Osmosis Explained - Sailing Mahalo Episode 6
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- เผยแพร่เมื่อ 28 ก.ค. 2024
- What is osmosis in fiberglass boats? Why does it happen? We're in the middle of an osmosis treatment on Mahalo, and it's a tough job!
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#sailing #blisters #diy #osmosis #refit
Thanks team of Maholo, as your video and commentary are great tool for this armchair sailor....cheers
Osmotic blisters are caused by incompletely catalyzed pockets of resin. This happens because once the catalyst is added there is only 15 minutes of working time so the tendency is not to spend enough time mixing the resin and catalyst. When the components are fully mixed you will not get blistering. I worked at a major sailboat maker for 16 years, the last 5 years I was the customer service manager and dealt with the blistering problem extensively. We had
many production boats that never blistered so it is not inevitable that blistering will occur due to the use of polyester
resin. If it does occur, then a coating of epoxy is a good solution.
Would this apply to fibreglass corvettes, mine has some blisters on one side of the hood . It was repainted with PPR polyester paint and a year later the first bluster appeared, now it has a few more.
not the same. Your Corvette is not subject to hydrostatic pressure like the portion of hull that is below the waterline
Last episode of A Boat Called Wanda also had some serious structural fluid accumulation.
Must be frustrating as 🔥 to wait for “dehydration” over time…
Was the boat surveyed before purchase ? Did the surveyor note the osmosis problem ? Also please do something with the microphone the audio is terrible could hardly understand what was being said .
What about the above the waterline? Surely the same method of construction with polyester resin continues above the waterline. Although blisters may not be as extensive, it might be worthwhile removing the gelcoat above the waterline and adding a good foundation of fiberglass with epoxy resin. Just a thought....
Great point! We've thought about doing a complete job, but osmosis really only has a chance to occur from the water line down. Everything above is not exposed to water for long enough to become delaminated. Considering the cost, we will stick to a bottom job only for now.
This is exciting, more so for you I know but exciting to watch. Hey, for when you start interior work, check out OnBoard Lifestyle on TH-cam. Teal is an amazing craftsman and has lots of tips and techniques that may come in handy. Also, check out Patrick Childress, he is also a craftsman with years of knowledge. Looking forward to the next video. Cheers to you all.
Thanks for the tips Patrick! We will check them out.
Let me ad the following to his explanation. The blister does not just form in random locations, and for no good reason. The blister forms initially because there was a void in the gelcoat and/or fiberglass resin/glass. That void, even a microscopic void, fills with salt water through osmotic pressure. Which inturn starts a chemical reaction within the fiberglass resin. The reason that the entire hull below the waterline does not form one giant blister is because the entire hull is not totally filled with voids. The blister will only form where a void once existed. My point is this. If the manufacturer of the hull would have invested in better equipment, and they would have properly trained their layup crew, and they would have used vinyl ester resin instead of polyester resin, there would be far fewer blisters in hulls. But profit comes before anything else. So you end up with a bunch of blisters as a result.
Thanks for the additional information, David!
Wow, I could write a chapter of a book on what I have seen here and in the other videos. I’m Not sure where to start
You video work is good but you are a pro and it shows! It’s wasted in this project.
I think Chris made a big mistake buying this boat ,sorry you probably all know that too. It happens. You also did not appear to pull the boat out of the water for the surveyor which would have found the osmosis problem & bad laminating problem. This boat was amateur built unfortunately ,and not by a fiberglass expert. Then it was done with an unproven method that was hugely questionable. I also think the choice of the actual polyester resin type may have been wrong. There are various type that are better or worse for water immersion. Some type have better chemical ( water) resistance than epoxy , that also comes in various types.. This was one mans life work and it is sad that an unsuitable method was used to build this hull from, The interior means nothing if the hull/foundation is bad . Since the hull is an integral part of the interior it must be right to be worth pursuing .
From the few photos it looks like the plywood for the bulkheads and other wood structure are not marine grade , BS1088 Brunyzel. Plywood is the only wood that lasts in the marine environment , all else rots sooner or later. Frequently Encapsulating in resin epoxy or polyester will cause rot faster in wood it just takes longer to see The rot.
The rotten keel is a huge problem , boats do not get built properly where a little caulking applied externally is supposed to seal leaks . The hull should be designed completely differently. . It’s not your fault you are not boat builders or apparently previous body owners.
Back to the fiberglass , you have found huge blisters deep in the laminate . This boat was not built in a mold but as a one off with the layers built up from the inside out . Done right this can produce a good laminate but it appears this fiberglass had a lot of voids left in it which only accelerated the osmotic issues. I can see how this would happen . Incorrect preparation of the cured layer before applying the next, working upside down, working alone probably in poor lighting many possibilities. The gelcoat applied externally is a sketchy process at best , and under water take carful application over the right kind of fairing compounds , was it polyester or epoxy fillets used , I bet polyester type and what grade???
These are only the things you can see , what about all the things you can’t see , what are the engine bed like ? Are they wood , what wood? Are they rotted? , what about the mast supports are that done right ? With good materials? An amateur built boat has to be reviewed very carefully . A professionally built boat built with good processes you have a chance to fix and get something worth having .
The crazy pipe or tubes or whatever????
You will need to blow air or vacuum the water out! Crazy . If you thought everything else on this boat was perfect above and below the waterline you could remove all the outer fiberglass and all the pipes ( a section at a time ) and replace it entirely with something else , many choices.and then re laminate the hull again. But the rest of the boat is not right! Clearly ,
The designer , who was this ? it’s a weird looking hull , very heavy and possibly too small sails. Very odd looking , strange stern cabin maybe a modification by builder?
I would get another or the same surveyor in to look at the boat now with it opened up and see what they say , preferably somebody who has worked in s boatyard too . I think you will be surprised what they might say now .
Sorry this is really long comment and you probably won’t read it but the bottom line is ..... take the loss , sell the good bits of the boat , engine , sails etc and go buy a smaller boat which you can go sailing now . Have fun live your lives doing the fun stuff , there are many good boat out there . that were properly made get one of them
You can never make this boat right again the time has come .
All the best Warren
40 years on designing and building , ex boatbuilder and still in fiberglass business