New Diesel Tank!

The more I work on this boat the more I scratch my head in wonder: “why oh why did they decide to build [insert pretty much any part of the boat] in such a crappy way? I am learning that this applies to most boats too, save maybe for the really, really high-end ones.

Thirty-six years ago the Taiwanese boatyard that built Leela welded a black steel diesel tank, installed it in the mostly empty hull and built the boat around the tank. They also decided to wrap the tank in fiberglass for good measure. That way if moisture got in between the steel tank and fiberglass skin it would really get all the opportunity in the world to rot away at the tank from the outside. When we purchased Leela we knew the tank was a ticking time bomb. From all the research we could do online we knew that these tanks had a limited lifespan and ours was reaching the end of “typical” life. These tanks can rot and develop pin-hole leaks in two ways.

  1. From the inside: usually when sea water ends up in the tank and rusts away at the tank and welds. Signs of failure will be pinhole leaks usually in the lower part of the tank. We had our tank professionally cleaned in the fall and the inside of the tank came up with a clean bill of health.
  2. From the outside: over the years the tank can be exposed to water on the outside from many sources including a high level of water in the bilge. We know for a fact that at one point we saw a high enough level of water in the bilge that the lower section of it was sitting in the bilge water, and we assume some of the moisture would have remained between the steel and fiberglass

Earlier this year we did a major boat and bilge clean. After that big push the boat smelled OK for a few weeks but sure enough, it didn’t take long for the overwhelming stench of diesel to permeate the boat again. I was at my wits end. We decided it was time to bite the bullet, yank out the tank and replace with a new one.

The first task was to sawzall the existing tank out of there. On the project-fun-o-meter scale, this particular one ranks as a 1.5/10. It’s noisy, super smelly and a sawzall can really rattle your brain. I started by drilling holes in the top sheet of steel to give the saw access and just started cutting pieces out as I could.



Saxony DEEP in the bilge cleaning and scrubbing the gooey-dieselly-smelly muck below the previous tank. An area that had not seen the light of day in almost 40 years!
Saxony DEEP in the bilge cleaning and scrubbing the gooey-dieselly-smelly muck below the previous tank. An area that had not seen the light of day in almost 40 years!

As mentioned the shop where Leela is currently located in Bellingham is simply amazing. I walked 20 paces over to Bill’s corner. Bill is the resident welder. I showed him my project. At first, we thought we would make the new tank simple and rectangular to save costs and fit it in the companionway easier. And this brings up a very important point: part of the reason the existing tank had to be demolished to be removed is that it will not fit out of the companionway. They literally built the boat around the tank so no way to get it out. All Union 36’s are advertised as having 100 gallons of diesel capacity for true offshore potential. It wasn’t until our tank was out and we made measurements that we realized Leela never had a 100-gallon tank! 65 gallons at most. Discussing with Peter the previous owner this made a whole lot of unsolved mysteries over the years much clearer. All of our tank measurements were about 70% of the measurements posted online by another Union 36 owner. How can this be? Ours was an early model hull #4. Perhaps they adjusted the bilge in later production units? I know our headroom is quite a bit more than a hull #160 that I previously toured. Perhaps 3-4″ in height were added to the bilge in later hulls and this gave extra room for the diesel tank? I guess we will never know but I’m glad for the extra headroom!

I designed the new tank in SketchUp and found that the best we could do while being able to fit the tank through the companionway would be about 40 gallons. Not much, but heck we’ll strap on jerry cans when we need to. Bill went a bit crazy on our new tank, he said it was a very unusual and interesting project for him. And he charged us a really reasonable price too.

Our new tank in the making. A work of art!
Our new tank in the making. A work of art!

With this new tank, we were able to add a fuel level sender so we’ll finally be able to see how much fuel is left in the tank! Bill also added a bottom drain port just in case. Added bonus: the new tank location leaves about 4″ between it and the water tank also located in the bilge. We were finally able to add a drain valve on the water tank so we can periodically flush the water and clean the tank. Imagine that!

