Filler, repairs and undercoats for chips, scratches and blisters

Robert Wilson

Robert Wilson

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What to use?
I'm nearly finished removing the old paint from my GRP boat(1980s) . During the process, using a hot air gun and Bahco scrapper, I have uncovered various bits of damage, old filled areas and I've made some gouges into what I assume is the gelcoat.

Before undercoating, what is the correct filler to use to repair the damage?

I'm totally new to GRP work, so please don't get too technical !!

Thanks in anticipation

Robert
 
Easiest way is to use a 2 part epoxy fairing filler such as International Watertite which you can get from any chandlers. Alternative which is arguably a bit cheaper if you are doing a lot is to make your own by mixing epoxy and adding a fairing filler. However only really makes sense if you are using epoxy for other jobs.

Good information on preparation on the International website and using epoxy on the Wessex Resins site - or you could buy the PBO book on refurbishing older boats.
 
Ive always used Plastic Padding gelcoaat filler. Two part stuff filler and hardener. Very easy to mix and use but don't overdo the 'leaving it proud' instruction because it's quite hard to sand down. It can be tinted to match surrounding gelcoat but thats a skill Idon't possess.
 
coopec said:
I would use a polyester or epoxy mixed with a filler like talc because I would probably be doing a fairly big area.

I don't know how much you have to do but maybe some "body filler" they use on motor cars might do the job?

http://www.mig-welding.co.uk/body-filler.htm
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Some car body fillers (or the talc in them) certainly absorb water unless well sealed: I've also had them slightly "bleed" the pinkish colour from the (usually red) hardener through white paint after a while. Refinishing a hull is such a huge and labour-intensive job that it makes sense to use reasonably decent materials.
 
ghostlymoron said:
Ive always used Plastic Padding gelcoaat filler. Two part stuff filler and hardener. Very easy to mix and use but don't overdo the 'leaving it proud' instruction because it's quite hard to sand down. It can be tinted to match surrounding gelcoat but thats a skill Idon't possess.
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I've just re-read your enquiry. If you are over painting, just use waterproof filler not gelcoat. http://www.seamarknunn.com/acatalog...5g-6891.html?gclid=CJf78uSQ9cwCFa0V0wodSLAO8w
 
Nicholas123 said:
Ronseal "High Performance Wood Filler." (other propriety brands available) Cracking stuff 17 quid a kg :encouragement:

(You can add colour pigment available from ebay then no need to paint it).Job done :)
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I've used it ashore for rotten painted window frames, and for that it's pretty good. Not sure I'd want to use it on a boat hull - the fact that they claim you can stain it must mean that the filler material is slightly absorbent. As I said before, to get an old boat hull up to a good finish is so hugely labour-intensive that you may as well use decent materials.
 
jwilson said:
I've used it ashore for rotten painted window frames, and for that it's pretty good. Not sure I'd want to use it on a boat hull - the fact that they claim you can stain it must mean that the filler material is slightly absorbent. As I said before, to get an old boat hull up to a good finish is so hugely labour-intensive that you may as well use decent materials.
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I hav'nt seen the 'stain it' remark.I use proper pigment paste & used it on my previous boat to fill osmosis blisters below the waterline that were about 3/8" deep.Finishing them by rubbing over the surface with ordinary Halfords fibreglass resin on the tip of my finger.Last time I looked they were still going strong after twelve years & none had broken down.
If you find it labour intensive or an ordeal you are doing something wrong.It's a a piece of cake with a LIDL multi-grinder & very satisfying. :encouragement:

OH I forgot,you may need to go over the surface with a broken hacksaw blade in order to get a smooth finish :D
 
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jwilson said:
I've used it ashore for rotten painted window frames, and for that it's pretty good. Not sure I'd want to use it on a boat hull - the fact that they claim you can stain it must mean that the filler material is slightly absorbent. As I said before, to get an old boat hull up to a good finish is so hugely labour-intensive that you may as well use decent materials.
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Agree. A tub of Watertite is £20, or Plastic Padding a bit cheaper at £17. Made for the job and applied properly gives a fine finish for painting.
 
Hi Robert,
Don't bother! Now's your chance to become famous and experiment. Get a golf ball and look at it closely. It's full of hollows and this is so that it it flies through the air straighter and faster. Now if you get a sander and make a hollow at all your dents scratches and gouges you'll end up with a golf ball hull. Balance the two sides of the hull a bit and Khamsin will fly through the water. You'll be able to go round the UK in half the time next time!
When you become a millionaire remember me. :D
Hope it's all going as planned
Mike
 
Tranona said:
Agree. A tub of Watertite is £20, or Plastic Padding a bit cheaper at £17. Made for the job and applied properly gives a fine finish for painting.
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Still twice the cost of what I'm paying & I'm quite sure you've got no evidence that it does a better job.

Why would you want to paint it & add to all the endless maintenance?The idea of fibreglass is supposed to be that it is maintenance free.
 
