Piece of plastic for hatchcover skylight?

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Nicholas123

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For my next project I would like to convert my solid fibreglass fore hatch to see through.So I need a bit of perspex type plastic 18" by 22" inches square (46 by 56 mm).

It needs to be flexible enough to take a 1/2" curve & be strong enough to walk over. So I'm guessing about 10mm thick minimum? Anybody know the type of plastic I need & where is can be obtained close to Fareham?

Can offcuts be obtained over the internet? That would be ideal as I've drawn a blank with my forays around Fareham so far. :encouragement:
 
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Either acrylic or polycarbonate will do. The latter is stronger but is more easily scratched. 8mm will be fine, but you may struggle getting that curve without applying a bit of heat and you will need good fastenings.

Widely available from many sources particularly sign makers - just google for local suppliers as prices can vary. Well worth getting it cut to size and the edges finished.

Sunlight Plastics are local to you and specialise in "marine" - but my not be the cheapest.
 
Just to add to Tranona's advice, acrylic goes by several trade-names: Perspex, Plexiglass, etc. Anyone selling it should be able to confirm what it is. There are companies which will undertake bending for you, but that would add substantially to the cost. If doing it yourself, heating is required for anything but a slight curve, but with progressive controlled cooling afterwards, rather than just letting nature take its course.

From memory (i.e. fallible) hatch manufacturers such as Vetus generally spec 10 or 12mm acrylic for offshore use, although this may take account of degredation over time. In your application, much of the strength will depend on the method of attachment...I presume with a generous overlap?
 
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Wot Tranona says +1

I think even 8mm will need some heating to bend that much

Sunlight plastics ( Waterlooville) will I am sure be able to "drape mould" it to match the curve of the hatch if you can take it off and take it too them. I had two windows drape moulded using the old ones as patterns ( although not by Sunlight) I don't remember any huge addition to the cost. It's if they have to make moulds that the cost escalates .

As well as getting the edges finished it might even be worth getting it drilled.

You dont say how you will be fastening it but remember countersinking fastenings is not advised.


You could go down the cheap off cut route but you may not easily get the colour/ tint of your choice and you will be on your own regarding cutting to size, edge finishing . drilling and moulding to shape go.
 
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Thanks gents.I want clear not tinted & the overlap I am aiming for is about 3" each side of the width which is where the 1/2" curve is pulled down.
I shall use stainless steel allen socket type pan head bolts & shall drill them as I see fit :encouragement:
 
You may want to use something with a bit of give in it within the assembly. The Acrylic will have a different expansion rate to the hatch.
I'd also consider using a load spreader accross the bolts if you intend to be able to stand on it.
 
Nicholas123 said:
For my next project I would like to convert my solid fibreglass fore hatch to see through.So I need a bit of perspex type plastic 18" by 22" inches square (46 by 56 mm). ...
Click to expand...

I'm shure it's only a typo, but 18'' by 22'' inches equals to 46 by 56 cm. (Just before ordering the wrong parts)

Cheers, Christoph
 
prof pat pending said:
You may want to use something with a bit of give in it within the assembly. The Acrylic will have a different expansion rate to the hatch.
I'd also consider using a load spreader accross the bolts if you intend to be able to stand on it.
Click to expand...

The hatch itself is pretty flimsy so I don't see 'give' as a problem.You might have something with regards to different expansion rates but I think I'll just have to risk that.
I intend to drill & bolt it in a sort of stitch pattern so the load should be well dispersed.:encouragement:
 
dunedin said:
Anything you want easily obtained from the inter web .... Particularly if you want pre cut to size

Various I suppliers including this site where I got some recently
www.simplyplastics.com
Click to expand...

That links brilliant thanks.For Clear extruded acrylic sheet it seems to work out at £2.94p excluding postage & packaging which I would'nt know until ordering.
Brillo :encouragement:
 
Skipper_Christoph said:
I'm shure it's only a typo, but 18'' by 22'' inches equals to 46 by 56 cm. (Just before ordering the wrong parts)

Cheers, Christoph
Click to expand...

