Replacing the diesel tank - CD36

[David van den Burgh]

Just before launch we discovered that Ariel's diesel tank had developed pinhole leaks in the bottom. I ordered a custom tank from Luther's Welding in Bristol, Rhode Island. The pricing was fair, the service excellent, the tank a perfect fit, and the workmanship superb. Even with shipping the price was cheaper than local fabricators. If anyone is ever in need of tankage, you might do well to give them a call.

Pictures of the tank and installation to follow.

[Russell]

Very curious to hear more about this. No problems with my tank to date, but its one of those things I feel like could become a problem any day. 30 year old aluminum tank that sits in the bilge cant last forever. What did you make the new tank out of?

[Jim Walsh]

Luther's made my replacement tank a couple years ago. I brought them my old tank to use as a pattern and had them weld on an "L" bracket to make it easier to install and provide a more secure attachment point than the teak bracket which held it in place originally. They really are a great outfit to work with.

[David van den Burgh]

I haven't taken any pictures of the new tank installation yet, but I wanted to answer Russell.

Our diesel tank - Ariel is hull #7 - is located in the port cockpit locker on a shelf at the forward end of the locker. Contrary to what is printed in the CD manual, Ariel's diesel tank was 30 gallons, not 43. It was made out of 5052 1/8" aluminum and secured to the forward locker bulkhead with two aluminum straps. I discovered the leak in the old tank when one of the marina yard workers hollered at me for pumping diesel on the ground during my spring commissioning. Naturally, I told him he was crazy and that there wasn't anything in the bilge but a little water. I was wrong.

After I confirmed the location of the leaks, I used a reciprocating saw to cut the tank into four sections small enough to fit through the cockpit locker opening. The original tank was 14" wide and the locker opening is 12.5" so there was no way to get it out in one piece. The cause of the leak was pitting in the bottom of the old tank that had eventually worked its way through, presumably caused by condensation over the years (yes, we have a fuel/water separator and do our best to keep our tank clean and full). Essentially the tank had weeped diesel onto the shelf on which it was mounted for part of the winter months, eventually dumping about 5 gallons of fuel into the bilge.

I seemed to recall reading about CD owners who cut their cockpit locker opening to fit a new tank, but I was not at all interested in that route, so I designed a tank that would drop through the opening and still provide a reasonable amount of fuel. I drew up a design and sent it to Luther's. I requested an additional port to accommodate the fuel polishing circuit, which Luther's added without charge. I also did my best to locate the fittings as close to their original locations so I could drop the tank in and reconnect things without having to make modifications. All three of the fuel fittings have draw tubes to minimize the chance of introducing air into the fuel pickup.

When I installed the new tank my initial plan was to reuse the aluminum straps that secured the old tank by adding shims to account for the narrower dimensions. I quickly scrapped that idea and bought 1/8" flat aluminum strapping and bent up two straps that conformed to the new tank width.

The new tank is 24 gallons, which is plenty for Lake Michigan. I dropped it in and plumbed it in a couple hours. It was necessary to move the exhaust hose temporarily from the inboard side of the cockpit locker in order to make room for the tank to slide in. I'm very pleased with the quality and finish. It matches my supplied dimensions exactly.



Let me know if you have any questions.

[Steve Laume]

I had nearly identical problems with Raven's fuel tank. I managed to catch the weeping before it did anymore than slightly seep onto the plywood shelf. I had planned to take the tank out to clean it, a few years ago, when I discovered the problem. I also needed the reciprocating saw to remove the old one and had the new one made 1 & 1/4" shorter to be able to get it back in. I went from 20 down to 18 Gal.

The point I wanted to make was the preparation of the shelf for the new tank. I cleaned the diesel staining off the shelf and painted it to seal things up. Then I bought a heavy rubber door mat that had a cut out grid pattern on it. I cut the door mat to fit the self and set the tank on top of it. The mat is about an inch thick so it pretty much made up for the decrease in tank height. It allows for very good air flow under the tank so it doesn't stay wet under there anymore. I found that all the degradation of my tank was on the outside and it was the bottom where it sat on the unsealed plywood that started to pit.

The plywood acts as a sponge for any salt water that ever found it's way into that locker, Steve.

[David van den Burgh]

Steve,

If I'd had more time, I would have put some sort of grid under the tank to keep the bottom dry and ventilated, too. The pitting in our tank clearly began inside, however, so I'm not too concerned. We're also sailing in fresh water. If I get motivated to pull the tank again, I'll probably glass the shelf and lip to prevent diesel (or water) from ever finding its way back into the bilge. At that point I'll probably mount the tank atop a grid for ventilation. We did manage to get thirty-three years out of the original tank, so....

