Official Luthiers Forum!

The newest Luthier Tips du Jour instructional video is on Youtube. The topic is the new and improved LMI side bender. Subtitles are available in both English and Portuguese and you can translate them into any other language by using the CC option on Youtube.
As always, comments and discussion are welcome.
Enjoy!

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Looks high speed, low drag.

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http://www.booneguitars.com
https://www.facebook.com/pages/Stephen-Boone-guitar-builder/488208541257210

Wow.

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Ken

What about cutaways????

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MK5acoustics.com

It is my understanding that cutaway forms will also be available.

Very cool! When is it available and how much$

Their new catalogue should be coming out any day now and it is featured in there. I am not sure of the price but I heard it would be about what the old one costs.

I like the low profile, cantilevered waist caul, and the floating waist caul shoes. The negatives seem to outweigh the benefits, such as being bound to LMI's forms and thus not being able to use proprietary shapes for the body. It also seems to add a bit of time to the bending process. I saw a similar amount of springback in the final product.

Somebody's been using their noggin! Very thoughtful innovations.

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Expectation is the source of all misery; comparison the thief of joy.
http://redrivercanoe.ca/

Regarding the proprietary aspect of the molds, that's a none issue for me. If we are able to build guitars, we should be able to build our own molds that would fit with the rest of the LMII bender gears.

And regarding the bending time and the amount of springback, I don't think it has so much to do with the bender itself, more with how Robbie is using it (with all due respect, Robbie). With the same blanket temparature, I bend faster than that on my own bender. There is no reason I couldn't work as fast with the LMII bender. And I tryed the "15 minutes with the bender ON after bending" technique and I didn't get satisfactory results. I prefer cycling through 2 additional 5 minutes with the bender ON, spaced with 5 minutes with the bender OFF. But that's just me.

The reason I bow to the designers of this bender is for the "rolers" than apply constant pressure exactly on the portion of the side that gets bent. This is going to be especially efficient for cutaways.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Overall, this new Charles Fox cantilever bender idea looks like a winner. However, I see an issue with the new "rollers" idea in the LMI implementation. Check the video out at around 5:50 to 6:03 and you can see that as the roller is turned and then paused, the tension on the upper spring steel slat relaxes to the point that the bending slat flexs up away from the wood being bent. This will very likely allow ripples to form in the bent side. It looks like the roller idea is okay if the roller is rolled continuously (without stopping to check anything) until it reaches the top/bottom of the guitar side (where the side is "vertical"), but that any time you stop rolling, it appears to relax the tension and the slat flexs up and away from the wood.

With my "old style" Fox bender, with spring tensioned upper/lower bout bending assisters, I see no such relaxation of the slat tension as I bend the upper/lower bouts.

Perhaps what is needed are some slat end tensioning springs?

Thoughts?

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

No disrespect meant to Charles Fox, but this bender is based more on the industry cantilever (Taylor) bending design than anything else. It is my understanding that Charles has a cantilevered bender, but we had not seen it (and still haven’t) when we began the design of this bender.

The “slat-float” in the slat stack is caused by over-tensioning the springs on the rollers. Robbie was using a prototype in this video and the markings on the machine indicating how far to drive the springs were not as clear as they are on the current machine. We have added some text to the video that ships with the machine that clarifies this. If the springs are over-tensioned “slat-float” can occur, but proper tensioning of the springs corrects the problem. We include detailed instructions with the bender. We continue to use these benders in our shop and all the sides coming off of them have come out great even with the most difficult to bend woods.

Spring back is an unavoidable issue unless one over bends their sides. The answer to this, in our opinion, is get your sides into a mold ASAP after bending.

We have a pdf that gives all pertinent dimensions for creating ones own bending mold which should be on our website soon. We are also selling blank shoes for this purpose.

There is more information on our website here: http://www.lmii.com/CartTwo/thirdproduc ... ng+Machine.

Natalie

Good explaination Natalie! I didn't know LMI was already using them in production....that instills great confidence
I'm going to take a look at it next time I'm up there at LMI and more than likely I'm going to buy one

I can see that if the compression force on the rollers was too high, then some slat float could easily occur. I guess it's like a lot of our tools/jigs in that you have to use it for several guitars in order to get a feel for it so that it produces good results every time.

Charles presented his cantalever bending machine at the last GAL convention a couple years back. I had no idea you guys were working on a similar machine at that time, so naturally I assumed it was based on the machine I saw at GAL. As they say, "great minds think alike!".

Cheers,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"