BowClamp Review

[ericbuggeln]

I have had the Bowclamp Master Set for about a week now and have become pretty familiar with them. In order to review them I have built a standard wall cabinet. I found them helpful in carcass assembly, FF to carcass assembly, and edge banding. I will go over all of these procedures in this review. There are other things that the Bowclamp can do, such as gluing up panels and laminations. In the next week i will be posting about using the MFT, shims and Bowclamps to clamp, without clamps. I will also post back on some more complicated glue ups.

The Bowclamp Master Set comes with two 2', two 3', and two 4' cauls and can be found at http://www.bowclamp.com/
You can also buy single cauls or pairs. The Bowclamp has a leather strap which makes it great for hanging from the wall and doesnt take up much space. The Master Set would suffice for all the procedures i will go over, although I can already tell that for some complicated FF to carcass assemblies more would be better. Specifically if your project had mid rails where more then two pieces of the same size caul would be needed.

The Bowclamps are made of solid maple and are CNCed to have the perfect curvature. The curvature allows perfect glue squeeze out and maximum force/pressure, so while you could make these on your own, you are not going to be able to achieve that degree of accuracy. There is a groove that will accept light or medium duty F style clamps and that could greatly help the ease of use, but since i didnt have any of those, I will use Jorgenson 3/4 Pony clamps for the entire review. Virtually any clamp can be used with the Bowclamps. The Ponys worked great. Bessey Parallel clamps were significantly fussier to deal with, but I fully blame the clamp and not the cauls. The beauty of the Bowclamps is that you can acheive your clamping goals with less clamps. Now that I have a 4x8 dedicated assembly table, I want to glue as many cabs as i can at once, but I only have so many clamps. In comes the Bowclamps. My favorite procedure they assist with is the FF to carcass assembly. Usually a task that takes every clamp in the shop. With four Bowclamps and eight clamps you can attach most any size FF. Instead of having clamps every six inches you just need one Bowclamp and two clamps and you can achieve the same results over a four foot span. For me the beauty is now i have extra clamps freed up to work on other cabs, which equals less wasted time and more money in your pocket.

For the carcasses, I dominoed everything as normal. The first pic shows all of my parts, clamps, Bowclamps, and glue all readily available. I start with the base panel and work up around the back. The top slides in and then i snugged up the bottom, snugged up the top, checked everything and then cranked it home. The carcass was very square right away. The glue squeeze out is remarkably uniform.

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The FF to carcass assembly was also dominoed as normal. I laid the cab on its back, glued, dropped dominoes, attached FF and then picked the unit up and put it into place. I used two 2' Bowclamps along the top and bottom and used two 3' Bowclamps on each side. In total you would need eight clamps for that. With the Ponys you just clamp over the top of the Bowclamp bc they obviously dont fit in the groove. Once again very uniform glue squeeze out. The top and bottom Bowclamps are easier to attach compared to the sides which can fall on you with a heavy pipe clamp. I found that you need to hold the screw part of the clamp and the Bowclamp in one hand and then use the other hand to snug the back. After that its smooth sailing.

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I always put a 3/4 nosing on my shelves and the Bowclamp is just the job for that.

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I had the pleasure of meeting the inventor of the Bowclamps last summer and watch him demo his product. Check out his videos on his website or You Tube to get a better understanding of what this product can do for you. Craig is a great guy and a real cabinetmakers, cabinetmaker. I think he is really on  to something here with the Bowclamps. There are endless possibilities on how this product could help any cabinetmaker. Once i saw a demo, it was self explanatory what to do with them. I found the Bowclamps had virtually no learning curve and I was able to incorporate them into a build immediately. They do exactly what they advertise, which can be rare these days. I received this Master Set in order to do this review, but will assuredly be buying more to further increase the capabilities of what i can do with them. I am really excited about the prospects of assembling multiple cabinets at once, now that i have more clamps freed up.

