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Bending Sides
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10117&t=21257		 Page 1 of 1
Author:  Hesh [ Sat Feb 28, 2009 9:50 am ]
Post subject:  Bending Sides
Perhaps the single most terrifying operation that we do as guitar builders is side bending. At least it used to be for me before I developed a system that provides me with consistently positive results.

With the help of other OLF members from their posts in the past couple of years I now have my own methodology that combines many of the ideas of others. Many thanks folks!

Please note that I will be posting many pictures in this tutorial and my apologies to those who have trouble downloading this thread. I have reduced my picture quality to hopefully make this a non-issue for all.

My bender is from John Hall at Blues Creek and it always provides me with excellent results. The only modification that I have made is more in my method then any thing else. As you will see from the following pictures I use a 3rd spring-loaded caul to firmly hold the widest area of the lower bout in place. This is completely optional and typically not necessary. I use the third caul because on some highly figured woods “cupping” can occur and in my experience the cupping was the worst in the area of the lower bout.

Today we are going to bend some highly figured Koa that I purchased from Volcano, an OLF sponsor. My sides were thickness sanded to a thickness of .085”.

Before we begin a word about the bending stack. By bending stack I am referring to the slats, blanket, wood, and the order that they are placed in.

My stack top to bottom looks like this:

Spring steel slat
Blanket
Stainless steel slat
Wood
Stainless steel slat

Again my stack is also optional and many others use a stack that is different from mine. Some folks only use two slats. Some have the blanket beneath the wood and some have the blanket directly in contact with the wood. It’s been said that there are a thousand ways to build a guitar and this is true with bending sides as well.

My results have been best with the wood firmly sandwiched between two stainless steel slats and the blanket above the top stainless slat with another spring steel slat on top of the blanket to help contain and direct the blanket’s heat downward.

Koa has a habit of tuning green when bent in a Fox style bender with metal slats and/or if using aluminum foil. We have discussed the reasons why here on the OLF prior and it probably has to do with the metals in the slats interacting with the Koa. Brock indicated that he has had very good results using craft paper, which is the brown, paper bag like paper that is used as packing material. Typically I wrap my wood in foil but today in an effort to not turn my Koa green I am trying Brock’s method and using craft paper.

Below is a picture of my bending set-up and you will notice the third caul with a block of wood wedged against the waist caul to hold it in place. Again this is typically not necessary, just the way I do things. The sides have already had the back edge profiled and the top edge is left straight to help with alignment in the bender.

Attachment:
DSCN2466.jpg


The first step for me after assembling all of the things that I am going to need is to lay out a side on a piece of craft paper big enough to wrap the side in. Also be sure to make a mark on your side where the waist will be. This mark will also be made on the out side of the craft paper. You will notice that the bender has a slot in the center of the waist area. The goal is to have the wood clamped in the bender with the wood’s waist mark centered in the slot on the bender and visually confirmed.

Attachment:
DSCN2470.jpg


Here is a better shot of the waist mark on the wood and on the craft paper. Once the wood is wrapped up the mark will be transferred to the outside, end of the package.

Attachment:
DSCN2471.jpg


I made a slight cut in the craft paper to help it wrap well over the side.

Attachment:
DSCN2472.jpg


Next I mist the Koa with distilled water. I don’t want it soaking wet, just lightly misted.

Attachment:
DSCN2473.jpg


Once both sides of the side have been misted I wrapped up the side and use masking tape to hold the package together.

Attachment:
DSCN2475.jpg


The next picture has many things to tell us. The stack containing the side and in the order described above is inserted in the bender. The waist caul is brought down in contact with the stack and helps to hold it all in place as well. My 3 spring loaded cauls are at the ready in the relaxed position. Spring clamps are used on the end of the stack to hold it together. It is important to have the stack held together so that the heat from the blanket transmits well throughout the entire stack. The blanket is plugged in and ready to be turned on.

Attachment:
DSCN2477.jpg


Here is a shot of the stack looking through the center slot in the bender. Note that the pencil mark that we made earlier denoting the waist area of the side is centered in the slot of the bender.

Attachment:
DSCN2476.jpg


To be continued...
Author:  Hesh [ Sat Feb 28, 2009 10:02 am ]
Post subject:  Re: Bending Sides
Welcome back! :)

And now the fun begins. Make sure that you are free of any potential distractions in as much as you will need to be at the bender for the next five minutes or so. Never leave a bender or blanket plugged in when you are not present………

This picture shows the timer and heat controller that came with my heating blanket from John Hall. I set the heating controller to “variable” and the heat control nearly all the way up in the “red” zone. I do not use a thermometer but it is recommended that you do. The various temps needed to bend various woods have been discussed in detail on the OLF prior.

I start my bend when the blanket timer indicates that it has been on for 2-3 minutes AND a wet finger results in a “sizzle” sound when I touch the top of the stack. In addition I look for steam which I do not always see and listen for a sizzling sound coming from the wood which I do not always hear either.

