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I use a hot pipe (heated by a propane torch) to bend sides. Well, a side (a mando rim), and some bindings. Anyway, I've successfully proven to myself that I can do it and even enjoy it. I've actually got most of a bending machine in my loft (thanks Larry!), but I can't bring myself to build a body mold for it or buy a heating blanket, rheostat, and timer. For one instrument a year, it feels like cheating.

So, I'm wondering if those of you who use a hot pipe on a regular basis (or used to) can offer any general tips. Here are some of the areas where I feel like I'm flying by the seat of my pants, but I welcome tips beyond these questions. Shoot, anyone want to do a tutorial?

-Do you use a strip of brass or alumninum as a backing while you bend? I tried using aluminum, but it's just too awkward - I can't feel if the wood is giving under the aluminum or if I'm just bending it to break. If you do use a strip, what material and how thick? Where'd you get it?
-How do you know you've got the heat *just right*? I've heard the advice that water should dance but shouldn't immediately vaporize, but that's a little imprecise for my taste. Does it make sense to invest in some kind of cheap thermometer-like device, and if so, what's right temp I'm shooting for?
-How wet should I get a side before bending it over a pipe? Seems I've heard everything from soak it for 30 minutes to just spritz it as you go. Seems like it dries out AWFULLY quickly against the pipe if you don't soak it. What should I soak/spritz with? Just plain water? I've heard of some interesting additives in the past...
-How do you go about the bend? Waist first? Upper bout? Lower bout? Do you mark on the side where you want the peak of those bends to be, or do you just eyeball the first one and use your template to guide you from there?
-Any tips for keeping the bends orthogonal to the soundboard edge of the side?
-Profile the side before bending, or afterwards? If afterwards, how?
-What do you wear to protect your hands? I'm using cheapo welding gloves right now, which work great until I get them wet.

Thanks in advance!

Jay

My experience is very limited, but my luck was pretty good on my bends. The wood was Zebrawood. I used a grill thermometer for temp readings, and did most of my bending in the 350 to 400* range, on the thermometer(it would be less for other woods, I think). I think that the actual heat was a little less than that. When the water thing worked, I started trying - if I couldn't feel some release within 10 to 20 seconds, I waited for it to heat up more. I kept trying until I could feel it pretty quickly, but before I got any burning. I tried using a strip of stainless, but found it to be cumbersome, and made it hard for me to feel the wood while bending. I marked all of my peaks at the waist, upper and lower bouts, and even marked the places where bends started from relatively flat areas - this helped me visualize my mold while bending. I also checked my progress often. I started my bends at the waist, then lower bout, then upper bout. Which one after the waist is probably not important, but doing the waist first makes it easier to check against your plan or inside mold. I also found that bending almost dry seemed to work best for me. I did spritz with distilled water in the waist and in the areas of the heaviest bends, but left them pretty dry for light bends. I also found that the resistance to bending too much and getting a lot of ripples in the bend seemed better the dryer the sides were. This may not be true with all woods, but feeling the wood give is most important, in my limited opinion, and light bends(large radii) seem to go better before it releases fully. As you start to feel it give just a little, slide the side, from side to side, along the pipe, to spread out the heat, then give a little press on each side of the pipe as you are sliding. It will give a nice smooth and gradual bend. I also had a good bit of success with un-bending the same way. If my bend was too tight, I would flip the side over, slide the bent area over the pipe back and forth with light pressure in the opposite direction of the bend. It would open up nicely. I only profiled the back edge, and this only very loosely. The top edge was square to the ends. I kept the squareness by staying square with the edge of the pipe, and I also put a line around the pipe closer the where the bend was taking place, to help me visualize the angle. I did most of my bending without gloves, but did use some cotton work gloves for some of it, they seemed to be enough. You shouldn't have to have your hands right over the pipe. When I did need to put pressure right over the pipe, I used another piece of wood, rather than using my hand. All this from a beginner! Take it for what it's worth, and it's worth what you paid for it.

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Waddy

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I think being able to bend on a pipe or iron is a very important part of building. It gives you a much better sense of the materials you're working on and with, much the same as being able to work with hand tools before you begin shoving wood through machines. It's also good for doing quick bends like cutaways and binding.
I hand bend one of my models (the quatre) on account of I don't yet build enough of them to justify making forms.
I learned some tricks from vetran builder John Greven, who does ALL his bending on a pipe with a torch (we're talking 40 or so guitars a year on average).
So, here's my rig
I use a electric bender from LMI, only rather than wetting the wood, I drape a piece of rag (not colored!) over the iron and spray or use a small measuring cup to douse it (the rag)with water. I'll spray or pour after every time on the iron. This method seems to prevent most scorching problems. I don't use a thermometer, but run it on high.
Sometimes I wear gloves.

I use a couple of sticks to put even pressure on either side of the iron.

For tight curves I use a small metal sheet (.007 stainless that was left over from my bender) that has the two sticks attached to it. The metal supports the bend and the sticks keep the pressure even.


When the part is bent I put it into the mold with spring clamps and small sticks

and this is where some of you are going to shriek in horror...
I spritz the side (in the mold) and dry it using the propane torch. Get it hot, to the point where the water evaporates completely and quickly, but try not to scorch the side. Leave it in the mold until it completely cools and the bend "sets". I'll use about 4 or so spring clamps on each side to hold it in position. This last bit is pure Greven technique. He doesn't worry about the bends being perfect off the iron. He "lets the mold do the work".
Hope this is of some use.
-C

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Freeborn Guitars
and home of BeauGuard©

Jay, Thanks man for asking these questions. I wanted to ask the same ones. I ordered pre-bent sides from LMI but when I got them they weren't anywhere close. I already had a bending iron like Chas has so I had to rebend to what I needed. I'll know next time not to get prebent wood. But, I did feel like everything you said.

