Drilling / fixing polycarbonate

Hadenough

Hadenough

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I need to replace the perspex?? (unknown material) to my wheelhouse roof hatch. It is big, 1.6m wide x 0.8m and fits into a substantial teak frame with a slight curve to the longer dimension, which slides open. The existing "glass" is held in an aluminium frame which being smaller than the overall frame is spaced out to the frame with approx 30mm of thin ply. The ply has rotted and the perspex is scratched but the teak frame is perfect.
My proposal therefore is to do away with the ply infill and ally frame, rout a rebate into the teak frame and directly fix a new perspex?? light into the frame. I am thinking of using 6/8mm Lexan and will be taking advice from the local suppliers as to the best material.
Searching the forum though I have come across the following bits of advice for this type of job:

1. Butyl tape for the seal.
2. Oversize fixing holes for clearance.
3. Slight countersink to the fixing hole to avoid cracking.

I intent to use stainless pan head screws with penny washers and neoprene washer seals at 100mm spacings. Not sure though about drilling method / best type of drill / pilot hole or not?
Anyone done anything similar or have any other nuggets of experience to offer.
Thanks in advance.
 
I used polycarbonate for my new washboards. I didn't have to drill them, but I did use a router for the rebated joint in the middle and for the cutout that the lock module fits into. The material seemed fairly well-behaved with the router so I expect it would drill fine too.

Pete
 
Drilling is straightforward, but you might do better buying from a sign maker and having them drill it for you.
 
When you drill it, back the leading edge of the drill bit...
Meaning take the sharp cutting edge off slightly on a grinding wheel, this will stop the drill twisting in fast into the material,

Use polycarbonate perspex
 
For what it's worth, Lexan(tm) is polycarbonate and Perspex(tm) is acrylic. Both can be transparent but with somewhat different properties. Polycarbonate is normally recommended for impact resistance. I'd go 75mm spacing with the fasteners personally but the other info works.
Doing the drilling and fitting when the material is warm would be advisable as this is the time when the hole might fracture out to the edge, which scraps the material in one fell swoop.
Reducing the tool angle is good advice, but the drill must still be sharp! Otherwise the localised heating can cause the material to crack.
Lexan is supplied with one surface treated to face out, ie it has better UV resistance. This info is printed on the protective film.
Good luck with the job.
Cheers
Rum Run
 
Tranona said:
Drilling is straightforward, but you might do better buying from a sign maker and having them drill it for you.
Click to expand...

+1.

Drilling perspex, acrilic, lexan-all can be tricky.

Having drilled many double curvature racing motorbike screens over the years one trick is to profile a bit with an almost flat tip-only just off horizontal.

Better to give the old screen to whoever makes the new one and get them to make the holes.

They should get them in the right place-and not crack it! If they bugger it up they will make another one, at their cost.
 
rotrax said:
Drilling perspex, acrilic, lexan-all can be tricky.

Having drilled many double curvature racing motorbike screens over the years one trick is to profile a bit with an almost flat tip-only just off horizontal.

Better to give the old screen to whoever makes the new one and get them to make the holes.

They should get them in the right place-and not crack it! If they bugger it up they will make another one, at their cost.
Click to expand...

Glad I hadn't read this thread before making my polycarbonate washboards :)

Pete
 
In my experience hefty acrylic ('Perspex' etc) is OK to drill; as Rotrax says, motorcycle screens are a different matter, being only 2-3mm thick. Just don't use a new steel bit (a blunt one is OK), and don't go too fast. If drilling and, especially, countersinking thick acrylic, it's worth letting the job cool rather than drilling right through in one go: excessive heating/cooling sets up stresses in the material which can become stress raisers.

If the OP's job permits I'd consider countersunk fasteners with butyl 'cones'. Providing the fasteners aren't done up too tight, this permits a degree of expansion movement whilst retaining a watertight seal. But whatever through-fasteners are used, the holes should be slightly oversize: acrylic has a very high coeff of expansion.

As others have suggested, the OP seems a tad unsure re acrylic/polycarbonate. The latter is certainly tougher but very prone to scratching.

This link has useful info about what attacks acrylic and what doesn't (some of them surprising):
http://www.professionalplastics.com/professionalplastics/content/AcryliteFFDataSheet.pdf
I've found olive oil effective (with a fair bit of elbow grease) at removing traces of butyl rubber.
 
I have recntly replaced a window in the little boat. I used a drill press ie a bench drill or pedestal drill. The reason being that i could easily apply just a light pressure to the drill to avoid that screwing in effect rather than cutting which perspex is prone to. I too would suggest more closely spaced screws rather than 100mm. My window was inclined to leak water and tightening the screws on crude gap filler didn't help much. Indeed I could see the perspex getting distorted under the screw. So yes pay attention to the sealer and don't tighten the screws too much. good luck olewill
 
Thanks all, good advice. Going to see the supplier tomorrow to talk the job through. He will be cutting to size and I am leaning towards getting him to drill the holes as there are so many. I can spend my time better prepping the frame. I'll report back.
 
Just done the job yesterday between showers. seems to be holding and watertight. 6mm holes with M5 pan head machine screws, remember to get them long enough as with arbor tape stuff the gap needs to squashed to about half depth of tape.
 
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