Racingfrank7
Well-Known Member
That's exactly what I have been told by people old wiser and in the marine trade with no intrest in what we do with our boat !
End of day it's a personal thing and what ever works / makes u sleep at night !
Drying out...
- Thread starter imac8
- Start date
That's exactly what I have been told by people old wiser and in the marine trade with no intrest in what we do with our boat !
End of day it's a personal thing and what ever works / makes u sleep at night !
oldgit
Well-Known Member
"It is widely recognised and understood that drying the boat for six weeks a year will reduce the onset of Osmosis."
Should somebody mention this to........
The RNLI
The Navy.
Custom and Excise
The Police
Most of the small charter and fishing boats around our coast.
Many of the super yachts around the world ?
Should somebody mention this to........
The RNLI
The Navy.
Custom and Excise
The Police
Most of the small charter and fishing boats around our coast.
Many of the super yachts around the world ?
Racingfrank7
Well-Known Member
2 points there really
Most of the police fire ect ect normaly have boatsheds and do take there boats out or have trailers and they launch them when needed.
And next been why would they care ? They will change them regular enough, there not protecting there investment like we have / need to and who says there boats don't have damp or osmosis ?
Do you think a traffic cop cares about his traffic car the same as his own ??
carlton
Well-Known Member
Not really. It's not their money they're spending.
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Nauti Fox
Well-Known Member
rafiki_
Well-Known Member
oldgit
Well-Known Member
"How do you know?"
Its called .......a survey ...... and you need it for insurance purposes !
Nobody is suggesting that you should not put a plaything ashore if it makes you feel better but in the real world it dont happen.
Would dare to suggest that as working boats tend to kept longer,worked harder and for far more extended periods than hobby boats,the owners may be more concerned than most about longevity.
Have yet to see any of our local plastic fishing/charter/workboat fleet ashore for "drying out" and losing income as a result.
Its called .......a survey ...... and you need it for insurance purposes !
Nobody is suggesting that you should not put a plaything ashore if it makes you feel better but in the real world it dont happen.
Would dare to suggest that as working boats tend to kept longer,worked harder and for far more extended periods than hobby boats,the owners may be more concerned than most about longevity.
Have yet to see any of our local plastic fishing/charter/workboat fleet ashore for "drying out" and losing income as a result.
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Nauti Fox
Well-Known Member
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jfm
Well-Known Member
Agreed. Sure, leaving a boat ashore for a couple of months will reduce the moisture reading but as soon as you crane it back in you're back to where you started within a few days. A lot of surveyors just say what the last guy said, without possessing first hand knowledge. There is nothing wrong at all with a few water molecules swimming around inside your GRP. And we really are talking tiny amounts of moisture here - I'm trying to get my head around Parsifal's story above about having to paint the boot top lower despite carrying more gear. I don't know what Parsifals' boat is made from but I'm a long way from believing that hundreds of kilos of moisture has permanently fallen out of the hull in his ownership compared with the previous ownership, all because the boat now stands ashore for a few months over the winter
Poignard
Well-Known Member
Well it puzzles me too but what other explanation could there be? I had her weight checked last time she was lifted out by a crane and she now weighs the same as other Twisters.
rafiki_
Well-Known Member
I'm missing something here. How do you check for osmosis without lifting the boat? If the boat is never lifted, how do you know there is no osmosis??
I'm sure that workboats are lifted, maintained and popped back in without an osmosis check. This does not mean that osmosis is not present.
penfold
Well-Known Member
What did she weigh before?
Poignard
Well-Known Member
I wonder if a possible explanation may lie in the fact that before I bought her she was berthed in a river, ie in fresh or brackish water but now she is berthed in salt water. As is well known, vessels float higher in saltwater than in fresh.
EME
Well-Known Member
Yes .. and I would have thought conceptually more molecules of fresh water will sneak into the hull than sea water.
oldgit
Well-Known Member
As we frequently go between fresh and salt,there is a noticable change.Most easily spotted cos the fenders start to drag in the fresh water.
In my boat (12m / 9 tons) this amounts to about a 25mm or maybe bit more.
Nauti Fox
Well-Known Member
If I may point out the reply was originally directed at me, to which you have a reply.
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Assassin
Well-Known Member
GRP and gel coats are not actually waterproof and water passes through the gel coat and back out again, this is fairly normal as the molecules of water are small enough to do so. Osmosis occurs when there is uncured resin, the water molecules passing the gel coat attach themselves to the uncured GRP and become too large to pass back through the gel coat and remain on the inside of it.
As temperatures fall and rise these water/resin blisters expand and contract and can form small local cracks around them, this is where the water/GRP molecules force their way into the matting of the GRP and you have osmosis.
Modern boats should be lifted annually and drying them out does help, particularly if you have osmosis or emerging osmosis. Modern boats are much better built then earlier models so there is a very small chance of uncured resin pockets, unlike older GRP boats. Most damage will come from small knocks and impacts which create tiny internal cracks inside the GRP and the water passing through the GRP will enter the matting.
To lift or not? with a newer craft i would say its at the discretion of the owner, on older craft i would say its beneficial.
As temperatures fall and rise these water/resin blisters expand and contract and can form small local cracks around them, this is where the water/GRP molecules force their way into the matting of the GRP and you have osmosis.
Modern boats should be lifted annually and drying them out does help, particularly if you have osmosis or emerging osmosis. Modern boats are much better built then earlier models so there is a very small chance of uncured resin pockets, unlike older GRP boats. Most damage will come from small knocks and impacts which create tiny internal cracks inside the GRP and the water passing through the GRP will enter the matting.
To lift or not? with a newer craft i would say its at the discretion of the owner, on older craft i would say its beneficial.
Jim@sea
Well-Known Member
I wish I had printed out what somebody had put on this forum a few weeks ago about their experience when they bought a GRP boat which had spent over 10 years in the water and sank when they were moving it to where their mooring was. Aparrently their hull had become "porous"
They mentioned the make of boat and gave a detailed description of how the boat slowly filled up with water.
And I can understand where they are coming from. In France I bought a 21ft GRP Boat which was 20 years old and I decide to remove the antifouling back to the original GRP. On close inspection of the hull there were hundreds of scratches some quiet deep which I realised were probably made when the boatyard had given a "Numpty" a straight edged scraper and told them to scrape the hull clean of antifouling and re apply another coat of antifouling.
Fortunatly this boat had been taken out every winter and stored undercover and had been up for sale out of the water for 3 years at too much money. I got round the problem of the scratches by sanding the hull down, and painting the hull (below the waterline) with 2 coats of 2 pack Ford Diamond White which sealed the hull,, then re applied antifouling.
I did something similar in 1982. I had bought a 1973 "Prestigious" 33 ft GRP Ketch. And it had a faulty hull. It turned out that in just 6 years to 1978 "Osmosis" had been noticed and the hull had been repaired and repainted with ordinary single pack Paint. Unfortunatly in 1978 " 2 pack was not widely used on boats whereas in my bodyshop we had been using it to spray cars.
Anyway I had bought the boat 3 years after the repair, I thought the "Faded Hull" was the affect of 9 years sun use and I could T cut it back. But then I noticed that the "Osmosis" had returned around the waterline.
So what I am saying is that dont assume that your GRP boat is impervious to water when left in it for extended periods.
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