In essence, Craig was able to invent a product that has equal parts pressure and equal parts force, which is a lot harder then it looks. Let me know if you guys have any questions that I could help you with or just want to discuss clamping stuff, Eric

 

[ericbuggeln]

I was using some jigs to get the Jorgenson Pony Clamps up off the table in this review. They were designed by my friend roman of Roman Enterprises, no connection to Bowclamps, but work very well in conjunction with them. This is the second prototype. The next model will be stackable, so you can have a multi tiered clamping press to do doors with. They will work with the spacing of MFTs and UWBs. If anyone is interested in them you can PM me, Eric

 

[ericbuggeln]

CNC in action, Eric

 

[Theshipstore]

I have been using the Bow Clamps now for about 9 months and I will say Craig has done one heck of a job in the design and engineering of this product.  [thumbs up]
I use them mostly for the gluing of my Face Frames to the Cabinet Carcass in my Cabinet Making ventures.

I was fortunate enough to meet Craig on two separate occasions each time we had a long talk on the useage and value of these Bow Clamps.

I would highly recommend these to anyone who has glue up situations as they work very effectively with a minimum amount of clamps, that feature alone saves time and makes glue up that much easier.

Sal

 

[ericbuggeln]

Sal, thanks for the response, it was dead in here. The FF to carcass is where the Bowclamp really shines. No more using fasteners(brads, headed pins) to secure those hard to reach areas that you cant get a traditional clamp. I have two vanities that I'm bidding on right now that will have such spots and I hope to get some pics of more complicated glue ups posted. Eric

 

[mouppe]

I use them predominantly for gluing up panels. Because you only need two clamps per panel, you can do three or four times as many panels at a time. A real time-saver.

 

[ericbuggeln]

Richard, any pics? I don't really have any appropriate stock laying around to show that, but it is a great use, Eric

 

[semenza]

Looks like a good set up. Everything held in place, no fumbling around with all the seperate pars. How soon for the stacking ones?

Seth

 

[ericbuggeln]

Seth, obviously the Bowclamp doesnt need my jig and could just be rested on the bench and the clamps could come over at a 45 degree angle. The jig gets you up off the table and gives you much more stability. In conjunction with the Bowclamps it acts as a press. The bottom and top Ponies are either resting in the jig/bench or laying on top of the cab, so you just slide the Bowclamp in and crank down. The vertical ones, you need to hold the screw part of the clamp and the Bowclamp in one hand and close the clamp with the other. Sounds a lot harder then it is and on my second try was doing it just fine. As with most clamping procedures i snugged all clamps, checked everything and then crank down.

As far as the jigs, this was the second prototype and a stack able version is around the corner. I will be posting more on them in the future on this thread, mostly bc the two go so well together, Eric

 

[mouppe]

Richard, any pics? I don't really have any appropriate stock laying around to show that, but it is a great use, Eric

I don't have any photos- sorry!

I used to use 5 x30mm dominoes for the vertical alignment of the panels but have switched to the 4 x 20mm dominoes because it's quicker to mortise 20mm than 30mm, and you don't really require the extra length and strength of the 5mm dominoes. Then a Bowclamp either side, a parallel clamp at each end, and it's on to the next panel. I had about thirty shelves to do, so you can see how important it was to do four glue-ups at once.

 

[ericbuggeln]

I'm gonna do some veneer pressing on the MFT tomorrow with the screw clamps and will have pics up asap, Eric

 

[John Stevens]

I use them predominantly for gluing up panels. Because you only need two clamps per panel, you can do three or four times as many panels at a time. A real time-saver.

Yeah, interesting idea, and one where I guess experience has to be your guide.  My resistance to this idea is because Franklin (Titebond) recommends 200 PSI along the whole length of the glue joint.  You can't get that with a bowclamp and two clamps.  On the other hand, I've glued together mitered boxes using only tape to provide the pressure for the glue joint, and they turned out strong enough to park a car on 'em.  So your idea appeals to me, but Franklin isn't in the business of selling clamps, so I don't see an incentive for Franklin to overstate its pressure recommendation.

