perspex window for a hard dodger?

[Niander]

Over the winter i built myself a hard dodger for my yacht as i had no shelter
It went very well [even looks good]but took many hours [but my time is cheap]
Anyway, im thinking of windows now and the front one is 1400 mm x about 300mm
so im thinking how thick should I get 8 or 10mm what say you?

 

[Tranona]

Is it flat or curved? 8mm will not curve much cold. Use polycarbonate and think 6mm would be fine.

 

[Niander]

totally flat but i gota cut curves
just thinking of waves hitting it.[not that I'm thinking of the southern ocean]
why use polycarbonate?

 

[Scotsailor]

I would use 8mm

 

[Niander]

Ok im also wondering whats best type of plastic and why?

 

[NormanS]

Polycarbonate is very strong, but very easily scratched. The storm boards for my deck saloon windows are Polycarbonate.

 

[Niander]

hmm, don't want easily scratched...?

 

[pvb]

hmm, don't want easily scratched...?

How's it going to get scratched? If you're vaguely sensible, it won't.

 

[jac]

But only takes spmeone dropping something. OP may stow dinghy lashed down infront it and dinks are not easy to manhandle. Battens, shackles, tools etc dropping when bending on sails. Plenty of ways that someone could drop something metal.

 

[Tranona]

Ok im also wondering whats best type of plastic and why?

Polycarbonate because it is stronger and virtually unbreakable. The scratch proneness is not really an issue in your application. I have used it for windows without any problems as they are not in a situation where scratching is common. Your panel is very narrow - almost like a slit in a gun emplacement. ^mm will be fine strengthwise. 8mm would be very heavy and very much more expensive.

Presumably you are screwing or bolting flat on the GRP. If so have a good overlap - 30-40mm, drill clearance holes for the screws (pan head) and bed on butyl tape. Unless you are very handy you may find it better to have it cut and drilled professionally. Shop around as prices vary. No particular need to use a "marine" supplier. I had my last set of windows cut by a local sign maker.

 

[William_H]

In the Southern Ocean the concern seems to be that the boat can be bodily lifted up and thrown on it's side so gunwhale and then windows take the shock. But if you are not going into rough water not so much of a concern.
Regarding scratching, on my little boat the jib sheet car and sheaves are set up on a spring. The sheave sides are inclined to scratch the window when the jib is flapping. So scratching marks do appear. On my TS the windows are about 5mm thick for dimensions similar to yours. olewill

 

[Niander]

Polycarbonate sounds very good then whats good about this butyl tape?
yeah panhead stainless bolts sound good im thinking of fibre washers ?under them also to seal them.

 

[rogerthebodger]

Polycarbonate sounds very good then whats good about this butyl tape?
yeah panhead stainless bolts sound good im thinking of fibre washers ?under them also to seal them.

Polycarbonate is also susceptible to UV and does go cloudy when exposed to UV.

I fitted polycarbonate to all the windows on my previous boat but had to replace then due then going cloudy.

https://www.irbnet.de/daten/iconda/CIB1832.pdf

Also do be careful in the fixing as both perspex and especially polycarbonate will crack when subjected to uneven stresses caused by fixing screws even with backing washers under the screw heads.

On my current boat my cabin windows are gebo which use perspex and my wheelhouse windows are toughened laminated glass but my biggest is 1200mm x 750mm.

 

[Niander]

I think ill be covering them up under a cover when not in use.
also, i recon don't over tighten bolts they don't need to be that tight and can always be tightened if loosening.

 

[Jeepster]

You don't need thick Perspex...I am using bronze tinted 3mm for lightness (my screen is about 1600mm x 670mm) and I beef up the stiffness with a custom made stiff Aluminium frame, which again is designed to reduce the weight. It's best to sandwich the Perspex between two pieces of Ally, and you can countersink the outer holes for a flush finish, with A2 washers and nylocks on the inside...CSK A2 stainless screws, washers and nylocks are very cheap in Toolstation (just as good as A4 stainless for most uses.)
The perspex for my screen cost me £114 all in, including the cutting to size and shape, and the ally sections for the frame were about another £50...So it doesn't have to cost the Earth either.

 

[Niander]

Good as i have 5 window openings!