Can making a bow wider lower the mass

[Badger]

   I was sugested a start a seperate thread on this. Over the past couple of years I have played around with making bows much wider than I normally do. The idea being just tiller them out and then reduce to desired weight by narrowing the limbs. I like to use the mass principle for letting me know that I have a sufficient amount of wood to work with to accomplish a specific design.

    More and more I have been pleasently surprised at how low in mass these wide limbed bows are comming out. I have also found them to be extremely low in hysteris, take very little set and perform at a much higher level. This sounds a little counter intuitive at first glance. Most of us know that if we add 25% to the width we only gain 25% draw weight, if we add 25% to the thickess we double draw weight. I am finding out that if I keep the bellies very flat I can reduce the thickess enough to overcome the added mass expected with added width. This can only be true if the narrower bows are crushing more wood than some of us thought. I find this more true on hard backed bows using flat wood backings.

    I noticed this same thing when examining Mark St Louis bows. I saw very flat bottoms, fairly wide limbs yet always low in overall mass. Any thoughts or debates welcome.

[Bryce]

I have had a similar experience, BUT! Only to a certain degree. I think for each wood there is a proper width:thickness:length ratio that adjustable for draw length and weight, and finding such is too difficult a complicated to even try bc of woods natural way of always being different than the piece before.
I find myself thinking less and less about it and focus more on just making a bow that takes minimal set and shoot a heavy arrow hard.

[JonW]

I can actually contribute to a thread! I don't do any weighing of my bow's physical weight but I can sure feel it in what you are describing. If I come across a good stave that is fairly wide and clean it is always going to be a shorty pyramid. I noticed that this design was making some good bows as far as a lack of set goes. Some of my Osage and Locust short pyramid bows are incredibly light in the hand. I rarely make anything under 50 pounds in draw and more often than not quite a bit over that. I really didn't give much thought to it but when Steve made that comment the proverbial "bulb" lit up. There is definitely something to this line of thought.

[Badger]

I have had a similar experience, BUT! Only to a certain degree. I think for each wood there is a proper width:thickness:length ratio that adjustable for draw length and weight, and finding such is too difficult a complicated to even try bc of woods natural way of always being different than the piece before.
I find myself thinking less and less about it and focus more on just making a bow that takes minimal set and shoot a heavy arrow hard.

  Bryce, you are right on, what we struggle with is trying to identify the character of the stave we have in our hand durring the building process before we have gone too far. I have always felt that going a bit wider and narrowing afterward was a fair way to accomplish this, I was just surprised at how wide I could actually go before the point of deminishing returns sets in. Patience is not one of my greatest virtues and the wide flat limbs are a bit more touchy to tiller.

[Crogacht]

Oh no, I was just starting to get my head around things and now you guys are changing the rules again, argghhhhh 

(But really, this is interesting and excellent and I'll read what you guys come up with  )

[mikekeswick]

If the wood cells get less damaged getting to full draw then they are going to have more stiffness per mass once there = lower physical weight proportionately for  equal draw weight.

[Badger]

If the wood cells get less damaged getting to full draw then they are going to have more stiffness per mass once there = lower physical weight proportionately for  equal draw weight.

   Its not really changing the rules as much as it is understanding them better, same rules would still apply. For my personnal program I intend to start them off about 25% wider than I had been in the past. If I am comming into heavy I can always reduce the width after.

[JonW]

I started using a bendy pyramid design for short bows based on what I was NOT getting in the set department. I got tired of reflexing the narrower designs and just kept getting good results from a pyramid design. If you want to go short go wide IMO

[Badly Bent]

I'm thinking there is something valid in this idea. Without really knowing why I have been thinking of going wider and thinner on the next stave that gives me enough width for it. About 6 months ago I made a buckthorn shorty that was wider than my usual and had very thin limbs for its 51# @ 24" draw. Had some natural set back at the handle and I added a little more reflex to bring the tips 2" ahead of the handle expecting 1-1/4" or more of set. Ended up taking only about 1/2" set and has taken no more after several hundred arrows shot, springs right back after unstringing too.
At 53" long it came in at around 8 oz. prior to adding handle, finish and string. Not sure where that falls in line with your mass principle Steve but it feels like a feather in the hand and cast is good for one made by me.
Ooops, just went and measured the width to make sure I was accurate in my description of this example bow and it is actually only slightly over 1-1/2" wide. Not that wide I guess, but like I stated very thin limbed for the draw weight.
I'll be looking through my stave collection to find an good candidate of black locust, buckthorn or other wood to try
for a wider thin limbed bow. The thinner limbs do seem to be a challenge to me to tiller well though

[Bogaman]

I think experimentation in our craft is great. I think all of us owe a debt to people like Tim Baker, who has provided us with gobs of bow building info. I also think close to 90 some percent of what we know today is ancient history that we have just rediscovered. It's to  bad some one wasn't writing all that prehistoric info down.
Badger, I suppose I've done a little experimentation  over the years, but it isn't my forte. I just like to whittle on the wood and hope I get a keeper while I'm at it. But, I'm sure I'll keep an eye on this thread to see what you come up with, either for or against;^)

[tom sawyer]

The physics don't support your contention.  I think what you are seeing is that craftsmanship trumps all, and that you can't really ever compare two bows because there are multiple variables that can't all be controlled.  Craftsmanship being one important variable.  A well-made bow is going to be low mass by default.  But all things being equal, the narrowest limb that maximizes the tension/compression without damaging the wood, is going to be most efficient.  All things are never equal though.

[tom sawyer]

You definitely only know if your bow is suffering a bit from hysteresis by observing it right after unstringing after a nice long shooting session.  You'll quite often see an inch or so of set that disappears as the bow recovers.  That temporary set is is more indicative of the relative strength of the spring during use.

[Badger]

The physics don't support your contention.  I think what you are seeing is that craftsmanship trumps all, and that you can't really ever compare two bows because there are multiple variables that can't all be controlled.  Craftsmanship being one important variable.  A well-made bow is going to be low mass by default.  But all things being equal, the narrowest limb that maximizes the tension/compression without damaging the wood, is going to be most efficient.  All things are never equal though.

   Tom, that is my contention that craftsmanship is the determing factor, thats the only thing that could explain wider bows having less mass. Another thing, maybe what many of us thought to be the norrawest effective width might really be a smidge wider than we thought.

[Badger]

You definitely only know if your bow is suffering a bit from hysteresis by observing it right after unstringing after a nice long shooting session.  You'll quite often see an inch or so of set that disappears as the bow recovers.  That temporary set is is more indicative of the relative strength of the spring during use.

  I agree with you Tom, a bow that stays the same right after unstringing is better to me than a bow that gains reflex.

[George Tsoukalas]

Steve, I always let the stave decide on width.
Here is what I mean.
I start out with a certain width...perhaps 1.5 inches. Let's say I want 48#.
As I tiller I may note the wood not responding to thickness removal. Than. I begin to narrow the  width to bring the tiller in.
There seems to be a certain width to length to poundage relationship that is specific to each stave.
My last bow (hickory)  turned out 1.25 in wide 65" in length and 48#.
I will admit that I wanted a narrow bow but the bow is light in weight.
That's all I have for now.
Jawge