Can making a bow wider lower the mass

[Badger]

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

  I know what you are talking about Jawge, I just finished an osage bow 66" long 1 1/8 wide, which is pretty typical even though I had started at 1 3/8 and the bow allowed me to narrow it. I have several osage bows that are 1 1/2". Learning how to read the wood is the real key.

[blackhawk]

Ha...Im sealing up a narrow hoohornbeam with a crowned belly that is borderline adhering to the 5/8's rule and I'm loving it .... the narrow, round n crowned belly guys are gonna flip hearing this,and i hope some of them chime in.....ya know I love making all kinds of bows from all those of different woods with all kinds of widths and cross sections.... it just depends on what type of bow I'm making,and the intended bows stats, and the type of wood that dictates width and cross section....I find if I do my job well they all perform well for me as long as they all have acceptable mass...and I find you can be plus a couple ounces or even a lil more than a intended target weight and still have a smoking good bow...the mass theory is still very credible IMO,and a good tool and guideline for folks wanting to lose some unwanted "fat" from there bows...it makes them reduce mass where it needs to be reduced(outer limbs),and put mass where it needs to be(inner limbs)..and yes a good bow will be by default lowest possible mass without eventually breaking down and taking too much loss from the start....to me its not so much about hitting a intended target weight as it is about having the right amount of wood where its needed,and NOT needed...I think Tim bakers "mantra" says it best in simple layman's terms..and I quote " make inner limbs wide or long enough for virtually no set. Make midlimbswide enough for little set. Make outer limbs and tips narrow enough for lowest possible mass". That statement is so simply understood and said,but at the same time it is an extremely difficult thing to understand as well as it takes a lot of bows made and experience to start to comprehend how to layout and make a bow with that in mind beforehand...

[George Tsoukalas]

Sure is, Steve. It can be a hard lesson to learn. Jawge

[George Tsoukalas]

Oh forgot to mention, Steve, that this bow started straight and ended up with less than an inch of set.  Jawge

[Bryce]

Yep! Tension/compression value is an ever changing variable.

[Marc St Louis]

I was thinking about this last night Steve and I think that in many cases you may be right.  Take for instance a HHB bow, no heat-treating.  If what you want to make is a stiff handle bow pulling 60# at 28" and you want to make the bow 64" ~ 65" long with 1 3/4" wide limbs, which are acceptable dimensions.  This would give you a bow with low set and of a certain mass.  If you narrow the limbs by 50% and increase the thickness appropriately then the bow will likely have slightly less mass but will also take more set so to compensate for this, to maintain the same low set, you would have to make it longer.  This would increase the mass again and you could very well end up with a bow of the same mass as the wide limb bow or perhaps even more mass.  I'm sure that there is an optimum mass for every wood type, bow style.  It is certainly something to think about

[Badger]

  Mark, I have noticed your bows are all relatively low mass but not unduly narrow in profile. I always attributed that to flat limbs and good tillering. I have been rethinking how I treat different designs and woods lately. I have always felt that my biggest personnal challenge is perfecting methods for reading the condition of the wood as a bow progresses. I hate tillering flat bellied bows so usually end up slightly rounded but I have much better results with dead flat.

[tom sawyer]

I wouldn't necessarily say that a bow that shows no hysteresis after unstringing is better.  My thought is that just a little of this, an inch or less, indicates that the bow is not overbuilt.

[dragonman]

I have also experimented with this....my experience is that the softer more elastic woods like yew and elm need to be narrower and thicker to get the wood to  "work"...but the stiffer and less flexible hard tropical woods work better  with the limbs flat and thin ( that is thin in depth)
With bamboo if you dont stress it enough you dont  get it working properly because its so flexible, the same with horn.....some woods work better when stressed more.....the harder woods like ipe are so stiff that wide thin flat works best...common sense realy

Badger have you concluded then, that the 8:1 width to depth ratio you talk about and BB talks about is no longer aplicable?

[PatM]

Most people say the exact opposite about Ipe, that  it needs to be deeper and narrower to show its best qualities.
 I have made many elm bows of wide and thin dimensions. Some woods work very well no matter what shape or length you give them.

[Badger]

I have also experimented with this....my experience is that the softer more elastic woods like yew and elm need to be narrower and thicker to get the wood to  "work"...but the stiffer and less flexible hard tropical woods work better  with the limbs flat and thin ( that is thin in depth)
With bamboo if you dont stress it enough you dont  get it working properly because its so flexible, the same with horn.....some woods work better when stressed more.....the harder woods like ipe are so stiff that wide thin flat works best...common sense realy

Badger have you concluded then, that the 8:1 width to depth ratio you talk about and BB talks about is no longer aplicable?

   I din't even know I subscribed to a width to depth ratio? I think the depth depends on elasticity and design while the width depends on draw weight. The contention I made starting this post actually applies more to backed bows than self bows because of the flatness we have to work with. I just seem to be getting better results starting off a bit wider than I had in the past. I use my own mass formula as a guage as well as how the wood is reacting. If I have a bow that is say 2" wide but well within my own mass requirements and behaving well I will leave it wide. If the bow is behaving well but very high in mass I will start reducing width until it conforms but monitoring the condition of the wood as my draw lenght increases. I have found anytime I can't get the mas down where I want it high moisture is usually the cause.

[dragonman]

maybe there are too many variables to draw conclusions?  My ipe recurves definately show less set  and a faster return after unstringing with  wider totaly flat  limbs, but I'm only talking small differences...I would call narrow 1"- 1 1/8"  and wide 1 3/8"   , I have even had compression fractures on the belly with narrow ipe bows of heavier weight.... just my subjective experience, not saying it proves anything....and I think ipe comes in sub species and diferent qualities..so hard to draw accurate conclusions

[dragonman]

badger sorry I didnt explain propery and our messages overlapped

what I meant was that if you increase the width by 8mm then that is equilivent to increasing the depth by 1 mm ,in increasing limb strength.....I think you said 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. isnt this saying the same thing as 1:8?

[Badger]

badger sorry I didnt explain propery and our messages overlapped

what I meant was that if you increase the width by 8mm then that is equilivent to increasing the depth by 1 mm ,in increasing limb strength.....I think you said 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. isnt this saying the same thing as 1:8?

  I see what you mean, thats just a standard engineering formula I believe, double the thickness 8 times as strong,

[Marc St Louis]

My experience is also that narrow Ipe bows are better.

Steve
You must remember the Bamboo backed Ipe blank you sent me years ago.  It was extremely narrow at 7/8" with a very thick Bamboo backing, the bow was a nightmare to tiller out.  If I remember right I tillered it out as a flightbow, 25" or 26" draw.  You won the auction at paleo and when you tested the bow you said it was extremely fast.  I was wondering why that bow was so fast, I do have a theory.