reflex caul

[billmac]

Has anyone made a one-size-fits-all caul for reflexing staves?  I'm wondering what dimensions and measurements to use.  I don't necessarily want to recurve the ends, I would just like to use the heat gun to correct deflex in a number of staves of varied species and lengths.

[GregB]

Pappy and I have several different cauls with varying amount of reflex. They were all designed to handle a 68" bow or less. We have smaller cauls for recurving tips. As for a one caul fits all, I would suggest you decide how much initial reflex you'd like to have in the roughed in bow prior to tillering and make you one accordingly. Remember that the bow won't usually hold all the reflex after removing it from the caul. Osage usually holds more then hickory and hhb.

[billmac]

Greg,

Thanks.  I was thinking it would be nice to have about 3" of reflex before tillering, but I'm wide open to suggestions.  Does that mean I should induce about 6" when heating?  Will a typical stave (whitewoods) lose half?  I guess a one-size-fits-all isn't really practical is it, since we measure reflex at the tips?

[Skeaterbait]

This is the pattern I used to make my caul, you could probably vary the aggression of the reflex by altering the measurements a bit but I have never toyed with that.
I used a single 2x8 for mine but if I had to make another I might consider putting two of them side by side to give it more width.




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[radius]

better to us plywood. 2 or 3 layers of 3/4 " ply will get you a dimensionally stable bending form which will not warp or  twist or cup as it ages

to get the top surface perfect, pass it over a jointer.  Then attach a little plywood pad, about 2" by 6", to the bottom, at each end, and one in the center.  These keep the form stable and prevent it from rocking back and forth while you're trying to glue up your bows on it.  I used yellow glue to fasten mine together.  I used screws as clamps, and then removed them all once the glue had set, so I could drill clamp holes without worrying about hitting metal.

[GregB]

Using dry heat I'd say white would probably loses about half of the reflex right off the form unless maybe if you really throw the heat to it. Osage tends to keep more of the reflex.

One thing to keep in mind about a caul is that it's good for a lot more then only adding reflex. We use them to remove propellor, get a more constant curve in the limbs, tweaking limbs sideways, etc.. Especially when working with osage you can have a lot of challenges in a stave that would make it a lot more difficult to make a bow without using a caul. I have seen the wood heated over a stove burner, and then while wearing gloves and a thick piece of leather on your knee you can remove propellor, and correct problems in a limb...even add reflex. Little more difficult to judge though.