Alden Caravelle -Fuel Tank - Tank top

[TaborKP!]

Hello,

Hoping another Alden owner can share any relevant experience with this issue for similar construction details. Wind Song is a 1965 European constructed Caravelle. Last year, I had the fuel tank opened and mucked out as a preventative maintenance activity. Who knows how long it had been, internals were in good shape, minimal muck. A new “tank top” was fabricated and bolted down, as the previous one was a bit deteriorated. However, quite a bit of water in the tank end of season, we believe some water leaked into the tank from the tank top last season, as the surface is very uneven between studs. Leaking stern tube, being replaced this year... The construction detail appears as to be a mild steel frame, with the threaded studs attached, which is glassed in around the perimeter of the tank.

We think the mild steel is starting to corrode and swell, making for a very uneven surface between studs, and now difficult to seal, even with an adequate gasket. It is hard to see in these pictures but wanted to provide some background.

Has anyone else had similar experiences, how did you resolve? Trying to avoid a major job extricating the mild steel frame for time being….?

Thanks TaborKP

 

[TomY]

Hello,

Hoping another Alden owner can share any relevant experience with this issue for similar construction details. Wind Song is a 1965 European constructed Caravelle. Last year, I had the fuel tank opened and mucked out as a preventative maintenance activity. Who knows how long it had been, internals were in good shape, minimal muck. A new “tank top” was fabricated and bolted down, as the previous one was a bit deteriorated. However, quite a bit of water in the tank end of season, we believe some water leaked into the tank from the tank top last season, as the surface is very uneven between studs. Leaking stern tube, being replaced this year... The construction detail appears as to be a mild steel frame, with the threaded studs attached, which is glassed in around the perimeter of the tank.

We think the mild steel is starting to corrode and swell, making for a very uneven surface between studs, and now difficult to seal, even with an adequate gasket. It is hard to see in these pictures but wanted to provide some background.

Has anyone else had similar experiences, how did you resolve? Trying to avoid a major job extricating the mild steel frame for time being….?

Thanks TaborKP

Huh. Are you sure the tank top frame is mild steel? How could they have sealed that to the hull let alone secure it?

My Challenger fiberglass hull was laid up at the Halmatic yard in the UK (1960). The tank tops are 1/4" (I think) mild steel plate. Like your's they bolt to the flange which I'm sure is fiberglass in my boat.

I've never removed the tops in 22 years. But you can clearly see the glass flange on the left and middle of the 4 lids(2 per side on my boat).

I've never had dirty fuel problems and have pulled samples out of the bottom, all clean. I've let the sleeping dog, lie,...

Halmatic used quite a bit of a fiberglass 'plate' like stock that I suspect was pre-formed. That material was glassed into the hull during construction.

Here is the 1/2" material used to build the ice box sump. In the photo, the bronze top is removed(the fiberglass top is tapped/threaded to fasten the top plate down to the glass flange/top.

The fiberglass material is glassed into the hull so as to be water tight (like the fuel tanks).

This is a mini version of my 80 gallon fuel tank: Top, ends, all glassed into hull and together. Plate bolts on top.

Here it is again (the 1/2" fiberglass ), fitted and glassed into the hull to form a bulkhead for the aft chainplate (and the mizzen mast step over the formed corner).

You can see the thickness of the material where an access was cut through. It's solid laid fiberglass, I know because I cut that access:

 

[jon hansen]

Tom's red fuel tank is located where my water tanks are. 2 fiberglass topped water tanks under the main solon table.

moving aft in the keel is then a deep well. bilge pumps, speedo, depth.

then ice box melt tank, in keel.

then under the floorboards, where one stands at the sink, alum plate
cover to an all fiberglass covered tank that is in the keel under the engine. the tank has baffels. the bottom is slanted towards the front. the cover is prolly 9"x19"

maybe a 28 gallon tank.

 

[jon hansen]

my water tanks were dropped in. the inside is gell coat. there is a gap between the bottom of the water tanks and the deep area of the keel bilge.

the fuel tanks are different. there are the area in the keel

i'm a fresh water boat. no rust issues.

i have a rubber gasket between the cover and the tank top.

could the studs for the cover be in a steel rim that is incased in the glass of the tank top. maybe. never looked that close. have had the top off maybe 3 times in 50 years

 

[jon hansen]

hi Tom, hi Tabor

i'm sure the inside of our keels are very different, Tom.

 

[TomY]

hi Tom, hi Tabor

i'm sure the inside of our keels are very different, Tom.

No doubt, Jon. I think his question is; how to seal his new top plate to the existing flange around his in hull fuel tank. KP thinks the surface of the flange is too rough for a good seal.

KP said; "However, quite a bit of water in the tank end of season, we believe some water leaked into the tank from the tank top last season, as the surface is very uneven between studs."

The above confuses me: If water got in through the seam between the newly installed top and flange, why didn't fuel come splashing out when the boat was heeled? Fuel tank nearly empty? Didn't heel last season?

 

[TaborKP!]

Thanks for comments, and Tom confirming details around construction materials, and pictures which would indicate to me this "Tank Top" is a solid GRP section, and studs threaded in. (Apologies if "Tank Top" caused confusion, this is common term for a structural section on ships which is the "top" plate on double bottom arrangements in engine rooms. I was not referring the the bolt access plate)

Yes have had same discussion around why no diesel leaked out sailing. Again, just exploring a theory. And was curious if other had similar swelling in way of stud penetration of the GRP. I am on the other coast from my boat, so have not sighted. But deformation is enough to be an issue in their opinion. Anyhow will have them "box up" (Singapore shipyard term), and fill to deck which should be adequate head to verify tank integrity.