balanced bows with different limb length's

[Glenn Newell]

OK i have been howled down for this before and in Australia one person was so upset he wrote a derogerty 27 page critique about me on the internet. But anyway here goes. When you tiller and equal length bow the way you did and you placed your arrow shelf 1.25" above centre which is the way most of us do it the string length from where you nock the arrow is 2.5" shorter to the top limb than the bottom limb. Imagine how much extra pressure you are placing on that top limb when it is being drawn. It shows up in selfbows as extra string follow and uneven set and hand shock. Making an equal length bow with positive tiller and set up to be shot the way you have it will pull the bow out of tiller almost straight away. Strenghten that top limb or negative tiller the bow and it will take even set and will reduce handshock, it's amazing the difference it makes...Glenn...

[osprey1]

Thanks Glenn. Seems reasonable enough. The actual act of tillering the bow that is looking at the limbs and seeing if they are bending  equally ....that would still seem to be easier on a symetrical type of bow?

[Glenn Newell]

Tom, making a bow with a shorter lower limb is not new, it has been around for a long time, they were made that way because they ae better balnaced when being drawn. I have an old Andaman Is. selfbow here that has a shorter lower limb.
Best thing to do is make several bows and find what works best for you and the way you shoot a bow, but I would be looking at all options...Glenn...

[Pat B]

Glenn, we are fortunate to be members of this website that demands respect and tolerates nothing less. Everyone's opinion is welcomed..not always agreed upon but always respected.
 Now if you guys will step aside, I'll tell you how it should be done! d;^)    Pat

[Glenn Newell]

No worries Pat, I know what you are saying. I use to have this idea in my head from what I had read that no bow should ever have a stronger top limb but it was on my second trip to the USA in 2000 I was shown by a bowyer over there that that is not necessarly true and he showed me why. I had been making selfbows since 1993 and they were mostly equal length limbed bows with the arrow shot above centre and positive tillered. While my bows shot well they didn't shoot anywhere near as well as the negative tillered bows I since then, but these days I much prefer a bow to have a shorter bottom limb. But as has been stated on here before if you change hand position and where the arrow is nocked that changes tiller when the bow is being drawn.
I don't know how other people get their shorter bottom limb but I mark the centre of the bow and go 5/8" below centre mark the handle 2" either side of that mark which is half of 1 1/4" which is how much shorter the bottom limb will be...Glenn...

[osprey1]

"Best thing to do is make several bows and find what works best for you and the way you shoot a bow, but I would be looking at all options...Glenn..."

Thanks Glen. For sure I will try to approach it that way. BTW I was doing a search and found a thread from last year called "symetrical vs asymetrical". I tried to copy the link over to post here but something buggered up. Under the search function (here under the Bowyers Bench) I typed "Torges" and it was one of the last threads listed. More informative great reading on this subject by many of the regulars here.
:-)

[DCM]

I hate to have contributed, in some small measure, to Glenn's turmoil about negative tiller.  While I appretiate his argument, it is sound within it's context, I do take exception to it as well.  More specfically, the theory (in this context the word does not mean unproven, rather the opposite) is that negative tiller causes undesirable nock travel, that is nock travel in the nock down direction during the course of it's return along the power stroke.  This could act to force the arrow into the rest, impeding performance and potentially causing tuning problems.  Ideally you want the arrow to come off the bow as straight as possible, and the nock to travel in pretty much a straight line.  In practice I think what happens is that other parameters of tuning, brace hieght, nock point in particular, and how the archer applies pressure with both his bow and string hands tends to cancel out the effects of, or actually mitigate the tendancy toward this nock down travel.

Negative tiller was first made widely public by Dean Torges in a article in The Bowyers Journal.  While I agree in general with Dean's conclusions, including that cited by Glenn wrt to negative tiller, I think we (Dean and I) resolved that the nock travel aspect may be important, and was not much researched or covered by his article.  They may have back issues at TBJ, and may offer subsequent issues where, for example, Gary Davis wrote another good piece on this topic of arrow pass placement, or relative limb lenght.

Most of all I think it's important for a bowyer who wants to broaden his understanding to a) become as aware and exposed to the underlying science (math and physics) as it practical b) keep an open mind c) try various designs and see how they work for you in practice.  I you are like me, I'd built dozens of bows over the course of several years before I really paid much attention to the subject at all, preferring to just do what I'd always done, based probably on one example from a book I'd read while building my first bow.

[Art B]

Gary Davis done an excellent job on explaining handle placement with his sliding handle diagram. Can't seem to remember him going into any details on adjusting ones grip to the different handle positions to help maintain tiller profile. Someone correct me if I'm misstaken on the latter (I borrowed that issue and don't have it for a reference).

Can't see any string nock travel when you keep equal strain on both limbs from the floor tillering step to finished draw length. Perhaps with unequal limb strain you might see this.

Can't see uneven limb set (as Glenn claims) when tillering while keeping equal limb strain either.

Pretty soon all this is going to dawn on folks that if you keep equal limb strain throughout the building process that you're not going to have the upper limb take additional set over the lower limb.

I'm in no way ragging on Glenn here. Hey, whatever he's doing seems to be working just fine for himself. If others can do the same then that's OK too. It's all about learning and having fun doing it.  