I'd love to hear your response, Richard (and anyone else), because your method looks like it saves quite a bit of time and effort.

Regards,

John

 

[mouppe]

I use them predominantly for gluing up panels. Because you only need two clamps per panel, you can do three or four times as many panels at a time. A real time-saver.

Yeah, interesting idea, and one where I guess experience has to be your guide.  My resistance to this idea is because Franklin (Titebond) recommends 200 PSI along the whole length of the glue joint.  You can't get that with a bowclamp and two clamps.  On the other hand, I've glued together mitered boxes using only tape to provide the pressure for the glue joint, and they turned out strong enough to park a car on 'em.  So your idea appeals to me, but Franklin isn't in the business of selling clamps, so I don't see an incentive for Franklin to overstate its pressure recommendation.

I'd love to hear your response, Richard (and anyone else), because your method looks like it saves quite a bit of time and effort.

Regards,

John

John,

Good point.

I've never had a failed glue joint using this method. On the other hand, I take a lot of care to ensure my edges are square and true, so that the glue will be at its most effective. It's also hard to imagine a scenario whereby a panel will be subject to such strong tension that the glue joint will fail, especially if the joinery is sound. If anything, the wood would fail before the joint. In the bookcase below, I match-planed two timbers for each panel using a TS55 and two connected 1400 guide rails.

I had to glue up 8' planks of 3/4" oak to make side panels 12" wide. I used a pair of 4' clamps and a pair of 3' clamps and a couple of parallel clamps to fill the missing gap. I had 4 of these panels to make, plus a 12' top and bottom. I obtained good squeeze out all along the joints, which indicates to me sufficient clamping pressure.

I spent a lot of time making sure my joinery is accurate and structurally sound, even for as simple a job as this bookcase. It reduces the need to rely on glue to hold the whole thing together. I can't imagine how many clamps I would have needed for this job if I hadn't had the bowclamps.

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[ericbuggeln]

John, for arguments sake, and I have no idea the answer, but what PSI value do you believe the Bowclamps can achieve on a four foot panel? Or how many Jorgenson Pony clamps would you need on a four foot panel to achieve 200 psi along the entire length?

I will try to explain what Craig told me about the Bowclamps. When you lay the Bowclamp against a surface to be clamped, the tip of the bow presses down in the middle and the two ends are not touching. Once you snug the two clamps the tip is already pushing glue from the middle out to the two ends. If done properly the glue moves to the end and subsequently out the end as you make your final turns. No pockets. When doing a panel, you would just be doing both sides. The glue squeeze out on my small project made me very confident on the quality of the joint, Eric

 

[Rick Christopherson]

John, for arguments sake, and I have no idea the answer, but what PSI value do you believe the Bowclamps can achieve on a four foot panel? Or how many Jorgenson Pony clamps would you need on a four foot panel to achieve 200 psi along the entire length?

First off, I believe that the need for 200 psi is a little too high. I feel that 100 to 150 psi (or even less) is sufficient. It is not about joint strength that was mentioned earlier, but about making a truly invisible glue joint.

As for your question, for a 4-foot joint of 3/4" material (36 square inches of joint surface area); to achieve 150 psi it will require 5400 pounds of force. This will require a minimum of 4 to 5 fully-cranked pipe clamps to achieve. A 4-foot BowClamp will max-out at only a couple hundred pounds of force unless additional clamps are used. That gives you only about 5 psi for the joint, which is even lower than a vacuum bag at 14 psi.

I will try to explain what Craig told me about the Bowclamps.

I think the BowClamp is a great product, but there is misleading information about what they can and cannot do. Craig has been asked by several people to provide the specifications on his clamps regarding how much force it takes to "straighten" the bow of the various clamps. That's because the force that it takes to flatten/straighten the caul, is the maximum effective force the caul can apply to the workpiece. For a short caul, this number will be quite respectable. However, for a 4-foot caul, this number will be very small. This is why a 4-foot caul is going to give you only about 5 psi on the joint, as opposed to the desired 100 to 150 psi that I recommend, and the 200 psi that the glue manufacturer recommends.

