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osmosis repairs with duratec vinyl esters?

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looks like i have an osmosis job to do


Mike Menzies has 1 of the better osmosis repair write-ups on the web and recommends vinyl esters over epoxies due to their absorbing less water




Duratec in henderson seem to sell vinyl ester products specifically developed for osmosis repairs



A high quality "sprayable putty" for fairing and priming composite marine surfaces. An integral part of the Duratec Marine System. For one-off and production composite yacht priming and osmosis and blister repairs. Formulated for below-waterline, topside and deck surfaces



For one-off and production composite yacht priming and osmosis and blister repairs. Formulated for below-waterline, topside and deck applications.


http://www.adhesivetechnologies.co.nz/d ... ml#sanding


so am thinking of grinding out the blisters, feathering down the edges, washing, drying, filling with the fairing primer, fairing, then a few? coats of the primer, antifouling


anyone any vinyl ester experiences to share or general osmosis comments?

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Following with interest... Just trying to buy my first glass boat (previous was wood) and the whole subject of osmosis seems like a veritable minefield with more than its fair share of 'experts'. Mike Menzies seems to me to know more about it than anyone else in NZ, but of course his time isn't free, and rightly so if he's the expert he appears to be. Not sure how much stock I'd put in anyone else's opinion at present - not unless they prove their credentials on the subject. Sorry crew.oracle! :wink:

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The old osmosis chestnut. Many people have lots of different ideas etc so take mine as you will.


Once you have one two or ten blisters it means the whole boat has it. .. The other blisters just aren't showing yet. If you took a moisture meter (another hotly contested topic) it would indicate that the whole hull is high in moisture and there for the osmotic reaction is happening.


Vinylester & expoxies whilst they are good at creating a barrier to prevent moisture from being drawn in they can't stop the osmotic action that is already happening.


In other words if you ground out the blisters you can see then applied a vinyl epoxy barrier the next time you antifoul you will still have a whole bunch ofv new blisters.


The trick is to remove the moisture in you hull to stop the osmotic action. Either a peel re glass fair etc ( I still personally believe that even once you have done a peel the exposed polyester should be cured by heat) or the hot vac system.


Once you have removed the moisture then the barrier vinly epoxy coats can be applied to prevent new moisture from getting into your nice new handy work:)

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stripping the hull, pulling the mast


putting the bare hull in a pressure and temp controlled oven for x? hours would be the best way to dry it out


then flipping, skimming and recoating with the best, hardest moisture barrier possible


must be better than a 'cheap bodge'




but it ain't gonna happen...




so what is the best 'cheap bodge'?


or is even a bodge necessary?


when was the last boat sunk


due to excessive 'blistering"?

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Nope, all that old laminate peel and dry for weeks and months and so on is all a complete waste of money and time and energy. Firstly, Blistering due to Osmosis is an issue for a particular type of Polyester used back in the very early 70's. Vinyl Ester was introduced and that was out a stop to Osmosis.

AkzoNobel/International Paints did a lot of research re the Osmosis issue and came to the final conclusion that it is not as bad as the scare mongering made ones think. The Hull is not delaminating etc etc. They came to the conclusion that Peels were not required. You did not need to spend huge amounts of money having the Hull dried in a Humidity controlled tent and all the rest of the carry on. They found that all that is needed is for the Blisters to be broken, allowed to dry for a day or so and then filled with epoxy filler, then a Barrier coat applied. Whether you want to go Epoxy or Vinyl is up to you.

For a really bad blister issue, a method of using Dry Ice blasting worked well at breaking open the blisters without harming the rest of the laminate. But I don't know if that kind of thing is done in NZ. Simply abbrasive grinding them open will work fine. Allow the hole to dry and then fill with Epoxy filler. Then apply your Barrier coat.

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Having had Mike Menzies inspect and then advise on the best treatment for what was quite minor osmosis on our yacht, the simple yet most strongly advised upon repair was simply to grind out, repair using the vinyl ester system.


It is now 5 years and no signs of any form of blistering to date.


It was fairly lost cost to do this repair, and it appears to have worked well.


I can honestly say that Mike is very good at what he does, and if your going to be investing significant funds into repairing your yacht, or into purchasing a second hand GRP yacht, I would strongly recommend involving him. He is also a nice guy but someone who says it exactly how he see's it. Investing without professional guidance is only for those who have too much money, or are willing to part with more than they should.

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Wheels, do you have a link or citation for the AzkoNobel/Intl research on that? Would be interesting to read, though I guess any commercially funded research needs to be taken with a pinch of salt.


Thanks for the PM Battgirl - always good to get a different point of view.

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Mike Menzies is a widely respected GRP guy and if memory serves me correct he pioneered the peel and suck treatment in NZ. I think the main danger with osmosis nowadays is it allowing moisture into the foam core. We had an issue with one of the Pride of Auckland boats when I was looking after them and we had to replace the entire foam core on one side. It seems that improper bedding of the beltings allowed water into the core and it started the osmosis process from inside.

