new grp resin or hardener in mid 80 s

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michael11

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New user so please be patient. I am doing research on the boat market, prior to purchase of a boat. Not sure what sort yet but it will not be a new one. I understand that a different resin or hardener was used from about mid 80 s . to improve the resistance to osmosis ( I may be talking rubbish if so please say ).
My question is how do I tell if a boat was built with this resin/ hardener ? and has time confirmed it was better.
 
[ QUOTE ]
( I may be talking rubbish if so please say ).

[/ QUOTE ] I think you may be thinking or orthophthalic and isophthalic resins, but I thought that change was earlier than the mid eighties.

Unpigmented resins have aslo been used as it is/was thought/discovered that unpigmented resin was less prone to osmosis,

Other factors, including proper mixing, moulding shop temperature etc etc have all come under scrutiny.

I do not know how you would tell what resin had been used or what other factors would be affecting a hull. I think all you can probably do is take each boat on its merits and a moisture test perhaps.

Sorry not a lot of hard fact there, but when you have researched all this thoroughly you should have all the info for a good magazine article. I look forward to reading it.
 
[ QUOTE ]
i assume they arrived in the order of previous post

[/ QUOTE ] Yes I think so. i should have pointed out that there are an number of books available that might be of interest to you in particular several by Tony Staton-Bevan who is a surveyor who has specialised in grp yachts.
 
I looked into this too when buying my boat a couple of months back.
I drew to the conclusion that you really need to take it on a boat by boat basis as a 'newer / better' resin on a poorly mixed and poorly built boat which has been left in the water for long periods without being hauled out will undoubtedly be more prone to osmosis than the 'older' resin which could have been prepared better and the boat treated better.

Get a good survey and listen to the surveyors comments on the moisture readings. But do remember - in the US they don't treat osmosis (no boat has ever sunk as a direct result of it so why bother!) - maybe on this side of the 'pond' we're a bit too cautious?

Jonny
 
I take on board what you are saying about how the boat has been treated and the moisture readings, for a specific boat , i just wondered if it was something that should be taken into account. The problem with oz is being able to sell it again without very expensive work, (i know shud nt worry about selling before ive bought one)
 
I was under the impression that the problems associated with g.r.p of the early to mid eighties were more to do with drastic cost increases in oil used to produce the resin leading to 'dry' laminates around this time, My boat was built around 1972 and shows no sign of blistering or wicking despite being left afloat in an abandoned state for several yrs. Later boats are certainly built a lot lighter these days, Not sure if this is down to better construction methods or more a case of building to a minimum standard/price. Mike
 
I was always under the impression that leaving the gelcoat unpigmented was just to help spotting air bubbles in it?

Anyway. If you're thinking of buying an older boat, see if the particular make you're looking at has a history of osmosis. I hear some older boats seem to be able to tolerate quite high moisture contents for years without ever developing osmosis.
 
If your looking to get a goodover view of GRP construction, positives and negatives, try and get hold of a copy of "fibreglass boats" by Hugo Du Plessis - I borrowed it from the library, thought it was so good I bought a copy!
 
thanks for all the replies i wiil try to get hold of the books highlighted . i think understanding if a particular model of boat has a history of problems is a very good idea as that is an indication of their process control

thank for all yor help /forums/images/graemlins/smile.gif
 
Hi Michael,
Isophthalic resins were introduced in the late 1980's, as they have better water resistance than the older orthophthalics. Around this time, resin manufacturers also became increasingly aware of other casues of osmosis; primarily high molecular weight alcohols, which absorb and retain moisture, and casue both blistering, and high moisture readings.

Sadly, very few people understand this process, which IMHO is why osmosis continues to be a problem.

Have a read of the following for some more information.

www.passionforpaint.co.uk/downloads/osmosis3v6.pdf.

Nigel.
 
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