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Of the 70 or so instruments I've built that require side bending I've never had this happen. I guess there's always a first. Even thought I was ten times more careful the same thing happened at the same spot on both sides so I can only assume it was a flaw. It was in the waist but it's not really a sharp curve. I bend on a hot pipe and never not once have seen so much of a minor crack. This just snapped like a twig with barely any pressure....

But anyway. I ordered some super soft 2. I've googled around a bit but can't seem to get a consensus on how to use it for guitar building. Some say they use paper, some don't, some just sprites it, others let it soak. Some let it soak over night, others for 4 hours. Some say to make sure the SS2 is completely dry others....

And so on.

So what is your schedule for using SS2 and especially for tricky wood like figured stuff or in the case of my tragic experience very old BRW

I spray it liberally on both sides then lean it up to dry over something absorbent. Sometimes a bit of color will run off but it's never been an issue. I let the sides dry overnight and bend the next day.

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Steve Smith
"Music is what feelings sound like"

I spritz it, wrap in parchment paper and let sit overnight. It works for me, but I just made that schedule up.

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http://www.Harvestmoonguitars.com

And do you bend totally dry? Or do you let the SS2 boards dry out real good then use water?

I've used it a few times. I let soak in for at least an hour but I don't care if it dries or not I wrap in paper & or foil and bend as usual. Use gloves and a mask. Nasty stuff.

I've only used it on veneer. Mainly to get it flat. To do that I spritz it thoroughly then layer the veneer with paper towels and clamp it between pieces of plastic covered MDF. I leave it overnight then replace the paper towels, clamp it and leave it overnight again.

A shame you lost the beautiful BRW. Looking at the grain I'd have guessed it would bend easily, it might have had an invisible stress fracture from felling.

To be sure, for suspected difficult/tricky or expensive exotics sides I apply SS2 liberally, wrap in clingfilm then ulufoil to stop evaporation and leave overnight to soak in, although I know others just spray and go.
Unwrap, wipe with a paper towel and sticker, by the time your iron is hot they'll be surface dry - spritz as usual and go.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

The procedure I use is based on this one from the Veneer Supplies web site:

Use full strength. Apply by dipping, spraying, or brushing.
Allow veneers to stand until the surface appears dry.
Place veneer between two sheets of absorbent paper (paper towels, brown paper, or unprinted newspaper) and clamp it between two flat boards in a press or simply by placing weight on top.
Allow 12 hours for the initial drying to take place.
Remove from press and replace the absorbent paper. Re-apply pressure or weights.
Replace absorbent sheets every 6 hours until veneer is completely dry.

In my case, I lay the sides on newspaper on the floor and spray until wet. Let it sit for about 5 minutes, turn the sides over, and spray the other side and let sit for another 5 minutes. I blot off excess SS II with a paper towel. I lay a sheet of wax paper on the bench top (to keep the SS II off the bench), then a paper towel layer, then the sides (next to each other), another paper towel layer on top of the sides, another sheet of wax paper, and then I place a large wood billet (about 25 lbs) on top and leave it overnight. When I take it apart the next day, the wood is dry to the touch. I've found I don't need to do a second round of drying between paper towels as described in the web site method.

As you mentioned, some people apply SS II and go to bending in only a few hours instead of letting it sit overnight. My guess is that this works for woods that don't need a lot of encouragement. A couple weeks ago, I bent Peruvian walnut binding for the guitar I'm building now. The sound hole binding bent fine without SS II so I thought I would be able to bend the binding for the body just as easily. Wrong. The first piece snapped like a twig almost immediately when trying to start the waist bend. Second piece same thing. So I sprayed four pieces of binding with SS II and let them sit for three hours. I tried bending two pieces and they didn't snap like twigs, but they did start to crack in the waist bend. I sprayed more pieces and left them hanging overnight. The next day, all of those pieces bent easily and smoothly.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Clamping the wood down is necessary when dealing with standard thickness veneer because it will curl up severely if left to dry in the wind. But there is no need to blindly follow the directions when using SS on guitar sides. I spray the sides and stand them up leaning against the work bench to dry overnight. Never had one warp from this process, but if it did, so what?

I had very old 250 odd years Cuban mahogany break for no obvious reason, I feel like wood gets brittle when it gets very old.

Good question and there does seem to be a bit of a consensus to leave overnight.

What I have often wondered is what sort of residue is left on/in the wood? Do people do anything to clean up after bending?

Cheers Dave M

My thoughts too. It was not perfectly QS but close enough. This rosewood was cut in the '60's so it's old. IDK if that hardens it up and makes it brittle. I've certainly seen that in very old oak that I have used. But having bent EIR and Mad rosewood in the past I thought rosewoods were pretty easy to bend.



Ok I have heard of this method on a few sites before too. This is probably what I will do. and I'll practice on scrap too.

