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[chris holley]

I am thinking off designing a fast electric as there is noting i can find that will suit what i have in my head , i am looking at a boat which is ideal for flat calm an choppy conditions .

So i am looking at 32" x 10", by a hight of 5.5" with a deep vee an stepped. i have found a boat by hydro marine the Streamer crossed with the X ray





so i have a piece off sheet wood cut to the L x W of the boat, an bought some polystyrene just to work on the design.

know will the poly be ok to make a mould or plug an if so? is it to work with, what prep do i need to make with it before i fibreglass?

i normal just buy a hull, but want to try an experiment.

any help an advice would be ideal am much appreciated thanks chris

[martno1fan]

Poly resin will eat the polystyrene you will either need to use epoxy which is expensive or use a special type of foam thats expensive.You could buy some insulation foam sheet and get the shape you want then cover it with filler and sand smooth and paint maybe but its risky if the poly resin gets to the foam its ruined.You can buy the propper foam sheet here,its not cheap but this is what you really need.You have a big job on your hands trust me,plugs need to be flawless or any moulds and then parts will magnify any flaws,good luck.

http://www.ecfibreglasssupplies.co.uk/category/tabid/60/entityname/category/categoryid/458/sename/pu-foam-board/default.aspx

[chris holley]

thanks for the headsup- will look at this site an give them a call.

[martno1fan]

No worries mate not trying to put you off but having done it i know what works involved  .If you call them ask for Marting hes a top lad and very helpfull.
Mart

[rapidrabbit]

Hi Chris,

I am in the process of making a large plug to be moulded and I am using the following materials - Blue High Density foam board, plywood formers and body filler. Once the body filler is on the blue foam you should be able to cover in either epoxy resin or poly resin. Poly resin with eat the blue foam though so it needs a barrier of body filler to protect it. I don't know about Epoxy on blue foam though as I have not tried it.

Good luck with your project,

Nigel

[Subculture]

If using car body filler on blue (polystyrene) foam, this will also 'eat' the foam, as it's polyester resin mixed with talc.

You can guard against this by painting the foam with an oil based paint, epoxy resin or brush on some PVA glue.

The other alternative is to use polyurethane foam for your plug (the yellow stuff) which doesn't react with epoxy or polyester resins.

I use this, skin it with a two or three layers of 300 gram CSM, glass tissue and then topcoat or polyester filler to get the final finish.

[Greggy1964]

You can make a polystyrene plug but you have to prevent the fibreglass resin from getting to it.

Carve the hull shape you want but then clad it entirely (deck surface included) in something that is impervious to the resin.

That Aluminium foil gaffa tape would work maybe, its thin, would mold to the hull shape, stick to the polystyrene and is impervious to resin

Or you could clad it in newspaper soaked in white wood glue and then paint the thing with melted candle wax.

A very sharp cabinet scraper would smooth things out, or you could just paint it with release wax.

You could use this hull as your plug to make a mold and then turn out as many hulls as you like

You 're only limited by your imagination

[DavieTait]

Bill Wood has done a plug/mould making series on Trawlerphotos that should help you

http://www.trawlerphotos.co.uk/gallery/showphoto.php?photo=99622

Start at that photo and go to the right from there they're all in sequence

Davie

[Tugwilson]

that's got to be the most comprihensive demonstration of mold making i have seen for a long time.
Thanks for giving us the link Davie

Tugwilson

[DavieTait]

We're lucky that Bill has taken the time to document how he builds his plugs and moulds Tugwilson the models he builds are exceptionally high standard

[Mr_Fid]

I dont know if this is of any use to you? I put this discription on another forum but have cut and pasted it below. Plug was made from scraps of balsa wood and hardboard, and then car filler was used followed by hi build primer.

Today I have started on the top. I have decided to (rightly or wrongly?) to make the top out of fiberglass, so I am in the

process of making the top on the model, which I will then take a mold off, and then all being well will be able to make a

molding? Or copy.



Well as explained i am going to make the top out of fibre glass. so i have now finished making the top out of wood and

filler, and spent the afternoon spraying loads of high build primer on to it. tomorrow i should be able to finish of the top

so that i can then take a mold off it.





ok this is the construction of my fiber glass top. this is a very long winded
process just to make a top but there you go

Picture 1, shows the yellow plug, mounted on a piece of white faced hard
board, and also the part line has been stuck in place (and screwed at both ends)


Picture 2, the side has now been gel coated, two coats were applied and left
to go off. the resin was brushed on and a finely chopped glass was placed
into the sharp corners of the plug.

Picture 3, then the first of two layers of CSM was applied, hear you can see
it is being pushed into place using a brush. I would like to point out that it
is not me in the picture I was being show how to do it by a very skilled laminator

Picture 4, once both layers of CSM have been put on then the air is rolled
out.

Picture 5, here is the completed first layers of CSM, this was left to go
off, and then another layer was added, followed by a layer of reinforcing mat,
finished off by another layer of CSM.

Picture 6 now you can see the other side, the parting piece of hard board has
been removed, and the plug given a good coat of wax. the same process is the
carried out as with the first side.

Picture 7, and here is the fully laid up mold, the white areas are the re-enforcing
mat (coremat)

Picture 8, here are the two half of the mold, firstly they were rubber down
with 800 grit wet/dry followed by 1000 and 1200, then the mold was polished.>

Picture 9, here is the two halves of the mold bolted together ready to
receive the gel coat.

Picture 10, and here is the final picture of the day, I have just left the fiber
glass shop and tomorrow I will lay up the CSM and with any luck by lunch time I
should have a top.

well i layed up the two layers of CSM and then waited untill it had gone hard, (i always worry that it isnt going to come

out)

then we split the mold and free the edges, the whole lot came out very easly!

i am very happy with this part! i know its been a long process just to make a top for a boat, but i wanted to do it and i

have learnt so much from being in the fiber glass shop for 5 days.

[martno1fan]

Looks very nice,lots of work goes into making plugs and moulds its a pity more dont realise this  .
 Just a heads up someone stated that you can seal blue foam with epoxy and then use polyseter resin and glass to make a mould from the plug.This is totally wrong as polyseter resin will not cure over epoxy,now the other way round is fine as epoxy will cure over poly resin.If you seal the blue foam with epoxy then you must make the parts using epoxy,the best way to make a plug when using poly resin is to buy propper poly foam board as this wont melt.
Mart

[Subculture]

Okay that's interesting. I've not had any problems mixing the two in the past, although it's been limited to using polyester fillers with epoxy hulls etc.

[martno1fan]

Try it,get some epoxy mix it up and let it set then get some poly resin mix it and see what happens when you put that on top.It wont go off it remains tacky in fact it goes even tackier lol.