Primitive Archer
Main Discussion Area => Bows => Topic started by: Burnsie on March 19, 2025, 12:54:43 am
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Let's assume a 66" - 68" Osage stave intended to be a 45-50# longbow.
As you rough out your stave and then work towards floor tiller, what thickness do you work your limbs down to, to get you in the ballpark, before you start tillering in earnest. I've been using 7/16"? Or do you even have rule of thumb thicknesses in mind when you are working toward any particular weight bow?
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Hi Burnsie
If you want to learn floor tillering by feel, then my advice would be to find a heavier bow to get the feel on.
perhaps you might try bringing a stave to thickness with a long string (and spend some time floor tillering it as you go in order to get the "feel"
maybe even find a oak board to start with and try to tiller it to your weight at about brace height or slightly more. floor tilliering is an aquired skill and "seeing the bend" is part of it
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On Osage I bandsaw off excess thickness to about 5/8” then started using a belt sander to smooth out to a 1/2”. After that I switch to rasp, draw knife and card scraper. Only got burnt once and the bow finished out a 35#. All others came in well over 50# but I started dropping to 44-45# due to shoulder issue.
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Yuo didn't say how wide your bow is going to be.
I make my osage bows 1 1/4" or 1 3/8" wide. I use the same method on hickory bow blanks that are wider.
I make a 1/2" mark at the end of the fade and and drop the measurement 1/16" every 6" until I get to 1/4". I hold the 1/4" measurement to the tip of the bow. I start removing wood to my line but leave the belly rounded, I never go lower than a 1/2" thickness at the tip even though I have a 1/4" mark on the side. I drop the width to as low as 3/8" at the tip but the limb tip is 1/2" thick.
I tiller the rounded belly and reduce the oval shape to almost flat on my finished bow as I reduce poundage, the last 6" of the limb will remain somewhat rounded on the belly.
Others may make a wider, flatter limb bow profile, in which case the starting measurement will be less.
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If I have too much poundage after starting at 1/2" side thickness at the fades I drop my starting measurement to 7/16" but still stop dropping the side measurement at 1/4".
My belly at the fades looks like this after tillering and transitions to almost round close to the tips. The second picture shows my transition from an almost flat belly to rounded. I can use very tiny tips this way. The extra groove is a stringing groove, I can use a simple stringer made out of parachute cord to string my bows, very safe, the stringer won't slip off the tiny tip.
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Thanks guys - I'm right in that 1/2" - 7/16" range as well.
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What was said above.
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Because osage can be a little wavy on the back you can't normally use a ruler to mark the limb from mark to mark. I put the pencil in my right hand and my thumbnail on the back of the bow. This way my thumbnail will follow the contour of the back of the bow and mark accordingly. As I mark toward the tip, I rotate my hand slightly so my line converges with the next mark on the limb. It takes a little practice and a good eraser sometimes but you can make a neat line with practice.
The key to using these sidelines is never, never, never remove wood below them on the side of the bow limb and get lost in the process with uneven wood thickness on part of your bow limb. With this method you will seldom if ever have a bow limb that doglegs to the side because the limb thickness is so well matched.
Here is an example of what your line will look like if you have a little roller coaster in the limb.
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Here's how I do it. Call it a giz2
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This only works for pyramid bows that are uniform thickness from fade to tip.
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OOPS! I said I used my thumbnail as a guide, I went out to the shop to take a picture to illustrate what I was suggesting and found I that use the fingernail on my middle finger as a guide for my pencil.
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I Do like Eric but that little jig Jim showed is cool, may get or make me one of them. :) learn something or see something new every day. :)
Pappy
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I use a compass to do the same thing by putting the pointy end on the very edge of the back of the stave and using the other end to scribe a line on the side, it works well and you don't have to make a jig for it
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Better to gauge from the center of a crowned back.
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Yuo didn't say how wide your bow is going to be.
I make my osage bows 1 1/4" or 1 3/8" wide. I use the same method on hickory bow blanks that are wider.
I make a 1/2" mark at the end of the fade and and drop the measurement 1/16" every 6" until I get to 1/4". I hold the 1/4" measurement to the tip of the bow. I start removing wood to my line but leave the belly rounded, I never go lower than a 1/2" thickness at the tip even though I have a 1/4" mark on the side. I drop the width to as low as 3/8" at the tip but the limb tip is 1/2" thick.
I tiller the rounded belly and reduce the oval shape to almost flat on my finished bow as I reduce poundage, the last 6" of the limb will remain somewhat rounded on the belly.
Others may make a wider, flatter limb bow profile, in which case the starting measurement will be less.
Thanks Eric - this information helps a lot.
Below is the layout of my handle and fade section - I assume when you refer to the 1/2" measurement starting at the end of the fades, you are referring to the lines on the outside ends of my layout - both are 4' from the center line of the handle.
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Yep, just outside your outside layout line where you fade transitions in to the limb.
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I make a 1/2" mark at the end of the fade and and drop the measurement 1/16" every 6" until I get to 1/4". I hold the 1/4" measurement to the tip of the bow. I start removing wood to my line but leave the belly rounded, I never go lower than a 1/2" thickness at the tip even though I have a 1/4" mark on the side. I drop the width to as low as 3/8" at the tip but the limb tip is 1/2" thick.
Does the 1/2" thickness of the limb tips include any tip overlays you might add, or just the original bow wood?
