In the fall of 2006 I sent the following in an email to a couple who were considering the move from a fin-keel sailboat to a Krogen 42 trawler, amd were understandably concerned about handling a large, single-engine, full-displacement boat.
Here's a terrific article on maneuvering a large single-engine boat:
Driving a Single: The Challenge of Handling A Single-Engine Boat
By Bruce Wood
Passagemaker Magazine - March/April 2000 issue, pp. 62 - 69
Note: I checked the Passagemaker.com website in July '06 and they haven't published this article for free on the Web - it's only available in the complete issue, which they still sell - for $6 for the single issue. See: http://www.passagemaker.com/issues/18.asp for ordering info.
Here's a quote from the Introduction to the article to give you the "flavor.":
"At speeds below two or three knots, the typical trawler begins to act differently because the subtle effects of propeller motion, rudder, wind, and current have a more noticeable influence on a vessel's behavior. Nobody wants to feel like a stressed-out lady in the bow-thruster advertisement that shouts, "Honey, it's your turn to dock the boat!"
There are several basic types of powerboat propulsion: the outdrive, a boat with twin engines, and the single-engine vessel. Each requires somewhat different techniques for slow speed maneuvering, and all have their proponents.
Most will probably agree that the single-engine vessel is probably the most challenging, but can be the most rewarding as well. Unfortunately, a great many boaters remain fearful of the single-engine boat. They believe a boat with twin engines is far easier to maneuver, despite the additional maintenance and expense of the twin propulsions system.
There is no question that driving a single is more of an art form than handling a twin-screw boat, requires more practice, and involves more advance planning and action thinking.
The single-engine vessel is a mind game and a skipper must constantly think like the rudder and propeller.
Let's step through an example of actions and reactions when leaving a slip and going into a slip with a single-engine, rudder-steered vessel. Most of today's single-engine trawlers are equipped with bow thrusters, but if you do everything just right, you don't need it. I try very hard not to rely on a thruster, thinking that if I do need it, I probably did something wrong a moment ago and need the thruster to correct for my error."
Here are some of MY comments on Wood's article and Kessler's comments (included in the article):
Sailboats ALSO have a large rudder, so they can perform these backing and docking maneuvers just like trawlers. Granted, the prop is smaller, but that means more rpm may be needed to turn the boat Ð also the chance for cavitation will be greater.
Backing in a straight line when the wind and/or current is significant will likely require the throttle to be used in addition to the transmission. When the wind/current is pushing the boat to starboard, the throttle will need to be "goosed" in forward gear to "hop" the stern to port. Then immediately shift back into reverse to continue the backing process. In general, the stronger the wind or current, the more throttle will need to be used and the quicker the shifts will need to be done. Backing out of a very narrow slip (ours is only 1.5 feet wider than our boat) will require VERY close attention to the boat position and MUCH more frequent shifts to avoid touching the dock/pilings on either side.
Neither author mentioned the fact that the tendency of these boats to back to the side is ONLY the case when the transmission is in reverse. This does NOT happen if the transmission is in NEUTRAL. So, once the boat is moving back in the proper direction, you can shift into neutral to continue the backing motion WITHOUT the tendency to back to the side.
Neither author mentioned the use of spring lines when docking or backing into a slip. Thee are VERY important skills which need to be added to the discussion. See the articles on my Krogen FAQ Website for more on this. The URL is: http://www.his.com/~vann/KrgStuff/Krognidx.htm and the specific articles have links about 3/4 of the way down this page.
Kessler's comments do not JUST apply to huge trawlers. They apply equally well to a 20-ton full displacement Krogen 42. We even use them to parallel dock our RIB Ð even when approaching our swim platform.
Kessler's comment about maneuvering DEAD SLOW is worth emphasizing. For example, if you're coming into a slip bow first and you're moving too fast, applying a lot of throttle in reverse to stop can swing the stern into the dock/pilings on the side. This is also useful to remember when turning the "back to starboard" boat to starboard. When we approach our narrow fairway to our slip, we do not have room to make a wide sweeping right turn. For this reason, we come to a COMPLETE STOP before starting the turn. The rudder is put hard to starboard and the throttle is "goosed" to start the turn. If done properly, the boat is barely moving by the time the 90-degree starboard turn is completed. Remember that a little reverse "goose" will stop the turn if the boat is going to swing too far. In summary, the boat will turn a LOT more in a short distance when the maneuver is begun from a dead stop than when the boat is still moving at the beginning.
I recommend practicing the back and fill technique in open, calm water. If you can do it near a mooring, so much the better, because the mooring will give you a reference point to judge how smartly you are doing it. The object is to start from a dead stop, then make a 180-degree turn without moving the boat more than half a length forward (or backward). Start by making this turn the "easy" way Ð ie, if she backs to starboard, make the turn to port so the prop walk in reverse helps tighten the turn. Once you're pretty good at that, practice making the turn the other way Ð you'll quickly see, the "easy" way is easier, so it's best to turn this way in tight quarters if possible. Practice until these turns can be done fairly quickly, because when wind and current become an issue, the longer it takes, the more effort will have to be put in staying in place instead of just making the turn. Once you feel comfortable in the open water, try it in more and more confined spaces Ð in a fairway between slips for example.
I like to practice backing in a straight line in a fairway also. (After, of course, practicing backing up to that mooring in relatively open water. Try it upwind, downwind, and crosswind to be sure you can control the boat in all situations in tight quarters.) Back into the fairway first, so you can go back out forward if something goes awry. This is a GREAT confidence builder.
Kessler's description of using a bow spring to leave a tight space on a dock needs more thought. Ideally, the bow spring needs to be rigged so the crew on the boat can release and retrieve the line from the boat without relying on someone on the dock. The usual procedure is to "double up" that spring line (as well as perhaps a breast line to hold the boat to the dock until it's time to depart). These lines are easy to rig, but great care must be exercised to make sure that the line can be retrieved Ð without it getting caught on the dock, cleats, or pilings. Bear in mind that the most common reason for needing to use the bow spring is because wind and/or current is pressing the boat onto the dock, so more throttle may needed in these cases. Also, since you will be pressing your forward rail against the dock/pilings, etc., you will probably need a fender to prevent damage to the rail. Many boats can be protected by adding "bang iron" (a metal strip) to the rub rail or upper rail. The bow spring must be rigged so as to prevent the boat from sliding along the dock Ð especially important on sailboats which may have chainplates exposed along the forward rail(s).
Earllier, after reading the article (and my comments) a full-keel Tayana 39 owner said he was going to try to install a Maxprop to eliminate the "propwalk" action. To which I responded:
Actually, most of the time I find the prop walk is HELPFUL! Especially when trying to turn the boat 90 or 180 degrees in a tight spot. Also, when docking parallel to the dock on the side the prop walk pulls the boat toward. It allows me to approach PERPENDICULAR to the dock, stop with the bow about 5 feet from the dock (and 1/3 boat length from the bow's final resting place), and turn 90 degrees to port, ending up about a foot from the dock and perfectly parallel -- leaving the spectators agape, especially those on the boats just a few feet from my bow and stern at the end! The only time I find propwalk annoying is when I'm coming into our slip bow first and need to stop -- WITHOUT hitting the piling on that side (starboard, the side the KK42 backs toward). We only have about a foot and a half clearance total in our slip, so I have to try to be only inches away from the port side when I stop because the prop walk pulls us to the right. Just some thoughts...