StugeronSteve
Well-Known Member
Wot, nutters on here? Never.
HOW LONG DOES GRP LAST?
- Thread starter alisdair4
- Start date
andy_wilson
Well-Known Member
F\'rever
If it suffers delamination it can be stripped and re laminated from the outside. Arguably if it gets over stressed and a bit springy you could do the same, plus reinforce from within with stringers.
If the gel coat fades it can be re-gelled or painted.
Whether it will be worth it on a return-on-investment basis is another question.
Apart from the odd one that sinks or burns to the waterline, I'm unsure what is to be done with them.
If it suffers delamination it can be stripped and re laminated from the outside. Arguably if it gets over stressed and a bit springy you could do the same, plus reinforce from within with stringers.
If the gel coat fades it can be re-gelled or painted.
Whether it will be worth it on a return-on-investment basis is another question.
Apart from the odd one that sinks or burns to the waterline, I'm unsure what is to be done with them.
DrBob
Well-Known Member
One thing for certain is that GPR doesnt have a half life of 25000 years and I doubt if it will be good for 00's of years.
In the 70/80's I worked as a development chemist on polyesters for the leading UK manufactures so I know the product.
The long term failure mode (other than fractures caused by impact) is likely to be water, wicking up the glass fibres and destroying the fibre to resin bond - leaving it open to brittle failure of the resin. It is also likely that dynamic flexing will cause microcracking in the resin over time which will weaken the matrix and open a path for water to get into the glass.
Experience shows that many laminates are still good after 40 years. They may well last much longer if made well but I wouldnt count on much more than another 40. Badly made laminates, poorly cured, not wetted out etc, etc will not last that long.
...and by the way, osmosis wasnt caused by cheap raw materials during oil shortages!! It is a combination of poor formulation and/or laminating. These resins are made from maleic anhydride, propylene glycol and styrene (or other acids/glycos). Cheap substitutes were neither available nor used in the 70s and 80s.
Dr Bob
In the 70/80's I worked as a development chemist on polyesters for the leading UK manufactures so I know the product.
The long term failure mode (other than fractures caused by impact) is likely to be water, wicking up the glass fibres and destroying the fibre to resin bond - leaving it open to brittle failure of the resin. It is also likely that dynamic flexing will cause microcracking in the resin over time which will weaken the matrix and open a path for water to get into the glass.
Experience shows that many laminates are still good after 40 years. They may well last much longer if made well but I wouldnt count on much more than another 40. Badly made laminates, poorly cured, not wetted out etc, etc will not last that long.
...and by the way, osmosis wasnt caused by cheap raw materials during oil shortages!! It is a combination of poor formulation and/or laminating. These resins are made from maleic anhydride, propylene glycol and styrene (or other acids/glycos). Cheap substitutes were neither available nor used in the 70s and 80s.
Dr Bob
oldsaltoz
Well-Known Member
[ QUOTE ]
One thing for certain is that GPR doesnt have a half life of 25000 years and I doubt if it will be good for 00's of years.
In the 70/80's I worked as a development chemist on polyesters for the leading UK manufactures so I know the product.
...and by the way, osmosis wasnt caused by cheap raw materials during oil shortages!! It is a combination of poor formulation and/or laminating. These resins are made from maleic anhydride, propylene glycol and styrene (or other acids/glycos). Cheap substitutes were neither available nor used in the 70s and 80s.
Dr Bob
[/ QUOTE ]
G'day Dr Bob,
As a development chemist you would know that 'half life' has absolutely nothing to do with how long an item will last as a structure, be it sound or not.
The reference to older boats developing Osmosis that were built during oil shortages; was the findings of an insurance company after they did an investigation to predict what boats had a higher risk of developing the problem. No doubt they were considering a hike in premiums.
I am yet to find any other event that coincides with the increase in osmosis for certain periods. But would be happy to to get more information on this coincidence.
Avagoodweekend......
One thing for certain is that GPR doesnt have a half life of 25000 years and I doubt if it will be good for 00's of years.
In the 70/80's I worked as a development chemist on polyesters for the leading UK manufactures so I know the product.
...and by the way, osmosis wasnt caused by cheap raw materials during oil shortages!! It is a combination of poor formulation and/or laminating. These resins are made from maleic anhydride, propylene glycol and styrene (or other acids/glycos). Cheap substitutes were neither available nor used in the 70s and 80s.
Dr Bob
[/ QUOTE ]
G'day Dr Bob,
As a development chemist you would know that 'half life' has absolutely nothing to do with how long an item will last as a structure, be it sound or not.
The reference to older boats developing Osmosis that were built during oil shortages; was the findings of an insurance company after they did an investigation to predict what boats had a higher risk of developing the problem. No doubt they were considering a hike in premiums.
I am yet to find any other event that coincides with the increase in osmosis for certain periods. But would be happy to to get more information on this coincidence.
Avagoodweekend......
DrBob
Well-Known Member
Hi Old Salz
If you read carefully I didnt say that half life has anything to do with time to failure.
GRP relies on the glass resin bond and that will fail due to the effect of moisture in time. The material will not retain its ultimate strength for 00's of year.
I was developing gel coats at the time osmosis raised its head. We had osmosis problems as everyone did. Causes were very varied when we could pin it down. It wasnt cheap materials as there was no difference in what we used (or could buy) as the naphtha price went up and down (the marker price for the rms we were using).
Having been in the industry in the 70s, I am surprised GRP lasts so long. If you had asked me 30 years ago would a laminate last to 2006, I would have said "Just About". Looks like we have done a lot better than that!