Craig markets his cauls as though they are a force-multiplier, instead of a product that spreads the force. The most obvious example is a picture on the internet showing a large veneer layup using 4 small clamps and a bunch of cauls. What not revealed is that this veneer layup resulted in less than 1/2 psi (0.5 psi) of pressure on the joint. You can get more pressure than that just by pressing down with your thumb.

I created this video several years ago specifically due to his claims at the WoodNet forum at the time. It explains the difference between force and pressure.

 

[Theshipstore]

Rich    Thank You for your input, this makes me look at gluing most anything now in a totally different light for sure, you explanation of force vs pressure has and will change my clamping methods. It funny but I am one who owns probally 150 different clamps and have over years clamped the daylights out of things.

I have used the Bow Clamps with great success and I do like how they work on my face frame to carcase glue up's but this does throw things  in a different light, as far as adding additional clamps to the glue up.

I guess the old school methods for which I was taught are still the new school idea.

Again
Thanks

Sal

 

[zapdafish]

I use the bowclamp for solid panel glueups and have no problems with unsightly glue lines. If a woodworker thinks cauls are going to fix sloppy edges and magically give them invisible glue lines then yeah, they are misguided.

 

[Michael Kellough]

Bowclamp is a well made product thats greatly simplifies glue-up. You won't achieve anywhere near the 200psi that Franklin (inexplicably) recommends but you don't need that unless your joints are junk.

The pressure an individual Bowclamp can apply depends on the individual piece of wood it was milled from (stiffness and grain orientation). The stock product is made from hard maple so the variation in stiffness from one Bowclamp of the same length to another is slight. In a custom order you can specify a different species to get a different stiffness. You could also request that the groove be omitted to increase stiffness.

In practice you can use two short Bowclamps instead of one long Bowclamp if you want to increase pressure but that kinda defeats the point of simplifying the process.

The standard product works just fine with ordinary yellow glue to make fine joints on well fitted work. You do need to get the glue on fast and even (Craig uses a mini paint roller). If you go slow and let the thin edges of the glue start to dry you might not have enough pressure to crush those spots of stiff glue.

If you want fine glue lines don't use fast setting glue or high solids glue. To get near invisible joints use thinner glue like stuff advertised for longer open time. Many of the best old school craftsmen still use Elmer's white glue (they started before Franklin's yellow glue came along). Consider this, fine craftsmen use white glue, factories use high solids glue. If your joints are fine you don't need thick glue, or much pressure.

I don't think it's right for Rick to continue to criticize Craig for what he said or misunderstood years ago.
Maybe it's that Rick misunderstood what Craig said meant because Craig used the wrong terms.
However anyone describes the physics the mechanism is dead simple.

I've never heard Craig describe Bowclamps as a force multiplier. He does describe them accurately enough as a force  distribution system. (Okay, technically it's a pressure distribution system but sheesh.) Apply force to the ends of the Bowclamp and you get some fraction of that end pressure evenly distributed between those ends, exactly what you want when applying edging etc.

 

[semenza]

Please keep this thread on topic and related to the review and use of the product.  Further comments that are of an attack nature, or seen as trolling, or antagonistic will result in the removal of the post , due to  not complying with FOG posting guidelines.

SRSemenza FOG Moderator

 

[Svar]

The force exerted by the bow clamps is actually easy to calculate. Let’s say a bow clamp is 120 cm long (4 ft model), cross section is 5x5 cm, the “bow” is 10 mm at rest, and it’s made of hard maple (E=1260N/mm^2). When the caul is straightened the maximum force exerted is about 1800N (404 lb-force). If you are gluing 120x2 cm surface it is 7.5KPa (10 psi). I made some pretty conservative assumptions, so l’ll say its below 10 psi for this example. Not much, but perfectly fine for edging. You can continue to crank down the clamps and get more pressure on the ends, but it will not affect the middle any more.

P.S. You could make much more rigid cauls from aluminum square tube with wooden tapered strip attached to it.