Polyester hydrolisation (aka "osmosis")
- Thread starter mortehoe
- Start date
Danny Jo
Well-Known Member
Thanks Stemar - a very useful link. I learnt a lot from this article on the yachtsurvey.com site
jaylo264
Well-Known Member
osmosis/old westerlys
Our 1966 Westerly 22 weighed almost the same on lifting out of the caledonian canal last autumn ( just under 2 tonnes, said crane operator) as she did on going in there 4 years previously.
No blisters, and presumably not much wicking?
Lots of freshwater weed, tho.
I am still much more worried about never having had anodes...........
jaylo264
Our 1966 Westerly 22 weighed almost the same on lifting out of the caledonian canal last autumn ( just under 2 tonnes, said crane operator) as she did on going in there 4 years previously.
No blisters, and presumably not much wicking?
Lots of freshwater weed, tho.
I am still much more worried about never having had anodes...........
jaylo264
catmandoo
Well-Known Member
jwilson
Well-Known Member
boatmike
Well-Known Member
doug748
Well-Known Member
I have told this story before but..
I have a survey for my boat dating back to the late 80's it warns that the WC bowl shows:
"early signs of osmotic blistering"
I have not been too worried as it is ceramic.
boatmike
Well-Known Member
Just shows how careful you have to be dunnit??
D
Deleted member 36384
Guest
That's exactly the advice I gave to my mate, "Tell her you got them off the toilet seat." And I thought it was just a crock of $hit.
Is that the time, best catch the bus then.
mortehoe
Well-Known Member
pre-1972 resins
"There are two seperate issues but not the two you mention. There is blistering which is cosmetic only, and there is hydrolysis of the resin which is eventually structural. You can have hydrolysis without the blisters but not the other way round."
It has been found that the "launched" boat's hull was laid (frg) in 1969.
It is reported that anything pre-1972 fibreglas's hardeners can't have the same "osmosis" or "polyester hyrolisaton (sp = Am or UK)
N
"There are two seperate issues but not the two you mention. There is blistering which is cosmetic only, and there is hydrolysis of the resin which is eventually structural. You can have hydrolysis without the blisters but not the other way round."
It has been found that the "launched" boat's hull was laid (frg) in 1969.
It is reported that anything pre-1972 fibreglas's hardeners can't have the same "osmosis" or "polyester hyrolisaton (sp = Am or UK)
N
Crabman
Well-Known Member
Try Gurit. I purchased a boat last year and it had patches of osmosis . The surveyor used a moisture meter and also used thermal imaging to give a picture of the infected areas. International yacht surveys. I was very happy with there services. The after service was very good.
mortehoe
Well-Known Member
To everybody that replied ... Many Thanks .... Now read on ....
Several of the posts have confirmed exactly what happened post the 5th survey from the same YBDSA "approved" Surveyor whose 1996 survey said exactly the same then as it did in November 2009 ....
A 2nd Surveyor was appointed (by me: Nov 2009) without the knowledge of either the boatyard (selling the boat) or the 1st Surveyor appointed by the buyer. The 2nd Surveyor was soley tasked to take external and internal readings of the hull both below and above waterline with a Sovereign Quantum Marine Moisture Meter: There was virtually no difference between any of the readings. His report said that the moisture readings "were both consistant and normal for the age of the casting........ In my opinion there is no evidence in this hull either below or above the waterline of any discernable hydrolisation .........."
In my opinion, I was conned into selling my boat with an immediate effictive 18% discount by the 1st Surveyor ..... His 2 applicable suvey comments follow:
July 1996 : ..........."the base cells probably partially unwetted underlying the epoxy could evidence signs of osmosis so resulting in the very high moisture content reading"
Nov 2010: Same Surveyor; Same boat:.......
" the base cells underlying the epoxy exhibit signs of being unwetted evidence signs of osmosis so resulting in the unusually high moisture content readings "
No blisters over 40 years and yet there is a Surveyor out there who manicures surveys repeatedly to fill his pocket by just stating the word of doom "osmosis" without specifying what resins or hardeners were used at the date of the lay-up - or any scientific evidence to say that with the resin/hardener/chemical combination used in 1969 that "osmosis" can't happen/exist.
Several of the posts have confirmed exactly what happened post the 5th survey from the same YBDSA "approved" Surveyor whose 1996 survey said exactly the same then as it did in November 2009 ....
A 2nd Surveyor was appointed (by me: Nov 2009) without the knowledge of either the boatyard (selling the boat) or the 1st Surveyor appointed by the buyer. The 2nd Surveyor was soley tasked to take external and internal readings of the hull both below and above waterline with a Sovereign Quantum Marine Moisture Meter: There was virtually no difference between any of the readings. His report said that the moisture readings "were both consistant and normal for the age of the casting........ In my opinion there is no evidence in this hull either below or above the waterline of any discernable hydrolisation .........."
