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  #1  
Old 04-03-2020, 10:24 AM
kmanuele kmanuele is offline
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Default Super Soft II for Khaya sides?

I have a set of Khaya sides that simply won't bend. Been in the bender twice, first at 320 and then 350 degrees, but no luck. Initially thicknessed to 2.1mm (0.083). After the first side was unsuccessful, reduced the second side to 1.85mm (0.073), still no good.

Both pieces are quite noticeably stiff, even at the thinner dimension.

I would like to salvage these (despite the thickness difference), as they have good figure - and a back waiting for them.

Can anyone with experience with Super Soft II (or Windex) provide some comments / advice, and how this is done?

thanks

Kevin
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  #2  
Old 04-03-2020, 11:24 AM
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I've been using super soft for a few years now. It all started when I was bending a set of black walnut for a cutaway guitar, I broke a couple sides trying to make the bend , so I decided it was time to pay up for the SS. The first try after using SS worked wonderfully. I can't imagine NOT using it now for a set that I think might give me some trouble. It's not cheap but I think it is worth it, I think of it as insurance.
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Old 04-03-2020, 11:42 AM
redir redir is offline
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I think maybe it was on the OLF but there was a recent conversation about this where the OP said that SS2 seemed to do nothing and I agreed with him. I don't notice SS2 do anything what so ever. The conversation evolved into people thinking that it woks well on some wood and does nothing for other wood and the wood that it tends to do well on is wood that is already easy to bend like walnut and mahogany.

I can tell ya it don't do Jack for BRW.
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Old 04-03-2020, 02:17 PM
charles Tauber charles Tauber is offline
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Quote:
Originally Posted by kmanuele View Post
I have a set of Khaya sides that simply won't bend. Been in the bender twice, first at 320 and then 350 degrees, but no luck.
What do you mean when you say it "simply won't bend"? It breaks before bending?

Khaya is a relatively soft wood similar to mahogany, which bends easily. I haven't tried bending Khaya, but have worked with it fairly extensively for other purposes.

I recently bent black walnut and Spanish cedar without incident, having never used Super Soft. I'd expect the cedar to be similar to Khaya.
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Old 04-03-2020, 02:29 PM
kmanuele kmanuele is offline
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Charles:

re: Won't bend. They come out of the bender with significant spring back, and too much inherent stiffness to force into the form. I've noticed that after sitting on the bench for 24 hours they have now relaxed a lot too.

It seems they are just one of those sets that have way too much stiffness.

Another Khaya set I bent a couple weeks ago, thinned to 2.2 mm, bent without a problem.
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Old 04-03-2020, 05:11 PM
charles Tauber charles Tauber is offline
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Quote:
Originally Posted by kmanuele View Post
Another Khaya set I bent a couple weeks ago, thinned to 2.2 mm, bent without a problem.
Same piece of wood or a different one? Sometimes kiln dried vs. air dried can be much more difficult to bend.
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Old 04-04-2020, 05:49 PM
kmanuele kmanuele is offline
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Charles: Presumably the same, from a well known respected tone wood vendor.
I am wondering if my wood is too dry. Been stored for months, but shop humidity these days is about 35%.
Not sure about bend temperature either, though 320 - 350 seems to be common.
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Old 04-04-2020, 07:00 PM
charles Tauber charles Tauber is offline
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Do you bend it dry, without surface wetting/soaking?
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Old 04-05-2020, 08:21 AM
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Quote:
Originally Posted by charles Tauber View Post
Do you bend it dry, without surface wetting/soaking?
Kmanuele, I think it would be a good idea to outline your bending technique in full so everyone is on the same page. I lightly spray both sides of the wood with water or SS, wrap in aluminum foil then bend in a Fox style bender in the 320 to 350 degree range. Is this along the lines of your bending or are you using different techniques?
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Old 04-05-2020, 12:39 PM
kmanuele kmanuele is offline
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Bill;
Essentially the same as yours. I use a modified Blues Creek fox bender with 1 kW blanket and a voltage controller. Wood is thinned to 2.2 mm (maximum), dampened slightly, placed between 2 sheets of Kraft paper. Then the sandwich from top: SS sheet, wood/paper, heat blanket, SS sheet. Place in bender without any waist pressure. Install two thermocouples, one at waist, another at a bout. Lower waist ram a bit to get slight contact between blanket, wood, and TK. Voltage control is pre-set to heat blanket to 320, measured at waist TK. Bend waist slowly until fully compressed, then bouts. let sit for 5 minutes. turn off. Remove when temps fall to 120 or so. I've tried to fix the stubborn sides by reheating to 350, but no success. Would like to salvage those, somehow (SS2?). But also need learn what is happening here, unless just bad luck with tempermental mahogany.
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Old 04-05-2020, 01:25 PM
redir redir is offline
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I just bought a Blues Creek bender last week and bent 5 various sets on it before tackling a BRW set. All 5 sets bent like a charm then I did the BRW and the spring back was huge. I put it back in the machine and it made it better but I still ended up having to bend it on a hot pipe. I followed the same procedure as yours to which John Hall outlines in his videos.

