31" Draw Lower Weight vs Shorter Draw But Heavier Weight

[cloudbaseracer]

Hey Gang,

I am curious if there is any data (maybe the bowyers can chime in) on the performance difference with a longer draw but lower poundage?
Example: Given the same bow manufacturer/model and same Grains Per Pound (not literally the same arrow) - Does a 31" draw at 41lbs have more speed (performance) than say a 28" draw at 46lbs? 
Is there a chart someone has produced somewhere that kind of covers this?
Does it change if the bow is a standard design vs a Super Curve? 

Thanks,
James

[Archie]

Very interested in this topic.  You'd think that since the 31" draw-fired arrow has a "running start" by the time it reaches 28", it should be quite advantageous.  Like bore-ing and stroke-ing an engine... longer stroke = more power.  But I've never seen data that sheds light on this.

[Orion]

Longer draws extract more energy from the bow.  The draw force curve is larger and the arrow stays on the string longer with a longer draw vs a shorter draw.  Thus, more energy is imparted to the arrow.  That being said, I don't believe anyone has come up with a comprehensive comparison/data set of various draw lengths and weights within the same bow design, though some bowyers may have that type of information recorded for their own bows.   

[FLHNTR]

Very interested in this topic.  You'd think that since the 31" draw-fired arrow has a "running start" by the time it reaches 28", it should be quite advantageous.  Like bore-ing and stroke-ing an engine... longer stroke = more power.  But I've never seen data that sheds light on this.

The only available data I’m aware of comes from the compound platform, specifically from the companies that design bows with cam specific ordering specs. I think specifically of Hoyt when they had the Carbon Element, and you got a #1, 2, or 3 cam. For example, the #1 cam@27” where it maxed out had more performance than the #2 cam on its lowest setting. To compensate for short draw lengths, a lot of archers choose to shoot 70-80 at 27” and under, at least that’s what I’ve been reading on the internet.

Regarding trad bows, super recurves are designed to store more energy than traditional recurves, and traditional recurves > longbows in terms of sheer stored energy. That’s why you see a lot of the traditional long bows offered at HH weights and higher. Idk if I answered anything, but I thought this information was relevant to what you’re asking.

[Steelhead]

Well said Kris.

I think I read a while back that every inch of draw adds about 5 FPS in general.But its hard to quantify everything specifically as Kris mentioned.

But its safe to say in a nutshell that a longer draw imparts more energy to the arrow and has more power inherintly than a shorter draw as a basic rule of physics.

A bigger egg head than me may have more educated information than me.

Good question.I Have not seen it discussed much in a long time.

[Hud]

  I doubt you will find a bowyer that can build a bow that will shoot a 31" arrow as well as a 28" arrow, or vise-versa. There are simply to many variables in a random test.

[Mark R]

If it is the same designed bow same length then the longer 31" draw bow will have a draw weight less then the 28" draw bow by maybe 6 to 15 or so pounds depending on design given that standard bow weights are scaled at 28".  IE 28" at 46lbs and same bow at the 31" draw at 41lbs would have a draw weight a lot less at 28" say maybe a 30 to 35 pound bow at 28", also the same bow may not be designed to be drawn to 31", as mentioned a lot of variables to deal with.

[cloudbaseracer]

If it is the same designed bow same length then the longer 31" draw bow will have a draw weight less then the 28" draw bow by maybe 6 to 15 or so pounds depending on design given that standard bow weights are scaled at 28".  IE 28" at 46lbs and same bow at the 31" draw at 41lbs would have a draw weight a lot less at 28" say maybe a 30 to 35 pound bow at 28", also the same bow may not be designed to be drawn to 31", as mentioned a lot of variables to deal with.

That is not at all what I wrote or was asking about.  I was talking about 2 different bows from same manufacturer. 

I am sure there are some really technical bow builders on here that will have some valuable insight.

[Mark R]

Sorry maybe I read it wrong you did say same manufacturer/ model, Again many variables, I think you'll get  different results depending on the Bows tested, good luck finding a precise answer

[Archie]

Maybe it's just me, but it seems like this short discussion is getting overly complicated and is not gaining good momentum. The way I see it, draw a bow back to 28 inches, and measure its performance. Then draw the same bow back to 31 inches, and measure its performance the same way. Then the question is, how heavy does that same model bow have to be at 28 inches to get the same performance results as the first bow at 31 inches...

[Wudstix]

It is my understanding that the bow is designed to be a specific weight at whatever length it was built for.  i.e., 27" or 28"  Every inch or part of an inch past that will be more weight.  My DL is 27 3/8" so I add poundage past 27" and subtract poundage from 28".  I then put the bow on a scale and verify what weight it pulls at my draw.  So, theoretically 31" would load up the bow to a higher poundage than a 28".  Most of my custom are made at 27" and I add one pound plus to draw weight.
 

[Archie]

I used to draw 31", and have one set of recurve limbs for my Black Widow that are 49# @ 31".  I also have a set that is 51# @ 29", and a set that is 62# @ 29".  I am drawing about 30" now, after breaking my draw-arm shoulder last year.  I've talked to Black Widow a lot about my bow/limbs, and the bow was definitely designed to handle all those draw lengths.  My brother has the same model and limbs, and his are marked at 32.5" draw length for him.

If a person short-draws, they definitely lose performance.  And, within reason, it doesn't make sense that a bow drawn an inch or two further would not gain performance.  Again, my thought is that it would be interesting to know that if two guys have the same model bows, side by side, and one draws 28" and one draws 31", what poundages do those bows have to be, to have the same energy output?

[Maynard Ferguson]

Last year I made a big change and started shooting left handed. Bow #1 is a 25" Hoyt GM with #36 long limbs. Adjusted tiller a bit until It was shooting quietly and bareshafted well. Struggled a lot with alignment in the beginning. I have learned that this bow was actually pulling 9lbs heavier at #45.  My hunting bow is a 17" Morrison Phoenix with ILF limbs. I'm still tuning, but currently 41.5lbs at 30 inches. I suspect the #45 bow is potentially faster, but I'm still short drawing it (probably around 28"). I can draw the lighter bow to full draw (scapular engagement) and my fixed crawl is the same. Without a chrono I can't tell how much of a difference there is between the two. Advantage goes to the bow/draw weight that I can handle well and shoot accurately.  In my case #41.5 @ 30".