Moving a single engine boat sideways..

D

Dave M.

New Member
TECHNICAL Contributor
Oct 9, 2006
874
Hermiston, OR
Boat Info
270 DA
Engines
7.4L, Bravo II
I also mentioned in a previous post that I had attempted to move my 270 DA sideways, but had not been successful. I was also asked about that:
I assume moving sideways is similar to turning in place, except you move forward a little bit to the right, and then back up with the stern to the right...? But I can't quite figure how that would actually work.​
Well, so far I can't figure out how that would actually work either. So I am open for input from those who know. I am not ready to write it off as impossible. Maybe 10 years or so ago I was talking to a guy that builds and sells ultralights. We were talking about what was basically a wing with a motor attached, a suspended chair to sit in, and some cables to the wings to pull on. Somehow in the conversation he mentioned that he could do a forward or side slip, I forget which. I know enough about flying an airplane to know that to do that requires cross-control of the ailerons and rudder, the ultralight had neither. I mentioned that and asked him how it was possible. He said he could not explain it, he could just do it. You can pull differentially on the cables, and I am sure that was part of it.

My point is that if he can do that, then I am not ready to concede that it is impossible to move my boat sideways. I can't do it, without significant rotation; yet!

I do know that when I position the boat behind the trailer for loading, and I am stopped, getting lined up, that when I give it forward power to approach the trailer, I expect the boat to move to port maybe six inches or a foot as it begins moving forward. So maybe that is Step 1, and I have yet to discover Step 2.
 
Moving sideways with a single screw is possible, but about the only movement I can reliably get is when I'm moving forward parallel with the dock, crank the wheel toward the dock and put it in reverse. With the wheel toward the dock, it moves the bow and stern toward the dock for a short period of time relative to your speed. If you leave it in gear too long, the bow will begin moving away from the dock just as it does when you back up with the wheel hard to the left or right. I haven't noticed much difference CW vs. CCW? I guess you could do it, but it would be like Austin Powers in the narrow hallway turning the golf cart around. Lots of back and forth with little movement. At that point, I think it would be easier to to nose up to the dock and drop off a person with a line!!
 
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When that ultra-light 'slips sideways' he's also losing altitude. So he's not really 'moving sideways' as much as he's 'falling sideways'. Can't quite do that in a boat, heh.
 
Dave M. said:
I do know that when I position the boat behind the trailer for loading, and I am stopped, getting lined up, that when I give it forward power to approach the trailer, I expect the boat to move to port maybe six inches or a foot as it begins moving forward.

Is this due to p-factor or am I out in left field?
Click to expand...
 
Arizona: Yep. You have a single engine boat without a BIII drive. Didn't even need to read your SIG to see that. (hmmm. . .guess I need a sig in the new forum)

Anyhow. . what you are describing is "stern walk". You have a single rotating screw that is putting torque on the boat, moving it sideways. A common effect. With a BIII drive, (or a boat with dual props), the props are counter rotating so the torque from one prop cancels the torque from the other prop.
 
A single engine vessel will yaw to port with a starboard turning screw. More noticeable at slower speeds, but at slow maneuvering speeds generally wind and current will have greater effects than prop walk, depending of course on your sail area and tonnage.

BoatSchoolAugs
 
With a single engine and counter rotating props and no bow thruster you can't get there from here. With a single prop backing up will cause crabwise motion as described in the other posts

There are a number dockline/cleat tricks that can be done for docking, e.g.- attaching line to mid ship boat cleat and tied off to dock - forward motion will bring the boat alongside the dock, that will create the functional equivalent of sideways moving.

Henry
 
Dave
With my 230OV I did this quite a bit. With quite a bit of steering and forward then reverse shifting. The way I was successful was to get the bow to head toward the dock at a 45 degree or less angle moving forward, then shift to reverse and steer to bring the stern in. Once your forward movement has stopped and you begin to head backwards and the stern comes closer to parallel to the dock now you can turn back away from the dock and shift to forward. The affect now should move the boat sideways as long as the forward motion is not too much. If you're still too far away you can now alternate shifting forward turning away and reverse turning towards with the object making the movement towards the dock keeping from moving too far or fast in either forward or reverse. The struggle of inertia either way should result in the sideways affect.
 
I guess the goal is to get a boat alongside at a dock where you are 27 foot outdrive trying to get in to 32 foot dock space and you have one out drive screw centerlined? (A inboard screw with rudder has a different method.)

