# Thread: Hitchcraft for hammock tensioning

1. ## engineering math

Originally Posted by hitchman
Here is my math: Sin of 30 is 0.5, meaning that for a 30 degree angle the vertical component is half of the tension on the rope. Each end carries half of the weight. So for a 200 lb weight, or any weight for that matter, the rope tension on each end is the same as the weight (multiplied by 0.5 and divided by 2).
W = weight

W*0.5/2 = W/4

not W.
??

The thing to worry about is dynamic tension, not static, me thinks. Getting mass times acceleration involved, and all that.

Grizz

2. The 0.5 factor is multiplied not divided. The tension on the rope is the resultant from the vertical component (weight) and the horizontal component (pulling the trees together). So at 30 deg the tension on the rope is twice the vertical load (half the weight on each end).
I wouldn't think the dynamic component is that great unless you are in earthquake country. Otherwise let me point out that the rope is rated at the breaking point (for new undamaged rope). Rope accessories are generally rated at the recommended work load, which is around 1/3 of the breaking load.

3. I hate math.

4. Math is hard.

I have that on a t-shirt...nobody gets the joke, though

5. ## fun with figures

There are two kinds of math : easy math, and hard math.
Easy math is the kind you understand, hard math is the kind you don't.

Also a joke that most don't get, or at least don't think is funny.

I've got a degree in the stuff, my wife's joke is that I double majored in math, and more math. However my courses ran to the crystal tower variety, and not the useful stuff like elementary engineering.

Not to belabor the point, but if you take half the weight (W/2) and if
The 0.5 factor is multiplied not divided
then that's (W/2)*0.5. But these are just words...I now understand the physics of the situation by your description
The tension on the rope is the resultant from the vertical component (weight) and the horizontal component (pulling the trees together).
So I gather that the way to think about this is that the known force is W/2, understood to be the vertical projection of the (unknown) total force T on the rope. The ratio of the vertical projection to the total component (hypotenus) is the sine of the angle theta between the hypotenus and adjacent side, so sine(theta) = (W/2)/T. With sine( pi/6 ) = 0.5 we solve for T in 0.5 = (W/2)/T, which is T = (W/2)/0.5 = W.

When you say that the 0.5 factor is multiplied and not divided, I guess you mean 0.5*T = (W/2).

so all is clear now.

Grizz the occasionally obtuse

6. Couldn't have put it better myself!

There are two kinds of math : easy math, and hard math.
Easy math is the kind you understand, hard math is the kind you don't.
I personally always thought 'hard math' was the kind that Newton, Bernoulli, Leibniz, Euclid, and Einstein struggled with.

so all is clear now.
Yes, the outlined principle is clear enough. It doesn't make me any less inclined to want my hammock ridiculously over-engineered, though. My backside, and my ego, don't like taking falls.

8. For those of you who do math so well, I have but one thing to say. I hate you. Just kidding, thanks for the science to back up the hanging, I appreciate it.

There are two kinds of math : easy math, and hard math.
Easy math is the kind you understand, hard math is the kind you don't.

Also a joke that most don't get, or at least don't think is funny.

I've got a degree in the stuff, my wife's joke is that I double majored in math, and more math. However my courses ran to the crystal tower variety, and not the useful stuff like elementary engineering.

Not to belabor the point, but if you take half the weight (W/2) and if

then that's (W/2)*0.5. But these are just words...I now understand the physics of the situation by your description

So I gather that the way to think about this is that the known force is W/2, understood to be the vertical projection of the (unknown) total force T on the rope. The ratio of the vertical projection to the total component (hypotenus) is the sine of the angle theta between the hypotenus and adjacent side, so sine(theta) = (W/2)/T. With sine( pi/6 ) = 0.5 we solve for T in 0.5 = (W/2)/T, which is T = (W/2)/0.5 = W.

When you say that the 0.5 factor is multiplied and not divided, I guess you mean 0.5*T = (W/2).

so all is clear now.

Grizz the occasionally obtuse
Hey now show some respect.

Hitchman, you have a good looking product. I broke and got dropped using 550 lbs rated paracord. It broke in the middle and not at the knot. It was at a decent angle, 30-45 deg. For me it is nothing rating below 1000lbs.

10. "multiplied by 0.5" = "divided by 2"
Maybe the confusion was stating the same thing two different ways.

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