Thursday, June 14, 2007

Bending sides and mold making....

Today I spent some time getting the side mold made. I first drew out the four sections on some MDF, then rough cut the shape using my band saw. After that, I used my router the same way I did when making the bending form to fine tune the mold pieces. Then I made a bunch of spacers and assembled the two halves. I drilled a hole through the ends for a piece of threaded rod and nuts to hold the whole thing together.

Once that was done, I scrounged around to get a 1000W dimmer and timer switch to make a controller for my bender blanket. I quickly assembled the whole thing so it has a double outlet. One half if controlled by the timer, and the other half is controlled by both the timer and the dimmer. That way I can plug the blanket in the dimmed half, and plug the lights in the un-dimmed half while bending.

It was time to start bending. I did make one small change to my bender from the other ones, I caul on springs that I could use to slide along the slats and push the wood tight to the bender while it is being formed. I didn't have this before but I figured that since I was using a blanket now, it would be a lot hotter requiring something other than my hand to push it down with. After I decided what side I wanted to see on the sides, I marked the waist locations on them. I read several posts online regarding a method that seems to work very well for bending wood. People have been spritzing the wood with water, and then getting the kraft paper wet and wrapping the wood. I decided to give this a try. Essentially this keeps the wood from getting too wet, yet the water in the paper will steam out and help loosen the wood. After getting the paper wet, and spraying the wood I wrapped it all up, sandwiched it between stainless steel slats with the blanket on top. I set it all on the bender, set the waist clamp and turned the blanket on. I had already pre-heated the box with the light bulbs. Within about 1 minute, steam started showing and the wood actually started to sag around the lower bout under it's own weight. I was amazed. I clamped the waist to withing about 1/2" from complete, the ran the spring caul around the lower bout. I clamped that, moved the springs to the upper bout and did the same thing. Once that was done I finished the waist clamp which pulled everything tight to the mold. I turned the blanket off, and then moved the light bulb cord to the dimmed plug. I dimmed the bulbs to get the bender down to 200 degrees and let it sit at that temp for 20 minutes. Then I turned it off and let it sit an hour. I was thrilled when I removed the sides and there was virtually no spring back. It went very well. The second side went as well as the first. This is my first bend using the blanket. I have to say, it really makes things go much easier. I like it a lot.

I now have the sided clamped in the mold waiting for the next step, end and neck blocks.

The four side mold pieces, one with the template on it.

I just used scraps as spacers between the two pieces to add thickness.

When assembling these, it is very important that they are square to the table which makes the entire mold perfectly straight.

I was hoping that this break in the sapwood would line up perfectly with the waist. It is close, but not perfect. Oh well, it should still look good.

Here you can see the wood wrapped in damp kraft paper. It is double wrapped so the inside piece is wetter.

Whoops, the pictures are out of order. Here is the completed mold.

Back to bending. Here you can see all the pieces sandwiched together, and the spring caul I made. It pivots on the mold and once the waist is clamped down, I slid it down around the lower bout. The caul is under spring tension. It worked very well and kept my hand from burning!

The first side all bent and cooling down.

About an hour later after taking it off the bender. Look, no spring back!

The first side in the form.

This wood is really purple and really makes a lot of oil when it bends!

Both sides in the form.

One thing I noticed is that the wood got a lot darker after bending. I am hoping that it will lighten up a little bit with some sanding and scraping. I really don't want it to be so much darker than the back. I really like the wild look of this wood though.


Rodrigo said...

Oi, achei teu blog pelo google tá bem interessante gostei desse post. Quando der dá uma passada pelo meu blog, é sobre camisetas personalizadas, mostra passo a passo como criar uma camiseta personalizada bem maneira. Até mais.

David said...

Hi Rodrigo,

Sorry but I can't read what you posted. Could you possibly write it in english? I have this funny feeling this might be spam though....