fibreglass query

[CubanPete]

I'm building a model boat (international one metre) i've laminated the keel and shaped it from mahogany and spruce. I now want the sheath it in fibreglass.

In the interests of minimising the amount of sanding I want to wrap it in a barrier so I can compress it while it is curing.

What is the best thing to use as a barrier? Can I use a polythene bag...?

[dr_gn]

CubanPete said:

I'm building a model boat (international one metre) i've laminated the keel and shaped it from mahogany and spruce. I now want the sheath it in fibreglass.

In the interests of minimising the amount of sanding I want to wrap it in a barrier so I can compress it while it is curing.

What is the best thing to use as a barrier? Can I use a polythene bag...?

I'd have thought a bag would give more problems that it solves used like that. I've never built a model boat, but it's more usual on aircraft to use a vacuum bag on female moulds. On gliders I've used lightwight glass cloth soaked with resin - it conforms to contours really well and just needs fairly minimal flatting to give a rally good finish.

[CubanPete]

The fibreglass tissue I have is very fine, but i want to keep it smooth around the overlaps around the different shapes - ive spent long enough sanding already!

What sort of plastic is the bags used in female moulds?

Thanks

[dr_gn]

CubanPete said:

The fibreglass tissue I have is very fine, but i want to keep it smooth around the overlaps around the different shapes - ive spent long enough sanding already!

What sort of plastic is the bags used in female moulds?

Thanks

You can get special plastic for bagging, but it's not necessarily as simple as that. There are usually foam barrier materials and other interface sheets between the outer bag itself and the part, to stop the bag just locally sucking itself to the part where the connector is...it can all get a bit involved.

I think if you experiment with your glasscloth you will find it apples to contours extremely well. Try a bit on something with some tight double curvatures first and see how you go would be my advice. You can warm the resin a bit too to make it runny. Don't go mad though or it can start an exothermic reaction and then you're in trouble becaue it just gets hotter and hotter and there's not much you can do to cool it. Ask me how I know!