Primitive Archer
Main Discussion Area => Bows => Topic started by: Tommy D on May 23, 2021, 06:13:38 pm
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A sort of hypothetical question - what would happen if you cut the back off a self bow and glued it back with some back set/ Perry reflex?
Would you see some substantial improvement in performance (all else being equal)?
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Probably not. Just heat the reflex into the bow blank.
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The effort/performance gain ratio likely isn’t any different than perry reflexing two different pieces of wood. The advantage might be having a nice clean backing if using a stave but straight grain backings offer just as much protection.
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It was more me imagining a very “primitive looking” bow with backed bow performance
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The cutting kerf in the whole limb will reduce the draw weight substantially. Not sure you can recover it through glued-in pre-stressed reflex. If you have long stiff tips, it might an interesting idea to make a kerf cut there and glue-in the recurve, possibly turning it into a working recurve.
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You'd see the same benefits because it's the same thing.
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The cutting kerf in the whole limb will reduce the draw weight substantially. Not sure you can recover it through glued-in pre-stressed reflex. If you have long stiff tips, it might an interesting idea to make a kerf cut there and glue-in the recurve, possibly turning it into a working recurve.
You wouldn't do it to a tillered bow :)
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I guess people might take the process a bit too literally.
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You'd see the same benefits because it's the same thing.
+1. This assumes the wood is tension strong, but that is the case for the vast majority of our bow woods.
Mark
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Seems like a question from the "what if department". Just my opinion, but so much work involved, and you would achieve very little. Better to simply take a board and cut 2 lams from it. Now fit them back together and add your Perry reflex, and build a bow. Much less work involved. You wont have a Self bow in either scenario, but you will have a chance to see what that kind of reflex adds, and some of the complexities involved.
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I have a 4 inch PVC pipe set up made for just this.. rough out bow.. put whole stave in pipe.. have jig ready... steam.. clamp let cool...done.. gut
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Better to simply take a board and cut 2 lams from it. Now fit them back together and add your Perry reflex, and build a bow.
This is my understanding of what OP is talking about. Not taking a finished bow and then cutting the back off, but really making a Perry reflexed bow out of one piece of wood to start with instead of mixing different woods. Perhaps I misunderstood his intentions.
I have a 4 inch PVC pipe set up made for just this.. rough out bow.. put whole stave in pipe.. have jig ready... steam.. clamp let cool...done.. gut
That is not Perry reflex.
Mark
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I understand perry reflex is gluing up a deflex reflex bow .. with a laminate backing.. I was giving an answer to how to get the shape of perry reflex without gluing a back on.. gut
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Better to simply take a board and cut 2 lams from it. Now fit them back together and add your Perry reflex, and build a bow.
This is my understanding of what OP is talking about. Not taking a finished bow and then cutting the back off, but really making a Perry reflexed bow out of one piece of wood to start with instead of mixing different woods. Perhaps I misunderstood his intentions.
Yes - there would be no point doing it to an already tillered self-bow; but a roughed out stave was what I was thinking.
I understand perry reflex is gluing up a deflex reflex bow .. with a laminate backing.. I was giving an answer to how to get the shape of perry reflex without gluing a back on.. gut
My understanding - and I stand to be corrected - is that gluing in so called “Perry reflex” adds something more than you would simply get by creating that profile through steaming?
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I understand perry reflex is gluing up a deflex reflex bow .. with a laminate backing.. I was giving an answer to how to get the shape of perry reflex without gluing a back on.. gut
Perry reflexing does more than just provide the final side profile, it lowers stresses in the belly wood and usually increases performance. Bending reflex in doesn't provide these benefits.
My understanding - and I stand to be corrected - is that gluing in so called “Perry reflex” adds something more than you would simply get by creating that profile through steaming?
Yes, correct.
Mark
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To your point on using a roughed out stave...lam bows are not my thing, but I have piddled with them. Enough to know that a roughed out stave won’t work. You have to have the bow near finished thickness upon glue up. If not, you lose ground once you begin scraping the belly.
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Really? Most would say you gain ground if you glue up overly thick bellies.
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Hey Pat. Yeah, but with that thick belly that's bent and and glued into reflex, once you start taking tensioned wood off the belly, it seems to me you change things. or so I would argue. With enough belly removal, at some point you have lost a good bit of what you started with. You have done more of these than I have, so tell me your thoughts on it.
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Tommy, we have a very skilled bowyer here around cutting staves into laminates an reglueing into perry reflexed staves. His results are fantastic. I'm posting a pic from his site... He even sells them sliced staves for real swiss prices ;D. You'll find more examples on his site.
http://www.tiralarc.ch/index.php (http://www.tiralarc.ch/index.php)
I have done the kerfing thing too...if done right it should work fine. My very first post on this site was about it. It was one of these young dumb and wild Ideas ;D Back then I was not experienced enough to get good results and used inferior wood too. Maybe one day I'll try again.
cheers
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If you back a bow and glue it into perry reflex with too much belly wood, as you remove wood during tillering it can continue to take on more reflex. The more you scrape to get the limbs to come around, the more reflex it accumulates... sometimes a lot of reflex. Sounds like a good thing, but it can be difficult to navigate such a bow because it can come around all of a sudden and take set or come in under weight before ya know it. Imo, it's best to glue the pieces up in the shape you want, as close to final thickness as is feasible. Sure, leave a little extra for tillering and weight reduction... but just a little.
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I glued an ipe boo recently.. belly was too thick IMO... after floor tillering it has gained a good bit of reflex.. still haven't got it to tree. just got tip overlays and grooves cut... been too busy with stuff around the house.. but it has definitely gained at least an inch or more.. it's around 5" or 6" of reflex now..I have it next to 2 others I have glued up .. an osage boo and a cedar boo backed.. it's reflex sticks way higher.. I never knew that perry reflex actually took stress off belly.. seems it would create it at the point of deflex turning to reflex.... I'll take that as lesson learned but find it hard to believe.. I'd post a pic but I can never get one posted always file too big... gut
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Marc with just one glue joint I don’t think you get much benefit over the steaming. Putting boo on the back might help Osage. Maybe
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I never knew that perry reflex actually took stress off belly.. seems it would create it at the point of deflex turning to reflex.... I'll take that as lesson learned but find it hard to believe..
perhaps it allows a thinner limb to make weight, the thinner limb being stressed less for the same bend? At first glance, it would also seem to work the back harder, as it is bending further to full draw...... but if the finished limb is actually thinner than a self bow of the same weight, maybe not?
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I never knew that perry reflex actually took stress off belly.. seems it would create it at the point of deflex turning to reflex....
It doesn't have to be a deflex/reflex side profile. You can do Perry reflex for pretty much any side profile you want.
For those that said you want to be near finished thickness when you do the glue up I would agree. It is just easier to only have to final tiller it to fine tune the bend. I can believe one that needs a lot of belly wood removed could get pretty unruly as the reflex keeps changing.
Marc with just one glue joint I don’t think you get much benefit over the steaming. Putting boo on the back might help Osage. Maybe
You are correct that you don't get as much as if you use 3 (or more) layers and glue in deflex before the final glue up, but you can get enough to make it worth while. I would have to look back at my numbers but I think it was something like 10-15% lower belly stresses.
At first glance, it would also seem to work the back harder, as it is bending further to full draw......
Indeed it does. That is really the trade off - lower belly stresses for higher back stresses. Since most bow woods are compression weak it is usually a good trade to make but you never get something for nothing (as bownarra notes).
Mark