ART B

[DCM]

My perspective is that talking about bow making takes a really far back seat to actually making bows.  but I still enjoy it so here goes.

I agree with you Art about having equal limb strenght to preserve working capacity in your wood bow.  And that if your apparatus doesn't mimick pretty closely actual shooting by hand then the upper limb might well take more set from hand shooting.  Heck, it is shorter after all, in most designs.  

Glenn I'm sure will argue back that making the upper limb more stiff (neg tiller) forces some work load to the lower limb, as the upper won't bend as far if stiffer.  With glass I'm not sure it matters, notwithstanding the effect of unequal limb strenght on nock travel, which while present doesn't seem to be very relevant in practice, at least in the cases Glenn cites.

[Glenn Newell]

All I can tell you is that when you have an equal length limb bow and with the handle in the centre and you shoot the arrow 1 1/14" above centre you are placing more stress on the upper limb, a fair bit more infact.
It's has been admitted that the upper limb is shorter so therefore it must have more stress placed on it. What benefit would weaking the shorter limb have for the bow. None that I have ever seen, just makes the top limb take more set and doesn't feel real good to shoot.
If you make a bow with a shorter bottom limb you positive tiller it and if you an equal length limb bow and you make the top limb shorter by hand placement and arrow pass why wouldn't you strengthen the top limb which is now shorter.
It's the same with glass bows, limb length and hand placement and arrow pass have a big effect on how a bow shoots, infact it is very nocitable...Glenn...

[Art B]

Glenn wrote: All I can tell you is that when you have an equal length limb bow and with the handle in the centre and you shoot the arrow 1 1/14" above centre you are placing more stress on the upper limb, a fair bit more infact.

There's some confusion, at least on my part Glenn, about that statement. How about clearing up something for me. I'm assuming we using the standard four inch handle for this dicussion. Most of us place our arrow pass at the top of our handles. Are you assuming the same?

Because with a same length limb bow with the handle dead center I would place the arrow pass 2" above dead center (that's one version of a symmetrical design). This leaves me with a 4" grip. This design requires a full grip for dymanic balance.

The way you described your 1 1/4" above center arrow pass, you would have 3/4" handle left "above" your arrow pass and that leaves you with a grip of 3 1/4". Is this correct? It's still a symetrical design but requires a straight wrist or lower contact hand grip to mantain dynamic balance.

Using proper grip with proper design you will not place greater stress on the upper limb. This bears repeating, the counter balancing effect of the "bow" hand is being ignored in this dicussion. And it can't be mimicked on a tillering tree. But trying to do so is what is adding the additional stress to the upper limb as you alluded Glenn. Just some humble thoughts on the subject.


ART B

[Glenn Newell]

Pat I set my bows out with a 4" handle centre of the bow and the arrow pass is 1 1/4" above centre. I have never shot my bows with a straight wrist. I started making selfbows with this layout I always made them positive tillered and the top limb took more set but since I started to strengthen the top limb enough to have equal set on both limbs once the bow is shot in all I can tell you is that my bows are now a lot smoother to shoot, and this is true for my fibreglass-laaminated bows as well. Surely if a bow is talking more set on one limb is needs to be strengthened/..Glenn....

[Art B]

Thanks for that clarification Glenn.

If one limb is being stressed more than the other Glenn then you're doing something to promote it during the tillering process. You use a tillering tree and pulling with a rope trying to mimick your draw?

ART B

[Glenn Newell]

I don't use a tiller tree that much Art, only in the early stages and I will not use a tiller stick anymore that pulls the limbs down from the centre of the bow, I gave them away years ago. You can feel when one limb is pulling more than the other...Glenn...

[NightHawk]

what I do is measure the center of the bow then place a mark say an inch above center.Then I cut an inch off of the bottom limb which brings the center of the bow to my second mark, which then becomes my arrow shelf

[Art B]

That would make your arrow pass 1/2" above center I believe. How do you grip your bow? ART B

[NightHawk]

no, it makes my arrow pass at center

[Art B]

Close enough for me!   :D   ART B

[DCM]

I think it puts arrow pass at center as well, but I don't understand how the process is any different by cutting the lower limb.  I just find the center of the stave and place the arrow pass relative to that mark, generally 1" to 2" above.

I tend to use more high wrist than heeling.  I think the more you heel the bow the lower you can place the arrow pass, and/or the more tiller you can use.  But I always get the direction confused, of nock travel versus tiller, and arrow pass versus tiller.  I think it is, the higher the arrow pass the more tiller and the more positive tiller the more downward the nock travel on return stroke.

I try to split the diff with the arrow pass placement so I can have a finished bow for my personal style of shooting with 1/8" or so of tiller and nock point no more than 1/8" or so above 90 degrees.

[Art B]

No, that puts his arrow pass 1/2" above center David..........do the math.

That's incorrect about the closer the arrow pass to center the more you can heel the bow. It's the other way around.

You are however correct about needing more positive tiller when heeling the bow.

Since there is no nock travel at brace I believe any upward/downward nock travel at full draw is irrelevant.

Of course, all this is just my humble poinion on matters, take it for what it's worth.

   

ART B