Selfbow Caul

[bigcountry]

I think I am going to make me a Caul to put in reflex into staves.  And fix side to side bends on occasion.

Would 3" of reflex be too much? Figured after you got a bow heated up and clamped to it, it might only hold 1.5-2" depending on how much deflex it had before and how much heat, etc?

[Ryan Yoon]

I've been asking myself the exact same question.

[DCM]

Mine puts about 2" over 64" or so, more if the stave is longer.  It has worked well for me, having done perhaps a hundred projects over the years.  You can always add reflex by putting spacers between the stave and caul.  Less reflex is more tricky.  I like for the bend to be fairly progressive, that is modest near the handle and more pronounced the farther out the limb.  A good caul is time and money well spent imho.  I'd be lost without mine.  Most staves won't retain as much reflex as you caul might put, rather they tend to spring back a little.  So I'd say 3" isn't excessive at all.

[John Scifres]

Credit goes to Will Steffen for giving me this design/technique.  I believe it was Gary Davis that taught him in the first place but don't quote me on that.

To make a decent caul for about every situation, get a 2x6x72" board.  Dimensional framing pine is OK.  Hardwood is better.
 
Square the ends.  Divide the ends into 6 equal segments.  Number them from top to bottom, 0 for the bottom, 1, 2, 3, 4, 5.  Mark the top of the board every 6".  Number them from left to right, 0 for the left edge, 1, 2, 3, 4, 5.

Draw a line from the 1 on the end, to the 1 on the top.  From the 2 to the 2 and so on.

You will end up with something like the middle piece here.  Smooth out the line at the bottom and then cut it out.  Repeat for the other side.

 

This makes a nice progressively steeper reflex that will ends up with flat to slightly deflexed mid limbs and slightly flipped tips after your done tillering.  If you make a lot of bows that are shoreter than 66", you can make it shorter or do like I did and make a length adjustable caul.  Use your imagination.  That's what's so fun about this thing.

[Shaun]

Gary Davis has an article about his caul layout in the next issue of TradArchers World mag (sponsor) that will be out in Feb.

[Walt Francis]

I have used the same layout for my culls as John since 97 with great results.  I made my first couple with solid wood and they warped after a dozen or so bows, now I use LVL without any problems. Also, I my cull to be adjustable from 48" to 72" so I don't need several different culls taking up room in my shop/garage.  Here I a picture of my cull with the inserts setting on top (the inserts drop in to place when the form is lengthened).  

 

[bigcountry]

Holy cow Walt, thats the cadillac of cauls

[bigcountry]

John, I guess one could also use 2X4 for something less aggressive?

[skeaterbait]

Mine is basically the same thing as John but has a smoother arc through the entire limb but still progressive.

I used a 2x6 to make it.

 

[RB]

Yep, over 6", down 1/2" (or over 3" and down 1/4"). 3" of reflex won't last very long....

Note: If you making stiff handle bows, allow for length of handle + fades (say 7-8") by keeping the top center of the 2x6 dead flat...then start your increments downward on the ends.

[bigcountry]

Thanks Skeeter, that looks a lot less agressive to me.

[dutchwarbow]

I prefer scifres caul,

nice low-string angle profile  :D

Nick

[skeaterbait]

Originally posted by dutchwarbow:
I prefer scifres caul,

nice low-string angle profile   :D  

Nick

That's why we have different colored cars.    

[Lee Slikkers]

Originally posted by Walt Francis:
I have used the same layout for my culls as John since 97 with great results.  I made my first couple with solid wood and they warped after a dozen or so bows, now I use LVL without any problems. Also, I my cull to be adjustable from 48" to 72" so I don't need several different culls taking up room in my shop/garage.  Here I a picture of my cull with the inserts setting on top (the inserts drop in to place when the form is lengthened).  

 

Greeting Walt, where would someone find a "pattern" or plan for making a caul like the one you have pictured here?

Many thanks,

[Osagetree]

Nice caul Walt. You must be fairly tall?  

[Walt Francis]

Lee, I use the same layout as John.

I needed one that would last and it has worked great.

Joe, I am not tall, just had have limited space and a few ladders so I make use of any open space on the walls.  I figured if it were above a door, I would not have to move anything when it was needed.

John, I got the design from the other site, probably either Will or Gary (can’t remember which one) about the same time as the whitewood - Osage war that spurred the creation of MoJam.

Here are some pictures of the caul in use on Sunday and the stave before and after.  It is 57” x 1 ½”, that has just started to bend (about 3”) and will get elk or bison back sinew inn   the next few days

Roughed out:
 

Before heating:
 

Heated and clamped up:
 

After it came off the caul:
 

The center of the tips arenow 1/8" from aligning through the center of the handle

[KellyG]

That is simply magic I say, you are an Osage wizard Walt.

[Aram]

Wow! That is magic! Do you use a wedge at the handle to allow you to bend the tips past the alignment point? I would have thought they would recover more than the 1/8th after being released. Can dry heat really do that?
( I imagine you use dry heat in addition to the coffee mug steam bending.        :p    )

[Walt Francis]

Aram, I took the right limb about 1/8” past my alignment marks and it came back a total of ¼”.  I did use a couple of shims between the side of the limb and the form to control the bending where needed.  A key to minimize the “Spring Back” is to continue/maintain heating the limb after it is clamped into position, and then gradually stop heating that area while heating the adjoining area.

I was pushing the limits on the tips with dry heat; the right tip started to lift a splinter at a small knot three inches from the end, in the non-working area, but should be fine when it is reduced to size.  I have a separate caul for bending tips that are more radical.  When using that caul I use Brad Merkel’s technique of boiling the limb tips in a pot of water and using a metal strap.  As a side note, many people use different types of oil when using dry heat but I had so-so results using that method.  At MoJam in 2002, Gary Davis told me to try heating the staves without oil, which worked well, and I have done it that way since.

[snag]

Brilliant Walt! Looks like another trip to the lumberyard and some LVL for another project.