Bedding Acrylic Windows onto fibreglass cabin sides and other related questions

davidpbo

davidpbo

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Boatless in Cheshire. Formerly 23ft Jeanneau Tonic
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I am fitting new acrylic windows which bed directly on the side of the fibreglass cabin.

The previous ones were bedded with tape originally. I did re-bed one with the wrong Sikalflex and that seemed to develop crazing quickly, another I re-bedded with a flexible butyl sealing compound.

The replacements are 10mm thick (previous were 8mm on the side and 10mm on the front). I went for 10mm all round so it came out of one half sheet.

Is the recommendation to use bedding tape or an appropriate flexible sealant? If I use tape do I need to use sealant around the screws/in the screw holes.

The fixings are interscrews and the originals anodised aluminium should I use the same (probably not anodised) or stainless steel ( The internal trim is aluminium).

Are Hadlow Marine Services still in existence? the link to there web site is not working for me.

The edges of the supplied windows weren't polished and have the bandsaw marks. Presumably it is wet and dry then a polishing compound, a liquid car polishing compound without colour restorer (T Cut is out) or abrasives. Could someone recommend one please.

I have to drill 90 holes. Pillar drill and slow I know, would I be better off with a steeper angle than a normal HSS drill.
 
I would us butyl tape, when I did mine I used 2 strips, one covering all the holes and one outside of that. Seemed to do the trick for me with no leaks. If you have aluminium frames then the original fixings would seem to be best to avoid dissimilar metal corrosion however with thicker windows and butyl tape you may struggle to get them to reach at first. I hope you have the old windows to use as a drilling template otherwise you could have a problem! As for polishing the edges I have no idea, sorry.

Yoda
 
I removed three large windows in the wheelhouse of my motorsailer this year, all bedded on some sort of compound and all leaking. I used butyl tape when refitting, very successfully. The old windows would not clean up due to the variety of sealants and paint applied by previous owners, so at some stage I will replace the perspex, using butyl tape again. Tape supplied by Hadlow http://hadlo-43547-001.dsvr.co.uk/Pages/Introduction.html
 
Cannot comment on tape verses sealant or on interscrews as mine are in rubbers but ITYWF that sealant can easily be squeezed completely out of the joint if bending windows to a curved surface.

Hadlow Marine still there ( Google finds them !)

Seeing that you are located in the NE Eagle Boat Windows, in Nelson Lancs, might be of interest http://www.eagleboatwindows.co.uk/

Advice pages on both websites worth a read

More pointy drill bit is recommended for cleaner breakthrough in brittle materials. 60° instead of standard 118° ( also for wood!)

Small bits of perspex can be polished with "Brasso" .

Should have had the new windows polished and drilled b the supplier :)
 
I managed to stem the drips from my windows by following the advice in the Sikaflex manual, including using all the rather expensive cleaner and primer recommended.

A very important consideration is the correct allowance for thermal movement.
 
Just in the process of doing mine in 10mm acrylic drilled all the holes with standard HSS drill but drilled pilot hole and went up through the sizes.Polished edges with finishing sander using various grades and then used wet and dry and finished with metal polish.I am bedding them on 25mm wide and 3mm thick neoprene strip.
I wanted tinted acrylic but its not available in 10mm so thought of using car window tint film but have heard its not suitable for acrylic and causes crazing anyone used it?
 
Since the sealant is not having to hold the window material in place and it is just for bedding/sealing, then as the others have said I would either use Arbormast BR (butyl based) or a butyl tape.

I have bought the butyl tape from here recently and it arrived the next day..

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=151320872469

Butyl based sealant makes future replacement a quick and easy job.

The only additional thought is that the Arbormast BR is not really UV resistant.. (I don't know about the tape but I'd guess it would be the same)..

It is great for behind things like the aluminium framed windows or hatches but I have noted that when some of the boat manufacturers put in non-framed windows, they paint perhaps a 2" border around in a silver colour. This both makes the windows appear framed and also protects the bedding/sealant from UV damage.
 
As to finishing the edges..

As you say, wet and dry, used wet with a block by hand... It doesn't take too long to get a smooth mirror like finish.

You might search out some videos on YouTube of edge finishing with a heat gun (or blow torch).. You could smooth the edges in seconds but it looks a little fraught with risk..
 
peteK said:
Just in the process of doing mine in 10mm acrylic drilled all the holes with standard HSS drill but drilled pilot hole and went up through the sizes.Polished edges with finishing sander using various grades and then used wet and dry and finished with metal polish.I am bedding them on 25mm wide and 3mm thick neoprene strip.
I wanted tinted acrylic but its not available in 10mm so thought of using car window tint film but have heard its not suitable for acrylic and causes crazing anyone used it?
Click to expand...

You probably don't want to know this now like I don't want to know some of the things I have learnt recently, but mine are bronze tinted. I went for 10mm windows all round because so they could come out of one half sheet from a plastics
supplier.
 
There are quite a few effective ways of working acrylic, but these are my favourites. Drill the screwholes oversize to allow them to accomodate differntial thermal expansion. Use pan head screws rather than countersunk, so they allow the acrylic to float, a nylon washer under the head stops them biting into the relatively soft pane and a second washer between the acrylic and the coachroof prevents overtightening and expelling the sealant. A belt sander mounted upside down in the benchvice can be use as a linisher to smooth the edges and also straightens the long sides. Using a pillar drill an ordinary drill bit will be fine as you can control the feed and go slowly to avoid chipping.

I can't see how an additional tinted film would cause crazing - its just floated on with a water film - unless it increases heat retention in the sunshine, but the spray on tints may well damage the material as can some adhesives. As others have said, butyl mastic will accomodate expansion better than others but may have a shorter life due to UV degradation.

Rob.
 
We have tried a number of different options including Sikaflex 291, and different butyl rubber compounds, one self-imposed constraint in our case being that they should be black to match the colour scheme (which probably causes its own problems due to heat absorption).

None of the sealants/adhesives have worked particularly well for various reasons, so this year when we had to replace the front window, after a lot of research, we settled on Marlon FSX Longlife polycarbonate for the window and 3mm adhesive neoprene tape for the sealant. The polycarbonate is supposed to be UV reflective, so we are hoping that it will protect the neoprene from degradation. So far we have been very pleased - it is much neater and easier to work with than BR, and is 100% leak proof (after 6 months!). Time will tell whether it is a long-term solution.

An account of our experiences with trying to seal windows is at http://shetlandf4.wordpress.com/windows/ if you are interested.
 
davidpbo said:
You probably don't want to know this now like I don't want to know some of the things I have learnt recently, but mine are bronze tinted. I went for 10mm windows all round because so they could come out of one half sheet from a plastics
supplier.
Click to expand...

Pretty sure Righton's supply it off the shelf, if not wouldn't take long to order... Depots all over the UK: http://www.righton.co.uk/
 
Countersink the coachroof hole and the window hole and when tightened up the sealant will fill these to give a good overall seal to the bolts.
 
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