In my opinion, I was conned into selling my boat with an immediate effictive 18% discount by the 1st Surveyor ..... His 2 applicable suvey comments follow:
July 1996 : ..........."the base cells probably partially unwetted underlying the epoxy could evidence signs of osmosis so resulting in the very high moisture content reading"
Nov 2010: Same Surveyor; Same boat:.......
" the base cells underlying the epoxy exhibit signs of being unwetted evidence signs of osmosis so resulting in the unusually high moisture content readings "
No blisters over 40 years and yet there is a Surveyor out there who manicures surveys repeatedly to fill his pocket by just stating the word of doom "osmosis" without specifying what resins or hardeners were used at the date of the lay-up - or any scientific evidence to say that with the resin/hardener/chemical combination used in 1969 that "osmosis" can't happen/exist.
boatmike
Well-Known Member
No blisters over 40 years and yet there is a Surveyor out there who manicures surveys repeatedly to fill his pocket by just stating the word of doom "osmosis" without specifying what resins or hardeners were used at the date of the lay-up - or any scientific evidence to say that with the resin/hardener/chemical combination used in 1969 that "osmosis" can't happen/exist.
No surprises there then. Unfortunately these days it's rare to find a surveyor talking sense. "If in doubt, throw it out" seems to be the pattern these days. I have even seen the dreaded "osmosis" word in a survey done on a boat that (unknown to the surveyor) was built ashore in a yard by the owner and had never been afloat! You can't blame them for covering their butt when they can be sued for saying something is OK when it isn't but this word has been misquoted and the whole subject so misunderstood that it has become a mantra chanted by the whole bloody industry and owners alike.
Two basic rules.1. If its wetter on the bottom than the top that just shows that it has been in the water. and 2. If it aint got blisters don't try mending it! That's not to say some boats don't truly suffer blistering caused by osmosis, but not half as many as those doomed in surveys. By the way, don't assume that using any combination of resin and re-inforcement used in 1969 or any other time means it can't happen. It can. It's just not as prevalent as surveys would suggest.
No surprises there then. Unfortunately these days it's rare to find a surveyor talking sense. "If in doubt, throw it out" seems to be the pattern these days. I have even seen the dreaded "osmosis" word in a survey done on a boat that (unknown to the surveyor) was built ashore in a yard by the owner and had never been afloat! You can't blame them for covering their butt when they can be sued for saying something is OK when it isn't but this word has been misquoted and the whole subject so misunderstood that it has become a mantra chanted by the whole bloody industry and owners alike.
Two basic rules.1. If its wetter on the bottom than the top that just shows that it has been in the water. and 2. If it aint got blisters don't try mending it! That's not to say some boats don't truly suffer blistering caused by osmosis, but not half as many as those doomed in surveys. By the way, don't assume that using any combination of resin and re-inforcement used in 1969 or any other time means it can't happen. It can. It's just not as prevalent as surveys would suggest.
mortehoe
Well-Known Member
".......By the way, don't assume that using any combination of resin and re-inforcement used in 1969 or any other time means it can't happen. It can. It's just not as prevalent as surveys would suggest."
BoatMike, and everybody else,
This thread ought to be posted complete in YM as an example of basic information that every yottie ought to be aware of. All we now need to know are the moisture reading numbers so that we can be surveyors of our own hulls/topsides/everything FRP as well .....
How can I print it out in one fell swoop ?????
Cheers,
N
BoatMike, and everybody else,
This thread ought to be posted complete in YM as an example of basic information that every yottie ought to be aware of. All we now need to know are the moisture reading numbers so that we can be surveyors of our own hulls/topsides/everything FRP as well .....
How can I print it out in one fell swoop ?????
Cheers,
N
boatmike
Well-Known Member
Two things there mort...
Firstly you are not going to get a thread like this posted in YM because they have to maintain a neutral stance. Some of the opinions on here (including mine) would be seen as prevocative to say the least. The truth often just ain't popular!
Your practical point about numbers is easier to answer.
Firstly there are several different meters around and the scales differ. None of the numbers are absolute readings though and there is no right or wrong reading. All meters should be recalibrated to a known reading ideally on a test piece that is representative of the layup and known to be fully cured and dry and the vessel compared with that. Of course that is not practical with a boat normally and would require a variety of test coupons to represent the various thicknesses and layup variations a surveyor might see. It is therefore usually a second best alternative to test the topside hull first at positions well above the waterline down to a point just above it. Usually the structure there is of pretty uniform thickness and layup and should be fairly dry. Then progress with readings below the waterline down to as low as practical on the bottom. Some variation will be seen usually as the bottom is often thicker laminate, but a rapid rise over a short distance or a big variation between the average bottom to topsides is an indication of high moisture. As I have said already even this does not necessarily indicate a problem. Remove all weed and antifoul and clean the test area and come back in a months time. Usually the reading will have fallen. If it hasn't this MAY indicate a problem.