How to replace fuel tank?

[mvweebles]

Originally Posted by massnspace

Why such a bad idea?

If the new glass is scarfed in properly with a 12:1 feather (or more), and epoxy is used, I am thinking it will be very strong. Especially if one could also add some heavy biaxial tabbing (as much as possible) to the inside. And of course add thickened epoxy to fill the gap between the cut core when rebuilding….

Of course it would be weaker, but that area of the hull is not subject to high loads. Of course a whale of something could directly hit it, but the chance of that is so minimal….and if that happened I would argue a normal hull would break anyway….

So, you can't get the tank out, but there's room to structurally reinforce the inside of the hull with the new tank in place? Type/brand of boat is relevant - how it would used re:hull flexing, coring, etc.

Sounds like a plan. What could possibly go wrong?

[NYSail]

If the manufacturer is still in business call and see if they have recommendations.

[Ballsnall]

40 year old OEM aluminium tank, strip the interior and replace it or walk away.

Probably already leaking, just the owner has rags stuffed in all the holes and listed at an attractive price to unload fast.

You could open the hull and flange the opening with G10 to make a backing plate for hull cutout to be epoxied in from the outside then do the 12/1 join from the outside. Stronger than original.

[Tin Tin]

You say it is under the settee. Cut the top of the settee off. What is under the settee cushion? A photo would be helpful.

[c.K.]

Originally Posted by mvweebles

Unless the boat is metal, that's a really, really bad idea. If it's metal, it's only a bad idea. There is simply no way to get the hull adequately reinforced.

Common way is to cut out old tank as previous poster said. Replace with multiple smaller tanks and/or live with reduced tankage.

A well installed and maintained tank will not leak for a very long time. Typical death is from deck leaks, either teak decks or from around fill neck. If neither of those are present, you may be okay.

Hey
my boat is 40 years old as well with aluminum fuel tank but you can also think if not broke don't fix it

[boatpoker]

Originally Posted by mvweebles

Unless the boat is metal, that's a really, really bad idea. If it's metal, it's only a bad idea. There is simply no way to get the hull adequately reinforced.
.

Not uncommon on Grand Banks and can be done well.

[mvweebles]

Steve D'antonio is a well respected marine inspector who was yard manager at Zimmerman Marine in Chesapeake Bay for several years. Interesting perspective from him:

https://stevedmarineconsulting.com/n...r/?print=print

[i] I’ve replaced scores of fuel tanks in all manner of power and sail vessel in my career.* In no case have I ever cut a hole in the hull of a fiberglass vessel to do so, and that’s no accident.* While that may have been easier in some cases, the risk it poses of compromising the integrity of the structure, through secondary bonds in a stressed structure that experiences slamming loads, is simply too great.* The alternative may require some ingenuity on the part of those undertaking the work.* I’ve removed engines, and cut existing tanks into pieces and replaced them with multiple tanks designed to fit through available access.* I’ve also cut small holes in cabin tops, through which crane cables were lowered, to lift engines out of the way, and then slide them out on temporary dollies, or poked the boom of a crane into the cabin to lift an engine in that fashion.

Finally, cutting a hole of this size in an FRP hull is not only ill-advised, it may affect your insurance coverage. My strong recommendation would be to find a yard with the experience and expertise needed remove and replace the tanks without compromising the hull.

[massnspace]

Originally Posted by mvweebles

Steve D'antonio is a well respected marine inspector who was yard manager at Zimmerman Marine in Chesapeake Bay for several years. Interesting perspective from him:

https://stevedmarineconsulting.com/n...r/?print=print

[i] I’ve replaced scores of fuel tanks in all manner of power and sail vessel in my career.* In no case have I ever cut a hole in the hull of a fiberglass vessel to do so, and that’s no accident.* While that may have been easier in some cases, the risk it poses of compromising the integrity of the structure, through secondary bonds in a stressed structure that experiences slamming loads, is simply too great.* The alternative may require some ingenuity on the part of those undertaking the work.* I’ve removed engines, and cut existing tanks into pieces and replaced them with multiple tanks designed to fit through available access.* I’ve also cut small holes in cabin tops, through which crane cables were lowered, to lift engines out of the way, and then slide them out on temporary dollies, or poked the boom of a crane into the cabin to lift an engine in that fashion.

Finally, cutting a hole of this size in an FRP hull is not only ill-advised, it may affect your insurance coverage. My strong recommendation would be to find a yard with the experience and expertise needed remove and replace the tanks without compromising the hull.

There are no “slamming loads” on a sailboat hull midships near the keel. That’s where the tank is.

[massnspace]

Originally Posted by c.K.

Hey
my boat is 40 years old as well with aluminum fuel tank but you can also think if not broke don't fix it

Not broke. But what happens if it breaks. That’s my question.

[massnspace]

Originally Posted by mvweebles

So, you can't get the tank out, but there's room to structurally reinforce the inside of the hull with the new tank in place? Type/brand of boat is relevant - how it would used re:hull flexing, coring, etc.

Sounds like a plan. What could possibly go wrong?

Yes, the tank can’t come out (easily), but it could be possible to add biaxial tape on the inside of the hull on the edges of the tank footprint.

[massnspace]

Originally Posted by Tin Tin

You say it is under the settee. Cut the top of the settee off. What is under the settee cushion? A photo would be helpful.

The tank is large. One would have to do much more than cut he top of the settee off. And dont forget the floor, subfloor and stringers would also have to be cut through.

[skipperpete]

Originally Posted by massnspace

Why such a bad idea?

If the new glass is scarfed in properly with a 12:1 feather (or more), and epoxy is used, I am thinking it will be very strong. Especially if one could also add some heavy biaxial tabbing (as much as possible) to the inside. And of course add thickened epoxy to fill the gap between the cut core when rebuilding….

Of course it would be weaker, but that area of the hull is not subject to high loads. Of course a whale of something could directly hit it, but the chance of that is so minimal….and if that happened I would argue a normal hull would break anyway….

I agree with avoiding cutting the hull out below the waterline. I did a similar thing on a Hatteras to extract a pair of deceased 8v71 detroit diesels ….but ABOVE the waterline and I was able to work on both sides to glass in the huge cutout and the stringers on the inside. I think it would have been incredibly difficult to do this job under the boat and with no access to the interior, half of my glass work was on a similarly scalloped foot wide join along the diamond saw cut line on the interior of the hull.

[mvweebles]

Originally Posted by massnspace

There are no “slamming loads” on a sailboat hull midships near the keel. That’s where the tank is.

Not sure what you mean - sailboats pound all the time, but no matter. Sounds like you've made up your mind. Best success on your purchase and repair.

[massnspace]

Originally Posted by mvweebles

Not sure what you mean - sailboats pound all the time, but no matter. Sounds like you've made up your mind. Best success on your purchase and repair.

Incorrect.

The area of the hull that is way underwater amidships near the keel never comes out of the water. So no pounding there….

If the tank were in the bow I would agree with you. But it is not.

[mvweebles]

Originally Posted by massnspace

Incorrect.



The area of the hull that is way underwater amidships near the keel never comes out of the water. So no pounding there….



If the tank were in the bow I would agree with you. But it is not.

Well, most power boats have saddle tanks. Well aft of any pounding.

You've convinced yourself this is a good idea. I wish you well. You may want to ask folks about resale - how many would see this type of repair as a serious defect causing them to either walk away or seek a significant discount. They would need a surveyor with the same attitude as Boatpoker vs Steve D'antonio