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Dennis La Varenne
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#1 Post by Dennis La Varenne » Mon Jul 16, 2012 9:29 pm

To Everyone,

Here is the table. It is that taken from the following thread - http://www.ozbow.net/phpBB3/viewtopic.php?f=34&t=12658 - if you want to read any discussion on the original topic

There were a lot of surprises for me when the numbers were crunched. I was very surprised at how many Australian wood species scored higher than 0.300 in my table compared to the classic bow woods listed at the start of the table.

There is an explanation of how I allocated a score to each of the woods at the end of the table. One wood specie in particular had an an almost unbelievable score close to 0.400.

Anyway, here it is for you to peruse and have a pick over. Please remember that it is NOT a predictor of how any particular wood specie will perform as a bow. It is only an indicator of which Australian wood species have the potential to be good bow woods compared to known classic bow woods.

Some woods have inherent problems presenting to bowyers such as gum pockets and gum veins which cause bows to break. Others have a grain structure which is too short for bowmaking unless the bow is backed, and so forth.

In a perfect world where everything else is equal from a bowyer's perspective, this table should help in the selection of suitable wood species from within this country, and potentially, result in bows at least the equal of anything from overseas.
Dennis La Varénne

Have the courage to argue your beliefs with conviction, but the humility to accept that you may be wrong.

QVIS CVSTODIET IPSOS CVSTODES (Who polices the police?) - DECIMVS IVNIVS IVVENALIS (Juvenal) - Satire VI, lines 347–8

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HOMO LVPVS HOMINIS - Man is his own predator.

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#2 Post by Hugh_mungus » Wed Jan 11, 2017 9:24 pm

I hate to be a nuisance bringing up such an old post, but after searching for a decent guide for Aussie woods I came across your work here. I have noticed though that the calculation you produced mistakenly favours woods with a high moe to mor ratio, explaining the anomaly of seeming low scores for proven woods like Osage, and outstanding scores for species like white ash. I think in actuality it is important to use a wood with a high mor (allowing the bow to withstand perpendicular forces without breaking) as well as having a low moe (allowing the bow to bend enough to a full draw)

I have a copy of the book you used for the data and will post up a revised version for comparative purposes. I will prppaply use a formula something like:

(mor/Moe)×mor = score

Which would give a score that not only acknowledges the ratio between the two values, but not exclude woods with exceptional breaking strengths and higher Moe values, such as massarandurma.

This could further be modified to include weight as a factor simply by multipling by the specific gravity of the wood. This would prevent excluding woods with lower weights and related mor values, like yew.

(Mor/Moe)×mor×(1/specific gravity) = score

A factor often overlooked is the crushing strength of the wood (in theory this would possibly help prevent compression fractures developing on the belly of the bow). To do this simply factor in the modulus into the equation (although I can't seem this entirely useful until I crunch the numbers) giving:

(Mor/Moe)×mor×max crushing strength×(1/specific gravity) = score

Simply put this would favour a wood with:
High modulus of rupture
Low modulus of elasticity (lower is better, with less resistance to elastic deformation)
High maximum compressive strength
Low weight

I think you have done an excellent job at creating the summary so far and your findings were a pleasure to study. I will post back when I have created a modified list of my own, hopefully we still see some natives score up with the big names.


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#3 Post by bigbob » Thu Jan 12, 2017 6:25 pm

not sure if you realise but the author , Dennis is no longer with us (passed away recently) so will be unable to comment personally re your findings.
nil illigitimo in desperandum carborundum

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