[Rhodes22-list] Effros' port of sail and da list

[P&M Beals]

Bill, do you sail on LIS?  I just checked Rummy's updated  list and don't
see your name on there...since I have notions of one day sailing or MOTOR
SAILING (scandal) from NJ to LIS I am curious to know where on the map to
place you.. and with the current issues you raise on East River- I know my
father always told me about those currents...I would want my motor to be
well tested and strong, which so far the Yamaha 4 stroke seems to be running
smoothly, strong and start-up reliable.


it is really interesting to see if geography and home location influence the
politics of the email author...not that I have been trying to pinpoint all
of you folks.  in fact lately I have to delete a lot since it takes so much
time to wade through-

Phyllis

> From: "Bill Effros" <bill at effros.com>
> Reply-To: The Rhodes 22 mail list <rhodes22-list at rhodes22.org>
> Date: Fri, 24 Sep 2004 11:10:18 -0400
> To: "The Rhodes 22 mail list" <rhodes22-list at rhodes22.org>
> Subject: Re: [Rhodes22-list]Speed Over Ground
> 
> Michael,
> 
> You know better.
> 
> We were discussing Speed Over Ground.
> 
> If you are in the East River, which has a current that moves in both
> directions at varying speeds up to 6 kts. It is impossible to determine gas
> "mileage" no matter what you do.
> 
> As I've mentioned before, you can go down the East River at 12 kts. (SOG) in
> an R-22.  Many days you can beat the cars down the same run.  It's a thrilling
> ride in every way.  As Peter correctly noted, there can be an incredible about
> of really big traffic in a situation where everyone else has the right of way
> and no one is completely in control of their vessel.
> 
> Granted, this is an extreme example to make the point, but as you know,
> everyone on LIS (and that's a lot of people) faces it every time we move in
> our boats, and it has to be factored into all of our equations.
> 
> Lots of other people face it too--the people on dammed lakes, people on
> rivers, in fact, the Hudson River travels in both directions down here.
> 
> There is no absolute ratio between the amount of power generated by your
> engine, the amount of gas consumed, and the amount of land you can cover in
> your boat at a given speed for a given amount of time.
> 
> Bill
> 
> 
> ----- Original Message -----
> From: Michael Meltzer
> To: Peter Thorn ; The Rhodes 22 mail list
> Sent: Thursday, September 23, 2004 11:44 PM
> Subject: Re: [Rhodes22-list] Re: Pointing
> 
> 
> Come on guys, current is an non-issue in this outboard debate, the motor
> pushes the boat thought the water, it really does not mater
> to the motor or type of motor that the water is also moving, that is how much
> power the motor is producing not how it produces it.
> It like claiming you hate bill new book because the color clashes your suit or
> that you hate it because your wife hits you every
> time you read, come on.
> 
> MJM
> 
> ----- Original Message -----
> From: "Peter Thorn" <pthorn at nc.rr.com>
> To: "The Rhodes 22 mail list" <rhodes22-list at rhodes22.org>
> Sent: Thursday, September 23, 2004 12:11 PM
> Subject: Re: [Rhodes22-list] Re: Pointing
> 
> 
>> Roger,
>> 
>> That was great!  A wonderful, science-filled explanation of  foils, stalling
>> and the technical woes that befall skippers who pinch.   Previously, my
>> knowledge about stalling sails was merely that the outside telltales stopped
>> flowing aft.  Good job.
>> 
>> I'd like to reprint your stalling missive in our sailing club's (Carolina
>> Sailing Club, Raleigh NC) newletter, with proper attribution of course.  OK
>> with you?
