Dhaeron,
Welcome to the conversation. The primary point of bumping this thread is to remind Lingchih that he can never live down starting it.
But I have some rebuttals for you
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The big problem with using a strong bow is not so much aiming (which works very well) or learning how to use it, but to build up the muscles needed to use it.
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I don't agree with this. I shoot archery maybe 10 times a year. And I shoot a 55 lb recurve bow. It was my first bow and I've had it for 25 years. I can't shoot all day, but I can easily shoot 40 arrows which is a pretty big bunch for any quiver. And I'm a desk jockey. So it's not like I work out regularly or do anything in particular to pump my strength. I am strong and big, but it's all just native ability.
If I was a peasant forking hay onto wagons I would easily be able to shoot a 100 lb bow. Forking hay onto wagons is an over the head move. Also using a scythe builds massive arm and shoulder muscles. I used to be able to place a 60 lb hay bale onto a wagon above my head using a fork. A fork of hay is not light. Do that all day and you'd find drawing a big bow easy.
We all tend to forget that medieval peasants worked all day at hard physical labour. It's unrealistic to compare them to modern couch potatoes.
The mongols shot 150lb composite bows from horseback.
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Another fun fact is that medieval and ancient crossbows (the greeks already used them) reached mostly the same projectile velocity as bows, mostly because that's limited more by the materials available for the arrows & bolts, than by the materials available for the bows & crossbows
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This is incorrect. The physics of the problem are reasonably simple. It's conservation of energy. The archer puts the integral of force times draw into the bow as energy (or the work done by the archer). If we want a simple calculation, using 100 lbs force for 28 inches (assuming a straight line force curve from zero to 100 lb on a longbow) the energy put into the missile is exactly 159 J or 0.15 BTU. I have converted to SI for the calculations.
Assuming 100% efficiency the missile when fired will have exactly 159 J of energy since energy is conserved. This does not account for energy lost as heat and sound in the string and bow but will be good enough for our calculation. The kinetic energy of the missile is then mass time velocity squared. I found some modern replica arrow heads online that mass about 2 oz each. Add that to the mass of a 1/4" diameter by 36" long cedar arrow (the material I use) we get a total mass of 0.54 oz. The velocity of the arrow is then 333 ft per second.
Let's now try this with a simple goat's foot type crossbow with perhaps a draw of 200 lbs. The draw length of a goat's foot crossbow is about 12 inches. Assuming the same type of force curve we get a input energy of. If the bolt is made of cedar as well with a similar point, it's mass is now 0.27 oz. The bolt velocity is 436 feet per second.
So basically, the velocity of a missile fired from any type of bow is a function of the input energy and mass of the missile. There is no direct comparison possible between crossbows and bows. It's all variable.
This is also why the material of the bow is irrelevant to the discussion. For what it matters, the bow could be made of adamantium or kevlar. The input energy doesn't change since it comes from the human archer. And a human archer has a very strict limit on the energy available. Crossbows can put potentially more energy into the missile because they over come the limits of human power by mechanical leverage. The trade off is loading time.
Of course, someone will argue that the bolt could be made of steel. And it could but then carrying them would be difficult. If we change the bolt shaft to steel the bolts weigh 4 oz each and then 40 bolts would weigh 10 lbs. Pretty heavy but I suppose not impossible. The worst problem is that the velocity drops to 113 feet per second which is so slow that you could simply step out of the way and the ballistics are such that range would deteriorate.
Summary
It is a standard rule of thermodynamic analysis in energy conversion that finding the output from a certain input you do not require to know anything about the internal workings of the energy conversion machine. A simple efficiency rating (to account for losses) is adequate. In the case of bows, they convert human force and distance into kinetic energy. On this basis, the materials, shape, construction, etc are irrelevant. All that matters is the input energy and the efficiency of conversion.
As far as output energy, a crossbow simply does one thing. It increases the energy input by allowing more time for the human to apply the energy. Whether it's simply a goat's foot, windlass or lever action, the job of a crossbow is to mechanically leverage the force of a human. And it takes more time to do so.
I can keep going, but let's see if anyone has the knowledge to try to refute my facts. So far, 80% of this discussion is simply annecdotes and opinion. It's very shy on fact.
For anyone interested, I can share my calculation pages by irc or here.
Re: Crossbows vs. Longbows
But yes, in a base game it's considered there are no light field pieces and heavy ones aren't really transportable - which was the case for most parts of history.
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