Prop walk

[rslifkin]

Originally Posted by Tmacmi

I have a long list of practice tests I've planned out: figure 8 in reverse, backing up to a stationary object, etc.

The challenge that I particularly had in mind was a problem last year.

We were tied up in a slip with the dock finger on the starboard. There was a port bow tie on land and pile on the port side at the stern quarter where you would expect it.

But the slip was also designed to accommodate a longer boat by having standing pilings about 10'-12' further back from the dock finger.

That required a long straight path backwards.

There was a strong wind from port to starboard. I tried to give it enough throttle to over come the wind

You know the result. Bow swings towards dock, stern heads directly for secondary piling. Lots of scrambling to fend off, embarrassed skipper.

In a case like that, I'd be inclined to get the stern as tight to the dock as possible and the bow out a bit on departure, knowing that when you put it in gear, the stern will move enough to clear the dock, but that'll give you some clearance to not smack the bow while you get moving enough to steer.

[Tmacmi]

Originally Posted by Glory Days

Hope this question does not creep the OP's thread and may be helpful to him as well as me.
Charlie; as a new boat owner I'm interested in exercises that will help me dock/undock etc. Can you expand on this comment ?

Thanks

I just finished the online Skipper Course and Maneuvering Under Power Clinic by Nauticed. They both had very good explanations of how a sailboat acts under power and how to use spring lines.

We went to Key West to do our in person work 3 weeks ago. Unfortunately we had 25-35 knot winds everyday and couldn't really work on docking maneuvers.

Fortunately we had 25-35 knot winds everyday and we got to sail like banshees.

[Shrew]

Originally Posted by Tmacmi

I have a long list of practice tests I've planned out: figure 8 in reverse, backing up to a stationary object, etc.

The challenge that I particularly had in mind was a problem last year.

We were tied up in a slip with the dock finger on the starboard. There was a port bow tie on land and pile on the port side at the stern quarter where you would expect it.

But the slip was also designed to accommodate a longer boat by having standing pilings about 10'-12' further back from the dock finger.

That required a long straight path backwards.

There was a strong wind from port to starboard. I tried to give it enough throttle to over come the wind

You know the result. Bow swings towards dock, stern heads directly for secondary piling. Lots of scrambling to fend off, embarrassed skipper.

Put a line on the outmost piling on the finger-pier side (or the side you want to be on). When you pull up, grab that line and give it a wrap around you midship cleat. Turn the rudder away from the finger pier side, and use the line to spring around the piling while doing the 'bump and fill' method I described earlier.

The spring line should keep you from blowing off.

[Shrew]

Just to add....

In my case, I know I only back to Stbd, so I get a slip with the finger pier on the STBD side. If no fingers piers, then I simply make sure I pull up with my stbd side on the piling and spring around the piling so I backing to Stbd. IF the wind is helping me I don't need a spring line. If the wind is against me, the spring line helps.

[Tmacmi]

Originally Posted by Shrew

Put a line on the outmost piling on the finger-pier side (or the side you want to be on). When you pull up, grab that line and give it a wrap around you midship cleat. Turn the rudder away from the finger pier side, and use the line to spring around the piling while doing the 'bump and fill' method I described earlier.

The spring line should keep you from blowing off.

I'm following you. I'll practice that. In this particular instance there was a second set of pilings further out that couldn't be reached to set spring lines.

[dannc]

Originally Posted by Tmacmi

...
We were tied up in a slip with the dock finger on the starboard. There was a port bow tie on land and pile on the port side at the stern quarter where you would expect it.

But the slip was also designed to accommodate a longer boat by having standing pilings about 10'-12' further back from the dock finger.

That required a long straight path backwards.

There was a strong wind from port to starboard. I tried to give it enough throttle to over come the wind...

The boat we charter has a port side prop walk and the boat is tied to a pontoon on the starboard. Maybe 5-10 feet to port is another boat.

On the boat, there is a loop/bight of dock line tied to the aft, starboard cleat and then forward to the starboard, amidship cleat. It is forward spring line, so to speak, but attached at both ends to the cleats on the boat.

