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i stink at bending
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=14134		 Page 1 of 4
Author:  Heath Blair [ Thu Oct 18, 2007 12:12 pm ]
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this is like the third time ive written this because i couldnt figure out how to resize my pictures to be less than 200KB. finally got it. a man i work with always says, "heath, there's a learning curve to everything." i think hes right. in fact, i know he is. anyways, back to the matter at hand.


ok, so i finished up my guitar mold and side bender sometime last week and before i went to town bending my actual guitar sides (peruvian walnut), i thought id have a few practice rounds with some quarter sawn red oak (home depot). to my amazement (and delight), i was able to thickness two 36"x4"x1/4" boards to .085" on my thickness planer. i was fully expecting a splintery explosion, but everything worked out just peachy.


heres a pic of my bender. six inches wide. solid MDF. i used one caul at the waist, two at the upper bout, and two at the lower bout.


i compensated the form only with the thickness of the wood and one spring steel slat (.015"). my "sandwich" was blanket/slat/wood/slat. fisrt attempt wood was misted with tap water and wrapped in parchment paper. stained the wood and rusted the heck out of my steel slats. second attempt was just wrapped in foil, no water. i studied hesh's side bending tutorial and then went to town. both sides were cooked twice at (?) temperature. im not sure how much i trust the little digital thermomter that came with the side bender. i dont think it ever read 300 degrees, but was on for ten minutes or more. the second side i let sit over night and i think it was worse than the first. so here is my first attempt at bending. im sure youll understand why i think i stink at bending. what in the world went wrong?


Author:  Brad Way [ Thu Oct 18, 2007 12:45 pm ]
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Heath...I feel your pain. I am no expert at bending but I did find that I had better luck listening to water sizzling on the bender slats than only following the temp off a thermometer. Some others will need to add their experience but it seems like 10 minutes seems like a little more time than is required. (just a hunch) Unfortunately side bending is as much of an art as a science.

Good luck...Please post your results if you get it worked out.
Author:  Martin Turner [ Thu Oct 18, 2007 1:10 pm ]
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Hi Heath,

I use Heshs method to bend my sides and have had pretty good success
so far.

It looks to me like you didnt have quite enough heat going to the wood. I
tend to wait untill I hear the water sizzling on the slat rather than rely
totally on the thermometer. On my form I cut the bouts with a slightly
tighter than nominal radius so I can over bend the side slightly and thus
compensate for spring back.

Be careful running your sides through your thickness/planer. With some
woods you can end up with serious tear out and a wrecked side.

Cheers Martin
Author:  Bruce Dickey [ Thu Oct 18, 2007 1:18 pm ]
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Heath, just looking at the picture, I'd say the second side didn't get hot enough.

Look at the well bent side, see the slight scorch marks here and there? That's an indication of heat.

Now look at the sprung side, see those marks? Not there are they? So, set that one back up in the bender as before, spritz, wrap, and hey, trust that little thermometer, and your nose.

Most walnut bends like butter, so this may be easy if you just don't give up.   
Author:  K.O. [ Thu Oct 18, 2007 1:59 pm ]
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Are those marks scorch or blue? Oak is high in tannic acid, and iron oxide from the steel can stain the wood. Though I use tap water I think it can also be a problem if you have water with a high mineral content.
Author:  Bill Bergman [ Thu Oct 18, 2007 2:20 pm ]
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Some years ago I soaked sprung sides and put them on the mold without heat for days to dry. They were absolutely shaped exactly like the mold when removed.
Author:  K.O. [ Thu Oct 18, 2007 2:36 pm ]
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I suspect that your second side took less of a set since you bent it sans H20.
Author:  K.O. [ Thu Oct 18, 2007 2:49 pm ]
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A concern that I have is that you said you planed the sides to thickness. This to me is a process that requires finish sanding in that any small nick is an invitation for tear out.

Author:  Heath Blair [ Thu Oct 18, 2007 2:49 pm ]
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the marks that you see, are blue. not scorch marks. i kinda suspected not enough heat, but i cooked the sides way longer than i had heard of others cooking them. so i wasnt sure... im still not. if the heating blanket (john hall - blues creek) is on for that long, shouldnt it get well over 300 degrees?



the only reason i ran this wood through the planer is because i didnt care all too much if they exploded. i just wanted to see if it would work. i would never run an expensive set of tonewood through the planer. a five dollar piece of oak was worth the experiment.


so todd, you run your blanket for twenty minutes after you complete the bend?

Author:  K.O. [ Thu Oct 18, 2007 3:12 pm ]
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I do not disagree with Todd as I have yet to bend using a form except when I experimented with cold bending.

Also Bruce could be on target it is just that it looked to be staining rather than scorching, I am just presenting just another possibility.

also edit above post to read,

tear out during bending.
Author:  K.O. [ Thu Oct 18, 2007 3:17 pm ]
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oops you where typing.
Author:  Bill Bergman [ Thu Oct 18, 2007 6:07 pm ]
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By the way. If you do try to clamp it wet and cold, you still need a moiture barrier over your mold, because the water will swell the grain in the composition board and distort the mold permanetly. Even a layer of Saran Wrap will suffice.
Author:  Bruce Dickey [ Fri Oct 19, 2007 12:36 am ]
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HBlair, what is your side thickness? And are you using a digital thermometer? In one query it appeared you didn't know the temp.

Do you have a pipe bender? I've enjoyed a few sets of nice side bends by replicating something Taylor guitars is doing.

Their bending machines first bend the waist, then they transfer the waist-bent sides to a final UPPER and LOWER bout bender. All outside bends. I don't know anyone else on the OLF who's tried it. We all get set in our ways.

