Jump to content

Any idea what kind of paint this is?

ronnietucker
 Share

Featured Posts

springy Proficient

springy

Posted
Posted

IIRC the Gelcoat is a layer of the same plastic monomer & activator mix with the required pigment added which would normally be painted on the inside of a mould (after a good waxing) the fibreglass (or other reinforcing material) is then laid over this with more monomer / activator mix worked into the matting up to the desired thickness and allowed to cure. As such the gelcoat is not really a separate layer but an 'integral' part of the fibreglass structure, although if cut with a saw a transition from the pigmented gelcoat to the clearer colour of the standard unpigmented resin can be seen, I have seen gelcoat can be applied onto an existing surface (for repairs etc) but it would be the same monomer/activator/pigment mixture, getting a high gloss finish really needs a waxed mould. (All based on 20-30 year old knowledge so current materials may have changed)

 

springy

 

Link to comment
Share on other sites
Dr Bob Veteran II

Dr Bob

Posted
Posted (edited)
33 minutes ago, springy said:

IIRC the Gelcoat is a layer of the same plastic monomer & activator mix with the required pigment added which would normally be painted on the inside of a mould (after a good waxing) the fibreglass (or other reinforcing material) is then laid over this with more monomer / activator mix worked into the matting up to the desired thickness and allowed to cure. As such the gelcoat is not really a separate layer but an 'integral' part of the fibreglass structure, although if cut with a saw a transition from the pigmented gelcoat to the clearer colour of the standard unpigmented resin can be seen, I have seen gelcoat can be applied onto an existing surface (for repairs etc) but it would be the same monomer/activator/pigment mixture, getting a high gloss finish really needs a waxed mould. (All based on 20-30 year old knowledge so current materials may have changed)

 

springy

 

Springy is right in his thoughts on gel coat, but there is one more thing that causes a problem.

You apply the gel coat to the inside of the mould and when cured sufficiently, you apply the laminate. Now, for polyester grp...which is what you have..... that laminate, once laid up, cures. Normally polyester resin when cured in air...ie the surface of the laminate... will remain sticky for 24 to 48 hrs although the resin beneath cures hard. This is because air inhibits the cure. The resin manufactures get round this by dissolving wax in the laminating resin which rises to the surface while working the resin with a roller and the wax effectively 'seals' the surface from the air, so the laminate is no longer tacky. The wax also has the effect of reducing styrene emissions which is good.

What has this got to do with gel coat?

Well, if you try and paint gel coat over the top of an existing gel coat, the outer surface will remain sticky for quite a while as it is in contact with air and therefore unsuitable for a 'final' coat. If you are repairing gel coat, the trick to it is to get a sheet of Melanex film, apply a coat of gel coat to it at the right thickness then stick it on to the grp surface like a plaster (with the melanex outwards). Let the gel coat cure and then peel off the melanex.....and you have a nice shiny surface apart from the join! No sticky gel coat.

So Rusty's comment of 'No' it doesnt work is pretty much right. Alan's comment of Yes but it is expensive is likely to be also right but I have no experience of this. I developed Gel Coats in the late 70's for the UK's second largest manufacturer so know first hand the issues. It is possible to dissolve wax into the gel coat which as per the laminating resin could inhibit the air reaction but that wax could have issues with the bubble release, the flow and pigment floculation (technical terms) so you would have to know what you are doing. Getting a good finish is then the issue which is why Alan found it expensive. There may be other ways to stop the air reaction.

Painting gel coat is not easy. Tony is right. Try to polish up the existing gel coat but why was it painted over in the first place? For a coating, you need a very flexible coating but what the norm is today, I dont know. Look on the internet. Gel coats last 40 years if looked after. Paint is not likely to make 10 years before it looks naff.

 

Edit to add. Tune in next week when you will hear Dr Bob say " My duck has volunteered to do it for £35, 676.39p inclusive"

Edited by Dr Bob
  • Greenie 1
Link to comment
Share on other sites
rusty69 Veteran II

rusty69

Posted
Posted
5 minutes ago, Dr Bob said:

Well, if you try and paint gel coat over the top of an existing gel coat, the outer surface will remain sticky for quite a while as it is in contact with air and therefore unsuitable for a 'final' coat.

V.Interesting. I always wondered why we put a bit of clingfilm over gelocoat repairs. Now I know!

Link to comment
Share on other sites
Dr Bob Veteran II

Dr Bob

Posted
Posted
1 minute ago, rusty69 said:

V.Interesting. I always wondered why we put a bit of clingfilm over gelocoat repairs. Now I know!

Yep, full of useless information. Melanex is much better than cling flim as it is more 'rigid' and gives a more glossy surface. Worth getting hold of some if you are doing a biggish repair.

Link to comment
Share on other sites
rusty69 Veteran II

rusty69

Posted
Posted
7 minutes ago, Dr Bob said:

Tony is right. Try to polish up the existing gel coat but why was it painted over in the first place?

Cos someone didn't try cleaning it.Its certainly worth a try. The gelcoat on our boat cleaned up quite well with some elbow grease on what looked like a definite re-paint job. Sometimes people just paint over to change the colour, although clearly not in this case.

  • Happy 1
Link to comment
Share on other sites
rusty69 Veteran II

rusty69

Posted
Posted
7 minutes ago, Dr Bob said:

Yep, full of useless information. Melanex is much better than cling flim as it is more 'rigid' and gives a more glossy surface. Worth getting hold of some if you are doing a biggish repair.

I used some gelcoat last month to finish a repair to my sailing dinghy ( A buoy jumped out at me and put a hole in it). What I thought would be the hardest part,adding pigment to match the existing gelcoat looked too much like hard work, so I didn't bother. Luckily it turned out a near perfik match!

Link to comment
Share on other sites
  • 2 weeks later...
LadyG Veteran II

LadyGDonate to Canal World

Posted
Posted (edited)

Have you been following SAIL LIFE on youtube 

 

Briefly he has met a lot of challenges with Athena, including tackling  the hull laminate, decking, gelcoat, and a lot of other things. He has done a lot of research and tried lots of techniques. At the moment he is doing a barrier coat below the waterline.

Edited by LadyG
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
 Share
Go to topic listing

  • 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.