steel patch over the hole? I have good access to the outside of the hole so could get the surrounding area very clean and, if necessay, rough it up a bit with a grinder.

I have had a good look at the tank and apart from this hole, the remainder is remarkabley sound for a 30 yr old mild steel tank, so I think it is worth trying to keep it.

I would be very grateful for any advice on an appopriate gluing solution.

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[cliff]

Bugger that! - using glue I mean!.

IF as you say the hole is 1/4 x 1/2" then drill the hole to 1/2" dia or 9/16" if necessary, thread the hole then fit a brass (or steel) plug with a copper washer.

Alternative is to tap the hole BSP and fit a tapered plug with sealant (PTFE tape works fine with diesel)

Nice neat job and no "extra" holes.

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[Evadne]

I've only indirect experience but I think epoxy would work, providing as you say all was clean and degreased (acetone is good here).

I have used a tank (petrol) that was mended "temporarily" with araldite some years previously, in that case a blob and a smear over a pinhole. "Plastic metal" is nothing more than a metal loaded epoxy, and it sticks to steel like the proverbial, especially if you want to get it off! Similarly with car filler. The main question is how how well the epoxy resists diesel.
If it were me, with no other options, I'd apply a patch of mild steel with a bed of epoxy and monitor the condition of the patch at regular intervals for leaks (possibly forever more). It's got to be a better first option than deciding which bit of boat to cut a hole in big enough to put in a new tank and/or extract the old one IMO.

Incidentally I don't want to tell you something you know, but would it be easier or possible to put a bolt in place (using one of those belden cable type of pick up tools and put the nut on from the outside through the filler pipe? You might also consider cutting an "inspection plate" in the deck or wherever to give you access to the top of the tank to put a nut/bolt in. I had to have one on my after deck in order to remove the rudder stock. Messy, but maybe more permanent than a glued patch and less work than fitting a new tank.


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[david_bagshaw]

Assuming you can get to the area from the outside, and the hole is not too near the edge

Fit a tank flange, ie you cut an oval then fit a bigger oval with studs on it through the hole & bolt another similar on the outside, with jointing cpd etc,
Will be stronger than the original bottom

Have done this in the past & it works


Good luck





<hr width=100% size=1>David
<A target="_blank" HREF=http://www.euroboating.net>http://www.euroboating.net</A>

 

[chas]

Thats a good idea - thanks

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[chas]

Thanks - good to hear someone with good experince of epoxy. It might work but the repair will be at the bottom of the tank, tank strapped in with a false floor on top and the usual things you find in a cockpit locker on top! I have an inspection hatch but as it is on top of the tank and the hole is near the edge furthest away and with the tank tipped up in the locker, I would have to be a snake with a hand at each end to reach both sides of the hole - even with a cable thing!


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[chas]

Good idea - thank you. As I cant get to the inside (reasons above) I would have to weld the nuts onto the inner piece. I will investigate.

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[Evadne]

I know how you feel. With cars they refer to "coathanger components" that are put on a coathanger at the start of the line and the rest of the car is assembled around them. I think that's what you have here. I also mended leaking external oil lines on the Yanmar as a "get you home" by smearing with epoxy (isopon), and it lasted the rest of the season, until I could get new ones.
David Bagshaw's suggestion of an oval (or rectangular?) hole so you can insert the plate into the tank through the hole is a good one that I've not come across, I'll have to store that away in case it comes in handy. It should work with a square patch as well.

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[david_bagshaw]

Tap threads into the inner plate and run bolts through the threads, then no welds are needed.

by using an oval or oblong plate the inner plate can be put through the hole and aligned through the bolt holes, without the need to work from the tank top etc.

<hr width=100% size=1>David
<A target="_blank" HREF=http://www.euroboating.net>http://www.euroboating.net</A>

 

[david_bagshaw]

wont work as well with a square patch, as the plate inside needs to be bigger than the hole, so by making the hole rectangular / oval you can get a much bigger than the hole plate through the hole.


with a square hole you are limited to the half the difference between a side and the diagional for the edge margin





<hr width=100% size=1>David
<A target="_blank" HREF=http://www.euroboating.net>http://www.euroboating.net</A>

 

[tugboat]

This sort of thing really pees me off! Boat owners shouldn't have to cope with this sort of problem - it's bad design/ construction by people who obviously don't intend to own such a boat themselves. Bring back the stocks. Public flogging. Name and shame. National service. What? Alright nurse, I'm coming. /forums/images/icons/crazy.gif

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