37c holding tank questions, please help

[Cocoa Beach Sailor]

Hello, I have just acquired Jolly Rodger a 1984 Cherubini Hunter 37 cutter and have read the threads concerning holding tank leakage. I am wondering what percentage of the volume underneath the shower seat is taken up by the original holding tank. My thought is to build a tank with Plywood And fiberglass epoxy to use the entire volume of the area underneath the seat. I have done a good bit of glass work and epoxy fiberglass is a very low permeable thing even though plywood not so much. Fiberglass would be on both sides of the plywood tank. Any guesses as to the total volume underneath the seat if I were to cut the entire top section off such that I could lower the tank into position? Thank you very much. The boat was purchased while on the hard and I'm looking forward to getting her back in the water! Regards, Terry

 

[Peggie Hall HeadMistress]

What is the existing tank made of? Do you see any signs that it's leaking, or do you just want a larger tank?
Shower seats usually fold down over the toilet...so where is the toilet on this boat? What size is the boat?

--Peggie

 

[Don S/V ILLusion]

Have you considered what happens to a glassed wooden box when it flexes when boats move?

 

[Cocoa Beach Sailor]

What is the existing tank made of? Do you see any signs that it's leaking, or do you just want a larger tank?
Shower seats usually fold down over the toilet...so where is the toilet on this boat? What size is the boat?

--Peggie

Sorry, I thought this was posted in Hunter 37 cutter. Oe tank stainless, 1984, and they are known to leak. Separate shower, tank is under seat. Given their propensity for linking, I would rather replace it before it starts! I will be building a bit larger tank as the factory one is only 5 gallons and I hope to double or triple that.

 

[Cocoa Beach Sailor]

Have you considered what happens to a glassed wooden box when it flexes when boats move?

I would imagine that tank flexes also, just like the dingy I built with regular exterior plywood, glassed both sides, if the tank was built into the hull. But given that the tabs holding tank will be of epoxy glass, I would think they would absorb the great majority of flex, unless I make them an inch thick. My notion is exterior plywood 1/4" glassed both sides, with several layers on the inside and several coats of epoxy, each being laid whilst the previous coat is still tacky.

 

[Peggie Hall HeadMistress]

I suspect that you can buy a top quality 10-15 gal plastic tank for the same or very little more than it will cost you to make a fiberglass tank. Check out Ronco Plastics Ronco Plastics marine Tanks Ronco Plastics marine Tanks
They make TOP quality thick-walled (50% thicker than most other mfrs) water and waste tanks for a very reasonable price and have more than 400 shapes and sizes, over 100 of which are non-rectangular, and they install fittings--including diptubes--in the sizes and locations specified by the customer when they make the tank. There are retailers who sell Ronco tanks, but Ronco sells direct for a much lower price...and they're great to work with.

When looking at drawings it's important to know that there is no top or bottom until the fittings go in, and YOU decide where they go. So rotate, flip in any orientation to find the tank that fit your space. You might find one that fits an even better location.

--Peggie

 

[dlochner]

A cubic foot is just under 8 gallons.

 

[Jim Legere]

Sorry, I thought this was posted in Hunter 37 cutter. Oe tank stainless, 1984, and they are known to leak. Separate shower, tank is under seat. Given their propensity for linking, I would rather replace it before it starts! I will be building a bit larger tank as the factory one is only 5 gallons and I hope to double or triple that.

The OEM tank was worse than stainless steel - it was aluminum! They all leak but they're relatively easy to remove (by cutting up the tank rather than the shower seat!). Lots of info here on SBO about removing / replacing the tank. If you want more volume, the usual route is to install a tank, custom or off-the-shelf, in the space under the V-berth.
Hunter 37-cutter Owner Modifications and Upgrades
Hunter 37-cutter Owner Modifications and Upgrades
Hunter 37-cutter Owner Modifications and Upgrades

 

[Peggie Hall HeadMistress]

If you want more volume, the usual route is to install a tank, custom or off-the-shelf, in the space under the V-berth.

The v-berth is my favorite holding tank location, but only if the head is forward of midship. Most manual and electric toilets can only move bowl contents about 6 linear feet in the length of time anyone wants to keep pumping or leave their finger on the button without more help from gravity than is available on most sailboats, making the hose run from a head that's aft in the cabin longer than any manual and many electric toilets to the v-berth impossibly long.

Btw...a flimsy off-th-shelf rectangular cube or an expensive custom tank aren't the only alternatives to building a fiberglass tank. See post #6 in this thread.

--Peggie

 

[Cocoa Beach Sailor]

I suspect that you can buy a top quality 10-15 gal plastic tank for the same or very little more than it will cost you to make a fiberglass tank. Check out Ronco Plastics Ronco Plastics marine Tanks Ronco Plastics marine Tanks
They make TOP quality thick-walled (50% thicker than most other mfrs) water and waste tanks for a very reasonable price and have more than 400 shapes and sizes, over 100 of which are non-rectangular, and they install fittings--including diptubes--in the sizes and locations specified by the customer when they make the tank. There are retailers who sell Ronco tanks, but Ronco sells direct for a much lower price...and they're great to work with.

When looking at drawings it's important to know that there is no top or bottom until the fittings go in, and YOU decide where they go. So rotate, flip in any orientation to find the tank that fit your space. You might find one that fits an even better location.

--Peggie

Thanks for the info, I had heard of them and when I looked at a tank it was just over $100. Two of my personal shortcomings work against me in this. The first is saving money. I have more time than money and so building my own will still be cheaper by 30 or $40. The second is my obsession with using space. I will probably line the space with neoprene rubber from wetsuits and then place plastic over that and then lay epoxy saturated cloth over that so that the tank will use every bit of space available. I'm trying to get an idea how much volume and total there is underneath that seat since I am not near my boat and won't be for quite some time and I am trying to organize projects for when I do get back to her. My understanding is that epoxy and fiberglass have a very low degree of permeability. I will probably coat the still tacky cloth with several layers of brushed on epoxy.