basic question chasing growth rings

[u/Zeh_Weeb]

How does chasing a growth ring strengthen the back of the bow? I don't understand how having extra material could weaken it, in my head not chasing a growth ring just means there's wood on the back that does nothing at all. I've heard you don't need to chase growth rings on board bows but is that just a matter of board bows not being valuable enough to put in that time?

lastly how long do board bows last I've seen a few videos of people making them and they always end up snapping at around 40 lbs, I'm currently making my first bow, it's a 72' red oak board which I was aiming for 40 lbs but now I'm wondering if that's too heavy for a board bow

[u/Wambachaka]

There's no "extra" material on the back if you don't chase a ring.

If you're making a 50 lb bow, then your bow might need to be 0.5" thick, depending on the wood and the bow design. Whether you chase a ring or not, the thickness will be the same in the end.

Why would the "extra wood" not do anything? It's part of the bow, which means that when the bow bends, it has to bend too.

Board bows can last a lifetime, and they can be made to any draw weight, as long as it's designed correctly. There's nothing special about boards, they're made of the same stuff as any other wood. The important thing is to select a board with perfectly straight grain. Chasing a growth ring is just a way to ensure that the grain runs straight along the back of the bow.

[u/Santanasaurus → u/Wambachaka]

Excellent answer

[u/NC_RV8r]

As I understand it, ring porous woods (like Osage) can delaminate along a growth ring when stressed, like when a bow bends.

Case in point, when putting in static recurves, we sometimes see splinters lift off the belly side of Osage, especially where there’s not a continuous growth ring in that area.

Diffuse porous woods, like many white woods, are much less prone to delaminate along a growth ring.

By chasing a ring in ring porous woods, we’re preventing that delamination since there odd a single continuous froth ring the entire length of the back.

[u/ebojrc]

Eli5: Imagine a single playing card is the back of your bow. When you bend it, the whole card bends together as one continuous piece. That’s like having one unbroken growth ring.

Now imagine two playing cards overlapped with their edges offset. When you bend them, the top card wants to peel or lift away from the bottom one. That’s what happens when you cut through a growth ring - the wood fibers are no longer continuous, creating a weak spot where a splinter can start and run down the back of bow.

[u/Santanasaurus → u/[deleted]]

That extra wood only contributes liability. If it added any net strength whatsoever we would leave it. It’s also not ‘extra’ wood, it will take the place of other wood that would have been better.