Gav
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| posted on 19/3/09 at 10:03 AM |
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Turning moments?
My boss asked a question about his boat and i got a bit stumped.
His boat is on land at the moment, it has a mast of 40ft with a 1ft width.
if a 50mph hits the mast, what would be the torque applied at the keel?
I tried to simplfy it bit applying x lbs at 40ft but i really dont know how to work out the force actually hitting the mast, and obivously it would
apply different forces all the way along the mast.
[Edited on 19/3/09 by Gav]
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oldtimer
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| posted on 19/3/09 at 10:07 AM |
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Sorry I can't help with the calcs bit 1 foot width on a 40ft mast seems excessive - are you sure that's right? Windage on the hull is
usually a bigger factor, especially on modern yachts with their high freeboard.
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Gav
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| posted on 19/3/09 at 10:09 AM |
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Yep those were the figures he gave me.
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mcerd1
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| posted on 19/3/09 at 10:31 AM |
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effective wind speed = 50mph = 22.352 m/s
40ft *1ft = 12.192 * 0.3048 = 3.716m^2
dynamic wind preasure = .613 * V^2 = 0.613 * 22.352 * 22.352 = 306
net preasure coefficent: = 1.2 (for circular profiles)
>> net surface pressure = 0.61kN /m^2
>> 3.716 * 0.61 = 2.267kN applied at half height
>> 2.267 * (12.192 / 2) = 13.819kNm (or 509.6 * 20 = 10192 ft lb)
does that look right ? (I've not allowed anything for a head wind)
[Edited on 19/3/09 by mcerd1]
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Gav
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| posted on 19/3/09 at 10:52 AM |
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WEll my boss found a website where you can jsut put in the values and it tells you how much force is being applied and at the end it says just forget
this and hope it dosnt fall over 
The total force applied to the hull and mast was something like 1800lbs
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loggyboy
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| posted on 19/3/09 at 02:58 PM |
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is the mast 1ft dia all they way up or just at the base with it thining as it goes up?
Mistral Motorsport
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owelly
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| posted on 19/3/09 at 03:02 PM |
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What you're getting with those calcs is the turning force at the base of the mast. Does the mast length stop at the deck? How far is the keel
from the base of the mast?
http://www.ppcmag.co.uk
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Gav
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| posted on 19/3/09 at 03:29 PM |
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No idea, dont worry chaps the boss got his answer from the other site
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