>> 
>> In Bill's defense, it's pretty clear to me that you haven't cruised the East
>> River lately.  Motoring back and forth across the current there would be a
>> death defying act, exposing R22 broadsides to harbor tugs with 4' bow waves,
>> full-throttled Egg Harbors and the like. <G>
>> 
>> PT
>> 
>> ----- Original Message -----
>> From: "Roger Pihlaja" <cen09402 at centurytel.net>
>> To: "The Rhodes 22 mail list" <rhodes22-list at rhodes22.org>
>> Sent: Thursday, September 23, 2004 9:25 AM
>> Subject: Re: [Rhodes22-list] Re: Pointing
>> 
>> 
>>> Slim,
>>> 
>>> Actually, all of the foils can stall out, both in the water & in the air.
>>> An object does not have to be a certain shape to generate lift.  To prove
>>> this to yourself, stick your hand out of the car window.  If you hold your
>>> hand at an angle to the air flow, do you feel a force?  That's lift!  Is
>>> your hand shaped like an airfoil?  Even a flat plate can generate lift if
>> it
>>> is held at an angle of attack to the fluid flow.  The fluid does not have
>> to
>>> be a gas, like air, either.  It turns out liquids obey the same laws of
>>> hydrodynamics as gases.  The only differences between gases and liquids
>> show
>>> up in the defining equations as terms for density & viscosity.  Liquids
>> are
>>> usually more dense and more viscous than gases as the same temperature &
>>> pressure.  Without going into the physics, what this means is that dense
>>> liquids will produce the same amount of lift force/unit area at a lower
>>> fluid velocity than gases.  Or alternatively, at the same fluid velocity,
>>> liquids require less surface area to produce a given amount of lift force.
>>> For example, at room temperature & pressure, the density of air is about
>>> 0.076 lb/ft^3 vs. water at about 62.4 lbs/ft^3, a factor of about 800X.
>> So,
>>> the keel only needs to have about 1/800 the surface area of the sails to
>>> generate the lift forces required to resist leeway under sail.  Water is
>>> also much more viscous than air.  This has the effect of making the
>>> underwater foils much more forgiving or less prone to stalling out than
>> the
>>> sails.  This is a good thing because it makes sailing much easier.  If
>> your
>>> underwater foils stalled out as easily as your sails; then, every time the
>>> boat lifted in a wave or every time you moved the rudder blade, these
>> foils
>>> would stall out & quit generating lift.  However, at a sufficiently high
>>> angle of attack, even your underwater foils will stall out & quit
>> generating
>>> lift.  This happens most frequently with the rudder blade.  If we define
>> the
>>> angle between the tiller & the centerline of the boat as the angle of
>> attack
>>> of the rudder blade; then, the rudder blade is starting to stall out at an
>>> angle of about 30 degrees & completely stalled out at an angle of about 45
>>> degrees.  At angles greater than about 45 degrees, the rudder blade
>> behaves
>>> more like a water brake or drag device than an underwater foil.  So,
>> unless
>>> you are trying to slow down the boat, putting the tiller over more than
>>> about 45 degrees off the centerline is counterproductive as far as
>> steering
>>> goes.
>>> 
>>> People cite the analogy of airflow moving faster over the curved surface
>> of
>>> the top of a wing vs., the straight bottom surface as causing a pressure
>>> difference between the top & bottom surfaces & that's what causes lift.
>> In
>>> the middle 1700's, a Swiss mathematician & scientist named Daniel
>> Bernoulli
>>> did a mass & energy balance on all the forms of energy contained within a
>>> moving fluid.  These days, mass & energy balances are fundamental to
>>> engineering calculations.  But, in Bernoulli's time, this was a completely
>>> new & creative approach!  Bernoulli found that, if you keep a running
>> tally
>>> on all the forms of energy in the fluid as it flows from place to place;
>>> then, total energy is conserved.  The energy can change form - i.e.
