boat waddles at slow motoring speeds

[GARY WEEKLY]

i,ve had it with this thing,,was out on the chesapeake bay this past weekend and couldn,t get my x to behave while motoring at 5 knots..wind and waves would shove it as much as 90 deg off course! i tried the center board trick but that did not work,,i finally had to resort giveing up my pleasure cruse and cranked it up to 10 knots to get some better handeling out of it,,so i,am putting out this notice to see what the boat users among us are seeing for handeling problems

[Dimitri-2000X-Tampa]

What size motor do you have? I've found that the boat tracks best with about 6 inches of CB rope let out. This drops the board out of the trunk but still keeps it mostly horizontal (simulating more of a full keel) Theoretically, this should give better tracking at slow speed than dropping it further, although dropping it further probably gives better roll stability.

You may also have wanted to drop some rudder. This seems to be less important with big foot engines, but it is particularly important if you are getting quartering following seas which will push the stern around. If you had the CB all the way down or all the way up, this may have caused a pivoting action. You may want to try dropping one or both rudders next time, but not a good idea to go much faster than 8 kn with any of the boards down.

[Frank C]

The boat is definitely sensitive to winds, so it helps to keep speed a little higher (say 5 knots). But I've never experienced anything quite so dramatic as you described. It almost sounds like the other problem ... with CB fully deployed, the track wanders due to foil lift.

Even at 10 knots, dead ahead, the symmetrical foil sets up vigorous alternating lift across one side or the other. This causes oscillations that constantly redirect the vessel's path. The result is imprecise, unpredictable, potentially dangerous steering. This is far from mysterious, and completely unrelated to the hull, the transom, torsion, or any other structural design element, or failure thereof. The foil is simply causing fully understandable and expected, but undesireable lift to either side. It's not mysterious, not deficient, and certainly not structural in any manner.

Even at only 5 knots, the fully deployed CB will indeed cause unpredictable handling. However, I frequently extend only 3 inches of CB line as a skeg, with a noticeable tracking benefit. (If you're fed up and selling cheap, advertise it here. There might be buyers in the wings).
(Just kidding! ... really!)

[Don T]

Hello:
If your situation was a following sea, you were experiencing what most boats do. Picking a different course or altering speed to keep up with the troughs might work better. I will agree that broaching is the Mac's weekness. It is narrow in the beam and pointy in the bow which lends itself to being pushed and rolled from the aft quarters. If the seas are big, then put all boards down, ballast in and steer a zigzag course. It will improve the ride. Don't let surfing down the face of a wave get your speed too fast This might stress the steering sys too much. I opt for a different course as a first resort and zigzag only when I cannot change it (such as a narrow river inlet or channel).
Once, not in the mac, I had to navigate in a trough for 30 minutes. All you could see out both sides was water taller than the boat. Only my GPS told me where I was cuz I could not see until I throttled back and let a crest roll under. I lost contact with the boat I was buddied with.

[Arthur Kelly]

Gary: We have found that we get the best low speed powering performance with rudders and centerboard down. By low I mean around 4 to 5 knots. Above that we raise everything. I have only powered the boat once with rudders and cb up in the 4 to 5 range. It was a nightmare. There was little to no control at all.

[mgg4]

The Voice of Experience speaks:

When moving through the water and going from fast power (all boards up), to slow power or preparation to sail, ALWAYS put the rudder(s) down FIRST, then the centerboard.

We have had bad experiences with the centerboard creating a pivot point, and without the rudders down, there was little to no control provided by the slow turning engine.

Food for thought.

--Mark
[/quote]

[Don B]

The first tme out with my boat I found that it did not respond well to helm at 5mph. The bow just kept swinging back and forth. The wind was coming straight at me, it was a pretty wide channel but it felt like I was taking up the whole channel. I found it rather alarming.

I later learned that higher speed gave me better control.

Of course this does not help you when you want to just go slow and it also does not help when trying to navigate into a slip at a slow speed.

I did not know that centerboard could cause problems when fully down at around 5mph.

I will try the slightly down position next time as I can see the benifit of it acting like a extended keel.

-Don B

[HERNDON]

Having a 8 hp motor. I always lower the rudders all the way and have a little center board down before leaving the dock. Otherwise it seems to oversteer from one side to the other.

[mgg4]

As a nonMac owner I'm going to be criticized for saying anything. However, just like many boats have a sweet spot or range where they handle nicely, many also have a sour spot.

