Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on May 17, 2018, 12:28:52 pm
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I know it doesn't happen all that often but if you have the occasion to remove wood from the back of a bow does 10 scrapes on the back equal 10 scrapes on the belly? This is a very generic question, I have nothing in mind as to wood or design.
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I don't think so.It's all about initial thickness in that area.I've never paid attention to whether it's compression side or tension side removal on backed bows.
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I think it would be the same because it is the thickness that we are adjusting.
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Your question got my brain thinking I'm asumming your talking backed bows also ,as in a peace of wood that's not following a growth ring , but if I'm thinking about it right as Ed said in terms of thickness if you took these lams spliced them together threw a handle/fades on the designated belly side and cut in the taper on the back side ,glued on the backing, the over all composite would have the same taper & thickness as doing it the other way around , by changing the thickness in any given area on the now flat belly would have the same tiller effect ? Is this a brain teaser question ?...lol
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If you are assuming a rectangular uniform material cross section, then beam theory can roughly be applied and taking 10 scrapes from the top or the bottom theoretically wouldn't make a difference. In real life, the top and bottom are not of uniform shape and in the case of a backed bow aren't of uniform strengths.
Hypothetical non exact examples: A maple backed ipe bow. 5 scrapes of ipe belly might equal 10 scrapes of the maple back since the strengths are so different.
An all maple pyramid board bow. 10 scrapes on the top would roughly equal 10 scrapes on the bottom.
Taking a ratio of the different woods MOE's would give you a rough estimate of the value of your scrapes. Like you mentioned, a very open ended question.
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Core thickness dimensions achieved before putting a backing on is what I assumed the question was about.Not afterward while tillering.It's best to not put yourself in that situation in the first place.For lack of core thickness to consider removing material from the back.
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But in the end regardless of what wood is used doesn't it boil down to thickness in any given area as far as tiller change ? Maybe I'm thinking about it wrong ?
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I posted at the same time as you did Ed but that's how I thought of it in terms of the core but doesn't the same apply in Bens example it were talking over all thickness ?
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Ritch.....Normally for these laminated glue ups even if it was spliced I would put the side I tapered with my hand planer to the belly side.I would pre taper those billets before adding the backing and the handle.I'm no laminated bow making expert though.It just makes sense to me.
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Ben has a good point though to consider about density differences.
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Yea I agree with the taper on the belly side I was just posting that as a example in terms of effect wouldn't it be the same on the over all bend ?
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From what I understand from your previous question would'nt you put the handle then on the back of the bow?Or am I missing something here?
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No I was just saying regardless of how the matrix of the core is laid out meaning if the core was tapered under the backing strip instead of the belly and the handle fades where tapered into the flat belly wouldnt the bend be the same ? all limb thicknesses would be the same regardless of how they got there ?
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Your question got my brain thinking I'm asumming your talking backed bows also ,as in a peace of wood that's not following a growth ring , but if I'm thinking about it right as Ed said in terms of thickness if you took these lams spliced them together threw a handle/fades on the designated belly side and cut in the taper on the back side ,glued on the backing, the over all composite would have the same taper & thickness as doing it the other way around , by changing the thickness in any given area on the now flat belly would have the same tiller effect ? Is this a brain teaser question ?...lol
I backed a bow with a strip of wood following a growth ring and then reduced the weight by working the backing down another ring.
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Pat M....On a perfect piece of backing wood that is possible but they are far and few between too.
Ritch....Yes I see what you are saying now.
DC...Regardlesss,I guess it is an option to consider though if things got tight but I would'nt care to put the bow in that situation.Maybe a first time try at woods not familiar with.Then on the next bow make the adjustment.
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This is a interesting topic, I'm not sure where any where near what the OP was thinking ;D but I see all the points in any of the above , it would really be no different in trap tillering a bow or adding sinew to a certain area on the back , or if you had a fixed belly lam thickness and needed to make a adjustment or tillering the back while reverse string prior to sinew , thickness is thickness regardless where it is in the wood in most cases its violated under the backing any way ,except in Patm example which still is a thickness change , when backing a bow the core becomes gender neutral so to speak (=)