Truck Pull

[Stumper]

Talk to a self bowyer. The sapwood is stonger in tension in many species-that tends to equate to more flexible. On the other hand thin is the key to bending without breaking. -The way to make weaker, less resilient, more brittle wood work in a bow is to make it THIN and wide. Some woods can be narrow in width and thick in cross section and function well for archery (Osage, Yew, Lemonwood (Degame) and to a lesser degree Hickory. Almost any wood will make a functional bow if it is made thin enough and strength(drawweight) 'added' by making those thin( in cross section) limbs wider. Centerpunching is very useful in preventing fiber pull in some species when harvesting for milling. It is OKAY to do in many situations. However, when the way that wood breaks is analyzed (back to our private neutral plane discussion) the reality is that centerpunching actually makes hinges that break sooner in the felling process. It feels good to have some wide straps on the outside-we feel intuitively that it is less likely to tear the hinge and roll out , causing a loss of control. In reality what happens is that the thicker hinges are simply more bend resistant so we have to apply more pressure to iniate movement-once it starts though... the thick hinges break loose and relinquish their controlling influence EARLIER in the tree's fall. Leaving the heartwood and making the hinge thinner is actually the better course but it doesn't seem that way on the gut level.:angel:

 

[TheTreeSpyder]

That is some of what Stumper let me into about flexing wood in his PM i spoke of.

In an ol'Erin Sorenson film, Mr. Sorensen describes the center punching being Swedish devised to save wood from fracturing up the center of the most expensive lumber end on felling, saying that it fractured earlier, and could splinter up inside wastefully. Then went on with how he thought that it made for softer fall becase of this.

i'd kinda go with some species variation here. i find more 'dramatic' (tree sometimes holding on all the way to ground) with local pines. Limited with oak, maybe every thing happening so fast, that especially in oaks it is as Stumper says, just too quick to catch/evaluate; and doing so much of all else to help etc...

In cases of darkeend, dry, part rotted center; i tend to punch it out (except if fighting side lean); to kinda know what i got, and that it is at maximum flexability. Pines seem to favor it too here. But besides fiber type stand differently (higher, more centered C.o.B. and less trunk width to control charachteristically).

Many things to consider. Hinge thickness is certainly good point. But, as less fibers are needed in the more leveraged loading of now rear fibers (rearranged from center punch), and only punch out 1 - 1 1/2 bar widths, how much thicker is hinge really? (Okay i'm no dummy depends on original lenght of hinge). But with the short cut out, and perhaps less than 1/2 the fibers repositioned (depending on how fat hinge is, as to how much leveraged now back row fiber is, the more leveraged the position, the less fibers needed?). Also, there would seem to be more fiber leveraging in the stiffer fiber (unpunched)center...........

Lots of things to consider.............!

:angry2: Plenty to start trouble :Eye: 'round hear! :Monkey:

 

[Kneejerk Bombas]

Some good subjects covered here. Glad to have you fine people to argue with.

 

[murphy4trees]

the thick hinges break loose and relinquish their controlling influence EARLIER in the tree's fall. Leaving the heartwood and making the hinge thinner is actually the better course but it doesn't seem that way on the gut level.

Hi Stumper,
Are you absolutley sure of this and where did you learn that??

You sound like you know what you are talking about... Who is going to understand the charactersitrics of wood fiber better than a bow maker?

That said there seems to be plenty of big egos giving bad info around here... At least enough to give me pause...

I would really like to see some experimentation to verify this sort of thing.

That "doesn't seem that way to your gut" is what I call counter-intuitive... I've seen it time and time again in this work, so that gets me thinking you got it right...

Big Jon was just telling me how important it is to not leave a back-leaners hinge too thick.... Sounds in line with your point as the hinge has to move quite a bit and maintain full control before freefall, thus requiring a lot of flexibility...

 

[Oxman]

Don't make that hinge too thin.

 

[Kneejerk Bombas]

What does the hinge thickness have to do with the butt comming back?

 

[TheTreeSpyder]

Hey Mike, not you Mike, i get to mess with you all the time!