When leaving the slip, all dock lines are removed from the dock cleats, EXCEPT the loop/bight of line that is acting as a forward spring line.

The line handler gets on the boat and stands ready next to the this loop/bight of line. This loop/bight keeps the stern from moving to port as we back out of the slip.

Once the boat gets moving aft, and we have enough way on, the line handler flicks the loop/bight of the line and we are clear.

Worse case, is that the line handler misses the flick, and the loop/bight does not come off the cleat. If that happens, all the person at the helm has to do is put the gear in forward, give it a bit of RPM, and the boat will move forward, at which point, we can either dock the boat, or put the gear in reverse, and try to flick the line off again. We have never had this happen though.

Going into the slip, the line handler stands ready on the starboard side of the cockpit, ready to do the Ape Hanger Fling. Think of an Ape hanging from a limb in a tree, your arms are above your head, but instead of holding a limb, you are holding the loop/bight mentioned earlier. The line handler needs enough of a loop/bight of the dock line to be able to flip/fling the loop PAST the cleat when the boat comes along side the cleat. the line handler needs just enough of the bight/loop to flip/fling, but not too much so that the fling/flip does not work.

The trick is to LOOK and AIM behind the dock cleat. We have practiced the Ape Hanger Fling in the house with our practice dock cleat.

Once that bight/loop is on the cleat, we have a forward spring line, and the helm just has to apply a bit of forward RPM to pull into the slip. The spring line will lay the boat right next to the dock. We might also turn into the dock if there is a bit of wind trying to blow the bow off.

Originally Posted by Tmacmi

You know the result. Bow swings towards dock, stern heads directly for secondary piling. Lots of scrambling to fend off, embarrassed skipper.

We came up with leaving the bight/loop on the cleat because of something similar to what happened to you. One day we were leaving the dock and it was low tide. The marina needs to be dredged. We knew this and we knew the boat was likely aground. We waited. Then waited some more. However, the problem was we did not wait long enough. A small wake, well, waked us, and we thought we had enough tide to leave....

So we did. The keel was in enough mud to act as a pivot point as the port side prop walked whipped the stern of the boat around like we were a spinning top. Not real fun but nothing was damaged except our ego. Boats have a way of adjusting ego.

Next time we left the dock, we used the procedure listed above.

A few months later, our sailing instructor AND four people he was taking out on a class, where on the boat next to the one we were taking out. So we had an audience. As we did our thing, the instructor said we had left a line on the dock, and as he said that, he realized what we were up too. The technique works for us.

Practicing back and fill and other techniques under power helps one get a feel for the boat and what it will do. Or not do, as the case may be.


However, you might get some strange looks...



We were practicing docking, back and fills, etc., one day. Someone on shore, who had attended the school, called the instructor and said we were doing circles in the water, going back and forth, and we might be in trouble. He called and we explained what we were doing. All was good. Same day, as we were practicing docking, an older couple on sailboat thought we needed help docking and headed over to us and asked if we needed help. Nope, just practicing.

I supposed some might be offended but we thought the couple, and the guy who called the instructor, did the right thing. It was a nice thing to do.

Later,
Dan

[manisland]

I doubt if the answer is as simple as 2 or 3 blade prop will have more prop walk.
Certainly the total area of the blades is an issue, as is the pitch of the blades when in reverse will play into the equation. Also certainly blade shape is an issue. (What taper, how bulbous, etc). Also RPM has to be a major component in the results.





Blade thickness could also be an issue, but I'm less sure about that, and most likely other 2nd order effects.



But without consideration of the other issues, you aren't going to be able to answer that question.

[belizesailor]

Originally Posted by Searles

Simple answer is yes ,a three blade prop will exhibit more side thrust ,prop walk than a two blader if the blade area is the same ,narrow blade props have less prop walk at low revs than big blades ,use prop walk to your advantage.[emoji569]️[emoji572]️

The under water profile of the boat, and entry angle of the prop shaft, make a big difference too.

