To Build an HLD

[Digital Caveman]

I finally received a scraper set yesterday including a gooseneck scraper.  I now have all the tools to start an HLD bow. 

My question is how does the front-view to tiller shape relation differ in a HLD vs. a solid limb bow? 
On a typical bow with a rectangular cross section a pyramid profile needs a circular tiller.  Is this true for a HLD? 

I think I will start out with ash because I have more small diameter ash, than say, elm, even though elm is much tougher to split.

[willie]

how does the front-view to tiller shape relation differ in a HLD vs. a solid limb bow?

interesting question. I'm curious why you think it might call for a different tiller?

[Digital Caveman]

The limb will have to vary in thickness in order to maintain the same cross section.

[willie]

typical limbs vary in thickness or width or some of both, but I have never thought that one could derive the needed dimensions from the cross sectional area (if that's what you mean)

[Digital Caveman]

I just mean that a pyramid bow in HLD would have a different limb shape than in rectangular cross section.  For example, the limb would have to get thinner as it got narrower.

[RyanY]

I just mean that a pyramid bow in HLD would have a different limb shape than in rectangular cross section.  For example, the limb would have to get thinner as it got narrower.

I think I see where you’re coming from. So if marked out like a typical pyramid bow, the higher crown of the stave would mean the inner limbs are actually wider thanwould be in a rectangular cross section if you were to flatten out the hollow limb. Is that the idea?

[willie]

the recommendation for a pyramid to have a more circular tiller, and a parallel limb to have a more elliptical tiller is based on an assumption that the bowyer is wishing to distribute the strain equally all along the limb. (the limb tapering in thickness, needing to bend more as it gets thinner)

But there designs that call for stiffer tips, which put more strain in the inner limbs intentionally.

One strategy to manage set, is to initially focus on the bend at mid limb, and bring the bend into the near fade area and out to the tip area as set dictates. If your design and wood can accommodate this, why not plan to make the outers more elliptical only if needed?

[Digital Caveman]

I think I see where you’re coming from. So if marked out like a typical pyramid bow, the higher crown of the stave would mean the inner limbs are actually wider than would be in a rectangular cross section if you were to flatten out the hollow limb. Is that the idea?

I mean the high crown would mean that the limb would be thicker front to back if the hollow of the limb maintains more or less continuous shape.  The other thing to consider is that HLDs are strained laterally as well as lengthwise as the limbs flatten out.

[stuckinthemud]

They are a lot of work and a bit wierd to tiller, I've built a few and the masochist in me loves making them but I don't feel confident to answer you. There are a few detailed discussions on this site, a little time searching would be time well spent. Maybe Simon will chime in.

[Digital Caveman]

I like to understand exactly what is going on in any project, but if nothing else I guess I will just follow the instructions and try to understand the mechanics later.

[Allyn T]

There is a video on swiftwoodbows youtube how to do one

[willie]

I like to understand exactly what is going on in any project, but if nothing else I guess I will just follow the instructions and try to understand the mechanics later.

calculate the possion effect on some sample limb sections? or maybe just rip some pvc pipe and play around with it a bit

[simk]

check this 
http://primitive-bows.com/hld-a-new-progressive-design-for-selfbows/

[stuckinthemud]

I have checked through all my posts and can't find a discussion on hld, but reading Simon's blog post,  it is definitely the item I was thinking of. Thanks for posting the link Simk.

[Digital Caveman]

Thanks, that should help