Y'all should check out Oxman's site and article collection he wrote for industry rags.

i think a strong enough hinge to resist butt coming back is needed as part of preparing for the equal and opposite reaction of felling. Though i have never trimmed one down to that point, and Oxman might be making stronger referance to tree size i don't see.

With Stumper's strategy i haven't had any problem. i don't think he meant to whittle hinge to nothing, but rather instead of having a short across face hinge that is fatter, he feels the mechanical properties of the wood have the strength but bend easier arrainged in a longer thinner pattern, but not paper thin. That might hold more true, for more brittle woods that you have a flexxing/hinging problem with anyway. The idea of the back cut is to reduce the hinge's leverage against pull to target; while maintaining leverage against sidepulls. If there is no shelf or ramp on the bottom face, even extra caution should be taken not to weaken hinge so much to target, that it was also too weak to pushes back from target axis.

Or something like that!
:alien:

 

[wiley_p]

After removing all the brush, and removing most of a stick, on any speicies if there is diameter at the butt, and say 20'-30' in the air, then I always bore the center holding wood out. Its quite simple really, has nothing to do with heartwood, elasticity, or any of that crap. less wood to break means the now balanced stick will wedge over easier, and for those who refuse to employ wedges, the ropw pull iss easier, and the corners are still intact, guiding stem to the face.

 

[TheTreeSpyder]

i think per forward pull efforts of lean + wedge + line (pulls/pushes to target not to sidelean or to counter sidelean axis of hinge); that in the equal and opposite reaction just as much resistance to forward fold will be encountered at first folding.

If it is easier or harder from there would take more examination i believe; for the named forward to target forces must collectively equal one single unique number, and their must be a matching to that unique quanity, or falling scarcely below at first folding.

With sidelean, and a tapered hinge against the sidelean; the same resistance in the hinge is met at first/matched folding; but the arraingement of the fiber that mke up the total resistance are arrainged more favorably to controlling the sidelean i think.

A hinge as a carabiner of similar shape is going to have a strong axis (the long one in hinge to fight sidelean axis) and a weak axis (the thinnner one, in hinge to allow spar to fall to target). i think the lean must be calculated to how it addresses each of the support axises of the hinge. That is more real, for it gives 2 dimensions to the equation; the 3rd dimension is the height of the Center of Gravity in the lean itself. Those are how the 3 dimensions of the load address the hinge i think.

Or something like that,
:alien:

 

[Stumper]

Daniel, Fair questions. Let me start by saying that different woods have differing properties and special situations require special techniques so my statements aren't to be taken as absolutes in every regard. About the wider and thinner being "better" (better meaning maintaining hinge integrity further into the fall). Some of this I learned through practical experiments. Some I learned from reading technical manuals and tests regarding bending wood when my dad got into bowmaking. Here's the skinny. Firstly-we know that wood is not a homogenous material- two pieces of the same species or even from the same tree will not behave precisely the same. Therefore, I'm going to speak about averages. I'll give you some examples that you can test to see if they seem to be accurate.
Grab a clear eight foot pine 2x4. You can bend it a little by hand. Now grab a clear pine 1x4 the same length-you can bend that a LOT more. Which is stronger? The 2x4. Which will bend the furthest before breaking? Assuming no defects and similar grain orientation in the boards-the 1x4. Why? Because fibers (in this case wood fibers) can only withstand a certain amount of elongation before rupture. In any piece of bending wood we have fibers being stretched over the outside of the bend and fibers on the inside of the bend are being compressed (at some point in the middle there is a neutral plane where the transition from tension to compression occurs). The thicker the wood the further the outer fibers are from the neutral plane and the greater resistance they will provide to bending-just a little bend takes the "slack" out (there isn't any slack of course but the loading increases the tension on the outerfibers very rapidly) The way the ratios work is thusly: Doubling the width of a piece of wood will double it's strength. Doubling the THICKNESS provides 8 times the strength,. Test your 1x4 against a 1x8 and against the 2x4. In this scenario "strength" equates to resistance to bending or ability to support a load. What happens when the bending starts though---A 4X4 is very strong but it won't bend far before it cracks and shatters-once the outer fibers let go a cascade effect usually occurs-the 2x4 will bend a little way before it ruptures, the 1x4 further still, a piece of veneer will let you roll it up full circle-but it isn't very "strong".
Wiley is absolutely correct that boring out the center of his hinge makes it easier to get moving-provided that the hinge thickness remains the same. The issue is how we want the hinge to behave.-If we want x number of pounds of resistence to bending in the hinge then we can bore out the center and leave the hinge slightly thicker(remember the 8x1 factor-if we bore 16" out the center ofa 32" wide hinge that was going to fold at 2inches thick then the straps left on the sides only get to be 2.25" thick to provide the same initial resistance. On the other hand Wiley could narrow his hinge by about 1/8 instead of boring out the center and make it just as easy to iniate movement. Once movement begins the thinner hinge will resist tearoff further into the fall. If you want to hang a spar at an angle on a narrow face cut without tearing off ...the way to do it is with a thin hinge-not a thick one-the thick hinge starts breaking almost as soon as the spar starts moving. a Thin but Wide hinge will frequently just hold the spar on the stump until you cut some more fibers!

