Your most frequently asked questions… answered.
Editor’s notes (2019)
The FAQ and discussion below has been mildly edited to eliminate typos, make it clearer who the authors are and which boats they themselves have (by hull number and boat name if known). Wherever possible alternative (i.e. current) references to products & suppliers are provided.
The bulk of this FAQ was originally generated as a Q&A in the period 2005 – 2015. In this period Lester Helmus acted as a clearing house for questions and responses, but some respondents would also write direct to each other, hence some of the overlapping answers you see in the FAQ. In places there are 2019 and subsequent comments, drawing either on my own experiences, or from other Corbin 39 owners and sources, including our Corbin 39 Group on Facebook. More comments are most welcome and this FAQ will inevitably grow.
We have attempted to contact all contributors to the 2015 version of the FAQ. All responses have been most supportive, thank you. If you are a contributor who has yet to respond please contact us.
As will be apparent there are multiple viewpoints on some topics. Sometimes, but not always, this can be traced to differences in arrangement between the boats of the various authors. Some of the topics raised are not so much a Q&A, as simply being a statement of why a particular owner thought something was a good idea, which of course it may not have been at all. Make your own mind up.
If you have further comments or suggestions on any of these questions, or wish to pose new questions, or describe various issues you have faced and/or overcome, then please contact us either via the Facebook Group or via the Website.
[Remark as of November 2019: Quite a lot of the links to drawings & photos are not yet reinstated due to workload. However I also know quite a few of the relevant images have gone astray. You may find the relevant photos in the individual boat’s entry. Please email us if you have any of the missing photos, drawings, etc.]
a. The view of the aft batteries shows our fuel plumbing. I have 5 fuel tanks as the area under the wheelhouse sole is divided up by “floors” (bulkheads to reinforce the area – which may be overkill). There is a fuel supply manifold with 5 shutoff valves and a fuel return manifold with 5 valves. All tubing is 3/8″ stainless with Swagelok connections. This is expensive and was time consuming but I didn’t want to have copper tubing (accelerates fuel gumming) or rubber tubing. Fuel was my specialty when I worked at Shell Oil. The other black tubular items are the heavy gauge wires to the inverter and breaker panel, also from the fwd batteries and the engine alternator batteriesunderpilothouse.jpg . David Salter (s/v #050, Opportunity)
Here’s a question I’d like to pose to the group. My plan to launch early this season were dashed when I opened the boat up for the first time in about a month to a reeking odor of diesel fuel. Turns out my 125 gal fuel tank has finally given up the ghost after 29 years and has been leaking into the bilge all winter. All I could find to identify the leak was an area of the tank along the rear bottom seam that seemed to be weeping fuel. My tank sits directly under the cockpit behind the companionway bulkhead. There’s no way short of tearing the entire aft section of the interior apart and cutting the tank up into smaller pieces that I’m going to get this tank out. Even if I can accomplish the removal, what kind of tank am I going to be able to replace it with? Any hard tank of any suitable size will not be able to be installed without majorsurgery both to the interior and the exterior. After a lot of thought, I’ve come upon a much more radical but probably easier solution. What I’m proposing is to open the hull underneath the tank and drop the tank out in one piece. I could then either repair the tank (not likely) or use it as the female “mold” for an all fiberglass tank; i.e. encase the tank in fiberglass, then remove it, leaving the FRP shell as the new tank – lighter, stronger and corrosion proof. The hull cut-out would be re-used to fill the hole in the hull and the new glassed area should be as strong or stronger than the original. After all, if I were to hole the hull on a reef, I’d do much the same as a repair. I’d like to know the following:
1) Please verify that the hull below the waterline is solid fiberglass
2) I’ve heard of ethanol damaging FRP tanks. Does marine diesel contain ethanol?
3) Has anyone built an FRP tank? Do I need to use anything special to create the new tank; ie is West System Epoxy sufficient or is there something else?