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Yes, but just where the overlay sits, I cut my platform for the overlay at a slant back to belly so the overlay will blend with the limb and not be a big bump on the back of the tip. The limb up to the overlay will be 1/2" thick where the overlay starts.
I make my overlays 2 1/4" long so the blend with the limb gracefully.
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Excuse the crude sketch.
So I would be looking at a side profile something like this, transitioning from a 1/4" limb thickness back to 1/2" tips - correct"
My example shows a 68" bow - I assume with shorter bows the amount of limb having the 1/4" thickness is less and less? If the bow is short enough, can you end up not even having a portion of the limb at 1/4", or do you change your "formula" for tapering from fades to tips.
Sorry for all the questions - this has been quite helpful.
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Nope, you use the 1/4" side line but don't cut straight across the limb at 1/4", the limb thickness never drops below 1/2" anywhere on the limb, the belly is rounded at the tip not flat.
Like this;
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I went out to the shop and got the last bow I made about a year ago to show the limb profile on the bows I make starting just outside the fade. I don't know if anyone uses the same limb profile I use, I have used this design for 26 years with good success, ease of tillering and low set bows. I picked up this profile from the Dean Torgus book "Hunting the Osage Bow" his facet tillering didn't work for me so I altered my limb profile to suit my tillering process better. This is my osage bow profile, with hickory I have wider, flatter limbs with less arc until I get a foot from the tip and then make the transition to round tips.
(https://i.imgur.com/WdFDnsB.jpg)
Hopefully these will be in order; the belly profile at the fade, 7" out and mid-limb. The squared side profile lines stay the same, the arc is cut from the sidelines across the belly to the sideline the opposite side
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A foot from the tip, getting more rounded, 6" from the tip with more of an arc and the rounded belly at the tip.
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Thanks Eric - I think my little brain has all the pieces put together.
The top of the crown on the belly stays at a 1/2" thickness the entire length of the bow - round over sides down to your side profile line - got it.
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Osage will survive a lot of different designs. Even the ELB, for which is not ideal.
I always keep in mind that wood is generally 3 to 4 times as strong in tension as compression. That's why a crowned back is strong enough to balance the belly's compression strength.
Crowning the belly puts the most compression strain on the highest part of the crown. The lower parts of the belly crown don't start to resist compression until the high part has already yielded to some extent.
But, as I said, Osage can live with less than perfect conditions.
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Stiil no, the limb never goes below a thickness of 1/2", it may be thicker closer to the fade because of the arc on the belly.
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I have never complicated bow making with the mechanical aspects, I could care less, I make bows that shoot poundage plus 100fps with 10gr per pound. The third bow from the bottom is 52#@26", it shoots 170fps with a 500-gr arrow drawn to 26", that is my best. The rest shoot poundage plus 100 or perhaps 10fps more if I am lucky and I only have a draw length of 26" on a good day. My bows in other people's hands have won over a dozen national championships so I guess I have done something right.
Back in the day I was a pretty good shot and knew when a bow was acting right or needed a little more tillering work or limb balancing, a sense of feel kind of thing, worked for me.
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You can't build a bow by replicating my measurements exactly, too many variables, poundage, wood type, width, tillering and so forth.
One more post and I am gone.
The bow in the profile pictures thicknesses at the same points I posted belly pictures of.
Fade 5/8", 7 " out 11/16", mid limb 9/16", a foot from the tip 9/16", 6 inches for the tip 1/2" and the tip 1/2".
The limb width is 1 1/4" to mid-limb tapering to 1/2" nocks starting 1 foot from the fade. The bow poundage is 48#@25", 51#@26", flawless osage with a clean back, no knots or pins. The bow is 64" long with an asymmetrical 1" shorter lower limb because I like them that way for no particular reason except for the drawn profile makes the bow look like the limbs are equal length not lopsided.
It is not my latest bow like I thought, when i looked at the specs I found it was made 15 years ago.
Got it?
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With regards to limb width not thickness. Would it be a design flaw to start tapering 1.25" limb width immediately at the fade vs starting the taper at mid limb to tip? Visually creating a distal taper from fade to tip before tillering and reducing thickness.
Thanks to Eric for sharing such great detail.
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Certainly not. That's the design that is often called a pyramid bow. That's the only kind I make anymore. Easiest to tiller by far--one thickness, straight taper.
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Jim is a pyramid bow expert and knows his stuff.
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Certainly not. That's the design that is often called a pyramid bow. That's the only kind I make anymore. Easiest to tiller by far--one thickness, straight taper.
Jim, when you tiller a pyramid, do you monitor the thickness for consistency, ie take off wood for the full length of the limb?
or perhaps tiller to a bend profile and observe consistent thickness after the fact?
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With a stave, I start by band sawing off the bulk of the waste wood on the belly side, taking the thickness down to about an inch and a half.
Then I layout the width taper and handle width and saw close to those lines.
Then I mark the thickness at both sides (9/16" or a little less.) I band saw near one side line, tilting the wood to leave the center of the cross section thicker, to make sure I don't cut too thin on the bottom side of the cut. Then I turn the stave over and do the same along the other side line.
Then I attack the raised center of the belly until it is flat (using progressively finer rasps and scrapers as flatness approaches.)
The limbs are surprisingly close to tiller at that point. I work down the thickness of any stiff spots until things are bending evenly.
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Here's one from 20 years ago.
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bigger
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Didn't work. Trying a different one