New tank in place
New tank in place
Finally all connected and floor structure above re-built
Finally, all connected and floor structure above re-built

The project is now complete. The new tank will last a very long time and gone are the smells (hallelujah!). Interestingly, we think the tank may not have had pinhole leaks after all. Upon discussing with Peter we think perhaps the inspection port gasket was not properly sealing the top of the tank. When the boat was heeling under sail some diesel would have leaked out and gotten stuck between the steel and outer fiberglass layer forever stinking the boat up. Oh well, we’re ecstatic with our new tank. It’s smaller size will force us to sail more and we love the sound of that. For those considering a similar project, the total cost of materials including tank and all new fittings was approximately $1,100 US.

7 Responses
    1. Emmanuel

      Thanks Christine! Fun project indeed. As for your boat, do you have big diesel smell in cabin? If not the tank is fine. Might want to double check the gasket for the inspection port is new and good to avoid the situation we had because once the diesel gets stuck between steel and outer fiberglass layer there is no way to get rid of that smell. As for volume yours will hold, I will send you a dimension drawing of the “proper 100 usgal” tank and you can compare if yours matches up. As mentioned, ours was shorter in every dimension except length.

  1. Emma

    Great job on this project!
    If I may ask, with what boat yard did you work to have the tank built?
    Did you cut any of the floor supports or any of the cabin sole, or remove any of the cabinetry on starboard to get the new tank in? Couldn’t tell for certain one way or the other.
    Where did you place the end of the vent hose for your tank, i.e, to the outside environment? It’s important to the ongoing health of your new tank.
    Some thoughts for you for why the tank was not as expected in size:
    -You point out inside cabin volume being different, thus overall tank height could be different.
    -You point out that you have an early hull, I’ve seen some of the early hull owners identify the boat as a “Union Polaris”. This could lead to a whole other thread on pedigree, but what’s important to note here is that until hull #111, the length of the boat was identified as 35.6, 35.7 or 35.8 ft. With hull #111 the length first reached at least 36ft (and maybe that is how many of us know and identify the boat as only Union 36). It was 36.2 or 36.3 ft, depending which data set you believe, and continued so until Andy’s boat Tilligo, which was back to 35.8ft. (By the way, where did you see hull #160? #156 was the last one I saw out.)
    -The depth dimensions are also sometimes different across the earlier hulls, and the tonnage varies some. The last hulls were almost consistent at a depth of 5’7 or 8″, again until Tilligo. Some of these things could be typos, but I don’t think all of them are.
    -The tank volume could be somewhat reduced as it appears original is not as far forward as later.
    -It was very common for the yard to incorporate “new features” into subsequent boats. For example, if a customer happened to order something specific, chances were high that all subsequent boats were built with it. -If the yard “improved” a feature, then again, typically subsequent boats were built with that feature.
    -I have documentation that says 115 gallons, others from the HC36 era said 90 gallons. For fact, I have loaded 85 gallons into a not empty tank.
    So, I think the summary here is that the later data sheets, which are still around (they say Union 36 on the front) are representative of the later boats, also known as Union 36’s, with some similarity to earlier boats, but without precision.
    Hope this helps.

    1. Emma

      Hi Emmanuel,
      I was just looking at the pictures again of the bilge after the tank was out & Saxony was in there cleaning it.. The interior bilge space in that area is much narrower than in the newer version of the boat. That’s likely where additional tank volume was picked up. If anyone is interested, I have hand drawn sketches of the later tank shape, not to scale but the dimensions are fairly close.

