Worst Med Mooring Ever - Just when you think you've seen everything!!

[Auspicious]

Originally Posted by Palarran

The only negative I've seen with thrusters is that invariably a crew member lets a line dangle in front of it when leaving a quay and it gets sucked in, or the motor overheats due to over use.

Also:
- significant increase in drag
- additional minor maintenance for cleaning and zincs
- major impact on storage space from the tunnel and motor and solenoids
- carbon dust from motor brushes
- RFI/EMI
- something else to break

[Dogscout]

Im waiting for the day that I am that skipper, I live with that fear. When I learned to MED moor and I have done it many times, my instructor was very emphatic about keeping enough speed to maintain helm, only using the bow thruster in a pulse to kick the bow to one side, and go slow to align then keep speed into position. I singlehand alot so I installed a remote for the windlass and I agree it will allow for a straighter alignment with the quay. The hardest thing is to stay calm.

Credit card captains are another thing entirely. They like spinning the wheel.

[Dockhead]

Originally Posted by Auspicious

Also:
- significant increase in drag
- additional minor maintenance for cleaning and zincs
- major impact on storage space from the tunnel and motor and solenoids
- carbon dust from motor brushes
- RFI/EMI
- something else to break

And worth every bit of it! At least, on a larger boat (say 50'+).



BTW a well-designed thruster tunnel with proper eyebrow produces an almost unmeasurable amount of drag.


But, you know, to each his own!

[Dockhead]

Originally Posted by Dogscout

Im waiting for the day that I am that skipper, I live with that fear. . . .

Sign of wisdom!

It may be somewhat paradoxical, but it IS possible to at the very same time have complete confidence in one's (hard-earned) skill, and yet be acutely aware of how easily and how suddenly any maneuver like that can go tarts-up. Keeps you honest.


Of course Neptune will keep you honest no matter what, so long as you are out there doing it often enough. I take some pride in my skill at difficult harbour maneuvers, but nevertheless recently made a small hash out of a berthing maneuver into German-style berth in Sassnitz, on Rügen, where you have two piles you throw stern lines onto and then bring the bow into the quay. It was blowing pretty hard right off the quay, and because there were only two of us, and the piles were very far apart (I somehow chose the superyacht berth; it didn't look so big while I was approaching it), I chose to throw a stern line onto the windward pile only and worry about the other one later.


Well, the windward pile turned out not to be. You can guess the rest. I didn't scratch anything (and haven't in years scratched anything berthing), but it wasn't pretty.

[HeinSdL]

Originally Posted by Palarran

It seem's ludicrous that there is even a discussion about the effectiveness of bow thrusters and reading the negative comments are laughable. Can you even buy a new 40+ foot boat without one? It has to add it's own value to the boats value to have one.

The only negative I've seen with thrusters is that invariably a crew member lets a line dangle in front of it when leaving a quay and it gets sucked in, or the motor overheats due to over use. But in general they are the cat's meow for you monohullers. Even a lot of cat's a jealous.

I don't think the comments were overly negative and I don't think that laughable would describe them fairly. There can be no disputing that a bow thruster is yet another piece of kit requiring proper maintenance (especially given its location on the vessel) and that to be honest for most manoeuvres on a sailing boat, you really don't need it. So in terms of pros and cons, whether to have one or not is not a done deal at all as you suggest.

Personally, I would certainly not have one, what with my ongoing campaign of ripping out all the stuff that a boat comes with these days. Either a piece of kit is essential and thus it works, or it's off the boat. And on that occasional moment where I might have liked to control the bow a bit better, well that's also a good moment to rethink what I'm trying to do.

If I was in charge of say a 60+ footer I might change my mind, but 44ft worth of plastic like my boat is not handicapped in any way due to no bow thruster.

[Auspicious]

Originally Posted by Dockhead

BTW a well-designed thruster tunnel with proper eyebrow produces an almost unmeasurable amount of drag.

Not true. That's why professionals have doors over thruster tunnels. Looked at that when specing my boat and wasn't practical.