4) Does anyone see any problems with this plan that I’ve probably overlooked?
All comments will be very much appreciated. Best Regards, Vince Salese #005, Witch of the Wave, Hull #5
a. Your solution seems radical, indeed! Won’t you have to tear out the interior in order to fiberglass the hull section back in? Sounds to me like you want to put a removable floor into the cockpit and go in that way. Maybe, you should contact Collin Harty http://buildinggalene.com/, still lists an 80 gal aluminum tank for ‘Tag Sale’. I have a similar tank, I think. It fits in neatly through my companionway and down below the removeable pilothouse floor boards (soles), just aft of the galley bulkhead.. My floor timbers were spaced for it. Mine is v-shaped, sloping down foreward and up sideways to fit the centerline of the hull bottom. But, I don’t have any propellor shaft; I have a saildrive with the engine under the aft cockpit. Lots of luck with your problem. Lester Helmus (#010, Insouciance)
b. Tell you what I did when our steel tank gave up the ghost a year ago (luckily I was on board on the hard and could organize a drum). Same problem as you: tank too large for the opening. Took an angle grinder to the thing and got it out in 3 pieces. Designed and ordered two new polyethelene (??, black, weldable plastic in any case) tanks from a Turkish supplier, dropped number one, and shoved it to the stern, dropped number two and hooked it up to number one. Case closed. Only problem: the design was not executed faithfully and we now have tanks with about 2/3 the previous capacity. Hope this helps. Gerry and Brigitte Stuurop (#087, Octopus I).
c. If your tank is structurally sound, and it sounds as if it is with only weeping or a pin hole, and if you can access it by installing a new access through the cockpit sole and a port(s) into the tank top; I would check out a product called “RED -KOTE”. It was developed in Australia to repair tanks in place. Go to Damon Industries, Alliance, OH, www.DamonQ.com regards, Ray Sullivan (#068, not yet identified)
d. Thanks for the comments and believe me I will take every suggestion, criticism, encouragement etc before I take a saws-all to my hull. Coincidently, after posting my question last night, I found this website that explains exactly what I was intending to do http://marlowmarine.com/fuel_tankreplacement.htm First a couple of things. #005, Witch of the Wave is a rear cockpit not a center cockpit – just a clarification. Luckily I don’t have a finished interior in the aft section behind the companion way bulkhead. It’s nothing but painted plywood used for storage. We call it the garage. Yes I could cut and remove all that to access the tank, but I still couldn’t get the tank out in one piece unless I also remove the cockpit floor. Reglassing and refinishing the cockpit sole and reinstalling the interior is as daunting a prospect as cutting the hull so long as, and here’s the key, the section I cut is solid fiberglass – I just don’t want to deal with the Airex core for some reason. Cutting the tank certainly is easier but, as Gerry implies, I’d have to compromise on the replacement tanks. Removing the tank intact means I have a plug mold for a new fiberglass tank. Is it your opinion(s) that I’d be compromising the hull’s strength? I’d grind down the seam/cut area before cutting so as to leave room to lay-up as much as 3/8″ of new matting before fairing the whole area. When I reinstall the cut-out section I’d epoxy “glue” the seam and lay-up matting both inside and out side. I would think that this section would actually now be stronger than the surrounding area. My biggest challenge is to reinstall the cut-out in exactly the same position to maintain my shaft alignment because, of course, the shaft strut sits smack dab under the tank. Keep the comments coming. I’m not going to cut anything inside or out until this is well thought out and planned and any and all alternatives are exhausted. Whatever I do, I am going to document it fully so others can learn from my experience good or bad. Best Regards, Vince Salese.
e. Hello Mr Vince Salese, I think the solution of cutting the hull would be the right thing to do. I suggest you:
1st Check to see if you have two tanks or only one big tank,
2nd Cut a hole in your floor to get access to your tank,
3rd Take your tank out through the hole and cut it up so that you can get rid of it by way of your companionway,
4th Install a new tank in place with “Vinylester Resin”. If you need, I could send you the number etc.
