Categories
Phillosoph

My Left Pocket.

A common piece of advice is to re-lace your boots with paracord. The more thoughtful of you may have wondered about the wisdom of being in a survival situation with unlaced boots! What is usually omitted is that in an emergency you are supposed to take the cores out of the cord, then re-lace your boots with the empty outer or some of the core cords. This assumes you did not buy the budget cord that doesn’t have particularly good cores!
Re-lacing your boots with paracord isn’t a bad idea. It cannot hurt. One day you may find yourself cold, tired and wet, your numb hands trying to unlace your boots, gut the paracord and then re-lace your boots. That sounds like something you may want to avoid if possible!
In my post on an EDC shopping list I suggested you add about two metres/ a fathom/ an armspan of paracord to your everyday carry (EDC). Or a pair of long, strong bootlaces, whichever you can acquire more easily. The utility of this was expanded on in one of the links from my 4-4-4-4 article. In the event you missed it:

I had a quick look in the left front pocket of my trousers. The contents were:
  • One bandanna, various uses.
  • Disposable lighter, for emergencies.
  • A hank of paracord, roughly two metres.
  • A actual length of shoelace. I tend to pick up potentially useful bits of cordage! Useful for stuff that does not require the paracord.
  • A tubular spectacle safety cord. My habit of acquiring cordage paid off here. What I thought was a bit of shoelace turned out to be something very useful to me. If the situation requires, I can retrieve this from my pocket and add it to my glasses.
  • A couple of metres of cotton string. Saves the paracord for important jobs. Potentially could be used as tinder. 
Categories
Phillosoph

Arrows: Time of Flight and Momentum.

Many thanks to Ric Morgan for his donation to support the blog.
Recently I got to thinking about archery. In particular, I was curious about the time of flight of arrows and quarrels. This seemed quite a practical thing to know. I was a little surprised at how little information on this could be found on the internet.
Most modern archers are target shooters, so not particularly interested in how long the arrow takes to reach a static target. They also shoot at ranges that provide very little insight into, say, bows being used on medieval battlefields. If you play role-play games arrows probably hit in the same turn, which may be the same second, of firing. You would think there was considerable discussion of flight times among bowhunters, but not according to my search engine.
One target site did inform me:
“Recurve bow arrows can travel up to 225 feet per second (fps) or 150mph while compound bow arrows can travel up to 300fps (200mph). Longbow arrows travel slower due to the weight of the arrows. Even at 300fps, it takes around a second to reach a 90 metre target. You hear your release first followed by the thud of the arrow hitting the target a second later (you can’t see it unless you use a telescopic sight).”
More trawling found me this article, with the following table:

I also remembered an old book I had, which gives the following table:

90m in the first second sounds like a good rule of thumb, although I would like to know how this changes beyond this range. 
Why does it matter? If in an emergency situation a bow may be one of your options for defence or food gathering. Much of this will also apply to other hand-thrown missiles such as spears or rocks. Contrary to what you see in action movies, bows are not “silent killers”. Some of the energy stored up in a drawn bow is released as sound. Your arrow will travel at 100-200 fps, while sound travels at about 1,100 fps. The animal you are shooting at will hear you before the arrow arrives. Many animals survive by being paranoid, so there is a good chance it will begin moving before your arrow arrives. Thus, you need to lead your target. For this, you need to know time of flight. Calculating lead and other parameters is covered in my book on survival weapons.
While there was very little discussion of time of flight, it seemed initial velocity and kinetic energy seemed to be of great interest to bowhunters.
The V0 of a bow is the equivalent of the muzzle velocity of a gun. Most bows don’t have muzzles. Arrows lose energy at a pretty steep rate. One of the above sites uses a working figure of 3% per 10 yards. This means that the terminal velocity of an arrow is going to be very different from the V0. Failing a really strong tailwind, V0 is the one velocity your arrow will not be at!
As discussed elsewhere, kinetic energy is something of a red herring when predicting bullet performance. It is popular in the gun press. It is far more impressive to say a round has 2,352 ft/lbs of energy than that it has 1.7 ftlb/sec of momentum!
Terminal performance of arrows is somewhat easier to estimate than for bullets. Arrows mainly rely on cutting to produce blood loss. Given similar size and configuration of arrow heads it seems reasonable that the more effective arrow will be that that penetrates more. Just for fun I ran some figures using the following formulae:

Energy (ftlbs) = [(Velocity (fps))2 x Weight (grains)] ÷ 450,240

Momentum (ftlbs/sec) = Weight (grains) x Velocity (fps) ÷ 225218

From the above chart I selected a 450gr arrow at 130 fps and compared it to a 350gr arrow at 147.4 fps. These would both have a kinetic energy of about 16.89ftlbs. Since weight is different, so will momentum be. The heavier arrow is at 0.2597ftlb/sec while the lighter is 0.225 ftlb/sec. That is about 15% difference. One would expect the arrow with more momentum to penetrate more due to its higher inertia, but would the difference be significant in real world applications? Something to think on.
Categories
Phillosoph

Lock Picks from Soldier’s Handbook.

Long ago, before we had the internet, one of the books talked about in certain circles was “The Soldier’s Handbook” by Anthony B. Herbert. This included information on how to make lock picks! It also came with a hefty price tag, so only serious/rich readers could dream of obtaining a copy. Wealthy people never misuse information, of course.
The Soldier’s Handbook has some interesting sections, but in retrospect I am glad I never tried to make lockpicks from the designs given. Here is a scan of the relevant page. Looks like a batarang, a half-ball, half-snowman, a full diamond and what look more like dental tools. I would not have gotten far! The instructions on how to use lock picks, and other entry techniques are not that bad, in fairness.

How lucky we are now! There are plenty of good sources of information on how to use lock picks, including, I hope, this blog. Companies such as UKBumpkeys and WithoutAKey offer good quality picks at reasonable prices. And if you are really on a budget there are Chinese-made sets from companies such as Goso and Klom. Not so nice but they are good for learning.