Bow clamp clamping cauls - Page 2

Bowclamp clamping cauls reviewed · 02-04-2007, 10:57 PM

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

Alan in Little Washington · 02-05-2007, 07:59 PM

Do they have a durable and smooth enough finish so glue doesn't stick or can be easily scraped off? If I hadn't paid about 1/2 of what the Bow Clamps cost for my Besseys (during the Bessey frenzies of a few years) I'd think about buying a couple.

I still would like to see a test with a number of pressure strain gauges spaced along the joint. And also do the engineering and see what it costs to make my own- the curve should be easy to determine and draw with a computer and CAD program.

NCPete · 02-05-2007, 08:59 PM

Hey, he is over 30!!! He can't be trusted!

DaveO · 02-05-2007, 09:55 PM

Originally Posted by Alan in Little Washington

Do they have a durable and smooth enough finish so glue doesn't stick or can be easily scraped off? If I hadn't paid about 1/2 of what the Bow Clamps cost for my Besseys (during the Bessey frenzies of a few years) I'd think about buying a couple.

I still would like to see a test with a number of pressure strain gages spaced along the joint. And also do the engineering and see what it costs to make my own- the curve should be easy to determine and draw with a computer and CAD program.

Alan, I e-mailed with Craig and asked about the pressure that they applied and if it was comparable to a clamp like a Bessey. He told me that in the design his aim was for 150 psi across the entire length of the caul. He also has some engineering type test with a material that is compressed and the measured with calipers to show that the pressure is even across the whole length.
They are waxed to prevent glue from sticking, but if I was to use them as cauls that would be in direct contact with a glue line (like keeping a panel flat) I would consider putting some packing tape over the faces just as an extra precaution.

I don't think that the design would be to hard to duplicate by following the original, but I still think that it would be more work than it's worth.
Dave

mkepke · 02-05-2007, 10:21 PM

I'm sorry, you lost me at:

"I was making a cat bed out of lacewood".

-Mark

DaveO · 02-05-2007, 10:27 PM

OK, let's call it a doll bed for my daughter, as I don't think that the cat will sleep in it without some adhesive persuasion. Although I did build a cat tree and they took to that like a fish to water.
I just needed something to make

...I can't just glue boards together for no reason, and the cat bed was my wifes suggestion. Wife wants = more shop time with less grief

Dave

cskipper · 02-05-2007, 10:35 PM

Originally Posted by DaveO

...I can't just glue boards together for no reason,
Dave

Dave, youi can send me that glued-up wood! It'd make some pretty trivets....

DavidF · 02-13-2007, 12:44 PM

Just a quick impression of the Bow clamp clamping cauls as DaveO did a fine job in his review.

My first thoughts when I started to use these was how well made they were and how nice they felt! My project was 19" long and 3 x 5" wide cherry being glued up into a panel. I had to use a 1/2" spacer under the panels to lift the pieces up sufficiently to allow the cauls to sit centred on the edges. No problem, just used 1/2 MDF under plastic sheet to prevent sticking. Got two of my cheapo F clamps and started clamping. Here is were I came across the first little difficulty. The boards were not sitting level and because of the pressure in the centre being so much greater than the outsides; I had to remove a lot of the end load in order to adjust the boards; adjusting them level was done with a dead blow, but I also wanted to shift them sideways. When I had removed enough pressure to do this I had lost some of the stability of the whole setup and the levels changed again. Not a serious flaw, but still.. Then I had a small "explosion" The cauls had shifted all the way to one side and therefore one of my clamps was near the ends of my boards, the other was 4 or 5 inches off the other end. I released a little too much pressure off the close in clamp and all **** broke loose as the clamp slip out of the grooves and the because pressure was still being applied at the other end...well you know what happened! glued up boards all over the place, cauls, clamps.. etc... So lesson learned - don't use cauls that are overly long for the project in hand. At that point I didn't like them! The I continued and found the next slight problem. My clamps are cheap as I said and with the 24" caul I was using I couldn't quite get the caul closed up right on the ends because my clamp was bending instead! This left a tiny gap on one end. With a normal setup I could have closed that gap with the clamp without the additional force required to overcome the bend in the caul. Lesson learned - use better clamps! However I tried I could not get the panel to sit quite flat when clamped up even though the joints were good; perhaps a bigger spacer would have allowed my to juggle the position of the caul to adjust for this. Top pressure from more straight cauls fixed that.

At the end of clamping up 6 sets of panels I would buy these for my shop. Not sure whether the 24" is strictly necessary because it only takes 3 clamps to clamp that distance anyway, but the 36" would be nice. Over all I like them. I would like to try the woodcraft panel clamps that apply downward pressure as well with a user supplied 2 x 2.

You can see the clamp bending here.

And the small gap. Changing to a standard bar clamp not an F clamp fixed the problem.

The woodcraft system. I would like to try this.

WOODCRAFT Clamping System

cpowell · 02-13-2007, 01:58 PM

Thanks for the review. I wonder how much force is applied at the point that the cauls are perfectly flat against the panel sides?

Sounds like you handled the "explosion" well. I get a little edgy when a glue up heads South.

Chuck

DavidF · 02-13-2007, 02:06 PM

Originally Posted by cpowell

Thanks for the review. I wonder how much force is applied at the point that the cauls are perfectly flat against the panel sides?

Sounds like you handled the "explosion" well. I get a little edgy when a glue up heads South.

Chuck

I do tend to think that the amount of bow on the 24" is a little too much. My clamps were bending to close the gap and I know the edge joints were good so without the cauls I would have needed minimal pressure to bring the joint up. Heaven only knows how much force was being applied in the middle!

