Jump to content

Plastic boats


placoman

Featured Posts

15 hours ago, Dr Bob said:

Still not quite right!

Osmosis occurs when there is a void in the laminate. This could be a microscopic air bubble or a big void caused by poor layup technique. The most common cause of big voids is where the glass mat (or glass rovings) were not rolled out well enough so the polyester did not wet the glass out completely thus leaving a dry area. Once the hull is in the water, the water then forces its way through the gel coat via osmotic pressure (which is very great) into that area of void and keeps coming swelling the void considerably. The gel coat will influence the speed of the flow of water but not that much. This may sound bad but it isnt really. In the days when people hand laid up using chopped strand mat (or woven roving), it was usually a very thick laminate that will last 50 years plus. In recent years where GRP boats are made with much thinner laminates, they tend to use resin injection or vacuum infusion or someother fancy technique which avoides the incidence of voids. Osmosis is not really a structural issue.

Structural problems tend to occur when the hull has has impact damage which cracks the gel coat and therefore opens a path for water to see the glass fibres, with water then 'wicking' along the fibres destroying the glass to resin interface and hence weakens the laminate. This is not osmosis. Poor workmanship when laying the gel coat can make this more likely to happen.

There was a 'rash' of high incidence of osmosis in the 70's which may have been partly due to some dubious gel coats on the market (despite my comment above that the gel coats influence is low) - but that is another story. I spent quite a few years in the late 70's developing gel coats for one of the 3 big UK manufactures.

If you read what I put I am mostly right because you have said the magic words poor layup bubbles present all due to poor workmanship. Late boats seem to be made from epoxy which I am told is completely waterproof [if there is such a thing]

I have removed all the floor from my broads cruiser and the hull is in very good condition no softness or anything, it is the product of the 80s and has a very thick layup. I suppose that lack of antifouling must also have a place in hull deterioration?

Link to comment
Share on other sites

3 hours ago, peterboat said:

If you read what I put I am mostly right because you have said the magic words poor layup bubbles present all due to poor workmanship. Late boats seem to be made from epoxy which I am told is completely waterproof [if there is such a thing]

I have removed all the floor from my broads cruiser and the hull is in very good condition no softness or anything, it is the product of the 80s and has a very thick layup. I suppose that lack of antifouling must also have a place in hull deterioration?

Even boats which have epoxy (be it a coating or epoxy resins) will still eventually start taking on moisture. It vastly improves the timescale but is not a magic potion to completely stop the process of osmosis taking place.

The thickness of the layout has little to do with the rate at which osmosis will take place.

Link to comment
Share on other sites

4 hours ago, carlt said:

2 winters on a Dawncraft 27 heated by a Taylor's paraffin heater.

 

 

attachment.php?attachmentid=107107&d=143

Toasty warm and no condensation.

The boat is long gone but I still have the heater

That's a nice looking little heater.

We are thinking that a couple of these drip fed diesel heaters will be fitted to our next boat. One in the rear saloon and the other in the master cabin at the front of the boat.

https://www.kurandamarine.co.uk/dickinson-heating-cooking/dickinson-diesel-heaters/newport-diesel-heater-kit-kmd00-new-kit-dickinson

Not as pretty as the Taylors by a long stretch but should do part of the job of heating the boat quite nicely.

Link to comment
Share on other sites

Just now, Naughty Cal said:

That's a nice looking little heater.

We are thinking that a couple of these drip fed diesel heaters will be fitted to our next boat. One in the rear saloon and the other in the master cabin at the front of the boat.

https://www.kurandamarine.co.uk/dickinson-heating-cooking/dickinson-diesel-heaters/newport-diesel-heater-kit-kmd00-new-kit-dickinson

Not as pretty as the Taylors by a long stretch but should do part of the job of heating the boat quite nicely.

The Taylors is pressurised, not drip fed.

It is effectively a Primus stove sat under a big ceramic element...though it is a lot quieter than my Primus.

We had a Dickinson diesel heater and a cooker in the lifeboat and they were wonderful bits of kit.

We didn't really need the heater because the cooker fed rads but it was shiny and the plumbing was already in place where a defunct Refleks had sat.

Link to comment
Share on other sites

1 hour ago, Naughty Cal said:

Even boats which have epoxy (be it a coating or epoxy resins) will still eventually start taking on moisture. It vastly improves the timescale but is not a magic potion to completely stop the process of osmosis taking place.

