Primitive Archer
Main Discussion Area => Bows => Topic started by: Mafort on July 11, 2018, 02:59:01 pm
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so i have a question. a buddy has a strip of bamboo that hes flattened and planed to glue up to the back of a bow he was bulding but he decided to sinew back it instead. hes giving this strip to me. i was wondering if i have a hickory stave floor tillered to say 55 lbs of draw weight what is a ball park estimate of the draw weight increase i can expect with the backing???
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There's no way to tell.It'll be enough of an increase, you will have to re-tiller, and could really have a new target weight. Basically it's like starting over. Hope that helps.
Tattoo Dave
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There's no way to tell.It'll be enough of an increase, you will have to re-tiller, and could really have a new target weight. Basically it's like starting over. Hope that helps.
Tattoo Dave
that explains it perfectly. i appreciate the reply
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I would estimate 10 to 20 pounds, but it's just a guess.
Like Dave said, you will have to retiller for sure.
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You'll have to flatten the back of the hickory bow to accept the boo so no way to tell how much weight you'll loose doing that.
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Ben beat me to it I would guess 85 lb or so depends on length of the bow & other factors , I just measure my 68'' ,48 lb @ 31'' BBH bow and it's ruffly 1/2'' out of the fade , you might want to thin that bow a bit and glue in some reflex for a pepper bow ,I love the BBH combo fast and durable combo it's one of my favorite natural material bows !
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I posted at the same time as Pat but if I remember right my hickory core started out at a hair over 3/8'' Pats right you need to get the core back flat the closer you are to having every thing right at glue up the easer is to tiller and a nicer bow !
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sooo if i was aiming for a bow around 70-75 lbs or so at 28" what would i tiller my hickory wood core out to be??? i have a really good flat back on this one so im wanting to do it right. my buddy that i hunt with every year is wanting to hunt traditionally before he starts building them himself. i use a 75 lb ELB style yew wood bow that ive had for years. and he literally loves that bow so hopefully i can surprise him with this hickory and bamboo one. i also appreciate your guys help.
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would i be ok tillering the bow down to 40lbs and then backing with bamboo to get the 70-75lb draw? the length of the bow is 64 inches long right now.
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also do i sand down the nodes???? that sounds like it would weaken the backing.
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I have no idea for a 75 lb bow maybe Ben will chime back in but with these lam type bows there is a lot of guess work involved some times it also depends on design and reflex and pre taper to get close to the weight you want , if I where in your shoes I would flatten the back and glue in 2 in. of reflex and see where your at you can always remove more wood , I don't know if any body can give you a definitive answer on weight particularly sense your using a stave vs pre tapered lams ! If your at 55 lb at floor tiller you have plenty of wood to go so your in good shape !
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No don't sand down the nodes your right you will weaken the back !
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The most you'll want to do to the back of the bamboo is remove the rind, and some light sanding. Not sure if your buddy did that already.
Hopefully someone with more experience than me with heavier bows can comment on starting dimensions for you. If I was doing it, I would start with hickory .75" thick and see how much force it took to bend it a few inches and go from there. Never made one that heavy.
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When I did BBO's and BBH's I start out with a 3/8" thick core with 1/8" thick bamboo on a 64" long bow.At that time it's easily 65 pounds right off the form.Those were D/R bows 1 and 3/8" wide @ fades.Straight Line taper to 1/2" wide tips with a moderate reflex of a couple of inches induced past the back of the handle into the outer half of the limbs.
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I'd glue it up and remove wood to achieve the desired weight instead of trying to guess how far to tiller before hand.
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There's a lot of things that can affect dimensional requirements on laminated bows, but I usually require a little more thickness than what Ed has seen with his bows. I've made a couple 60#'ers and they need to have a total thickness of about .6". So .125" bamboo and .475" core. And this doesn't leave you much room to play around with the tiller. But those bows were a couple inches longer.
I agree with Pat. That's about the only way to do it unless you are duplicating a design.
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When I did BBO's and BBH's I start out with a 3/8" thick core with 1/8" thick bamboo on a 64" long bow.At that time it's easily 65 pounds right off the form.Those were D/R bows 1 and 3/8" wide @ fades.Straight Line taper to 1/2" wide tips with a moderate reflex of a couple of inches induced past the back of the handle into the outer half of the limbs.
so i should clarify a few things so i can possibly narrow down the information needed. this is what this bow is but its a flat bow. its not a D/R.
