Official Luthiers Forum! :: View topic - Bending different species wood

I can tell you what results in perfect, zero-springback, true sides in difficult woods for us:

- A minimum of three plies in the mold so the full width is supported...preferably a solid mold, but much of the additional support needed, especially for shapes with flat runs, is provided by a center laminate

- A dedicated waist caul. We were given a second bender with a universal caul, and after a few uses, modified it to the same dedicated caul as on our original benders. Dedicated cauls ensure the waist is properly shaped, with contact for 1-1/2" - 2" out from the center of the caul...that makes a big difference in accuracy of waist shapes for guitars with more turn in that area than a dreadnaught.

- We don't worry too much about temperature...worry about steam. With a 5 watt/in^2 blanket on FULL, the waist can be brought down to 1/4"-3/8" off the form as soon as visible steam is rising from the bending sandwich. The lower bout and then upper bout follow immediately, with the waist hard set once the upper bout is done. About ten minutes will be required to cook off most of the water in the bending sandwich if the kraft paper is wetted and squeegeed such that it presents a satiny appearance...once the steam stops rising (we use the fogging of a pocket compact mirror - the kind used when noses are powdered - when it is difficult to see any more steam rising to verify that the bending sandwich is empty). We then set the controller to VARIABLE and dry somewhere around 260 deg F - 280 deg F for 40 minutes. Once the timer clicks off, we let things set for an hour for rosewoods and 9-12 hours for mahogany, acacias, etc.

- We use SuperSoft II for anything figured or prone to cross-grain ripples and other bad behavior. Even very difficult woods such as curly ash and highly figured curly anigre behave well when properly treated.

Author:	Bill Higgs [ Wed Nov 06, 2019 6:45 pm ]
Post subject:	Bending different species wood
Has anyone seen or know of a chart/table/instruction guide that gives techniques for bending many of the species of guitar wood? Thanks. Bill

Author:	Clay S. [ Thu Nov 07, 2019 8:40 am ]
Post subject:	Re: Bending different species wood
I have never seen a chart like that, but it would be a good one to have. Maybe rate the bendability of the species, the thickness, and temperature they like to bend at. I don't measure any of those things, so I don't have any data to contribute, but many here do. If people would share their experiences then perhaps a list could be complied and augmented as more data is contributed.

Author:	Colin North [ Thu Nov 07, 2019 10:12 am ]
Post subject:	Re: Bending different species wood
Using a bending iron or a blanket and fox bender?

Author:	Colin North [ Thu Nov 07, 2019 10:15 am ]
Post subject:	Re: Bending different species wood
http://www.13thfret.com/articles/sidebending.html

Author:	bluescreek [ Thu Nov 07, 2019 10:43 am ]
Post subject:	Re: Bending different species wood
I have been bending for 20 years I found that many blankets are not the same, so with this in mind a good point was made hand or machine so in this case lets say machine. The blanket is the key if you have a 2 1/2 watt per sq in blanket 2 may be what you need. I never understood this idea and I did try it and never say a benifit for it, so this is how I bend . I use only 5 watts per sq in this provides plenty of heat for the thermal load. Once you start bending the heat transfers from the blanket to the slats thus into the wood. I don't measure the heat of the wood I rely on the heat on the blanket. I learned pretty early that moisture is a refrigerant and will give you a false reading so you may set the cell before bending and cause cracks. So most woods will bend very similar in the temp range though a few woods tend to over bend and I will address that, First I use .075 in thickness when I bend. This is the same that Martin uses. I used to bend at .090 and .095 and had more cupping issues. I don't use alum foil but I do use untreated butchers wrapping paper and you can get that at uline. I also stopped using super soft2 as windex works just as well and doesn't stain the wood plus it is a good bit cheaper. My method is this with exception listed below I pre shape my side to the radius of the back thinned to .075 dampen the slap with a few spritzes and set the paper into the moisture . This helps to keep it from moving around. Then I spray the top of the paper. I will then spray the wood. We will assume you have them marked right and left and show side. So with the wood DAMPENED I lay that on the paper and spray the top of the wood and apply another sheet of paper also dampening that. Then slat then blanket. I set it into the machine and set on the hold downs. I like to place a weight on the lower bout. when the sides heat and are ready to bend thew weight will slide off. I place a thermometer under the top blanket between the waist and the lower bout , and turn on the blanket to FULL and allow it to heat up. Usually in the 250F range things will be ready to go. I do the lower bout first this is a walk down not a pull and fly so take about 15 to 20 seconds to set the hold down. Move the them to the upper bout and at about 275F you are ready . Also note that you want to check that the upper bout is still damp and has not dried out. So id you need to spray it do so. Again a walk down with the hold downs. You can also add a weight to the front I use about a 3 b chuck of Alum. So now the upper is bent so run the waist. At this point I let the heat go to 325F to 350F once it gets there I set the control to VAR and dial in a 275F. I give this a 15 min cycle and let it cool down. You can check to see how well your bend did before removing by sliding the lower bout hold down up and hold the lower slat down and see how the wood is sitting against the pattern. I have a spring back factor so it isn't going to be tight to the pattern but should be close. Maple I will not use as much water so you use just a small amount. Some figured woods need a slower bend and this comes from experience. This is were having weights on the slats helps to let you know when it is ready to bend. If I need to heat cycle again I spray a little water in there and just run the heat up to 375F then cool down The key is your patience and learning to know when the wood is ready to bend. Common mistakes are bending too soon or taking too long. From the time I turn on the machine until the sides are bent on the pattern is about 4 to 5 min. Then heat cycle takes about 5 more and the 275F setting and drying cycle 15 min. Cool down then is about 45 min hope this helps.