The thickness of the layout has little to do with the rate at which osmosis will take place.

I started sailing and canoeing when I was 11, I continued doing both until I left the forces at 38. I have built more canoes and repaired more boats than I can remember, I have had numerous fibreglass cars, I made a new shell for one from scratch, after it was badly damaged in a crash, my last 2 fast cars [C4 corvette and a marlin hunter] are both fibreglass, my friend owns a fibreglass repair shop in Handsworth. For the last 40 odd years I have been a fully paid up member of the sticky back hand club! Poor layup has for the boats and canoes I have seen [hundreds] has always been the cause of the osmosis, you can on canoes see the holes in the fibreglass where its not been rollered properly and know at a later date it will come back and bite you. Modern production methods as Dr Bob says has largely cured this with vacuum bags pressure and ovens etc. My own 35 year old broads cruiser which has been in water all its life as a hire craft, has no soft spots, but Alfacraft were a good builder with a heavy layup. It helps to have a dry warm workshop when building boats in fibreglass but that doesnt always happen does it?

Link to comment
Share on other sites

1 hour ago, peterboat said:

I started sailing and canoeing when I was 11, I continued doing both until I left the forces at 38. I have built more canoes and repaired more boats than I can remember, I have had numerous fibreglass cars, I made a new shell for one from scratch, after it was badly damaged in a crash, my last 2 fast cars [C4 corvette and a marlin hunter] are both fibreglass, my friend owns a fibreglass repair shop in Handsworth. For the last 40 odd years I have been a fully paid up member of the sticky back hand club! Poor layup has for the boats and canoes I have seen [hundreds] has always been the cause of the osmosis, you can on canoes see the holes in the fibreglass where its not been rollered properly and know at a later date it will come back and bite you. Modern production methods as Dr Bob says has largely cured this with vacuum bags pressure and ovens etc. My own 35 year old broads cruiser which has been in water all its life as a hire craft, has no soft spots, but Alfacraft were a good builder with a heavy layup. It helps to have a dry warm workshop when building boats in fibreglass but that doesnt always happen does it?

What moisture content is your Alphacraft hull showing?

I ask as we are looking to get an Alphacraft 35 which will be of 80's or 90's vintage so will be useful to judge how moisture contents compare. 

Link to comment
Share on other sites

21 minutes ago, Naughty Cal said:

What moisture content is your Alphacraft hull showing?

I ask as we are looking to get an Alphacraft 35 which will be of 80's or 90's vintage so will be useful to judge how moisture contents compare. 

Watch the windows around the stern because they steer from the front but turn from the stern they tend to pick up damage around the stern. Mine had leaks on the rear window and at the stern in the opposite corner to the steering wheel. These water leaks have caused big damage to the ply floor. Also the engine hatch is another water leak waiting to happen. Good luck with your search plenty were built and many survive in good condition. 

I have stripped everything out of mine so all repairs will be watertight and last, the hull is in very good condition shame about the rest 

1 hour ago, rasputin said:

I am 52 and have had a shit most days, I wouldn't know how to cure bowel cancer though.

But if you were a surgeon it might have helped

Link to comment
Share on other sites

1 hour ago, peterboat said:

Watch the windows around the stern because they steer from the front but turn from the stern they tend to pick up damage around the stern. Mine had leaks on the rear window and at the stern in the opposite corner to the steering wheel. These water leaks have caused big damage to the ply floor. Also the engine hatch is another water leak waiting to happen. Good luck with your search plenty were built and many survive in good condition. 

I have stripped everything out of mine so all repairs will be watertight and last, the hull is in very good condition shame about the rest 

But if you were a surgeon it might have helped

What is the hull moisture content like?

Not interested in water leaks!

Link to comment
Share on other sites

1 hour ago, rasputin said:

I believe we are in a similar position with osmosis, a lot of people seem to know all the answers, some perform expensive surgery.

Until I lift the boat out I won't know for sure but the hull from the inside is rock solid. The last survey reported no osmosis but that was 5 years ago so fingers crossed 

6 minutes ago, Naughty Cal said:

What is the hull moisture content like?

Not interested in water leaks!

It's wet on the outside and dry inside with no blistering softness or any other woes

Link to comment
Share on other sites

4 minutes ago, peterboat said:

Until I lift the boat out I won't know for sure but the hull from the inside is rock solid. The last survey reported no osmosis but that was 5 years ago so fingers crossed 

It's wet on the outside and dry inside with no blistering softness or any other woes

So you don't actually know if it has osmosis or not then?

