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Elasticity versus poundage

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mikekeswick:
Interesting to hear others thoughts on the subject but all that determines poundage is the overall thickness. The varying ratios of the three materials would change things very little. However it would be a bad idea to go too thin on the wood as that is what gives the bow its shape and lateral rigidity. The ideal is to have the total thickness evenly divided by the three materials to make best use of their different properties.

joachimM:

--- Quote from: mikekeswick on March 20, 2017, 03:28:32 am ---Interesting to hear others thoughts on the subject but all that determines poundage is the overall thickness. The varying ratios of the three materials would change things very little. However it would be a bad idea to go too thin on the wood as that is what gives the bow its shape and lateral rigidity. The ideal is to have the total thickness evenly divided by the three materials to make best use of their different properties.

--- End quote ---

My thoughts too. poundage doesn't come from the core, but from the distance the working portions (sinew back and horn belly) are from the neutral plane, hence thickness. If the core is too thick (strain>1.5% - the backing does hold down splinters so it tolerates higher strain than unbacked bows), it will break just like a normal bow, no matter how much sinew and horn you have. If it's too thin, it will tend to twist when put under high strain.
You could add some sinew to increase thickness and hence poundage, but in the end you might end up with a sluggish bow as the first 2 layers of sinew are close to being dead but heavy mass.

It's good to experiment and question existing designs. However, most of the time there's a good reason for a particular design.

Stick Bender:
Thanks for the answer Mike I couldn't wrap my brain around the ratio vs strength but it makes sense for draw weight I was confusing weight vs performance which would be another whole  thread but a interesting one thanks for posting learning a lot here Ed !  (=)

BowEd:
Thanks fellas.Great comments.Overall thickness/staying within the design....that all makes sense for ease of final tillering.Too much horn makes it more unstable or a bit wonky I call it.Can only imagine at the moment what it's like making an all horn/horn sinew bow.This current bow is close to the 1/3,1/3,1/3 ratio yet of components with the core being a shade more ratio wise.Overall thickness is the same as previous bow but like said 2" shorter overall.Overall mass comparing to the last one is the same too but like said again can depend a lot on what component having the most mass for poundage for performance.Horn versus core mostly.Keeping the ratio within reason is good.Crowning the sinew will help with performance.Tapering components before sinewing to put the most material where it is needed and bend the way it should is a bit like self bow making to refer to.I guess I just wanted to stir the pot a little on this thread.Maybe others considering making a horn bow will learn a little.Seems the only way to learn making these bows right is Adam Karpowiczes book mostly.Most people who make these type bows are accomplished bow makers referring themselves to that book and a lot of people don't have it.
They are fun to make but are not quite like the ease of roughing out a stave to a bow and making a fat 3/8" line along the side for a taper that's for sure like said again but really don't require any more sophisticated type tools or equipment,but some are just different that's all.Making calculated measurements of each component etc.Making these makes a person think quite abit more about different forces going on etc. too.In the end getting a deeper understanding of bow making IMO.

BowEd:
joachimM....The koreans at times use rather thin layers of sinew.Total of 2mm at most.Mostly on bamboo though?Reflexed from the handle etc.
I've done some extensive testing with the previous bow I made and it does shoot comparitively right up there with other horn bows listed in Adams' testing list.Using FF string though of 2gpp.Curious to see if any at all difference there is with this one.
I should apologize to Pat B probably but not sure if what he stated was meant about the ratios of components or the lengths of bows getting sinew depleteing performance.In the past it was discussed extensively that longer bows up to 64" did'nt benefit from sinewing.I've proven here if put where it works it does enhance performance.

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