... if your doesn't like 5 kts., but handles fine at a slightly high speed, drive faster

Which is fine, except when you're trying to dock.

I find that wind is the major culprit in most of these "Bad handling" reports. The has a lot of surface area to grab the wind, and at slow speeds can be a handful no matter what you do. But this is true of many boats as well, so this is nothing new. I've had my share of problems with the wind, and I'm sure I haven't seen the last of these problems, but every time I go out I learn a little bit more about the . Probably about the time I've mastered this boat, it will be time to sell it and get a bigger one.

In general, in close quarters you must go as slow as possible, but also remember you must be moving to control the boat, and the boat steers from the stern.

If you are having trouble making a landing into the wind, you might try turning the bow away from the wind and backing up close enough to the dock to throw a line to someone on the dock. After they tie that long spring line, you should be able power against that line (forward or reverse, depending on the space available) to bring the boat alongside.

As always, practice makes perfect, and going just fast enough for control in these conditions can make the whole operation a much safer operation. Don't give up. Practice the operation in open water until you feel comfortable enough to try it in close quarters.

--Mark

[ronacarme]

Motoring under 7.5 mph....
1. no boards down, the boat hunts from side to side vigorously...fogetaboutit!
2. in deep enuf water,with all boards down ( CB line out 25% or more), Carmen is happy to steer.
3. in shallower water not permitting all boards down, I finally can run with 2-3" CB line out and one shoal piggyback rudder down (draws same as the motor), I finally can steer fairly well in smooth water by anticipating the swing of the bow with a minimal movement of the wheel to meet it ,and then halfway back onto course, centering the wheel and letting the bow complete its swing back onto course....keep repeating for each off course swing....The rougher the water, the more you want all boards down.
4. with big waves on the rear quarter, the stern wants to slew back and forth...so I either try to steer as in 3 above or sometimes just let the stern slew as long as the average course is in the right direction...Quartering waves seem to get a good grip on that big, wide, deep, powerboat stern.
My old 26D and other sailboats I have motored were less fussy to steer, tho quartering waves of size did tend to slew.

[Frank C]

Gary,
Dimitri's and others comments on quartering seas, plus another comment about wind, bring back memories.

Quarter seas, and their customary tail wind, will unavoidably impact your course. As mentioned earlier, keeping boat speed at the swell's speed is best. Also, a stiff wind "on the bow" will distinctly grab the bow and push it to either side - again, unavoidable, except to increase speed markedly.

The fate is not so bad, as at least there's an answer. That's not always true in a daysailer.

[GARY WEEKLY]

THANKS FOR ALL THE REPLIES GUYS,MY WIFE HAS COME UP WITH THE PERFECT ANSWER--WE,RE GOING TO GO INVESTIGATE A 13000 ACER LAKE WITH NO WAVES OR TIDES. LET YOU KNOW

[Russell]

anyone using a four blade prop? I hear that will give you better control at slower speeds.

[Frank C]

I tested a 4-blade Comprop because it was on West Marine's open-box shelf. Unfortunately it was 4X13X17-pitch, versus my aluminum 3x14x13. Silky smooth at all rpms, with good performance, but it was over-pitched. WOT rpms dropped by 600 revs (~5100 to ~4500), with related top-speed reduction. West Marine put it back on the open-box shelf.

Solas (Australia) scanned my prop stats and recommended a stainless 3x14x13 (no 4-blade offered) and I finally opted for it, plus a prop-lock. Unfortunately, the Suzuki DF60 spins it like a pinwheel, and spools right past max 5,400 rpms without hesitation. So the result ... I'm back to the aluminum prop. Someday I'll haul it up to Sacramento and have the prop shop fix this stainless prop. Wish I'd found an appropriate 4-blade, I sure liked it's balance and smoothness.

One cannot generalize from this ... the DF60 has 1300cc versus 966cc for a Merc Bigfoot 60, so the motors would handle the load differently. Most 50 hp outboards have only 12" diameter props and smaller yet engine volumes (Honda BF50 @ 800cc) - seem to recall that few 4-blade props are offered for them.

[mgg4]

anyone using a four blade prop? I hear that will give you better control at slower speeds.

I'm using a four-blade prop from ProPulse. One thing I noticed right away was that reverse performance was much worse. I think this had to do more with the highly-cupped blades, rather than then number of them.

I do notice a bit better "Hole-shot performance," but I'm less impressed with the new prop than I thought I would be. Handling of the boat is about the same, with the exception that when you goose the throttle in forward, you get a quicker reaction from the boat.

--Mark