Another World Record!

[adb]

  Robby, actually he got somewhere around 55% of the energy into the arrow, which is still excellent for a 5.5 grains to the pound arrow.

How do you figure that? I'm not being facetious... I'm interested to know how you calculate the bow's (or any bow for that matter) efficiency.

[adb]

I'd like to know the diameter of the string.  Everyone knows that the surviving Mary Rose arrow nocks "prove" that warbows were only 80-100 pounds because it is impossible to build a natural material string that will hold up to any higher weight and still fit an 8mm nock.
   

That old myth has long since been disproven.

[gianluca100]

@ adb: could you tell more about that? I don't know the current viewpoint of the experts.

Thanks in advance,
gian-luca

[WillS]

Well it's been disproved simply by this record.  Joe is using natural fibre string with EWBS Livery arrows.  Livery arrows have to be 3/8" at the nock end, and the nocks are usually cut with a standard tile saw or standard width bandsaw blade.  They end up generally around 1/8" wide.  Any wider and the strength of the nock is compromised.

Considering that Joe is using a 170# bow here it's fairly apparent that the string withstood the shot.

[gianluca100]

@adb, thanks for your fast reply and the info. So it's not that somebody found out that the nocks did shrink during drying and/or conservation. They really were 3/8 inch wide. So for us metric this is a tiny bit more than 3mm.

I make my linen strings for my 50-55 pounder also that width, with a margin of safety of about 5 to 6 times the bow weight. If I would put that string on 170 pounder the margin of safety would drop to about two times the draw weight and that would be scary low for me 

How much margin of safety do you think is safe for warbows of 120+ weight? Or how low do you dare to go?
On the vessels from the mary rose time they seemed to carry about 4 strings per bow, quite a good reserve. So perhaps they were awaiting some broken strings... or wanted to be on the safe side, being in war...

ciao,
gianni

[Badger]

  Adam, without doing a measured FDC on the bow all I could really do was an estimate. As a general rule a long bow will store energy approx equal to its draw weight. He said the bow shot a 960 grain arrow through the chrono at 210 fps. The arrow had about 94# ft# of kinetic energy which is about 55% of it's draw weight. Just an estimate but likley not too far off.

[adb]

@ adb: could you tell more about that? I don't know the current viewpoint of the experts.

Thanks in advance,
gian-luca

I've disproved that theory myself. I have a linen string (of just slightly more than 1/8" diameter) that I've used on a 120# warbow I made. It withstood multiple shots and the bow and string are fine. The string didn't stretch much, either. That string currently resides full time on a 90# yew self warbow.

[PatM]

The British guys on the Leatherwall foam at the mouth if you mention that a natural material string can be made in smaller diameter and hold up to anything over 100 pounds.
 There is also the draw weight issue as if people back then were planning on having a chronic injury free old age  and thus were careful not to over-bow themselves in their youth.

[WillS]

Yep!  It seems unlikely that in a time of war when archers were desperately sought after, a whole load of manly soldiers were going "Oooh I dunno boss, I'd love to join your elite force into France and keep my family alive while making some decent money, but I'm currently only on a 95# bow and I've read that it's sensible to progress in 5# increments, so I don't think I could handle your military specific 150# bow I'm afraid.  Maybe next year?"

[adb]

I'm sure most have heard this before, but... some of the skeletons recovered from the Mary Rose showed deformation due to shooting heavy draw weight bows over many years. I've been shooting 100# warbows for almost 10 years, and my skeleton has no significant deformation, so it must be caused by something more than that.

I was sceptical too PatM. I always wondered how a natural fiber string could withstand such large forces. I disproved it myself. 120# isn't at the top end, but it's certainly north of the mystical '100# limit.' Also, with no significant reduction in cast, or adverse effects to the string or bow.

[PatM]

I have made strings well up to the task as well. When you mention that you have made a linen string for a bow well over 100 pounds they immediately call you a liar or make disparaging comments about proving manliness as if that is the only reason to attempt to duplicate the old bows.
 The warbow cult is a strange one.

[WillS]

In regards to the deformation of the skeleton - there was a pretty good documentary a while back called Ghosts Of The Mary Rose.  It featured the EWBS shooting, it showed Steve Stratton putting a 170# bow on the tiller but more importantly they scanned Mark Stretton's shoulder after (but not straight after) shooting the Guinness World Record's heaviest bow at 202lbs.  They showed definite and distinct damage to the bone and cartilage of his bow arm due to the compressive forces of the bow.  It wasn't the same as the skeletons on the MR because Mark hasn't been shooting from such a young age - the belief being that young bones are yet to fuse, and repeated damage such as shooting heavy bows is enough to PREVENT the bones from ossifying properly - but it's very clear from that, that these bows DO cause skeletal structure damage with repeated use.  I'll try and find it, and post a link.

[WillS]

Well I found it, far easier than I thought.

http://www.veoh.com/watch/v15536356yKc73mEf?h1=Ghosts+of+the+Mary+Rose

Skip forward to 16:39 minutes in.  And enjoy the EWBS shooting, drool over Steve's beautiful work of art, and check out the medical scan of Mark Stretton.

[PatM]

I don't think anyone would dispute that the potential for damage is there but anything taken to extremes will do that.
 Probably still a fair amount of individual variation in how different guys coped with it.
 Some ex-football players are fine, some are crippled.

[adb]

I have made strings well up to the task as well. When you mention that you have made a linen string for a bow well over 100 pounds they immediately call you a liar or make disparaging comments about proving manliness as if that is the only reason to attempt to duplicate the old bows.
 The warbow cult is a strange one.

Yes it is. Send those wankers our way, and we'll straighten them out.