requiem
Well-Known Member
Consider that tide simply translates the boat whereas wind tends to rotate the boat, so the decision would be whichever best accounts for both factors. (Helpful, I know.)
Yes, a marina berthing question!
- Thread starter reyes
- Start date
Consider that tide simply translates the boat whereas wind tends to rotate the boat, so the decision would be whichever best accounts for both factors. (Helpful, I know.)
Dockhead
Well-Known Member
But wind also pushes the boat through the water downwind, besides rotating it.
The effect of tide is more like piles, buoys and pontoons moving, not the boat moving towards or away from them.
The interaction of both effects can be very complex.
dansaskip
Well-Known Member
Ferry gliding is an excellent technique and probably not understood or used by the majority of yacht people ( shout at me if I am wrong)
boomerangben
Well-Known Member
Absolutely so in the same way, the tide acts on the hull and its appendages. But when you are underway using the engine, the point of action of propeller thrust (the thrust bearing/saildrive attachment points) will generally be aft of the centre of drag on the hull (at slow speeds) so if you go astern in a tide won’t the vessel tend to “weather vane” with the stern to the tide? In other words you can “hang” the boat off the power of the prop and if you are holding station, the tide will tend to turn the bow down tide. My thinking (and it is not backed up by practice) is the OP could ferry glide stern to the tide until they get to the berth, straighten up and then use short applications of astern to control the rate at which the tide moves them alongside the finger. Spring from bow to end of finger, motor forward against spring with tiller towards the finger to hold position while you secure the rest of the lines.
fredrussell
Well-Known Member
Just to add: for what it’s worth, the greatest boat handlers out there will still feck it up once in a while. Boat repairs are expensive, fenders are cheap. Festoon your boat with them.
Ammonite
Well-Known Member
This approach is what I suggested earlier. ie. hanging in the tide in reverse, but I would not use a spring from the bow as you enter the berth as it will pivot you into the boat alongside or risk turning you side on to the current as the stern is pushed out. You need to use a miship spring as this will pin you to the finger
flaming
Well-Known Member
Boat repairs are cheap compared to people. I've always told my crew "If I've messed it up, it's my problem not yours. Don't risk your limbs trying to save me money on repairs. Shove a fender in the gap if you can, but otherwise fiberglass is easier to fix than a crushed limb."
And boy oh boy did I feck it up earlier this season. In my defense it was a particularly tricky one, but I got it very, very wrong and ended up completely sideways across a pen at HYS. Naturally with a very large audience.
flaming
Well-Known Member
The viability of ferry gliding into a berth backwards depends a lot on the strength of the tide. You need the tide to be stronger than the minimum speed you need to retain steerage way in the prevailing wind in order for it to work. That is quite a lot of tide.
For what it's worth, in your scenario I would almost certainly reverse into the berth, but do so by reversing all the way down the aisle and turning into the berth. I'd do this with a reasonable amount of speed to make the steering sharp and minimise the risk of being swept sideways, and the reason I'd do it in reverse rather than forward is twofold. Firstly, when reversing the pivot point is closer to the back of the boat, so it's actually easier to do a sharper turn in confined spaces where the "leading" end has to be precise but the trailing end has room to swing. But the main reason is that when you are then arriving in your berth with tide under you and your speed as well, you are using forward power to stop the boat, which is a lot, lot more effective than reverse power. And in your case, if you need an adjustment you can bang the helm over and use the prop wash to flick the stern one way or another as you do it.
Ammonite
Well-Known Member
Been there, done that. I had three novices on board and was so focused on telling them what to do while coming alongside, that I collided with the wooden bowsprit on my neighbours boat, who were in the process of selling and onboard at the time. Fortunately, the damage was very minor and easily repairable (and they are an extremely nice couple!)
Ammonite
Well-Known Member
I guess it depends on the boat. Mine is fitted with a Autoprop and I can almost count to 10 before the boat stops and starts moving when going from reverse to ahead, even with a load of revs, whereas it stops very effectively when engaging reverse. Its the only thing I really don't like about the design.
flaming
Well-Known Member
That sounds.... unusual....!
Ammonite
Well-Known Member
It's a very unusual prop design! It tends to reverse in its natural state and needs the water flowing over the blades in ahead before it will pitch up and provide you with any meaningful thrust. 10 seconds is probably an exaggeration but it can be a little daunting when reversing out of a berth with a strong cross wind as you come to a stop and I'm very glad I have a bow thruster on these occasions. Mind you the boat (a Moody 36) is a little on the heavy side which doesn't help. The great thing about the Autoprop is that allows you to cruise at the same speed in ahead as those with more conventional props while doing a lot less rpm.
reyes
Active Member
Interesting! So, a few weeks ago, I did exactly this (same berth, same tide conditions, but a touch of wind to starboard as I was reversing down the aisle). I had a decent amount of momentum, testing my steering with a few small 'S' turns to check responsiveness whilst reversing. The boat adjacent to mine was also out at the time. As I made my turn, I got about halfway before I started sliding quite a bit to the pontoon. Due to the fact that I had space to starboard (reversing in to berth to lay port side-to), it wasn't an awful experience, though it wasn't the tidiest by a long way either.
It's this type of situation that's made me ponder how I'd approach it differently, based on wind factors etc. In your message there @flaming, my concern is the boat behaving consistently through the turn when abeam of tide and any wind. It feels fraught with danger to my novitiate mind! What's your opinion on the alternatives we've been discussing based on this situation?
- Alternative 1: reverse down the aisle, then initiate a turn reversing into tide (holding the boat on the spot as it does so), and then drifting in using reverse to control.