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Author:	SnowManSnow [ Thu Nov 07, 2019 1:14 pm ]
Post subject:	Re: Bending different species wood
John... you let it sit at 275 for 15 min, or ammo reading that wrong ? Sent from my iPhone using Tapatalk

Author:	bluescreek [ Thu Nov 07, 2019 5:23 pm ]
Post subject:	Re: Bending different species wood
that is 100% correct you have to set the wood cells so they hold shape.

Author:	SnowManSnow [ Fri Nov 08, 2019 7:19 am ]
Post subject:	Re: Bending different species wood
bluescreek wrote: that is 100% correct you have to set the wood cells so they hold shape. Are you using a temp controller? If not how do you get it stable ? Just know about where on the dial it is? Sent from my iPhone using Tapatalk

Author:	bluescreek [ Fri Nov 08, 2019 9:25 am ]
Post subject:	Re: Bending different species wood
just get it close with the thermometer you can dial it in . and you will know about where it is

Author:	Bill Higgs [ Wed Nov 13, 2019 11:53 pm ]
Post subject:	Re: Bending different species wood
Thanks again John for all your help. You have no idea how much info I have gotten from you over the years. And thanks Colin for the John Mayes info.

Author:	Colin North [ Thu Nov 14, 2019 6:30 am ]
Post subject:	Re: Bending different species wood
Bill Higgs wrote: Thanks again John for all your help. You have no idea how much info I have gotten from you over the years. And thanks Colin for the John Mayes info. I'll just say what although I posted the info you were asking for, I myself have started to use John's method as a guide. But I still use SS, although I have experimented with ammonia as Windex of that type is not available in UK.

Author:	bluescreek [ Thu Nov 14, 2019 8:00 am ]
Post subject:	Re: Bending different species wood
I also used to use fabric softener although I can't say it did anything Super soft is fine if you can't get the windex although you can make your own. a little ammonia about a table spoon per pint should be enough we will be shooting new vids soon so look for the updated bending videos coming your way soon

Author:	Woodie G [ Thu Nov 14, 2019 3:22 pm ]
Post subject:	Re: Bending different species wood
From an earlier post: Quote: I can tell you what results in perfect, zero-springback, true sides in difficult woods for us: - A minimum of three plies in the mold so the full width is supported...preferably a solid mold, but much of the additional support needed, especially for shapes with flat runs, is provided by a center laminate - A dedicated waist caul. We were given a second bender with a universal caul, and after a few uses, modified it to the same dedicated caul as on our original benders. Dedicated cauls ensure the waist is properly shaped, with contact for 1-1/2" - 2" out from the center of the caul...that makes a big difference in accuracy of waist shapes for guitars with more turn in that area than a dreadnaught. - We don't worry too much about temperature...worry about steam. With a 5 watt/in^2 blanket on FULL, the waist can be brought down to 1/4"-3/8" off the form as soon as visible steam is rising from the bending sandwich. The lower bout and then upper bout follow immediately, with the waist hard set once the upper bout is done. About ten minutes will be required to cook off most of the water in the bending sandwich if the kraft paper is wetted and squeegeed such that it presents a satiny appearance...once the steam stops rising (we use the fogging of a pocket compact mirror - the kind used when noses are powdered - when it is difficult to see any more steam rising to verify that the bending sandwich is empty). We then set the controller to VARIABLE and dry somewhere around 260 deg F - 280 deg F for 40 minutes. Once the timer clicks off, we let things set for an hour for rosewoods and 9-12 hours for mahogany, acacias, etc. - We use SuperSoft II for anything figured or prone to cross-grain ripples and other bad behavior. Even very difficult woods such as curly ash and highly figured curly anigre behave well when properly treated. I'm not sure there is a 'too soon' when using rosewoods or SuperSoft 2 treated woods, provided the package is steaming when bending begins. Even for notoriously difficult-to-bend woods like curly anigre, once the phase change from liquid to steam begins, that steam is far more effective in plasticizing the wood than temperature change alone for exactly the same reason that a steam burn is far worse than a hot water burn. Most problems we've seen with bending have been waiting too long, versus not long enough...if you have some scrap maple or oak sides and want to experiment, it is revealing to see the difference between bending as soon as the steam is visible coming from the package and waiting until most of the steam has been generated (another 4-5 minutes). Adding water beyond what is in the paper may be a problem for woods that see fiber collapse on the inside of the bend, such as figured mahoganies and the aforementioned anigre, as well as highly figure ash or maple. Less water is better, and as Mr. Hall mentioned, a blanket with a faster temperature rise is highly desirable, as that is what will cause the quickest, most uniform change from water to steam in the bending package.

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