Attachment:
DSCN2478.jpg


I set the timer for 6 minutes but will not leave the blanket on that long with 3 – 4 minutes usually working fine for me.

Attachment:
DSCN2479.jpg


After approximately three minutes I begin the bend by bringing the waist caul down using the large screw and handle located on top of the bender. This is done slowly and you can feel if you are encountering any resistance. It will be a bit stiff but should not require any force. I bring the waist caul down on the stack until I have approximately ½” of travel left and stop. Since I am moving fast now I did not get a picture of this – sorry……

After the waist caul has been lowered nearly all the way the lower bout is next. Simply pull the caul slowly down over the lower bout keeping it in firm contact with the stack at all times. If it gets hung up working it back and forth will free it up. Once it is in place over the lowest part of the bending form I position my third caul over the center of the lower bout but again this is not necessary. Also this is when I usually unplug my blanket and no more than 4 minutes have passed that the blanket was on.

Attachment:
DSCN2481.jpg


Repeat the process for the upper bout and in both cases know that some force is needed to move the cauls. The springs have a great deal of tension and I typically pull the caul with one hand and use the other hand on the bender’s tower to keep it from being pulled off the bench.

Attachment:
DSCN2482.jpg


Now with both the upper and lower bout of the side bent I return to the waist caul and lower it the remaining ½”. This pulls every thing together.

Attachment:
DSCN2483.jpg


The most important thing to note in this picture is that the blanket is now unplugged. The bend has been completed, less than 5 minutes time has passed, and all is well.

Attachment:
DSCN2484.jpg


For informational purposes here is a shot of the 3rd caul in action. See how tightly it is holding the stack down over the widest part of the lower bout.

Attachment:
DSCN2486.jpg


Next I note the time with the intention of returning to the bender in one hour after the side has completely cooled down.

Attachment:
DSCN2485.jpg


To be continued...
Author:  Hesh [ Sat Feb 28, 2009 10:18 am ]
Post subject:  Re: Bending Sides
Approximately an hour later, it really does not matter how long so long as the side and the bender are now completely cool I return to the bender.

Attachment:
DSCN2488.jpg


Now with out doing anything other then plugging the blanket in again I cook the side for an additional 4 minutes. Again do not leave the area or become distracted while the blanket is on. After 4 minutes has passed and I can hear the sizzle when I place a wet finger on the stack I unplug the blanket and wait an additional couple of hours and overnight is even better.

Cooking the side twice helps to reduce the amount of spring back that the side will have when removed from the bender. Another way to say this is that it helps to set the bend.

Here is our Koa side still wrapped in craft paper. One of the things that I like about using craft paper is that the moisture from misting the side is permitted to escape the package and the side will be bone dry when I unwrap it.

Attachment:
DSCN2491.jpg


And here is our side now nicely bent. There was no cracking or crushing marks in the waist area and I am very pleased with the results. In addition the green stain that Koa is known to have after bending is completely absent.

Attachment:
DSCN2492.jpg


The side is placed immediately into the mold and clamped with spreaders into place. You can also see that the fit is very tight and is gapless in the mold.

Attachment:
DSCN2493.jpg


Attachment:
DSCN2494.jpg


Additional notes:

Please remember that you are making a “right” and a “left” side. It is all to easy to make two of the same sides and if you do usually the side can be flattened out and bent again.

Also, if you want to have a nice “book-matched” match of the two sides where they will meet at the butt wedge this is easy to accomplish as well. Just lay out both of your flat sides with the two straight edges (top edge) against each other and make the waist mark with a pencil in the same place on both sides.

So there you have it – this is how I bend my sides and it has worked out very well for me. There are many ways to bend sides and this is only one of these methods. As you learn to bend sides I am sure that you will develop your own methods for doing things as well.

As always I welcome discussion, tips, tricks, criticisms, what ever – the really important thing at least to me is that this thread is of value to folks.

Thanks for looking!
Author:  oli-lgw [ Sat Feb 28, 2009 11:28 am ]
Post subject:  Re: Bending Sides
Hesh, Thanks for the toot! well detailed and easy to follow [clap] [clap] [:Y:]
Author:  Chuck [ Sat Feb 28, 2009 12:22 pm ]
Post subject:  Re: Bending Sides
Thank you for the information and the pictures.
chuck
Author:  Randolph [ Sat Feb 28, 2009 2:07 pm ]
Post subject:  Re: Bending Sides
Hesh, thank you!! This couldn't have come at a better time bliss
Author:  Stephen Boone [ Sat Feb 28, 2009 6:43 pm ]
Post subject:  Re: Bending Sides
Thank you HESH!!!

My side bender from John Hall is supposed to get here TOMORROW! I will be putting this info to good use on my OLF-SJ very soon. I have to finish my flamenco build first.
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