Official Luthiers Forum!

I mentioned in another thread that I started a build from left over 6 x 6 cedar from building a deck.
All was going great until it was time to bend the sides, I need help,
I've never had a problem bending sides in Maple, east India rosewood, mahogany but cedar keeps breaking at the upper bout.
The sides are 1/4 sawn and thinned to .070. Bending with a Charles Fox style bender, the sandwich from the form out is .010 galvanized, craft paper, wood, craft paper .015 stainless, heating blanket, .015 stainless
bending at 285F cooling to around 130F then heating again to 285F and hold for 10 minutes.
I spritz with distilled water before the bend.

I'm thinking I need to do more than just spritz with water?

_________________
Say what you do, Do what you say.

Dave—

I can’t speak to cedar in particular, but in general, I find that hand bending over a bending iron gives me more control over giving the wood what it needs, where it needs it, in order to bend without breaking. If I were having the trouble you are having, I would give a bending iron a try. Just a thought.

I had some Indian Laurel that just would not bend in the way I normally bend. Only thing that worked was soaking the sides in hot water for 20-30 minutes. They then bent fine in my bender. Only wood I’ve ever needed to soak. BTW, I’ll not use Indian Laurel again.

I've never bent cedar, but I suggest two things to try.

1. Wood never stretches, it only compresses. Compression happens on the concave (inner) side. This is where the heat needs to go. Put the heat blanket under the wood.

2. The compression happens in the lignin, which is a plastic-like substance. Lignin has minimal melting below 140 C (284 F). Transition from a "glass" (rigid) state to rubbery happens at 170 C (338 F). Flow happens 180 C (356 F). So try at least 300 F, and go up to 350 F if necessary.

Greg

I use Super Soft veneer softener on woods that are prone to cracking while bending, like ebony. I works for me and I spray the wood until completely wet on both sides and let it soak in this while the blanket heats up, lay it on the blanket already on the bending machine and top it with a steel blanket and bend slowly.

I used to have problems with sides breaking in the upper bout on my bending form. I'd clamp the waist, pull in the lower bout to the bottom block and clamp that. By then the upper bout was pretty dry, so I'd spritz in on the under surface, and bend it. I finally realized that I was cooling off the upper bout with the fresh spritz, and tried spraying it before I bent the lower bout. That pretty well solved that problem.

Wet wood tends to fail first on the compression side. The sort of open grain structure you see on softwoods and (in a slightly different way) mahogany buckles when it's compressed. Softwoods, and even soft hardwoods, such as butternut, willow and poplar, and the softer mahoganies, can be hard to bend.

A friend once noticed that a black painted Gibson he owned had nice looking mahogany sides and back, and scraped it down to varnish it. It had a lot of crushing at the waist bend that didn't show on the inside.

Thanks for everyones input. This is what worked for me.
Decided to soak the wood in distilled water (I have some super soft 2 but I've had problems with it staining the wood, thats a presumption on my part) both sides were put in to soak the 1st side was left in for 2 hours it bent "good enough". The 2nd side soaked for over a day, on this side the heating blanket was moved down below the wood, and bent better than the first. It's my belief that the putting the blanket below the wood was the key.

Thanks again for everyones help.

_________________
Say what you do, Do what you say.