Begin close along side the boat off your bow with your prop centered, then back your stern in at an angle towards the dock about 2/3rd of the way back from the boat off your bow, Your bow will swing away from the boat off your bow.. Then as you approach the dock bring your wheel hard over and away from the dock and pump/tap the throttles until the stern begins to swing away from the dock bringing the bow in. Stop the throttles and let the energy work for you and then bring your wheel hard over towards the dock and check you backing progress and pump the throttles momentarily to kick the bow over twowards the dock , and then check your forward progress. You should be inside the linear distance and few feet off the dock. Now you may have to repeat this process to walk the stern over then the bow until crew can step off and tie the lines, or toss them to dock hands. Done well you'll get applause or at least an opportunuty to be smug about it.

If you have strong current or wind, you may get some help to make this look simple or ... a chance to get to know your insurance agent much better.

Running a 42ft sail boat with a single screw with massive rudder and deep fin keel, for years, I leaned to walk the boat sideways under favorable conditions. Mostly I let nature put me where I wanted to go but using current or wind to give me the extra push I needed to get sideways. And then I also learned when to just use lines and crew brawn and be done with it.
 
Arizona240DA said:
Is this due to p-factor or am I out in left field?
Click to expand...
"Is this due to p-factor or am I out in left field?" Good pun, you will be if you don't use right rudder!

It is similar, but the cause is different. With p-factor, the thrust difference is between the blade moving up and the blade moving down, due to the difference in angle of attack. So on a typical small plane, you need right rudder when you push the throttle forward for takeoff.

With a boat, the prop is normally pretty much aligned in the horizontal plane, and the props are so short it wouldn't matter much anyway. But, the blade on the bottom works against water that is constrained as to where it can go. The blade on top can just throw water towards or along the surface with less resistance. So the bottom blade will push sideways to starboard harder than the blade on top will push to port. (speaking of outdrives here) This will try and turn the boat left, so you need right rudder when you push the throttle forward for takeoff.

That's my theory, and I think my boat really acts like that. I do have to correct the course when I push the throttle forward, and I think it requires right rudder.
 
The way Todd describes is how I almost always approach the dock when loading the boat. I'm usually at the dock in the picture above. I guess I have gotten into a bad habit of always docking by putting the dock on the port side of the boat, I am uncomfortable trying it in the other lane. My old Glasspar is much worse for being cranky around the dock than the 270, and I just haven't learned better yet. I really did not expect to be able to turn in place CCW with the 270, and was happily surprised when I could.

I will have to go and try what Chad has described, I have not practiced doing it that way at all. I don't have a well trained crew, lots of the time at home here I just go out by myself on a weekday for a few hours and try things like this. Fortunately, the dock is well padded with canvas rub railing, so for gentle practice around the dock, I won't harm anything if something doesn't work as hoped.
 
Dave M. said:
I don't have a well trained crew, lots of the time at home here I just go out by myself on a weekday for a few hours and try things like this.
Click to expand...

Dave, in the San Juans you will have a HUGE crew to assist! In fact, just drive by and we'll lasso you and drag you to the dock!! I'm sure you've got it down pat and can put the boat anywhere in any kind of conditions! From the pictures, I can't imagine trying to turn around in a tight space like that. With patience and using the wind to your advantage I'm sure you can do it better than the rest of us!

Funny, I've never paid any attention to the fact that the boat turns better CW or CCW? I think I need to go for a boat ride to check this out! I just crank the wheel, go to neutral, reverse the wheel and put it in reverse. If the results weren't successful, repeat until I'm facing the right direction or give up in frustration!!
 
Sundancer, I have almost no experience putting the boat into a slip or other tight space. Since I keep it on a trailer, I don't need to do that. So for me, boating in the San Juans around lots of other boats is much different than what I am used to.

I think how much difference you may see between CW and CCW movements depends on how far your prop is below the water surface. Most of my boating years are in the old Glasspar, where the boat had a fairly flat bottom at the transom, and the prop was not too deep. It wasn't until I was reading a bit in Chapman's Piloting a couple of years ago that I gave it much thought. I knew I habitually docked with the dock on the left, but I never gave it a thought about why. It was just what I did. I always docked as Todd mentioned above; approached the dock at an angle, then with the bow almost there, put it in reverse and pull the stern to the dock while stopping.

So, when you put it in reverse, the prop wants to walk the stern to the left, regardless of which way you turn the wheel. So it pulls in nicely to port, but poorly if docking to starboard. But the effect seems to be significantly less with the 270 DA.
 
I guess that makes sense. My prop is 2 - 3 feet down at the bottom of the V so I don't think I get much prop walk. It seems to handle the same regardless of Port vs. Starboard.

I really should break down and get a Chapmans to read!! I'd probably learn why an anchor is better than throwing that old block tied to a rope overboard!
 
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