Bouncing around ideas while waiting for materials

[Badger]

   I did some tests a few years ago on exceptionally wide osage bows. The results kind of disagreed with my own mass theory.  I built several osage flat bows with stiff handles at about 2" wide to 2 1/4 inches wide. To my surprise the mass came in slightly lower than the 1  1/2" bows. I use to build all my 50# osage bows at about 1 1/8 wide to about 1 1/4 wide. I found I got less set when going wider and I also was adding mass but they were still better performers because of less set. When I bumped them up even wider I fully expected to see a substantial increase in mass but it didn't happen. The bows came out much thinner than I would have expected also. The only way this is possible is if at 1 1/2" wide I was still doing more damage to the wood than I thought I was.

[PatM]

How so?

Thinking behind this is that osage is a good bow wood in general due to having high compression strength while still retaining good elasticity, correct or no?

The narrower limb will undergo more stress per square inch is what is going to be a big factor in stability, like how bownarra mentioned horn width, had not thought about doing something like that, but not sure the stability of doing more than 1 strip side by side like that.

All in all that is why I believe osage would be the premium choice for a core in a design like this as it makes core failure and instability less of a factor due to it's inherent properties that make it a good bow core anyways.

   This sounds long on theory, short in other ways.

[RyanY]

   I did some tests a few years ago on exceptionally wide osage bows. The results kind of disagreed with my own mass theory.  I built several osage flat bows with stiff handles at about 2" wide to 2 1/4 inches wide. To my surprise the mass came in slightly lower than the 1  1/2" bows. I use to build all my 50# osage bows at about 1 1/8 wide to about 1 1/4 wide. I found I got less set when going wider and I also was adding mass but they were still better performers because of less set. When I bumped them up even wider I fully expected to see a substantial increase in mass but it didn't happen. The bows came out much thinner than I would have expected also. The only way this is possible is if at 1 1/2" wide I was still doing more damage to the wood than I thought I was.

This is really interesting. My understanding is that the wood in wider bows is being used more efficiently with less stress/damage due to being thinner allowing it to more easily make the desired bend. The thicker and narrow bows have more mass due to more damaged wood so the total amount of wood is less efficient in energy storage. Do you remember the mass differences between the bows?

[Corvus]

This sounds long on theory, short in other ways.

Well that is kinda the idea behind this thread. I have not done a design like this. Was looking for experiences of others who may have fiddled with the theory behind the narrow/thick construction.

   I did some tests a few years ago on exceptionally wide osage bows. The results kind of disagreed with my own mass theory.  I built several osage flat bows with stiff handles at about 2" wide to 2 1/4 inches wide. To my surprise the mass came in slightly lower than the 1  1/2" bows. I use to build all my 50# osage bows at about 1 1/8 wide to about 1 1/4 wide. I found I got less set when going wider and I also was adding mass but they were still better performers because of less set. When I bumped them up even wider I fully expected to see a substantial increase in mass but it didn't happen. The bows came out much thinner than I would have expected also. The only way this is possible is if at 1 1/2" wide I was still doing more damage to the wood than I thought I was.

That is quite wide, must have been extremely thin. Maybe I will do all 3 identical except for width and thickness to see how that would play out as well. Like widths of 1", 1.5" and 2". Hammering out my design aspects over the next month while waiting for materials to come.

[PatM]

What sort of composites have you made before?     

[willie]

Corvus,
thicker limbs mean that you will be asking the sinew to stretch more than usual and the horn to compress more than usual. This might demand higher quality materiel and workmanship in those layers. expecting the exceptional compression qualities of an osage core to make up the difference may not help unless the horn is cosmetic. cores might be better selected on the basis of shear resisting properties. maple has been proven in modern and traditional composite construction as it is relatively homogenous, being a diffuse porous wood, which osage is not.

that's theory, at least as I understand it

[Corvus]

What sort of composites have you made before?   

