Thanks again for that positive response!
Very impressive Sir! I was wondering how long have you been employing this design? More to the point, how is the longevity of a hollow limb design compare to oh....say a flatbow design. I can see some definite advantages to the design, but I would be concerned about the bow splitting itself as the limb flattened out at full draw. Have you noticed any tendencies or signs of that happening ? Would it be your opinion that a highly interlocked grain wood is necessary for this design? I'm very seriously considering giving this a try, so please forgive all the dumb questions. Lol! It looks like a very in depth project that I would prefer to learn as much as possible BEFORE attempting. Which is an entirely new approach for me. Lol! Beautifully done sir! Josh
Josh, I will answeryour questions. But sorry for the long replay, cannot say shorter:
1. Employ, results, longevity
I have made about 20 HLD bows so far, it should be more to get funded results. I began the HLD when I remember right 2010. Some bows were gifted away, some sold and some still in my possession. I never heard of a failure, my bows are still in use. I didn’t notice any chrysal or fret, esp. in the ‘belly walls’. Never had a vertically splitting, even in this one where the hollowed out is extreme. A word to the flatting out, this does not mean that the curved limb becomes a flat limb. You can feel the effect when you hold your hands on the belly of the limb while the bow is drawn (of course by another or on the tree).
I came to this design more or less by accident. A stave had very changing crown (depth), so to get it matched I could have narrowed it on the sides. But then the front profile would have a changing width. I decided to give a hollowed out limb (in that section) a try and that was it. It did work!
2. Advantages
The HLD allows a limb with lower mass compared to flat or lenticular cross section by a given draw weight. The lower mass causes a faster return of the drawn limb, more energy on the arrow – a better cast. HLD bows have a different f/d curve compared to flat bows. There is a steeper curve in the beginning of draw and a milder increase at the last inches, because of the flattening out. I will not say there is something like a let off (like in wheelie bows), but the limbs thickness differs while drawing the bow. You know the limb’s depth is much more critical than the width. Double the width and you get a bow with 2x draw weight. But double the depth you will get a bow with 8x the draw weight. I will say, just a little difference in the limb’s depth (flattening) causes a great effect.
Drawing a HLD bow always reminds me on spring steel, the draw is very smooth and comfortable.
In my opinion the limb’s belly has lower stress compared to the flat profile (see my sketch I the buildalong). The flattening out causes a tension horizontally, perhaps this allows more room for the cells to compress vertically.
3. Bow wood
I have done HLD on osage, elm, yew, hazel, golden chain tree, euonymus europaeus (don’t know the English word), maybe some others I don’t remember now …
At least hazel is marginal bow wood, but I had a surprisingly good result with that specific bow (is posted a few weeks ago), so I cannot say HLD needs a highly interlocked grain like elm. But wouldn’t use a wood gnarly like this with dogleg different reflex and so on anymore, this was a challenge.
4. Design
A stave with a high crown is needed. The depth of the limb (measured over the hollow) compared to the width should be in the ratio of 1:3, otherwise it doesn’t flatten out and you lose a great advantage. The curved wall of the limb must be thin enough to work. The two ends of the wall should have no edges and must be sanded round to prevent excessive stress. These are just my thoughts and experience.
Hope I could help
Seeing forward to your HLD bows guys
cannot wait to share experience!
