Build of a Bonito 50 Motorcruiser

jfm said:
Sprayed gelcoat creates a skin that is about 2mm thick and because of the thickness/creaminess of gelcoat it smooths out any surface imperfections better than paint. Paint is much thinner. Gelcoat can also be rubbed/sanded/polished very easily after the final coat - paint can sometimes too of course. When you look at gelcoat/plywood components, you think the thing is made of GRP. It is also much easier to repair scratches and bumps in gelcoat than in paint. It needs a stable base, ie best quality marine ply. As I say, it is widely used for deck boxes/furniture on custom GRP superyachts like Mangusta, Leopard, et al.

They use a gelcoat formulated for spraying, with wax to enable it to dry when exposed to air
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many thanks, thats very interesting info,
this is probably wat the yard in Fiumicino used on BA, 1,5 year ago, for painting the new steps and the gunwale,
the finish was amasingly smooth.
When they took of some masking tape, I noticed the paint on the tape was about 2mm thick, and much more flexible then you would expect from normal paint.

do you know;
to achieve 2mm, how many layers of gelcoat need be sprayed ?
or is this done just in one go ?
 
BartW said:
do you know;
to achieve 2mm, how many layers of gelcoat need be sprayed ?
or is this done just in one go ?
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From memory (visiting yards in Viareggio, but some years ago) they spray something like 3 coats. You cannot get the 2mm in one spray pass and there is no need to try. I recall that they used normal gelcoat for the initial spray coats, because it dries sticky on the surface, then used wax-added gelcoat for the final coat so it dries not-sticky, ready for sanding/buffing/polishing

I guess they used a primer on the wood to stop the gelcoat soaking in, but I don't know about that.
 
jfm said:
I like what Danny is doing here. Marine ply, with radii on all corners, then sprayed in gelcoat, is a long-established quality method of making one-off deck box/furniture items. It is widely used in superyacht ...
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agree, superstructure on BA is made like that, many visitors think its GRP (has been totally refurbished / repainted in 2009)
I was asking because I'm considering all possible options for the next upgrade on BA, a FB hardtop, inspired by Monte Carlo Yachts (they're using carbon fibre)
more questions / info about that later in my rebuild thread
 
BartW said:
agree, superstructure on BA is made like that, many visitors think its GRP (has been totally refurbished / repainted in 2009)
I was asking because I'm considering all possible options for the next upgrade on BA, a FB hardtop, inspired by Monte Carlo Yachts (they're using carbon fibre)
more questions / info about that later in my rebuild thread
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the biggest problem with a self build project is getting a decent finish. This process opens up a whole new world, build in plywood which is easy to cut and glue......finish with gelcoat.

sounds like a really good idea.
 
jfm said:
From memory (visiting yards in Viareggio, but some years ago) they spray something like 3 coats. You cannot get the 2mm in one spray pass and there is no need to try. I recall that they used normal gelcoat for the initial spray coats, because it dries sticky on the surface, then used wax-added gelcoat for the final coat so it dries not-sticky, ready for sanding/buffing/polishing

I guess they used a primer on the wood to stop the gelcoat soaking in, but I don't know about that.
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jfm....do they lay on a bonded chopped strand mat layer all over prior to spraying, interesting if not as I would have thought that unless the construction was extremely rigid they may become sucsceptible to cracking of the gelcoat at stressed areas?
As per the joints in plasterboards being taped prior to a skim sort of thing!
 
jfm said:
Danny if it would save you much work (and weight?) to abandon the plywood and mould the dash in GRP here are the dimensions. The mould is in UK (postcode PE8 4HN) so not convenient I guess, but you can have it for free if you want it. I also have CAD files for the aluminium panels on the face of the dash. The Perspex is easy - just a rectangle

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Here is the finished dash. The screens are Garmin 7015
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Hi,
It's a great offer, thanks. But I have checked the dimensions and your dash is more than 20 cm larger then mine. Also the dept will be a problem. Again, thanks for the offer.
 
D-Dream said:
I think it's very usefull for finishing walls or sealing, but for constructing a bench... I have my doubts.
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i'll let you know on tuesday!!!

looking at the stiffness guide it seems to weigh about 70% less for the same rigidity as aluminium.
the alloy is only 110, so not marine grade, but it is painted and sealed in a plastic membrane, so should be reasonably corrosion proof.
i was considering using 1.5mm ally sheet at 12 kg, this material only weighs 10kg and is nearly twice as strong.
 
I'd agree with D-Dream RB,

I've bought 3 sheets of the thing in a light silvery alloy colour and I'll use it to line the aft deck ceiling (without any underlay as it wont be readily squeezable/bumpable...) and to line the hull sides on the cabins (but in that case glued on a 6mm ply for rigidity)
I'd probably use it for f/b furniture but glueing it on top of a structural frame (probably wooden battens and thin ply-the 6mm is excellent for that!)

I'd really like to get hold of this 2mm spray on gelcoat but it's only available in a limited range of colours (and not even sure I can get it down here...)

cheers

V.

PS. I think I've not posted in this thread before, well done D-Dream, will be looking closely at this built thread for sure!
 
vas said:
I'd agree with D-Dream RB,

I've bought 3 sheets of the thing in a light silvery alloy colour and I'll use it to line the aft deck ceiling (without any underlay as it wont be readily squeezable/bumpable...) and to line the hull sides on the cabins (but in that case glued on a 6mm ply for rigidity)
I'd probably use it for f/b furniture but glueing it on top of a structural frame (probably wooden battens and thin ply-the 6mm is excellent for that!)

I'd really like to get hold of this 2mm spray on gelcoat but it's only available in a limited range of colours (and not even sure I can get it down here...)

cheers

V.

PS. I think I've not posted in this thread before, well done D-Dream, will be looking closely at this built thread for sure!
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The reason i choose the aluminium composite panel is because i'm very weigh limited on the total weight for the cat hardtop, and it comes ready painted and finished. 17' by 8' top including frame will be less than 100kg.
A 6-7mm plywood would weigh the same, but would need to be finished in epoxy and matt, which would nearly double the weight.
I tried standing on a 9mm plywood sheet in B&Q supported at approx 3' centres, and i heard a nasty cracking noise.
According to a forumite who also has a aluminium hardtop, a 1.5mm ally sheet at 1mtr centers will support a 80kg person.

the aalco panels has equivalent stiffness to a 2.5mm sheet of ally., hopefully.......
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Hi,
The big bench is also finished and I started with the filling of the various parts. I use for the filling 2-component filler. This is a very time-consuming job: filling, sanding, filling, etc... but it's very important if you want to have a nice result afterwards.

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Robg71 said:
keep up the excellent work. I am watching progress and getting lots of ideas :)

ps, are you near to the dutch border/amsterdam schiphol. would love to come and have a look.
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Hi Rob
Thanks. I m located in Belgium. It s about 200 km from Schiphol airport. But you are always welcome. Juts let me know when.
 
Hi all,
After a lot of sanding and filling with 2-C filler, I started with the painting of the different parts. The cockpit and 1 support are already with painted with 1 topcoat. The other parts have just got a basic layer.

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