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Bending Koa
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=4575		 Page 1 of 1
Author:  Andy Zimmerman [ Tue Jan 17, 2006 3:40 am ]
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Hi
I am about to bend a set of Koa in one of John's benders.
Any tricks to bending high flame Koa? Speed temp wetness etc?
I have the stainless steel slats and the heating blanket.
Thanks
Andy
Author:  Michael Dale Payne [ Tue Jan 17, 2006 3:57 am ]
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Wet and wrap in foil or craft paper, preheat to 270, bend 1/8 of waist bend, bend lower bout at 300, then upper bout at 300-310 then finish waist bend. This should take about 8 min. start to finish. The koa may have a greenish stain it will sand and scrape clean with a little work. This may be cause by spring steel slats reacting with resin in the wood and seems for me to be worse in the waist, but was not a big issue.MichaelP38734.4989583333
Author:  Brock Poling [ Tue Jan 17, 2006 5:32 am ]
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For whatever reason, I notice that when I use craft paper I don't get the greening as much as when I use foil.

This is based on a small sample size for sure... but there may be some correlation.

Brock Poling38734.5645486111
Author:  PaulB [ Tue Jan 17, 2006 9:19 am ]
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I just bent some figured black acacia sides a few days ago, very similar to koa, actually I don't think you could tell the difference with this set.

The first side came out very green. I had wiped it down with a wet sponge then wrapped in foil. After it was bent I left it in the bender overnite then gave it another heat cycle in the morning, let it cool and unwrapped the foil. Green all over and a still a little damp in places.

The second side, I used a little less water and as soon as it cooled I took it out of the bender, unwrapped it, and put it back in the bender. It was also still damp in places so I gave it another heat cycle to dry it out. Much less green this time, only a little at the waist. It then occured to me that if the green didn't come off I'd have a set of sides that didn't match, Doh! Thankfully a search of the archives and a PM to Michael sorted it out.

I won't use foil again on either black acacia or koa, I'd try the craft paper instead. The greening seems to be more of a problem when there is residual moisture in contact with the wood and metal for a long period of time, so you'll want to make sure you get the sides dry quicky and don't leave them in the bender overnite.
Author:  Brock Poling [ Tue Jan 17, 2006 9:23 am ]
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Again, I find with craft paper I get very little "greening" and I always leave my sides in the bender over night.
Author:  TonyKarol [ Tue Jan 17, 2006 10:42 am ]
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after watching the factory friday on bending on Taylors website a few months back, I gave up spritzing sides all together. I almost never used any on curly or figured woods anyway, but I bent some dry a few weeks back and the greening was very minimal. here is still moisture in the wood without adding any spritz, and stuff has been bending fine. I use foil wrap inside spring steel slats with a 550w blanket. Full heat for about 3-4 minutes then crank down to about 90 volts and complete whatever isnt bent down.
Author:  Mike Mahar [ Tue Jan 17, 2006 11:20 pm ]
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I was bending some koa mandolin sides last night by hand. The koa seems to prefer very little water and tended to split when too wet. I'd use only the lightest spritz of water if I were using a bender on this wood.
Author:  Dickey [ Wed Jan 18, 2006 2:35 am ]
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It's amazing. I started building in 1999. The soak in water overnight, to soak in hot water ten minutes before bending, to no water at all, has happened in that time.

Taylor's side bending video put the nail in the coffin for me. It also helped me to understand the different stresses the wood experiences under bending conditions.

Fomerly, the waist bend got more heat than the ends. Also if you measure the temps of a heat blanket it's cooler toward the ends. That may be due to less confinement of the heat allowing it to dissipate.

Anyway, I've switched bending methods. Hand bend on the waist, an outside bend, like Taylor's video. Hey, these guys bend three hundred sets a day, ahem. Then I toss them in the bender for the upper and lower bouts.

