Calculations: why tie-down strap tension and angle impacts load stability

A strap tensioned to 150 lbs. in position B results in a lateral force of 63 lbs. A strap tensioned to 150 lbs. in position c results in a lateral force of 106 lbs. This creates an imbalance of 43 lbs. (106 lbs. –63 lbs.)

In order to equalize the lateral forces you can either increase the tension in B or decrease the tension in C.

If you choose to increase the tension in B you will need to increase the resulting lateral force by 43 lbs. to 106 lbs.

• 106 lbs. = cos 65 deg. x ? lbs. or
• ? lbs. = 106 lbs/cos 65 deg. or
• ? Lbs. = 251 lbs.

You will need the increase the strap tension from 150 lbs. to 251 lbs. This would also increase the down force to 227 lbs. (251 lbs. x sin 65 deg. = 227 lbs.)

If you choose to decrease the tension in C you will need to decrease the resulting lateral force by 43 lbs. to 63 lbs.

• 63 lbs. = cos 45 deg. x ? lbs. or
• ? lbs. = 63 lbs/cos 45 deg. or
• ? Lbs. = 89 lbs.

You will need the decrease the strap tension from 150 lbs. to 89 lbs. This would also decrease the down force to 63 lbs. (89 lbs. x sin 45 deg. = 63 lbs.)

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