Enough holding wood should be left for control but, given that, the thinner and wider across the face a hinge is the better it resists rupture and premature tear off. I don't advocate cutting hinges down to paper thinness. I do advocate cutting a hinge to 1.5 -2"thick rather than leaving then 2.5 inches thick and boring out the center-unless fiber pull on a sawlog is a factor.:angel:

Clear as mud?

 

[Tim Gardner]

Stumper, very good post. Well worth the read. Thanks.

 

[Stumper]

Thanks Tim.

 

[Kneejerk Bombas]

Well written Stumpy. Every now and then you post something completely reasonable. On these occassions when you behave totally out of your normal character I agree with you and am overcome with awe at your great intellect and perspicuity.

 

[MasterBlaster]

Originally posted by Mike Maas
...great intellect and perspicuity.

What's that last word?

 

[Kneejerk Bombas]

Hell if I know, ask Stumper.

 

[Tim Gardner]

Originally posted by MasterBlaster
What's that last word?

It a fancy $2 word that says you can understand what he writes.

 

[Stumper]

Perspicuity=clearness of expression. Fun word since it tends to inhibit what it is purported to express.

 

[Stumper]

Tim beat me to it but forgot modern priceing . It is now a $5 word. Please send cash to...........

 

[TheTreeSpyder]

Stumper , that was better than the first time you presented here or in messages! A wide depth of knowledge crossing the commonalities of what we deal with further then the borders of what we can experience! And i am still digesting and weaving these things deeper into what i set up; and especially the neutral plane of fibre that you pointed out must exist between compressed and tensioned wood, as i immediately went to there for the next property to exploit in hinge (why not? )....

i think the tapered hinge keeps a general 'low profile' and only places the extra fibre where needed. in brittle, but solid wood, where ya can't depend on the pull force as much, for it comes from the hinge's flexability, i adjsut the other side more (in solid wood) and play with the way the faces slap for help too. Making almost a safety, the faster the tree 'flys' and is trying to get away from me (hinge strategy not working slow and nice), the harder the faces slap, so the more adjustment there etc. Covering and self adjusting to the failure or the succes of the hinge pull, the frace push steps in. i've been playing with a lil 'punching' of hinge though, not so much extra move to face to hit center of hinge, but a diagonal punch from back to front on thin side of hinge, to leave just a 'clump' of hinge for pivot, and force more fibers to fat side of hinge. Then finish backcut from fat side of hinge, bring so close, then cut across some instead of straight to target, to (i think) get the rest of the hinge thinner; and i think there is better control power if the release is more across hinge (sidelean conditions) like throwing the release force directly against sidelean rather than release force throwing towards target as hinge folds. Direction is always important, even here i think, the direction of the 'release force' and the way it steers.

Or something like that..
:alien:

 

[rumination]

Thanks Stumper. You opened my mind up a little more as to the nature of wood. I think I just learned something important. I love it when that happens!