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Bending slats: choices, choices. What is your take on it?
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Author:  Ed Haney [ Tue May 31, 2011 8:46 pm ]
Post subject:  Bending slats: choices, choices. What is your take on it?
I am getting ready to build a Doolin style bender with temperature control. I didn't realize that there are more choices for what slats to use than components for building a temperature control systems (yeah, I'm exaggerating, but not much).

Doolin uses .007" spring steel on the bottom and .017" perforated stainless for the top. He runs hot water over his sides before bending. He says the perforation is important. Yet several others have built his design and report that it works fine without the perforated steel.

Some say using spring steel for both the top and bottom is best. Others use stainless. Many with various thicknesses. LMI is using 2 spring steel slats each .008" plus a .020" small 5.75x5.75 spring steel slat at the waist only.

I am leaning towards 2 spring steel slats at .008", but have not made up my mind. Of course other slats could be substituted later.

What kind of slats are you using, what thickness, and what your take on it?
Author:  Terence Kennedy [ Tue May 31, 2011 9:03 pm ]
Post subject:  Re: Bending slats: choices, choices. What is your take on it?
I use blue tempered shim stock-spring steel at around .008-.010. I use the lighter for cutaways.
Wrap with tin foil and use brown wrapping paper to cover the sides. Moisten as needed.
I've used two blankets after seeing John Mayes' video a few years ago. That combination has worked very well for me. Lately I've used another .007 or 8 slat over the top blanket to protect it.
Author:  amcardon [ Wed Jun 01, 2011 12:21 am ]
Post subject:  Re: Bending slats: choices, choices. What is your take on it?
Either spring steel or the stainless will work fine, stainless isn't going to rust on you like the spring steel will. Correct me if I'm wrong but I'm perry sure John gets his from Lyon Industries and had them at a very good price, maybe he will chime in and sau why he stocks both and what he'd recommends...
Author:  Robbie_McD [ Wed Jun 01, 2011 6:53 am ]
Post subject:  Re: Bending slats: choices, choices. What is your take on it?
^^^Yup - John's spring steel slats are the goods!
Best to provide a barrier between wood and slat - dampened craft paper or parchment paper....
Author:  Ed Haney [ Wed Jun 01, 2011 4:53 pm ]
Post subject:  Re: Bending slats: choices, choices. What is your take on it?
verhoevenc wrote:
I use the same method as Todd... but since my shapes have some REALLY tight bends I don't use the spring steel slats that most lutherie supplies sell. They're so tight they permanently dent/bend the spring steel the first time round. I use aluminum flashing and have been very happy so far.
Chris


Thanks for the feedback, Chirs.

I am confused (common state for me), seems like aluminum flashing would "remember" its shape (dent/bend) worse than spring steel. Or maybe it does and you just throw it away after each bend? What am I missing here? What mil thicknes is the aluminum?

Ed
Author:  Brad Way [ Wed Jun 01, 2011 8:51 pm ]
Post subject:  Re: Bending slats: choices, choices. What is your take on it?
verhoevenc wrote:
I use the same method as Todd... but since my shapes have some REALLY tight bends I don't use the spring steel slats that most lutherie supplies sell. They're so tight they permanently dent/bend the spring steel the first time round. I use aluminum flashing and have been very happy so far.
Chris


I have used spring steel, stainless, but finially started using aluminum flashing. It is cheap, doesn't rust, and comes in 6" wide rolls at the local Home Depot.
Author:  Pat Hawley [ Wed Jun 01, 2011 8:51 pm ]
Post subject:  Re: Bending slats: choices, choices. What is your take on it?
Spring steel. I feel the support is important when doing cutaways.

Pat
Author:  Ed Haney [ Thu Jun 02, 2011 3:06 pm ]
Post subject:  Re: Bending slats: choices, choices. What is your take on it?
Pat Hawley wrote:
Spring steel. I feel the support is important when doing cutaways.

Pat


Few people have mentioned their slat thickness and how one thickness compares (pros and cons) to another.

John Hall reports that his Blues Creek slats are currently (always?) 0.015" thick for both the spring steel and the tempered stainless. His tempered stainless has some memory (a negative) while his spring steel does not.

John's .015" slats are 87% thicker than LMI's standard .008" and 114% thicker than Doolin's .007. That is a big difference in thickness, but is it a big difference in using characteristics? Does anyone have any experience to speak to the pros and cons of the various thicknesses?

Maybe all these choices work fine and it does not matter very much what thickness or steel or aluminum type one uses??

It is a mystery to me.
Author:  matt jacobs [ Thu Jun 02, 2011 6:14 pm ]
Post subject:  Re: Bending slats: choices, choices. What is your take on it?
Hi Ed,
.015" is fine for non-cutaway guitars, but adds a lot of "resistance" on cutaways. I prefer thinner slats.
Author:  bluescreek [ Fri Jun 03, 2011 5:06 am ]
Post subject:  Re: Bending slats: choices, choices. What is your take on it?
The slats do a few things . Depending on what style of bend pattern you are using. If you are using the fox style pattern you need the slats to add support for the wood as it bends. Thinner slats won't do it nor will aluminum. If you have a solid pattern then the thinner will. The memory bend can actually help on discreet benders as the Doolin and other modified bending machines.
Not all slat material is the same . There are different alloys. Shim stock isn't tempered . While my stainless is , it isn't as hard as spring steel . Granted you have to look at your need. If you are building 1 guitar, you use what gets you through. If you plan on making multiples you need something that is going to work long term.
Water chemistry can also add to the mix . Chlorine can do funny things to some woods. Spring steel with a high iron content needs a barrier so it won't stain your wood plus it rusts . So you see there is no one perfect material. I have been using the same stainless slats for about 8 years . The minor ripple is insignificant and under tension they go away . The only modification to my basic bending process I have done is to use kraft paper between slats and resinous woods. Often the heat will bring out these resins and they can be difficult to remove from the slats. East Indian Rosewood is the main one for this.
Hope this info helps .
On Cutaways I use the standard stuff without a problem , but then I have bent well over 200 sets a year and I have a good repeatable process.
Author:  Ed Haney [ Fri Jun 03, 2011 9:37 am ]
Post subject:  Re: Bending slats: choices, choices. What is your take on it?
Thanks John, Matt, and all.

Some of the aspects are clearing up for me. The Fox style bender with just two outside molds which are too wide for the wood to see offers little support (requiring more support from the slats thereby favoring thicker slats). Whereas the Doolin style bender uses solid molds supporting the wood completely (requiring less support from slats thereby allowing slats to be thinner).

The LMI bender, which uses thin .008" slats offers support somewhere between a Doolin style and Fox style. The LMI has 4 molds, 2 of which are under the wood and 2 outside the wood like the Fox. While the LMI offers more support than the Fox and less support than the Doolin, but it offers enough additional support to work well with the thin slats.

The thin blue tempered spring steel (not just shim stock) appears to have the advantages of no memory and ease of use with cutaways. I wonder how tempered 302 or 316 stainless at about .007" thickness would work on cutaways used on solid fully support Doolin style molds?

One thing that is clear to me is that there is a broad range of what works to bend sides. This includes temperatures (275F to 385F), side support or lack of it, "cycle time" or no cycles, water or no water, additives or no additives. I guess I (we) are lucky that that so many approaches work.

Ed
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