Boat Handling Puzzle

[Dockhead]

Let's say you are tied up port-to to a pontoon berth and are getting ready to depart. You have room ahead and behind. But 20 knots of wind is blowing from your starboard quarter, pinning you to the pontoon. To make matters worse, you are single handed!

You have a bow thruster, so you don't think you're going to need to warp off. Ordinarily, you would steer towards the pontoon -- left rudder. Put the engine in gear in ahead and give it some revs. Use the starboard bow thruster. Like this, you would ordinarily move sideways off the pontoon, where you would straighten out the rudder and carry on out to sea.

But it's blowing a hoolie, and you don't want to scrape along the pontoon. So what do you do? Here are a couple of variants, but other ideas are also welcome:

1. Fender up at the bow, throw off the lines, then use the port bow thruster to angle the stern out into the wind. Then a good burst of power in astern with the rudder hard over to starboard. As the boat starts to move, a little starboard bow thruster to keep the bow from scraping, but not enough to allow the stern to fall off the wind. More starboard bow thruster will make clearance to the pontoon when the rudder starts to bite and pull the stern out.

By the way, a similar technique can be used on boats without thrusters: just rig a slip from the bow, and when you're ready to depart, haul in hard on the bow line to pull the bow to the pontoon and angle the stern out. Then throw off the line as the helmsman puts on power in astern.

2. Fender up at the stern, throw off the lines, starboard bow thruster to pull the bow off the pontoon. Burst of power in ahead with rudder moderately to port, starboard bow thruster to keep the bow swinging out.


Which would you do? Any other ideas?

[motion30]

I was in that exact situation comet and was able to get off as you described in your first scenario. But the lesson I learned that day, if it is blowing that hard better to stay on the dock as I got my butt kicked and.lost my dinghy

[oceannavigator]

Originally Posted by motion30

I was in that exact situation comet and was able to get off as you described in your first scenario. But the lesson I learned that day, if it is blowing that hard better to stay on the dock as I got my butt kicked and.lost my dinghy

Coming in to docks is about going slowly. Minimal speed to maintain steerage.

Leaving is just the opposite.

There is nothing complicated about this situation on a sailboat.

I've never had a bow thruster.

Get that bow kicked out, then just gun it forward. Once steerage is obtained and you are doing a couple knots, you just keep the stern skirting the dock until clear. Eye the stern as you depart.

No puzzle needed.

[atoll]

if it is blowing 20 knots in the marina in the solent,it is blowing 35 outside!

sounds like a good excuse to go and discuss the situation in front of a log fire at the yacht club bar.............

[Dockhead]

Originally Posted by oceannavigator

Coming in to docks is about going slowly. Minimal speed to maintain steerage.

Leaving is just the opposite.

There is nothing complicated about this situation on a sailboat.

I've never had a bow thruster.

Get that bow kicked out, then just gun it forward. Once steerage is obtained and you are doing a couple knots, you just keep the stern skirting the dock until clear. Eye the stern as you depart.

No puzzle needed.

I don't know about your boat, but the wind will blow my bow onto the pontoon in that situation. Above 20 knots of wind, even a 10 horsepower bow thruster like mine won't hold the bow up.

In my opinion, coming out in reverse -- stern-first into the wind -- is strongly preferable. Once you get your stern into the wind, then your boat is stable and won't weather-cock onto the pontoon.

[Dockhead]

Originally Posted by atoll

if it is blowing 20 knots in the marina in the solent,it is blowing 35 outside!

sounds like a good excuse to go and discuss the situation in front of a log fire at the yacht club bar.............

Yep, I am in Cowes, and that would be Plan A for me. Go up to the Fountain for a pint and think about it!

But time and tide wait for no man -- I have to get back up the Hamble and onto my mooring -- flight to catch tomorrow.

[valhalla360]

In that senario, I would wait for the wife to return and for the wind to settle down.

Assuming, it's our boat and the wife is there, one of us would fend off a bit on the bow, crank the wheel hard to starboard and back out until we are clear. It's great having a steerable outboard for these situations.

[DoubleWhisky]

Originally Posted by Dockhead

I don't know about your boat, but the wind will blow my bow onto the pontoon in that situation. Above 20 knots of wind, even a 10 horsepower bow thruster like mine won't hold the bow up.

In my opinion, coming out in reverse -- stern-first into the wind -- is strongly preferable. Once you get your stern into the wind, then your boat is stable and won't weather-cock onto the pontoon.

Hi Dockhead

I think You are almost right here (probably completely right for Your boat), but, You know, "almost" make a great difference

Your port side is to the berth. Your scenario number one is really good, as long Your propeller give You a prop-walk towards starboard. If opposite You can be in unpleasant situation, as Your prop-walk will be pushing You towards the wall or ponton.

I'm always trying to moor alongside in the way to have a prop-walk pushing my stern outside on back revs, but it is not always convenient.

Cheers

Tomasz

[atoll]

Originally Posted by Dockhead

Yep, I am in Cowes, and that would be Plan A for me. Go up to the Fountain for a pint and think about it!

