Caul question

[DC]

I'm trying to decide how the top edge of my new caul should be shaped/formed. The caul I use is 1 1/2" wide. I tried to make one out of 3/4" material to try to keep the heat from the back but then it wasn't stiff enough to take lateral bends out of the limbs. I'm thinking my next try I would use 1 1/2" wood but cut the corners off so the part that touches the bow is only 3/4" wide. Or, I could space blocks every 4-6" along the caul so that there is a gap between the bow and the caul. Which do you think would protect the back from burning best? I've tried Del's fence method and most of my staves are too wiggily for that.

[Tracker0721]

No help from me as I toasted mine getting it to bend on my 2x4 caul so I wanna hear suggestions too! Great topic idea.

[PlanB]

Wouldn't the hot air go around the sides to the back? Seems like you can't cool the back by exposing it. Shielding it somehow might work, but then you're back to thick wood for the caul.

If you could put two thin sheet aluminum vertical fences on the sides to concentrate heat in the center of the belly that might keep it away from the back.

Or straight radiant heat might be better, without hot air to flow around the bow. A campfire facing a bow. could do that from the side. Too bad there isn't a gun sized radiant heater.

[PlanB]

A long straight electric oven element used as a radiant heater above, might be long enough to do a whole limb at a time.

[Mo_coon-catcher]

I use 2x lumber, don't fence, and don't oil the wood and so far I havnt had any backs scorch. When heating I never stop moving the heat gun and make sure the gun is pointing square wth the bow and pointing a little towards the direction I am moving so the moving hot air moves in a more forward direction. I have broke a few by trying to heat them up too quickly and scorching the belly before its hot all the way through causing a crack when I try bending the bow before it's ready, if I'm distracted or rushing things. Those usually and up becoming short bows. But so far I havmt had any failures from scorching the back.

Kyle

[scp]

Does anyone here use the healting element like this: Strip Heater, 24 In. L, Silicone Rubber?

[Badger]

      Some of my cawls have a bottom shelf and some are just shaped like I want to shape the bow. I often need to align the limbs so the cawls with shelves I use primarily. I have scorched a few backs on shelf cawls. I keep my heat gun moving from one end of the limb to the other until the entire limb is hot, I never concentrate the heat in one area.  As long as I keep moving and keep the angle of my heat gun facing straight into the bow it isnt a problem. I tend to aim a little downward causing the heat to bounce off the shelf and go around the back of the bow scorching it.

[Selfbowman]

I use a different method somewhat. I feel that the heat when I straighten the kinks and twist in the bows at 5/8 to 3/4 inch thick on the limbs also gets the toasting done. All this happens in the straightening  process one inch at a time thru the entire limb length. I do scorch the entire limb but it all comes off during tiller. I also follow the scorching process with bar clamps compressing the wood as I go. Some say this is torchering the wood. I did not do the wood any good when I cut the tree earthier. I spend hours on that bench with that caul. My caul is a 2x4 with reflex and flipped tips. It does only one end at a time. I let it cool and do the other end of the bow. I have found this is easier cause the handles usualy has irregularities and can cause problems. Arvin

[DC]

This is what I came up with so far. The pieces are just screwed on so that it is adjustable. I just had a piece of 2x3 that I used for the base but it seems a little flexy for taking out lateral bends. I'm going to knock the corners off for heat control. In the second picture you can see the chunks of plywood I screw on where needed for taking out lateral bends. I think they replace a shelf, don't they? I also have no qualms about sawing a notch in a caul to make room for a knot or lump. I make the notch triangle shaped so it's easy to glue in a patch. A couple of strokes woth a rasp and it's good as new. 

PS I just realized that if I lay the 2x3 on its side it will be stiffer laterally and also lower so smaller clamps will work.

[DC]

Does anyone here use the healting element like this: Strip Heater, 24 In. L, Silicone Rubber?

This is interesting. It says it gets to 450 degrees. Kind of pricey though. Give it a try and get back to us

[Selfbowman]

DC those are for laminated bows if it's what I am thinking. And no in my oppinion it would not be good for selfbows. You crush those wires inside the rubber and they are toast. Arvin

[wizardgoat]

I use a 2X4 and haven't scorched any backs yet, even on snaky ones.
I do as badger, and point my heat gun just a little towards the tips.
In my mind, back scorching happens when your heat is coming straight in and bouncing off the caul into your bow. If you keep a slight angle the heat doesn't get trapped anywhere

[DC]

Up til now I've just used a 1 1/2" board and haven't had any trouble. Just trying to avoid any. maybe over thinking again

[Onebowonder]

I have on two occasions where I thought I'd be heating extensively used strips of wet terry cloth towel under the back of the bow to help mitigate excessive heat build up, but most of the time I don't bother.  I have also made a tin foil 'shield' to keep air and heat from flowing around the caul to toast out the back of the bow.  This is what I do if I'm trying to heat and move an exceptionally thick piece like a handle.

OneBow