Boats with sail drives, thus an entry angle almost parallel to the water line, generally have almost no prop walk because the prop wash in reverse has less contact with the hull than a shaft mounted prop (which is typically angled downward, thus directing more reverse prop wash toward the hull)

[belizesailor]

Originally Posted by dfelsent

Prop walk is your friend.
Short bursts in reverse, yes.
Your stern moves to port in reverse. So does mine. Big time.
For fun put your helm hard to starboard when stopped, on a calm day. Hold it there. Alternate a few seconds of reverse with a few seconds of reverse. Don’t move that helm. You just might spin in place. That’s a cool thing to be able to do. Looks like a bow thruster.
And useful.

So docking and in really tight quarters you have a new tool.

Yes before you establish headway in reverse it’s a nuisance. But you can spin in places you couldn’t.

Yes, learn how to use prop wash to your advantage and you will no longer view it as an impediment.

[belizesailor]

Originally Posted by chrisr

this works best with a hydraulic clutch. full ahead to full astern, without bits of gearbox flying out the companionway...



cheers,

Just need to be gentle with a mechanic transmission.

Hydro transmissions are great fun though...full reverse to full forward in the blink of an eye, no worries!

[belizesailor]

Originally Posted by Charlie

...

The best thing someone on this forum suggested was that you should practice doing figure 8's in reverse. In both directions. Once I learned how to do that my boat handling skills under power improved dramatically.

Yes a good exercise.

When I teach boat handling under power, I take students out into open water and we do figure 8's in forwad and reverse. It is an effective way to learn how a boat handles in both directions.

Keep a firm grip on that helm when backing though! It can get backed by the reverse water flow and slam over hard.

The next exercise I do is to drop a mark in the water, or use a mooring ball etc if handy, and have them make approaches to the mark (bow to and side to).

After that its time to move on to actual dock approaches. I just have them do touch and go's...get within a couple of feet of the dock, stop the boat, then head out and try it again. This gets them comfortable with approaching fixed objects (which is what makes most uncomfortable)

Then on their final approach, its really just a simple matter of actually securing the dock lines.

[belizesailor]

Originally Posted by Tmacmi

I have a long list of practice tests I've planned out: figure 8 in reverse, backing up to a stationary object, etc.



The challenge that I particularly had in mind was a problem last year.



We were tied up in a slip with the dock finger on the starboard. There was a port bow tie on land and pile on the port side at the stern quarter where you would expect it.



But the slip was also designed to accommodate a longer boat by having standing pilings about 10'-12' further back from the dock finger.



That required a long straight path backwards.



There was a strong wind from port to starboard. I tried to give it enough throttle to over come the wind



You know the result. Bow swings towards dock, stern heads directly for secondary piling. Lots of scrambling to fend off, embarrassed skipper.

One way to counter act that is short hard burts of reverse just to get the boat moving backwards. Once you have sternway, you then have steerage in reverse without the drive actually being engaged. Just give it more short shots of reverse to maintain momentum, but induce minimal prop walk...which can be offset with rudder.

If prop walk does start to move the bow/stern in a direction you dont want then opposite helm (to direct the thrust) plus a burst of forward thrust will counter act that. Just enough to induce the boat to pivot, not enough to stop sternway momentum.

[deblen]

Same boat? Vandestadt Spirit 28. Len

https://www.youtube.com/watch?v=R_f7Yuv4ocw

[chrisr]

Originally Posted by belizesailor

Just need to be gentle with a mechanic transmission.

Hydro transmissions are great fun though...full reverse to full forward in the blink of an eye, no worries!

yep, this exactly why i mentioned it

had my first clear demo of this years ago when a friend showed me he could turn his 60' single screw motor yacht in it's own length by doing just that - full ahead to full astern and back again...repeat...as fast and as often as you wanted. marvelous !

try doing that with a mechanical g/box and you are very quickly up for a new one !

cheers,

[belizesailor]

Originally Posted by chrisr

yep, this exactly why i mentioned it



had my first clear demo of this years ago when a friend showed me he could turn his 60' single screw motor yacht in it's own length by doing just that - full ahead to full astern and back again...repeat...as fast and as often as you wanted. marvelous !



try doing that with a mechanical g/box and you are very quickly up for a new one !



cheers,

My first hyrdo transmission experience was an old tractor we had when I was a wee lad...full speed forward then full reverse! [emoji1787]