I was one of "those"guys. The ones who try to fly before they can walk. So a lot of failed ones lol. Before life got in the way I had 3 successful composites after about 12 failures. "Oh I have woodworking knowledge, lets just start hard" NOPE! Way too many intricacies to these traditional composites to just hope that would work lol. My goal and end design that I had finally ironed out was a mix between crimean tatar and Turkish flight. Which was 1 out of the 3 successes. Other 2 I made for someone else and were more simplistic mongolian style bows of a 3 piece construction(limb+ ear as one with splices at handle/Sal connection).Which were much easier than the original design I failed at a dozen times 😆

@willie

I am not expecting the osage to necessarily make up the difference as there will be quality in the other layers. Though the points you bring there are a big reason I am curious about osage in a thick and narrow setup. It is elastic and takes compression well, should that not make it ideal for a project like that as both tension and compression are higher? Obviously execution has to be "on point" otherwise there is that shear factor. Say that there is quality of execution and materials would there be any reason that osage would not be perfect for a thick and narrow? These will be high quality pieces of osage used for this, no snakey or imperfections that would raise the possible shear factor

[PatM]

The problem will also  be what weight you are going for relative to the narrowness of your design.

 The construction of a composite  is designed to replace the compression and tension abilities of wood so that becomes hardly relevant in the core.

[willie]

It is elastic and takes compression well, should that not make it ideal for a project like that as both tension and compression are higher?

the tension and compression forces are highest at the belly and back surface and are proportionally less towards the middle of the core. conversely, the shear forces are the highest at the center, and lessen towards the front and back surface.

Say that there is quality of execution and materials would there be any reason that osage would not be perfect for a thick and narrow?

osage could be used, although I would avoid a flat grain orientation. I think the logic most composite bowyers use, is that much effort is expended in labor, materiel prep and acquisition with a horn/sinew bow so why not go with the proven core material. good maple is the easiest of the three basic materiels to obtain. If you want to use osage for its compression qualities in a composite combo, it would shine with something like a bamboo backing.

here is an interesting, albeit experiential, design you might consider if you want to do some radical laminating with osage
https://www.reddit.com/r/VirtualBow/comments/b8109p/using_an_evolutionary_algorithm_for_optimizing_a/

[bownarra]

Osage is far from ideal for a hornbow core - regardless of design. It is oily, heavily ring porous and a bit too dense.
Compression abilities etc of a selfbow bowwood are irelavent in the core wood of a composite. It will make no difference to the performance. The wood is there simply to give the bow its shape and its stability.
If I were you I would definitely save the osage for where it shines and use maple or bamboo for the core.
How many historical hornbows had osage cores!? All these sort of questions have been answered/tried/ etc and the consensus remains. No need to re-invent the wheel
I have made osage cored hornbows before and you will have to use a modern epoxy for a good horn/core bond.

[Corvus]

It is oily, heavily ring porous and a bit too dense.

This is something I kept going over in my head yesterday before you mentioning this lol. Going to just save it and do some boo backed setups with modern glues is where I think the osage will go.

Not a big fan of boo as a core though and my last ones were all maple cores. So guess part of it was for the aesthetic lol. I have some semi-translucent horn coming and I kinda want to put a nice looking core wood behind it. I find maple rather bland after many years in the trades. I know it is a solid core, but feel there are a lot of options with similar qualities I am not thinking of

[PatM]

Do you have any pictures of your previous bows?   

[Corvus]

Do you have any pictures of your previous bows?

If I can manage to track the guy down then might dig some up. Been through 4 computers and half a dozen phones at this point, any I had are long gone.

On another note if I wanted to fiddle with stuff and slap something together while I wait my choices are kinda crap. Only soft maples around here. Basically limited to sitka spruce and Western hemlock as choices ( best out of my options, not very good options lol), unless I can find a stray dogwood as those are around in a lot of landscaping here.

P.S. NVM forgot there is good yew here, so will find some yew or if someone loses a dogwood to a windstorm( saw one last storm, but was already chopped up by time I came back by)