“Y” or “V” cross section

[SebastianArc]

Just curious as I haven’t found much information out there regarding this kind of cross section, this was me just messing around with a failed yew bow, (badly seasoned , not worth my time haha) I’ve strung it up and seems to be bending quite well, albeit the bad wood.
I’ll try it again on a better piece of wood to really see how it holds up. Has anyone out there had some experience with this kind of cross section and how it went ??

[Kidder]

No personal experience with it, but you are unnecessarily stressing the belly in compression with a design like that. The belly width is only a fraction of what the back is and all the compression forces will be focused at the peak. I would also imagine it would be very difficult to tiller that way as well - because of how narrow the belly is just a few scrapes will drastically impact your bend I believe.

I do believe Simson has made a belly ridged Osage bow successfully so I know it can be done, but his wasn’t as extreme as this. https://primitive-bows.com/osage-fumed-flattie-with-carved-handle-55-28-no-143/

[Aksel]

Ive never seen that cross-section. Looks like a bike saddle. There are bows from the migration period with flat back, flat sides and a triangular belly. And many other strange cross sections from the past. Lots to discover  I believe.

[Digital Caveman]

No personal experience with it, but you are unnecessarily stressing the belly in compression with a design like that. The belly width is only a fraction of what the back is and all the compression forces will be focused at the peak. I would also imagine it would be very difficult to tiller that way as well - because of how narrow the belly is just a few scrapes will drastically impact your bend I believe.

Totally agree.  That's just asking for excessive stress concentrations along the ridge, even if you did manage to tiller it perfectly.  You could do test small samples if you're not sure though.

It looks like a pretty good cross section for stiff tips though.  It would be light and rigid.   

[organic_archer]

The thin strip of wood farthest away from the neutral plane will take all the stress. Will it work? Perhaps. But not efficiently.

[medicinewheel]

Well, from my humble little experience in bow building I would bet that even the most perfect piece of osage will fret mercilessly with this design.
And even if not I second on organic-archer's last statement.

[simk]

my gut also says it's not very reasonable to do so. altough there are lighter victorian longbows that have the v cross section (maybe off-cuts from the sides from a thicker stave where they did not have enough thickness when rounding them......just my thgought). also the burgundian longbows made from laburnum and yew sometimes had a similar cross section (5 corners) => I once made this cross section and the bow worked pretty fine.....not a real V but 5 corners with one on the belly-center....
still do not completly understand the principle....

[Zugul]

I think that could be a good cross section for the levers of a Mollegabet bow, making that part very stiff compared to a "normal" cross section of the same weight. Maybe someone more skilled then me could try this sort of improvement 

[superdav95]

I’ve messed around with this idea on the tips of my molle style bows.  Here’s some pics of the lever on one of my molle bows.  It made the transition look nice and it’s functional in that it reduces mass.  I could have gone even thinner on mine here really. 

[superdav95]

Here’s another one where I dished out the fades a bit to lesson the mass.  Still plenty strong. 

[Jim Davis]

Go ahead. Defy the physics of wood bows. Draw your own personal conclusions from the failures. You can have a personal relationship with the conclusions recorded down through the ages since the invention of writing. Maybe you could test out your own designs for wheels while your are at it. ;-)

[mmattockx]

I’ve messed around with this idea on the tips of my molle style bows.  Here’s some pics of the lever on one of my molle bows.  It made the transition look nice and it’s functional in that it reduces mass.  I could have gone even thinner on mine here really.

Those look great, but you can remove more mass for the same strength if you flipped the triangle around and put the narrow side on the back. That assumes your wood is compression strong as most of our bow woods are. If you were using something tension strong like cherry then your levers are correct.


Mark

[superdav95]

Thanks mmattockx.  These are hickory bows.  There are known for good tension strength as well.  They are ok in compression to.   

[Selfbowman]

Jim I don’t get it. Your an engineer aren’t you. You convinced me with the pyramid! Yes I pushed the limits by putting recurve in the outer limbs. Putting more stress on the inner limbs. But it got faster just saying. Speed is not everything by any means . But is it not good to try to improve your skills?

[Jim Davis]

There are limits to every stress factor. Bow design is limited by the nature of the materials. Nearly every wood is 3 to 4 times stronger in tension than in compression. Reducing the amount of wood that carries the compression load can only reduce the strength of the limb.

If the belly of the bow is narrowed greatly, the narrow ridge (or two ridges) will fail early, but if narrow enough and the limb is thick enough, the stress may be handled successfully by a deeper layer of wood. In that case, the bow will not fail, but will be carrying the failed ridges along for the ride with no benefit from that wood.

Yew has its own rules. I've never used it, but it does well with a thicker rounded belly.

Please forgive my earlier abruptness. I'm 75, and sometimes forget that I was a long time learning a lot of things that others learned earlier.