Monday, June 25, 2012

Prop Walk and other Mysteries


“Prop Walk” and Maneuvering Around The Marina

One of the trickiest parts of sailing doesn’t have anything to do with sailing.  It has to do with motoring around the marina.  This includes backing out of a slip, shifting into forward gear after backing out of the slip, and motoring back to the slip.  For new sailboat owners, successfully backing out of a slip may be the trickiest and toughest part to boat ownership.
The reason that backing out of a slip is so tough is because sailboat engines are notoriously underpowered; AND the propellers are also very small compared to the size and weight of the sailboat.  Compare for example a twenty-five foot long powerboat and its fifty to two hundred horse-power engine and huge propeller with a twenty-five foot sailboat with its six to ten horse-power engine with its “tiny” propeller.  The “tiny” propeller doesn’t move much water with each revolution…… BUT, the propeller can “walk” the stern of the boat to the left or to the right before the boat begins moving either forward or backward.
We talk about the propeller being either “left handed” or “right handed”.   This refers to the rotation of the propeller when in forward.  If the boat is not moving and the propeller begins to turn, the rotation causes the propeller to “paddle-wheel” and move the stern of the boat to one side or the other.  A “right hand” propeller tends to walk (prop walk) the stern to the right (starboard) in forward; and to the left (port) in reverse.


 





Problems are created for new sailboat owners if the “prop walk” moves the stern in the “wrong” direction…… to the left when the skipper wants the stern to pivot toward the right.  No amount of rudder angle will prevent the “prop walk” because the boat is not moving forward or backward; so, no water is flowing along the rudder.










 





The problem becomes worse as the stern continues to pivot in the wrong direction.  If the boat eventually makes it out of the slip, the boat is headed in the wrong direction.
The easiest solution to overcome the effects of “prop walk” is to use the tiller on the outboard engine to help turn the transom in the desired direction.  This takes some practice so-as to know how much to turn the engine while in reverse and when to straighten out the engine before engaging forward gear.
Another problem occurs after the boat is out of the slip.  If the skipper has backed out successfully, he/she often thinks (wrongly) that the boat should be lined up straight down the slip row before shifting into forward.  The boat may be stopped in the water or even be backing up.  So, considerable “prop walk” is going to take place as the boat is shifted into forward gear.  If the boat is lined up straight before shifting into forward, the stern pivots to the right and as the boat gains forward direction, the skipper finds that the boat is now aimed at the boats and slips across from the slip just exited.


 









It is better to back the boat out to about a forty-five degree angle and then shift into forward.  The transom pivots with the “prop walk” to the right - - aiming the bow right down the slip row.  Yea!!!!  A perfect backing out and motoring away.


 

Monday, June 11, 2012

Thoughts on Anchoring


 

Thoughts on Anchors and Anchoring
      
Anchors
          Sooner or later, you'll want to anchor your boat for the night.  This may be because you've planned your trip to arrive at a destination that has neither docks nor moorings available.  Or, you may have had a tough sail in deteriorating conditions and you need to rest before going on.  There are many other reasons as well.  In any case, you will want to make sure that your anchor and its related equipment (ground tackle) is ready to use.  You (and your crew) really won't enjoy drifting around a potential anchorage in bad weather and decreasing light, while you try to find and shackle together your anchoring system.
          Your anchoring system includes:  your anchor, a length of chain, the anchor rope, and two shackles to attach everything together.  The anchor needs to be sized to your boat.  The following are some suggested anchor to boat sizes:
           