Anyway. I would trust Mike's advice as he was at the forefront of solving the problem in NZ.

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Wheels, do you have a link or citation for the AzkoNobel/Intl research on that? Would be interesting to read, though I guess any commercially funded research needs to be taken with a pinch of salt.

Sadly no. I saved the info on a hard drive from about three computers ago. The company that included International Paints has changed dramatically since then and I have never found the "white papers" again. Maybe of someone emailed and asked them, they might be able to help. However, if the info was in the days of me being apart of Cruisers Forum, it is possible I posted it their in the technical info ad it could be worth a search.

The article was from one of the companies head research guys, with a well known name in the Industry, whom as soon as you heard it you would most likely recognise it. But seeing as I have the memory of a Goldfish with a Bad memory, I can't remember. The info was from the experience/research perspective and not from one of a commercial benefit. In fact, it would have been of greater benefit to them to have told the opposite story. The info was of the same time that the guy wrote another article on research were they found Evadure did not work and fully sealing timber from water, due to the solvent evaporation leaving microscopic pores that water then entered via.

Wheels, do you have a link or citation for the AzkoNobel/Intl research on that? Would be interesting to read, though I guess any commercially funded research needs to be taken with a pinch of salt.
That is not an Osmosis issue, it is a leak. Osmosis is a very different kettle of fish, of which I know you understand PW, sp I will not go into Osmosis and tell you how to suck an egg.
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These are the sorts of thread replies that make me give up on this site and it's forums. To many experts or chiefs that can wave magic wands and view some ones boat through there computer screen and diagnoses it and fix it.


Osmosis is a word, not unlike Rot. it's a term use to describe water ingress into a hulls laminate or air void/bubble typically via a strand of fibreglass, or laminate void.


This like Rot can have many varying degrees of state, from the soggy sponge like laminates of say a very early Raven, to a fingernail sized blister.


Points to remember, until infusion was fully developed most boats have been hand rolled (or the laminate hand consolidated) so every boat will have "that" human factor to it.

This means every boat will be different to some degree


So have an expert look at it if you can, listen to them first of all, if your not happy get another expert to give a second opinion.


Osmosis, like Rot should not be generalized, it should be looked at case by case.

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fng it is unrealistic to expect most members here to have an equivalent knowledge of a professional boat builder.


Many don't have the financial resources to hire a professional every time something goes wrong. Many are just boating enthusiasts trying to do their best and help others where they can.


Nothing wrong with that, but, as you say, sometimes the advice given is not entirely accurate. Where that is the case, corrections are often provided, regularly by some of the professionals on here, like yourself. This is greatly appreciated, and it is often the information available on this site that attracts, and keeps members.

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Nope, all that old laminate peel and dry for weeks and months and so on is all a complete waste of money and time and energy. Firstly, Blistering due to Osmosis is an issue for a particular type of Polyester used back in the very early 70's. Vinyl Ester was introduced and that was out a stop to Osmosis


Wheels, i have seen 3 year old euro boats needing total hull jobs. It's not restricted to only old grp boats.


What i believe is best advice for anyone who is pondering what to do is to seek professional guidance as that will most likely cost less in the long run. Mike menzies is the best i know of.

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And back to the original poster - while Wheelie and FNG are seeing who's yellow stream will travel further ( hopefully into the wind ) Lets take a big giant step back to the issue you have at hand.


Are you in a position to get professional assistance in to determine the best way forward for the vessel in question?

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went out to 17 corbans rd henderson


and spoke the very knowledgeable guys at adhesive technologies who seem to be suppliers to the frp industry with a huge range of bulk; resins, cloths and fillers


they advised a 'permanent cure' would be to 'peel' the compromised gelcoat off the hull, and resheath with a layer of chopped strand and vinyl ester


costing thousands and taking weeks


however if i just wanted to do the best repair i could on a limited cash + time basis, grinding and filling with either epoxy or VE was better than doing nothing


first up they thought using the expensive duratec vinyl ester system was probably an overkill for this kind of repair and so they sent me off with


- 3.8ltr of a cheaper vinyl ester resin ($60-gallon)

- the specific (1.5 - 2%) catalyst for it, (very similar too but not the same as polyester cat)

- 8kg of 202 filler (very similar to the 400 series west fillers they also stocked, but 202 seems to mix better with VE without any 'foaming issues'


total cost $120


they also advised the local abrasives warehouse sold #80 flapper disks so picked up a bundle for $3 each


back at the boat late afternoon mixed up 50ml of resin with 1ml of cat and working quickly brushed it into as many 'divots' as possible before it started to gel.

this helps to re-resin the glass fibres that have been leeched white due to the breakdown of the resin by the chemical reactions within the bubble, better fills any tiny gaps + provides a better bond for the following mix)


then mixed another 50mil resin batch but with an equal volume of filler on top, and used a range of scrapers to smear the thickened mix flat over the divots


that first 'test' batch should have fully hardened overnight so will go down soon and see how it cleans up with sanding


then the rest of the day will be repeating, again and again


will try and get some pics up later

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After your grinding and filling are you going to interprotect the hull and tackle blisters as they appear later on or leave it and eventually deal to the entire surface? As mentioned osmosis varies greatly and you are the only one that knows how bad it is. But it certainly doesn't have the stigma it originally did, it used to be like having the clap, not that I've had either.