There is far more to the process of osmosis then blistering. Some boats will suffer for years before showing any signs of blistering.

You need it moisture testing to find out if it is suffering high moisture content.

It would be a surprise to find an older boat that wasn't suffering from high moisture content unless it has been ashore for most of its life!

Link to comment
Share on other sites

2 hours ago, Naughty Cal said:

So you don't actually know if it has osmosis or not then?

There is far more to the process of osmosis then blistering. Some boats will suffer for years before showing any signs of blistering.

You need it moisture testing to find out if it is suffering high moisture content.

It would be a surprise to find an older boat that wasn't suffering from high moisture content unless it has been ashore for most of its life!

Give me  a break I still have to take out the poo tank! It's integral to the hull so when that's removed I will be able to do a moisture check and I will let you know the results 

  • Happy 1
Link to comment
Share on other sites

3 hours ago, Naughty Cal said:

There is far more to the process of osmosis then blistering. Some boats will suffer for years before showing any signs of blistering.

You need it moisture testing to find out if it is suffering high moisture content.

It would be a surprise to find an older boat that wasn't suffering from high moisture content unless it has been ashore for most of its life!

This is not correct. Osmosis causes blisters. The water flows into a void via osmotic pressure and keeps flowing in until a blister is formed. The water then doesnt move out to other parts of the laminate as the osmosis process drives 'low electolyte water' into high electrolyte areas - so it stays there. Most osmosis is due to small voids in the laminate so it ends up as a 'pox' on the gel coat surface. THis then is a cosmetic problem and will never sink the boat particularly if the laminate is thick. Occasionally you will see a boat with poor layup and big voids that will cause a few very large blisters on the gel coat. I would avoid this type of problem as there 'may' be some structural issues.

I am not sure a boat that is not showing blisters yet  is suffering.

The cause for concern is when the gel coat is damaged due to impacts ie star crazing or cracks where water then has direct access to the laminate. Water then 'wicks' up the glass fibres and destroys the resin to glass interface which therefore weakens the laminate. This is where the problem of high water content can cause structural problems and it is not osmosis. If I was buying a grp boat, I would not be too bothered about osmotic blistering if it was over a large area of the boat. It is easy to repair and if it is a decent thickness, it will only be cosmetic. If however there were 2 or 3 sections with large blisters ie 3''+ across or clear problems of gel coat cracking/exposed laminate/damaged laminate then I would be very interested in water contents.

You seem to be building up osmosis to be the main problem to look for on grp hulls. It isnt. Poor gel coats, poor layup, poor cure, unrepaired damage etc are far worse problems leading to reduction in tensile and flex strength of the laminate and a reduced lifetime. In general though, grp lasts for years and a good hull is going to be fine 50 years later as most boats built in the 70s/80s/90s had hulls so over designed. Shame grp boats look so tatty when they get old.

Edited by Dr Bob
  • Greenie 1
Link to comment
Share on other sites

GRP boats do not need to look tatty as they get older. They only need a good going over with polishing compound to bring them up like new. The problem is a lot of people can't be arsed to put in a bit of effort and compound their boat, or even worse they paint the poor thing.

Phil

  • Greenie 1
Link to comment
Share on other sites

9 hours ago, Dr Bob said:

This is not correct. Osmosis causes blisters. The water flows into a void via osmotic pressure and keeps flowing in until a blister is formed. The water then doesnt move out to other parts of the laminate as the osmosis process drives 'low electolyte water' into high electrolyte areas - so it stays there. Most osmosis is due to small voids in the laminate so it ends up as a 'pox' on the gel coat surface. THis then is a cosmetic problem and will never sink the boat particularly if the laminate is thick. Occasionally you will see a boat with poor layup and big voids that will cause a few very large blisters on the gel coat. I would avoid this type of problem as there 'may' be some structural issues.

I am not sure a boat that is not showing blisters yet  is suffering.

The cause for concern is when the gel coat is damaged due to impacts ie star crazing or cracks where water then has direct access to the laminate. Water then 'wicks' up the glass fibres and destroys the resin to glass interface which therefore weakens the laminate. This is where the problem of high water content can cause structural problems and it is not osmosis. If I was buying a grp boat, I would not be too bothered about osmotic blistering if it was over a large area of the boat. It is easy to repair and if it is a decent thickness, it will only be cosmetic. If however there were 2 or 3 sections with large blisters ie 3''+ across or clear problems of gel coat cracking/exposed laminate/damaged laminate then I would be very interested in water contents.

