GRP thickness for a shower tray

[RogerMayne]

Hi, I have a plastic shower tray on my boat. It is cracked and needs replacing. It seems to be built into a ply form for support.
I want to cast a new one in situ using the existing ply shape as a mould and support ongoing.
Will two layers of 450gsm grp finished with a layer of tissue and painted with topcoat be strong enough? (I weigh 18st)
Cheers

 

[rob2]

Can't do the maths - but maybe you should consider improving the ply sections so that the GRP is really only a waterproofing layer? Interlinked vertical strips under a ply sheet should do it.

Rob.

 

[G12]

I'm pretty sure 900GSM won't be good enough unless it's just forming the waterproof barrier for the structure underneath.

 

[nimbusgb]

I have a large ( 1200 * 900 mm ) glassfibre shower tray. Layup is polyester and CSM. Unsupported across a lot of its area. Thickness around 3.5mm. With 1 adult in the shower it 'creaks' occasionally.

Two up it is not a happy piece of kit

 

[bendyone]

I did mine about 1m square with 3 layers of 450 mat and finished it off with surface tissue then a flow coat of white, all on a good ply wood base. Moulded in a drain into a sump box. Worked well for me

 

[Bav32]

How about the same thickness as your home shower or bath and treat the ply as a bonus.

 

[William_H]

Shower base

Clearly the original was not strong enough or more likely not supported sufficiently. The support may have rotted away if wood. You need to look at the places it cracked and work out why. If you improve the support then the proposed layers should be fine if the original is left in place.
Or remove the original and mold the same thing (make a mold from the original and use it to mold a new one) but make it just a little thicker or a lot thicker if you don't find a failure of support. good luck olewill