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Old Today, 10:37 AM
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Vienna/Austria
Joined Jan 2009
1,089 Posts
Mini-HowTo
Building one-off hull shells from a male plug:

I usually build/built my plugs of solid styrodur foam,
shape/sand them to probably 0.5mm preciseness throughout,
then glass them over with 2 x 160 gr. glass twill,
then 2 x 80 gr. glass. -
Or 3 x 160 gr. glass twill and one layer of peel ply.
Let it cure for 24 hours.
Then they get sanded/faired till I´m satisfied.
Then PVA release film is applied.

Next step is laminating:
1) One layer of peel ply. (Yes, INSIDE! )
2) 2 x 160 gr. carbon. Twill or linen, but I prefer linen for multihull shells.
3) one more layer of peel ply outside.
This way the carbon layers get compressed, smoothened out and any excess resin sucked up. If the peel ply looks shiny when done, you´ve used too much resin...
Or you can use one layer of 80 gr. glass instead of the peel ply - same prucedure.
Let it cure at least for 24 hours.

Next step:
Cut off any overhanging (cured) cloth fore and aft of the hull.
Now remove the peel ply - or, if you used the 80gr. glass, just start sanding.
I allways use a sanding block (fir) of at least 10" x 2" x 1".
As time goes by that block feels like an extension of your own hand...
I start with grain 40, usually starting from the main cross section towards the ends - but don´t sand too much with it!
Carefull at the ends, where the radiuses get smaller/sharper!

Sanding direction normally is mostly cross diagonal -
much more than fore-aft sanding.
About 75-80% of the surface should be smooth now!
100 % is definitely too much.

Please use rubber gloves, dust mask AND vacuum cleaner all the time!
Also very loose, old clothes - like jogging dress/jogging trousers + old T-shirt.
Thight clothes are NOT good! You will soon find out why!
And stroking the hull in between isn´t bad either -
as it imcreases your feeling of/for the hull shape.

Then I redo the whole process with grain 80.
When completed, the process is redone with grain 120.

Then it´s time for a shower.
Not YOU - I mean the hull first!
The water removes the finest remaining dust particles and
dissolves the PVA release film.
Use one (or several) plastic squeege(s) to lift the corners of the carbon shell off of the male plug. Let the (warm) water run into the gap.
Soon you´ll hear that satisfying soft plop when the shell comes free.
Remove any remaining PVA from the plug, put plug and shell outside of the shower - and now it´s YOUR time to take a shower.

For one 62" shell the whole procedure shouldn´t take longer than 1 to 2 hours,
depending on your own speed and confidence.
But sanding too fast and with too little feeling will ruin the shell and you´ll have to redo it from the beginning...

If you take a closer look at my ´60" Daydreamer´-trimaran and it´s surfaces - you normally wouldn´t believe it wasn´t made from female molds - would you?
No, it was all done from male plugs.

And when plug + shell is dry again, you can apply PVA release film to the plug again immediately -
and you can also ripp off the peel ply from the inside of the shell now!
Ready for the next building steps - and the lightest buildmethod besides the use of autoclaves!
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