Anchor Type



Boat
Length




18'
20'
22'
24'
26'
28'
Danforth

8 lb
8 lb
8 lb
13 lb
13 lb
13 lb
Bruce

11 lb
11 lb
16.5 lb
16.5 lb
16.5 lb
16.5 lb
CQR

25 lb
25 lb
25 lb
25 lb
25 lb
35 lb








Chain Size

1/4 "
1/4 "
1/4 "
1/4 "
3/8"
3/8"
Chain should be 100% of Boat Length















Rope Size

3/8"
3/8"
3/8"
7/16"
7/16"
7/16"
Rope Length should be 200' or more








Anchoring
          The more often that you sail, the more likely that you will begin spending "nights on the hook".  And, the more often that you anchor your boat, the more likely that you will have "adventures" in the middle of the night.  Usually, these adventures have little long term effect on your sailing.  The important thing to remember when anchoring is that there are a few basic rules to follow, such as:
1.  As hard as it is to believe, make sure that the anchor is securely shackled to the rest of the ground tackle before you toss it over the side.
2.  Equally hard to believe is to insure that the other end of the anchor rode is securely tied to the boat somewhere.
3.  Be sure to let out enough anchor line to insure that the anchoring system will hold you at high tide where you want to stay overnight.  Waking up tomorrow morning to find that "the island has sunk during the night" is not the kind of adventure that most of us want before breakfast.
          and 4.  Make sure you'll have enough water under you at low tide.
          We have already said that the anchor system consists of the anchor, a length of chain, and the anchor rope.  Each piece is securely shackled to the next, and most of us like to make sure that the shackle bolt does not turn itself out by using a wire to hold the bolt from turning. 
          The type of anchor, the length of chain, and the size and length of the rope are all decisions that will vary from skipper to skipper and sailing area to sailing area.  In general, you can ask other sailors in your area what kind of anchor they use and prefer.  You'll probably find that a Danforth style is the most popular.  Danforth anchors are relatively easy to stow and have acceptable holding power, pound for pound.  Instead of weight, the Danforth anchor uses its ability to dig into the bottom to hold your boat.  The length of chain provided in many "safety & equipment kits" is often about six feet.  This is OK for “lunch on the hook”; but if you are anchoring overnight or if you have had a high wind or storm adventure, you have probably increased the length of chain to equal to your boat's length.  Some skippers have even opted for 100% chain with no rope at all.  Of course, this will give you the best holding power and shock absorption; but, it is a chore to weigh the anchor when you want to leave, and is quite a heavy bit of ballast while sailing.

          Many sailors have a rule of thumb regarding the amount of anchor rope to set out when anchoring.  The rule depends on the expected wind:
          Light breezes - Depth of water times four
          Moderate breezes - Depth of water times seven
          Stormy conditions - Depth of water times ten
This means that if you anchor in twenty feet of water, you will want to deploy 80 feet of anchor line in light breezes, and possibly more than 200 feet if stormy conditions are expected.  Some skippers will deploy two anchors for stormy conditions for extra holding power.  These are usually set out at about a 90 degree angle to each other.  If you are worried about holding, you might rig a “sentinel” – a weight deployed down the anchor rope on a shackle and light line – to act as a shock absorber and extra weight to keep the anchor stock parallel with the bottom.  I have successfully used one or two sash weights.

          It is handy to mark the anchor rope in regular intervals.  I like 25 foot intervals.  These lengths are easily divided into 100… so I don’t need a calculator to determine how much rope to let out.  Additionally, since Snickerdoodle is 25 feet long, I have 25’  of ¼” chain… so everything is in 25 foot intervals.

          It is better than nice to have an anchor roller on the bow.  This roller allows the chain and rope to more easily be let out and pulled back in.  My anchor roller has a loop above the actual roller to keep the rope and chain from “jumping off” the roller. 


Anchoring Steps –
First, Check your charts, local knowledge, etc. to select where you want to anchor.  Generally, I like to anchor in about 20 feet of water (~3.5 fathoms).  Determine how much scope you want to let out on the anchor line….  Four to one for nice weather; seven to one for moderate weather; and at least ten to one for stormy weather.
Second, Observe your selected anchorage as you approach for other boats and their anchors, and other hazards.
Third, Once over your selected anchorage spot, release the anchor.  When you feel the anchor touch the bottom, begin backing the boat up and simultaneously pay out the anchor line until the required scope is out.  Cleat the anchor line and continue backing down till the anchor sets (digs in).  If the wind and waves allow, I like to back toward the shore so that I can be sure the required scope still lets the boat float in enough water.
Finally, When the anchor sets, shift the transmission into neutral and/or stop the engine.
       One of the things I like to do if I’m alone or with an inexperienced crew is to lay out all of the required anchor rope in long parallel loops on deck before getting to the anchor spot (called “faking” the line on deck).  If I need 80 feet of anchor rope for Snickerdoodle, I’ll fake the anchor rope down the starboard side for 20 feet (about to my primary winches… and then fake an another “loop” of rope down the port side to the cockpit.  I cleat off the anchor rope to a bow cleat at the 80-foot mark.  Then, I’ll take a couple turns on the starboard primary winch and wrap the loop around the cleat with the loop of rope at the 20-foot mark.  I can then let the anchor chain pay out over the bow roller and bring the anchor back to the cockpit (having the anchor rope on the winch and cleat keeps the chain from pulling the rope off the deck prematurely).  I like to have the rope to chain shackle just down from the bow roller so that there is only rope on the roller and the anchor chain bows in the water below the boat.  When I’m just about to the chosen anchor spot, I throw the anchor out to the side of the boat and cast off the anchor rope from the cleat and winch.  The anchor sinks and the anchor rope begins paying over the roller as I continue to motor slowly toward shore.  When all of the anchor rope has gone over the roller, the bow cleat brings the rope taught and the anchor digs in and sets… this pulls the boat around 180 degrees and you are at anchor.
          So, go out there and anchor your boat and enjoy an evening on the hook.