Top Limb 1-2" longer

[bigcountry]

I know Dean Torges and others suggest to make your top limb 1.5" longer.  He says for balance after the shot.  I thought it was due to the arrow already being 1" over center (on a bow with equall limb lengths), and you usually nock an arrow antoher 1/2" higher to get good flight. 

So far, I have made all bows equal limb lengths with center being dead center of handle.  But the last bow had me thinking.  I had the bow tillered perfect, I then shot in about 100 shots and somewhere during shooting, I got a slight hinge right at a point where I had thin latewood and fairly thick early wood underneath.  I since have seen the advantages of a faceted belly. 

I shoot 3under.  I hold the bow pretty well dead center of the handle.  So I figured I am putting more strain on the top limb. Not as much as a split shooter, but bottom line I put more strain on top limb.

I know its been hashed over a few times.  But I am thinking on my next bow making the top limb 1-2" longer.  What thinks you guys? 

[Kent D.]

I have built bows with both limbs the same size with no problem.  In general, I usually make my upper limb a tad  longer.  Either way, Ive never really noticed a difference.  I guess the amount of positive tiller might deal with any issues.  Not sure, just a thought.

[JackCrafty]

I've got to admit that this subject is confusing to me.  Maybe this time around someone will explain it really well....so an ADD person can understand whatever it was we were talking about.

Also, uh, oh yeah, why not just lower your grip instead of making the limb longer?

[bigcountry]

I have built bows with both limbs the same size with no problem.  In general, I usually make my upper limb a tad  longer.  Either way, Ive never really noticed a difference.  I guess the amount of positive tiller might deal with any issues.  Not sure, just a thought.

I think the root of the issue I had was it was just a weak spot and tiller changes after being shot.  I learned the hard way.  I didn't have much room to move on the poundage.  If I would have built it right from teh start and had 5 lbs to play with, I would have had it shot in, and sanded right to my wieght.  I am still learning as you know.

[adb]

When you build a bow with equal length limbs, and tiller it at the bow's center (which is the middle of the grip), you end up with a longer lower limb. This is because you have to grip the bow in the middle, and the arrow pass usually ends up about 1.5" above center. This is where the +/- tiller comes in. Because the bottom limb is longer, you need to make it a bit stiffer, so the limbs recoil together. This is negative tiller, or the distance from the limb to the string on the lower limb is less than the same spot on the upper limb. The bottom limb can be determined at any point during the tillering process. If one limb continues to be consistently stiffer, I make it the bottom.

If you make a bow with a longer upper limb, the arrow pass is now the middle of the bow (and the balance point). You have to tiller the bow with the upper and lower limbs determined before you start. The advantage is, upon realease, the lower limb does not "drag anchor" and move forward, because the balance point is now at the top of your hand where the arrow passes, not in the middle of your hand. With an asymetric limbed bow, you should tiller it even, no +/- tiller)... the bottom and top limb should be the same, as they are now the same length.

An easy way to make sense of this: take a bow you've made with equal length limbs, and balance it on your hand with the arrow pass as the balance point. What happens? Well, the bottom limb will drop because it is longer, and therefore heavier. Do the same with a bow tillered with a longer top limb. Balance the bow in the same way, with the arrow pass as the fulcrum point and what happens? The bow balnces perfectly, because the limbs are equal length.

The down side... asymetric limbed bows are a bit harder to see perfect tiller. A bow tillered from the center of the grip, is easier to see perfect tiller. I've made many bows with both methods, and personally, I don't have a preference. I think an asymetric limbed bow is a bit more difficult, but I don't think they shoot any better. I must admit, they do balance very nicely in your hand, however.

[bigcountry]

Thats a pretty good explanation.   

[nickf]

I have actually built 'symmetric bows'. The lower limb always turned out to get more set. Then I started making longer upper limbs, and a slight positive tiller. Set was equal

so without any theory, or science behind it, It just prooved to better to have a longer upper limb and a postive tiller

I addition, you'll all know how bad it feels when you have a weaker, lower limb, feels bad in the wrist. However, if you have a weaker upper limb, things balance better in your hand, and things feel better in you wrist.

So, just from my feelings and observations I can tell that a longer lower limb and positive tiller is better for the bow. That's the way I prefer it.

however, if you have a symmetric tiller, with symmetric limbs, you should actually make the lower limb longer, to equal the set (thus strain). This is also what Comstock adviced. He especially pointed on the fact that your upper limb often get's caught in low branches etc, but that you rarely have such problems with your lower limb

Nick

[adb]

There is no doubt that the bottom limb is under more strain. Actually, I now brace my bows (using the push/pull method), with the bottom limb up. I used to brace my bows with the top limb up, as most people do. Not anymore. I turn the bow around, and realease the string from the bottom nock. I believe my bows are much happier as a result.

