Tapered vs Parallel Thickness Limbs

[Erwincm]

A friend of mine shoots a Samick Sage and I noticed his limbs are constant thickness with no taper. His Samick seems to shoot pretty well. The constant thickness limbs have the obvious advantage of ease of producibility. Dumb question - what is the advantage of tapered thickness limbs over constant thickness limbs?

Charles
Madison, AL

[Pat B]

A bow bends in relation to the limb taper. It can be the width taper, the thickness taper or a combo of both.

[monterey]

It's a matter of design and the relationship of the width and thickness.  The relationship of the two in the Sage may allow/require no thickness taper.

OTOH, a careful examination with caliper or micrometer may show that there is some taper.

[Crooked Stic]

Both ways work. The tapered limb will bend more towards the tip and may stack sooner.

[bornofmud]

Depends on the limb shape and how you want it to bend.  there is no advantage to one or the other, other than it making your particular bow shape function better.  Most bows have some amount of thickness taper, I'd be surprised if the sage was actually parallel.

[Erwincm]

I'll have to mic the Sage to be sure. Seems like a constant thickness limb would be so much easier to produce and more economical that everyone would do it (assuming all else is equal). There must be more to it in terms of some advantages in the tapered thickness limb design.

[bornofmud]

The advantage is that you can get r/d shapes to bend right.  Parallel limbs only usually are found on hill style or very mild bow shapes, where the limb profile taper is enough to weaken the tips for that design.  r/d bows usually have higher performance than hill styles, and thus we taper the limbs to get them to bend right.

[monterey]

About the only bow that tolerates a non taper thickness is a pure pyramid.  Even that might benefit from a very mild power lam.

[bamboo]

IMO parallel limbs tend to be hingy in the butts--and carry a lot of physical weight in the tips
it will work but tends to not be very efficient

[ztontonz]

I dont fully agree with what has been said here.
Of course the result of parallel limbs vs tapered will be more weight at the tips, more vibration and relative speed loss in the end. But this doesn't mean your bow will be slow nor unefficient.

If you take the exemple of the wolverine bow made by Abe Pener, It has parrallel limbs, a quite radical r/d profil and still is an efficient bow (80% efficiency and 180fps when shot at 28" with 10gpp arrow).

Design of limbs includes profil, thickness taper and width taper. I dont think each parameter should be consider by itself.

To come back to the initial question, for me avantages of parrallel limbs  are:
- laminations are easier to produce and to center on your bow form when gluing
- your limbs will bend closer to the handel
- more thickness at the tips will give you more lateral stability

Your choice will depend on what you are looking for when building a bow.

[ztontonz]

I dont fully agree with what has been said here.
Of course the result of parallel limbs vs tapered will be more weight at the tips, more vibration and relative speed loss in the end. But this doesn't mean your bow will be slow nor unefficient.

If you take the exemple of the wolverine bow made by Abe Pener, It has parrallel limbs, a quite radical r/d profil and still is an efficient bow (80% efficiency and 180fps when shot at 28" with 10gpp arrow).

Design of limbs includes profil, thickness taper and width taper. I dont think each parameter should be consider by itself.

To come back to the initial question, for me avantages of parrallel limbs  are:
- laminations are easier to produce and to center on your bow form when gluing
- your limbs will bend closer to the handel
- more thickness at the tips will give you more lateral stability

Your choice will depend on what you are looking for when building a bow.

[bamboo]

zt
here is the actual question that was posed---

" Dumb question - what is the advantage of tapered thickness limbs over constant thickness limbs?"

even your statement contains the answer---"Of course the result of parallel limbs vs tapered will be more weight at the tips, more vibration and relative speed loss in the end."

and that's not to say your example is not an excellent exception to my statement [and yours]

have you measured the wolverine?  does abe use a power-lam/tip wedges?--it seems like a fairly fast bow for it to be "only" edge tapered [no thickness taper at all]
---and please don't take my statements as argumentative--I truly enjoy discussing design

[Bowjunkie]

I almost always want them to bend so that each inch works as much as the next. I like narrow bows, which allow little width taper, so I need them to taper in thickness.

[ztontonz]

Thanks Mike,

I really enjoy discussing design too and I think this is a really interesting topic.

You are right I did not exactly answer the question that was asked in the first place. I wanted to bring another point of view in this thread I think.

To answer your question here are the picture from the tip ans handle on the wolverine, no power lam and no wedge:


 

I am sure some bowyers on this bench already made tests on bow with // and tapered limb with the same profile. It would be interesting to have their feedback.

[Erwincm]

Great point about how thickness taper facilitates a narrower limb. I like narrow limbs as well. Even if you could coax an even bend across the full limb length of a constant thickness limb, it would need to be fairly wide to allow sufficient width taper. I think I understand the function of limb thickness taper now. Thanks guys!

[bamboo]

i'll tell you--this stuff really gets my gears turning!!LOL!
I've been tweeking a hybrid design --
1-1/2"wide @64"long-and using a.001" taper and a .002" taper power lam about 8" outside of the fades/6"x.020"tip wedges--a lot of set back
and its really shooting well
...but one change that never occurred to me was to try parallel lams--I'm sure I could start the side taper a little sooner--and make the tips  narrower--the bow had a whip tipped shot feel to me--my buddies love the bow and it is quick--but I felt I could do better--and this might be it!!
back to the drawing board!!thanks for pointing the bow design out zt!!