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How do you get those tight bends on your Venetian cutaways?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=26556		 Page 1 of 1
Author:  Rick Cowan [ Mon Mar 15, 2010 11:51 am ]
Post subject:  How do you get those tight bends on your Venetian cutaways?
I really like the look of the venetian cutaway with a tight bend on the horn. Taylors seem to have them and I have seen some from several of the OLF members. Putting Taylor aside (who has a gazillion $s to invest in hydrolic this-and-thats and robotic outfits capable of unheard of lbs/sq. in.) how do you folks accomplish those tight bends and returns on your cutaways with your bending fixtures? Do you thin your sides more in this area? Do you have any particular apparatus you use attached to your fox-type bender to assist ? Or maybe not (as it appears to be the case with this fellow)



This is something that I have wondered for awhile but don't know enough about the bending procedure to pull it off.

Rick
Author:  JohnAbercrombie [ Mon Mar 15, 2010 12:06 pm ]
Post subject:  Re: How do you get those tight bends on your Venetian cutaways?
Rick-
I use laminated sides on pretty well all my guitar projects now, and that makes bending easy. The sides are very strong (split-resistant) and rigid as well.
Though not what I'd call a 'tight' , my recent archtop project had a cutaway, and it was pretty easy bending with just a heat blanket and a few simple cauls (with aluminum flashing slats) over a form-using mostly hand pressure. Those sides were actually 'one piece', so all the bends around the head area flowed from one to the next. It was surprisingly easy- bent all three lams at the same time.
Black (domestic) cherry and yellow cedar for the mid-layer.
Not the answer to your question, but one solution that 'works for me'.
Cheers
John
Author:  SteveSmith [ Mon Mar 15, 2010 12:32 pm ]
Post subject:  Re: How do you get those tight bends on your Venetian cutaways?
I've only done one but I just bent it on my Ibex bending pipe.
Author:  Rick Cowan [ Mon Mar 15, 2010 12:44 pm ]
Post subject:  Re: How do you get those tight bends on your Venetian cutaways?
Hi John,

Thanks. I'm curious, what thickness is each layer (.030" +/- ???) and how do you ensure there are not any air pockets when laminating the sides?

Rick
Author:  JohnAbercrombie [ Mon Mar 15, 2010 1:00 pm ]
Post subject:  Re: How do you get those tight bends on your Venetian cutaways?
Rick Cowan wrote:
Hi John,

Thanks. I'm curious, what thickness is each layer (.030" +/- ???) and how do you ensure there are not any air pockets when laminating the sides?

Rick


Rick-
I like to make the lams on the 'thick' side to minimize cupping and rippling problems, but that's probably not necessary. Mostly in the .035-.045" range....
I vacuum bag the lams and use epoxy for bonding- if there are any 'pockets' they are full of epoxy,not air.

Cheers
John
PS- the pump is a JB 'Eliminator' pump - some similar JB surplus (new) pumps were selling on eBay for under $30 a week or so ago.
Author:  JohnAbercrombie [ Mon Mar 15, 2010 3:06 pm ]
Post subject:  Re: How do you get those tight bends on your Venetian cutaways?
Todd Stock wrote:
I bend them on the Fox or on an iron...down to 1/2" radius is doable in most woods.

I'm very impressed! [clap] [clap]
1" diameter half-circles is really tight.
Which woods?
And at what thickness?
Author:  Rob Warren [ Mon Mar 15, 2010 4:53 pm ]
Post subject:  Re: How do you get those tight bends on your Venetian cutaways?
I've done 2, Sapele and zebrawood at 1.5" on my pipe/torch. I used a 1.5" pipe and thinned the sides to .080" in the cutaway and I made sure to use a steel backer slat...
Author:  Ti-Roux [ Mon Mar 15, 2010 9:01 pm ]
Post subject:  Re: How do you get those tight bends on your Venetian cutaways?
The secret is in the cigarette.
Author:  Rick Cowan [ Mon Mar 15, 2010 9:55 pm ]
Post subject:  Re: How do you get those tight bends on your Venetian cutaways?
Does this mean I must take up smoking?
Author:  Ricardo [ Tue Mar 16, 2010 11:14 am ]
Post subject:  Re: How do you get those tight bends on your Venetian cutaways?
John, who's your source for the veneers? I like your technique.
Author:  JohnAbercrombie [ Tue Mar 16, 2010 11:53 am ]
Post subject:  Re: How do you get those tight bends on your Venetian cutaways?
Ricardo wrote:
John, who's your source for the veneers? I like your technique.

Rich-
I've got a pretty good bandsaw (though side-width stuff is not a big challenge even for a small bandsaw) and I put the sides through a thickness sander to bring them down to thickness. (Very even grained stuff can be machine thickness planed a bit, but not to the thickness of a guitar side.) Lately I've been using a plywood 'carrier' board with (roll-type PSA) sandpaper stuck to one side, which helps with consistency when sanding thinner stuff.

I've been using mostly lumberyard yellow cedar for inner lams, though I do have a bunch of 2nd and 3rd grade IRW side stock from Allied to use some day if necessary. I dislike wasting a lot of the stock for the outer sides, but sometimes there's not a lot of alternative.

Laminating sides is quite a bit of extra work, but you do get around a lot of the difficulty of bending without making the sides so thin they are fragile. I know some excellent builders add side reinforcements to laminated sides, I haven't done that- so far. Oh, and with laminated sides, cutting a sound port as an afterthought is pretty straightforward.
Reading Bogdanovich (Classical guitar) prompted me to get going on the laminated sides idea.

Having said all that, there's no reason not to bend sides in the traditional way, using some techniques from Todd Stock and others (thinner, backing slats, etc.) to help with the tighter bends.
Cheers
John
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