How to join and clamp worktop under a corner sink?

I have read dozens of posts regarding worktop joining, but none seem to address my specific problem. Hope there's an expert here that can!
I have to fit this 90 degree corner sink into a 600mm benchtop: http://www.trade-appliances.co.uk/_4056_Blanco_ALA403.html
I have acquired all the kit: Jig & pegs (32 on ebay), Pro quality 1800W 1/2 router with 30mm guide plate (15 for the w/e from local hire shop) , new 1/2 x 2" router bits (15 B&Q). I have managed to complete everything else in this raised floor U shaped kitchen, so I'm game to have a go at this. (With a bit of practise on the old worktops!)
Question is how do I do the join that has to locate under the sink? A 45 degree cut will give me plenty of room for a couple of worktop bolts in the middle and back, but leave the joint at the from with no fixing, except maybe a biscuit.
A 90 cut gives me just enough worktop left to fit a front and rear bolt but it will be only sitting in the 50mm of bench in front and behind the sink.
Whatever I do it looks like I'm going to have a largely unsupported joint right under the sink! A recipe for failure and swelling me thinks. Any better ideas or tips?
While I'm at it, in the other corner, I have an option of a 90 or 45 joint in a uninterupted bench run around a corner. Is there any advantage to one over the other? (except I guess less router bit wear on a 90)
Finally, are bicuits essential or can you just use bolts? (Otherwise I need to go back to B&Q for biscuit router bit)
Thanks Steve
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On Mon, 30 Aug 2004 14:02:53 +0000 (UTC), "Yebligs"

I think that you will need to sketch it out on graph paper and see which arrangement gives the longer joint. The sink is a strange shape once the small bowl is taken into consideration.

The normal ways are to use a postform jig with a routerr and to cut either a 90 degree joint or two 22.5 degree joints and then have a piece of worktop across the corner effectively at 45 degrees.
This is typically used for a sink or sometimes a hob, but I don't think that the sink that you have would work in this way.

Especially in the sink area where you don't have much material.
Biscuits will prevent vertical movement of the worktops relative to one another while allowing a little horizontal movement for alignment. Bolts will pull the joint together but don't prevent vertical or horizontal movement of some amount.
I would definitely use biscuits and bolts,

.andy
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wrote:> >I have to fit this 90 degree corner sink into a 600mm benchtop:

I think what he needs to do is form the corner out of three work-tops. The corner will be a pentagon with a 90 degree angle. Difficult to see how the board that goes in the corner can be wide enough.
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On Mon, 30 Aug 2004 22:52:44 +0000 (UTC), "Michael Mcneil"

You can do this with a worktop jig.
If the piece across the corner comes to a point at the front, then I am pretty sure that it will be a quadrilateral, but that would only be the case if the corner piece could be formed out of a deeper piece of worktop. Otherwise, with worktop of the same depth as the main runs, there will be a triangle missing in the back corner.
I had to do an exercise like this not long ago for a built in desk that I put in my study. I made it from runs of block laminated hardwood worktop of standard 600mm depth. I wanted a sitting position in the corner where I could put a large 53cm monitor with keyboard etc in front. To fit this in required a run of worktop at a 45 degree angle across the corner. I cut the pieces using a worktop jig and router, but this left a triangle missing from the rear corner. To address this, I cut across the back corner with the router precisely along the edge of a block. I then cut out a triangle to make up the shape and end up with a point at the back. This was then glued and biscuit jointed together and clamped. The result is invisible as compared with the normal blocks. This gave me an non-regular but symmetrical hexagon which could then be fixed into place.
A similar technique could be used here except that the sink is a direct right-angle and not designed for this arrangement. If there were enough space, another solution for a corner sink is something like
http://www.franke.co.uk/prods.asp?prodid=7&pid=1&rtid=1
(PAX 652-E)
This has the advantage that you can stand squarely at it, but lacks the amount of draining area of something like
http://www.franke.co.uk/prods.asp?prodid=6&pid=1&rtid=1
(STX 621-E)
(similar to the OP's sink).
.andy
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I'm a bit concerned that doing a triangle is just going to give me 2 joins under the sink to swell and split, rather than one.
Although this would definitely be the best for the sinks you suggest, we've bought this one already!
I think can do a 90 join that will be under the least used bowl and I can still get a connecting bolt in at the front and back. If I can get a biscuit in too I'll be very happy.
I'll have to be very conscientious about sealing the ends. What's best, silicon or waterproof PVA? Most people seem to suggest silicon, but I'd have thought the PVA would seal in deeper?
Thanks for your help,
Steve
wrote:

bolts in

except
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On Wed, 1 Sep 2004 07:37:11 +0000 (UTC), "Yebligs"

Given the situation, I think it is probably best to go for whichever combination gives the most mechanical strength.

I would use silicone. It has some elasticity to deal with any tiny movements in the worktops.

.andy
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Whatever type of cut I do I'm going to have 100mm of uncompressed 45 joint at the front aren't I?
I found a sales blurb with a photo of the sink installed
http://213.123.251.98:8081/def/ala403ss2.jpg
which appears to show what I intended to do, which is a 90 degree, with the male on the right. (join behind bonsai sprayer, or it could be a twig :-))
This way I should get a bolt and a bicuit or two in at the back, and a biscuit at the front initially, followed by a large coach bolt into the end of the right piece once the cutout is made.
Lots of silicon and fingers crossed!
S
wrote:

fixing,
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On Wed, 1 Sep 2004 13:14:03 +0000 (UTC), "Yebligs"

From the picture, it looks to me as though they have used a combination.
At the front it appears that there is a 45 degree joint, and then a 90 degree one coming out by the Bonsai sprayer as you say.
The important thing is to get as much support as you can under as much of the sink as possible.
.andy
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If I was doing it I'd get the widest tops I could find and use a wide piece in the corner as I suggested or make one up out of sheet and put my own laminate on top.
No I wouldn't really, that's the way a workshop would have it done to spec. I'd just build up a laminate of 3x2s.
Put the units in and the first fix plumbing, then screw the first timbers all around to the wall and then the next to that, then the next to them and so on and so forth.
The job'd be done in half a day bar the varnish and the wait for the bloody plumber to get off his arse.
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