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Armrest Construction - Veneer First or Purfling First?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=36463		 Page 1 of 1
Author:  Pat Hawley [ Sat May 12, 2012 12:49 pm ]
Post subject:  Armrest Construction - Veneer First or Purfling First?
Hi all,

I want to try putting an armrest in my next guitar. My review of previous posts on the topic suggest that there are those that install the purflings that go around the armrest area first then file/sand down to create the armrest surface to which a veneer is then glued. A second approach I see is to first file/sand down to create the armrest area, install the veneer and then route purfling channels and install the purfling around it (the veneer). I hope this is clear but it probably isn't unless you are already familiar with both approaches.

I'd like peoples opinions on what is the best method. I'm leaning towards the second approach because in the first, I'm not understanding how the veneer doesn't end up being higher than the purfling. That is, the edges of the veneer would be showing above the purfling, as the would not be against the sides of the purfling (or do people just not worry about this since the veneer is very thin?).

Thanks,
Pat
Author:  TonyKarol [ Sun May 13, 2012 1:16 pm ]
Post subject:  Re: Armrest Construction - Veneer First or Purfling First?
I cant say there is a best method, but I use hte purf lines first then veneer. I must add to this though that I also add binding to the purf lines, on both the top and side of the guitar body, before I veneer usually using something thinned down in the shop to about 50 thou. My reasoning for this is when you sand the veneer down and round it over to meet the purfling, you have the same wood underneath it if and when you go thru at the edges - which you will as there is a transition area and this works well as a seemless look, especially on dark woods.

My current fave is to use african blackwood as the binding and veneer. I do have a student about to use ziricote, which should also work well - dark is better, macassar or black ebony would also be good. In the past, I have also used carmelized (lightly roasted) maple and regular curly maple. These are tougher as you must have the veneer surface really flat before attempting to glue the veneer down, otherwise you may have gaps.
Author:  Pat Hawley [ Sun May 13, 2012 8:42 pm ]
Post subject:  Re: Armrest Construction - Veneer First or Purfling First?
Thanks Tony. That sounds tricky to me. Then again, so does the second method where I'd have to route a channel that exactly follows the joint between the veneer and the top for the top purf and the joint between the veneer and the side for the side purf.

I was thinking of a third method for a very small armrest in, say, ebony where I just route deeper for a double (or perhaps triple) deep binding and putting two (or three) layers of binding in that area. I think if it was in dark ebony, the layers of binding could be pretty much invisible. Then I could just file/sand the armrest into the wide binding area and be done without needing a veneer at all. Has anyone done this approach?

Pat

PS Tony, if you have a picture handy of one of your finished armrests, could you post it? Thanks.
Author:  TonyKarol [ Mon May 14, 2012 7:03 am ]
Post subject:  Re: Armrest Construction - Veneer First or Purfling First?
I do your third approach as well .. I call it a mini armrest (or ribrest). You still put a block inside, albeit smaller in size. You still need to route a new channel for your purfling that follows the inside curve of your armrest on the top. Using the same template, you then you route a full depth channel into which you put 2 or 3 small strips of binding, leaving them overhang the original standard binding ledge at the ends. Then reroute your outer binding ledge, and bind as normal. Now carve your mini armrest into the wider binding area.

Sorry, went looking for a good pic of either and I cant find one ...
Author:  Chris Ensor [ Mon May 14, 2012 8:17 am ]
Post subject:  Re: Armrest Construction - Veneer First or Purfling First?
I route for the binding and purfling. Then I use a template to route the purfling in the armrest area. I glue in the binding and purfling. Then I VERY CAREFULLY carve the armrest area up to the purfling. Cursing is allowed here if you hit the purfling. laughing6-hehe Then glue on the laminate, flush it with the top and sides and vuwla- you're done. I should mention that I final sand the entire guitar before doing the laminate and then carefully flush it up so that I am not sanding too deep and exposing any gaps. Those aren't any fun.
Author:  Pat Hawley [ Mon May 14, 2012 8:41 am ]
Post subject:  Re: Armrest Construction - Veneer First or Purfling First?
Thanks guys. Tell me if you think this sounds dumb as an approach for the third method:

Instead of using a template, I was going to use the same binding jig (which makes use of the LMI bit and bearing set) as I do when doing regular bindings. For the armrest area, I was intending to use a smaller bearing so the router went deeper. So I would do both the ledge for the purfling and the bindings sort of the same as doing regular bindings, just deeper. Here's the idea that's either good or bad: To make a smooth transition at the ends of the armrest, would make small "ramps" for the router bit bearing to follow that I would stick to sides with two sided tape. That way, the router would come off the top following a path determined by the shape of the ramps.

Pat
Author:  Chris Ensor [ Mon May 14, 2012 9:54 am ]
Post subject:  Re: Armrest Construction - Veneer First or Purfling First?
I like my armrest to be a sweeping arc. I guess you could use the ramp method. But you would need long ramp to make a nice arc other wise it will look a little funny (at least I think so). I would definetly practice on some scrap first before trying it on a guitar.
Author:  TonyKarol [ Mon May 14, 2012 1:21 pm ]
Post subject:  Re: Armrest Construction - Veneer First or Purfling First?
In theory, the idea could work .. but as Chris says, the ramps need to be long .. and more importantly, very thinly and evenly tapered . You want the transition to be smooth and almost seemless if possible.
I think its more easily done using a plexi template, clamped to the guitar's top, and a lam trimmer with guide collars. In fact, you really only need one - to get the right offset from the template after routing the purf ledge, simply use whatever purf design you are planning and put that against the template to give the exact offset - thats how I do it. If you then plan on having the armrest tape some into the side as well, I use a piece of flexible ply with a slight curve sanded into it and tape that to the guitar side, then route the new side binding ledge.
Author:  Pat Hawley [ Mon May 14, 2012 4:26 pm ]
Post subject:  Re: Armrest Construction - Veneer First or Purfling First?
I drew this out for a very small arm rest - one that only uses a double thickness of binding. If I go about 4 mm into the sound board and 4 mm down the side, that gives me an armrest width of about 6 mm. Not much but way better than the corner you have with no armrest. Also, one of the guitars I want to try this on will be a classical and I have a feeling that to be accepted in the classical guitar community, it should intrude on the sound board as little as possible.

With an armrest that small, the transition is only the thickness of one binding width i.e. about 2 mm. From my drawing, it seems I can get a reasonably smooth transition using about 1 inch side ramps. So for the ramps I would just need wedge of wood that go from 0 to 2 mm thick over the course of an inch. Of course, the proof would be a trial run and I'll get a hunk of wood and give it a go. I'll post some pictures.

Pat
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