Ash "holmegård" (pics)

[adb]

Kviljo,

Notice the proportion of outer to inner limb. I usually go 2/3, 1/3, making the stiff non-bending outer limbs no more than 12", regardless of bow length. There has to be more bending than non-bending limb. Otherwise, the bow will take huge set, and will crysall at the fades.

I have broken 2 Holmegaards over the years, but they have both been at the distal taper, not at the fade. Probably the best Holmie I've made was a 62" hickory backed osage, 55# @ 27". A screamer. Cast was incredible. Alas, but happily, it is in the hands of the person I made it for.

[adb]

Hey, Oldbow

Full draw pic is posted.

[Shooter]

kviljo, nice work with the ash. Hard stuff to finesse without having it crush itself. Respect

adb3112, beeee-m

[adb]

Shooter,

beeee-m? I don't get it?

[Shooter]

sorry...I dunno how to spell it. an expression the kids are using these days when they're wicked impressed

[adb]

Shooter,
LOL. I should know that one, I've got 3 teenage daughters!!
Thanks for the compliment!

[Kviljo]

It's still the same, adb   It is not distributing the stress evenly. But I wouldn't worry if it took so little set.

If made properly, there is no reason they shoul crysal easier at the fades.

What I have been describing is a bow that would distribute the stress evenly along the wide parts of the limbs. And there is no reason to think that the original holmegård bows were not made to distribute the stress evenly.

[Knocker]

Thanks for this discussion Gentlemen.  I had seen photos of Holmegaard bows, but did not understand what made them unique until this thread, and the article by Dennis La Verenne.  This is a more advanced design then I will attempt for a while, but you have both created thought-provoking and beautiful, functional, bows. 

The Holmegaard tiller takes some getting used to looking at, but the non-bending limbs make sense.  They are are mechanical levers right?  Much the same as an atlatl, that doesn't bend itself, but adds mechanical advantage to the projectile.  At first look you would think that getting all of the bend from the inner limb would stress the wood too much, but then you realize that the extension provided by the non-bending limbs does not require the inner limbs to BEND AS FAR to achive draw length, and thus minimizes that stress.

Thanks again,
Keith

[adb]

OK, Kviljo. We agree to disagree! That is the great thing about bow making... there is more than one way.

[Kviljo]

There is more than one way, but only one truth

How can you say that such a bow Dennis La Verenne decribes will distribute the stress evenly?
Do you agree that a bow with even thickness should bend in a perfect circle?

[adb]

Kviljo,
How can I say that the stress is distributed equally? Because I've made several of this tiller type that do, with minimal set, only minimal failures, and none which have crysalled, in both self and backed types. Proof of the pudding...
I agree that a bow with even thickness does not bend in a perfect circle. That's the whole point with a Holmegaard tiller. I don't want the tiller shape to be circular. It seems you're missing the point. I don't want a "Holmegaard" shaped bow which is circularilly or elliptically tillered. You lose all the advantages of this design.

Delphilabs,
Yes, the non-bending outer limbs act as levers, increasing cast, but reducing string angle at full draw. You've hit the nail on the head with the inner and outer limbs, and how they relate. This design is about 9000 years old. The skill of Neolithic bowyers is incredible, when you come to understand this bow's design. Highly efficient. A marvel of physics and engineering. Our archery ancestors were truly ingenious.

[Kviljo]

No no

Theoretically, do you agree that a bow which has even thickness along it's whole lenght, should bend like a circle, to be evenly stressed?
The answer is yes, and the reason is that the thickness decides how much the wood can bend before it breaks. More thickness and you won't be able to bend it as far before it breaks. Less thickness and you can bend it further without damaging the wood. If the thickness is the same along the whole bow, then it should also bend just the same along it's whole lenght. Like a perfect circle. That way the stress will be evenly distributed.

If you follow me on this, then you should follow me on the next point too:

To make an even-thickness bow bend like a circle, you have to taper it in width.


Agree?
If not, then were do you stop agreeing?


If you agree with all this, then apply it to a holmegård, and you'll see that if it's inner limbs have even thickness and width, then it is not ideally tillered. Such a bow will have too much dead-weight in the outer part of the wide inner limbs, and too much stress in the inner part of the wide inner limbs.

[kerbinator]

That is really the coolest looking design I have never seen any thing quiet like it

[adb]

Kviljo,
Remember an old truth about wood... any wood. Wood which is twice as wide, is twice as strong. Wood which is twice as thick, is eight times stronger!! The whole point of a Holmegaard tiller is to AVOID a circular tiller. Otherwise, you're just building a regularly tillered bow, with narrowed outer limbs. The entire bow does not have to be "evenly stressed." Only the inner limbs are supposed to bend.

Like I said before, we agree to disagree. That is OK.

[deerhunter97370]

So does the inner limbs have a normal tiller then completely stiff outter limbs? Joel