- Alternative 2: based on the more notable delays with steerage with reverse, drive down the aisle forwards instead of reverse and perform a similar manoeuvre, which is to say turning into the tide, and allowing the current to drift back, using drive to hold and steer where required.
I feel like we could all collaborate on a book. I ordered one yesterday so if it's no good I'll start looking for a publisher!
reyes
Active Member
Interesting! So, a few weeks ago, I did exactly this (same berth, same tide conditions, but a touch of wind to starboard as I was reversing down the aisle). I had a decent amount of momentum, testing my steering with a few small 'S' turns to check responsiveness whilst reversing. The boat adjacent to mine was also out at the time. As I made my turn, I got about halfway before I started sliding quite a bit to the pontoon. Due to the fact that I had space to starboard (reversing in to berth to lay port side-to), it wasn't an awful experience, though it wasn't the tidiest by a long way either.
It's this type of situation that's made me ponder how I'd approach it differently, based on wind factors etc. In your message there @flaming, my concern is the boat behaving consistently through the turn when abeam of tide and any wind. It feels fraught with danger to my novitiate mind! What's your opinion on the alternatives we've been discussing based on this situation?
- Alternative 1: reverse down the aisle, then initiate a turn reversing into tide (holding the boat on the spot as it does so), and then drifting in using reverse to control.
- Alternative 2: based on the more notable delays with steerage with reverse, drive down the aisle forwards instead of reverse and perform a similar manoeuvre, which is to say turning into the tide, and allowing the current to drift back, using drive to hold and steer where required.
I feel like we could all collaborate on a book. I ordered one yesterday so if it's no good I'll start looking for a publisher!
(Apologies for duplicate post: forum gave me an error and when it refreshed it had duplicated -- I also see no option to delete).
Last edited:
flaming
Well-Known Member
Think of it this way.
When you are moving at sufficient speed through the water, be it forward or backwards, your keel is gripping the water, your rudder is exercising control. So you can steer. When you stop moving, when water stops flowing past your keel and rudder, you now have no control over the direction your boat is pointing in, simply because you have no flow over the rudder. And with no flow over the keel either you might drift sideways, or rotate, depending on the wind. (Not tide). Add in that in strong winds the speed you need to be going before the grip of the keel and rudder exceed the wind effects is not zero.
So any plan that involves swapping from forwards to backwards (or vice-versa) in confined waters need to be made in the knowledge that there will be a period of time between losing steerage going one way before it is regained going the other way. And therefore any such plan needs to consider what the wind and tide will do to the boat whilst you are in this no-control phase. And this can be quite boat specific.
For this reason, I am always wary of plans that involve changing between forwards and reverse whenever there is some wind. The potential for errors is definitely higher. Especially if swapping to reverse, as you don't then get the benefit of propwash.
If your berth is on the outside of your final turn, that is always going to be easier, as you can afford to come in faster, and allow the momentum of the turn to "wash out" the boat into the pontoon as you apply reverse thrust to stop the boat.
if your berth is on the inside of your final turn, and especially with wind blowing you off the berth and tide sweeping you in. That's going to be one of the trickiest approaches. In that case I would go past, all the way up the aisle in forwards, with the stern to the wind. Assuming that at the inshore end of the aisle the tide is significantly less, and with the wind on your stern, swapping to reverse is about as easy as you'll get, then come back fairly fast, and reverse into the berth, again washing out the turn to mitigate for the wind blowing you off.
Still not an easy one at all though.
reyes
Active Member
Very grateful for such a comprehensive answer, thank you.
As everybody has said, and as I subscribe to myself, practice practice practice is definitely required.
I alluded above to the fact that a marina skills day didn't actually involve doing any of this except for the final parking manoeuvre by one person, and with more favourable pontoon position (relative to tide, and the first finger in the aisle). I wonder if this is due to marinas probably feeling a little nervous about allowing such training around their members' boats!
finestgreen
Well-Known Member
I've always been told 15 knots of wind is very roughly equivalent to 1 knot of tide (but of course that it can only be an approximation and you need to judge the specific situation based on what the boat actually does)
flaming
Well-Known Member
I'm not sure that holds really, as wind and tide do somewhat different things to the boat.
A 1 knot tide will move the boat at 1 knot in whatever aspect it is in relative to the tide. And because the movement relative to the water is zero, there will be no steerage.
In contrast the wind will first blow the bow off, so that if left to its own devices the boat will end up pointing roughly downwind. And then move the boat through the water. The difference there is that if being blown, especially downwind, you may well still have some steerage.
The best plans in restricted space involve using the elements to assist what you want to do, rather than fighting them. The classic one you see is if the wind is blowing down the aisle and the boat is bows in the easiest thing to do is come out of your berth and turn the stern into the wind as the boat wants to turn that way, and then just reverse out of the aisle. But a lot of people fight the natural tendency of the boat to turn that way and end up getting somewhat stressed trying to make the boat turn in a way that it does not want to.
finestgreen
Well-Known Member
Of course, but specifically to the question of which factor is likely to dominate.
flaming
Well-Known Member
If you have both wind and tide, unless there is a ton of wind, the tide will dominate which way the boat moves, the wind which way it wants to point.
In river pontoon marina berths, like the OP, both can be seriously complicated though. Since the current is stronger in the center of the river than close to the shore, and the presence of other boats, especially larger ones, can have an effect on the wind. So as you're deciding out in the fairway, with a strong tide and a decent cross wind, you may well find that by the time you get half way down the aisle to your berth the tide is half what you had, and the wind is now swirling off the land and coming from a different direction.
It's for that reason that I struggle to recommend a ferry gliding approach to that sort of berth, as what you set up out in the aisle is quite likely to be different when you arrive at the berth.