I think you just have a difficult set of wood there. It's not uncommon from what I understand to have to re-bend wood on a pipe after coming out of the machine.
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Old 04-05-2020, 03:15 PM
charles Tauber charles Tauber is offline
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Quote:
Originally Posted by redir View Post
It's not uncommon from what I understand to have to re-bend wood on a pipe after coming out of the machine.
It isn't uncommon.

One thing that can be done to reduce spring-back is to over-bend the upper and lower bout curves and the waist. That requires exaggerating the curves in the bending form.
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Old 04-05-2020, 07:11 PM
redir redir is offline
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Quote:
Originally Posted by charles Tauber View Post
It isn't uncommon.

One thing that can be done to reduce spring-back is to over-bend the upper and lower bout curves and the waist. That requires exaggerating the curves in the bending form.
When thinking about making my own forms for the machine I just got, that is what I was thinking. To exaggerate the bend at the head and tail blocks so that they come in maybe one centimeter. If they don't spring back then it probably would not be a problem anyway and if they do then they would probably be spot on.
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Old 04-06-2020, 05:26 AM
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Quote:
Originally Posted by kmanuele View Post
Bill;
Essentially the same as yours. I use a modified Blues Creek fox bender with 1 kW blanket and a voltage controller. Wood is thinned to 2.2 mm (maximum), dampened slightly, placed between 2 sheets of Kraft paper. Then the sandwich from top: SS sheet, wood/paper, heat blanket, SS sheet. Place in bender without any waist pressure. Install two thermocouples, one at waist, another at a bout. Lower waist ram a bit to get slight contact between blanket, wood, and TK. Voltage control is pre-set to heat blanket to 320, measured at waist TK. Bend waist slowly until fully compressed, then bouts. let sit for 5 minutes. turn off. Remove when temps fall to 120 or so. I've tried to fix the stubborn sides by reheating to 350, but no success. Would like to salvage those, somehow (SS2?). But also need learn what is happening here, unless just bad luck with tempermental mahogany.
Try using a foil wrap instead of paper, I believe it will hold in the moisture as steam longer than the craft paper, that may help.
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Old 04-07-2020, 10:47 AM
kmanuele kmanuele is offline
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Thanks, that helped, but more detail:

Besides the Khaya sides, I was also bending Honduran mahogany, and one of those pieces refused to bend also -- so 3 out of 4.

Reheating at higher temps did not work. Did an experiment: sprayed one piece with Zep glass cleaner (a Windex clone), let sit for an hour, put in the bender as before. No luck.

Tried your aluminum wrap, spritz with plain water. This showed some improvement (though I only slightly wet the wood).

Then sprayed thoroughly with Zep, wrapped with aluminum while still wet. Perfect bend.

Did the same with the other 2, and success also.

Not sure if it was Zep, or just that the wood was more wetted.

I've noted in Taylor's factory tour that when they bend their sides "dry", water gets extracted and wets the paper. As I mentioned, my shop is at 35% humidity now, and was probably lower during the winter. So there are clues in here, somewhere.

Thanks for all the comments.

Kevin
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