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    Slip answers
    From: Doug Royer
    Date: 2003 Apr 24, 17:07 -0700

    Mr. Huxtable, I'll try to answer your questions to the best of my ability.I
    like it when you degress.I enjoy reading all your posts.I've learned quite a
    deal from you and all so far.
    I don't make the rules of the exams.I was told these are the conditions that
    the U.S.C.G. set.It's a government organization,so they have their rules.I
    do know that in the states the timed mile markers that are along shore for
    checking speed are in statute miles and that is what the examiner was
    looking for.I calculated 351.7 mi.(nautical mi.)and got it wrong.That's all
    I can tall you on that.
    No,taffrail logs are not used.It's not common to drag anything off the stern
    unless it's a tow.There are more suffisticated pieces of equipement used
    today.The revs. are feed into the Inertial Nav. System along with other data
    for positioning.
    I know what you're saying about true(observed)slip.That is where the mile
    markers come into play.You get your observed speed by useing them.Slip is a
    factor to be concidered.It is used mainly for calculations of advances and
    fuel consumption(mainly fuel consuption as crude was around $37.00 a barrel
    and if you burn 3 barrels every 15 minutes you can see the cost.).At best it
    is an approximation as I stated.Yes when speed changes slip will also.What I
    should have said is at the start of the leg the speed and distance of the
    vessel is calculated with slip factored to give a "better" future pos.This
    is only a tool used as a check against other calculations or equipement.Out
    there you are useing every tool you have to keep on top of ever changeing
    conditions.Heavy weather is a factor.When it can't be avoided you slow down
    and everything has to be recalculated.In a 6 hr. watch period I can go
    through 15-50 sets of calculations because of changeing conditions.Mr.
    Huxtable, everything you asked in paragraph 5 has and is taken into account
    to the best ability.If a vessel is laden slightly more in the bow or side
    that must be taken into consideration.I hope I answered some of your
    questions.Remember,though,that all of these calculations out at sea when
    underway are only approximations.Everything is done as carefully as possible
    but are still approximations.The electronics are much more precice and
    quicker.The best I can say is the calculations made are checks.I took my
    training and instruction at face value and never really questioned or
    thought about it.I do know it all works.

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