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So, from time to time I have to chuck a set of Khaya or mahogany due to compression marks from bending. Is there a way to lessen this effect?

You could try bending them a bit thinner and slower (more thoroughly heated). Have you tried using supersoft veneer conditioner?

No, should probably get some...

Fabric softener for clothes works too.

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nigel

http://www.theluthierblog.com

Oh reeeaaalllyyyy....seems to be easier to find than Supersoft in Canada...

Are you talking about the waist? If so, don't crank too much on the screw. If you were to overcut the bending form a bit at the waist you could turn until it hit home and then back it off some.

If you do try the fabric softener, please let me know how it works.

Are you talking about the slick flat areas where the waist caul was that looks like they were pressed really hard, or the faceted looking things that look like some breakage inside the wood?

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Pat

Facets...

Thanks for coming by the other day, btw...

Yep ribbon figured Khaya is a bugger! The interlinked grain seems to go off in all directions. Water instantly causes ripples, ripples cause uneven heat lifting off the source and actually makes the material stiffer. So thin to .075" (same as the Martin factory) high heat, pre-conditioning with SS sounds like a good idea.

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Ken Cierp

http://www.kennethmichaelguitars.com/

I use SS any time I'm bending Mahogany of any type. I spritz the wood down the night before and leave the wood wrapped in a plastic bag. I use minimal water and slowly crank the waist down when bending. Once I get the waist down I back the screw off slightly. No matter how hard I try I still end up with some compression on certain sets. It is of course worse on tight waisted OMs and 000s.

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Josh House

Canadian Luthier Supply
http://www.canadianluthiersupply.com
https://www.facebook.com/canadianluthiersupply?ref=hl
House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

Yep, a Martin 00 at the waist.

Josh, where did you you get your SS?

I bought it from the US, 1 gallon about 8 years ago and still have close to half of it left. Yes it was expensive, but considering how long it lasts and spreading the cost out over something like 150-200+ guitars doesn't make it seem so bad. I only use it on Mahogany or figured woods that I think might be tricky to bend. I know there are plenty of places in Canada that sell veneer softeners (most veneer suppliers stock it). As I've only ever used SS I have no idea how it compares to other softeners or to fabric softener (which is an interesting idea). I remember reading about SS that the effects of the softener on the wood are totally gone after about 7 days. I assume that it is probably less after the side is "cooked" in the bending process. My only concern with something like fabric softener is whether there are any lasting effects on the wood. My guess is not, since guys like Nigel are using it. I just have nothing to document the affect of fabric softener on wood. Maybe fabric softener and veneer softener are chemically similar? I just don't know, and have never had a need to check.

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Josh House

Canadian Luthier Supply
http://www.canadianluthiersupply.com
https://www.facebook.com/canadianluthiersupply?ref=hl
House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

I bought some of the veneer softener from A&M. I used it for a set of walnut practice sides, and a set of black limba. With my very limited experience, I can't say if it helped one way or the other.
If I take a trip to the USA this year, I'll try to find some SSII.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

I was looking at the A&M veneer softener and wondering if it's a good enough product...

I had emailed them a while back asking about it, and they replied that they had guitar builders tell them that it worked well for bending sides.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Only one way to find out I guess...

Thanks for having me. Nice work!

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Pat

Thanks!

Just to follow up, I machine bent several pairs of Khaya sides yesterday with no issues (having damaged a few pairs in the past) Here is the process - it's simple enough.

1. Prebent the waist on the pipe with a strap.
2. Lightly sprayed water/fabric softener mix both sides of the side.
3. Wrapped in brown paper, blanket above, placed between the slats.
4. Placed in machine, switched on timer and temp control to full (its an old LMI control)
5. Slowly cranked the waist down - a turn every minute or so until the shoe was about 5mm from the bottom.
6. Turned the heat down to half way and slowly worked the top bout using a scrap of ply as a caul. This felt much more like bending by hand than when rosewood is in the machine - I was really feeling for "give" and keeping the hand pressure very constant - I don't have spring loaded cauls on my machine. Then clamped the top bout in place.
7. Repeated the same process for the lower bout.
8. Slowly brought the waist in.



No issues. I just took a little more time than with rosewood and worked less wet.

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nigel

http://www.theluthierblog.com