Robert Wilson said:
What to use?
I'm nearly finished removing the old paint from my GRP boat(1980s) . During the process, using a hot air gun and Bahco scrapper, I have uncovered various bits of damage, old filled areas and I've made some gouges into what I assume is the gelcoat.
Clean out the holes and fill proud with plastic padding, get it from Dingbro Inverness about a third of chandler price. Flat sand the whole hull with 320 grit then on painting day tack cloth the hull and paint with your chosen undercoat! Next day assuming you have good surface/weather ! gloss and walk away.

John


Before undercoating, what is the correct filler to use to repair the damage?

I'm totally new to GRP work, so please don't get too technical !!

Thanks in anticipation

Robert
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Too late Vegable.
Scientists have discovered the shark's scales cause tiny whirlpools which enable them to swim so fast.
 
Nicholas123 said:
Still twice the cost of what I'm paying & I'm quite sure you've got no evidence that it does a better job.

Why would you want to paint it & add to all the endless maintenance?The idea of fibreglass is supposed to be that it is maintenance free.
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You are making the mistake of saying what you did, rather than reading the OPs requirements. He is going to paint his topsides (irrelevant whether you agree with that or not) so he needs to correct fairing filler for the job. There is a huge amount of work (as he will discover) in preparing a hull for painting, if he wants a good finish. The two products suggested are specifically designed for that purpose. They are epoxy based, will adhere properly, will not fall out and crucially can be sanded to a fine finish for painting. That is what the professionals use - and the cost in relation to the overall cost (never mind the effort) of painting a 30' boat is miniscule.
 
Vegable said:
Hi Robert,
Don't bother! Now's your chance to become famous and experiment. Get a golf ball and look at it closely. It's full of hollows and this is so that it it flies through the air straighter and faster. Now if you get a sander and make a hollow at all your dents scratches and gouges you'll end up with a golf ball hull. Balance the two sides of the hull a bit and Khamsin will fly through the water. You'll be able to go round the UK in half the time next time!
When you become a millionaire remember me. :D
Hope it's all going as planned
Mike
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Och! I nearly fell for that one!
 
Thank you one and all.
Topsides were so badly scratched and bodged (from previous owners' whoopsies) that I decided to start from scratch and would need to paint again.
I wasn't sure whether some special compound was needed for repairs/filling. As noted by you above, I'm painting the hull when all is repaired and sanded. And yes, it is certainly a labour-some task.
Just removing the old paint with the hot-air gun and Bahco took 30 hours at least. Sanding with an orbital thingy has taken nearly five hours and carefully removing the paint from the coach line a further four hours.
Unfortunately, using the hot-air gun caused some damage; it seemed to melt and/or blister the gel goat. Not extensively, but some small patches. I wonder if the gel-coat has been damage by impact and hence weakened the surface layer making it vulnerable to heat?

I'm just about ready to start filling the damaged bits (not all my doing, I hasten to add :rolleyes:) so I wanted to make sure I would be using compatible and appropriate "stuff".

One odd problem I have come across is there is a "build-up" of some sort of compound from below the waterline to the top of the boot-topping - mainly around the stern area. Once it's been sanded off the gel-coat seems the same as the top-sides.
Any suggestions/info/thoughts on this?

When all is ready for painting I shall do the undercoat(s) and sanding myself, but I'm getting a professional to do the finish-coat. I hate painting and am useless at getting a good/perfect finish.

Thanks for all the info, as usual.

Enjoy your summer on the water. I'm looking forward to next season when Khamsin will be re-launched - looking superb in her new blue finery. :)
 
Tranona said:
You are making the mistake of saying what you did, rather than reading the OPs requirements. He is going to paint his topsides (irrelevant whether you agree with that or not) so he needs to correct fairing filler for the job. There is a huge amount of work (as he will discover) in preparing a hull for painting, if he wants a good finish. The two products suggested are specifically designed for that purpose. They are epoxy based, will adhere properly, will not fall out and crucially can be sanded to a fine finish for painting. That is what the professionals use - and the cost in relation to the overall cost (never mind the effort) of painting a 30' boat is miniscule.
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If you read what I posted you would see that none of mine 'fell out' & it's at least half the cost of what you suggest.It can be painted perfectly so why pay over the odds?
The fact is doing up old boats is a juggling act you can pay an arm & a leg trying to make a silk purse out of a sows ear but if your just going to throw your money around you might just as well buy a newer boat in the first place :cool:
 
Nicholas123 said:
If you read what I posted you would see that none of mine 'fell out' & it's at least half the cost of what you suggest.It can be painted perfectly so why pay over the odds?
The fact is doing up old boats is a juggling act you can pay an arm & a leg trying to make a silk purse out of a sows ear but if your just going to throw your money around you might just as well buy a newer boat in the first place :cool:
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Some logic in that, but firstly I can't afford a new/newer boat, secondly (most importantly) I love Khamsin and want to have her looking "good" and thirdly I enjoy DIY and learning more about boat maintenance.
She'll never be a "silk purse" but I'm proud of her and she suits my sailing, so I'll do the best my limited "purse" allows.

But thanks for your comments
 
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