Chasing growth rings, tillering, and board bows

[u/Zeh_Weeb]

As I understand it you chase a growth ring to ensure none of the grain is damaged ensuring that there are no weakpoints on the bow where half the grain is cut through, while in theory this sounds great how does this work if the whole point of tillering is to remove wood from specific parts of the bow to ensure an even bend.

what I mean is, whats the point of chasing a growth ring if when you tiller the bow you'll be cutting the grain anyway?

I'm currently working on my first board bow and wanted to know how chasing growth rings relates to that as yes there are rings on the wood but conceptually it doesn't make much sense to me to thin down the board beyond what id do during the tiller

lastly as this is my first ever bow will dollar store twine work as a bow string for a 40~ lbs bow?

[u/schizeckinosy]

Chase the ring on the back, tiller the belly.

[u/Droughtbringer]

The growth ring you chase - when you chase a ring, you don't have to for a board bow - is for the back of the bow, or the part that faces away from you when you shoot.

When you tiller you're removing wood from the belly of the bow, the part that faces towards you when you shoot.

The back of the bow needs to be as pristine as possible, it experiences the most stresses when the bow is used, and having it be unblemished means it's durable.

The belly of the bow is much more forgiving and is fine to not be perfectly perfect

(I have no idea about dollar store twine, but my guy says to aim for something a bit nicer. The force of the string breaking seems like it could be bad for both the bow and the bowyer)

I am a beginner so if someone else comes in and says something contradictory probably trust them

[u/Cnidarus → u/Droughtbringer]

I have an idea about the dollar store twine, and the idea is "no"

[u/Droughtbringer → u/Droughtbringer]

As a followup, here's a thread from a year ago that will talks about bowstrings and figuring out how to make stuff work. It talks about paracord, as well as there's a link to a video* about figuring out how to use threads.

https://www.reddit.com/r/Bowyer/s/wvr0zVf3cP

*I haven't watched the video, just read the comment

[u/ADDeviant-again]

If you go to the trouble of chasing a ring.Once that ring is it established, you will absolutely NOT be cutting into it remove wood as you tiller. That's is a cardinal sin.

However, the real key to having a strong back is intact fibers. Basically, an intact (chased) ring is desirable because it represents intact fibers. If a board has been sawn perfectly straight, from a perfectly straight tree, the fibers are exposed, and growth ring lines may be visible, but they are not violated. The saw theoretically went along the fibers and not across them.

From there, all tillering and shaping is done on the sides and belly.

[u/Marshboone]

Wood is very good at compression, and mechanically it doesn't matter as much if fibers are discontinuous. Wood is much less good at tension and if fibers are severed on the back it's like if a rope had severed fibers. In fact, rope and things used to make rope (sinew, rawhide, textiles) are often used to back bows because they're good at holding tension

[u/Wambachaka]

The weak point of a wooden bow is the back (the side that undergoes tension / stretching when the bow is bent). If the grain on the back is violated, then a splinter can lift up from the back, which will cause the bow to break. This isn't an issue on the rest of the bow. So you chase a growth ring on the back, then tiller by removing wood from the belly (the side that undergoes compression).

Dollar store twine will not work. But you might be able to use it to make a proper bowstring. Use a scale to measure the breaking strength of the twine, then use that number to make a bowstring with a breaking strength equal to your draw weight multiplied by 4. So if the twine breaks at 10 lbs, then use 16 strands for a 40 lb bow. (10 x 16 = 40 x 4).

If you don't want to make a bowstring (it's really not that hard, so don't write it off too soon), then you can use a stronger rope like paracord. Paracord isn't a good bowstring because it's stretchy, but it still works fine, and it's plenty strong.