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Very interesting!

Thank you.

I've watched the video and read the theory, but I don't understand how the waist area doesn't get 'unbent' when you move on to bending the upper bout. You remove the waist block, then bend the upper bout. Why doesn't the tension on the slats just 'straighten out' the waist??
I know it works, but I just don't understand why!

Thanks again.

John

John, I may be mistaken here, but I think he only removes the 'outer' waist blocks used to guide the cable, but the inner forms all stay in till the end.

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-Clint Beacock

Yes, as Clint mentions, the inside blocks are added in sequence as the bend progresses but the outer blocks are removed in sequence.
You might call it an additive process on the inside blocks and a subtractive process on the outside.
The air cylinders maintain constant tension on the sandwich during this process and it is this tension which supports the outer fibers of the wood to prevent them from seperation. This is very critical when tightly bending highly figured maple as the undulating grain has no continuity.
The frustrating thing when bending this type of maple to a tight cutaway, say 1" radius or less, is that two or three sets will bend "perfectly" with no tearing or faceting. Then the next set, bent with exactly the same settings and appearing no different figure-wise, will go "kersnap" as Anthony Zlahtic so eloquently described it.
This is why Fernando has spent so much time inventing this prototype bender and will be the first to tell you that it is not yet perfected. He does have plans for improvements to simplify the process. He has spent a great deal of time with drawings and the video to explain the process as he wants to pass it on to the luthiery community.
Nelson

Hi Fernando,

this is a very nice presentation of your side bender, indeed!
I agree with that comment in the very beginning of the video, that one first had to understand how it works to see what the bender really does.
I missed a little bit to have a quick look "inside" the bender when you put in the waist insert and upper bout insert. (I guess that is what John missed too). But well, I imagine how it is to bend the sides and film it at the same time...


Which ones exactly? I guess (but I'm not sure) you refer to screwing on and off the wire rope guides and bending inserts. When I watched it the first time, to me it also seemed to be quite a lot to do. But then I turned off the music and everything appeared to be much calmer
But in fact, I thought some flip-in-place-and bolt-on mechanism for the inserts and guide blocks could be subject to further development of this bender.

But in fact, I thought some flip-in-place-and bolt-on mechanism for the inserts and guide blocks could be subject to further development of this bender.
I believe that these are some of the improvements Fernando is working on.
http://www.guitarrasjaen.com/English%20Version/Bender.htm

Hello Everyone,

I thought folks may enjoy seeing my friend Mark's method of bending
sides. The sides being bent in the video are walnut. He has bent 100's
of side using this method successfully.

Cheers - Luc

http://luthiertube.com/video/453/side-bending

Interesting video, Luc!
I only wish that flamed maple could be bent that easily.
It can be rather cantankerous at best.
Nelson

Hi Nelson,

I agree, flame maple can be a real challenge.
Had one set taking every precaution possible just kept cracking.
Switch to another set....bent like butter.

Cheers - Luc

Fernando,
I must say that your approach to side bending is very interesting. I really like the concept you are using and many of the ideas you incorporated in to your design I believe help solve some of the problems with bending highly figured woods.

Some time ago I also designed a side bender that was a little different approach but also used a pnumatically tensioned slat type system. My design was sort of a cross between the Taylor side benders and a Doolin bender. Here is my design...

http://www.luthiersforum.com/forum/viewtopic.php?f=10102&t=15206&hilit=dry+bending

I tried to focus on bending consistancy, easy of bender use, and the ability to load and unload sides while the bender while hot. Overall I was happy with the project but if I were to build a second one there are some areas I would improve. I have thought about modifying my design to handle cut aways but have not taken on the challange yet....but I will.

I am sure that many of the challanges you faced with your bender were similar to mine and I would enjoy compairing thoughts and notes on this topic.

While building a better bender is a big project it is an excellent was to learn the process of bending.

Keep up the creative work.

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Brad
Avon, OH

Brad:

I saw your machine when I was searching for information on side benders. It is really impressive, and it may be the absolute best when it comes to bending non-cutaways. What I cannot see is how to modify it for bending cutaways.

It was the same for me with the benders at Taylor guitars. The videos that show them don't show the bending of the cutaway. The only reference that I had was an article in Wood & Steel, the Taylor magazine:

http://www.taylorguitars.com/news/commu ... l_2004.pdf

If you read (page 27) they talk about the cutaway bender. It says that their earlier attempts at bending a Venetian cutaway were bending "the arm" back unless the machine was made using extremely strong construction. I guess that "the arm" was a device similar to their waist bender. The most intriguing aspect comes later, when they say that electromagnets were the solution to the cutaway bending. It is a pity that there are no photos, but the method must work very well, as the Venetian cutaways that I have seen in Taylor guitars are great.

Hi Fernando,

As far a I understand, talking of "it was actually bending the arm back" they mean that the final (concave part of the) bend of the cutaway would reverse part of the already bent convex part (of the shoulder / upper bout), or at least affect the straight part of the cutaway.