But time and tide wait for no man -- I have to get back up the Hamble and onto my mooring -- flight to catch tomorrow.

you must have low water coming up soon, i find in the channel you will generally get a bit of a weather change at the change of tides.

wind might slacken off for the next couple of hours once the tide stops running.

other wise as others have said,get the bow off and go like hell,
might ask the marina guys for a bit of a push off the dock as well

[oceannavigator]

Originally Posted by Dockhead

I don't know about your boat, but the wind will blow my bow onto the pontoon in that situation. Above 20 knots of wind, even a 10 horsepower bow thruster like mine won't hold the bow up.

In my opinion, coming out in reverse -- stern-first into the wind -- is strongly preferable. Once you get your stern into the wind, then your boat is stable and won't weather-cock onto the pontoon.

May be a full keel ketch, but any spade rudder modern hull shape can steer away.

Just add up the force vectors. Like shooting a game of billiards.

If the bow is pointed away from the dock and you have forward thrust, the situation is the helmsman's to screw up. Picture the extreme case. Instead of 30-40 degrees bow out, what happens at 90 degrees out from the dock?

No way would I back out! The bow would drag along the dock!

A boat is steerted from the stern, pivoting on the keel or other center of effort below the waterline. Backing out will spin the bow closer to the dock.



It's all about steerage and speed.

This works on 30ft, 45ft monohulls, larger catamarans, etc... anything that has good tracking and steering ability.

[atoll]

to answer you first question,i would rig a spring line to the bow,power the stern off in fwd with the helm hard over,till 45 degrees from the dock,then slow astern using bow thruster to get you out in to the channel,but you will need someone on the dock to cast off bowline once you are clear.

[Dockhead]

Originally Posted by DoubleWhisky

Hi Dockhead

I think You are almost right here (probably completely right for Your boat), but, You know, "almost" make a great difference

Your port side is to the berth. Your scenario number one is really good, as long Your propeller give You a prop-walk towards starboard. If opposite You can be in unpleasant situation, as Your prop-walk will be pushing You towards the wall or ponton.

I'm always trying to moor alongside in the way to have a prop-walk pushing my stern outside on back revs, but it is not always convenient.

Cheers

Tomasz

I should have mentioned that my prop kicks to port! So prop walk is working against Variant 1. If my prop kicked to starboard, Variant 1 would be a no-brainer.

[Dockhead]

Originally Posted by atoll

to answer you first question,i would rig a spring line to the bow,power the stern off in fwd with the helm hard over,till 45 degrees from the dock,then slow astern using bow thruster to get you out in to the channel,but you will need someone on the dock to cast off bowline once you are clear.

That's the voice of huge experience

Thanks for that -- yes, now that I think about it, that would work a treat. I like that a lot -- you would get very far clear of the dock that way so would gain a big margin of error in case you get blown around. I guess the thing to be most careful about is to not bash the bow on the pontoon when you are motoring forward against the spring line, and the stern starts to swing out. I'm not sure you could get all 45 degrees before you start bashing the bow, but I guess it depends on the shape of your boat.

Unfortunately I was dead single handed, so no spring lines allowed, in this particular case.

[Dockhead]

Originally Posted by oceannavigator

No way would I back out! The bow would drag along the dock!

A boat is steerted from the stern, pivoting on the keel or other center of effort below the waterline. Backing out will spin the bow closer to the dock.

I think I would agree with you if we were talking about a boat without a thruster.

The absolute greatest thing about having a bow thruster is that you can steer the boat from both ends. It's like having a rudder at both ends of the boat. So yes -- backing out will definitely spin the bow into the dock (I think I mentioned that), but with the thruster you can steer the bow to keep it just off the dock -- something I use it for constantly.

[Dockhead]

OK, so here's what happened in the end:

I threw off all the lines at a leisurely pace -- as the wind was pinning me to the pontoon.

Then, I went for Variant 1.

I used port bow thruster to angle the bow in and the stern out and into the wind. Remember that the one stable position for a single-masted sailboat with the sails down is stern into the wind.

Once the stern was nearly aimed into the wind, the wind stopped blowing the boat around and stopped blowing off the bow. I used the thruster to hold the bow close to, but not touching the pontoon, then powered astern with the rudder to starboard.

Despite the prop walk to port, it worked very well and without any kind of drama. The key was getting the stern into the wind to take the wind forces off. Trying to go out in ahead would have been a mistake because angling the bow out would have put it just at the angle where it is blown off the most. I don't think I would have been able to avoid scraping the port side quarter on the pontoon as I would have needed starboard rudder to hold the bow up -- the thruster, even with 10 horsepower, would not have been enough, so I could not have ported the rudder the move the stern out.

The other advantage of moving out astern into the wind was that the stability of this posture was also needed after I got off the dock. If I had moved out in ahead I would still need a bit of speed to keep the bow up, and this was in close quarters inside Cowes Yacht Haven. As it was, I was able to motor off in astern at low speed and in perfect stability.