fitting sink in laminate worktop

I have a sink to fit in a laminate worktop over a 1000 x 600 cabinet. Its a 1.5 bowl and drainer, total external dimension 1000 x 530 mm. The sink has a flat steel "designer" flange all around which includes the tap hole and is about 60mm wide along the front and back (only about 25mm around the sides). The fixing lugs are set 15mm in from the edge. The lugs take nylon/metal claw type clips that hook onto the lugs and tighten against the underside of the worktop.
Now, the obvious way to fit the sink is to form a single large cutout 974 x 504mm (4mm to allow tolerance and space for the metal clip to fit on the lugs). However next to the sink is a gap for a washing machine which leaves very little supported laminate along the edge of the sink.
So my general plan is now to cut out as little of the laminate as possible. I'll do a main cutout for the bowls. Along the front and back with the large flange, I'll only cut where I need to (i.e. slots for the fixings lugs and clips, and a hole for the tap. This will also give a lot more sealant contact area and better support for the bowls. It will also help to constrain the fixing clips which have been known to slip off, I'm led to believe.
For the drainer, which has a depth of between 10mm and 20mm, I'll just route out as much depth of the worktop as required to allow clearance. Since the drainer is on the washing machine side, this will provide a lot more solid material where it is needed, and make the metal "ring" less with water dropping onto it.
The only flaw in all this is that there will be a lot more surface area of naked chipboard to get wet if the sealant around the edge were to fail. I plan to waterproof this with plenty of varnish / oil-based paint etc.
Question: Is all this trouble worth it, or should I just cut the big hole and have the thing only supported on 15mm all around the edge ?
At the very least, I think I'll need to avoid cutting right through under part of the drainer to give more solidity next to the washing machine.
Simon.
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wrote:

Use a thick coating of waterproof wood glue.
Gives a seal with one application.
Thomas Prufer
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On Monday, July 9, 2012 8:01:14 AM UTC+1, Thomas Prufer wrote:

Ah. Do you have an example brand in mind, or just waterproof PVA (EVA etc) ? Simon.
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If you have a router then it seems a sensible solution to a tricky problem.
Fibreglass resin, perhaps with a layer of fibreglass tissue for binding/reinforcement should see to any water ingress problems, cheap, waterproof and very tough.
A few thick lines of sealant (clear Plumbers' Gold recommended) between drainer and now waterproof chip under will reduce tinny drumming and stiffen it up further. Run the beads "downhill" just in case to avoid the risk of trapped moisture. PG above also suggested for the main bedded insert seal but do apply a taped template mask to the area round the insert and mask the insert itself first as the stuff is a combined sealant/adhesive and will stick like shit to anything it touches.
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fred
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On Monday, July 9, 2012 1:01:42 PM UTC+1, fred wrote:

I don't ! Time to get one I think. And read the wiki on routers (if there is one) Simon.
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Using one will have the advantage of leaving a relatively smooth surface, albeit with steps, which will make waterproofing easier and more reliable.
You will have a lot of material to remove so maybe hire a decent 1/2" one (collet size) to try which will have more power than a budget 1/4" machine. Even with a beefy one you'll need to do it in stages, routers don't really do big chunks. I'm not great at this but reckon you could do 3mm depth per pass on a 40mm cutter with a decent machine (happy to be corrected).
Also, you'll need to get it right first time, deepest cut first, taken in stages then move back to the next deepest and so on. This is cos you will lose your supporting edge as you cut back so won't be able to back for a second bite easily.
Good luck!
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fred
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On Monday, July 9, 2012 3:53:23 PM UTC+1, fred wrote:

It would probably be best to route around the edge of the area to the correct depth first, then take out the middle I would think. It would also be possible to remove some of the bulk without the router, cutting a series of grooves and snapping out in between, but that wouldn't leave a nice smooth surface. Simon.
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