What happens during the transition from pipe to form bending, is that the waist is cooling. No more scorched waists requiring excessive sanding and no more bursts unless I want one. Thanks to the OLF, and the generous sharing of info, even from other sources pointed to, is great. I applaud inovation, and the vehicles that carry the news, such as the OLF, MIMF, 13Fret, Frets.com, Guitarmaker, American Lutherie, etc, etc
Author:  Michael Dale Payne [ Wed Jan 18, 2006 3:33 am ]
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I have never scorched a waist since moving to a blanket for my heat source. I measure my heat near the waist since it is the smallest radius to bend and near middle of the blanket. The lower bout requires less heat because it is a larger radius so I dont worry to much there.

I am sure the temp at the end of the blanket does dissipate quicker. Just one of those physics things dealing with mass, heat exchange and thermal transfer.

For me I know I could not bend the waist on the pipe then the bouts on the bending fixture near as fast as I can preheat the wood with the blanket and bend as I described earlier. Besides it is more difficult to get every thing in line ie. slats, blanket and wood if there is a bend in the wood to begain with. It takes me for most woods 8 min max from preheating the flat wood to finished bend using the blanket.

As far as water goes I don’t add much just a surface sprits on each side. I have tried tests with mahogany and maple dry, soaked and spritzed and have had the best results lightly spritzed. I truly believe that the steam is an aid to the bending process. I also believe that over wet wood will stain and rack if not fully dried before un clamping.
Author:  tippie53 [ Wed Jan 18, 2006 8:58 am ]
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   Bending Koa 101
   NO FOIL PLEASE !   I have had some koa go green.

   Kraft Paper is the safest material I found. I soak this for about 1-2 minutes while setting up the machine

   Once the paper and sides are ready I will lighty spray the wood. I then take the wet paper and it goes into the machine like this
Pattern   slat   wet paper   wood   wet paper slat blanket.
   I do place the thermometer between the blanket and the slat. I am interested in the heat at the blanket level.
     I use spring clamps to hold this all together and align in the machine . I thin set the waist cawl just that it gives a little friendly friction to hold this steady.
   Once I see the heat at 250-275 and hear sizzle I will start with the lower bout first as this is the easy bout. I take about 15-20 seconds to pull the hold down into position.
    Once that is down I check my alignment marks and then do the upper bout , but I check to see that the paper is still wet or very damp. If I need to I will spray a little water on. Be careful as it is hot and you can get a steam burn if you are not careful.
    Once I am happy things are wet and the temp isn't ober 350 I do the upper bout , Then with the 2 bouts down I do the waist. This will actually pull the wood onto the mold very well.
   I hold the heat at 275-325 for about 3-5 minutes to dry out the wood. It should look real steamy. Keep an eye on the temp as that will spike once the water cooks off.
    Let this set overnight if you can for best results then place it in the mold. If you are in a hurry you can pull it out at room temp and place in the mold and block in till the other side is finished , then trim and keep in mold till cool and dry,
    A good working temp on Koa is 275 to 325 . This won't scorch and you should have a great result.
John Hall
Blues Creek Guitarstippie5338735.7086226852
Author:  PaddyD [ Wed Jan 18, 2006 9:22 am ]
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hi there i remember reading this on the allied lutherie website:-

Not much needs to be said about koa as an instrument wood. Lots of guitars are have been made with it. One tip I recall is that sometimes when bending sides you end up baking some of the wood's greenish extractives into them. To avoid this, you can soak the sides in water and replace the water from time to time until the water remains clear.

dont know if that any help
Author:  Serge Poirier [ Wed Jan 18, 2006 4:02 pm ]
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Thanks John, that post is gonna be pinned to my shop's board and is going to be very helpful!
Author:  tippie53 [ Thu Jan 19, 2006 2:21 pm ]
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Too much water will make them warp and twist as they dry. Once I stopped using aluminium foil I havn;t had a set turn green .
     
