many thanks for your nice compliments guys!!!
I'm surprised of that many replies, will answer the questions.
first: I'will do the requested measurements tomorrow and post it then
Your work is inspirational! You make it look so easy 
I'm really loving the hollow limb bows you've been turning out, gonna have to try that eventually 
thank you for sharing!
Yes Will, go for that. I'm convinced that HLD has really great potential and it would be great to share the results here
Hi Simson, what specific species is the elder you use?
I 've made a couple of elder bows nows and really rate it as a bow wood. Low density, very elastic and able to take lots of compression with no chrysals around pin knots.
Nice bow you have made there!
So is your thinking behind hollowing the limbs out anything to do with the poisson effect, mass reduction without affecting stiffness and/or just the thin edges you end up with on these short of sapling bows? My mind keeps on thinking about the 'snap' effect that happens when you keep extending a metal tape measure......let off at the end of draw maybe???
We need some tests doing with this design to see how it compares to a standard limb cross section.
Mike, that is sambucus niger.
I did a copy from an answer given to Gun Doc in this thread:
http://www.primitivearcher.com/smf/index.php/topic,41863.0.html1. 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.
Such a beauty!!! soo elegant!
what kind of tool did you used for tillering?
cant wait for my elderberry to dry
Please go to:
http://www.primitivearcher.com/smf/index.php/topic,41217.0.htmlhere you can see how it is done
Yep, got some elder myself!!!! Have just made a molly kind of bow out of half of it. Not decided if I am going to leave it as is or do some experimenting - thought of het treating a lot, scraping and reducing draw weight so that I can put some recurve into it, sinewing the back and even putting some horn on the belly a first for me. Any thoughts on the ideas, ever done them with elder?
Not trying to get in the way (again) your bows are just something to aspire to. Elder is great bow wood, I think it is sambucus nigra around here for those of you wondering Thanks once again Yoda simon for your thoughts
Peter
If I were you: no horn on the belly, sinewing works for sure, heat treating also - but hard to say without seeing the stave ...
every time i see one of your HLD bows i drool man! such a kool idea, how did you think of trying that? or did you learn from some one. gorgeous bow right there
more or less by accident, I had a stave with very high crown and had the only opportunity to decrown (what I did not want), so I searched for other possibilties ... and voila - the HLD was born
Yes Sir Simon!
That's a Beauty!
I Love your HLD Bows...
Will definitely be looking for a Stave or Two to try this design on
once I complete my current Track... Wide/Flat Belly/Molly.... Sort of.
Keep up the Great Work!
I am watching and Learning.
-gus
Yes Gus come on. I'm hungry for what others make out of HLD
Really cool, something I have always wanted to try. Be interesting to put that bow through its paces and see how it performs as opposed to another similar bow. I imagine it would fare well.
Steve, being German I don't understand what you mean with 'put through its paces' ? Do you have a testing idea? What can I do? And yes I'm waiting for a stave which could be split in a half. one for HLD the other conventiaonal design to compare.
All my experience, my feel as a bowmaker, convinces me the HLD is much more efficiant. I hope I can rent a chrono in summer then I willl do fps measurements on all HLD bows I have.
I will call you Sir Simson from now on 
That is amazing. How does the HLD affect the performance? Are they more or less prone to splitting...?
Thank you and keep em comin.
DuBois, please see answer above. and no, till now no splitting and no chrysals
