perpex windows

[homerj]

I`m thinking of making new windows for my boat possibly getting rid of the old car type seals and through bolting perspex panes onto sealant. the largest area would be 20" by 10". Any idea of pane thickness reqd. and other advice would be appreciated.

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[Little_Russel]

I found Crouch Marine Windows very helpful.

<hr width=100% size=1>Sail the Se7en seas...

 

[bernard_foster]

I would use polycarbonate, If you through bolt with nuts and bolts, or captive nuts, and overtighten slightly, perspex will spider out, Poly will not

<hr width=100% size=1>Bernie Foster

 

[cameronke]

I had been warned that polycarbonate, though being extremely tough is soft and vulnerable to scratching. It is also prone to UV bleaching. Acrylic (perspex) is resistant to UV and comes available with a hard coat to resist scratching Marguard is one brand that I have used.

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[charles_reed]

If you are changing windows

you would be well advised to replace them with toughened glass in a proper frame.

The proposed course of action will be cheaper but a comparitively short-term solution to your current problem. Leaks, due to hull working and expansion/contraction will start in about 3 years and the acrylic will UV degrade within 10 years (less if you're in a sunny area).

there are a number of specialists who will either do the work for you, supply the windows or the materials.

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[beneteau_305_553]

I would suggest :

- 8 mm thick tinted polycarbonate (Makrolon). Its almost unbreakable and very tough.

- Bed it onto neoprene foam tape rather than sealant as this is much more tollerant of movement without leaking as it is always in compression.

- 6mm stainless bolts at about 150 mm centres and washers both sides and nyloc nuts on the inside. Don't overtighten the bolts.

- Bolt the window on first without the foam. Then remove the window clean the surfaces and fit the tape to the grp. Bolt the window back on by pushing the bolts through the foam ( make a small hole with a screwdriver )and trim off the excess foam with a knife.

<hr width=100% size=1>Richard<P ID="edit"><FONT SIZE=-1>Edited by beneteau_305_553 on 06/01/2004 10:13 (server time).</FONT></P>

 

[paulrossall]

I used the method described by beneteau_305_553 but I used 12mm acrylic. I did intend to use 10mm but the supplier was out of stock. He advised me that perspex would scratch too easily. Did 3 windows at cost of £100 for the acrylic cut to size. Neoprene tape abtained from ARCO rubber who have trade counters in many cities. My bolts were longer but use the washers and nylock nuts. If I had to do the job again I would use the 12mm thickness. It looks very good and it has plenty of strength.My biggest window was about 3ft by 18inches.

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[MainlySteam]

I agree with the comments opposed to use of polycarbonate. Polycarbonate is not recognised as being a good material for ports, windows or hatches due to its ductility and flexibility making it hard to seal (and hatches sag if you stand on them), it is soft and scratches, and its UV resistance is a bit of a trial.

No doubt there will many screams about that, but the simple test is to just check what the best quality hatch and port manufacturers use. For example, Lewmar do not offer polycarbonate.

I could not authoratively recommend a thickness, as was asked in the original question, as the boats I am involved with all have glass or bought in ports and hatches and are much bigger. However, for a 20 foot vessel which originally had rubber mounted windows (so is a completely sheltered waters vessel) I would have thought 8mm would be sufficient for 10 x 20 inch windows - maybe 10mm if one was going to stretch the capabilities of the vessel beyond completely sheltered waters. That would also seem to align with Paulrossall's experience with bigger windows.

John

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[Spuddy]

I didn't want to lay out a lot of cash to replace windows which sounded much like yours were. Like yourself decided to switch to through bolted. A ring around using the yellow pages plus asking a proper chandlers put me in touch with several Daves in industrial estates. These little missions are time consuming but I look on them as adventures - one took me into tuunels that burrow beneath the Dover cliffs . It can start to get a bit hobbity.
Anyway - yours are about the same size as mine. I found some 3mm neoprene sheet quite cheap off the end of a roll from Dave. Then another Dave used my card templates to sort out some offcuts of 6mm acrylic ( perspex, same thing).
The M6 SS machine screws werequite cheap as well ( not in blister packs from the chandlers)
The neoprene was cut out into gaskets ( didn't know about tape). Assembly was acrylic then neoprene bedded with sealant down onto coachroof sides. I nipped it up a little, waited until the sealant had gone off and then tightened up - not too much or the acrylic will crack.
Can't tell you about knockdowns or lifetimes I'm afraid but it was cheap, easy and better than what was there

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[Blue_Blazes]

Re: If you are changing windows

Couldn't agree more Charles. Through bolted plastic (either sort) is a bodge, and looks crap to boot. Better (but dearer) to get some proper frames made up.

Bill.

