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67" Red Oak Lam Bow, 50lb @ 28"
bjrogg:
One good one a year will work.
Bjrogg
willie:
--- Quote from: mmattockx on November 27, 2021, 08:54:57 pm ---In replying to the questions, I realized I didn't put any pics of the grip area up...
Mark
--- End quote ---
after seeing your handle pic in this post I was curious if the bottom lam is the same thickness from tip to tip? ie the entire fade is contained in the lighter colored handle piece? some bowyers dont have very much success with the glued on handle arrangement. Was the short lam on the back of handle purposely designed to help spread the stress in the fade area?
nice glue lines!
tb3?
mmattockx:
--- Quote from: willie on December 26, 2023, 07:46:34 pm ---after seeing your handle pic in this post I was curious if the bottom lam is the same thickness from tip to tip? ie the entire fade is contained in the lighter colored handle piece? some bowyers dont have very much success with the glued on handle arrangement. Was the short lam on the back of handle purposely designed to help spread the stress in the fade area?
nice glue lines!
tb3?
--- End quote ---
You're making me go way back in the memory bank here...
1) The bow is 3 lams full length and the ~0.080" thick power lam under the handle area. I don't recall the main lam thicknesses, but the core is thicker than the back and belly lams. I think the back and belly lams were the same thickness. They are all constant thickness, though, with no taper. All the tillering was done by designing the pyramid profile to work with constant thickness limbs. The pyramid shape isn't a true straight sided triangle, it has a bit of an arc to it as that is what you actually need for correct tiller with constant limb thickness.
2) I glued the power lam in towards the back side of the bow because it simplified my layups during the laminating. Structurally it doesn't matter where the power lam is in the stack, just that the overall stack thickness in that area increases as intended.
3) Yes, the lighter wood has all the fade in it and is a glued on piece. The colours vary because I used oak pieces from a number of boards.
4) Yes, TB3 for everything. I think it is a bit soft for laminating like this and is part of the reason the reflex pulled out during shooting in. I am going to try smooth on for the next one.
Since you have asked, I will add a bit more detail. I gave a very basic description of how I did the glue ups, but here are some pics.
Glue up #1 - Belly and core lams glued into deflex:
Glue up #2 - Belly/Core lam assembly pulled into reflex with the back glued on. The back of the bow is up in this pic:
This pic shows how far glue up #1 had to be reflexed for the second glue up:
The end result, something like 1/2" or so of reflex but with the belly pulled into tension like there is 6+" of Perry reflex:
The handle pieces. The thin one is the overlay on the back, the other on the belly side:
The handle pieces glued on and part way through shaping. I liked using the drill press with Forstner bits for hogging off the majority and will definitely use that again on big, chunky grips:
Mark
superdav95:
Very interesting set up jig for your glue ups. Looks adjustable and sturdy. I like it!
willie:
Mark,
thanks for the detail pics on the fade pieces. As I thought, the power lam helps distribute the load better over the fade area.
Curious about the perry part of the experiment. Did you collect force draw data when the bow was fresh off the form?
My guess is that if there was a measureable benefit to the pre stressing of the lams before glue-up, then there might be a higher string tension at brace and early draw weight, (when compared to a non perry reflexed of the same design).
since you dont mention a control bow for comparision, would you comment if the bow has lost any draw weight, or specifically, any early draw weight, in the few years of use?
My thought is that if the bow, fresh off the glueup, has internal stresses even when unstrung, then
perhaps over time the wood might creep back towards an unstressed condition similar to the way a thin board leaned up against the wall will take a permanent set or "belly" over time.
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