The OP gave it roughly two layers of FG so I think you'd be looking at something which behaved like a "fiberglass bladder tank" if the internal SS were to be lost
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Wrapping a stainless tank in fiberglass
- Thread starter baycloud
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I still have to ask the question which I imagine is lying in wait on the tip of many people's tongues, WHY did you embarked on this particular fool's errand in the first place.
A miserly approach ? too much spare time ? the challenge ? What was it ?
A miserly approach ? too much spare time ? the challenge ? What was it ?
You should have filled it from gallon jugs to determine the capacity…
I have followed your channel for a while. Nice boat.
Greg
If the fiberglass makes a complete seal - not likely. It's hard to know from watching the video.The OP gave it roughly two layers of FG so I think you'd be looking at something which behaved like a "fiberglass bladder tank" if the internal SS were to be lost
dj
It's irrelevant if pinhole corrosion starts on the inside or outside. Covering the inside or outside does several things: creates a new environment under that coating that may or may not be more prone to corrosion cells. It creates a barrier that can inhibit passive oxide reformation if a corrosion cell starts. It is not unlikely that you have some trapped contaminant that could act badly. You may have holidays in the coating that can create corrosion cells. You have created an interface at the edge of the fiberglass where it stops - this is actually the most susceptible area - especially in the inside - for future corrosion concerns.I saw that the pickup tube was starting to have pin hole corrosion, but as per my diesel and this tank - I notice generally corrosion happens at the waterline. I don't believe at all that the uncovered top of the black water tank will corrode first. It will be the bottom or the sides, thus my lack of 100% encapsulation. So my prediction for the failure mode will be pinhole corrosion on the pickup tube (epoxy glass wrapped up almost to the top of the tank on the inside) and then at the 'water line' on the sides of the tank. Then further pinholes etc. With 2+ layers of fiberglass, I think there would need to be a loss of >20% of stainless before structural issues occur; and predict that the pickup tube vacuum/structural integrity will fail first.
I have read that stainless doesn't like being submerged, however I am less familiar on how a covered 'outside' of a tank would affect an unchanged and uncovered 'inside' of a stainless tank. It doesn't intuitively make sense to me that a covered/uncovered outside portion of a tank would affect pinhole corrosion on the inside. I don't claim to know either. I'm sure however that...we'll find out! But we will have to wait. As dlj said, probably until I cross the pacific
It's not possible to predict if any or all of the above will create an accelerated corrosion condition in your tank. In the best case, you did a whole lot of work for no gain, in the worst case you have shortened the life of your tank by some undefined amount.
It's not catastrophic - it's just bad engineering. It's a whole lot of work for either nothing, or making your tank more prone to future corrosion concerns.
But if it makes you feel better - then for you it's a success....
dj
FWIW, YachtWorld has several early 90’s Hunter 40.5’s listed. Holding tank specs range from 30-35 gallons. One lists 30x 2….i assume a 2-head model.
I would guess your tanks is 30-35 gallons.
Greg
I saved about $2k, which is something, plus the delay wasn't workable, but ultimately I'm hoping for results. If it fails soon, then it will be the proof that I haven't seen that this is not an advisable method.
I understand the comments, but they're all predicated on an assumption of a failed bond. I disagree that that's a guarantee. If I thought a pinhole would cause mass delamination then I wouldn't have done this. I will make an update, but I have no desire to regularly pull the floor to check. maybe every 5 years or if something happens
$2K to replace a holding tank??? A new top quality plastic tank up to 25 gallons shouldn't cost you more than about $300, if that much and a lot easier to replace yourself than all that fiberglassing.
--Peggie
I read the OP's last post and was thinking, I never even mentioned delamination, nor would it be a failure mode I'd expect. The phrase "you can lead a horse to water, but you can't make them drink" comes to mind.
dj
It wasn't a $300 decision.
The Hunter forum all recommended this manufacturer, MMM:
Plus CA sales tax plus $500 shipping > $2k.
This tank is already quite small so smaller and a less optimal shape was not worth any effort from my point of view. I looked through maybe a hundred or so designs and nothing looked remotely workable. No Legend 40.5 owners use stock tanks.
As for the other guys, it's bit weird - people think I just make shit up and then they respond with personal insults? Must be the election season...
I guess for some people, group think and ego (let alone incomplete analysis) is more important than success. My counterpoints weren't answered other than by insult. Ok.If it's a failure, then their criticism will be correct. However, so far, so good.
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From a related thread by a different 40.5 owner:
SBO latest holding tank replacement thread
If ya'll can find a $300 tank for us then hundreds of people would have been in the past and would be in the future very grateful - so please let the forum know! I can tell you the reason no one has gone with a stock tank is for the same reason as myself. They are pumping out constantly and intuitively or explicitly know that a smaller tank is not viable. It's not a question of if something could 'fit' - it's a question of how much reduction of functionality (holding capacity) would be acceptable.
SBO latest holding tank replacement thread
While I have great respect for Mr Calder, I humbly disagree - my preferred option is polyethylene. Less permeable than fiberglass and not as prone to leach chemicals into fresh water. Also, fiberglass holding tanks made from polyester resin are permeable to stink. Unfortunately I found that out by experience in one of my past boats.
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I would suggest that poly holding tanks for boats had not been out long when Nigel Calder published his second edition of "Boatowner's Mechanical and Electrical Manual" back in 1996. I would suspect that Mr. Calder would now consider poly tanks far superior to FG tanks for all applications of tankage on a sailboat.
I was citing the 4th edition, published in 2016.
He doesn’t clarify whether polyester or epoxy resin would be best, though I expect epoxy could be used and be water safe. He also doesn’t really give any significant downside to polyethylene, especially if you can get a size and shape that’s a perfect fit.