[Rhodes22-list] Combination Of Sharp Turn To Port + Single
Handed Docking
Steve Alm
salm@mn.rr.com
Mon, 13 Jan 2003 16:56:29 -0600
David,
Some one here on the list (I forgot who) posted this idea: Create a sort of
safety net at your slip for when you're coming in too fast. Fix a permanent
line from the left front corner of your slip to the right side of the slip
about half a boat length back. Then another line just the opposite, from
the right front corner to the left side. This makes the lines cross and
form a "V" several feet out from the middle of your finger peer in your
slip. Then you can come in a little faster (without losing steerage) and
use the "V" to "catch" you and stop you from hitting the dock.
Slim
On 1/13/03 7:44 AM, "Roger Pihlaja" <cen09402@centurytel.net> wrote:
> David,
>
> I pasted your questions in below & added my comments:
>
> "Interestingly, much larger sailboats in the larger slips opposite me (the
> ones I back toward as I back out of my slip) seem to have no problem, at
> least when I seen them come and go on normal days. One skipper with two
> small sons repeatedly brings his 35-foot sailboat to a dead stop centered in
> his slip with no lines whatsoever. The only differences I can see are:"
>
> "(i)they are headed towards a larger opening"
>
> The degree of difficulty (DoD) of entering a given slip can be thought of in
> terms of the ratio of the
> slip width/max boat beam. If your slip is only 10' wide & your R-22 has an
> 8' beam; then, your
> DoD = 10/8 = 1.25 That 35' LOA sailboat probably has a 12' beam. If his
> slip is 50% wider than yours,
> or 15'; then your friend faces a challenge of: DoD = 15/12 = 1.25 or
> proportionately the same as you. On the Great Lakes, where boats tend to be
> larger, slips in recreational marinas are rarely more than 20' wide. I know
> this max slip dimension from sailing on my friend's 42' sailing catamaran,
> which has a 23' beam - we anchor out a lot. But, on a small inland lake
> like yours, a 15' wide slip wouldn't surprise me, especially if the rest of
> the marina is laid out small & cramped as per your description.
>
> "(ii) they are turning to starboard, if that makes any difference--is that
> what people talk about when they refer
> to a right-hand prop?"
>
> Prop side thrust or "prop walk" is caused because the prop is operating in
> water that is less dense on the top of the prop vs. the bottom of the prop
> because of the weight of the water above the prop. A right handed prop has
> the blades arranged such that; when viewed from astern, the prop rotates
> clockwise when generating forward thrust. The density difference of the
> water across the vertical diameter of the prop causes a side thrust to be
> created. In the case of a right handed prop, this side thrust is directed
> to starboard. A side thrust to starboard at the stern of the boat causes
> the stern of the boat to be pushed to starboard. Pushing the stern to
> starboard causes the boat to rotate about its CR in a counterclockwise
> direction - in other words it turns to port. Large diameter, slow turning
> props tend to produce proportionately more side thrust vs. small diameter,
> fast turning props. For a left handed prop, all of the above arguments are
> reversed. In reverse gear, the right handed prop turns counterclockwise,
> the stern of the boat is pushed to port, & the boat tends to turn to
> starboard.
>
> "(iii) their prop is inboard and at the centerline of their boat, giving
> better steering control."
>
> On an R-22, having the prop mounted to port of the boat's centerline
> generates a torque about the CR in forward gear that tends to rotate the
> boat in a clockwise direction. In other words, in forward gear, the port
> offset location of the prop tends to make the boat turn to starboard. In
> reverse gear, the offset thrust tends to make the boat turn to port. Note
> that this has nothing to do with whether the prop is right handed or left
> handed. This phenomenon is simply a side-effect of mounting the prop off
> the boat's centerline.
>
> So why is it so hard to turn sharply to port with a strong wind from astern?
> Well, the hull presents much less surface area to the wind when it is
> oriented stern-on vs. side-on to the wind. So, energy is required to turn
> the hull from stern to the wind around to side to the wind. Energy is also
> required to hold the hull in the side to the wind orientation as the wind
> tends to rotate the hull back to the stern to the wind orientation. Where
> does this energy come from? There are two potential sources, the kinetic
> energy of the boat itself & from the motor. In a crowded marina situation,
> the boat is going to be moving slowly. So, you don't have very much kinetic
> energy to start off with. But, suppose you start the turn anyway? As the
> boat turns, the viscous drag of the hull in the water + the windage work
> together to use up your kinetic energy. You will likely end up turned
> side-to-the-wind, but stopped dead in the water. When the water stops
> flowing across the rudder blade, it stops generating any steering forces.
