A while back someone created a thread about Bowclamps. There was a little discussion about them, but the general consensus was that nobody had tried them to give a reliable opinion about them. A reply was posted to that thread by Craig Feuerzeig of Zig Industries, the creator and maker of the Bowclamp system. He offered a set of the clamping cauls to be tested and reviewed by a member of NCwoodworker. D L Ames, took on the task, but due to a very busy work schedule has been unable to make the time to give them a good testing for review. He handed the set off to me to test and give y'all my thoughts and opinions about them. And they follow:
I have to admit that I was a little skeptical about the Bowclamp system. Not about the technique or method of using clamping cauls as it is a time proven method of distributing clamping pressure across a large area. Nor that they were well made items. But about the whole idea of buying curved pieces of wood for between $22-32 a set.
Well, I picked them up from D L on Saturday, and gave them a work over today. My first impression of the cauls as I removed them from the box was that they were definitely hand made, not by a CNC or any other automated process. You could see the tooling marks, a little burn from a router or shaper, and some slight chip-out from shaping. None of these thing affected the usability of the cauls, it just proved that Craig is a one man operation, and made each on himself.
Right off the bat I noticed that each set of cauls had their own unique curvature, definitely not random. I wanted to see if they would bow like they were designed to do so they could provide even pressure across the entire work piece.
Here's a shot of the cauls without clamps showing the curvature:
And with clamps applied closing up the gaps to a straight line:
After doing that I decided to put them to use in a panel glue up. I was making a cat bed, (as something to make that would require the use of the cauls). First I milled up three pieces of Lacewood that were to be the headboard of the bed. Normally I would use 3 or 4 Bessy clamps for this glue-up.
Here's a shot of the panels and cauls before clamping:
And after, showing very even (somewhat excessive for illustration purposes) glue squeeze out across the entire joint:
The cauls applied excellent pressure even though only two F-style clamps were being utilized.
The only draw back I found in this application was that I need to make 1/2 spacers to lift the panel so that it was in the center of the caul face to provide parallel pressure.
The next application I tried was a quick lamination of some Red Oak 5/4 stock to make the legs for the bed. Seeing as the panel was still drying in one set of the cauls I had to use my standard method of clamping for one and the cauls for the other.
Here's a 18 lamination using 3 Bessy clamps:
And here's a 26 lamination of the same stock using the 36 Bowclamp cauls:
Excellent glue squeeze out across the entire joint line:
The only issue I had during this application and others was the amount of screw travel to completely close the cauls. It takes almost the entire thread length of my standard F-style clamps...that's a lot of twisting.
I wish that I had a scientific method of testing how much pressure the cauls applied compared to a standard K-body style parallel jaw clamp. But I don't so I tried to break the joint after the glue had cured and the wood broke first...that's enough pressure in my book, it created a solid joint.
My overall impression of the Bowclamp caul system is that they are well designed, do what they are designed to do, and worth the money. A full set of 3 pairs of cauls 24, 36 & 48 runs about $130. If you bought the wood to make them, about 6 BF of 8/4 hard Maple, you would spend around $36. Then factor in 3-4 hours milling, squaring, dimensioning, routing, cutting sanding and finishing, and you would come out better buying them. If you value your time like I do. I much rather be making something fun than some high tech bowed sticks.
And the savings goes even farther because instead of having a arsenal of expensive parallel jaw clamps you can use many less and cheaper F-style clamps. That is something that I found to be quite advantageous as I have many of the cheaper F-style clamps that I don't use very often due to their tendency to not stay parallel and to mar the work piece with their small area of surface contact.
My biggest complaint is that I don't have 2 sets of any of the sizes to be able to utilize them to help keep a panel glue up flat, something which I think that they would also excel in doing.
I would like to thank Craig for the opportunity to test out his product and commend him on taking something very simple and refining it to perfection for a reasonable cost.
Also thanks to D L for being to busy to test them out...I will find lots of use for them in my shop. If anyone would like to give them a test run themselves, I would be more than happy to let you give them a try providing you post your thoughts also.
Respectfully submitted,
Dave
Bowclamp
02-04-2007, 11:57 PM
Nothing left to do but smile, smile, smile 
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