What do I use to produce a nice curved corner in wood

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cygnusv

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In the early summer I fitted 2 new fresh water tanks to increase our usable capacity. One of these 2 tanks is visible so I want to make it appear to be a nice mahogany (faced plywood) locker / table. The top and the sides are sorted but that leaves one visible corner. I don't want this unit to look like a box so would like the 'corner' to be rounded. The curved 90 degree bend is just under 60 cms high and I'll need to produce a 100mm radius. The bend will be a total 90 degrees with a 25mm straight at each end to attach the piece which will ideally be 12mm thick to match the rest of the hardwood faced ply.

Any thoughts about a material to use ( I can laminate to make up the thickness if necessary ) and where I can actually buy a practical material to do the job bearing in mind the 100mm radius?

Thanks in advance.
 
If I was doing the same, I think I would make a faceted version of the curve with perhaps three or four faces, using strips of solid cherry (because that's what my joinery is). The joints would be essentially butt joins at the appropriate angle (cut with the router using a simple jig to raise one side of it to set the angle), with a groove to take a spline of 3mm plywood. Then when it was all glued up and set, I'd hand-sand the facets into a curve with 80-grit paper on a foam block.

But that's just me.

Pete
 
You could use bendy ply available in b and q . laminated it holds its shape. When you get the shpe you require then cover the piece with veneer or maybe laminate on a piece of 1/8 inch faced ply.
 
I would get a length of PVC tube of the correct radius or slightly less and laminate a few veneers around it with epoxy or polyurethane glue.Since I have a vacuum pump I'd vacuum bag it but a strip of inner tube tightly wrapped around it does the same ,more or less.
 
Depends on how much work you want to do and the final finish, but laminating either bendy ply or veneers around a former, preferably vacuum bagging would be the professional way. This technique was covered in detail in a PBO article fairly recently - perhaps a search on the reprints section will find it or a call to the office.

Alternatively Robbins Timber actually have pre moulded profiles of exactly that size which they will veneer for you.
 
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pandos said:
You could use bendy ply available in b and q . laminated it holds its shape. When you get the shpe you require then cover the piece with veneer or maybe laminate on a piece of 1/8 inch faced ply.
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No need to laminate another layer, just paint the back with resin (and glass if you want) and it will hold its shape. Ply face can be stained and varnished to match existing woodwork.
 
prv said:
I'd hand-sand the facets into a curve with 80-grit paper on a foam block.
Pete
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You could find something with an appropriate diameter - a piece of plumbing pipe for instance - to use instead of a flat foam block. Pad out with a bit of closed cell foam (like Karrimats - camping "mattresses"). That's how I faired all the constant-radius bits on my hull.
 
This year I made a new hatch by glue laminating 3 layers of ply. I only needed a curve of 80mm over 900mm. The first attempt using 5mm ply failed as I got a hairline crack on the outer surface. Attempt two using 3mm ply was a success.

I've just been out to my workshop to do some rough tests as I've got lots of ply offcuts. I could form a 90 degree bend in an 800mm length of 3mm ply. With a shorter length I started to hear splintering.

The other issue with this method is spring back. Once you remove it from the former it will spring back by a surprising amount, enough that you need to take it into account, so you need to over bend. It is not easy to know by how much, it can allegedly be calculated but I only found numbers for solid woods. It is also an all or nothing approach, in that you spend time cutting the wood, glueing up etc, but only when you release it from the former do you find out how it went.

I would follow prv's method, faceted version of hardwood strips glued together, then planed and sanded to a curve. The benefit of this method is the control you have over each stage. They can be cut and glued one at a time, so you have chance to correct for an earlier error.
 
30boat said:
I would get a length of PVC tube of the correct radius or slightly less and laminate a few veneers around it with epoxy or polyurethane glue.Since I have a vacuum pump I'd vacuum bag it but a strip of inner tube tightly wrapped around it does the same ,more or less.
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That's what I do using contact adhesive for the veneer. Makes a very easy job and looks highly professional. Cost is also minimal!
 