> The wind keeps blowing. The boat is blown out of control back downwind &
> tends to rotate back to the stern-to-the-wind orientation! So far, these
> effects are pretty much the same for a port or a starboard turn. OK,
> suppose we add some power from the port offset mounted prop? In forward
> gear, even with the motor turned full lock to help the port turn, a
> substantial fraction of the thrust is acting against the turn. This is the
> difference between a port turn & a starboard turn. You can't use too much
> throttle because a substantial fraction of the thrust is also pushing the
> boat forward. Using too much throttle will result in the boat finishing the
> turn & entering the slip going much too fast. Now, when you put the engine
> into reverse & apply full throttle to stop, the prop side thrust tries to
> turn you back in the direction you came from. Arggg! Overall, this
> technique simply has everything working against it. It's a delicate
> balancing act that requires good eye/hand coordination & a good sense of
> speed & distance all performed in real time under stress with dire
> consequences for failure!
>
> But, if we put the engine into reverse, turn it to full lock in the opposite
> direction, & now apply full throttle; everything is different. With reverse
> thrust, the port offset engine location is tending to assist a port turn.
> Full reverse throttle will tend to slow the boat down, not speed it up. So,
> you get up a good velocity before starting the turn, use the reverse engine
> thrust to spin you around + burn off your speed. With a little practice,
> you will find you can pull a sharp 90 deg turn to port, finishing the turn
> with the bow at the entrance to your slip, with the boat moving slowly
> forward at just the right speed for docking. Then, you shift into neutral,
> slip your single dock line over a piling or cleat, stop parallel to the
> dock, quickly attach your bow line, & then your stern line. Then, briefly
> stop to acknowledge the applause from your fellow boaters! I know this
> technique sounds radical, but I guarantee it really really works.
>
> Roger Pihlaja
> S/V Dynamic Equilibrium
>
> ----- Original Message -----
> From: "David Keyes" <dkeyes@houston.rr.com>
> To: "The Rhodes 22 mail list" <rhodes22-list@rhodes22.org>
> Sent: Sunday, January 12, 2003 12:35 PM
> Subject: Re: [Rhodes22-list] Combination Of Sharp Turn To Port +
> SingleHandedDocking
>
>
>> Roger, I will try your single dock line. But the challenge with a brisk
>> wind astern has been even to get that far (to where one is entering the
> slip
>> between the finger piers), where you could get to the dock line. I have
> to
>> think about coming in close on my port side to the sterns of the upwind,
>> docked boats just before my slip and fetching the dock line for a pivot
> into
>> the dock, but this couldn't work single-handed due to the protruding
>> outboard motors of the other boats. I have been coming down the "alley"
>> between the adjacent piers with my boat about 2/3 to 3/4 of the way
> towards
>> the opposite pier to allow for turning room but without my stern getting
> too
>> close the the sterns of the boats to starboard as I make my turn to port.
>>
>> As to your question: Of course the wind is not always that strong. I
> have
>> since found out, talking to the marina personnel and some other boat
> owners,
>> that (virtually) no one goes out on days where there is a strong onshore
>> wind (northerly wind--we are on a southern shore), which would be rare in
>> the summer but is common in the winter. They don't go out because of the
>> same problem of returning to docks. But I am going to ask a few of the
>> owners who seem to use their boats frequently, year around.
>>
>> Even on the November day of my docking accident when mine may have been
> the
>> only boat out, I and my crew of two thought we were successfully turning
>> into the slip without incident after a great sail when at the last instant
> I
>> decided that the wind had caught the bow so that it was going to be pushed
>> too hard into the entering edge of the starboard finger pier. I hit
> reverse
>> on the engine to soften the blow (and one crew member jumped onto the pier
>> at that point) to try to push the boat off, when my motor jammed in
> reverse
>> and we went rocketing back into the boats in their slips behind me. (It
> was
>> when I forced the gear shift into forward just missing a collision with
>> those boats but permanently jamming the gear into forward).