I know what osmosis is but I'm not sure about the clap, where's Bushman he'd know?

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Right, I've been out most of the day. Just caught up with this thread, and I've deleted a few posts.

It beats me why people cannot discuss differences of opinion in a polite, adult manner. :roll:


Really, IMO both parties were right, just coming at this from different angles - Osmosis is by its dictionary description;

Osmosis is the spontaneous net movement of solvent molecules through a partially permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides.


That does not matter if it is GRP or a plant leaf. That is osmosis.


Now re boats;

Water in the laminate, due to a crack, damage, or poor quality is NOT, technically speaking, osmosis. This is Wheel's angle.

However, it IS treated the same way as osmosis from a repair point of view, which I think is what FNG was trying to say. It doesn't matter how it got there, just fix it and move on.


The result of this "discussion" is that two valuable members have thrown their toys out of the pram, rather than discuss this like adults! :(

There is not much I can do about that but remind people to be polite and diplomatic with their posts, so no-one gets upset, and we might ALL learn something!


Back to the topic - there is a good article here http://www.smithandcompany.org/GRP/GRP.html for anyone who would like a more in depth understanding of Osmosis.

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I have been sent this to post, it has some good points, so;


To answer the original question regarding osmosis repair here are some facts.


After 20 plus years in the marine coatings business including 9 years with International Marine paints developing and testing systems (GEL Shield™) to protect boats from Osmosis I can report the following.


In plain English...


There are two scenario to the solution...


1. Correct system and product.


2. Correct remedy and application.


These two apply to both professional and amateur. But remember the professional will have the better setup and equipment to fix the problem to a better and more consistant level. But excellent results can be achieved by amateurs using the correct system / spec.


I will not get into all then detail regarding identification and types of osmosis. I want to just explain the system/product selection.


international Yacht Paints spent millions testing hundred of resins on many differing substrates over many years. This culminated in the best products available to the industry and ultimately resulted in Gel Shield systems and products like nterprotect etc... And The results were without debate.


US Paints, Boero (Italy)! Petit, Sigma, and many other companies did the dame thing and ended up with the same results.


300microns (dry film thickness) of a high quality epoxy "barrier coat" applied over correctly prepared surface is the best solution.


The Epoxy has to be high quality. The supplier will know if it is fit for purpose so ask them for a supplier statement and spec.


Vinyl ester is the next best. Again ask for a Supplier statement of suitability. Why you ask?....


Many early osmosis repairs done in NZ HAVE HAD REOCCURENCE of osmosis due to poor workmanship and / or poor quality product ( epoxies and Vinyl esters)


Some applicators have used "any type of epoxy" and thought this to be OK. Not all epoxies are the same. Some are good for certain jobs but only a few are good for osmosis repair.


Personally, I would be tread carefully with hybrids like vinyl ester.


Please!.. get a spec and get an assurance the product is fit for purpose. This applies to both the home handy man and to the professional.


Ask the pro for the paperwork along with the quote. No paper work no go!


As for repairing osmosis. There are Giga bytes of info out there. Trust the big companies and follow the process to the letter.


Remember, every hull will be different and seek 2 opinions. Some people will offer a peel when there is only a isolated issue and vice versa.


For the best job, in AUCKLANDS HIGH HUMIDITY, the real pros will have a shed with dehumidifiers and will have testing equipment to ensure the substrate "ready ( moisture/alkalinity/acids etc), for recoat/glass etc.


Remember entrapment of air, water, solvents, uncatalized driers/catalysts etc... caused the problem in the first place and can also be an issue during repair. Also vinyl esters, and their curing mechanism, can have issues similar to Polyesters. Solvent free hi quality epoxies do not!


Having said all this osmosis repair can be done by the average person with a bit of good prep. But the " good pro's" get it right and get the quality of the repair close to 100%, almost every time.


But remember, osmosis is a cosmetic issues and it is very rare if not impossible for it to become structural.


Some of the first GRP boats, build for the American navy, sank and remained underwater for many years. The were retrieved an found to be in good condition. Sure they had blisters but structurally they were OK.


Epoxy is best. And to prove it ... how many oil rigs, ships bottoms, or any expensive immersed object uses vinyl ester?.... very very few if any. They all use epoxy!.... because it is the best product.... and they can afford it.




Name abridged

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