Stupid ?

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Re: Stupid ?

Determining IBO Speeds (copied)

"Understanding the IBO Speed Phenomenon:

Like it or not, most archery enthusiasts are "speed junkies". Show most guys a brand new bow, and their first question is likely to be "How fast does it shoot?". In the archery industry - speed sells. And like the coveted 300 yard drive in golf, the 300 fps mark seems to be the benchmark. In the current market, a bow that shoots 296 fps (202 mph) is generally considered slow, while a bow that shoots 305 fps (208 mph) is considered fast - in spite of the fact that only 3% separates the two. So manufacturers are under tremendous pressure to produce bows that pump out big 300+ fps IBO speeds.

But as you will soon learn, actual arrow velocity is all relative, particularly with regards to the arrow's total weight and testing methodology. Any bow can be fast or slow, depending upon how it's setup. It's analogous to the idea of "power to weight ratio" in a motor vehicle. If you have a high-performance engine in a small lightweight car, the car will go very fast. But put that same engine in a dump truck, and the dump truck doesn't go half as fast. The same is true for compound bows. Shoot a lightweight arrow in a high-performance bow, and it practically leaves the bow on fire. But shoot a heavyweight arrow through the same bow, and it arcs lazily through the air.

On the most basic level, there are three main components of actual arrow speed: draw weight, draw length, and arrow mass. The higher the draw weight - the faster the arrow will shoot. The longer the draw length - the faster the arrow will shoot. And the lighter the arrow - the faster it will go. So for the purposes of testing, a slick manufacturer could setup a particular model bow and establish their bow's advertised speed using an unrealistic 100# draw weight, 32" draw length, and shoot an anorexic 250 grain arrow. Surely that combination would yield a blazing fast test speed and would help to sell more bows, right? Well, not so fast.

To really compare two bows, we need an "Apples-to-Apples" method of comparison. Since it wouldn't be fair for one manufacturer to test and rate their bows using one standard, and another using a different standard, manufacturers generally rate their bows using the same IBO (International Bowhunting Organization) Standard. To get an accurate IBO Speed rating, manufacturers must test their bows under the same preset conditions: setting the bow for exactly 70# Peak Draw Weight, exactly 30" Draw Length, and they must shoot a test arrow that weighs precisely 350 grains. Fair enough!

However, since most manufacturers rate their own bows - they'll usually give themselves a few added advantages by testing the bows with a bare arrow shaft (no fletchings), a naked string (no nocking point, peep sight, or silencers), and a drop-away style rest. This helps to eliminate friction and squeeze out a few extra fps, but doesn't necessarily reflect realistic shooting conditions. Manufacturers can also squeeze a few more fps by shooting the bows from the hard-wall (forcibly drawing the bow back a little too far) rather than from the soft valley (more on wall and valley concepts later). And finally, the manufacturer's IBO speed is likely to reflect their "best" test, rather than their average test.

Since the industry has no independent testing authority to actually scientifically verify each of the manufacturers' claims, most bows end up with advertised IBO speeds that are optimistically high, and nearly impossible to duplicate. After all, most consumers don't have the benefit of a chronograph, and few people actually shoot 70# DW, 30" DL, and exactly a 350 gr arrow. And even if they did, there will always be some percentage of variance among scales and chronographs to help dismiss any claims of discrepancies. So there's really no way to hold manufacturers accountable for their exact IBO speed numbers. From our experience, they're all guilty of a little IBO speed padding. But in all fairness, most are careful not to get too carried away. A little padding and outright fabricating are different things.

As such, we recommend you consider the manufacturers' ratings as a high-estimate. In most cases, the IBO speed is still a reliable method of "Apples-to-Apples" comparison among different bow models. We just have to accept that manufacturers invariably doctor-up their apples to be a little sweeter than they actually are. It's just part of the game.

In fact, we periodically IBO test new bows here at our facility. Over the course of several years and countless dozens of tests, we have NEVER found a single bow which will actually shoot at or above it's advertised IBO speed - from any manufacturer. Admittedly, some manufacturers come closer than others, but in the real world, most compound bows will actually shoot 10-20 fps less than their advertised IBO speeds. And once setup in a typical hunting rig, most will shoot a measurable 30-50 fps less than the advertised IBO speed.

So while we understand that speed is a big selling point for compound bows and a major performance characteristic that merits concern, we strongly suggest you not get too caught-up in splitting hairs over IBO speed. Compared to the wheel bows we grew-up on, any modern compound bow is blazing fast. In the field, the 296 fps "Slow-Bow" will probably perform just as well as the 305 fps "Fast-Bow". Neither you or the deer will likely ever know the difference."

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