You seem to be building up osmosis to be the main problem to look for on grp hulls. It isnt. Poor gel coats, poor layup, poor cure, unrepaired damage etc are far worse problems leading to reduction in tensile and flex strength of the laminate and a reduced lifetime. In general though, grp lasts for years and a good hull is going to be fine 50 years later as most boats built in the 70s/80s/90s had hulls so over designed. Shame grp boats look so tatty when they get old.

Yes. Thus the first signs that a boat is suffering from osmosis is a high moisture content reading and not necessarily blistering. There would not be high moisture content if the process of osmosis was not occuring in the hull (given of course that there is no other damage in the area)

GRP does not have to look tatty as it ages. There are some excellent examples of 70's boats about that have been well maintained and the orginal gel coat is still in very good condition. Some people however decide for whatever reason not to look after their gel coat so well and leave them to get dull or subject them to shoddy paint jobs, much the same as some people choose not to polish the paint on their narrowboats and leave that to get tatty I suppose.

Link to comment
Share on other sites

9 hours ago, Phil Ambrose said:

GRP boats do not need to look tatty as they get older. They only need a good going over with polishing compound to bring them up like new. The problem is a lot of people can't be arsed to put in a bit of effort and compound their boat, or even worse they paint the poor thing.

Phil

You are right Phil unfortunately I will be painting mine it's bright Orange so it has to change 

Link to comment
Share on other sites

1 minute ago, peterboat said:

You are right Phil unfortunately I will be painting mine it's bright Orange so it has to change 

We were discussing this the other day and decided we would use vinyl instead of painting if we have to change the colour on our next purchase, which we most probably will!

Link to comment
Share on other sites

9 hours ago, Dr Bob said:

This is not correct. Osmosis causes blisters. The water flows into a void via osmotic pressure and keeps flowing in until a blister is formed. The water then doesnt move out to other parts of the laminate as the osmosis process drives 'low electolyte water' into high electrolyte areas - so it stays there. Most osmosis is due to small voids in the laminate so it ends up as a 'pox' on the gel coat surface. THis then is a cosmetic problem and will never sink the boat particularly if the laminate is thick. Occasionally you will see a boat with poor layup and big voids that will cause a few very large blisters on the gel coat. I would avoid this type of problem as there 'may' be some structural issues.

What you have not mentioned is that the pressure can cause the GRP to de-laminate, resulting in 'soft-spots' that feel like a trampoline when you walk on them.

This is a serious, and expensive fault to rectify requiring cutting out and re-fibre glassing the whole area and trying to repair the structural strength - ,I'd suggest a 'walk-away' issue when looking at buying. 

Link to comment
Share on other sites

53 minutes ago, Alan de Enfield said:

What you have not mentioned is that the pressure can cause the GRP to de-laminate, resulting in 'soft-spots' that feel like a trampoline when you walk on them.

This is a serious, and expensive fault to rectify requiring cutting out and re-fibre glassing the whole area and trying to repair the structural strength - ,I'd suggest a 'walk-away' issue when looking at buying. 

That was the big voids problem I was referring to giving large blisters, large enough so they are soft areas but still a blister. Thanks for clarifying.

Link to comment
Share on other sites

11 hours ago, Alan de Enfield said:

What you have not mentioned is that the pressure can cause the GRP to de-laminate, resulting in 'soft-spots' that feel like a trampoline when you walk on them.

This is a serious, and expensive fault to rectify requiring cutting out and re-fibre glassing the whole area and trying to repair the structural strength - ,I'd suggest a 'walk-away' issue when looking at buying. 

 

10 hours ago, Dr Bob said:

That was the big voids problem I was referring to giving large blisters, large enough so they are soft areas but still a blister. Thanks for clarifying.

luckily for me I can see all of the inside of the hull [less poo tank] and no soft areas exist, floor has no bounce layup is very thick. I will happily insulate the floor lay down the unerfloor heating and put down the new floor without concerns

Link to comment
Share on other sites

11 hours ago, peterboat said:

 

luckily for me I can see all of the inside of the hull [less poo tank] and no soft areas exist, floor has no bounce layup is very thick. I will happily insulate the floor lay down the unerfloor heating and put down the new floor without concerns

It tends to be the decks and roofs that first alert you to delamination rather then the hull.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.