Boat with osmosis - buy or not?

[Mark-1]

I don't think Mark-1 has the quote "There are absolutely no osmotic forces involved" correctly attributed.

It's not a direct quote but I'm fairly certain that HdP rules osmosis out. From memory HdP says the process involved cannot be osmosis or at very least it cannot start out as osmosis. IIRC he says that this is because salt water is a strong solution and in the early stages (if the process really were osmosis) then the process would work the opposite way round.

Maybe someone with the book to hand can confirm or correct my feeble memory.

HdP is one of many people around (eg on the web), who recommend individual grinding back of blisters (up the the several hundreds mark) in preference to replacing the gel coat. This is something that can be done by the owner. His remarks about cowboys removing glassfibre up to an inch deep by the enthusiastic application of sand blasters makes that seem preferable even if you have to do some every year.

That's my recollection too. I think he says that when the yards skim back layers of the GRP they're taking off a more or less unknown quantity of material and putting back a more or less unknown quantity of material. Certainly convinced me that less is more in terms of osmosis treatment.

Please, nobody take my memory as gospel - get hold of the book yourself.

 

[Phideaux]

Well, istm you have described osmosis.

The gel coat allows water molecules through without permitting the solute back out so it is acting as a semi permeable membrane despite appearances to the contrary.

Boo2

I think you'd find that the gel-coat will allow water to come out. this is why a moisture test on the gel-coat can give different readings between when you first lift out of the water and after having her stood on the hard for a few months. Either way, water gets in, reacts with styrene (or other binders) and may cause damage, either cosmetic or deeper into the laminate. It's probably not a short-term worry, but if you're keeping the boat for a while then it's probably best to put some money aside to have a proper HotVac treatment. Alternatively, just check the hull at the end of each season and undertake any remedial work to blisters that have shown up since the previous year. Be assured that if there's evidence of blisters at the survey, any potential buyer will want to deduct the cost for a professional anti-osmosis treatment from your asking price when you come to sell.

 

[alahol2]

From memory HdP says the process involved cannot be osmosis or at very least it cannot start out as osmosis. IIRC he says that this is because salt water is a strong solution and in the early stages (if the process really were osmosis) then the process would work the opposite way round.

The fact that blisters seem to occur much more rapidly in fresh water implies, to me, that the process is osmotic as osmotic pressure would be that much greater than with salt water.
I don't think any of the experts opinions seem to explain why many (most?) boats don't suffer from osmosis.

 

[john_morris_uk]

I can't imagine getting the full cost of £7k off the price. If that were the case, the seller might as well do the work and then load the price for having the guarentee. The boat would be in better than average condition.

Personally our last two boats have had some signs of blistering in some places - but I haven't worried about it for more than a few seconds. On the Sigma 33 I had the bottom grit blasted and it revealed LOTS of blisters that the grit had opened up. I filled them all with thickened epoxy and faired the hull before putting two coats of Primocon and two coats of A/F. When we came to sell, the very reputable surveyor didn'tfind a thing wrong with it.

Our current hull had 'some areas with slightly high moisture readings', but the surveyor told us not to worry about it and we haven't. When I had all the A/F removed 9this time with the much gentler Soda blasting' there were a few tiny blisters that I didn't even bother filling and fairing as they were so small in insignificant.

The moral of all this to the OP is that Colvic Hulls are so solid that you shouldn't be worrying about it at all. If the rest of the boat is OK, you could try and get some reduction in the price against future treatment, but if I was selling I wouldn't be giving the full £7k off the price, so do the best that you can. The whole price thing is about what you think its worth vs what they think its worth anyway - you just have to settle at an agreed figure.

To those who have said 'walk away - there are lots of boats' my feeling is that, yes there are lots of boats, but lots of them are poorly presented at unreasonably prices.' If the blisters are the only thing stopping you from buying this particular Colvic Watson - see the above...

 

[Mark-1]

The fact that blisters seem to occur much more rapidly in fresh water implies, to me, that the process is osmotic as osmotic pressure would be that much greater than with salt water.
I don't think any of the experts opinions seem to explain why many (most?) boats don't suffer from osmosis.

Again, going purely from memory HdP does address freshwater/salt water issue. As Phideaux says it's not critical. It gets in. The process by which it enters doesn't really matter.

From memory HdP is clear on why most boats don't suffer from osmosis. he says blisters only occur where there is a void the the GRP. No void, no blister. So old layups didn't always have voids and modern layups could completely have eliminated voids.

Again none of this is my opinion, I'm just quoting my half memory of HdP.

 

[ukmctc]

osmosis has never sunk a boat yet....buy it and enjoy it, its only a problem if your into the bs.

 

[Lucky Duck]

Betterment

I can't imagine getting the full cost of £7k off the price. If that were the case, the seller might as well do the work and then load the price for having the guarentee. The boat would be in better than average condition.

I'm glad somebody pointed that out and I don't think it unreasonable for the buyer to 'contribute' to part of the cost of the treatment costs.

 

[Twister_Ken]

Disagree. I'd expect the vendor to put the boat in good order, or to compensate the buyer in full for doing so post-purchase. In this case, the buyer only seems to have the vendor's word that it can be put right for £7K - if I were the buyer and were serious about proceeding, I'd want to get my own quote for the work.