>> kinetic
>>> energy can be traded off for pressure &/or potential energy & vice versa;
>>> but, the total amount of energy remains constant.  Bernoulli expressed
>> this
>>> idea in the form of an equation that now bears his name.  Bernoulli's
>>> equation is one of the 1st things students learn in any class on fluid
>> flow
>>> or hydrodynamics.  Naval architects, aeronautical engineers, & chemical
>>> engineers have it tattooed on the inside of their eyelids so they see it
>> in
>>> their sleep!  Macroscopically, one of the things Bernoulli's equation
>>> predicts & experimental measurements have verified is that there is a high
>>> pressure region on the windward side of a sail, a low pressure region on
>> the
>>> leeward side of a sail, & greater air velocity on the leeward side vs. the
>>> windward side - hence the common analogy cited above.  The difference
>>> between these two air pressures, multiplied by the surface area of the
>>> sailcloth over which the pressure difference is acting, is a force, which
>> we
>>> call "lift".  Although Bernoulli's equation is correct, it doesn't provide
>>> much insight into what's actually going on, physically.  Physically,
>> what's
>>> actually happening is Newton's Laws of Motion are at work, as always.  The
>>> air flowing over the sail is being forced to change direction by the shape
>>> of the sail.  Since the air has mass & Newton's Laws state that it doesn't
>>> "want" to change direction, forcing the airflow to change direction
>> requires
>>> that work must be done.  The only source of energy available to do this
>> work
>>> is the kinetic energy of the moving air itself, so that's where it must
>> come
>>> from.  Macroscopically, we observe this work as an increase in the air
>>> pressure on the windward side & a decrease in pressure on the leeward side
>>> of the sail.  The speed of the windward side & leeward side airflows
>> adjust
>>> themselves in response to these new pressures.
>>> 
>>> So, what the heck is stalling out?  Well, back to Newton's Laws again.
>>> Remember the fluid flow does not want to change direction.  Forcing the
>>> fluid to change direction too abruptly will cause the more or less orderly
>>> flow of molecules to break down into a more chaotic pattern.  The fluid
>>> molecules sort of get in each other's way when they are forced to change
>>> direction too abruptly & go bouncing off in random directions.  This
>> process
>>> turns the kinetic energy of the fluid flow into random molecular
>> vibrations
>>> or heat.  We call this process "turbulence".  Bernoulli's equation doesn't
>>> "care" what form of energy we convert the fluid's kinetic energy into,
>> heat
>>> is just as good as pressure.  So, at the onset of turbulence or stalling,
>>> the pressure difference across the sail goes away in favor of a slight
>>> temperature increase in the airflow.  Again, this has been verified
>>> experimentally.  Around the turn of the 20th century, a British physicist
>>> named Osborne Reynolds came up with the concept of a dimensionless
>> parameter
>>> which could be used to predict the onset of turbulence under any set of
>>> fluid conditions.  This dimensionless parameter is now called the
>> "Reynold's
>>> Number" in his honor.  (NOTE: In engineering, one of the highest honors is
>>> to have a dimensionless number or fundamental defining equation named
>> after
>>> you!)  The Reynold's Number is given by:
>>> 
>>> Re = (L * V * ro) / mu
>>> 
>>> Where:
>>> Re = Reynold's Number
>>> L = Characteristic Dimension Or Length Of The Flowing System (ft)
>>> V = Fluid Velocity (ft/sec)
>>> ro = Fluid Density (lb/ft^3)
>>> mu = Fluid Viscosity (lb/ft-sec)
>>> 
>>> Note: all the physical parameters that go into this calculation must be in
>>> units that cancel each other out, hence the term "dimensionless number".
>>> For any given physical geometry, there is a certain critical Reynold's
>>> Number above which the fluid tends to become turbulent.  For example, for
>>> fluids flowing in pipes, the L parameter is usually the inside diameter of
>>> the pipe & (Re)critical = about 2100.  Note that the fluid viscosity
>> appears
>>> in the denominator of this equation.  i.e., more viscous fluids like
>> liquids
>>> tend to resist the onset of turbulence better than less viscous fluids
>> like
>>> gases.  Again, this tends to make the underwater foils more resistant to
>>> stalling out than the sails & this is a good thing!
>>> 
>>> There, that's probably more than you ever wanted to know about foils &
>>> stalling out!  hopefully, I answered your question.