It is easy enough to do in the variety of ways explained here. I would suggest using solid timber as it is far harder to make a neat job of veneering edges on a curved profile. If you do want to veneer then use a trim bit on a router with a guide bearing.

The two ways I would favour are either layering up of thin strips of solid wood round a form or the faceted method with blocks angled and then trimmed to shape. The first method will be marginally stronger as the grain will follow the curve fully.
 
PCUK said:
We never have any problems veneering on curves. Depends if want the advice of people who've done it or those with nothing more than opinions.
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I am not sure if you mean veneering or laminating. Veneering requires skill even on flat surfaces to reduce the appearance of a seam between the edge banding and surface veneer. It can be done and professionals use an edge banding tool or a router with trim bit.

Laminating is best done with thin 'veneers' of solid wood thus avoiding the requirement for edge banding as the finished laminate, if done properly, is hardly distinguishable from a single curve of solid timber. Clamping can be done over a simple jig or with vacuum bagging.

Do you think you are the only one who has tried these techniques?
 
PCUK said:
We never have any problems veneering on curves. Depends if want the advice of people who've done it or those with nothing more than opinions.
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Having done it various ways, I find kerf bending the easiest. Can be done on a table/bench saw or hand held circular saw and if the cuts are well doused with pu expanding glue is very strong without additional layers/laminations. Typical example here -

http://stusshed.com/2007/07/17/kerfing-bending-wood-on-the-tablesaw/
 
pmagowan said:
I am not sure if you mean veneering or laminating. Veneering requires skill even on flat surfaces to reduce the appearance of a seam between the edge banding and surface veneer. It can be done and professionals use an edge banding tool or a router with trim bit.

Laminating is best done with thin 'veneers' of solid wood thus avoiding the requirement for edge banding as the finished laminate, if done properly, is hardly distinguishable from a single curve of solid timber. Clamping can be done over a simple jig or with vacuum bagging.

Do you think you are the only one who has tried these techniques?
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You can do it with either veneers or ply, or even with foam core and epoxy glass with an outer veneer. As i understand it the OP wants it to finish off a boxed in tank which presumably will have flat panels and the curve is to join the two at 90 degrees. Finishing the edges is therefore not relevant as they will but up to the panels. as you won't see the inside, I would be tempted to lay up glass epoxy on a piece of plastic 4" pipe and glue a veneer on the external surface to blend in with the panels. Rebate the edges of the panels to take the moulding. Cheap and easy.
 
Tranona said:
You can do it with either veneers or ply, or even with foam core and epoxy glass with an outer veneer. As i understand it the OP wants it to finish off a boxed in tank which presumably will have flat panels and the curve is to join the two at 90 degrees. Finishing the edges is therefore not relevant as they will but up to the panels. as you won't see the inside, I would be tempted to lay up glass epoxy on a piece of plastic 4" pipe and glue a veneer on the external surface to blend in with the panels. Rebate the edges of the panels to take the moulding. Cheap and easy.
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Yes, you can laminate either with solid 'veneers' or ply (with a decorative veneer on top). My suggestion was to use solid as it avoids the 'seam' where one surface meets the other. Obviously I don't know exactly what the OP intends but in my mind any 'box' always has vertical and horizontal surfaces which meet. At this junction is where solid timber is easier to 'blend' in since getting a neat edge on veneer where the corvers meet the top is more tricky unless you have tools such as I listed. With solid timber laminate you can simply sand until it matches with no risk of going through the surface decorative veneer. This is even more true if the edges come above in a 'fiddle' type arrangement.

If this is not a concern then there is no reason to even use wood for the substrate and many people simply glue a plastic pipe in place and mould round it with the final veneer. The only thing to think about in that scenario is the glue adhesion to the plastic as some glues don't like it especially if not roughed up with sand paper. It makes the origninal build easier as you build square to start with.
 
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Unless you want a continual surface finish on both the curve and the flat then it is common to have the vertical curved part as a discrete piece - very common in production building. The continuously veneered type was well covered in the PBO article on the subject.

The technique the OP chooses will depend very much on what visual effect he wants to achieve and the amount of effort (and skill!) he is prepared to invest in the job.
 
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