Questions about assymetrical limbs?

[Sidewinder]

I decided I would try to do one with assymetrical limbs and was curious what type of layout those of you that do that use. I don't mean limb width and stuff I mean length ratio etc. I undestand the bottom limb needs to be shorter but how much? and....how does the tiller look differently? Post pics if you can. Oh yeah, what do you guys think the advantages are verses dissadvantages?

I'll be waiting with baited breath......Danny

[richardzane]

you might look into Japanese bows
http://en.wikipedia.org/wiki/Yumi

[Will H]

I usually make my bottom limb an 1 1/2" shorter when I make an asymmetrical bow. As for the layout... Just lay it out the same as your top limb. It's just shorter. Measure from fade to nock and mark midlimb on both limbs. Then layout the bow accordingly. On bows longer than 64" I usually make my bottom limb more like 2" shorter remember though if you decide to do this early on you're pretty much stuck with the decision of top limb bottom limb. So you will have to do string alignment with heat or leave the tips wide until you're at low brace and can get an idea of how the string lays.

[Sidewinder]

thanks Will. Do yo have one you can post full draw on, I wanna see what it looks like.   Danny

[tom sawyer]

When you think about it, there is generally no true symmetry in a bow anyway.  You hold the bow towards the middle and the arrow passes above that by an inch or more.  Making the lower limb a little shorter puts the arrow pass a little closer to center, but still the pivot point at your palm is a little lower and the limbs are a little different.  It really doesn't matter much, they all shoot nicely if well tillered.

[steve b.]

I do what Will H does--the longer the bow the bigger the difference in the length of the two limbs, in general.

I experimented once with a 70" osage bow that I originally made symetrical.   I moved the shelf up and down on the handle several inches and shot it after each move.  Then I put the shelf in the normal spot and began cutting the limbs down, one at a time, a half inch at a time, and shot it each time while checking for any differences in either vibration in the hand or how the arrow flew.  Honestly there was not alot of difference in all the changes but I settled on just having the upper limb somewhat longer. 

So you could do the same thing by starting with a slightly longer, symetrical bow and making small changes up to some point and call it good..?

[Will H]

I don't have any on my Photobucket to post but I have a couple old BOM's that were asymmetrical. My hole bow and my 100yr fencepost bow. Don't know how much that will help ya. I just finished tillering another fencepost bow that is 62" and asymmetrical. I'll be posting it up soon.

[Sidewinder]

Tom thanks for the input, by the way its good to hear from you haven't seen much of you lately.

Will, I will be looking at the hole bow you mentioned and pay more attention to the full draw. I am also looking forward to seeing your newest creation.

 It would seem to me that a shorter limb would bend less than a longer limb, is this correct or should it be bending more? I just finished up a light weight hackberry for my step mom that I did assymetric and the top limb bends more. It shoots real good but the tiller seemed a little funny to me. I wanted to examine some pics of others tiller with unequal length limbs just to get a good picture in my head as to what I should be looking for when I do this next one for my wife.
 I figured that since I was making light weight bows under 40lbs it would be a good time to experiment with something that I haven't tried that much.    Danny

[Hamish]

I don't know how important it is, but its an issue in bowmaking that I think about frequently.

The arcs of the two limbs are subtly different as the shorter lower limb obviously has to bend further. They usually aren't identical even in an equal length limbed bow. Even so much of the time I make the lower limb bend not quite as far as the upper. I take into account the amount of set each limb is taking. If there is an obvious discrepancy, I weaken the stronger limb, balance that with the shape of the drawn bow, The end result is the longer limb,( or upper limb in a equal limb bow), usually (but not always) ends up with a 1/8"-1/4" positive tiller.

I generally like the feel of an assymetrical limb bow when shooting, more than an equal length limb bow. Its very subjective and there's not much difference between the two styles.
Manufacture is much more simple, in terms of layout, and tillering/string alignment over arrow pass with equal length limb.


                                            Hamish.

[steve b.]

I tiller by pulling the string from the arrow nock point.  When using the tiller stick I tiller so that the limb tips move the same distance from the floor, as well as making sure the limbs bend evenly, to about 16", then I finish tiller pulling by hand with the mirror.  Works for me.

[gpw]

  If you think about it , likely the very First Bow was asymmetrical   , just a branch  eh ?  Stick and string .... 

[crooketarrow]

  I've built a few bows like this but over the years I've came to the conclusen that unless you shoot a couple 100,000 arrows from your bow 3 under. THEN I'M NOT SURE IT WOULD EVEN MATTER THEN. Your building a hunting bow. Haveing a stiff bottom limb dose not matter.
  There's been years when I've shot hours a day ,1,2000's of arrows a week. And I have shot over 100,000 arrows a year from the same bows. I've never had any of my own or have ever had some one send me a bow back because of the tiller chaged FROM EVEN LENTH LIMBS.
  Now thats useing a split finger hold. I hav'nt any exsperance with 3 under. But like said I've never had a bow returned. I know some of these went to 3 under shooters.

[Sidewinder]

thanks for the feedback Crookedarrow. I am taking all of these comments into consideration.   Danny

[blackhawk]

I make bows both ways and have no preference over one over another...each has its pros n cons to them to consider...the beauty of an assymetrical bow is its a better balanced bow in the hand...a symmetrical bows top limb will naturally tilt down when carrying it ..and when in need to raise the bow effortlessly with less movement to bring the top limb up when in need to quick raise your weapon and shoot is an advantage IMHO.

[blackhawk]

Here's one of my assymetrical jobys....its an osage Andaman holmgaard.   Ya gotta look reeeeal closely to see it. One give away is you can see the arrow pass is at the bows true center. That's still one of my fastest selfbows to date.

 http://www.primitivearcher.com/smf/index.php/topic,28407.0.html