 

[yacht surveyor]

Also have a look at the free download of the "Osmosis primer" from Nigel Clegg. He had a pair of articles about osmosis in PBO if I remember correctly in about November 2007.

He is very experienced with osmosis. His primer can be found here.

It explains what is going on in a relatively easy to read and understandable way. It also has a good outline of treatment methods (note that no osmosis treatment can be called a repair).

 

[Lucky Duck]

Disagree. I'd expect the vendor to put the boat in good order, or to compensate the buyer in full for doing so post-purchase. In this case, the buyer only seems to have the vendor's word that it can be put right for £7K - if I were the buyer and were serious about proceeding, I'd want to get my own quote for the work.

I agree regarding getting a second quote however if the engine was found to be knackered and beyond repair, should the vendor be expected install a brand new one without any recognition from the buyer that was is now installed is significantly better than a 20 year old unit in working condition?

FWIW my first 'proper' boat was one of the British Hunters built in the mid 1990s that suffered from the gel-coat issues. The cost treatment was about 3k and the purchaser contributed about a third as he was now getting a boat with a 5 year guarantee.

 

[Rivers & creeks]

I'm glad somebody pointed that out and I don't think it unreasonable for the buyer to 'contribute' to part of the cost of the treatment costs.

I disagree. I would expect when buying a boat to buy it without it needing several thousands spent on it, unless that was reflected in the price. This boat is advertised without such a built in reduction. The analogy with the knackered engine is only comprable if the boat with the knackered engine is already discounted.

Thank you for all the posts, I've found it very helpful. The decision we've made is to let the vendor resolve the issue, when he has done the treatment we'll reassess. In the meantime we're free to look elsewhere, he may well find it easier to sell once he's done the treatment but to be honest, put two boats next to one another. One has absolutely no signs of osmosis; the other has just had all the gel coat taken off and replaced having had a good case of osmosis and has a 5 year "guarantee". They are identical in every respect - which would you buy? I'd buy the untreated one like a shot - she was built so well she never needed treatment. Who knows what's lurking under the new gelcoat on the other one? I don't agree she's been made better, just put back to how she should have been. Her only benefit is having a smooth bottom.

 

[Caer Urfa]

I wish I could buy a flipping boat with my head for once, so please just tell me to walk away. We have fallen for it though.
we found a beauty of a Colvic Watson 31.6 but on close inspection the hull has a number of blisters about the size of a 5p / 20p piece. Or should I just leave it and find a boat that's not got "it"?

Hello Muddy Paws

I have been reading some of the replies with interest and although interesting I do not think you wanted a lecture in the 'Causes of Osmosis'.

Colvic Watson hulls and battle tanks have one thing in common 'they are both almost bullet proof'.

We have all seen the description ‘heavy layup’ but what does that mean?
It’s a technique and part of the mould process when constructing a mould in GRP (Glass Reinforced Plastic) and G L Watson and Colvic Craft were very careful on this point when designing the Colvic Watson hulls, as all the hulls had a very heavy layup where the hand layed polyester resin reinforced woven matting used was from 24.5oz, 20.5oz, 16.5oz and 10oz per sq/ft used from the keel upwards to form a rigid bonded hull and coach roof.

The hulls were then heavily further constructed and strengthened with side and bottom transverse bearers also bonded into the hulls for extra strength and the moulds were manufactured at the time by Colvic in a special temperature controlled moulding building to ensure the correct mould process was carried out making the hulls far in excess of Lloyds specifications for the hull design at the time.

During my 'Pre-Buying Inspection Visits on Colvic Watsons which I do part time only on Colvic Watsons for customers I have seen dozens over the years but only two with part signs of Osmosis, If I knew the name of the boat you are looking at this may also help.

If you are so concerned and 100% sure the boat has Osmosis then yes it is more than reasonable to negotiate a more reasonable price, and I agree with other posts that if the hull is taken back to the original gel coat and the spots treated accordingly and the boat left to dry out for a couple of months then treated by cleaning off with International No7 thinners then with 5 coats of Gelshield 200, 1 x Primocon, 2 x antifoul she will probably last you out!

My last advice is 'Read slowly the surveyors report and understand what he is saying' AND discuss his findings with him (it's amazing how many people do not), Negotiate the price and get the hull done either by yourself or others, Then you will have a fine boat!

If I can help further drop me a PM

Mike

 

[jwilson]

My 2p's worth.....

This is sanded again to give a smooth finish and your anti foul is applied. The epoxy if done slowly at the correct temperature, is far more "waterproof" than fibreglass. You may note that your boat will float considerably higher when you get her back in the water...... to emphasise the amount of water present in the hull before drying out. This was the case here and it was very noticeable. (He won many subsequent regattas and claims the long dry out has given him an edge)

The amount and weight of water in the GRP hull is small - maximum maybe 2% of the weight of the dried out GRP at worst case. Any alteration of the waterline will be insignificant. Any visible change in waterline is more likely to be due to clearing junk out of the boat when she went into the boatyard - or painting the waterline in at a different height after the peeling/coating job!

The hull will be slightly stiffer after drying, and this does slightly affect speed in a chop with less hull panel flexing. Racers like ultra-expensive stiff carbon fibre hulls for that reason, as well as low weight.