This method is the only way that you will avoid having a bigger problem then what you have now. Best, Gaëtan Duchesne.
f. My previous boat, a Fisher 37, had a similar problem. The fix was to have a custom fuel bladder made that was installed through a hole cut in the top of the old tank. The repair was done by a company in Seattle WA but I do not have any contact information. I would hesitate to cut a hole through the hull unless it was a last resort. David Williams (#154, Sunshine).
g. I’m in the process of replacing my fuel tanks. The tanks are located under the pilot house deck, aft of the navigator’s seat and just forward of the aft bulkhead. The pilot house deck is divided in half for excess to the transmission/ prop shaft thru a hinged lid and aft of that is the deck over the 2 fuel tanks. I’ve got the deck above the tanks removed and just today removed the tanks themselves, what a job. I’m looking for someone to build the tanks locally. If anyone is interested I’ll take pictures and send them to you. John and Anita Baumgartner (#116, Bright Eyes).
(#131, Two Crows) is a 1982 Mk. II. Her aluminum fuel tank began weeping fuel a few months ago and I have now emptied the tank and removed it. The source is a spot of corrosion in the sump: gentle scratching with my screwdriver caused the disintegrating spot to open up to a 5 x 3 mm hole. I’m probably very lucky not to have the whole contents of the tank in my bilge. Don’t ever ignore fuel leaks. Now the tank is out and needs to be welded. The welder won’t touch it before I have it steam cleaned.
(A) Does anyone know of tank steam cleaning services in or near Toronto?
(B) I have been quoted $500 from one company. Does this sound reasonable?
(C) I want to install a visual inspection port. I am thinking of a 6″ circular opening with two aluminum backing rings holding a 0.5# plexiglass disk via 8 bolts and a rubber gasket. Does anyone have experience with or comments on that?
(D) Also, I was thinking of running a tube to the bottom of the sump to be able to manually pump out sludge/debris from time to time. Good idea?
(E) The tank was made by Unitech Manufacturing, Woodstock, ON – does anyone know how the baffles in the tank are arranged?
Thanks all, Boris Steipe, (#131, Two Crows).
a. I just added an inspection port in my SS tank and found baffles kept me from seeing and cleaning everywhere. Then I cut another one on the other side of the baffle only to find yet more baffles. It would take at least 4 ports to see everything so plan well before cutting. Also, I would worry about plexi plates because the plastic expands differently from the aluminum and it will leak eventually even if diesel doesn’t attack it. Sump drains leak, as well; better to suck up debris through a top-hung fuel pickup. Make sure your tank isn’t sitting in bilge water or on a soaked piece of wood; aluminum oxidizes to protect the surface but if it rubs on something it will keep deoxidizing and wear thru. Also, salt water in contact will wear a hole. These tanks often leak at about 20 years so anything we can do to prevent that is important. When you cut a port use aluminum plate, a nitrile gasket, and aluminum bolts (aircraft hardware) to prevent dissimilar metal corrosion. Make the tank thicker and it will last longer. By the way SS isn’t any better as I have learned with my water tank. John Gleadle (#181, Spinnaker).
b. When I installed an electric fuel gauge on my aluminum fuel tank I found:
1) Bottom of fuel tank has a slight v shape and slants down towards a 6” x 6” x 4” deep sump at one end,
2) One baffle in the middle of tank, and
3) Pick Up line was just above the sump bottom.
Respectfully, I am not sure if fiberglass panel would be kept clean enough to see anything. I would just cut a 4″ sq. inspection hole in the top above the sump and make a good gasketed cover for it. You could make a ” squeeze bulb ” thing long enough to reach the bottom of the sump (like a battery tester thing) to clean out the bottom of sump now and then. Anything that has vacuum would do as well.
