Jeff wrote:
I've been thinking about this - since I did give the guy a rough time -
So just how much acceleration is a "Panic Stop"? Did the mast have to
be "encased in concrete" as he said?
No, just tied down securely enough that if it came loose, it was because
either the tie-down broke (not chafed through, that would again be
carelessness on his part) or whatever it was tied to broke.
This is not very scientific, but it's a good working standard.
The braking distance, according to
http://www.ortrucking.org/stopping.htm
from 65 MPH is 245 feet for cars, 454 for trucks, not counting reaction
time. To decelerate at the force of gravity (one "G" or 32 feet per
second squared), the stopping distance would be under 150 feet, so a
truck is nowhere close to that.
Hmm... I've been under the impression that car stops can approach 1 G...
certainly the momentary accelerations due to road bumps can often exceed
1 G...
For a report on actual panic stop
decelerations and other tests using police cars, see:
http://www.nlectc.org/pdffiles/tirerprt.pdf
Cool... a road test report in a sailing thread! The results are obvious:
1- the police don't exactly drive sports cars
2- the Caprice can outhandle the Crown Vic (duh)
3- get Firestone Firehawk tires
Since the boat generally has a vertical force equal to one G, and the
force of deceleration is somewhat less than that, then net force in a
panic stop is similar to being at rest at a 30 degree incline, though
stronger, maybe by 20 or 30%. (Even at one G, it would be only 40%
stronger than being at a 45 degree incline.) Clearly, anything not tied
down could slide around, but there is no reason for the mast to move, or
even for the bracket to break.
Agreed.
An other way of looking at this is that when the mast is hoisted, it
will have a force on its axis easily double that of a "panic stop."
Would a slippage of 2 feet be acceptable during that maneuver?
Its pretty clear that the mast slippage was the fault of the
preparation, not a panic stop. The bracket is a little harder to
determine - It shouldn't break from a panic stop, but it could have been
from normal bumps, or previous damage, or both. But again not the fault
of the trucker.
I trailered a small boat with an outboard motor on a transom bracket...
but that particular bracket was *very* sturdy, was not the usual wimpy
'tilt-up' type bracket which is totally unsuitable for supporting a
motor while jouncing down the highway. And even at that, when trailering
long distances, I took the motor off and secured it *securely* somewhere
else.
I wonder if the guy bothered to drain his tanks, remove his batteries,
etc etc... all the other normal precautions for trucking a boat? Maybe
an instructional thread would be 'How To Prepare A Boat For Transport By
Truck' since a number of people seem to be doing that these days?
Fresh Breezes- Doug King