9.5 Maneuvering the Single-Screw Trawler: The Art of "Goosing" to Make 360 Turns
Back in November, 1997 a lively thread popped up on the Internet Trawler-World mailing list, TWL, on Single vs. Twin engines. This perennial subject quickly evolved into a discussion of how to maneuver a single engine boat -- an art that must be learned by a Krogen captain to be able to look "cool" and avoid serious damage to one's boat and pride (not to mention others' boats). I tried to describe in text form some tips on how to do this, and judging from the responses from others on the list, it seemed helpful. Although this sort of stuff is "old-hat" to the long-time, single-screw skippers, I thought some of the new folks in our club might find it useful It all started with the following two quotes. (In Internet email quotes from some else's messages are usually denoted my the ">" marks at the left margin.)
>"October would occasionally simply decide she wouldn't turn to port. We
>got tired of doing 270 turns."
>Exactly. My present single engine boat has a keel and a lovely great
>rudder but with any wind blowing ( a Mistral can go on for a week) you
>can forget about backing her anywhere but left about. The 270 degree
>turn is often the only option I've had in a medium wind - and it's
>great luck if I've got room for one in a Mediterranean harbour - or on
>our narrow canals.
At the risk of stating what may be obvious to some of the folks on this list, I'm going to toss my $0.02 into this part of the thread...
First of all, I've had this identical discussion with some of the single-screw owners in our marina and the ones who've been bold enough to try these techniques have told me the experience has been very helpful.
The first "secret" to tight-quarter maneuvering the single-screw boat is to learn how to "back and fill" to "rotate" the boat, not "drive" her around. Using this technique, you can do 360-degree turns in EITHER direction in less than two lengths of your boat -- and, if you get good at it, it'll be 1.5 lengths or so. This technique consists of stopping completely and putting the helm all the way over and leaving it there throughout the turn. Then shift into forward and give the engine a quick "goose." You really have to hit it hard, so the first time you practice this, try it out in the harbor where you're close enough to objects to see the effect of what you're doing, but not so close you're likely to get into trouble. As soon as you've "goosed her" forward, throttle back, then immediately shift into reverse and "goose her" again -- hard enough to kill all forward motion. You will see that the forward goose has rotated the boat perhaps 30 or 40 degrees and the reverse goose has killed her way again so she's barely moved forward. Repeat the process over and over until you've rotated the boat the desired amount.
Of course, because of stern walk in reverse, you'll find this works better in one direction than the other. For example, our boat backs to starboard, so rotating the boat to port is MUCH easier because BOTH parts of the maneuver (forward AND reverse) assist the turn, whereas when you turn her to starboard the reverse goose tends to slow the turn. However, it CAN be done in both directions -- even in a breeze. Start by practicing the "easy" way and THEN work on being able to do it the "hard" way. Leave the helm alone during the maneuver -- it's only effective in forward anyway.
The second "secret" to this is that you can NOT be gentle with the power when you "goose." Think of it as handling a mule, not a lover. It will makes LOTS of noise, and if you're in shallow water (say, less than 5 to 8 feet under the keel, you'll kick up a LOT of mud to boot. If you're lucky enough to live in an area where there are watermen (who most all use single-screw boats -- think about it!), watch THEM turning and backing in small spaces. In our area, you can hear their engines a mile away doing this. Observe the action of the stern during the forward goose -- it seems to almost "hop" over several feet in the direction you want it to go. As you watch what's going on during the turn, you'll note that you're effectively moving the stern around the bow -- or at least a point maybe 25% back from the bow. This is quite different from what the twin-screw folks can do by pivoting around the stern -- or at least a point maybe 25% forward of the stern. Nonetheless, it works pretty well.
Here's the rub. While you're doing all this, the wind and/or current is causing you to drift. Start by practicing this on a calm day. THEN, when you can do it quickly and smartly, try it in the wind. The quicker you turn, the less distance you'll drift. When trying it in a narrow slipway or around docks, you'll just need to allow for the drift by starting your maneuver a suitable distance up wind or current.
You'll also find that this works a lot easier with a semi-displacement boat (with very little keel aft) and with fin-keel sailboats (that's where I learned this), but it will work with the full-keel trawler (or sailboat) -- it just takes more of a "goose" (and MORE gooses (geese?) to make the turn.