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I might be able to salvage this wood for a mandolin. But I was also thinking I could use it for a guitar for myself. The break is on the 'lap side' of the guitar anyway and what I was thinking is I can rout a lap joint in each broken half and mate them up as close as possible and just carry on. Probably put a spruce backing strip on the inside. Thoughts?

I bend on a pipe. Usually I'll spritz on a bit of water just enough to make some steam while I'm bending.

_________________
Steve Smith
"Music is what feelings sound like"

What you have there looks like a 'brash fracture'. If that's the case there's not much you can do about it.

Green wood tends to fail in compression, so trees have devised ways of making sure the wood stays in tension, even under moderate bending. One way is to pre-stress wood as it grows, so that each new ring line is in tension relative to the wood underneath. This can manifest itself as strips cut from the outside edge of a quartered piece bend away from the center of the tree. It can also make it very hard to cross cut a quartered plank by cutting in from the outside of the tree, and very easy when you cut out from the center.

Each new layer of wood going on in tension relative to the wood under it necessarily puts the old wood into compression. In large trees the weight of the bole plus the built-in stress near the center of the tree can actually exceed the compression strength of the wood. The wood structure can fail microscopically in compression. This is similar to 'wind shake' but not visible, since the damage is microscopic. In effect the wood is already 'broken', and will fail in bending as soon as you try. The result is the sort of 'brash fracture' you see there: it has broken off cleanly across the grain. I believe this is one reason the old boys used to leave those tall stumps behind: there's lots of stress built into the buttress.

I have noticed on wood, such as redwood, that is prone to this, that wood with this sort of built-in crush failure tends to have low long-grain stiffness, high density, and higher damping than usual. It rings like cardboard. Easy to check on.

If I had more of that wood, and was determined to use it, I'd be very inclined to sand it out really thin and laminate it onto something that you know will bend. With proper support you'd be likely to get away with it.

Double sides, waist wedge, start a new trend...

I'd go with a butt joint, and backing strip made of side offcut. Glue the backing to one side, and then use masking tape to make a hinge so clamping the other side to the backing simultaneously squeezes them together. Here are some relevant photos of stuff I've done.

These osage sides are for a harp guitar where I didn't have a long enough piece for the harp arm side, so the seam is not over the tail block. This one has a scarf joint between the two sides, but I've been getting better results since switching to butt joint. Note that hide glue is very handy for this, so you can clean off all the squeeze out from gluing the first side to the backer.

Here's a tape hinge on a cutaway. Stick the tape on while the joint is open, so it will be pulled tight when the joint is closed.

And here's a finished tail seam done this way with butt joint.

Apply SuperSoft 2 with a spray bottle to both sides and stand vertically to drain. Allow to dry. Bend within 12 hours. Unlike thin veneer, there is no need to use cauls and weights to keep the side from wrinkling, and any color bleed is temporary, and stops once the wood has dried.

Rosewoods are easy bending woods and we generally don't bother with SuperSoft 2 for Brazilian, cocobolo, or other commonly used Dalbergias. I suspect that Mr. Carruth is right in wondering if a flaw in the side was at fault versus an atypically tough piece of rosewood.

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

Once I was blind, but now I can see! It's a miracle! Thank you so much.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I had to read that 5 times but I think I finally get it, tree's are tricky things. You have to really think spatially about it.

For those interested in this I also skimmed through this paper which goes into great detail: https://www.google.com/url?sa=t&rct=j&q ... o0uZqF8wEx

From that paper this line hit home:



That's exactly what happened, as soon as I applied pressure it cracked right through the 'top' side that was in tension.

That looks great! Thanks for the tip. That's probably what I will do with this guitar if I can continue the rest of the bend without issues. Supersoft should be here by Friday.

I would have thought that the scarf joint would be a better way to go too. The butt joint sure is more simple anyway.

Fortunate the wood for this project is not mine and was provided by a client who has dozens more sets in stock and is perfectly understanding that these things happen. I can see now why luthiers charge so much for their existing stock, that would have been one hell of an expensive mistake. But there are probably enough people out there that would accept a 'repair' like that. I mean hey, it's BRW right?

Good BRW is one of the easiest woods out there to bend. Much of what I see on the market now should have been made into coffee tables: it commands such a premium for guitars that they're scraping the bottom of the barrel.

Yeah I thought it should bend easily too. This stuff however is the good stuff, well except for the brashness, but it was cut in the 1960's and stored since that time. Fortunately the batch that I have doesn't look like it came from the same flitch so hopefully that was a rare one off. None the less, I'll use SS2 on it to be on the safe side.

OK, that was a bit harsh of me. Sorry Jay.

If the problem is brash fracture SS won't help: the wood is already broken. See if you can get a narrow test piece off one edge of the side you want to bend and try that. If it won't bend you'll need to laminate it.

^ that's a good idea. These boards are wide enough for this test too. In fact I cut off the extra to use as binding some day.