yew shortbow design advice needed

[stuckinthemud]

Hi All,

I have tillered a 48" long yew shortbow to brace.  At the moment, she draws happily to 18", photo shows draw at 12".  The bow is quite characterful, with several large knots and is little more than a straight stick, 27mm wide through the central 1/2 of the bow, tapering to 14mm at the tips.  The problem I have is the weight - at 12" draw the weight is 25#, rising at 3#per inch of draw, so target weight of 40# is met at about 17" draw. Ideally I would like 24" draw length  - 26 would be nice but I think totally unrealistic. I am nervous about taking out a ring of sapwood as there are only 6 sapwood rings left.  The heartwood reduces from 8 rings in the centre to 3 at the tips. The bow already has 1" of set. As the bow is constant width for half its length, should I be looking at reducing width and refining the tips instead of taking out any more rings?

[blackhawk]

You should be scraping on the belly to finish tiller...only scrape the stiff areas.  It almost sounds like your tillering from the back by how much ya mentioned about taking the sapwood rings off? Your supposed to remove material from the belly not the back. Hope im just misunderstanding this. 

[stuckinthemud]

Hi Blackhawk,

no you're not misunderstanding, but the sapwood was really thick and I have already reduced it by half.  At the moment the sapwood:heartwood ratio is 3:4 at the centre, and I do not know if that is about right or too much in favour of either the sapwood or the heartwood.  The only thing that I do know is that the bow is too strong by about 15#, so I need to explore my options, one of which is to take out one more ring of sapwood, particularly as the bow is showing a little set, which might indicate the heartwood is not what I should be looking at reducing?  Equally, I have left the edge of the back of the bow really sharp, and I could round it over - would that have a similar effect in de-powering the sapwood just a little bit? Or should I be considering trapping the belly, or trapping the back?

[redhawk55]

I double Blackhawk: scrap at the belly the stiff areas. 26" seems to much. The stave seems to be grown with fine growthrings, so 40lbs at 22- 24" would match its capablities.
Michael

[wizardgoat]

At floor tillering stage your sapwood should be the thickness you want.
On lighter weight bows you really don't need a lot of sapwood, no more than 1/4".
You run the risk of running out of heartwood on the belly.
If you want some tiller advice we need to see the bow unbraced, braced, and drawn, but don't draw it
past a weak spot

[Jodocus]

Clean up the back to one ring,  and go on tillering from the belly then. Don't care about sap- or heartwood really, you can make a fine bow from 80% sapwood, no worries.

see this post:

http://www.primitivearcher.com/smf/index.php?topic=2608.0

if you feel it is to wide and you have already made a coupe of bows, otherwise it's better to make it too wide in the inner and mid limbs.

I don't think I'd trap this one. Yew is quite strong in compression and your back probaly isn't perfect either.