[Jim_B]

I replace my tank this past fall. It is in the bildge and required cutting the sole, subfloor and 2 stringers.

It was replicated in aluminum at a local shop (cost ~$500). It easily holds 43+ gallons and was removed in one piece. I re-installed the stingers with check-blocks and thru bolts and cut the sub-floor/sole into 4 removable pieces. Now it is easy to get to the entire bilge area. The new tank has 2 access points if needed for future cleaning.

One key learning was the tank is wedge shaped so its capacity isn't linear. Upon refilling with fuel I recorded the mechnical gauge readings in 5 gallon increments. When the gauge shows 1/4 tank there's less than 5 gallons in remaining.

[hilbert]

I also noticed diesel drops from pinhole leaks on the bottom of the fuel tank. Most people of sound mind would look for a replacement tank to drop in with minimal fuss (sigh..., not I).

I found a 1/8" aluminum 5052 universal 11 gallon tank from Boyd Welding (http://www.boydwelding.com/shop/index.p ... t-cap.html). Dave Boyd agreed to modify the dimensions so that it would fit through the cockpit locker opening and add a drain fitting for no additional charge. The tank has tabs that allow mounting away from any contacting surfaces. I took this opportunity to remove the external overflow tube and replaced it with a thermal relief rollover vent, that does not allow liquid to pass. I also got rid of the deck fill and the possibility of water intrusion through o-ring seals. The fill is now a 3" flush aircraft style cap that is just large enough to get a hand inside (and hopefully out again). Access to the fill is though the seat cover.

[gates_cliff]

When I bought my CD 27, almost 5 years ago (my time flies) I had it surveyed and one of the issues found was that the fuel tank needed to be replaced. So before putting back in the water, I took the old tank out, measured it carefully including all holes, took pictures and sent the information to Speedytanks in New Jersey. The price was less than $400 for the tank and necessary fittings, not sure if it was a good deal or not but at the time I thought it was ok.

Anyway, they sent me an exact replica. The surveyor suggested I add something to the bottom so that it wouldn't sit directly on the wood base which would collect water and contribute to deterioration. So, I got a PVC board and ripped some 1/2" X 1/2" strips and used 5200 to attach them to the bottom of the tank. There was enough space that I only needed a little woodwork to make it work. I thought it might be a good idea to provide some "chafe" protection at the top and side so I put some split pipe insulation over the wood that held the tank in place. In addition, I needed to reglass the bulkhead that held the tank in place, while waiting for the tank I reglassed the bulkhead. Found that Cape Dory had only put one layer of fiberglass cloth to tab it to the hull. I went ahead and applied 3 layers, so I know it's sound. I installed new hoses and reconnected everything. I'm no diesel mechanic so I paid for Vosbury Marine in Annapolis to come over and check my work and to dewinterize the engine. They approved my work.

To get insurance from Boat US, I had to supply the survey. Before they would issue the policy the bulkhead retabbing and tank replacement had to be completed. So I took some pictures and asked the surveyor if he would go to the boat and certify that work was done ok. He was nice enough to check it one day when he was at the yard doing another survey and didn't charge me for another trip. Sbumitted the photos and surveyor's follow up email and got the insureance.

Fortunately, for me, the tank came out and went back in through the port cockpit hatch. Now, doing the work down there did require my contorting my aged body into positions it wasn't inteneded (at this age anyway) but I was able to get it done, along with some aching joints!!!!

I would recommend Speedy Tanks, they were very helpful and provided exactly what was needed. I didn't do a lot of price comparison so not sure if the price was out of line or not.

[Bob Ohler]

This has to be one of the best threads I have seen on this board in a long time!

Let's see some more project photos and write-up's!

Fair winds,

[gates_cliff]

Thanks Bob. I had a little lull at work and thinking about sailboats is lot more fun than what I usually do, so it was a nice little mental hiatus. I'm at work and don't have access to photos but I believe I still have picutres, I think. Right now my internet is down right now at home, so will have to wait a day or 2. Once it's corrected and I think of it ( ) I'll add some.

[gates_cliff]

Oops, I think Bob was referring to hilbert's report and not mine! LOL

I like hilbert's a lot better anyway, I need to add a second fuel filter as well.

[Bob Ohler]

Actually, I was referring to all projects on Cape Dorys!