Laminations

[adb]

 Draw weight is determined by the distance between the back and belly of a given design regardless of which core wood is used.
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I'm not following you.

[DarkSoul]

Over on TradGang, I think I read that only 18% of the weight of the bow is delivered by the (wooden) core of a f!b€rgl@$$ bow. The remaining 82% comes from the FG itself. I'm not sure where the figure of 18% is coming from, since it must depend on the wood species (stiffness) of the core wood as well. But if only about 18% is coming from the wood, no wonder that you can't notice a huge difference when using various wood species in a FG bow. So if you want to compare a low density wood such as soft maple (SG 0.5) to a high density wood such as ipé (SG 1.0), there will be very little variation. Maybe (just guessing here) 14% draw weight from the soft maple, or 22% from the ipé. The difference of only 8% is nearly negligible in draw weight: perhaps the ~4 pounds draw weight is sometimes even ascribed to a different variable by the FG bowyer...

Disclaimer: figures are just for illustration purposes, and are not calculated.

[Jesse]

You might be right. I haven't done the math. I would have thought that a woods resistance to bending would be more of a factor as core. It turns out it doesn't have a big effect. If you use ipe as a core or bamboo as a core the draw weight at a given thickness is the same. I tried heat treating cores before gluing. Again no difference.that leads me to believe that the gaines to be had " though small" are through the cores weight rather than its resistance to bending.  The real work is done by the back and belly.

[adb]

Are we talking FG bows, or wood bows here?

[Jesse]

Are we talking FG bows, or wood bows here?

both 

[adb]

Well, it's my understanding that the core wood on a FG bow is nothing more than a platform for the FG, which is doing all the work.
The core on a wood bow is an entirely different thing.

[Jesse]

Well, it's my understanding that the core wood on a FG bow is nothing more than a platform for the FG, which is doing all the work.
The core on a wood bow is an entirely different thing.

Different materials and limitations yes but the same physical forces acting on both.

[adb]

Well, it's my understanding that the core wood on a FG bow is nothing more than a platform for the FG, which is doing all the work.
The core on a wood bow is an entirely different thing.

Different materials and limitations yes but the same physical forces acting on both.

OK... but my only point (which you seem to be missing) is: the core wood of a FG bow doesn't matter much, but the core of a wood bow matters greatly.

[Jesse]

I get what you're saying believe me. I just don't agree with it.. If you make 2 tri lam wood bows from the same boards at the same exact thickness only changing the core wood like say an ipe belly, hickory, back and maple core on one. Then hickory back ipe belly and ipe core on the other. The draw weight will be close to the same giving the slight performance edge to the lighter bow which has the maple core. If im wrong im wrong and im fine with that but this has been my  experience

[Jesse]

It maters to both types of bows to the same degree. Example  A fg bow with an all fg core does not perform as well as one with a maple core.       Darn smartphone. sorry for the edits hard to see on this thing.

[adb]

It maters to both types of bows to the same degree. Example  A fg bow with an all fg core does not perform as well as one with a maple core.       Darn smartphone. sorry for the edits hard to see on this thing.

How do you know this? Have you done any comparative testing? The really high end recurve target bows (Olympic style) have 100% composite limbs. Don't you think, if your statement was true that all FG bows, including compounds, would have maple cores?

[Jesse]

They used to make all fg bows. I just happen to own one that was handed down to me. Believe me there is a good reason they dont make them anymore. If you can find an all fg longbow that people actually like I would be surprised.  When it comes to compounds the issue is the ability to withstand the forces. Quite a different ball game with cams/pulleys/ cables involved.

[adb]

I get what you're saying believe me. I just don't agree with it.. If you make 2 tri lam wood bows from the same boards at the same exact thickness only changing the core wood like say an ipe belly, hickory, back and maple core on one. Then hickory back ipe belly and ipe core on the other. The draw weight will be close to the same giving the slight performance edge to the lighter bow which has the maple core. If im wrong im wrong and im fine with that but this has been my  experience

I tiller most of my bows using the mass principle to some degree. So, 2 bows of the same design, having the same draw weight will have the same mass, regardless of what they're made from, including tri-lams.

[Jesse]

Nothing wrong with that. Mass is a good performance optimization  tool. We agree on that

[adb]

I don't try to over think it. Tri-lams look nice, too. I use compression strong wood for the core from experience, and tiller using the mass principle mostly. The mass of the limb should be the same regardless of it's make up (for wood bows!).

My theories about tri-lams revolve mostly around glue joints... much like plywood is stronger than a single piece of wood. Also the neutral plane of a glue joint is a factor I believe.