Saturday, 30 March 2013

Hickory Challenge Result!

One of the reasons for doing this is to test the received wisdom.
Can a bow with 3" set be restored?
Can you tiller a hickory bow the day after heat treatment without allowing it to re-acclimatise / re-hydrate?

I rasped the tips much slimmer and put on horn overlays onto the back with a string groove filed in. You'll see that the tip is greatly reduced, but the original string grooves on the side of the bow are still visible, thus I've removed all that weight with no loss of strength.
With the old string the brace height is only about 3" now due to the slimmer tips allowing the string loops more slack.

Before putting it on the tiller I'd rasped some off the belly over the outer 1/3 of each limb. This was because I'd noticed that all the set on the bow was on the inner 2/3 of the limbs, so I assumed the outer thirds weren't working enough.
I put it on the tiller and winched it back to 50# I could see the top limb was a bit stiff, the lower limb wasn't too bad. It only came back to about 20". Excellent, that meant I had some poundage to play with and could remove some along the belly of both limbs getting a better tiller and a squarer cross section rather than the very rounded belly.
The 'classic D' section or 'high arched belly' of a longbow is a bit of an exaggeration, the Victorian bows were like that but the bows from the Mary Rose were more square or round with a slight flattening on the back.
Mind, actually looking closely at the capital letter 'D' it's not too bad an approximation if you round the back a bit.

I also took the corners off the back and rounded it a whisker.
This was done in degrees of course and slowly got me back to about 50# at 26" on the low brace.
Ah, yes, the string! A horrid thing of Dacron and much too thick with far too much serving weighing it down, not to mention a nasty heavy brass nocking point.
In the interests of a fair comparison I could make a Dacron string I s'pose, but I've got better things to do than make bad strings, so I found an Angel Majesty string that was about right and twisted it up an extra 20 turns to get it to fit, with a slightly lower brace height which gives a longer power stroke.
The tiller looks pretty good now, I think the upper (right) limb could probably flex a whisker more, but it's not worth messing about with.
I'll sand it down and give it a second coat of varnish (quick drying water based (acrylic?) ). I normally use it on my arrows as a wiped on finish, it's not very nice for a bow.

Results:-
5.7" Brace
~52# @28" (you can see in the full draw shot, it's a whisker over 28")
1" Set

Speed fps
162.0
164.3
167.9

That's an average of  164.7 fps (previous average was 141.4)
Pretty conclusive improvement. A rule of thumb is 100fps added to the draw weight gives an approximate speed, so you can see, it was below par before I tweaked it and now it's above par.
One has to be cautious, because after a few sessions of shooting it could well deteriorate, but I feel the bow is more evenly stressed now, and would hope it stays above the old speed.

Big Bow Update:- It will have had another two coats of Danish Oil by tonight making a total of 4, ready for a good wipe of beeswax polish in the morning ready for some shooting.




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