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Hello,

Just thought I would share my experiences with bending Blackheart Sassafras and ask a couple questions.

Setup:
- Fox style bender with silicon blanket and steel slats.
- BHS thickness to ~2mm
- Bending temp ~150c
- Bending time ~10mins
- Water - Just a light mist on each side. The wood soaked up the water very quickly.

I followed my normal bending procedure which is waist, lower then upper. I start with the waist and have the caul just putting enough pressure on the sandwich to hold it in place. I then turn 1/2 turn on the press screw every thirty seconds until the waist is almost down. Then do the lower bout using a similar approach. I slide the caul about an inch at a time every thirty seconds until bent. I go a bit slower in the areas where the bend is greatest. Then the upper, pretty much the same process. An inch every thirty seconds, slower in the tighter radius area. Next, I finish off the waist. I usually finish the bend in 10 - 11 mins.

Results:
The sides bent easily with very little spring back.


The sides clamped into the form nicely:


As you can see in the pics there is some scorching on the sides. I'm afraid this may not sand away.

Question: Do you think 150 was too high? Any guesses on if this will sand out?

Overall they bent nicely and were less stressful than my last build. Maybe I'm getting better with practice.

Thanks!
Brad






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Just a suggestion, but for me, 150 C is not really too high (Ive gone briefly to 160C), but the perhaps the bending's a bit slow, and your sides are drying out.
I sandwich my sides in damp wallpapering lining paper (seems to help with cupping) rather than spraying the sides now.
I start my waist as soon as I see steam (105-115?), crank steady to about 6/8mm shy of the waist, maybe 30 seconds? (by about 135/140 C)
Then lower bout, upper bout, then finish off the waist all quite quickly. Thermostat has started cutting in/out before then, and it only stays at 150 for a couple of minutes.
I'm done in about 3/4 minutes tops, then turn the heat down to 120C for 15 minutes, then cool.
Then heat again to 145/150 and turn down immediately to 120C again, 10 minutes to help "set" the bends and cool overnight.
Lignin in wood apparently starts to scorch about 150C (especially if it's dried out?), less time it spends therabouts the better.
Maybe sanding will help. doesn't look too bad.

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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.

Thanks, Colin. Your timing is close to some steps that I've read before, so I will speed things up a bit.

FWIW, this stuff smells like mesquite or BBQ sauce when it's heated.

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So far, I've only ruined one side while bending, and it was BHS. I went up to about 150°C and ended up with scorching that would not sand out. I purchased a replacement pair of sides (thanks Tim Spittle!) and bent at lower temps. BHS bends very easily and there's really no need to go much higher than 125°C.


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Oh, forgot to mention, I use large steel bulldog clips, to keep the "sandwich" together and help heat transfer as long as possible, taking then off when I need to fit the side to the form.

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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.

Good to know. I'll glue the blocks in tonight and try to sand it tomorrow. Fingers crossed.


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