a clamp to prevent bowing cants ?

[kelLOGg]

I want to run this idea up the FF for a clamp to prevent bowing cants before I make it. The idea is to slam the cant into a stationary "beak" and then tamp the moveable clamp into the opposite edge and tighten it to pull the cant down – and hopefully keep it down during sawing. See sketch. Think it'll work?

Bob
https://forestryforum.com/gallery/albums/userpics/13036/beak_op.JPG

[Jeff]

I believe that you would be putting more time and effort into something then what it would be worth in return.  On the commercial mill I used to run I had all the holding power in the world. Hydraulic brute force, and wood that wanted to move would still move. It will tear itself apart if there is enough stress. You can actually end up with more screwed up would trying to stop it then you would if you just worked with the log.

[bandmiller2]

Bob, I fear your trying to shovel sand agenst the tide.Even if you could hold the cant straight the boards that come off will be bowed.Its fustrating to make a straight cut flip the cant and see a big bow.Cut on opposite sides to reduce the bow {stress},some logs you just can't help.What I have done with oak logs is cut and let them age a few months seems to let them work out their problems.Frank C.

[logwalker]

I think just the tooth on one side would help. Use a large sliding heavy-duty clamp to pull the cant down and then tighten the flap clamp. But then you would always be fighting the tooth and leaving marks on the faces. I do take a small bow out by tightening the clamp and then smacking down with a single bit hand axe I keep handy. Works well on smaller timbers. Joe

[Meadows Miller]

Gday Bob

I find its not worth fighting timber with Alot Tension in it .
I genraly start by taking a light roundback  and a board of all sides and leaving a rough square with minimal or no Sapwood left in the cant  this will leave You with two strait sides at rite angles to eachover Your wing boards should be within sawing tolerances .I also cut the cant between 1/2 to 2 inches oversize  plus saw kerf for any cuts I intend on making in the cant this allows for Face cuts on the two Bowed sides of the cant then flitch the widths You want in the cant turn the flitchs up and Board off .this works on most of the H/W logs I have milled so far aboud 10million bf. If You have any  ??? just ask as I can post this and a few other stress relef sawing patterns for you in picture form.

Good luck Chris

[Fla._Deadheader]

  That's the reason "Skim" cuts were invented. Sometimes you just HAVE to take a thin board, to get the cant flat enough for a decent board. Some logs just won't allow you to get NICE boards  : :

  It's very difficult to make Chicken Soup out of Chicken Poo.  : : ;D ;D

[backwoods sawyer]

I am going to step out on a limb here and AGREE WITH YOU that a simple clamp would save a lot of lumber that is lost due to the limitations of the equipment. In the large production mills they hold the wood where they want it with rollers ect. After it is cut, the tension is relieved in many cases, sure, there is wood that it will not help, but if you can push it down by hand and all you need is a way of holding it, your clamp would work just fine and you would not have wasted your time in designing and building it.

Further more I have been saying for a long time that Woodmizer mills need a double clamping system to hold the wood in place as a single clamp contributes to the bow problem by putting all the force in the center of the wood. Look at any production mill and you will see that they have figured out long ago that you have to hold the wood in as many places as possible. In fact, the small log mills are now so sophisticated that after the log is scanned the saws move to follow the curve of the log, and the wood that comes out the other end is straight. 

The small manual mills use more then one clamp and you can walk on the wood so that your weight takes the bow out of it.

Don't except it the limitations of your mill, improve upon them, after all it is the American way.

[Tom]

I've found one clamp to be sufficient exept for ultra long stuff, and even then, by the time you get to the last couple of boards, the weight will hold it down.

The best thing is to learn to cut to the tension in the log by turning the cant. It's a lot more accurate, creates better boards and is generally faster.   Anything you do that stops the sawhead is counter productive, even if you have to do it. 

[backwoods sawyer]

Anything you do that stops the sawhead is counter productive, even if you have to do it. 

I agree with that portion of your statement.

But when you are cutting a lot of 16' X  ¾" boards, and a simple clamp would prevent you from having to waist a good board why not use it?

After all the whole idea behind the thin-saw, technology is higher recovery. (Higher recovery = higher profits)

In addition, every time you turn the block your saw head is not cutting wood.

[peterduncan]

Has anyone out there attempted to make a huge vacuum clamp?

[kelLOGg]

Thanks for all the input.
I realize attempting to clamp a big cant is futile but there have been many times that the final few cuts have benefited from holding down the board with a cinder block or forcing it down with a hand (usually mine...dangerous) so I think I will make a few clamps. It will slow down sawing to put them in place but I'm not into production and it will keep me and the customer happy to not see an ugly bow appear wasting the wood. I'll find out how effective it really is.