Dr Bob
If you read carefully I didnt say that half life has anything to do with time to failure.
GRP relies on the glass resin bond and that will fail due to the effect of moisture in time. The material will not retain its ultimate strength for 00's of year.
I was developing gel coats at the time osmosis raised its head. We had osmosis problems as everyone did. Causes were very varied when we could pin it down. It wasnt cheap materials as there was no difference in what we used (or could buy) as the naphtha price went up and down (the marker price for the rms we were using).
Having been in the industry in the 70s, I am surprised GRP lasts so long. If you had asked me 30 years ago would a laminate last to 2006, I would have said "Just About". Looks like we have done a lot better than that!
Dr Bob
fireball
Well-Known Member
Have you run your hull in yet?
PeterStone
Well-Known Member
Thanks for shedding a bit of objective light. Much is said about the indestructible nature of GRP and with so little evidence one way or the other, apart from anecdotal, these discussions are usually inconclusive. We should know much more in another twenty years or so.
Even the best built boats are going to flex and I would have thought that this is going to be the main cause of failure - particularly if boats are being built to a lighter spec nowadays.
However, in my experience of owning older boats - and I have owned four - they weren't all overbuilt with massively thick hulls. So I'd like to question the widely held belief that "they don't build them like they used to".
One of the best moulders in the 60's and 70's was Tyler - I have owned two boats made by them - but by no stretch of the imagination could you say that they were overbuilt. I've still got the lay up spec of my 8 ton "Sprinter" moulded in 1967. She was 31ft 10" long and had topsides of around 10ozs a sq. ft. - maybe 1/3rd of an inch thick. The bottom was about twice that lay up weight I think - I'd need to check to be totally sure - but nowhere would the hull have been as thick as one inch except, perhaps, in the region of the floors. But the mouldings were superb - well wetted out and with a high glass to resin ratio.
The fact that some boats from that era had very thick hulls might be a reflection on the amount of resin used rather than the layup of the glass. Yacht designers don't specify hull thickness - merely layup. Thickness means little. A good moulder aims to use as little resin as possible to achieve maximum strength.
Even the best built boats are going to flex and I would have thought that this is going to be the main cause of failure - particularly if boats are being built to a lighter spec nowadays.
However, in my experience of owning older boats - and I have owned four - they weren't all overbuilt with massively thick hulls. So I'd like to question the widely held belief that "they don't build them like they used to".
One of the best moulders in the 60's and 70's was Tyler - I have owned two boats made by them - but by no stretch of the imagination could you say that they were overbuilt. I've still got the lay up spec of my 8 ton "Sprinter" moulded in 1967. She was 31ft 10" long and had topsides of around 10ozs a sq. ft. - maybe 1/3rd of an inch thick. The bottom was about twice that lay up weight I think - I'd need to check to be totally sure - but nowhere would the hull have been as thick as one inch except, perhaps, in the region of the floors. But the mouldings were superb - well wetted out and with a high glass to resin ratio.
The fact that some boats from that era had very thick hulls might be a reflection on the amount of resin used rather than the layup of the glass. Yacht designers don't specify hull thickness - merely layup. Thickness means little. A good moulder aims to use as little resin as possible to achieve maximum strength.
oceanfroggie
Well-Known Member
[ QUOTE ]
HOW LONG DOES GRP LAST?
[/ QUOTE ]
Ah, quite a fair bit! As long as you'd need anyway. /forums/images/graemlins/laugh.gif
HOW LONG DOES GRP LAST?
[/ QUOTE ]
Ah, quite a fair bit! As long as you'd need anyway. /forums/images/graemlins/laugh.gif
G
Guest
Guest
Doh ..... didn\'t I say that ?????
Deja vue ?
Deja vue ?
oceanfroggie
Well-Known Member
Re: Doh ..... didn\'t I say that ?????
[ QUOTE ]
Deja vue ?
[/ QUOTE ]Is she Charlie Vue's brother? /forums/images/graemlins/laugh.gif
Sorry missed your earlier response /forums/images/graemlins/blush.gif
[ QUOTE ]
Deja vue ?
[/ QUOTE ]Is she Charlie Vue's brother? /forums/images/graemlins/laugh.gif
Sorry missed your earlier response /forums/images/graemlins/blush.gif
G
Guest
Guest
I have a Westerly Nomad, built 1968...........and I mean built! like a brick carsie, no osmosis, no stress cracks, and dry as a chip!
What more could you ask of a 38 year old boat, and despite the sometimes cruel aspersions cast about by certain of the sailing fraternity, she actually sails rather well, leastways, she does if you aren't into racing around the cans etc.
I reckon, they built 'em a lot heavier in the 60's/70's, because they didn't know of any other way of building in the strength they required, which is probably why a lot of boats from that era have lasted so well. Go for a plastic classic!
Unless of course, you happen to know where a Bristol Channel Pilot Cutter is lurking for a couple of quid! /forums/images/graemlins/grin.gif
Best, Charlie.
What more could you ask of a 38 year old boat, and despite the sometimes cruel aspersions cast about by certain of the sailing fraternity, she actually sails rather well, leastways, she does if you aren't into racing around the cans etc.
I reckon, they built 'em a lot heavier in the 60's/70's, because they didn't know of any other way of building in the strength they required, which is probably why a lot of boats from that era have lasted so well. Go for a plastic classic!
Unless of course, you happen to know where a Bristol Channel Pilot Cutter is lurking for a couple of quid! /forums/images/graemlins/grin.gif
Best, Charlie.