Limb Alignment????

[Bald Eagle]

Timid Toad you are asolutely right! Modern bows longrod bushings are 99.9% spot on, but you still have to find a long rod that screws in straight before you can attempt limb alignment! I've got one that I only use for this purpose and I guarantee any bow I set up is spot on! Beiter limb guages are precise, more precise than masking tape and two arrows placed under the string at either limb tip!! Sid Ball at a coaching conference at Lilleshall ,a few years ago now, changed my mind on a lot of these "theories", Straight limbs on a bent riser will give the same result!!

[Big Boy Blue]

Im not sure that the Beiter Limb gauges are far more accurate than using masking tape, I guess it depends on how you set things up. I place masking tape at about 20% and 80% of limb length. I then use an engineers digital calliper to measure the width at those points. The calliper is then set to half the distance and I mark the tape, which are then highlighted with a fine point pen.

This gives very precise alignment and when I have checked with limb gauges there is no difference. You do however have to be carefull about how you use limb gauges as they can give slight offsets if not mounted properly.

[geoffretired]

Bald Eagle, your post made me think about the riser being twisted but showing up as twisted limbs. Using two arrows across the limbs at the pocket ends, could be used to check the riser at the start. If the riser is twisted, it will show as those arrows will not line up. I'm assuming the limbs are seated onto the surfaces of the riser that need to be in line with each other.

[Timid Toad]

This was part of my thinking. When CNC risers first came out everyone scoffed because they said they couldn't be made straight (not that the Mag Ally ones were either), until I think it was Stylist's use of stretched plate. So I always check riser and limbs. I haven't found a problem with either limbs or risers since returning to the sport, but if you have a twisted riser, do you offset the limbs to counteract this, or stick with straight limbs and live with the twist in the riser?

[geoffretired]

Timid Toad, about the twisted riser; I suppose we are talking theoretical and the bow is out of guarantee etc.
If the bend was visible from the shooting viewpoint, so the limbs were not in line, they could be adjusted until they were. I think some risers allow for this sort of adjustment. If the riser was twisted when viewed from the top limb pocket it might be more tricky depending on the limb fitting. I would want to get rid of that sort of twist as it would be causing the limbs to twist as they are drawn.

[TJ Mason]

As an aside, I'd just like to point out that limb alignment has nothing to do with compensating for a twisted riser. It's a fine-tuning mechanism.

The style of the archer affects where the "true centre" of the bow is. Limb alignment allows the bow to be adjusted to the true centre for that archer.

Earl Hoyt actually invented the limb alignment system in the Seventies, but it wasn't made available until the 1990s because Hoyt feared that people would think its purpose was to compensate for twisted risers. Denise Parker wrote a nice article about this:

http://www.arrowstar.be/downloads/Avalon_Tuning.pdf#search=%22%22denise%20parker%22% 20limb%20alignment%20%22

[Rik]

No one has mentioned the 'mini-plumb bob method'.

You support the bow (string upwards) across a couple of stools (or other hand supports) and hang mini-plumb bobs (say, darning needles strung on thread) from the string). If you make the thread long enough, the needles will hang close enough to the riser/limbs to see the limb allignment fairly clearly. Also, supporting the bow on a couple of level surfaces placed at the base of the limbs can give an idea of whether the whole setup is straight or twisted - both ends should sit flat on the supports.

Yet another tool in the archery pedant's repertoire...

[Timid Toad]

I'm not talking about any bow of mine...warranty or not, Geoff, just risers always were a little off, to a greater or lesser degree. Hoyt and Yamaha were very good, but I have seen a Samick (made about 1988) that had a noticeable twist. It was just something you lived with, because you couldn't adjust the limbs then either.
I have noticed that BMG used no system for altering string alignment on their last riser, presumably because fiddling around can cause more problems, and limbs are definitely made so much straighter these days?

[joetapley]

IMO the purpose of limb alignment for a recurve is that the when drawn the limbs bend at 90 deg to their surfaces and the limb tips travel back in a straight line. So agree with T.J. that it's more a tuning/setup function.

If the limbs aren't "aligned" then the limbs will twist during the draw and on release you will get torque and arrow-button interaction issues much the same as an incorrectly placed bow hand.

I favour (sensibly) using the longrod as the end gives a high degree of parallelax sensitivity. It's very easy (from experience) for the alignment to be quite a way off just using the Beiter Gauge/masking tape approaches on their own.

[tel]

I do like the suggestion that the eye is some sort of natural protractor for measuring 90 degrees - I've worked with plenty that wouldn't know a right-angle from a triangle!