Thanks Waddy and Chas for answering.

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"After forty-nine years of violin building, I have decided that the search for a varnish is similar to the fox hunt. The fun is in the hunt."
Jack Batts Maker and Repairer of Fine Violins

I think the best way to learn to bend on a pipe is to get a bunch of scrap strips and bend. bend, bend. Try different things and see what works and what doesn't. If it's scrap it doesn't matter if you break a bunch of pieces, in fact, you will learn a lot that way.

I started out bending on a torch heated pipe... did about 3 guitars that way. Then I built a Fox bender. After bending 3 more sets in the Fox machine, and struggling with trying to use it to bend cutaways, I went back to using a pipe. That was 96 guitars ago. I now have an electrically heated pipe and it is a joy to use. One of the main problems I had with a torch heated pipe, besides having trouble controlling the heat, was scorching or melting holes in the front of my shirt !!! It is also hard to avoid breathing the exhaust when using a torch.

I still use my Fox bender, but not until AFTER I have bent the sides to shape on the pipe. I then put them in the Fox machine to smooth out the curves, reduce ripple and insure symmetry.

Mark

Re: the scorched-shirt problem, I put a cap on the end of my pipe, which prevented oxygen from getting to the flame and put the torch out. I drilled a 1/4" (just guessing, don't remember exactly) hole in the cap and three 1/4" holes along the length of the pipe in a line on the portion that down (6 o'clock) when mounted. That prevents the heat from blasting out the end but gives enough oxygen to keep the torch lit.

I don't know why I put a hole in the cap; maybe I tried that first and it wasn't enough to get air to the flame and then I tried the three along the pipe. Anyway, it seems to work fine.

http://www.barbecue-smoker-grill.com/smpitprhochs.html

one type of bending tool you can cook with it too.

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I dont know if this is right or not, but it worked on a set of indian rosewood sides I just did (om size). used a propane torch in the pipe, water spritz on the wood, used my fingers as a temp gauge, laid the wood across the pipe and felt the top of the wood with my fingers, when it got to hot to touch, I was ready to bend. I found that too much water would lead to cupping of the side and that was no fun to get out. No scorch marks, and the sides fit the mold better than the prebent martin sides I got for my first kit guitar.
Tried a wet cloth on the pipe, that just seemed to take longer to heat up the wood.

I just bent my indian rosewood sides over the pipe, and here's what I learned:

300-350 did turn out to be a good temp for bending. I got a $15 infrared thermometer at Harbor Freight (which has laser built in so you know what you're pointing at - handy) to gauge the temperature. The thing about being at 350 versus 250 is that the went definitely bends more quickly, but you've got to be conscious of keeping it moving and making sure you're getting steam, not smoke.

I sort of split the difference in the advice I was getting on how much water to use. I submerged them for about 5 minutes and was spritzing liberally throughout the process. Used just plain tap water. All of that seemed to work fine. I'd probably do it again.

Starting with the waist, then the upper bout, then the lower bout was easiest for me. I did the first one lower bout first, then waist, then upper bout, and that was really difficult to check against the template or mold. Doing the waist first let me check it against the template, and the waist was a much better point to use a reference while fitting.

I've decided that in addition to horseshoes and hand grenades, "close enough" also counts in bending guitar sides, especially if you've got a body mold and clamping cauls.

For what it's worth, the whole process for two sides, from ambling out to the shop to ambling back into the house after staring incredulously at the seemingly well-bent sides for a few minutes was about 1.5 hrs. I'm sure those of you who do this on a regular basis are laughing hysterically about now. I will say that the second side went WAY faster than the first, both because I had gotten a feel for what I was doing and because I used a much hotter pipe on the second. I was bending at around 200 degrees on the first side, 300-350 on the second.

That was fun. Some blocks, kerfing, back, top, and braces and I'll have myself a box...

Bravo!
An hour and a half for the first time out is VERY respectable. As you gain experience you'll go "hot and fast" like the old timers. Less water is good too.
Do post up some pics of the progress.
-C

_________________
Freeborn Guitars
and home of BeauGuard©

I've always bent my sides over a hot pipe (heated with a propane torch) until recently when I bought an electric bending iron (a bit safer and more convenient). Make a sheet metal "plug" for the end of the pipe if you are using a torch.
Observations:
-First, set the temp so that water vigorously boils off (yes, "dances")
but not so hot that it scorches.
-I soak my sides for only a few minutes and find that with the right temperature on the iron the bend is complete just about the time the water has completely evaporated from the bit that is in contact with the iron. The exception to this would be sides that have a center inlay as in my recent #90, these I spritz and wait a bit for the bends to cool as I move along in order to not disturb the glue joints.
-I use a 1/2 side template and only mark precisely at the waist bend as well as precontour the sides.
- I bend Waist first, upper bout then lower bout moving outward from the waist in increments checking/correcting the bend as I go.
- A thin piece of spring steel (get it from stew Mac ) is used to support particularly curly or other pieces with run out....normally this is not needed on well quartered straight grained stuff.
Congrats on your success!
Learning to hot pipe bend is the way to go, it frees you up from having to make all sorts of bending forms for different sizes and shapes (especially if you "free build" classicals) and at the very least, you end up with sides that you don't have to wrestle with during your assembly.