I haven't seen the Taylor bender but guess that the electromagnet (as a part of thge cutaway insert) would just clamp the side to the inner form of of the bender, instead of bolting the cutaway insert in place. They didn't like the "mechanikel things - latches, things like that" because they are "maintenance items that'll get clogged or need to be lubricated or fixed".

I took one of your drawings to modify it in order to explain how I imagine the electromagnet cutaway part of the Taylor bender could work:
A) Lower bout, waist and shoulder already bent
B) Cutaway insert clamped on with an electromagnet
C) Completing the cutaway bend

Fernado,

Thanks for attaching the Taylor article. It is always interesting to understand how Taylor arrived at their final design. There are many concepts in their design that I think are perfect. Last year I was in Califonia and stopped by Taylor for the factory tour. I am kicking myself for not taking a closer look for their cutway bender. When we were there they were done bending for the day so there wasn't too much to see in the bending department.

As for how to use my bender to bend cutaways....Markus is one step ahead of me! If you look at his sketch how the Taylor cutaway bender works (from his understanding) I was thinking of using a similar design for my bender to bend cutaways. I never really considered using an electromagnet but this would be a great way to clamp. I would probably also add a 4th hindging point to my bender to bend the last part of the cut away. I found with my bender that the farther the center point of the arm swing is off from the tangency point of the bending curve then the more force is required to swing the arm. I do not believe I could make the last part of the cutway bend with my bender as is since the force to swing the arm would be excessive. This may also have been the issue with the Taylor bender. Since your bender doesn't have hindge points and you don't have this issue. (good thinking)

You have many good concepts in your bender. Now that you have it working and have tested the design what things do you plan to improve/change?

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Brad
Avon, OH

I have been exchanging emails with Nelson Palen since I explained here how this machine works. In fact, if it hadn't been for him I doubt that I had done the video. We've been talking a lot about improvements; the following list contains the most important things, some of which have been proposed by Nelson himself:

- The external blocks can be set into recesses in the chassis, perhaps using a simple wing nut or nothing at all.

- Currently I am using wood (walnut) for the external blocks, but it has a lot of friction and stiction. You can feel the difference between the tension in the rope close to the pneumatic cylinders and at the bridge attachment. Nelson proposes using UHMW (he has experience with this material) as a tough, easily machinable, wear resistant, low friction alternative. This is applicable also to all the places where the wire rope changes direction (end of the bridge and wire rope guides close to the cylinders).

- The wire rope exerts a lot of pressure on the wooden external blocks, marking them. The rope then gets into those marks with the result that the friction increases. Replacing the wire rope for metal straps would lower the pressure significantly. This is also a great suggestion from Nelson.

- Currently, heating a surface for bending it will also heat the already bent areas. Independent heaters would allow extremely precise bending "recipes", heating each surface as needed. This would make the machine more complex, so the benefit should be weighed carefully.

- The internal walls of the machine must be coated with Formica or some other water-resistant material. If you watch the video closely, you will see that the steam has damaged the MDF walls.

- The current alignment adjustments are not enough. I use a single point for this at the bottom side of the machine, but this must be improved and there must be a second adjustment at the bridge.

- The internal blocks should be built with some overbend to prevent springback.

- There is a small distortion when pressure is applied. This does not cause problems for the non-cutaway sides, but the cutaway sides come a little bit smaller than they should be. It could be fixed just by making tougher chassis and internal blocks. A simpler solution could be to make the internal blocks a little bigger than necessary. Or, as Nelson suggests, making the whole machine narrower. This is not easy for me, as my slats and blanket are all 6" wide. If there was some source for narrower slats and blankets, that would be great...

- The bridge can be built using aluminum extrusion to save weight and to simplify its construction. This is another great suggestion from Nelson.

- The supporting bars that keep the bridge balanced between operations are not very elegant. A better simpler alternative could be to use sliding weights.

Brad and Fernando, you guys amaze me with your problem solving and construction ability.
Fernando, I appreciate your giving credit to my little ideas here and there.
They are minute, however, in comparision to the concept you have developed.
Keep up the good work, guys! Your sharing with the rest of us is appreciated.
Nelson

Sounds like you (and Nelson) have lots of good ideas. Here are a few thoughts to add to the list.



Have you considered using spring loaded locator pins?



Great idea Nelson about using UHMW. You may also want to conder replacing the steel cable with braided nylon rope (Spectra). This is the same rope that is used for many boating related activities. I would check out a sailing shop but you will find that is VERY strong, comes in many different sizes, and can easily be tied and would be low friction against UHMW.



Metal straps....also a great idea.



One of the features of the Taylor benders use is to only heat when you are actually bending. I found this to be very important especially if bending dry. Heating the wood when not being bending only drys it out. Or you need to add more moisture to compensate the extra heat which tends to cup or stain the wood.

Cool stuff...keep up the good work.

Nelson..thanks for the kind words.

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Brad
Avon, OH