Hijack/sidebar:
If I have a vehicle on a 100 foot rope, being towed at 60 mph.
I put a pull scale on it, and it reads 100 lbs.
How do I translate that into HP required? ie - 100 lbs of drag at 60 mph is ? HP.
Too slow typing if a tortise can beat me
will leave it here anyway
1hp = 33,000 foot-pounds per minute.
60mph = 5,280 feet per minute
Multiply that by your 100 lbs measured pull = 528,000 foot-pounds per minute.
Divide that by 33,000 = 16hp.
If you want to get a reasonable measurement of your frontal area cut out a square the size of the units you want to work in i.e. a square foot if imperial or 10cm square if metric.
Stand it next to your vehicle and take a front on picture from a reasonable distance with a long focal length lens.
Rule up the picture with a grid the size of your square cutout and count the full and partial squares and that's your frontal area.
Cheers
Jon