Author Topic: Interesting HLD bow explosion (Pic heavy)  (Read 3434 times)

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Offline BoltBows

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Interesting HLD bow explosion (Pic heavy)
« on: November 19, 2018, 07:23:34 am »
Hi there folks!

With a lot of inspiration from Leon (aka Leonwood) and Simon (Simson) I wanted to build a HLD elderberry bow. Leon gave me a great piece of elderberry to use and so it began.
I did try to make an elderberry HLD recurve before, but after heat treatment it failed and developed fatal crystals in the sides near the handle.
The first HLD I tried to make involved a lot of work with gouges and scrapers to get the hollowed out shape. Being a woodworker I decided that could go a hell of a lot quicker!
So I took up one of my granddad's old concave moulding planes. (Not sure what this one is called in English.) And well to put it shit way: It will save you a lot of time ;)

So this HLD elderberry made it to a 28'' tiller when I decided to shorten it a little to get a few lbs extra. It was just under 40 and I wanted about 42-44.
The left limb seems to do way less than the right, but the left limb had quite a kink which resulted in reflex exactly where the knot it, in the middle of the limb!
Quite dodgy, but amazingly it did what it had to.


However, after shortening it, it exploded spectacularly on full draw. So now the interesting part:
It was the right limb that broke, although in the whole process I felt like the left one was gonna go.
And what's more interesting than that, is the way it broke. As you can see on the picture below it split lengthwise for almost half the limb.
It looks very much like the backing of the limb has been broken off because of the limb deformation, although it might have been that little knot you can see in the picture on the left.
however I still think that knot was not the case, because of the fact that the limb halves almost split a cm apart in width.
In my mind this confirms the theorie of the cross section tension which makes this HLD so fast, however this was probably a bit too extreme.

After this happened I wondered what the cross sections looked like exactly, so yeah.. here they are:

Looks pretty good I suppose. I even compared them to Simson's recommendations which are in his tutorial on his website, and I was damn close!
Keeping in mind that he makes even more extreme versions of this, mine should be okay I guess.
So yeah, I probably went a bit too extreme, wanting too much from this piece of wood. But it resulted in an interesting project I think!

Cheers guys, thanks for reading.

Jaap
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Offline Badger

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #1 on: November 19, 2018, 07:30:25 am »
  I don't believe it has ever been confirmed that the hollow limb is a fast design. Have you seen any tests done on it?

Offline leonwood

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #2 on: November 19, 2018, 07:40:08 am »
Hey Jaap, nice to see you posting here! Sorry to see this one explode, thought you made it! The hld cross section looks pretty good to me.
However it also could have been the wood since my broken elderberry from last week and Erics from last month where from the same tree and they all broke!

Offline leonwood

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #3 on: November 19, 2018, 07:45:13 am »
  I don't believe it has ever been confirmed that the hollow limb is a fast design. Have you seen any tests done on it?

Don't believe anyone has ever done any comparison tests, I know for sure my fastest selfbow is a HLD black locust recurve but I am not sure if that has anything to do with the HLD part.

Would be interesting to test it though... Take two staves from the same tree an tiller them at the exact draw weight and mass, one hld and one flat. Would that work???

Offline Bayou Ben

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #4 on: November 19, 2018, 07:47:03 am »
There you have it....if Leon's bow broke from this wood, it's the wood's fault!

Offline Badger

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #5 on: November 19, 2018, 11:42:10 am »
  I don't believe it has ever been confirmed that the hollow limb is a fast design. Have you seen any tests done on it?

Don't believe anyone has ever done any comparison tests, I know for sure my fastest selfbow is a HLD black locust recurve but I am not sure if that has anything to do with the HLD part.

Would be interesting to test it though... Take two staves from the same tree an tiller them at the exact draw weight and mass, one hld and one flat. Would that work???

  That would be an interesting test. Just bottom line performance would also be interesting.

Offline bradsmith2010

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #6 on: November 19, 2018, 11:52:46 am »
better is the enemy of just fine,, (SH)

Offline ohma2

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #7 on: November 19, 2018, 12:00:19 pm »
I agree on the test as mentioned,would be very interesting .yeah 3 bows breaking from the same tree wood does get one wondering.

Offline Weylin

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #8 on: November 19, 2018, 05:15:57 pm »
I'm not sure how accurate the test would be (not that I'm discouraging it) You would need to take a branch from a tree to make the HLD if it's big enough to make a flat bow out of with the trunk. That's already adding another variable. I'm all for playing around with designs to get an idea of what's better or worse but it's just so damn hard with wood bows because there are too many variables that we will just never have control over. I feel like the only reliable data can come from flight shooting/chrono readings from lots of bows over time but even then managing the variables on that can be a headache.

Offline Badger

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #9 on: November 19, 2018, 06:10:18 pm »
I agree with you Weylin, woodbows are virtually impossible to really control variables.

Offline BoltBows

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #10 on: November 20, 2018, 12:19:24 am »
  I don't believe it has ever been confirmed that the hollow limb is a fast design. Have you seen any tests done on it?

Of course you're right there Badger and no I haven’t. Just suspicions!
I agree it would be very interesting to make a lot of HLD bows to somehow compare to ‘normal’ design bows, but yeah it would be hard to truly compare.
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Offline simk

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #11 on: November 20, 2018, 01:35:07 am »
would it be wrong to argue that a HLD profile in general needs less wood/mass to generate same strain/draw weight than other common cross-section designs and therefore should be more competitive? just asking...

Offline Del the cat

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #12 on: November 20, 2018, 02:39:52 am »
Great pics interesting post.
Del
Health warning, these posts may contain traces of nut.

Offline leonwood

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #13 on: November 20, 2018, 05:18:15 am »
You are right Weylin, you just never know with wood. There is so much difference in wood even from the same species that most tests only say something about the specific piece of wood the testbows are made from.

But specifically about HLD bows, I have done quite a lot of them in the last two years and I must say that all of them came out as really good shooters. Especially the whitewood ones from elder and hazel amaze me with the amount of set (almost none) and how they hold up even after a lot of arrows.

This bow for example: http://www.primitivearcher.com/smf/index.php?topic=61803.0

I gave it to to a fellow archer who broke his osage bow and he shoots it a lot. The bow still has no set and even after shooting for a few hours it immediately snaps straight after unbracing. And it still shoots 176 fps

Offline Badger

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Re: Interesting HLD bow explosion (Pic heavy)
« Reply #14 on: November 20, 2018, 07:12:05 am »
That is a good report. I have always wondered of the hollow limb design might be less prone to vibration in the last few inches of the power stroke. Flat bows have some distortion here that looses energy.