After you've gotten pretty good at this, take her into a slipway where the boats don't hang out the ends of the slips and practice making the turns in tight quarters. If you have a flybridge, that's the best place to do this from so you can watch both ends of the boat. If you only have a lower station, you'll want to put a spotter on the stern to watch your distance from the pilings. Do this the first time on a calm day. Soon you'll be doing it confidently in a bit of a breeze.
OK, so far, we have only talked about rotating the boat, but there's yet another maneuvering requirement that's just as tough for the single-screw boat -- that's backing in a straight line. It's really not all that hard IF you remember secret #2. Always use quick, hard bursts of power when you "goose." This will let you complete the maneuver in shortest order, minimizing the drift due to wind and/or current.
OK, let's say we want to back our boat (that backs to starboard due to propwalk) slowly into a narrow slipway. Start by lining up with your stern headed in toward the slipway and put your helm all the way over to starboard (and leave it there). (WHY put the helm to starboard? Because when you're backing slowly the helm has very little effect anyway -- especially with a full-keel boat, so putting it to port won't do much to counteract the natural tendency of the stern to move to starboard anyway, and we're going to need the helm to starboard for the "gooses" -- you knew that had to be coming, right?) Now, put her in reverse and give her enough throttle to get her moving in reverse. As soon as she's moving backward (and starting to turn to starboard), shift into neutral and coast. This will stop the propwalk and let you coast almost straight back. As you start to slow, shift back into forward and give her a quick goose. Because of the starboard helm, this will "hop" the stern to port without moving forward (completely offsetting the propwalk -- plus maybe a little more), and then you can then repeat the process. Now, this may sound a little complicated (you'll be following a slightly "scalloped" path), but you can back as slowly as the wind/current conditions will allow without terrorizing yourself or the other owners in the yard.
Now, wouldn't it be easier to get a bowthruster and let the bowthruster do all the work? Sadly, no, at least not with a 20-ton, full-keel boat and most electric bow thrusters (although hydraulic thrusters of, say 25 hp or so, can be very effective). Even in calm conditions, you can only move the BOW with the bow thruster, so offsetting the propwalk is easier with the gooses, since THEY move the stern back into place. We have a bow thruster, but I seldom use it -- relying instead on the techniques I've been talking about here -- they're MUCH more reliable. The bow thruster is a 5-hp, 12-volt model that draws nearly 400 amps from a dedicated 8D battery located about 2 feet away. As I recall, it puts out around 150 lbs of thrust, maybe a tad more. However, it doesn't take much in the way of marine growth to reduce that thrust significantly. On the other hand, the 100+ hp main engine can always be counted on to be sufficient. On the other hand, I only count the bowthruster for a little "finesse" in calm conditions -- in conjunction with these other techniques. By itself it won't prevent a disaster in a fresh breeze.
Finally, practice these maneuvers over and over until you feel comfortable with them. Pick a calm day (during the week when nobody's around) and practice backing into every slipway in the marina. Then, when you think you're ready, come in bow first and practice backing out and then doing 180s to get out. THEN, pick out a few empty slips well into the slipway and practice the 90-degree turn to line up with the slip and back in! (Believe it or not -- I find it easier to back into a slip now than trying to come in pointy end first.) If you have sturdy rub rails (let's hope you do), get used to letting them touch the pilings, gently of course -- otherwise you'll need a helper to fend off occasionally. The key is practice and MORE practice (along with quick, hard geese) so you know exactly how YOUR boat handles.
For some discussion on backing a single-screw boat into a slip with spring lines (which is even slicker), check out my Website:
PS. PLEASE don't let your boat know I likened her to a mule!
Later another TWL subscriber made the following comment, in part:
>I have a marvelous collection of very fuzzy texts in English, French
>and German too, where the GOOSING principle is decidedly not stressed.
