Stiff woods

[sapling bowyer]

Can we say as a rule of thumb that stiff woods that have been designed efficient for their density make faster bows than other woods? I guess that the stiffer per mass than the less mass is needed for getting to the intended draw weight. Does that make black locust a candidate for very fast bows? Or is it more complicated than that?

[Pat B]

I think it is more in the design and the execution of that design that makes a faster bow. Proper design for specific woods makes a big difference.
 Atmospheric conditions can change the performance potential of some woods also. A hickory bow in dry Arizona could easily out preform an osage bow of the same design because the hickory will be lighter in physical weight. The osage bow in the humid SE US would probably out preform the hickory because of the hygroscopic nature of hickory. 

[bradsmith2010]

its alot more complicated than that

[PlanB]

At absolutely opposite ends of the scale:

Cottonwood, the poplars, spruces are very stiff for their weight.

Osage, Pacific Yew, and Eastern Red Cedar have very low stiffness for their weight.

The answer would seem clear as a "no."

But it might be even more complicated than that......

[sapling bowyer]

Thanks guys

[crooketarrow]

Not really blade Pats hit it right on as I see it.

[joachimM]

In theory, yes. High stiffness woods tend to be able to store more energy per unit of mass. But mass can be distributed such that the mass of the bending portions hardly affects tip and lower limb mass. And then other wood properties come into play too.
So PatB said it already.

Low stiffness woods for their mass are ERC, osage, yew, elm, plum
Medium stiffness woods are ash (some), hickory, maple, black locust, ...
High stiffness woods are birch, eur ash, bulletwood, douglas fir, bamboo ...

All can make very good bows. Low stiffness woods are preferred because they can stand abuse better, including changes in ambient moisture. Moisture management is less critical there.

Bamboo is popular  as a backing because it has high stiffness and being able to tolerate high strain for its stiffness.

But it could be that high stiffness woods also suffer more from hysteresis.

[mikekeswick]

My fastest wood bows have all been black locust. Recurves with deflexed fades and reflexed mid to outer into the recurves.

[Hrothgar]

Realizing that we are saying 'in theory' we pretty much are all on the same page, so what factor or factors cause a light-weight, low modulus of rupture and elasticity wood like hackberry to be preferred over a stronger, heavier wood such as white oak...interlocking grain maybe?

[Badger]

   I have noticed a lot of high stiffness woods also tend to chrysal but are low in hysteresis. Locust can be a very fast wood when done correctly. I have chrysaled most of the locust bows I have worked on. I prefer the low stiffness woods as they give me more design options.

[PlanB]

That brings up a question for me re. chrysalling. In a stiffer type wood, does heat treating increase resistance to chrysalling, decrease it, or not make a difference in people's experience?

Is it possible heat treating reduces tendency to set but at the expense of making chrysalling more likely down the road?

(I don't have an opinion on this yet, just something I'm wondering about.)

[Pat B]

...also, wood availability has a lot to do with why some folks use one wood or another.
  Like Badger I too have had not so good luck with locust. The only locust bows I've made that have not chrysaled I have heat treated but I can't say that is the reason why. Could be I just got better over the years. Most of my locust bows were early on when I first started making wood bows.

[Badger]

   If I stumble across a good maple board I won't pass it up. Maple seems like a pretty stiff wood as well. Some tendency to chrysal but not too bad.

[joachimM]

Realizing that we are saying 'in theory' we pretty much are all on the same page, so what factor or factors cause a light-weight, low modulus of rupture and elasticity wood like hackberry to be preferred over a stronger, heavier wood such as white oak...interlocking grain maybe?

Because these woods are more tolerant to imperfections/errors on the bowyer's part. Most people dont care about having the fastest possible bow, but rather the most reliable bow.

[sapling bowyer]

Realizing that we are saying 'in theory' we pretty much are all on the same page, so what factor or factors cause a light-weight, low modulus of rupture and elasticity wood like hackberry to be preferred over a stronger, heavier wood such as white oak...interlocking grain maybe?

Because these woods are more tolerant to imperfections/errors on the bowyer's part. Most people dont care about having the fastest possible bow, but rather the most reliable bow.

Great point there.