Windscreen...

[sblake161189]

Further to my previous post reg my dash...

I am now thinking of adding a windscreen/sheild to my boat, however I think the angle of which it would be supported would be too steep and not enough of the boat to attach it to (see pic no1). I think I would have to make it a very low screen but I wouldn't want it flapping around at the top as pure acyrlic... it would need some sort of hardened trim at the top to protect strengthen it... where do you get one of these or how would you create on... plus any ideas about improving the angle/size of base or does it look fine?
Any pics/ideas would be much appreciated...
Thanks /forums/images/graemlins/smile.gif /forums/images/graemlins/grin.gif

Also how easy is it to bend???

 

[jfm]

Sam
This is a how long is piece of string question! You could have a st/steel frame custom made but would cost a fortune. Here's one suggestion, at the budget end, but it's not the only answer:

1. This suggestion gives you a simple screen with a free top edge, ie no metal frame.

2. Make a template in 3mm mdf. Bit of trial and error. Start with cardboard and duct tape. You'll find it is a banana shape

3. If you can afford it, buy a massive piece of 5mm perspex (or acrylic, but that's MUCH dearer) and cut it out of that. Cut carefully with jigsaw. Tricky job, cos it melts on the blade

4. But it will be much cheaper to put a vertical joint down the centre of the windscreen, and fasten the two pieces of perspex together using 30x3mm aluminium strip both sides (from B+Q), thru bolted neatly using socket head c'sunk screws showing on the outside and dome nuts inside (from www.sea-screw.com). Painted black maybe

5. At the bottom, bolt the perspex to the angled face on the GRP, using section PVC266 from www.wilks.co.uk to cover the screws and form a soft gasket. Many boatbuilders used PVC266 for exactly this job in the 1970s and 80s. Available in black or white

6. Trim the top edge of the perspex with section PVC869 or similar, glued on

7. An alternative to perspex is 4-5mm marine play, painted black with lots of coats to make it look smooth. Cheaper and stronger, and will look quite cool. Remeber, it doesn't actually need to be transparent, cos you look over it not thru it. You could maybe (just) get it out of one sheet of 8x4 so no centre join needed. Still use section PVC266 at bottom but nothing at top edge


8. 5m perspex or 4mm ply will bend fine to that curvature

Good luck!

 

[sblake161189]

Brilliant information there matey, thanks a million /forums/images/graemlins/smile.gif

Will be looking on that website very shortly...

Will 5mm perspex bend that far round... ie as far round as the bottom left of pic no2. (but the shape of it going down to a triangular finish). Just got a horrible feeling it would not bend at that point and just crack, because its fairly gradual at the front but looks very sharp corner at the sides.

 

[tico]

jfm.... i'm surprised at you?
Perspex and Acrylic are one and the same (it's just ICI's trade name)

What I think you meant is 'Makrolon' (polycarbonate) as the more expensive alternative.

Acrylic is cheaper, clearer and more scratch resistant, but can be brittle. Polycarbonate is tougher, won't break.

when cutting acrylic with a jigsaw, keep it well clamped down and dont allow it to flap coz this will cause it to crack.

Otherwise... spot on!

 

[Nick_H]

If it doesn't feel rigid or strong enough after following jfm's method, you could always fashion a small stainless or alloy strut to brace the top of the windscreen to the top of the dash. It's normal practice on many boats to do this, so wont look out of place.

 

[MapisM]

Are you sure it's a see-through windshield you really want?
If you're not into a restoration "as it was" for the sake of it, I'd rather go for something like this. Stronger, cheaper, easier and (imho) nicer - on a small speedboat, at least.
An unbeatable combination.

 

[jfm]

Oops, you are quite right! I typed that in massive hurry, was rushing out to meeting, just back now . Yes, indeed, I meant to say "polycarbonate" where I said "acrylic". Thnaks for correcting me! Sorry Sam!

 

[jfm]

Yes, I'm very sure 5mm perspex or 4mm ply will bend to that curvature!

With perspex, you want to do it in warm weather, and if it's too cold gently waft a fan heater on it

Incidentally, perspex is very easy to bend into sharp angles if you make a former and get it hot with a heat gun. I've done this several times, it's pretty easy

 

[sblake161189]

thanks for all the advise guys, much appreciated... but im sure I will be back /forums/images/graemlins/wink.gif lol

 

[Cliveshep]

Make a template in hardboard that fits the curve and cut the shape in acrylic. Fine blade jigsaw, cutting slowly to avoid melting the cut behind the blade. Sand with a sander to smooth edges. Drill fixing holes over-size to cope with expansion or it can crack at the fixings. You will have to heat the ends with a heat gun (carefully) to get the curve. Screw with self taps and plastic caps to hold it on. It is a shape that is basically stable due to the geometry and will actually be quite stiff once fixed around the curve. Suggest yo start by fixing at centre and gradually form the curve by heating, working alternately left and right of centre and fixing as you go. Trim the top with a vehicle trim that just thumps on and grips (loads of them at car accessory or trimming shops to choose from). I did one many years ago on a home-built runabout, heated the ends at that time in mum's oven but that was 40 years ago when heat guns weren't around. I wouldn't bother with polycarbonate, too expensive and acrylic lasts for years anyway.

 

[jfm]

I'd advise against using screws and plastic caps to hold it on, cos you get a build up of cack in the thin gap twixt perspex and GRP and you'll be able to see all that cack thru the perspex but not be able to clean it. Section 266 as above is a better way and what many boatbuilders of that era used