To which I replied:
This comment (and several other similar ones) prompted me to check in the various texts on boat handling I have lying about. Know what? You're right! Only ONE even came close to describing the "backing-and-filling" technique. The one that does describe it is "Boat Handling Under Power," John Mellor, Sheridan House, Inc., 1993. Unfortunately, John doesn't use this term to describe it however. On p. 37, he describes "Turning at Low Speed," where he states, "It is essential to appreciate that a boat with a rudder can best be turned at low speeds by driving a powerful flow of water from the propeller across the rudder; the slow water flow past the boat will produce very sluggish steering. A tight turn can thus be made by using a succession of short, sharp bursts of power, maximizing the turning effect of the slipstream while minimizing forward movement." (For some reason he doesn't mention using reverse to aid in minimizing forward movement.) However, in the succeeding section, "Turning Short," John goes on to state, "A single-screw boat with a rudder can, surprisingly perhaps, be turned more tightly than twin screws, being capable of a three-point turn quite literally on the spot... The secret is to make the initial turn against the propeller effects, giving a brief hard kick ahead to swing her with the slipstream over a fully angled rudder. As soon as the stern begins to swing, put her full astern and allow the increased prop effects in astern gear to continue pulling her stern around; there is no need to alter the position of the rudder as it will only have effect when the prop is going ahead. Then go ahead again as before, and repeat the whole cycle as often as necessary. As long as you never allow the boat to actually gather way ahead or astern, simply using prop effects or slipstream to swing the stern sideways each time, she will turn on the spot quickly and powerfully. The more nearly stopped the boat is to begin with, the tighter the turn." Now if he'd only called it "goosing!" (;^)
BTW, I recommend John's book (I have the paperback edition) VERY highly. He describes a LOT of techniques that will be useful for handling trawlers -- like how to move the boat directly sideways (without turning at all) using the bowthruster, docking alongside, maneuvering in wind and current, how to use spring lines and warps (very important, IMHO, when clearance for a turn is only inches, rather than feet -- and a LOT easier to do than it sounds, even short-handed -- especially if you have a sturdy rub rail), narrow-waters handling (including how to "read" your boat's message to you that she's getting too close to shallow water for comfort), an so on. He also describes the Mediterranean moor (including how to do it in a strong crosswind). Only "biggies" missing seem to be the Bahamian moor (more of an anchoring technique than a maneuvering technique, I suppose) and how to cross a bar with a strong following sea that's moving faster than you are (often the case with trawlers). Since the helm responds BACKWARDS under these conditions, I think it deserved some discussion.
Another topic which could have used some discussion is what I call "weather cocking," the tendency of a boat that's dead stopped to turn it's bow away (usually) from the wind. It's VERY useful to understand exactly how your boat behaves when dead stopped in a wind, because this turning effect can be too powerful to counteract without heroic measures. Better to understand what she's going to do and then plan wherever possible to take advantage of it. This is particularly necessary with backing-and-filling in tight quarters where you don't need to be battling any adverse forces. (Of course, you'll always have to consider the downwind drift due to the wind -- both in planning where to start your turns and in completing the process smartly to reduce the time you're exposed to the wind effect.)
Next time you're out in a good breeze, stop dead in the water with your bow either just off the wind or a right angles to it. Now, watch what happens. Of course, the boat will start to drift downwind. That's expected. However, note that it may TURN also. How she turns and how fast she turns may be VERY useful to account for in tight quarters. For example, a sailboat under power (sails furled) will almost always "weathercock" with her stern toward the wind. With a fin-keel sailboat, this will happen VERY quickly, regardless of her angle to the wind when you stopped. (The reason is that the wind pressure on the mast and above-water portion of the hull acts forward of the spot where the water acts on the underwater portion of the hull, including the keel.) With a trawler, this effect may not be as dramatic and could, I suppose, be exactly the opposite, depending on the design of the hull and deckhouse location. Our Krogen 42, for example, hardly turns at all. (Frankly, I preferred the rapid turning of our old fin-keel sailboat!) Why? Well, when I planned my tight-quarters turn with the sailboat, I would intentionally stop with the bow at least 20 degrees or so off the wind IN THE DIRECTION I WANTED TO TURN ANYWAY. Thus, this turning effect aided the backing and filling rather than opposed it. Now, I have to do ALL the turning work myself. I strongly suggest you find out how your own boat behaves in the wind when stopped -- do it out in the harbor where you won't have to worry about hitting anything as you drift along, and then use her tendencies to your advantage when you can.
PS. John also mentions in his book the importance of pausing in neutral long enough for the gears to stop turning when shifting from forward to reverse and back. It should go without saying that the engine should be at idle speed before shifting into either forward or reverse. At the very least, high-speed shifts can cause the damper plate to disassemble itself or, even worse, cause the transmission itself to do so. (:^(
To which another TWL subscriber, added:
>The video "Single Engine Boat Handling" by Bennett Marine does show and
>explain the back and fill turn somewhat. The interactive docking
>simulator in the "Hands-on Powerboating" >CD of Chapman's is also great
Yes, the video does, indeed, AND it features the Krogen Manatee 36 in all the demos!