To make a caul

[Tradslinger]

I understand the reason and function of a caul in terms of manipulating the wood to do what we want it to do. And that there are numerous kinds and styles of cauls for different results. I can make one easy enough when I get around to it just for the tips but... So I watched this video of Beckum outdoors where they took a just cut tree (hickory) split it and made two staves out it. Then rough formed one very quickly before clamping it down still wet and fresh to a caul. They went ahead and used heat to treat the wood while clamped to the caul, then later fire harden the stave still in the caul. So this caul was a full size caul for the full length and the staves were with a "flexable" handle, I guess like a Bendy style. another was simply roughed out and allowed to dry slower while clamped to another similar caul. They claimed that this would take out most of the twists etc as well as allowing it to dry quicker without cracks. The rough forming and clamping to a caul to dry that way intriged me. My question is what length should this caul be? I plan to build 64" bows, hickory first and mainly since it is so easy to find here in Ark. I plan to use 2x6's, doubled up. Mainly looking for a slow good reflex caul but may have to make a reflex eflex caul as well for a Bendy attempt. Making a caul, it all sounds simple enough, just getting a good smooth flow of the bends to get better performance out of your bow. The fire hardening thing has always made sense to me from tools that I have seen made out of hickory. I believe that one is seeking a graceful caul.

[Dances with squirrels]

I make mine about 6' long. I like to cut my staves that length so I have room for layout options.

My two main selfbow reflexing cauls are 2" wide and made of hardwood, one oak, one ash. They have 1/8" rubber covering their surface where the stave will rest. This helps keep from smashing the wood on the staves back if more clamping pressure is needed to make a serious correction. It also protects the caul somewhat from divots and such when clamping down staves. They've held up very well over the years.

I wouldn't use softwood lumber for it, but that's just me.

[Tradslinger]

I make mine about 6' long. I like to cut my staves that length so I have room for layout options.

My two main selfbow reflexing cauls are 2" wide and made of hardwood, one oak, one ash. They have 1/8" rubber covering their surface where the stave will rest. This helps keep from smashing the wood on the staves back if more clamping pressure is needed to make a serious correction. It also protects the caul somewhat from divots and such when clamping down staves. They've held up very well over the years.

I wouldn't use softwood lumber for it, but that's just me.

thanks for the info. I was looking at having a liner in between. flashing plus rubber strip

[Eric Krewson]

Mine are short, I do one limb at a time on the same caul. I use dry heat and it is easier to keep one limb hot than both of them at the same time. I make my cauls out of scrap plywood.




 

[Selfbowman]

Eric what is the board for that’s higher in the back of the caul for ?

[RyanY]

Eric, is it safe to use plywood? My understanding is they often use formaldehyde based glues so I’ve been hesitant about using them for heat treating cauls.

[Selfbowman]

Ryan I use a plywood glue lam and have for about a hundred bows. Has not killed me yet. My shop is well ventilated though. Arvin

[Pat B]

I have a few cauls and the simplest one is a 2x4 with a radius cut from tip to tip.As long as the board is straight and untwisted it will be OK. I have a couple of others, one for just one limb reflex and one a couple for recurves(one tip at a time)of different degrees. Making the curve of the caul is important so when the bow comes off the caul it is straight and the limbs bent evenly. I remove twists and lateral bends from staves with these same cauls by using clamp and small wood wedges. The wedges are used to remove twists by clamping the stave with the wedge under the side closest to the caul. For lateral bends I secure a clamp hard to the caul and drive a wedge against it to force the stave in the direction I want it to go.
 For a full stave correction I start by clamping the stave to the caul securely(at least 2 clamps)at the handle, back down and start heating the first 6" after the handle and clamp it down. If twists are present I use a wedge under the back and clamp the other side(be sure to pad your clamps to prevent denting the hot wood). Once that 6" is done I move on to the next 6" and so on down that limb. If there is a lateral bend I fasten a clamp to the caul and drive a wedge to force the limb over to straighten out that lateral bend. While I'm doing this I heat well. After the limb has been corrected and it is still on the caul I go back over each limb from the handle out the entire limb with heat then start on the other limb. After that entire limb has been corrected I reheat the entire bow, starting at the handle and go out each limb making sure I get good heat penetration(I look for color change) I leave the bow on the caul over night to cool completely.
 On staves with drastic bends or twists I use cooking oil on the limb at the time of heating. I think this oil helps the heat penetrate better and I think it holds the heat longer. 
There are as many methods as there are people building bows so find what works best for you.  Also, I don't think I would use plywood unless reinforced with solid wood. Not only can the off gassing be a problem but the heat could delaminate the plywood.

[bassman]

I use para lams loaded with bad stuff. When heat treating if I don't wear a good respirator I get an instant head ache.

[Tradslinger]

and this why you ask, getting all kinds of info. I plan to make a short caul or two just for tips. I am wanting a caul for a 64" bow mainly because that is my favorite length. I don't have access to hardwood 2x6s, just the pine ones. These will be for self bows only. I am wanting to take a fresh cut stave that has also been roughed out and clamp it to the caul to both dry and be heat treated on until it is dry enough to work. hoping that this will also help in creating a reflex as well as taking out any twists. may not work but I want to try it.

[Eric Krewson]

The side rail is for aligning and straightening, gives me something to put a C clamp on in the same plane as the bow limb for pulling the limb sideways.

[Pat B]

Most of my cauls are pine or fir 2x4s from Lowe's. I have one maple one for a single limb. it came from a scrap pile of a woodworker and I use as it layed there with no modifications. My recurve form was another scrap of oak with the radius cut by me. You don't need to spend much money for your cauls just be sure it is true.

[Eric Krewson]

For simple reflex I tape a string to the floor, and make a giant compass with a pencil on the other end to draw the arc of my caul. No particular formula, I have several, each has more or less reflex depending on how I drew them and how I plan to use them. Hard dense wood needs less reflex to end up with straight limbs or a little reflex after shoot in, particularly after heat treating. I give whimpey wood more reflex from the get go.

I use a low arc caul for secondary heat treating of BBOs after shooting them in if I am not impressed with their performance. I have turned so-so bows into top of the line bows with these after shoot in treatments and the correction doesn't pull out over time.

Of course I have RD cauls and static recurve cauls that I either freehand or in the case of the statics I use a big container lid as a drawing guide.