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When you are bending guitar sides on a hot pipe, what temperature do you like the pipe to be at. I will be bending Indian Rosewood and Mahogany.

I find I need to have the pipe in the 450 degree F range for it to bend but I get a lot of scorching at that temperature.

Any tips would be welcome.

Thanks,

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EddieLee

I always drape a damp piece of 100% cotton cloth on the wood (between pipe and wood) when bending. You scorch the cloth instead of the wood.

Sounds to me as though your sides are too thick --- note that we (KMG) thin our sides to the same thickness used at the Martin factory .075" for both Mahogany and EIR.

We use a pipe style bender to pre-bend the waist curve prior to loading them into the profile bender, same as the Taylor factory. Temperature is about 300 degrees.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Keep the wood wet until the bend is well underway. If it gets too dry, wet it again.
I have always soaked my sides before bending. 30 minutes for mahogany, an hour or two for rosewood.
I use an aluminum pipe with a propane torch stuck in the end of it. When water dropped on the pipe sizzles, it is hot enough. I am guessing between 300 and 325 degrees.

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John

The lignin 'glue' in wood actually starts to soften at about 180 F, iirc. Most woods start to scorch at around 300 F. , so there's your window. Some light woods do darken at a temperature lower than the scorching point if held there for a while.

Water seems to lower the softening temperature a bit, or maybe I should say that lack of moisture raises it. At any rate, the longer you keep the wood hot the hotter you have to get it to make it bend, and eventually you need to get it up to the scorching temperature. Adding water is not a free lunch, though. It weakens the boond between the fibers, and can also weaken the cell walls. Weak bonds cause the wood to fail by peeling on the outside of the bend, particularly on things like cirly wood, where there is run out. Weak cell walls collapse on the compression side; this is common on mahogany.

The usual strategy is to heat the wood up as fast as you can so that you don't cook the moisture out, bend it to shape, and hold it there while it cools off below the lignin softening point. A bit of water, usually on the inside (against the iron) helps keep things from drying out too fast, and helps carry the heat through, but you have to think about how the wood will tend to fail. A 'backstrap' of something like aluminum flashing on the outside really reduces the amount of peeling and splitting and speeds things up by holding in both the fibers and the heat.

Try to run your iron at 300 F., and hold the wood in place with some bending pressure until it starts to give. Then just chase that hot spot down the piece, moving faster where there is less curve. Don't forget to hold the shape while it cools.

I usually find it best to over bend everything a bit, and then go back later to correct it. If you're doing that iit's more important to make the curve smpppth than it is to make it right the first time out. You can always correct a smooth bend if it's the wrong curve, but it's hard to fix something that has flat spots and corners, especially if it's gotten scorched.

If the wood does scorch, out it down and turn the iron off. There's not enough moisture in it to bend it, and you can't get it in by just wetting it, so you're just asking for trouble. If you can leave it in a humid place over night it will pick up enough to work.

That's good advice about letting wood sit overnight to pick-up moisture. Advice I've never heard before. I'll file that away for the next time I accidentally get a piece too dry while trying to bend.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

So, I must say again, this forum is a fantastic resource. My side were to dry. I put them in my humidity controlled area for a few day and they bent very easily!!!!

Thanks to all that responded.

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EddieLee

I was unaware that Taylor did this, bur I have to say it has always bemused me when i have read posts on forums which advocate putting a heating blanket on the side and slowly cranking down until the waist is formed, and then pulling the sides over the top and lower bout.

Pre-bending the waist prior to loading into the bending form just seems like such an obvious thing to do, with no downside.

The main downside for production shops would be the usual one: time.

I often do pre-bend the waist, particularly if it's a wood that I have not tried before and there's some reason, such as fancy figure, to suspect that it might be problematic. OTOH, I'll say that with the 'usual suspects' I've had less trouble with the waist in the form that the bouts. Maybe it's because the waist gets bent first, while it's still moist.

Throughout our process (KMG) we locate off the apex of the inner most waist curve including the side bending operation. This resulted in a quantum improvement in repeatably, which is especially important for us since our sides are pre-profiled and we also supply matching molds for our kits etc.

Here's Taylors process:

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Ken Cierp

http://www.kennethmichaelguitars.com/

We've had a few local builders of kits in for help on touching up side sets that likely went out from the kit provider perfectly bent, but relaxed over the months the builder spent before starting assembly. I am wondering if prebending the waist might help with that issue, or whether allowing more time in the bender setting the side would address that issue. All of the side sets have been mahogany or koa, so it seems not to be a problem with rosewoods.

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A constellation only takes shape when one maps the whole.
- Beth Brower

Any side will move a bit if it's not restrained in the mold and the humidity changes. Some are more prone than others. I had a set of apple sides that practically straightened out over night when I left them out of the mold at an outdoor craft fair in August. It gave me another chance to do the demo....