>>
>> Interestingly, much larger sailboats in the larger slips opposite me (the
>> ones I back toward as I back out of my slip) seem to have no problem, at
>> least when I seen them come and go on normal days. One skipper with two
>> small sons repeatedly brings his 35-foot sailboat to a dead stop centered
> in
>> his slip with no lines whatsoever. The only differences I can see are (i)
>> they are headed towards a larger opening, (ii) they are turning to
> starboard
>> if that makes any difference--is that what people talk about when they
> refer
>> to a right-hand prop?, and (iii) their prop is inboard and at the center
>> line of their boat, giving better steering control.
>>
>> Lastly, even on relatively calm days, the approach to the slip requires
>> skill, paying complete attention, good anticipation and decisions and
>> sometimes a little luck. Many years ago, I had boats at marinas in lakes
>> and bays where this was not the case, within the limits of prudent
>> seamanship. For five years at one lake, I just sailed to the dock with no
>> motor at all (boats of 17 and 19 feet). In Biscayne Bay in Miami, I
> docked
>> regularly a 34-foot motor sailer in many kinds of weather and never any
>> problem. However, in the present case, for one thing, I usually have to
>> start my hard turn to port as if I were going to head into the (already
>> occupied) third slip out from me. If one were driving a car doing this on
>> dry land, one would crash into the motor at the back of that boat. I have
>> to "slide" out to starboard during the turn to actually come in,
> hopefully,
>> right in the middle of my slip without touching anything. Surprisingly,
>> this works at least half the time, and over the past 1-1/2 years until
>> November, the rest of the time involved a bump into a fender or the like,
> so
>> no big deal--at worst a rubbing of the gel coat alongside the white rubber
>> strip at the edge of the finger pier, or against the small turning wheel
> at
>> the entrance to the port finger pier. But there should be a way to make
>> this virtually 100% successful in all but emergency weather conditions and
>> where you could even explain to a guest skipper what he or she needs to do
>> as the best technique for this particular slip. My success rate had gone
> up
>> significantly after the first few months of owning the boat when I started
>> the practice of, if needed, momentarily engaging the engine in forward
>> during the turn, with the motor linked to the tiller. Then, if I weren't
>> going to complete the turn in time (i.e., coming in too far too
> starboard),
>> I would change the tiller/linked motor steering direction bringing the
>> tiller hard to port and momentarily hitting reverse to straighten the boat
>> out before proceeding (hopefully) straight into the slip. This appears to
>> have been hard on the engine, as you said in an earlier email.
>>
>> Roger, I really like your earlier suggestions, which I quote below:
>>
>> "You might consider finding a different slip for next season. For example,
> a
>>
>> slip right across from you would be better. A tight turn to starboard in
>>
>> this situation is much easier than to port.
>>
>> "If it were my boat & I were being more cautious, I think I would pull up
> to
>>
>> the end of the finger pier, port side to the pier. I would either put out
>>
>> fenders on the port side amidships or mount a suitable bumper on the
> corner
>>
>> of my pier. I would loosely tie off amidships & use a bow line to warp the
>>
>> bow around into the slip. No muss - no fuss."
>>
>> There is not alot of room to do this at my slip, but it should be
> feasible.
>> The finger pier at the port is only one foot wide, and their is a long
> boat
>> with a motor protruding to port. Likewise there is a boat and protruding
>> motor on the starboard side of my slip (mine being the last full one with
> a
>> finger pier on both sides to make an enclosure), and which of course one
>> would not want to "warp around" outside the edge of the slip and into that
>> motor. The slip is 10 feet side. So what you say should work with a
>> practiced technique, and I am going to try it. Using your single dock
> line
>> idea in your article quoted below, this could also be the line that I
> fetch
>> at the end of the port finger pier.
>>
>>
>> David Keyes
>>
>>
>>
>> ----- Original Message -----
>> From: "Roger Pihlaja" <cen09402@centurytel.net>
>> To: "The Rhodes 22 mail list" <rhodes22-list@rhodes22.org>
>> Sent: Sunday, January 12, 2003 5:53 AM
>> Subject: [Rhodes22-list] Combination Of Sharp Turn To Port + Single
>> HandedDocking
>>
>>
>>> Thank you Steve & Mark! This was the article on single handed docking I
>> was
>>> refering to.