>>> 
>>> Roger Pihlaja
>>> S/V Dynamic Equilibrium
>>> 
>>> ----- Original Message -----
>>> From: "Steve Alm" <salm at mn.rr.com>
>>> To: "Rhodes" <rhodes22-list at rhodes22.org>
>>> Sent: Thursday, September 23, 2004 3:26 AM
>>> Subject: [Rhodes22-list] Re: Pointing
>>> 
>>> 
>>>> Peter,
>>>> 
>>>> Hold on, thar!  "Lift" from the keel, CB and rudder?  The underwater
>>>> appendages are symmetrical with the hull and cannot provide any lift.
>>> They
>>>> only serve to prevent lee way, or to provide lateral resistance.  That
>>> part
>>>> I agree with.  Brad might have a better description, but lift happens
>> when
>>>> air (or presumably water) has to travel farther around one side than the
>>>> other, creating a difference in pressure between the two sides.  Lift is
>>>> created by the curved shape of the sail or airplane wing and will stall
>> if
>>>> not going fast enough.  The keel, CB and rudder do not have that kind of
>>>> shape.  I'm with you on the rest as far as pinching vs. pointing goes,
>> but
>>>> it's the sails that stall out, not the keel, CB or rudder.
>>>> 
>>>> Slim
>>>> 
>>>> On 9/22/04 7:58 PM, "Peter Thorn" <pthorn at nc.rr.com> wrote:
>>>> 
>>>>> Hello Ed,
>>>>> 
>>>>> If you verify that you're able to point your R22 35 degrees off the
>> true
>>>>> wind, I certainly would like to visit Lake Hartwell to see that.
>>> Perhaps
>>>>> it's the apparent wind, the combination of the boat's velocity across
>>> the
>>>>> bottom combined with the true wind direction, that's making you think
>>> you're
>>>>> pointing so close. On a reasonably fast boat like R22, the apparent
>> wind
>>>>> angle can move quite a bit forward.  In an extreme example such as
>>> iceboats
>>>>> (that travel many times the true windspeed) the wind indicator points
>>> almost
>>>>> straight forward.
>>>>> 
>>>>> Are your headsail sheets led to tracks at the foot of the cabinhouse
>>> roof?
>>>>> That, I think, would certainly improve pointing.
>>>>> 
>>>>> It's good to be aware of the difference between pointing and pinching.
>>>>> Sailing too close to the wind can cause the underwater foils to slow
>>> down
>>>>> then stall.  That's pinching.  When the keel, cb and rudder stop
>>> producing
>>>>> lift, the boat will start to produce a lot of leeway, or sideways
>> drift.
>>> It
>>>>> is very difficult to detect leeway when aboard the boat that's making
>>> all
>>>>> the leeway.  The bow points higher, so the skipper might think he's
>>> pointing
>>>>> pretty high because the sideslip is so hard to feel.  To avoid this
>>>>> condition, foot off and keep the boat moving.  After regaining speed,
>>> head
>>>>> up a little.
>>>>> 
>>>>> If you have a GPS you can verify your pointing angle by measuring your
>>>>> heading (not the direction the bow is pointing), tack to the other
>> tack,
>>>>> measure heading again and divide the angle difference by 2.  I think
>>> someone
>>>>> mentioned this not too long ago on the list.
>>>>> 
>>>>> I too have wondered about the diamond board, and would guess Phil
>> Rhodes
>>>>> original cb is pretty hard to improve on.   A while back Roger wrote a
>>> very
>>>>> scientific sounding comparison, do you recall that?
>>>>> 
>>>>> Perhaps you Lake Hartwell guys should conduct on-the-water pointing
>>> trials
>>>>> and settle the issue.
>>>>> 
>>>>> PT
>>>> 
>>>> __________________________________________________
>>>> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>>>> 
>>>> 
>>> 
>>> 
>>> __________________________________________________
>>> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>> 
>> __________________________________________________
>> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>> 
> 
> __________________________________________________
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