john hall
Author:  Michael Dale Payne [ Fri Jan 20, 2006 2:00 am ]
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John I agree whole heartedly about too much water. we spend sometimes years dehydrating wood to get it to a stable point. It is a balancing act. Just enough to create some steam during the bending is all that is needed. More than will cook out in about 10 min just adds to the possibility of rack and warp. When I first started bending on forms I had a problem with cupping after the bend. I figured out that I was over wetting and not cooking the excess moisture out. When I would remove the sides from the form they would cup in the middle of the plank. I cut the moisture down and have no issues with cuping.MichaelP38737.4206712963
Author:  Anthony Z [ Fri Jan 20, 2006 1:02 pm ]
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John, great description! Have you bent Koa ribs for a Venetian cutaway and if so, any recommendations you could share?
Author:  tippie53 [ Fri Jan 20, 2006 1:19 pm ]
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    When ever I bend cutaways , Especially with high figured wood I use the wet paper technique with the thermomter reading 270.- 325 for at least 2-3 minutes so that I have lots of steam. If the wood is quartered straight stock I only use 1 piece of paper on top from the upper bout into the cutaway.
     I keep a close eye that the paper remains wet to damp while heating and when I see the paper start to go from wet to damp I will start the cutatway. I will complete the cutaway bend in about 1 minute or so from the time I start till I have it aginst the pattern. You want to see the steam coming off as this tell you the water is coming out and creating the steam.
    The entire amount of time is within 7 minutes . It takes about 3 minutes to get to heat and then the actual bend time. I will keep the cutaway in the machine over night to cool. I will hole the sides to heat about 3 minutes once I have them on the pattern and then hold them at 220 for 10 minutes to help dry them off. Too much heat you can scorch and too little , the excess water will cause some serious warping.
     Once I have it out of the machine I keep in either in a drying rack or mold. I found most warping will happen at the ends so I tape a small strip of plywood on the end to keep them flat.
   After a few days when the water is off them they will stay pretty stable
john hall
Author:  Anthony Z [ Fri Jan 20, 2006 1:37 pm ]
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Thanks John, one question I forgot to ask -- do you use spring steel slats?
Author:  JJ Donohue [ Fri Jan 20, 2006 3:57 pm ]
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Then again, there's Wayne Henderson. As described in the recent book, "Clapton's Guitar", he dunks the Brazilian Rosewood sides in a trough of boiling water for 15 minutes before placing it in the side bender. He says "it gives the wood amnesia" and makes the wood "relax into a docile and compliant blob."

Go figure

Incidently, Bryan Galloup suggested that I do the same thing when I try bending the BRW he recently sold me. There must be something to it...just goes to show us...there's more than one way to skin the cat.

Has anyone else done the boil & dunk method?
Author:  tippie53 [ Sat Jan 21, 2006 8:33 am ]
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HEY JJ
    I to have BRW LOL   I use stainless for cutaway . I have spring steel but don't use it much anymore. I found a supplier for tempered stainless and it works very good.
   If you do start to develop a memory bend store the slat it a roll as that helps.
   As for boiling wood I hate that as I allways ended up with serious warping. The wet paper does the trick as wood is thermoplastic and what you need to do is have the wood fibers compress. The steam just is more penetrating and helps to avoid scorching.
   Too much water and you get it locked into the wood too deep and it takes a long time to get it out.
   john
Author:  Anthony Z [ Sat Jan 21, 2006 8:42 am ]
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[QUOTE=tippie53]   HEY JJ
       If you do start to develop a memory bend store the slat it a roll as that helps.[/QUOTE]

Did you mean store the slat rolled-up?

I have a more sophisticated method...lay the stainless slat on the shop floor and jump up and down on it...

Great info John -- you really do service what you sell.Anthony Z38738.6971412037
Author:  tippie53 [ Sat Jan 21, 2006 12:15 pm ]
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   I tried a rolling pin but that didn't work LOL.
I love this hobby and use this stuff to. I hate junk and I want to treat all my customers like friends. You are important to me .
I have met so many wonderful people and just want to give back what I got from this. I cna tell you this hobby saved my life.
John Hall
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