<hr width=100% size=1>One of these days I'll have a boat that WORKS

 

[paulrossall]

Further to my earlier post I should have mentioned that the bolt through windows look very smart indeed and a number of people have said what a proffesional job has been made of them. I forgot to mention that I had the outside edges of the window beveled at 45 degrees through about the outer 1/3 of the material. I have seen many cases of replacement framed windows that look a bit of a bodge and once they start leaking it is difficult to make them watertight again whereas it is comparatively easy to reseal my bolt through windows. Hope this helps. Paul

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[MainlySteam]

Re: If you are changing windows

Your statement maybe a little unfair. My personal view is that anything under around 115 foot and not finished to the highest possible standards is absolute crap. Unfortunately most of us have to make do with boats which are within our budgets or appropriate to the wealth we are interested in committing to the sport.

In this case, both you and Charles are suggesting solutions which will result in a cost that is inappropriate to the value of the vessel unless, of course, one wants to put money in, through some love affair with the boat, which will never be recovered.

On the life of acrylic under high UV exposure (hardly likely to be a problem in the UK I would have thought), UV stabilized acrylics have a very good record, even here in New Zealand which reputedly has very high levels of UV. Horizontal hatches are the most exposed and unless one uses unstabilized acrylic (which I have seen used) one would expect a life very much greater than 10 years with modern acrylic. In our own case our hatches are 7 years old and they show no sign of UV damage whatsoever.

In any event for vertical windows, the life will be very much greater as their exposure to UV is very much less. I would suggest that for them, assuming a stabilized acrylic, deterioration from UV will never be an issue.

John

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[Blue_Blazes]

Re: If you are changing windows

<<inappropriate to the value of the vessel>>

Not necessarily. A simple external metal frame mounted outside the plastic will not only spread the loading from the through bolts, (no star crazing), it will also look 10 times better and will probably make the boat easier to sell when you move up to your 115 footer.


Bill.

<hr width=100% size=1>One of these days I'll have a boat that WORKS

 

[MainlySteam]

Re: If you are changing windows

Lost me I am afraid - not sure why Homerj would want to sell his boat when I get a new 115 foot one.

John

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[LeonF]

Ealy Sigma 33 boats had perspex screwed over the aperture with self tappers. I replaced my leaking windows with thicker perspex-10mm and made the holes 1mm larger than the bolts. I used interscrews which are a bolt with a female nut. Anglia stainless stock them as do many others. I also used self adhesive neoprene tape. Talk to Salford |House windows near Sevenoaks, Kent. Sikaflex will break down with UV in time. Later Sigmas have proper aluminium frames but these are also prone to leaks even in relatively young boats. My windows are totally leak free.

<hr width=100% size=1>L.A.R.Ferguson

 

[richardandtracy]

The designer of my boat recommends 3mm (0.125") for every window with a short dimension up to 24". I think this is a bit thin, and reckon 6mm would be a better minimum. For hatches & skylights, 12mm minimum (0.5") is recommended. I have used 2mm as secondary double glazing at home, and it flexes like anything with a 30 x 60" window.

While CSK is very nice, unless you have a large clearance hole on the other side, I think you run a risk of cracking the acrylic. Do not forget that acrylic expands like crazy in hot weather, and the thermal expansion loads, if you run out of clearance, can be HUGE.

Bolt spacing should be about 8 diameters apart around the perimiter, maximum 10x material thickness. In other words, use lots of small bolts (that's what they do on aeroplanes too).

PC is much softer than acrylic & does scratch. But it's impact strength is about 50x better. It's more expensive.

Regards

Richard.


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[Blue_Blazes]

Re: If you are changing windows

LOL.

Perhaps I could have phrased that better.

Bill.

<hr width=100% size=1>One of these days I'll have a boat that WORKS

 

[Guest]

Funny how .....

There are lost of boats on market and happily sailing around with bolted through plastic windows ...... frames or no frames ..... mirages etc. etc.

They seem to sell ok and give good service.

Quite a few boats I know with plain bolted windows have taken them off every few years and re-bedded without hassle ... in fact a boat near mine now - re-beds on a regualr basis - NOT because he has to, but does it because he thinks it good preventive measure - can't argue with that !


<hr width=100% size=1>Nigel ...
So WHAT does the EU really stand for ????/forums/images/icons/cool.gif

 

[homerj]

Re: Funny how .....

Thanks for all the interesting comments, I think through bolting is the option for me with 6mm or 8mm acrylic and a nice bevel around the edges.

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[charles_reed]

Re: If you are changing windows

In fact your assumptions about the cost difference are probably incorrect and therefore your comment of doubtful validity.

The cost of toughened glass (cut and then treated) is about 65% of UV resistant tinted acrylic.
Admittedly one has to then cost the window frames, but standard anodised extruded section suitable for window frames is about £1.80/ft (£5.80m). There was an aluminium stockist in Christchurch, when I was there in 1990 who had such a section in stock.

Admittedly if you have to pay someone else to make up the frames for you the price could well quintuple.

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