Primitive Archer
Main Discussion Area => Bows => Topic started by: son of massey on July 09, 2014, 02:29:46 pm
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I seen a few posts where comparative builds were made, and the conclusions I seem to recall seeing were that about a 1:1 ratio of working limb to lever is best. Does anyone know if that holds across total bow lengths, or is that more true at shorter or intermediate lengths?
The reason I am wondering this is I have a few ironwood bows in the works for this year's deer season, and for one of them I was considering the Holmegaard (or Mollegabat, whatever) design. It is far longer than any Holmy I have attempted before at a stave length of 73". It can certainly be shortened, but before I did that I found myself wondering if the "beyond 66" efficiency falls off" rule applies to this design as well. Is the trick with these total length or working limb length? And do excessively long levers with regular working limb length help or hurt performance, or do relatively short levers with long (for a Holmegaard) working limbs help of hurt?
SOM
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On the holmguaard bows i've made i've just copied the original as closely as possible and boy do they shoot well. Those guys back then certainly knew a thing or two. ;)
If you google it you can find the dimensions.
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the Holmegaard (or Mollegabat, whatever) design.
Not "whatever". They are distinctly different designs! Please run a google search and compare the two (three) actual archaeological artifacts that were found. The Holmegard is a basic flatbow that has a pretty even width taper, while the Møllegabet bow has an abrupt width taper with shoulders, leading to thick and stiff outer limbs, acting as levers.
I seen a few posts where comparative builds were made, and the conclusions I seem to recall seeing were that about a 1:1 ratio of working limb to lever is best.
I would actually love to see those posts. I can't remember any of such comparisons, so I must have missed them. Could you post the links please?
I've only made one Møllegabet bow myself (link (http://paleoplanet69529.yuku.com/topic/36883)). That one had 2/5ths levers and 3/5ths bending limbs (not counting the handle). I personally like a 2:3 ratio of the lever:bending limb or perhaps the golden ratio would be good as well. A 1:1 ratio doesn't feel right. It looks weird and I'm pretty sure you want more bending limb length to spread the load. I'm sure a longer Møllegabet could handle a 1:1 ratio, but my intuition (not based on facts or measurements) tells me it is not the perfect ratio. Myself, I don't believe that the longer the levers are, the faster the bow will be. The midlimbs are so far away from the tips, that a little bit of extra mass (that means wider, thinner - thus heavier - but bending limbs) there won't slow down the tips, yet help to spread out the load and prevent set. In my opinion, good tiller in these Møllegabet bows, and highly reduced levers, is much more important than the ratio between the two parts of the limbs. It would be a fun experiment to make a Møllegabet bow with 1/3rd bending limbs of 4" wide, and 2/3rds stiff levers.
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Blackhawk has made more of these than probably the original guys did. ;) You can find those lever length comparisons in many of his posts or related posts.
Steve(badger) made a bamboo backed Ipe one with the lever-limb length dramtically skewed in favor of the lever. It didn't have to be that wide though.
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How about making several different ratios and find out what YOU like best and not what someone else says ;) .....I know..I know....not the answer you were looking for....but there's more favorite flavors of kool aid on this site to mention...one person might prefer orange,and another might prefer grape.. Etc etc...... me personally I like my levers to be 33-40%(pending on bow and limb length) of my limb whatever length my bow and limbs are...50/50 does well also(anything more is overkill IMHO),bit its harder to make a smooth transition between lever and working limbs with that ratio,and I prefer the looks of the ratio of what I mentioned previously because you can semi pyramid the limbs and make a much less abrupt,and a smoother transition...and if done right you still get the benefits and advantages of leverage with the levers....
You have some length you can chop of there as well(and I wood if I was making it a hunting bow)...just as long as you have enough width to do so in the stave
One of two of my main hunting bows is a 54" osage semi bendy handle with ~35% of the limbs being reflexed levers....and it has a subtle deflexed handle section....its a great hunting design..for a short bow I shoot it well and am confident out to 20 yards with it...not to mention it rips a mean area too ;) 8) the bow already has blood on its hands too ;) it helped me rid some "pests" recently ;)
http://www.primitivearcher.com/smf/index.php?topic=42911.0
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the Holmegaard (or Mollegabat, whatever) design.
Not "whatever". They are distinctly different designs! Please run a google search and compare the two (three) actual archaeological artifacts that were found. The Holmegard is a basic flatbow that has a pretty even width taper, while the Møllegabet bow has an abrupt width taper with shoulders, leading to thick and stiff outer limbs, acting as levers.
