Spine: the final step in matching arrow and bow?

It’s nice to think we may introduce the world of bows to some people. For that reason, this blog about arrow spine is an intro to a key factor in archery.

With an increased selection of limb weights, particularly in the Stinger II range, there also needs to be a broader choice in arrows. If you want to know why, read on.

Whatever bow you have, it will have a minimum weight needed to provide enough resistance to avoid (potentially explosive) damage to your bow’s limbs. The decompression of bow limbs without anything to slow them down can cause them to shatter and that’s why dry-fires (shooting without an arrow) or arrows that are too light should be avoided at all costs.

You can usually find your bow’s minimum arrow weight on the bow manufacturer’s website, the user manual, or by writing a friendly email. It is true that some manufacturers keep such information to themselves. In that case, all you can really do is put one of the complete arrows that came with your bow on a decent scale and weigh that.

What is spine?

Another aspect of arrow design is spine. Spine is the amount of flex in an arrow’s shaft. Or rather the amount of flex when you put a weight (1.94 lb or 880 g to be specific) on its centre point.

So let’s imagine two types of arrow. Both are 28” long (like those 1.94 lb, it’s an industry standard for measuring arrow stiffness), but have very different stiffness. If you support both at their ends, and hang that weight from their midpoint, the stiffer arrow will bend less. Logical, right?

Now imagine that the less rigid arrow is shortened and measured again. Being now shorter, it will flex less. This in turn means that, at some point, it will be short enough that its flex is the same as its stiffer brother’s.

Flex is not always the same

The above scenario explains how the amount of flex will change depending on the length of shaft you’re testing.

In archery there is a sweet spot of flex needed in your arrow for it to launch cleanly and fly true. That comes from making sure your arrow’s spine and the ideal spine for your bow are the same. And that ideal spine is decided by your bow’s power and the length of arrow you choose.

So when choosing arrows off the shelf (or off the screen, these days), or buying components to build your own arrows, you will need to take this into account.

Thankfully most reputable arrow/shaft manufacturers have charts you can check: Find your bow’s draw weight along one edge, find your arrow length along the other and where they meet is your required spine.

All this means that too flexible or too rigid will cause you accuracy problems and now that we’ve established the impact on accuracy, here’s something even more crucial.

Spine is also important from purely a safety point of view. If you have a powerful bow and use it to fire an arrow of insufficient spine, it will flex so much that it may even fragment.

In fact, if your arrow offers too little resistance to the limbs, they may lack the necessary resistance while decompressing. And that spells the “dry-fire” scenario described above. So not only do you risk damage to your arrow but also your bow and, most importantly, you risk injury to yourself or others.

Other factors

Even such changes as a heavyweight tip (field-tips weighing up to 175 grain are not hard to find) can mean a large inert mass at the far end of your arrow. This also increases the chances of your arrow fragmenting as it struggles to both absorb the power of the bow launching it and get that field tip moving.

Basically there is one big and crucial lesson to take home from this: choosing arrows is more than just finding the cheapest bundle of 12 arrows online and shooting them. And building arrows is not something to be considered without educating yourself beforehand. Thoroughly.

Tried and tested

All this is the main reason why it is always our recommendation to buy the arrows for our products from our website. For example, the recently announced light and heavy line of carbon arrows for the AR-6 Stinger II repeating crossbows will mean you can buy the arrows to match your limbs.

Be they the hassle-free 35 lb CQ limbs or the highly-anticipated 150 lb hunting limbs, you’re sure to get arrows that have been carefully tested and matched to your crossbow or your FENRIS and have been produced with the same care as other goods sold with the Steambow brand.

So, arrow weights and spine causing you headaches? Steambow has done the leg-work: shop with confidence. You order, they arrive and you shoot them with confidence. It’s far simpler and far safer and the results are as good as you could hope for.

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