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That'll still be close to the same D/R or not when it comes to estimating thickness's for poundage.It's not hard to nail down close within 5 to 10 pounds the poundage during glue up you want without much tillering afterwards after you make enough of them.Perry reflexed bows are not deflexed any either.I just gave you parameters of what is gotten from a certain length/thickness/and width.I would'nt tiller it down to 40#'s though prior to glueing on bamboo to get 70 #'s.You did'nt state the width you've got now.
If I remember right I think my bamboo was tappered in thickness from 3/16" at fades to 1/8" thick or less at the tips.Thus making the initial fade thickness at 9/16" thick with a 3/8" thick core at fades and 1 and 3/8" wide @ fades.From that a 55# bow can easily be gotten.
To get 70 pounds I would start out a 1.5" wide with those thicknesses' stated on a 64" long bow.
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For the boo to be thin enough your bow will probably be no more than 1 1/2" wide to 1 3/8" wide. I think I'd take that width at least half way out the limbs before tapering to the tips at that weight.
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When I made my BBH I pretty much followed BowEds recipe but my bow is 68'' parallel 1 3/8 wide ,I pre tapered the core lam and I would bet I only spent 20 minutes tillering the bow every body does it different but my belief is 90% of the tiller is done in the detail work before glue up !
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Then again, there’s always a chance to screw up while tillering and end up losing more poundage (well, atleast for me). I’d just save the strip for another bow and keep the finshed bow finished.
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Here is another thought that we over looked he basicly is converting a already floor tillered self bow so Im assuming a handle/fade area of 8-10'', shorter riser then most BB backed bow so he needs to add thickness ?
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Oh shoot I read floor as fully tillered. Well if weight gains the question, maybe 10 to 15 pounds, though I’m assuming that after flattening, tempering, and retillering, it’s gonna be around the same weight, maybe a bit higher.
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Yeah Ritchie, a shorter handle means more working limb, essentially a longer bow as far as the limb thickness is concerned.
I'm a little confused as to what stage the hickory bow is in right now. So it's floor tillered and you are assuming the finished weight is around 55 #'s?
If so flatten the back and glue the bamboo on (add reflex if you want). I don't think it will end up at 75 lbs after you flatten the back and tiller it out, but you have what you have.
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There is a excellent DVD out on this topic by Dean Torges Hunting the bamboo backed bow it covers these type bows A to Z , I found it real helpful , some times with these laminate bows you just have to take your ideas and build them using the Wasg (Wild ass scientific guess) system and see where your at unless your replicating a exsiting bow like was said ,if you come in heavy you have a lot more options , I enjoy trying to get as close as possible off the form as I can , but others enjoy scraping the bow to get there ! These guys around here have saved me a lot of time with there advice its good to pay attention to the details they offer it will save you a lot of time to ! Good luck with your bow look forward to seeing your post !
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so i am looking to out some recurve into this bow. how would i do so? do i recurve it and then back it? or do i back it and recurve it then? also would i use steam? or should i use heat? heat and oil? sorry for the questions i just want to make sure its done right. its for my friend and i dont want him to get hurt should it blow up. the back is flattened and ready for glue up as is the bamboo backing.
As for the stage the bow is in, its floor tillered right now. tiller is looking good and im assuming its around 55-60 lbs as of now.
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If your bow is floor tillered as a self bow its more then likely to thick to recurve or even reflex that much , you will need to get closer to Boweds & Bens recipe typically the recurves are done at glue up using reverse wedges, I have used and curently using reverse wedges on a bow same concept , the tip limb lams need to be thin enough to bend well, especially if your going for steep curves , typically there done in more of a slower reflexed fashion on this type bow , steep curves on laminate bows are hard to do unless using multiple thin lams in the tip areas , but you can get some fair reflex if the single core is thinned down ! With the more reflex or recurve form alignment becomes more critical at least for me ! If you have room to leave your front profile wide it helps with string alignment later ! You could also curf cut the tips to create thinner lams and insert wedges I have never did it that way but guys here have !
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I had to cut some lams today so based on your recurve question I did some hill billy exsperments in the first pic the osage lam is at 0.110 a little under 1/8 '' and with heavy thumb pressure trying to get a tight bend thats the radius I got, the other pic is at 0.055 a little under 1/16 '' and getting tighter but to get any tighter I think you would need to go 0.040 for glue up curfed recurves , Bubby just posted a bow with glue on recurves that might work for you !