Stringstretcher,
I do NOT have enough experience with the rubber strap types of forms to comment as to their capabilities or limitations. They very well may be capable of producing a glue up just as solid as a high pressure form. With as much rubber as Marty used, they may have as much pressure in them as a typical air hose/high pressure form. I noticed in Marty's picture you don't see ANY of the belly on that bow. If you look at mine in the hot box, I didn't completely cover the belly with rubber. My fear of limitations on this type of form is NOT from fact, but is a result of MY lack of experience with using one piece forms...but I certainly find their concept very user friendly. Someone such as Apex Predator (Marty) would be much more qualified to address your questions as to what this type of form is capable of. Next time I will use much more rubber. Does it matter that I made that error on that first bow? No, not really. It was educational and I am confident that bow will be fine. It turned out nice, just not perfect...but it isn't something I am selling and it won't have to endure much tension and/or compression since it is only 15#@18" draw. I came out good in the critical areas (the fadeouts and overall limbs). I also noticed a glue line on the bow that is about 0.010" on the curve the glass had to follow on the BELLY side of the riser right next to the grip, but again that would have resulted from not having enough pressure on the bow during glue up. I am being very critical though, as I don't want to see a glue line at all. I have actually seen thicker glue lines on some adult bows that receive regular use to be honest. Given the excellent fit on the backside of the riser and bow, I am confident that the form is good and if I had used as many straps as Marty is using in that picture above, everything would have been better in my son's bow...so again, on the next one I make I will fix that. I also see Marty has a C-clamp on the riser. I ran my belly glass over the belly of the riser, so I might skip the C-clamp aid for now, but I will AT LEAST use much more rubber. I will post some close up photos when I am done to illustrate what I learned...and if you like I will update this thread when I do a "2nd attempt" to see if I solved the issues I observed in my "1st attempt."
As far as "one piece" forms go...I know some EXCELLENT bowyers use them. I believe Chris Cox (Habu bows) and Howard Hill Archery use them (at least they use to) but both used C-clamps instead of rubber. My reason for using rubber instead of C-clamps was because I MYSELF didn't know how hard to twist the clamp in order to obtain a desired pressure on the bow. I didn't want to have INCONSISTENT pressure that resulted in "pressure points" as I feared that might crack the belly glass. Chris Cox, IMO, is probably one of the best bowyers out there but IF MEMORY SERVES ME CORRECTLY he has some way of evenly distributing C-clamp pressures. I think he had 2" blocks on top of 1/4" thick rubber pressure strip, but I am not certain about that...as it has been many years since he and I spoke on that matter. Please do NOT take MY INCOMPETENCE with this type of system to mean/represent the inabilities of this type of form in general. It is just I MYSELF am not versed in them as I am with the high pressure air hose/2 piece form.
Marty,
I have certainly not made as many bows as you have. I only started making bows last October. My reason for becoming a bowyer was motivated by my experience as an archer...as I have come to prefer certain characteristics in a bow...and I wanted it done my way. Not to say my way is the only way or the best way...but it is the best I know of for ME. I wanted a bow that met my criteria, so I asked Gary Sentman to teach me how to make a bow. Gary, my mentor, had about 3 decades as a professional bowyer and he has certainly made a few thousand bows...and MANY bows well over 100#. Remember, he was known for setting the world record 176# bow back in 1975, so many people that wanted heavy bows would call him up. He informed me he generally glued up at 100-120# psi and told me to do the same. He taught me how to reinforce my form and air hose system to sustain such pressures. That said, I actually stop at 100 psi on my form. With a properly assembled air hose and a highly reinforced form that has CONSIDERABLE brackets (not the 1" ones you can get in a kit that by the time a 1/2" hole is drilled into them you only have a 1/4" on each side of the bolt holding thousands of pounds). If these extra steps are made to "beef up" things, then the process goes really well, except for having to move that 100# beast around. I have never had a single air bubble in any of our bows. That is why I called the heavy form the "back breaker." The only problems I see with using this much pressure is one BETTER have a super clean slick surface. If you have a grain of sand on the form, there is a good chance it may leave a mark/dent on the bow and we obviously don't want that. I clean my form and wax it with a paste every time I use it for that reason. Plus, that helps to remove the bow after it is cured.
As far as a "starved" glue joints are concerned...starved to me means empty...an area void of glue...and I would speculate that is a result of either not having enough glue on the bow or actually not having enough pressure on the bow. One of those two. I don't think pressure will squeeze out all the glue. In contrast, I think it can drive epoxy into tiny pores that otherwise might not be penetrated by the epoxy. I think pressure eliminates "pockets" and voids. In other words, I actually think low pressure was the reason I got the few gnat bubbles I got in that youth bow. I think with more pressure, I would have driven the epoxy into all the tiniest pores more efficiently.
Topic: Some of the coolest things seem so simple (Read 460 times)
