Official Luthiers Forum!

Ahh, never reached 300.

I have a Minco heater runs around 800 Watts on 110Volts and will hit close to 500 degrees so they say. My thermometer only makes it to 400.

I use a 1000 Watt Commercial dimmer to cut back once everything is bent, just a switch and duplex outlet mounted on a board. Before using that control, I did like Jim Olson and used the plug and unplug method, it works too.

You might want to get a second thermometer in the kitchen gadget section at Walmart. John Mayes turned me on to it. About 12 bucks. This will give you confirmation that your thermometer is correctly indicating.

And well, you are right on the Juglans comment. I got on the Mayan by mistake at LMI:

Black Walnut, Mayan Walnut and Peruvian Walnut are three species new to the LMI catalog. Each offers a great value to beginners looking for a quality tonewood at a great price. All three share qualities of our familiar and popular California Walnut . They are dark in color, bend easily and offer a clear, open tone with excellent depth and strong trebles.

The Black Walnut (from the Eastern United States) is gray in color, often with contrasting tan center strips.

The Peruvian Walnut is a nice, dark chocolate brown color, often with interesting, broad, dark lines. Most sets will have some small, subtle gray mineral spots. The Peruvian variety is slightly more dense than other Walnuts, which may increase volume and/or projection.

The Mayan Walnut (not a “true Walnut” from the Juglans family) is even-colored and straight-grained, and is very easy to work. The color is a light-mocha (decaf anyone?) with contrasting dark gray grain lines. Most sets have a very subtle flame figure, and many sets also have an attractive blonde sapwood center.

I like the Easy to BEnd part!

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http://www.dickeyguitars.com

    http://www.bluescreekguitars.com/tut orial10.php

Here is a tutorial on bending. In a nut shell most peple tend to over cook or over wet the wood.
   If you are not done bending your wood to the pattern in 6-8 minutes you are waiting too long. I set the thermometer between the blanket and slats. Usually I am bending the lower bout in about 2-3 minutes at full power then then I do the upper bouts. The waist is done last so that the sides are "pulled" onto the bending pattern. Once I see the 200 degree mark I am checking the wood for relaxing.
    I never use softening products but if you feel you need them go ahead. The temp range for a good bend is 250-375. The staining can be either iron migration or water staining. I do see that once in a while on African mahogany. I think it may be something from the water chemicals or maybe even iron in the water.
    You have a good bit of spring back. This can be attributed to taking it out too soon or not heating it enough. I use 375 degrees for 3 minutes then 200 for a full 15 to dry out the excess water.
     Again check out the tutorial as you can get bneind instructions there or call me and I will be happy to help you. Never use the blanket without a controller . they will scorch wood.
   The full pattern you made will absorb a great deal of heat from your wood. That is why you see the patterns with the tubes. The heat isn't pulled off the wood and into the pattern. It becomes are large thermal mass.
john hall
blues creek guitars

Hi John, tips from the master.

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http://www.dickeyguitars.com

"and the additional support from the form means that even thin slats perform well."

Uhmmm, the idea is that you need the support while the wood is bending but not yet in contact with the form (as occurs doing the waist and cutaway areas). So I don't see how having a solid form is going to make up for the lack of support from thin slats. Sorry.

Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

OK, I know I'm a dinosaur here but I would strongly urge folks to get a hot pipe bender and learn how to use it. I just purchased one from Stew Mac after using a piece of iron pipe (flattened in an arbor press) and propane torch for thirty years or so.

Hot pipe bending is easier than you think, produces sides with little or no spring back and frees you up to build many sizes and plantillas that you don't have to make a bending jig, or even a form for if you "free build". A luthier friend of mine who already knew how to pipe bend purchased  a Fox style bender from a supplier and after using it a few times, it collected dust for several years and he sold it on ebay. Meanwhile, the many side sets he bent were all produced the old way.  

Even if you are commited to the bending machine approach a hot pipe bender can help you refine the results.

   Bending machines are designed to work with building molds and forms. Free building as Dave is mentioning is mostly for both but free building without molds you need a pipe.
   The bender gets you close and the mold does all the refining of the shape
john hall

Todd,
I agree with your point about the value of a solid form helping to reduce cross grain ripple. In the form I made to go with the spring steel slats I made it "semi-hollow" which is to say I added a middle board. So there's only about 1.75" gaps  across the form  between the boards.  I think the  spring steel is rigid enough that  I won't have any  rippling  over that distance. For some reason, the area I was was having the most breakage was the first inside curve closest to the neck in the cutaway. So for me, it seemed important to get good wood support under the ram as it pushes into the cutaway. So if I was making a choice, I would have the thicker slat on the bottom. For the other tight curve to make the horn, you already get support on the inside as you press on the form and you can provide it on the outside with the bar that is doing the pressing. That's my theory, but it may well be wrong. Personally, I would prefer to have support on both sides using "strong" slats so that I could move the ram out over the cutaway early without having to think about using to support the outside of the wood while doing the horn area.

Hesh,
With respect to using "regular" stainless steel slats you are right. I don't know what I am talking about since I have never used them so in that regard people should take what I am saying with a grain of salt. However in making your recommendation you described the stainless slats as "whimpy" and from that I took that they offered less support than the spring steel. If stainless provides all the support you need and they flatten easily after use, then I would agree, use them to reduce staining. I think part of my reaction has been my joy at finally finding a method that gives me good consistent results and I wanted to share what I think have been the reasons.

This may be awkward for John Hall since he sells both, but I know that he has done a lot of experimenting with different slats with respect to thickness etc. So I'd very be interested in his opinion on their relative merits just with respect to the support they provide the wood and if that's really all important.

Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

things i will do differently next practice run:

1.  possible work indoors (if the wife smiles on it ) as the temperature is a bit warmer and the humidity probably lower.

2.  after the bend is complete, cook the side for twenty minutes or so at a lower temperature to dry things out.

3.  probably use foil and craft paper this time. i just realized that on the second side i bent (the worse of the two), i wrapped the side comletely in foil with no way for moisture to escape.

anything else?

as for bending with a hot pipe. i gave it some thought and then decided on the heating blanket. i figured i would probably end up using a blanket eventually anyway, so why not just start with it? maybe it would have been a good idea to get started with a pipe, but since im $200 deep on blanket/slats and hours in the shop making molds and forms, i think ill stick with my current method. thanks for the advice though.

david, i just laughed really hard because i looked at you profile to see what your first name is and noticed your occupation is "museum exhibits." was it a figure of speech, or are you really a dinosaur?

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sweat the small stuff.

H,

That is funny! (though unintentional........!?..). I do work at a Museum and have been building now for 41 years and sometimes feel like a dinosaur in that I that I started at a time when there was one place to buy wood, one how-to book and Martin guitars <REALLY WERE> hand made. Just wanted to chime in with another perspective.

Best!

John,
Excellent post! Reminds me of how much I miss building..better get by butt in gear.
Thanks for the great post.

Mr Laplante
    you are not a Dinosaur as having the privilege of meeting you through Steve and at Asia you had given me some valuable advice. Those of you that don't know David , he is very experienced in luthiery. He was very helpful to me when I started.
      Things have progressed since the "old days" and the internet has made information so available from the few things that we could gleen from just a few years ago.
     I believe there is more than 1 way to do this and you as the builder need to find your own path. I have been at this now for about 10 years and have learned a lot. Often because of a failure or I was lucky enough to get to meet some knowledgeable people like yourself.
     I know if you use the machine aluminum is not the way to go. Steel either stainless that is tempered or spring steel will have more than enough strength to support the wood.
    Warping on bending can be from a few things. Too much water , pulling out the side when it is still warm or sometimes it is the wood. That is why quality wood isn't always the cheapest but is often the better buy.
   Hopefully we all learn from each other and can agree that this is why we are here , to share what we know.
john hall
blues creek guitars

well, this is my third try. it seems like im getting worse with each attempt. not sure what to do now. guess ill try again, eh?

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sweat the small stuff.

If you were bending using a pipe I would be telling you wait for the wood to relax that you can feel it when it does.

Not having form bending experience limits my ability to help.

It does sort of look like you bent the waist first and cooked the bouts dry before you got to them. It is easy to be wrong just looking at a pic though.

I think you should describe the order of operation and a rough time line.

_________________
"It's a Tone Faerie thing"
"Da goal is to sharpen ur wit as well as ye Sgian Dubh"
"Sippin Loch Dhu @Black lake" ,Kirby O...

YOU WILL get the feel for your method just keep at it.

_________________
"It's a Tone Faerie thing"
"Da goal is to sharpen ur wit as well as ye Sgian Dubh"
"Sippin Loch Dhu @Black lake" ,Kirby O...

Perfect opportunity to make a Venetian Cutaway though......(hope it's the treble side....)

call me and I can help
john hall
blues creek guitars

    I suspect you may be doing one of 2 things , One you may be waiting too long and not getting the heat you need or overheating.
   If you case harden the wood , and this means you over cook and over dry it you turn the wood very brackish and it will snap.
   Another thing is that you may not be working the wood as you should. If you are just pulling the ends you can brake it , I like to use the hold downs and roll the wood onto the pattern.
   The total time in the actual bending process should be about 6 minutes. Todd describes bending perfectly
Just in case what is your heat? 325 is a good all around temp
john hall
blues creek guitars

you guys are just too cool. thanks so much for the response. well, this time around my sandwich was from top to bottom: blanket/slat/foil/parchment/oak/parchment/foil/slat. lightly misted both sides of wood prior to wrapping it all up. turned blanket on full blast for about 3 or 4 minutes prior to starting bends. temp between blanket and first slat was around 320 when i started. bent waist first, stopping about 1/2" shy of full bend. next i bent the lower bout, then moved on to the upper bout. the entire process took about 6-8 minutes. i then cooked the side for about 20 minutes at around 290 degrees. the whole thing cooled for a few hours. then i went back outside and cooked again for about 10 minutes at 290 degrees. brought everything inside and it sat in my house (45% humidity 70 degrees F) for 12 hours or so then i took it all apart and wept. ok, i didnt weep, im doing great, but i was a bit bummed. itll be that much sweeter when i get it right!

the three sides ive bent, i havent realy seen any steam rising and have not heard a whole lot coming from the sandwich. more water maybe? i KNOW it got hot enough this last time. maybe too hot. anyways, im off to read john hall's tutorial on bending. maybe ill give you a ring john. thank you so much for the offer.

after my first attempts and all the spring back, i thought for sure more heat and longer period of heating would eliminate all of the spring back in the wood. even if the wood had not cracked this time, there is still substantial springback. whats the deal?

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sweat the small stuff.

ok, i just read john's tutorial on bending. the one thing that im curious about, is bending the waist last. im having a hard time imagining that happening with the cauls ive been using. the springs hold them fairly tight against the sandwich and it seems like alot of material to pull in with the cauls securely in place. can someone describe this in a little more detail? john?

where do you buy kraft paper?

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sweat the small stuff.

sorry hesh, we posted at the same time. 3 of the 4 sets of springs are pretty strong. i dont have anything to compare them to, but they are pretty much as you desrcibe above. the springs above the upper bout are a little weaker than i would like them to be, but then there are two sets on both the upper and lower bouts, repsectively.

_________________
sweat the small stuff.