The only problem with the "explosion" was that all the time I was fiddling the glue was drying out

tonyps · 02-13-2007, 10:25 PM

Evening,
I saw this product a while back and have been waiting for someone to put a pair of em through the wringer.....it seems like a pair of em would be well worth it if you glue up boards on a regualr basis. It seems like it would sure reduce the number of clamps needed for this type of operation...
Do you know the cost and different lengths available?
Thanks,

Tony ...

02-13-2007, 10:46 PM

So Dave - are they really all that?

DaveO · 02-14-2007, 07:16 AM

Originally Posted by tonyps

Do you know the cost and different lengths available?
Thanks,

Tony ...

Tony and all. I merge this thread with the review that I did, where I list the costs and sizes, so someone looking for the information wouldn't have to look in several places.
DavidF, thanks for putting your spin on the review, anyone else that would like to give them a try just let me know.

Dave

Alan in Little Washington · 02-14-2007, 09:42 AM

I got to thinking about my previous question about the Bow Clamp's ability to apply even pressure across the length of a glue up and testing with strain gauges- would be nice to know (since I am a skeptic about manufacturer's claims), but I doubt anyone puts even pressure across a glue up with clamps of any sort- you just tighten until it feels right.

What is lacking with the Bow Clamp is the ability to put more or less pressure. If you need to put more pressure in one area (first you didn't do a good job jointing or had some post jointing warp- wouldn't be the first time

) you can add a clamp on top of the Bow Clamp. Of course then you are changing the dynamics of it- so why do you need it at all. Second, I often release pressure on one or two clamps in a long edge glue up to make it easier to realign the faces. As DavidF found out you can't do that very easily with Bow clamps. Also, it would be hard to run cauls across the face of a glueup unless they are shorter than the width of ther glue up, since the Bow Clamps would be in the way. It might be better to use regular clamps on the edges and Bow Clamps across the face.

I guess the bottom line for me, they are not a "be all end all" clamping tools, but just another (expensive) tool in the clamping arsenal. I still think they are too expensive for something made from wood (Besseys are too expensive also), and if I were regularly gluing a lot of panels, I would make a panel clamping rack.

DavidF · 02-14-2007, 10:21 AM

Originally Posted by Alan in Little Washington

I got to thinking about my previous question about the Bow Clamp's ability to apply even pressure across the length of a glue up and testing with strain gauges- would be nice to know (since I am a skeptic about manufacturer's claims), but I doubt anyone puts even pressure across a glue up with clamps of any sort- you just tighten until it feels right.

What is lacking with the Bow Clamp is the ability to put more or less pressure. If you need to put more pressure in one area (first you didn't do a good job jointing or had some post jointing warp- wouldn't be the first time) you can add a clamp on top of the Bow Clamp. Of course then you are changing the dynamics of it- so why do you need it at all. Second, I often release pressure on one or two clamps in a long edge glue up to make it easier to realign the faces. As DavidF found out you can't do that very easily with Bow clamps. Also, it would be hard to run cauls across the face of a glueup unless they are shorter than the width of ther glue up, since the Bow Clamps would be in the way. It might be better to use regular clamps on the edges and Bow Clamps across the face.

I guess the bottom line for me, they are not a "be all end all" clamping tools, but just another (expensive) tool in the clamping arsenal. I still think they are too expensive for something made from wood (Besseys are too expensive also), and if I were regularly gluing a lot of panels, I would make a panel clamping rack.

I tend to agree Alan, I would have had to apply a huge amount of force at the ends of the bow clamps to match that which was being applied in the middle. When I have made curved cauls in the past, I have had a tenth of the bow on these clamps. If you were to clamp a flat caul and measure the gap, if any in the centre then multiplied by 10 to actually apply pressure I am sure you would not be talking more than 0.1" of bow needed.

I did indeed have to use face cauls that were shorter than the panel width, and then long cauls on the top to apply the pressure. Certainly only juggling two clamps was nice, but as you say, they are not a "magic bullet" to the panel clamp game. Another member has offered me the use of the WC clamp system which I look forward to trying on the drawer sides and fronts. I will let you know how it goes.

Craig Feuerzeig · 02-28-2007, 10:34 PM

Thanks for two great reviews guys. Glad to see my Bowclamps put through their paces. This product will either stand on its own 2 feet... or not. And let the chips fall where they may.

But a few thoughts.

With the benefit of CNC, I can change or adjust the pressure rather simply. And David, I think you might be right about too much pressure on the 2 footers...You see, I never intended on the 2 footers being used in pairs, in a panel glue up, for the reason you stated... it only takes 3 or 4 clamps normally across that length. But this is exactly the kind of feedback I'm looking for.

I certainly know the "explosion" you speak of

. But it does take a little practice getting used to a new method. And a dry run or 2 always helps. I like to get started by applying just enough pressure in the middle to allow for adjustment and alignment. With a little practice you'll find that a half a turn one way or the other will let you "dial in" the right amount. Then just clamp until the ends are tight.

Nothing can be right for every situation, but I'm trying to work with averages for most common everyday clamping dilemmas. Also I do custom orders, and am toying with the idea of introducing light duty and heavy duty versions. Again looking for your feedback.

Also there is no "be all end all". But the Bowclamp is not just for panel glue ups. It will also apply solid wood edgebanding, attach face frames, counter-top edges, act as a deep jaw clamp going places other clamps won't, work as a veneer press, a hold-down... and as DaveO and Jeff are finding out, new uses come up everyday.

And wait until I show you the no clamps at all trick.