Winding up limbs bad on 30" draw length?

[geoffk]

Following up from the other thread on bow poundage, I have just worked out, that in reality as I have removed 2 washers from my bow to increase the draw weight, has in effect done exactly the same as having an additional 1.5 inches of draw....

Now I have read here, and also heard from other people that you should only go up say 10% on draw weight by winding up the limbs, but as this is exactly the same as drawing further, then obviosly you cant have it both ways, thus is it 10% total? and with my 30 inch draw, and wound up limbs, I will have gone way over the 10%?

I have heard the term "stacking" and am possibly into this, but how bad can this make things?

Am I loosing stability?

Am I gaining speed at 38lb on the fingers by the over draw compared to non wound up 38 pound limbs at 28 inch?

What happens to everything when I eventually get my new higher poundage limbs, but put the washers back into the bow?

Lots of questions!

Thanks

[JohnKR]

I think you are getting confused here. There are two different things to consider, one is the limb weight, and the other is the weight on fingers.

The poundage marked on the Limbs is when drawn to 28”, if you draw to 30” this will normally be increased by around 2lb per inch, so 4lb extra. Now if you wind up the limbs the poundage will increase both at 28” and at 30”.

For example, I have limbs marked 36lb, I draw 30” my limbs are wound fully out, and weight on fingers is 40lb. if I wind the limbs up fully (10%) I will get 44lb on fingers.

This is all “rule of thumb” as some combinations of riser and limbs will give differing amounts of adjustments, and they don’t always come to 10% overall. Also some are measured wound half way, some at wound out.

Stacking, to keep it simple, imagine drawing a bow string back, and each inch you pull adds another 2lb of weight to the draw. These would be smooth limbs, but, if the last inch before anchor added another 4-5lb it would be harder to pull through the clicker, and this would be known as stacking.

[geoffk]

Originally Posted by JohnKR

will increase both at 28” and at 30”.

For example, I have limbs marked 36lb, I draw 30” my limbs are wound fully out, and weight on fingers is 40lb. if I wind the limbs up fully (10%) I will get 44lb on fingers.

No, I dont think I am confused, a 36 pound limb at 44 pounds on the fingers in the example is way way more than 10% over marked weight. (20% extra!)

So thats 20% extra over marked weight, so im trying to ask the questions over the 20% extra over marked weight, when its suggested 10% is the rule of thumb.

If its 10% wind up from a random start point, then its not a very good rule!

Winding up a limb seems to be exactly the same as a longer draw, ie an archer can get 4 extra pounds by "either" pulling the bow past 28 inches, or winding up the limbs by 4 pounds.... (or of course a combination)


What does this do to stability or speed, when compared to a "nominal" limb

[Random_guy]

I'm afraid i have to agree about the being confused part.

Basically the answer is that its fine to wind the bow in, irrespective of drawlength. The whole thing of 10% weight increase is just very roughly the difference between limbs wound all the way out and all the way in at 28".

I've heard various things in the past about people saying limbs are designed to be shot from a certain position in the limb pocket, but to be honest, even if this true, only people shooting immense scores would have a chance of noticing the difference, and even then i doubt it.

Either way, the 10% thing has nothing to do with draw length.

[AlanT]

John is correct in what he says. This is how I understand it (sorry if I repeat what has already been said).

The 10% 'rule' applies to the limb weights at a draw length of 28". It is important to remember this as it is the reference point for draw weight measurements.

Assume you have a limb marked at 36lb 'wound out', this would give approx 10% more 'wound in' say 40lb .

This still applies at a longer draw length. In the example given, 36lb marked weight 'wound out' would measure approximately 40lb when drawn to 30". Winding them in, would give 44lb when drawn to 30". This is a 10% increase, so the 'rule' holds true.

What we are looking at is the increase in draw weight between 'wound out' and 'wound in'. The AMO standard states that limb weights are stated at 28". Shorter or longer draw lengths will change the starting point up or down (to confuse things, some limbs are marked for the riser at mid-position, some fully wound in).

Hope this helps

Alan

[Desert Archer]

Instead of worrying so much about the % increase, think in terms of the pre-load you are putting on the limbs. Like any mechanical system limbs have a range where they work best, are more efficient. That is usually some where in the middle, rather than at either extreme (limb bolts all the way in or all the way out). This is complicated by draw length. Longer draws need to keep the pre-load (initial tension on the limbs, produced by the bolt setting) low because they are going to take the limbs to or beyond the range where the limbs perform well. Like wise, a short draw would generally need the limbs pre-loaded because they aren't going to be pulling far into the "performance range" if at all.

I draw 32.75" from the nock groove to the back of the arrow shelf. I make it a point to only screw in the limb bolts just enough to get the tiller I want. At my draw I don't need (or want) to pre-load the limbs as I'm going to load them more than enough at anchor.

Hope this helps understand better what's going on.

Dave

[geoffk]

Originally Posted by Desert Archer

Like any mechanical system limbs have a range where they work best, are more efficient. That is usually some where in the middle, rather than at either extreme (limb bolts all the way in or all the way out). This is complicated by draw length. Longer draws need to keep the pre-load (initial tension on the limbs, produced by the bolt setting) low because they are going to take the limbs to or beyond the range where the limbs perform well. Like wise, a short draw would generally need the limbs pre-loaded because they aren't going to be pulling far into the "performance range" if at all.

Yep, that makes it very clear, thanks. The "winding up" is a very poor term, I will forget about it now, as its rubbish. I can see clearly that the adjustment in the limbs is purely to account for the "pre load" according to draw length.

This reason has maybe been forgot over time (and internet )

So I have put a bit too much pre load into my limbs, thats fine as its just to get me used to a bigger draw length. Once I get limbs the next step up, all will be fine again

[BorderBows]

the more radius you have in the power section of the limb at Brace height, the more the nocking point becomes vertically unstable. To reduce the radius, you should only use the first 5% of the adjustment in any serious way. the reason for this is that the limb butt is more inline with the limb to give less radius.

If your using more than that first 5%, then you should be looking at new limbs to get the best from the geometry.

The vertical NP stability is something that is visable with grouping issues with unequal finger release, as when little movement is available then the NP stabilises quicker during the shot.

does that make sence?

We have also noticed that 36lbs on your fingers is 36lbs on your fingers, and to achive this same weight if limb A is at minimum and B is at max, B will be the fastest, but most unstable. You are stressing the limbs more, but your kicking them out of geometry...

[geoffk]

OK, thats fine, I will work with my cheaper limbs for the time being to build up strength. I guess that when I get the next set of limbs, as im intending to spend a bit more on some carbon foam ones, I will get some of the lost speed back, and all the lost stability

I will do some searching on limbs as I dont intend to buy them for a couple of months.

Thanks