Post For Tim Baker ( Sinew)

[Tim Baker]

SpringBuck:

I don't know if you're using a similar method or not, so just in case:

If all the sinew needed for a bow is worked into bundles, then all of the bundles trolled through water till soft and all strands parallel, then you won't be working with raggedy dry sinew which wants to stick to your hands and make life miserable. Sinewing is a breeze when the the bundles are prepared in damp bundles.  Such prepared bundles can also be allowed to dry for future use, a quick water bath making them ready to go. When like this you can begin sinewing at a moments notice:

[Tim Baker]

PatM:

" ...wouldn't exceptionally stiff wood force sinew to stretch more?"

All else equal, stiffer wood = thinner limbs, so the sinew is resting closer to the neutral plane, so it's actually stretching less. One reason sinew works so well on Juniper is because, all else equal, bow limbs of it are thicker

[Springbuck]

  Tim, kind of like that.  As I said, I'm new to sinew, so this isn't "how I was doing it", but look at your bundles.  Just regarding the twisting technique mentioned.

If each of those "sub-bundles" in the larger, tied bundles were made up like that; about that size, damp, and just a little glue, then each given a single full twist to roll them together, they would hold themselves.  You could lay them aside and let them dry a bit, sort for size, etc.

   That's all.

[PatM]

 But does the lower bend resistance not counter that?

[Yellarwoodfellar]

It would seem that bend resistance would be equal in same draw weight limbs. Thicker wood raising the sinew farther above the center of the bow limb causing a longer stretch of the back and sinew. I hope I'm following Tim correctly anyway

[Tim Baker]

Springbuck:

That would be a quicker and easier way to make a cable, and allow less twisting, another plus. A couple of tries needed to get the variables right. Shouldn't take long.


PatM:

The lower bend resistance means thicker wood is needed for a given draw weight. Juniper's high elasticity allows this. It's likley the best wood/sinew combination of all.  Yew might be second.

Yellarwood:

That's right. The naturally elevated sinew on a Juniper limb is a smaller natural version of the elevated sinew test bow here.

[Springbuck]

Tim, not following.  Which would be an easier way to make a cable?

What I'm describing would be for backing, and is just a hypothesis.

  Each of your minor bundles looks like it was wet and just stroked parallel to smooth them together.   I was thinking that, alternatively, under primitive conditions, each small bundle could be twisted together, but not for coiling, counter-twisting, or making cable.  Just twisted up lightly for ease of handling, rather than tightly twisted for cable.    Almost parallel, nothing like cord.   When applied, loose enough to still be smoothed and blended.

[Springbuck]

Tim: "Thanks, even though I hate it that you thought of it first."

Just doing what Tiggers do best.   I have such a serious case of ADD, that I can't even think in the box when I try.   This kind of brainstorming is one of my favorite things to do.        Remind me to show you my list of things I need to patent, but lost interest in once I had a working prototype. 

Nice to be able to put it to use.

[willie]

It's also generally said that sinew works best with woods like Juniper but wouldn't exceptionally stiff wood force sinew to stretch more?

All else equal, stiffer wood = thinner limbs, so the sinew is resting closer to the neutral plane, so it's actually stretching less. One reason sinew  But does the lower bend resistance not counter that?works so well on Juniper is because, all else equal, bow limbs of it are thicker

But does the lower bend resistance not counter that?

The lower bend resistance means thicker wood is needed for a given draw weight. Juniper's high elasticity allows this.

The principles being cited on both sides of this discussion are correct. To know which ones are more correct, one would have to run the numbers for a specific combo. It is actually not that hard. if someone wants to sketch an specific example. (Please keep it rectangular) I can show the calc.

[willie]

  willie:  "Is "energy wasting" the same as  "not getting it's full potential?"

   I kind of think it is.  I, like you, don't think it is a good idea to stretch things right to the limit, but.......

   I'm pulling some numbers out of the air, here, but..... Say we want a sinew back for a 50 lb bow.  Since sinew can stretch almost 10% of its length, you can take "X" amount of sinew and pull it 8% of its length to get the 50 lbs.   OR, you can take "2X" amount of sinew and stretch it 4% of it's length.  Something like that.

Sinew is heavier than wood.

Two possibilities, say 2% and 4%, not near max.
I propose that the  2% has less unit hysteresis than the 4%, that is per sample of the materiel compared to an otherwise equal sample of the same materiel. When incorporated into a limb, it is a trade off. the more efficient 2% sinew is not as thick (less weight) for a double advantage, but in order to make a short limbed (and much lighter weight core/belly) bow bend enough to have a good powerstroke, the sinew needs to be proportionally thicker in the crossection. There is probably a different "sweet spot " percentage depending on the length of the bow.

[Tim Baker]

Bob Barnes:

" Tim, It would be really nice if you could accompany Steve to MoJam this year for the anniversary and flight shoot... " 

Thanks for that, and if the anniversary meet was set up like the original meet I'd love to be there. At the first meet full and precise bow stats were taken and bows accurately chronographed. Much of value was learned. The coming meet is a different animal altogether. Its rules could see an excellent design have a poor showing, a fair bow getting greater distance. More misinformation could come from this meet than information. Bowmakers value solid design information, and participants at the first meet very much enjoyed putting their bows through the process. Everyone benefited, primitive archery especially. Maybe next year. 


Springbuck:

Somehow I got the idea you were talking about cable making. 10 points off for me. 

[BowEd]

We'll test your bow anyway at Mo Jam.

[Marc St Louis]

Bob Barnes:

" Tim, It would be really nice if you could accompany Steve to MoJam this year for the anniversary and flight shoot... "

Thanks for that, and if the anniversary meet was set up like the original meet I'd love to be there. At the first meet full and precise bow stats were taken and bows accurately chronographed. Much of value was learned. The coming meet is a different animal altogether. Its rules could see an excellent design have a poor showing, a fair bow getting greater distance. More misinformation could come from this meet than information. Bowmakers value solid design information, and participants at the first meet very much enjoyed putting their bows through the process. Everyone benefited, primitive archery especially. Maybe next year.

Well that's pessimistic.  It's just as likely to be the opposite.  Regardless, it will be a learning experience whichever way it goes

[sleek]

Well, i think what has been learned over the years is being put into the rules for this shoot. We should come up with much more accurate results this time. I do want us to do the chrono shoot as well though.

[Badger]

Sleek, our spread sheet has a place for the fps readings as well. One can shoot both the chrono and the flight shoot or either one of the two. They are both optional.