Questions on bow forms

[Bighornangler]

When making a wood deflex/reflex bow with a bamboo backing, would it be better to use a solid wood form with the bow profile cut in and holes drilled for clamps or a typical 2x4 form with a center post, midlimb post, and tip post  since the bamboo backing is radiused and not flat? My concern is getting good glue lines not ease of making the forms. Also, since you are using a radiused boo backing, would it make any difference if you used say a strip of scrap bamboo or a metal strip as a pressure strip?

[Roy from Pa]

My form is adjustable so I can make different r/d designs. If you make a solid form, all your bows are going to be the same. I use 2 inch scrap pieces of boo for padding the back.

 

 

 

[Bighornangler]

Roy. Thanks for your input. I understand what you are saying about the flexability of your form, but that is not my issue. I have a form just like yours as well as a solid form. I am not happy with my glue lines with either form, that was why I was asking about the boo being radiused & not flat. A friend of mine who has years of experience building glass bows, but has never built a all wood bow, expressed his concern that the boo being slightly oval or radiused, might be a problem with getting good glue lines.

[Roy from Pa]

Well the 2 inch sections of boo I use for padding will assure uniform pressure on the boo backing. You need to clamp every 2 inches. I snug the clamps down but do not over tighten them. It doesn't take much pressure to squeeze the glue out of two flat surfaces that are only 1 1/4 wide down to 1/2 wide. Nice glue lines also require two flat surfaces that are square on the edges. Also I have my boo cut to the exact shape/profile of my bow before glue up. My belly slat is a good 1/4 inch wider than the boo before glue up. After glue up is dry and before I cut the bow out, I first glue on the riser section. After that glue up is dry I then proceed to cut the entire bow out, staying about 1/32nd" away from the edge of the boo, then getting down to the edge of the boo with hand tools.

[kennym]

Hand tools and that 7 hp sander! LOL

Roy makes a great point on profiling before  thinning the boo.

That was the demise of my boo backed sage.

The boo was waaay thick when glued full width and then profiled to narrower bow dimensions..

You are probably familiar with all that, but I relayed the info for someone first trying.

I think Roy likes to see a feller break one, cause he didn't tell me til I broke it!!  :D

[Bighornangler]

Roy. I pretty much do mine the same way as you. I never cut my boo pressure strips 2 inches, but instead used a full length piece of scrap boo. I don't see that would make any difference, so I'm thinking my surfaces are not as flat as I think they are OR the amount of pressure I'm using with the c clamps is the problem. I tighten the clamps about as tight as I can by hand. I recently was able to borrow a torqe wrench that I could put over the c clamp "t" handle and discovered that I was getting about 3 to five lbs. of torque pressure. Too much or not enough??

[Roy from Pa]

Could be your surfaces are not flat is my guess, OR... Your full length boo pressure strip, did you grind/round out the cross section on the belly side where the nodes are? You understand what I am talking about there? At every node on the boo, on the belly side it is not concaved like the rest of the boo is, it is flat across the belly side at each node. If you don't grind that section out, then at every node you are applying more pressure on the glue joint than on the rest of the lateral length on the boo pressure strip. I think you are making the clamps way too tight! All they need is snugged down till the clamp gets tight, then maybe another 1/4 turn. We are only trying to make the two flat surfaces snug together here, not force them to squeeze all the glue out between them. If I were you, I would cut scrap boo into 2 inch long pieces, without the flat section across the belly side on any of them, or grind it out. Then space them equally along the bow when you glue it up, leaving 1/4 inch spacing between each section of scrap pieces. And ONLY snug down the clamps, don't try to make them as tight as you can. Look at these two pictures below again and you can see how I space them and the clamp is right in the middle of each 2 inch section.
 
Your about a 6 hour drive from me. Ya wanna come out here someday and we can do this together?

   


   

[Bighornangler]

Thanks Roy and Kenny for your help. Roy I would like to take you up on your offer to come out to your place someday. I will be in touch.