>>>
>>> So, David, what do you think? Wouldn't executing a sharp 90 deg turn to
>>> port & throwing a single dock line over a piling or cleat on the end of
>> your
>>> finger pier be more graceful & less taxing on your equipment than what
> you
>>> do now?
>>>
>>> By the way, if your marina is so tight & the wind blows like you say,
> how
>> do
>>> the boats around you get into their slips?
>>>
>>> Roger Pihlaja
>>> S/V Dynamic Equilibrium
>>>
>>> ----- Original Message -----
>>> From: "Steve Alm" <salm@mn.rr.com>
>>> To: <rhodes22-list@rhodes22.org>
>>> Sent: Friday, January 10, 2003 5:41 PM
>>> Subject: Re: [Rhodes22-list] Single Handed Docking Article
>>>
>>>
>>>> Here it is:
>>>>
>>>> All boats have a point along both sides, usually just aft of
> amidships,
>>>> wherein a single dock line will cause the boat to stop parallel to a
>> dock.
>>>> To find this point, pick a place along the side. It's helpful to use
>> the
>>>> sliding cars on the genoa tracks for this purpose. Attach a mooring
>> line
>>> to
>>>> this point & pull on it from behind. If the bow pulls towards you
>> faster
>>>> than the stern, then slide the attachment point aft. If the stern is
>>>> favored, then move the attachment point forward. When the boat crabs
>>>> sideways towards you, then you have found the approximate sweet spot.
>> The
>>>> actual sweet spot will shift slightly when the boat has forward
>> momentum.
>>>> However, this approximate location will be sufficiently close to allow
>> you
>>>> to go out & try to pull up to a dock with a single line. Try to stop
>> the
>>>> boat with a single mooring line using your approximate sweet spot. If
>> the
>>>> bow or stern tend to crab towards the dock faster, then adjust the
>>> position
>>>> of the line fore or aft as before & try again. When you have found
> the
>>>> correct location, you should at least mark it. You may even wish to
>>> install
>>>> permanent mooring cleats there port & starboard.
>>>>
>>>> With a single mooring line, simply motor up to the dock, slip your
> loop
>>> over
>>>> the piling near the end of the dock, & shift into neutral. The
> mooring
>>> line
>>>> attached to the sweet spot will snub the boat's forward momentum & the
>>> boat
>>>> will almost magically "crab" sideways up against the dock. This
>> sideways
>>>> crabbing involves a tremendous amount of drag, which uses up the
> boat's
>>>> forward momentum in a matter of inches, thus making it almost
> impossible
>>> to
>>>> hit the dock. The boat will stop at a convenient distance away from
> the
>>>> dock for you to go around attaching your bow & stern lines at your
>>> leisure.
>>>> Try this technique. I guarantee it will make you look like a boat
>>> handling
>>>> genius!
>>>>
>>>> Roger Pihlaja
>>>> S/V Dynamic Equilibrium
>>>>
>>>> On 1/10/03 12:50 PM, "Roger Pihlaja" <cen09402@centurytel.net> wrote:
>>>>
>>>>> Hey Everyone,
>>>>>
>>>>> Did anyone happen to save a copy of an article I wrote several
> months
>>> ago re a
>>>>> foolproof single line docking procedure? I can't find it in the
>> SailNet
>>>>> archives or on the FAQ page & I don't know how to search the new
>>> archives.
>>>>> I'd really rather not retype the whole thing if someone has a copy
>> they
>>> could
>>>>> repost.
>>>>>
>>>>> I'd like to forward it along to David Keyes. The combination of the
>>> technique
>>>>> for making a sharp turn to port which I described in my previous
> post
>>> along
>>>>> with this single line docking technique might work very well in his
>>> situation.
>>>>>
>>>>> Roger Pihlaja
>>>>> S/V Dynamic Equilibrium
>>>>> _________________________________________________
>>>>> Use Rhodes22-list@rhodes22.org, Help? www.rhodes22.org/list
>>>>
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>>>
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