The Great Longbow Debate

[wedgeski]

I'm no expert but if I vaguely remember a rather good TV program I saw on this recently, medieval archers were trained from a very young age in the use of a bow so that their muscles developed in exactly the right pattern to pull draw weights that would seem obscene by modern standards.

 

[CharlesRyan]

Hi, all--

I'm not a longbow historian, but my credentials include being a perennial visitor to the Mary Rose, having sat through numerous reenactor lectures, having several times attempted (but never succeeded!) at drawing a true longbow, and having just (last week!) finished reading Bernard Cornwell's Azincourt. Here are the opinions of a well-informed amateur.

• First, the longbow (or warbow, as it was actually called back then) should be an exotic weapon. Proper use requires substantial specific training; most people--even very strong men--couldn't even properly draw a longbow. Also, the longbow isn't aimed the same way as a shorter bow or crossbow, because the string is pulled back behind the ear (instead of to the cheek).
• Draw strengths vary; 100lb +/- 20lb seems to be average. (?) (Compare that to modern hunting and competition bows, which are more like 40lb - 60lb.) There were bows with draw strengths approaching 200lb found on the Mary Rose; there may be no-one alive today capable of pulling those bows. (See again my thoughts on the longbow as an exotic weapon.)
• A proper longbow isn't just long; it's made out a specific type of wood (yew) cut in a specific manner. (Ironically, although the English were the only society to really adopt and master the longbow, the best yew wood was imported from southern France.) Dimensionally, the longbow is as long or longer than the user is tall.
• In terms of accuracy, in the hands of a skilled user the longbow was very accurate at short or moderate ranges. The necessity of a "rain of arrows" was only at more extreme ranges (around 200 yards).
• With an armor-piercing arrowhead (called a bodkin), the longbow could penetrate virtually any armor, though at range it needed a good, square hit to penetrate heavy plate.
• Power and range-wise, the longbow was slightly inferior to a heavy crossbow. And a crossbow could be used with very little training. But an archer can accurately fire 12+ arrows a minute, while a crossbowman would be lucky to get off 2 shots in that time.

Maybe that provides a bit of context for the OP's questions!

 

[Wulf Ratbane]

Some say that all the stopping power of the arrow came from gravity. It was the downwards arc where the arrow gained the most velocity. And even then, normally only after having been fired pretty much straight up.

Some say that folks who say such things really need a remedial physics class.

 

[Kzach]

Maybe that provides a bit of context for the OP's questions!

Thanks!

The idea of it being an exotic weapon is nice. I might use that.

 

[francisca]

There were bows with draw strengths approaching 200lb found on the Mary Rose; there may be no-one alive today capable of pulling those bows.

I wonder if being submerged for 400+ years affected the wood, therefore, changing the draw over time?

 

[HalfOrc HalfBiscuit]

You might want to have a look here:

Longbow-Archers.com/Warbows

and at other pages on that site.

 

[El Mahdi]

I gotta go with S'mon with this. How would you even be able to draw, much less fire a 200 pound draw weight bow? You'd have to be huge to pull that thing. Heck, most compound bows top out at around 100 pounds.

I think you're a bit high on the draw weights.

Because of this:

...medieval archers were trained from a very young age in the use of a bow so that their muscles developed in exactly the right pattern to pull draw weights that would seem obscene by modern standards.

... Englishmen for a time, were actually required to participate in regular archery practice. The place in a village where this occured was called the Butts. A lot of villages still have areas or streets named this even today.

Another interesting thing I read about the Mary Rose was that the skeletons of seasoned veteran longbowmen were DEFORMED! It showed not only abnormal muscle development in the shoulders and arms of the drawing arm, but bony growths and deformed fingers.

And everything Charles Ryan said. He pretty much nailed it.

I'd definitely consider it an exotic weapon also. But I'd make the distinction between basic longbows and "Warbows".

 

[Umbran]

Aren't "momentum" and "energy" the same. Essentially it's just kinetic energy, isn't it?

No, it isn't. It really, really isn't. The two are related to the same quantities, but they aren't the same thing at all. The difference being that in every collision energy is conserved, but the same is not true for momentum.

How much energy is deposited in a target doesn't mean much in and of itself. I can push a refrigerator across the floor, putting a whole lot of energy into it, without damaging it. If I put the same energy into the fridge with a baseball bat, the fridge will be dented. The difference is what a physicist calls "impluse", which is equal to the change in momentum, not in energy.

I'm sorry that plain text does not allow me to write these as clearly as I would like.

If m = mass, and v = speed

Kinetic energy = 0.5 * m * v^2.
Momentum = m * v.

So, let's take some examples (data pulled from the internet - we could quibble about the details, but these are just to get the right order of magnitude.)

Say we have a bullet: m= 0.02 kg, speed = 400 m/s
And an arrow: m = 0.06 kg, speed = 40 m/s

Bullet KE = 1600 J
Arrow KE = 48 J
Clearly, the bullet has higher Kinetic Energy, by a factor of 33 or so.

Bullet Momentum = 8 kgm/s
Arrow Momentum = 2.4 kgm/s
The bullet has higher momentum, but only by a factor of about 3. Far more even footing than on energy.

Here's where the bullet's penetrating power actually works against it. If you're firing a modern gun with a normal bullet against an unarmored target, you *expect* it to come out the other side and keep flying. That means it has momentum left over, that it didn't lose to the target. While a modern arrow might pass clean through, that's the exception, not the rule. It would be even less the rule for a more primitive arrow. It is not so odd to imagine that the bullet hits with *less* impulse than the arrow.

The gun wins not because it is so much more awesome at killing for each individual bullet, but because guns are sooooo much more convenient - you can carry more projectiles, and wing them out faster than any archer ever could, and you can do it effectively with far less training and physical conditioning.

Even a modern compound bow doesn't have the impact of a 200 lb. pull longbow with a heavy war arrow. Even the most powerful compound bows only have pulls in the low to mid 100's.

Respectfully, the 200lb pull longbow was also the exception, not the rule. That's the Dirty Harry .357 Magnum of bows, not the usual .38 special. An old time longbow, in general, was not notably harder pull than today's powerful bows - as you pointed out the difference in today's bows isn't the pull, but in the force needed to hold the bow once you'd drawn it.

 

[Nikosandros]

No, it isn't. It really, really isn't. The two are related to the same quantities, but they aren't the same thing at all. The difference being that in every collision energy is conserved, but the same is not true for momentum.

The opposite is actually true. Momentum is always conserved in a collision, but energy is conserved only in an elastic collision.

 

[Umbran]

The opposite is actually true. Momentum is always conserved in a collision, but energy is conserved only in an elastic collision.

Yeah, I bungled what I was trying to say, there.

However, for these considerations, it is important to note that total energy is always conserved (can neither be created nor destroyed, and all that). The question is whether kinetic energy is conserved.