The reason I asked you Walnut and Oak thicknesses, it seems not to be addressed or I overlooked it in the post. Thickness is important. .080 to .090 inch thickness is what you want. Thinner in cutaways.
Author:  Bruce Dickey [ Fri Oct 19, 2007 3:43 am ]
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I see no scorching on any wood. Hesh, thanks for pointing out his thickness, that seems good. With this light colored wood, I'm just amazed it's not scorching.

Scorching is why I went to waist bend, cool, add to bender with the waist prebent. Toss on the blanket and go. Again, I have bulbs inside my benders and blankets on top. Kinda hard when you have solid benders.      But I think the rational is the same even with just a blanket.

Remember to anyone bending wood, make sure there are no drafts..... fans, A/C units, heaters blowing, windows open, drafts of any kind kill sides, cRRRRRRRRRRAAAAAAAAAAccccccccccccccccccck!

I just think we're not getting hot here. If so, it either bends or makes toast! I bet he gets whatever his problem may be and he'll be sharing a DOH! Moment with us.

Author:  Pat Hawley [ Fri Oct 19, 2007 9:54 am ]
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Gee, only my second post and I'd like to qualify something Hesh said earlier where he recommended stainless steel slats over the spring steel slats. And after he so graciously welcomed me to the forum with my first post! Sorry Hesh!

Personally, I like the resistance that the spring steel slats provide because I feel that resistance results in more support for the wood and helps reduce the probability of breaking. I think this is especially important when bending for a cutaway but probably not that important for non-cutaway guitars. In support of this belief I would point to the Taylor Factory Fridays session on side bending where Bob Taylor stresses the importance of the pull (i.e. pressure) they are putting on their wood as they bend it. I think John Hall is right to recommend the spring steel for cutaway sides.

I would also add that with the last sides I bent, I used the Super Soft II veneer softener and I think that also makes a big difference. I bent about ten scrap pieces of wood and using the Super Soft II had zero breaks. When it came time to do the real thing, quilted bubinga, I went with spring steel slat, foil, moistened paper, buginga sprayed with Super Soft, moistened paper, foil, spring steel slat, heating blanket and finally an aluminum slat. No breakage and very little spring-back. I doubt I'll ever bend sides without Super Soft again.

Pat
Author:  WaddyThomson [ Fri Oct 19, 2007 10:25 am ]
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Ahhh, the trick to SuperSoft II is to let it dry wrapped in kraft paper, and clamped between flat boards.  Couple of days drying time, then bend normally, as though you had not used it.  I learned that here at OLF.  Someone will correct me if I'm incorrect.
Author:  WaddyThomson [ Fri Oct 19, 2007 10:28 am ]
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[QUOTE=WaddyT]Ahhh, the trick to SuperSoft II is to let it dry wrapped in kraft paper, and clamped between flat boards.  Couple of days drying time, then bend normally, as though you had not used it.  I learned that here at OLF.  Someone will correct me if I'm incorrect.
[/QUOTE]

Well, you don't put the SuperSoft II between two boards and let it dry, you spray it on your sides, wrap them in kraft paper, and clamp flat between a couple of boards for drying.
Author:  K.O. [ Fri Oct 19, 2007 10:58 am ]
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Pat I have used painted galvanized for strapping while bending using my BBQ,s chimney to bend, so for me it is hard to believe that spring steel is needed.
Author:  Heath Blair [ Fri Oct 19, 2007 11:02 am ]
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thanks so much for the responses guys. im not distraught at all, as i was viewing this purely as a trial run. to work out all the bugs. better now, than later when the real zoot is at risk. i believe, as others have pointed out, that the culprit here is not enough heat. the question is, how do i go about getting more heat to the wood? the sides were bent outside in my garage (i call it a shopBig smile). it was cool outside, but definitely not cold. i did hold the wood together with spring clamps. with the blanket being on for such a long period of time, and still not transfering enough heat, is it possible there is something wrong with the blanket? i dont know. i think ill give it another go tonight. good fun.
Author:  Heath Blair [ Fri Oct 19, 2007 11:04 am ]
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hey guys, im serious. thank you so much for the time you put into your responses. my wife says, "thank you" too. Big smile
Author:  Pat Hawley [ Fri Oct 19, 2007 2:38 pm ]
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Waddy,
If you go to the site that sells Super Soft II you will see a little video of a guy spraying it on veneer then immediately wrapping the veneer around a pencil. So the effect on the wood is immediate. My impression from the advertisement is that the two days clamping in boards and paper is the way to get veneer to dry flat. They also point out that it can be dried faster with an iron if desired. I have found that by the time I'm done bending the thicker wood for the sides (as compared to a veneer) it is pretty dry and will hold it's bent shape - and on top of that I put it in the form for "safe keeping".

K.O. ,
I'm basing my comments on the value of having good wood support with the spring steel in part on the Taylor Factory Friday video, discussions with John Hall and the bad experience I had using a lighter material. The first "slats" I had I made from aluminum roofing metal that I picked up from Home Depot. It was cheap and convenient but I payed the price latter on trying to bend cutaways. It offered no support to the wood and, in fact, I even had trouble keeping it in real good contact with the wood in the crucial areas being bent. As you know, this is vital to get good heat transfer to the wood. After some discussion with John Hall I decided to go with the spring steel. During some test runs clamping only the steel I was surprised at how much force was needed to push it into the cutaway and I did have the same concerns about breaking wood just getting it off the bender after bending (as expressed by Hesh) but, in fact, that has not  been  a problem. When doing my bending now with the spring steel the wood is clamped very tight all through the curves thanks to the spring in the metal and I'm convinced that has played an important part in the success I am now having. Plus the Super Soft - I have to admit that I've made two changes at the same time and I can't absolutely say which has been more important. I have no problems however repeating my advice that for cutaways use the spring steel slats and the Super Soft II.

Pat
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