Note: Measure fuel when filling up and note quantity @ 1/4 , 1/2, 3/4 and full as it’s not quite linear. That is very useful with electric gage. [Ed. Note: I use a wooden dowell to measure; I’ve had no luck with electric gages.] Good luck with this ……………. Frank Bryant (#186, Visitant).
c. Thanks Frank and John, useful advice. Yes, I would expect the plexiglass to age over time. I think I’ll just give it a try – if it holds up for less than say five years, I’ll replace with glass. Great idea about the squeeze bulb. Boris Steipe
d. The design of the fuel tanks called for a sump lower than the bottom of the tank and a pickup that went to the bottom of that sump so that you could suck any water or solid trapped in it. It had its own pickup on top of the tank. If this sump pickup is not there, it`s possible that the tank does not have a separate sump. Then, it is better to have the fuel pickup at the very bottom of the tank so that it picks up anything that could lie there including water and any solid. If the pickup is higher, like it is often the case, then solids and water will accumulate at the bottom and when the weather is bad, from the movement of the boat, will mix with the fuel and clog the filter at the worst time. As far as the inspection hole, I would not do it on my boat, because any opening below the top will eventually leak and you will have fuel in the bilge. Rubber gaskets are known to be eventually eaten up by fuel and leak. If the tank is full when it happens you will have to empty the tank to fix the problem. If you want a manual fuel level check, do the hole at the top, small, and use a dowel rod to check the fuel. The gasket should be of a material that is resistant to fuel (not rubber). Hope the above will help and have a great day, Marius Corbin
e. I don’t recommend an inspection port in the side of the tank or any opening except at the top. You would be initiating a chance of a leak. Your proposed method could result in attack of the gasket/caulking by the fuel over time as well as differential expansion between the Plexiglas and the aluminum. I have used a dipstick successfully, a piece of wood dowel marked in inches, litres or gallons, and inserted by a removable plug on the tank top [Ed. Note: Over the deepest part of the tank]. It is crude but trouble free. You probably know that there are commercial level gauges that use hydrostatic pressure with a small nylon tube inserted from tank top to the bottom. See http://thetanktender.com/ An ability to pump out the sump is also a good idea, again using a tube from the top of the tank. For example, use a suction pump with a piece of copper tubing extending to the tank bottom. I insert mine through the dipstick port! An engine oil vacuum suction kit could also be used for this job. See Bigboy Topsider. I have one of these but have not used it for fuel. It should be OK for diesel (not for gasoline) but you should check compatibility of the gaskets.
Regards, David Salter (#050, Opportunity)
f. My aluminum fuel tank is underneath the pilothouse sole. I was going to add a similar port so I found some cleanouts at Fisheries Supply in Seattle. They’re called Seabuilt tank access plate system. I was able to pull out the tank sender and see the baffles. My tank has six compartments. That’s when I gave up. I didn’t want to put six access hatches in. I bought a paste you can get from the home heating industry that detects water in diesel fuel. You rub it on a stick and dip it into the diesel fuel to detect water. I was able to access my fuel through the sender hole. I had no water in my tank probably because the fill is underneath the cockpit seat. [Ed Note: You might also want to buy a filter that removes water [Funnel Fuel Filter.] Regards, William Schmid (#174; “Anakena”).
a. I have just siphoned the fuel out of my outboard motor tank as part of winterizing. I used a small hand pump that I had used in industry and I have found many uses for it. For example, it could be used to suck from the bottom of a fuel tank to check for (or remove) water. It can also be used for water siphoning. See details at GOLDEN THIEF, sampling pump, 4520 Cleveland St. Gary, IN , 46408-3715, Phone: 219-980-3848, FAX: 219-980-2937 PumpPrice.htm Also see “Home”. Recommend Aluminum Model U, $55.81, that seals to a rigid bottle, e.g. glass, so that a vacuum can be pulled. A plastic bottle can be used if only a light vacuum is used. Regards, David Salter (s/v #050, Opportunity).