[Aries]

Ive made all of my bows Assymetical since reading Hunting the Osage bow. I have found that these bows preform just as he says. Ive had guys who have never shot a bow before pick one up and be shootin in some pretty tight rings after the first few arrows. It is a bit of a pain the first or second time tillering this style of bow, but thats the only draw back Ive experienced. Ty

[Gordon]

I've made bows both ways. I like making the upper limb longer because the bow will balance better in the hand when carrying it and that's important when I am looking for elk all day. I've never noticed any difference in shootability, however.

[bigcountry]

There is no doubt that the bottom limb is under more strain. Actually, I now brace my bows (using the push/pull method), with the bottom limb up. I used to brace my bows with the top limb up, as most people do. Not anymore. I turn the bow around, and realease the string from the bottom nock. I believe my bows are much happier as a result.

First post, I was right with ya.  You said in the first post, the bottom limb is longer.  I understand that over arrow location.  But if its effectively longer, wouldn't it have less strain?

[DCM]

WRT what is symetrical, or not, it depends upon the perspective.  From the perspective of the arrow, the string is all it "sees."  And if you bend a string together at the nock point you'll see more dramatic asym in the so called "even" bow where arrow pass is arbitrarily established at 2" above dimensiional center.  And for no other reason or justification that I can find than because somebody suggested it.  In fact in antiquity, where ideas are more thoroughly evaluated, arrow pass closer to center is very well represented.

Couple of points where I differ.  First, when upper limb is farther from the string, that is called positive tiller.  This is the most common config, even if arrow pass is at center.  It's simply a matter of degree, when arrow pass is closer to center less (positive) tiller is needed.  But due to the effect of the geometry of the string hand being necessarily above the bow hand (can't tshoot through ones own hand), some degree of positive or even ideally keeps the nock travel up then down instead of vice versa.  Folks generally find nock travel in the opposite direction not as easy to tune for, ie. requiring higher nock point.  Second, the lower limb is rarely if ever under more strain.  It is stiffer yes, but doesn't bend as far as it is longer.  Strain is all about bending radius.  It may store more energy, and certainly delivers more, relatively, by typically it enjoys a better string angle.

Arrow pass at center bows have the apex of the curve at the arrow pass.  So called symetrical bows, more accurately shorter upper limb bows, apex is at dimensional center of handle, or under ones palm on the bow hand.  As such one must adjust their eye for proper tiller, incorporating the handle in the lower limb rather than ignoring it, and/or how we setup on the tiller tree.

Regardless of the config, balance is imperaitve.  Geometry won't combat one limb taking more set, or hinging.  That's all about the process of the crafting, not so much design.

In practice I find a happy medium w/ arrow pass about 3/4" to 1" above center.  What suits you best may be different, based largely upon how you place pressure with your bow hand and string hand.  One test I use is, I want relatively less positive tiller, and relatively less nock height, about an 1/8" being as close to the edge as I care to tread. 

[DCM]

"...why not just lower your grip instead of making the limb longer?"

Same thing.  Lowering arrow pass necessarily lowers grip, and shortens lower limb relative to upper.  Again, from the arrow's point of view it's all about the relative lenght of the segments of string above and below the nock point and the consequence of same, the angle the string makes at the upper and lower string grooves.  The more out of whack these, the more tiller you need and the higher the nock point, the more rotation the bow will make on the draw, the more nock travel on the loose.  It's all about vectors, in physics terms.  The more in front of the load, the more efficient the tow.  By being shorter, the upper limb stacks more, builds weight more quickly at the upper end of the draw than the lower.  So we make the lower stiffer to begin with, to compensate.

[George Tsoukalas]

Big, I make my bows with the same length limbs. I place the arrow pass an inch to 1.25 inches above center point. DCM, I agree 2 in may not be a good idea. I tiller the lower limb about 1/4 inch stiffer at full draw.  I've made a few bows with shorter lower limbs but really didn't notice anything about them that was special. But the sample is way too small to have any significance. I really can't or don't want to wrap my mind around this issue but Torges has but I'm too set in my ways to change much. LOL. Dean sure has engendered forum discussions about this topic. I can't even begin to consider the implications of drawing with 3 fingers under in regards to shorter lower limbs. You may have to experiment. I would begin by using same length limbs and really looking in the mirror as you tiller or have someone snap a digi which is what I do anyway even for my split finger draw. I would aim for 1/4 inch stiffer lower limb but at FULL draw. One more point regarding lower limbs is you have to really decide early on which limb will be the lower one. My last few bows have been difficult to tune and I've had to turn the bows around to tune them. I don't steam and heat correct much if at all so I have to leave that avenue open. If I remember correctly the Dean steams and bends on a form right from the outset (wood is still green)  which would make deciding upper and lower limbs easier. Anyway, have fun experimenting. I think my experimenting and high volume bow making days are done. I gotta mow the lawn and work in  the garden as soon as they dry out. Jawge

[Pappy]

I do about the same as Jawge,nothing wrong with the longer top limb,for sure, I'm just  to 
old or maybe hardheaded to change. I have made a few with shorter lower limbs but it was out of necessity ,had a problem with it to weak and couldn't flip the bow over for some reason.I really couldn't tell the difference but as Jawges said haven't done enough to know for sure ,and there
was nothing scientific about it.
   Pappy