Thanks for flagging that up.Fortunately their computation device required it in mm's so no harm was done.I managed to work it out at 457 by 559 mm's :encouragement:

I shall sit back & see if anyone can see a fault in what looks like a good buy before placing an order.
Bye the way that order input was for 8 mm thick stuff.I'll clean up the edges & round off the corners & drill the piece myself when I lay it out down my boat.That is the plan! :encouragement:
 
Nicholas123 said:
Thanks for flagging that up.Fortunately their computation device required it in mm's so no harm was done.I managed to work it out at 457 by 559 mm's :encouragement:

I shall sit back & see if anyone can see a fault in what looks like a good buy before placing an order.
Bye the way that order input was for 8 mm thick stuff.I'll clean up the edges & round off the corners & drill the piece myself when I lay it out down my boat.That is the plan! :encouragement:
Click to expand...

Unles you actually have a bench pillar drill/ drill press on the boat it would be better to drill the holes in your workshop before you take it to the boat.

Also be sure your drill bits are ground to the correct angles etc for drilling acrylic.
Clamp to a suitable MDF board to reduce the likelihood of chipping when the drill breaks through
Water is a suitable lubricant/ coolant

Take care you dont want to be buying the plastic twice
 
VicS said:
Unles you actually have a bench pillar drill/ drill press on the boat it would be better to drill the holes in your workshop before you take it to the boat.

Also be sure your drill bits are ground to the correct angles etc for drilling acrylic.
Clamp to a suitable MDF board to reduce the likelihood of chipping when the drill breaks through
Water is a suitable lubricant/ coolant

Take care you dont want to be buying the plastic twice
Click to expand...

I like the idea of my workshop Vic......it's actually my kitchen :D

I'm sure I'll manage,I always have done.One of the biggest considerations from a technical standpoint is my leccy drill only goes up to 650 rpm but again I usually get there in the end.What concerns me more having gone down my boat yesterday is the degree to which I need to bend this stuff to fit.It's about one inch on each side & I have doubts about being able to do that with 8mm stuff without distorting the frame.I may have to drop down to 5/6mm.
I really need to see some of this stuff to see how flexible it is.
 
I replaced the fibreglass fore hatch on my W25 with a polycarbonate one. I suggest you look very carefully at the shape of your old one because it may be quite a complex shape when you get down to detail.
I made a cardboard mock up of what I needed and got Barkston plastics of Leeds to fabricate it
The construction was made from 3 pieces one of these formed the front the top and the back. The two sides were then bonded in under the inside edges of the larger piece
The hatch was fixed in with pivoting screw/ acorn fittings designed for sash windows. These were bolted through the top face
Incidentally this made the forward section much lighter even after I put a small solar panel under the hatch to trickle charge the battery
Martin
 
I'd seriously consider having the holes drilled before you go down to your boat. If you crack the Perspex down there you might have a hole letting in the rain.
 
Halo said:
I replaced the fibreglass fore hatch on my W25 with a polycarbonate one. I suggest you look very carefully at the shape of your old one because it may be quite a complex shape when you get down to detail.
I made a cardboard mock up of what I needed and got Barkston plastics of Leeds to fabricate it
The construction was made from 3 pieces one of these formed the front the top and the back. The two sides were then bonded in under the inside edges of the larger piece
The hatch was fixed in with pivoting screw/ acorn fittings designed for sash windows. These were bolted through the top face
Incidentally this made the forward section much lighter even after I put a small solar panel under the hatch to trickle charge the battery
Martin
Click to expand...

As far as I can tell there are no compound curves.I think it will pull down alright if I can just get something flexible enough in the first place.
 
philwebb said:
I'd seriously consider having the holes drilled before you go down to your boat. If you crack the Perspex down there you might have a hole letting in the rain.
Click to expand...

Is Polycarbonate of acrylic harder? That is a consideration.I did a previous boat hatch alright but can't remember what it was I used.It was fifteen,twenty years ago!

At just two or three quid delivered as far as I can see,I'm not risking much. I can afford to experiment.
(It will be bedded down on silicone rubber type goo).
 
Nicholas123 said:
Is Polycarbonate of acrylic harder? That is a consideration.I did a previous boat hatch alright but can't remember what it was I used.It was fifteen,twenty years ago!

At just two or three quid delivered as far as I can see,I'm not risking much. I can afford to experiment.
(It will be bedded down on silicone rubber type goo).
Click to expand...

Polycarbonate is very much stronger and best if you intend standing on it. Do not use silicone sealer but bed it down on butyl, either from a tube or us the proper tape which you can get from a glazing supplier. Silicone does not adhere well to the plastic. Do all the drilling and screwing - making sure the holes are clearance as the plastic expands at a different rate from the screws. When you are happy with the fit, remove the screws, lay the tape and then screw down permanently.
 
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