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Post by Deleted on Jan 8, 2017 9:27:09 GMT
If a 40hp engine can propel a boat at 6mph that is 30kW and 2.7 metres per second.
Energy is force x distance. Power is force x speed.
In SI units 30kW is 30,000 Watts; a Watt is 1 Nm/s. There are 9.81 Newtons to a kg.
30,000/2.7/9.81 = 1,500 kg = one-and-a-half tonnes of push. So this would be about the force needed to restrain a boat in a 6 mph current.
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Post by JohnV on Jan 8, 2017 11:00:02 GMT
If a 40hp engine can propel a boat at 6mph that is 30kW and 2.7 metres per second. Energy is force x distance. Power is force x speed. In SI units 30kW is 30,000 Watts; a Watt is 1 Nm/s. There are 9.81 Newtons to a kg. 30,000/2.7/9.81 = 1,500 kg = one-and-a-half tonnes of push. So this would be about the force needed to restrain a boat in a 6 mph current. Interesting !!! Just a thought though, that 30Kw, is the maximum generated power, the actual applied power would be considerably less due to losses in the conversion of the engine power into thrust. I do not know the efficiencies for a propeller driven narrow boat, but I would consider it to be probably very low, thus greatly reducing the requirements of an anchor.
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Post by Deleted on Jan 8, 2017 11:34:47 GMT
Well, it was a 'ball-park' estimate! But it gives an idea. Can't really be more though, so useful in that regard.
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Post by JohnV on Jan 8, 2017 13:02:20 GMT
Well, it was a 'ball-park' estimate! But it gives an idea. Can't really be more though, so useful in that regard. As I said "Interesting" As you say, it gives a useful starting point
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Post by Gone on Jan 8, 2017 15:50:09 GMT
Do keep up at the back, he's not ginger, he's "fire engine blonde". Either way he doesn't strike me as a Twat. High praise indeed!!!!
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Post by Gone on Jan 8, 2017 16:00:56 GMT
If a 40hp engine can propel a boat at 6mph that is 30kW and 2.7 metres per second. Energy is force x distance. Power is force x speed. In SI units 30kW is 30,000 Watts; a Watt is 1 Nm/s. There are 9.81 Newtons to a kg. 30,000/2.7/9.81 = 1,500 kg = one-and-a-half tonnes of push. So this would be about the force needed to restrain a boat in a 6 mph current. "How big an anchor" is one of those interesting puzzles. If you want to stop your boat on a River in flood conditions (say a 6mph flow) then you will need a big anchor, probably bigger than you can safely handle. However I would not attempt to go upstream in a 6mph flow as at wide open throttle I would end up with a ground speed of about 0.5mph whilst using about 8 to 10 litres per hour of diesel. Therefore I would stay moored up until the flow dropped to less than 4mph. I suspect the River Seven would be closed at a flow of 6mph, though that is a guess. So as to anchor size, it is dependant upon the fastest flow you would venture out on, or indeed when CRT open the locks on the river. For those reasons I choose a 14kg Danforth.
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