    2. Emmanuel

      Hi Emma! Thank you so much for your interest in the blog. Always love to hearing from fellow Union 36 owners. So to answer your questions in this post.
      1) The yard we worked at is Colony Landings in Bellingham. You would have to ask for Phil’s shop to get in touch with the welder who did our tank work.
      2) We only had to cut one floor support out to get the tank out and didn’t touch any of the cabinetry. I had checked with a previous owner who refitted a beautiful Union 36 and he had the same experience. We simply spliced the floor support back with epoxy when we re-installed the new tank.
      3) As for the vent, we are so proud of that design. We simply ran the vent up the stanchion post and drilled 2 @ 1/8″ holes in the side of the stanchion post at high level. So we get no water ingress in the stanchion post and even if we do we also drilled a small hole at low level of the post to drain. And now our vent is above the tank and above the side decks. So no more water in the tank from heeling over too much. I can send a sketch if you wish.
      4) Interesting information about all the hull numbers vs boat length. I had never heard of this before. Where did you find this info? Is your tank still the original? What year is your boat? What hull #?
      We have now both realized that buying an early hull number is not always the best move. So many things were improved over time so from now boat purchases will be later hull numbers for sure!
      We did not notice anything different in boat balance but we had not sailed Leela that much before the tank change. We do find Leela carries quite a bit of weather helm, not crazy amounts but enough that we always know when to trim our main sail down based on the weather helm. So we have not found a perfectly balanced boat like you mention and it seems from the forums and reviews that Union 36’s are not, by the very nature of their full keels, balanced boats. So, lucky you!!
      Emma, do you have a blog or pics of your boat? Would love to take this conversation offline. I’ll send you an email. Thanks again for all your info and I’d love to see your boat!

  2. Emma

    Most important thing, and I forgot to ask in earlier post.
    Sailing post the tank change, have you noticed anything different in the boat’s balance?
    I have most enjoyed how this boat sails, as she sails very well balanced. Meaning, the COE of the sails align beautifully with the hull CLR, and it’s possible to set the sails properly, and not need to be at the helm constantly adjusting the rudder position, and adding drag in so doing. This has been true full sail starting early in the day with just 5 knots of wind, to freshening across the day up to more than 30 knots when offshore from Monterey to Half Moon Bay. Can’t say enough about how well balanced she was. Didn’t have to have the hand on the wheel at all until suddenly amongst pods & pods of whales.
    Same balance as also been true in the slot in SF Bay.

    Are you able to trim the boat out & still find optimum balance?

  3. Emma

    So lovely to get your reply.
    Yes, offline email is fine. You can see my email, correct?
    No website, or blog, but pictures yes.
    The boat is in rebuild mode, more to do than original commissioning.
    Happy to share, have lots of info. Info is good, need as much as can find, also.
    Once back together, any and all are welcome, always enjoyed company undersail. Even the ultra-keen are welcome now, but will be a long time before back on the water. I very much look forward to that time. There is something magical about sailing, to be balanced and propelled by natural forces, while in nature. My family does not understand where this sailing thing came from. I think it is deep in my ancestry. I don’t try to understand it. I just know it has given me joy, strength, courage, conviction, empowerment, solace when needed, inspiration when otherwise there might have been none, and humor too, as my former colleagues and I once found on a sailboat rented in Goa!
    So thank you so much for your inspiration, and helping to get me back to my inspiration.

    In 1987 & 1988, I worked with Eric Ni (from Union Yacht Co./Ben’s son) at Ocean Yachts (Union Yacht’s west coast office for sales) on the commissioning of the boat, was actually living on the Oakland waterfront behind the business. There were about 5 or 6 other boats that had come off the cargo ship there at the same time, and most owners were not doing the commissioning, but Eric & his brother were. So, we saw, and learned much of these boats, the different “models” and met some other owners back then, even tho we did not stay in touch, do remember them.

    Also had a friend with a Hans Christian 36, Tikin, so knew all the prior history. And there is a database with the coast guard documentation/build paperwork info. Many of these boats in the US are/were coast guard documented, so if you know enough of the boat you can locate the document associated .

    Look forward to conversing more. Congratulations to you on your lovely vessel, and ongoing adventures! And thank you, so very, very much for sharing!

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