New guy with stupid question

[snowplow]

Now that I have set the bar nice and low, hi guys!

So I have a very elementary question. I just cant make sense of this in my mind. Maybe you can help me out.


So say you have a dried stave. If you tied a string to it and pulled it to 28" it would pull very heavy and then break in half.

Then on the other end of the spectrum, that same piece when done right would pull easily to 28" at your desired weight.


So as you remove belly material, the bow gets lighter and more 'bendy'. Say you remove more and more until you can finally pull it to 28". Its now at 45#. How would you have made that bow 55# without it breaking? Do you see what I mean?

Lets say we had an 80# bow. How does that stiff thing not break when pulled?

Sorry I hope you follow me, I am having a hard time putting to words what is tripping me up. 


Thanks for the help!

[osage outlaw]

Say your desired draw weight is 50 lbs at 28".  You work the stave down until it is starting to bend.  Start with a long tillering string and use a scale to check your draw weight.  Bend it until you hit 50 lbs.  Lets say that's 10" of draw.  Make sure everything is bending evenly and remove some more wood.  Check it again on the scale.  This time it might take 11" of draw to hit 50 lbs.  Keep the limbs bending evenly and slowly scrape away at the belly.  Eventually you will get the limbs bending enough to take it to a low brace height.  Keep checking the weight and draw length.  If your goal is 50 lbs, don't pull it any farther than that.  Keep removing wood and you will get it to full brace height.  Check the weight again.  Lets say its 50 lbs at 20".  Fine tune the limbs to make sure they are bending smoothly and evenly.  Keep removing wood and checking the weight.  Every time you remove wood from the belly it will take a little farther draw length to hit 50 lbs.  Go slow and steady until you hit your goal of 50 lbs at 28".  Hope that makes sense.

[J05H]

It all boils down to design. If your stave is long enough and wide enough for its species to make the draw length and weight your shooting for, then if you tiller it well it should make it. You decide on your draw length and weight up front, then you only draw your bow to that weight. Say your going for 50@28. So you only ever pull to 50 pounds even if its 50@3. First you focus on getting it bending evenly. Never pull it farther than it takes to see a flaw. Once you get it bending well, then you reduce wood slowly and evenly and check your draw length at 50lbs often. You also check to make sure it stays bending evenly. Its just a matter of scrape a little and check, scrape a little and check, and so on until you reach your final draw length.

So the way to avoid a 45# bow when trying for 55# is to always check your draw length at 55# unless you see a flaw. Sometimes, by the time you fix the flaw, you're already underweight. It happens to us all. Just try again.

And the reason that an 80# bow doesn't break is that it was designed to be 80# from the start. It has enough wood in the right places to bend evenly and safely out to full draw at 80#.


Edit: You posted while I was still typing, Outlaw.

[Badger]

  Snow plow, a 20# bow should be under the exact same strain as a 120# bow. In other words there is only one correct thickness for a specific bending radius and the actual draw weight is accomplished by using the proper width. You can monitor the condition of the wood as you work it down to see if you are over straining it. You only advance the pull in no more than 1" increments, always check to see if it has picked up any set inbetween advances in draw length. Adjust the bending areas to bending properly as soon as you can see them and never advance the bend with an area needing adjustment. If a bow starts taking on set too early in the tillering process you may need to lower your target goal for draw weight and make the next one wider. We pretty much have standard widths we use for various woods that will help you get started with the right demensions.

[TimothyR]

Say your desired draw weight is 50 lbs at 28".  You work the stave down until it is starting to bend.  Start with a long tillering string and use a scale to check your draw weight.  Bend it until you hit 50 lbs.  Lets say that's 10" of draw.  Make sure everything is bending evenly and remove some more wood.  Check it again on the scale.  This time it might take 11" of draw to hit 50 lbs.  Keep the limbs bending evenly and slowly scrape away at the belly.  Eventually you will get the limbs bending enough to take it to a low brace height.  Keep checking the weight and draw length.  If your goal is 50 lbs, don't pull it any farther than that.  Keep removing wood and you will get it to full brace height.  Check the weight again.  Lets say its 50 lbs at 20".  Fine tune the limbs to make sure they are bending smoothly and evenly.  Keep removing wood and checking the weight.  Every time you remove wood from the belly it will take a little farther draw length to hit 50 lbs.  Go slow and steady until you hit your goal of 50 lbs at 28".  Hope that makes sense.

This is an excellent way to explain the proses. Thank you outlaw!

[sleek]

Long sticks bend further without breaking that short ones of the same width. Short ones are harder to bend than long ones.
Fat sticks are harder to bend than skinny ones of the same length.

The above statement is a very simple explination of tje two factors you control to get weight you want at draw length you want.

Another example. Shower faucet. I want a certain water pressure and temp. I have two knobs to play with. The more I turn both the more pressure I get. But one must be more than the other to get my temp. You mess with both until you have what you want.

[bowandarrow473]

It's all about design and distributing the stress evenly. I've heard of 200 pound bows that shoot without breaking(don't know how you could even draw them though).

[Mad Max]

nuff said

start scraping

[snowplow]

Thanks guys, those were super clear. That make total sense to me. Thank you!!

[Eric Krewson]

Another thing; You don't start out with a strung bow, you use what we call a long string first that is longer then the bow. First you floor tiller, next use the long string and finally when you have  the limbs bending with a very even bend on the long string you can actually string your bow. It is best to use a slightly longer string when you first string your bow and start with a low brace height, around 3". This way if you encounter a hinge or one limb much stronger than the other you can quickly unstring the bow and correct the problem with out stressing the bow limbs too much.

Look up "Tillering Gizmo" in the how to section, you will need one.