I seen a few posts where comparative builds were made, and the conclusions I seem to recall seeing were that about a 1:1 ratio of working limb to lever is best.
I would actually love to see those posts. I can't remember any of such comparisons, so I must have missed them. Could you post the links please?
I've only made one Møllegabet bow myself (link (http://paleoplanet69529.yuku.com/topic/36883)). That one had 2/5ths levers and 3/5ths bending limbs (not counting the handle). I personally like a 2:3 ratio of the lever:bending limb or perhaps the golden ratio would be good as well. A 1:1 ratio doesn't feel right. It looks weird and I'm pretty sure you want more bending limb length to spread the load. I'm sure a longer Møllegabet could handle a 1:1 ratio, but my intuition (not based on facts or measurements) tells me it is not the perfect ratio. Myself, I don't believe that the longer the levers are, the faster the bow will be. The midlimbs are so far away from the tips, that a little bit of extra mass (that means wider, thinner - thus heavier - but bending limbs) there won't slow down the tips, yet help to spread out the load and prevent set. In my opinion, good tiller in these Møllegabet bows, and highly reduced levers, is much more important than the ratio between the two parts of the limbs. It would be a fun experiment to make a Møllegabet bow with 1/3rd bending limbs of 4" wide, and 2/3rds stiff levers.
I pretty much agree on all point.
The Hjarnø bow which is pretty much contemporay with the Møllegabet fragment, is about 66" long and has a 1/3 ratio of the levers/working limb. 1/3 works very well for me:-)
Cheers
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Thanks for the replies. I will dig through Blackhawk's posts, thanks Pat.
Darksoul, I know the Mol. and Hol. designs are considered different-but way back when I learned it was Holmegaard and I happen to like the name better, accuracy aside. Besides, I am a scientist by trade, I get enough of super specific jargon as it is. I have read a lot of the posts here and other places regarding the name change, and my personal opinion from looking at pieces of these bows is that they were really more like extremes of a design feature so interchanging the names isn't that big a deal-or at least that is what I tell myself so I can sleep at night. I will look for some of those posts, I seem to remember Half Eye was helping with the tillering or made one or two of them...but I don't remember who was really behind the experiment. I think they were also a bit shorter, which partly prompted my initial question.
And this wouldn't be my first of this design, just by far my longest-one of my favorite shooters is a 57" bow in hickory. In general my bows sit a little under 60", so around 70" seems huge...but something about the stave made me think that this is the design to go with.
Blackhawk-I was more curious what is known about the physics/efficiency type of characteristics that these bows have at longer lengths and how it translates to more 'standard' layouts. If it were just personal opinion I would shorten it a good deal, and with just shy of a 2.25" wide bit of hop hornbeam I am not too concerned about having enough wood. But thanks for the general ratios, I will take those under advisement. I was considering relexing the levers slightly as well, I will look for that bow. Is it posted here? Never mind, I see the link now.
Thanks again, SOM
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Is the ratio based on mass or mechanical advantage? The reason I ask is say I have a 12" static limb and I put my nocks 1" from the tip. Do I now have an 11" static limb?
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Here's a small sampling of some of mine showing different bow lengths and ratio "lever" bows as I call them...and all of these bows shoot well regardless of length,ratio,or wood species
http://www.primitivearcher.com/smf/index.php?topic=42911.0
http://www.primitivearcher.com/smf/index.php?topic=35393.0
http://www.primitivearcher.com/smf/index.php/topic,36920.0/nowap.html
http://www.primitivearcher.com/smf/index.php?topic=40916.0
http://www.primitivearcher.com/smf/index.php?topic=32585.0
http://www.primitivearcher.com/smf/index.php?topic=36860.0
http://www.primitivearcher.com/smf/index.php?topic=43511.0
http://www.primitivearcher.com/smf/index.php?topic=44033.0
http://www.primitivearcher.com/smf/index.php/topic,38078.0.html
http://www.primitivearcher.com/smf/index.php?topic=30598.0
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Blackhawk, that third one, the black locust with recurved levers, is still my ideal/goal bow ;) All gorgeous examples.
+1 what's been said about the differences between molles and holmes. I think the modern idea of a holme with the stiff tip/lever but no pronounced shoulder is perfectly functional and beautiful, but I don't know that it's a primitive design ??? I just gave one to a friend; for a while it was my favorite and she loves it.
http://www.primitivearcher.com/smf/index.php/topic,46637.msg636162.html#msg636162 (http://www.primitivearcher.com/smf/index.php/topic,46637.msg636162.html#msg636162)