Torsional centerline of limb vs actual

[Appalachian Hillbilly]

How do you guys find centerline of you bow limbs? Was watching the South Cox video of him doing 3 piece takedowns and he leaves his limbs full width, then using a jig that clips on the end of each limb that holds the string. He then marks the string line on the limbs at brace height and adusts side to side with the limb tip stringholder adapter to get the string centered.

Then once he has a centerline,  he had a clear template he overlays on the limb to mark his profile. Does any fine adjustments with the nocks grooves.

I had laid out my profile and center lines on my masking tape, but my glass moved a little in the mold.

His method looks very effective .
How do you guys do takedown limbs?

[kennym]

I do it that way too , glass don’t always stay exactly where it starts...

[JGR1269]

Same here as well.

[Crooked Stic]

Never mark mine untill the limbs are milled to width. 1.625 curves and 1.375 longbows. Most times after that the center is where you mark it. And if your lam grind is good on curves and all drilling done right fine adjustment can be done with string grooves leaving them a bit wide and to final width when pulling straight.
Never really had trouble with LB as long as long as center goes thru the center of the riser checked with a weighted string.

[Kirkll]

First of all i gave up using masking tape on my glass after my first year of bow building. (about 15 years ago)  If you just take the time to clean off the EA 40 with lacquer thinner before wrapping it in plastic before going in the form, you don't need to bake on your masking tape in a hot box or using heat strips. That stuff is nasty to get off the limbs.

I do use small pieces of tape on the limb butts after i get my limbs ready to mount for drilling and milling purposes, as well as the tip and center line lay out.

For getting a center line on your limbs, a string line is hard to beat. just use a spring clip on each end and eyeball it. typically tells the tale.   I use a 6' level for a straight edge and measure from center of limb bolts to get my measurement and transfer it to the limb tips on each end.   

Then i paint the limb profile on the limb using a pattern.... Here are some photos to look at to give you an idea what i'm talking about.     Kirk

https://photos.app.goo.gl/RNMOwINK2s37vfoN2

https://photos.app.goo.gl/eObZ7ZFhLGYqxdc93

https://goo.gl/photos/Hxd6XeTJphNEUxtq8

[Crooked Stic]

Well they just let anyone back in here huh.

[Buemaker]

Good to see you again Kirk.

[Appalachian Hillbilly]

Kirk thanks for posting those pic links! That is some beautiful work!

[Kirkll]

Thanks guys…. I miss swapping philosophy with other bowyers and helping new guys get off on the right track.

Getting back on topic here…. A lot of new guys building take down bows get frustrated with limbs going sideways and this discussion always comes up.

then  the suggestions of tiller blocks come up to find true center, and which side of the limb you sand to eliminate a twist which adds to the frustration because it’s not really a productive exercise. Why it’s twisting should be addressed. Not how to fix it….


These glass limbs are amazingly similar coming out of the same form using identical laminations, and true center on a limb profile is typically very close to torsional center. Close enough to typically adjust the depth of your tip notches to get things bending straight. 

The key to success is getting the limbs mounted as straight as possible on your riser before you mark your center line, and not have any twist in the limbs from the start. Checking your limb pads carefully for being dead square with 90 degree angles on the same plane is critical. Another huge part of this is checking both limbs laying on edge on a flat surface at the limb butt location and clear through the working portion of the limb BEFORE you mount the limbs. This is true for both long bow and RC limbs.

Getting your limbs mounted with a slight twist on your riser block is very easy to do, and is the most common reason guys are fighting limb twist.     Kirk

[Appalachian Hillbilly]

Thanks so much for that advice! That bow in the middle of your first post, I live that profile. Almost a semi recurve. I would live to build one like that!

[Kirkll]

That limb design has proven to be one of my most popular models I call my Sasquatch hybrid long bow.

Originally it started out to be a recurve limb test and I laid up a set that came in around 80#. Rather than use them for tomato stakes, I narrowed them way up to a long bow width profile just for fun to get the weight down to about 60#….

 What happened next was I got a serious jump in performance that couldn’t be ignored. So I took it from there and started adjusting taper rates and wedge lengths until I maxed out in the high 190’s on some of these. Besides speed, this design proved to be incredible in long draw length applications. I can build a 60” bow that draws smooth to 33” with no finger pinch and less than 3 PPI on the tail end of a 55-60# draw weight with this design….. That my friend is tough to do…. 

 Kirk

http://bigfootbows.com/b/bows/

[Appalachian Hillbilly]

Those are gorgeous designs! Very impressive.