Concerto
Well-Known Member
Most of the top boat builders (not mass market) mould with white gel coat and then if the owner wants it a different colour, the hull is sprayed with Awlgrip to whatever colour they want.
1974 Hull Materials
- Thread starter Sea badger
- Start date
Praxinoscope
Well-Known Member
I haven't studied the latest GRP boat building techniques, but I am not sure that your concept of spraying gel coat onto the Hull after removal from the mould is used, it is the quality of the mould and the careful application of the release compound ( may be wax or silicone) to the mould before the gel coat is sprayed on to the release agent in the mould thats gives the shiny surface, when the Contessa was in production along with the other 70/80's boats, the gel coat was roller painted on to the mould before lay-up, which is why gel coats from this period are thicker but often more variable in thickness than boats produced today.
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Concerto
Well-Known Member
Boats in the 70/80's definitely had the gel coat usually brushed on. If the person applying it failed to brush the mix our correctly, small air bubbles could be trapped in the gel coat. Most builders in the 90's started spraying 3 coats of the gel coat in the mould as it was quicker and used less gel coat than brushing. A brushed gel coat is generally 1 to 2 mm thick, except for Westerly who applied a double coat of brushed gel coat and can 2 to 3mm thick. Modern sprayed gel coat is 0.5 to 0.75mm. This information was told to me by the local glassfinre repair man who does a brilliant job, never used him but watched complete several jobs.
PaulRainbow
Well-Known Member
Really, can you post some links to the manufacturers that are doing this ?
It's a very long winded and time/money consuming way to make a GRP product. It's normal to spray the mould with gelcoat, then lay the glass up before the gelcoat is fully cured, this requires no additional work or cost when the product is removed from the mould.
anoccasionalyachtsman
Well-Known Member
I'm hoping he means one-offs from a male mould.
lustyd
Well-Known Member
I didn't say any of that ?
A good example is Princess, who have most of their boats sanded and sprayed after production. The moulds are large and not even remotely flat, so straight from the mould they look very cheaply made. Look at a new Sunseeker if you want to see examples of this, I believe they don't do this stuff. You need to look along the hull to see what I'm talking about. While shiny, the finish looks pretty poor out of the mould. The boats are then sanded back to flat using long ply boards to produce a good "flat" surface which is then sprayed any colour the owner wishes. As Concerto says, Awlgrip is used to paint them, but it's not just to change colour as many get sprayed white
Concerto
Well-Known Member
Sounds more like poor quality moulds. If they spent the same effort on the hull shape former for the mould as they do no each hull, every hull would come out perfect.
JumbleDuck
Well-Known Member
Even Awlgrip does not, I am told, last very long - but Princess are in a market where few owners of new boats seem to keep them for more than a year or two, so perhaps it doesn't matter very much.
lustyd
Well-Known Member
Not sure where you heard that, it's got an exceptionally long warranty when applied by certified people and I'm not aware of any having had finish issues when professionally applied. It's effectively as good as gelcoat from what I've seen.
lustyd
Well-Known Member
That's true at the smaller end of the scale, but try making a 60 foot one and it gets harder. Individual parts will be flat, but producing a good line along the whole boat and more importantly keeping it stiff enough during moulding through varying temperature ranges is extremely difficult and more importantly expensive. Different companies take different approaches, some "fix it in post" and others pretend it's a good finish. Most people don't even notice how wonky those big boats are as they're too busy seeing the bling, after all the hull will be shiny regardless.
DownWest
Well-Known Member
Hearing some odd stuff on this thread..
Any boat builder trying to keep costs in line would get the best mould he could afford. Then spray the gelcoat on (it is designed not to go off quickly) then lay the glass and polyester resin layers up to creat the hull. When I joined a small outfit to get some production experience, the moulds were tidied up about every ten hulls. In between, small probs were faired with putty.
The idea of laying up a hull and then applying the gel coat is laughable. We did that on a one off sports racer car. No way would you do it for production.
Any boat builder trying to keep costs in line would get the best mould he could afford. Then spray the gelcoat on (it is designed not to go off quickly) then lay the glass and polyester resin layers up to creat the hull. When I joined a small outfit to get some production experience, the moulds were tidied up about every ten hulls. In between, small probs were faired with putty.
The idea of laying up a hull and then applying the gel coat is laughable. We did that on a one off sports racer car. No way would you do it for production.
matt1
Well-Known Member
Yup! Never heard or seen that in any series production, I mean why would you?
Concerto
Well-Known Member
If a hull can be made distortion free by sanding and painting, they might was well just use a crude male mould. If they are using a female mould, then it still comes back to a poor mould former finishing and then inadequate stiffening of the mould, or possibly the hull thickness is too thin to hold its shape.
DownWest
Well-Known Member
That is interesting.. Back when I was in it, on much smaller boats, lots of effort went into fairing the plug.
On BIG boats, shurley the shiney finish shows up any wavey hull lines?
lustyd
Well-Known Member
Yes, that's the reason they sand and fair them
Because people paying £1M+ for a very large luxury boat expect a level of finish that a mould cannot provide. Same reason BMW refinish the paint by hand on high end cars after spraying!
DownWest
Well-Known Member
So, what you are saying is that the small numbers of big hulls coming out of moulds, does not justify fairing the plug and mould enough to a high standard? More effective to do it after the hull is out of the mould?
Back when we did a bit of stuff for Lotus, they quickly realised that self coloured shells were not going to cut it, so spray painted them. OK for 7s, not for Elans.
lustyd
Well-Known Member
No, I'm saying that over a certain size it's uneconomical to create and use a mould to that standard, yet relatively cheap to get a team of people in to sort it after production. My car comment was that a spray finish is not good enough on high end goods, so BMW flatten and polish them to get the kind of finish a high end customer wants and expects. A standard spray finish looks shocking by comparison.
DownWest
Well-Known Member
Think we are on the same page.
Bit surprised about BMW. Are their finishes that much better to justify the expensive labor?
Bit surprised about BMW. Are their finishes that much better to justify the expensive labor?
lustyd
Well-Known Member
Yes, the ones that get done have a very flat mirror like finish, even an untrained eye can easily spot the difference. Realistically it's a one person/one day job so on a £50k car not a big deal. The boats are a 4 person one week type of job so on a million pound boat also not that big a deal. Especially true when at a boat show and you can stand someone on the pontoon and directly compare the "build quality" where one boat looks smooth and the other looks like a circus mirror.