[Dockhead]

Originally Posted by Auspicious

Not true. That's why professionals have doors over thruster tunnels. Looked at that when specing my boat and wasn't practical.

Well, I've seen the tests. I'll try to remember where I read that and find a link. There was a lot of discussion about this on the RORC forum a few years ago; most Fastnet competitors with thrusters elected NOT to rig doors over their thruster tunnels because it just wasn't worth it, even though it's a pretty simple and not that expensive thing to do while you're hauled out anyway getting the bottom polished.



The amount of drag and its impact on sailing depends on the design and location of the tunnel, the hull form and the size of the boat. The bigger the boat, the less the impact. The eyebrow is critically important, according to what I've read, as it deflects the water stream just enough to keep it from colliding with the back wall of the tunnel and creating a turbulent vortex, which is what causes most of the drag. This is fairly recent art; so your information may be out of date. It is true that typical bow thruster tunnels of the '80's and '90's were pretty horribly draggy, but modern ones are not.

All that being said, I wouldn't want a thruster on a boat of less than maybe 15-20 tonnes displacement. I don't need it at all on a say 45' 10-12 tonne boat. But once a boat gets beyond a certain size, the tricks we use to do close-in maneuvers without thrusters become less and less effective. I would simply not have a single screw boat of more than 50' without a thruster, at least one where I had to regularly do harbour maneuvers in tight conditions, ESPECIALLY Med or Baltic mooring. At the same time, the bigger the boat, the less you feel the drag, and the less any of the other drawbacks matter, so this is very much a size-dependent calculus.

[Dockhead]

Originally Posted by HeinSdL

. . . but 44ft worth of plastic like my boat is not handicapped in any way due to no bow thruster.

I agree.

[Auspicious]

Originally Posted by Dockhead

Well, I've seen the tests. I'll try to remember where I read that and find a link.

Remember that I am a naval architect. Even back in the Middle Ages when I was in school this was covered. I recall it being raised at least three times between hydrodynamics and in ship design. The "eyebrow" is far from new, at least in commercial and military hull forms. Recreational boat design always lags.

Doors are far from simple, at least remotely actuated ones. Ships use them due to the fuel savings to be gained because the drag is so high from open tunnels. They don't use them because they are pretty. *grin*

I did not miss your "tricks" post - I need some time to address that. I do appreciate your offer.

[Dockhead]

Originally Posted by Auspicious

Remember that I am a naval architect. Even back in the Middle Ages when I was in school this was covered. I recall it being raised at least three times between hydrodynamics and in ship design. The "eyebrow" is far from new, at least in commercial and military hull forms. Recreational boat design always lags.

Doors are far from simple, at least remotely actuated ones. Ships use them due to the fuel savings to be gained because the drag is so high from open tunnels. They don't use them because they are pretty. *grin*

I did not miss your "tricks" post - I need some time to address that. I do appreciate your offer.

Thruster tunnel doors which can be opened and closed remote are surely impractical for recreational yachts of less than mega yacht size. That's why God made retractable thrusters. I was talking about blanking plates, which are simple, and are used from time to time for racing.

[Auspicious]

Originally Posted by Dockhead

Thruster tunnel doors which can be opened and closed remote are surely impractical for recreational yachts of less than mega yacht size. That's why God made retractable thrusters. I was talking about blanking plates, which are simple, and are used from time to time for racing.

I'm a fan of retractable thrusters although the reliability is not great. They are prone to damage even from waterflow. The vertical "elevator" ones on Amels can be damaged by leaving them down when sailing (above 2 kts IIRC). The rotating ones as from Vetus are only slightly more robust. Running any of them aground is a disaster. Nothing is perfect. In addition the space requirement goes up significantly.

Blanking plates are fine. I have no idea why more racers don't use them. They cut toothbrushes in half to save weight and then drag the equivalent of a bucket around with them. Foolish. Perhaps owner/drivers are confident of being able to dock after a race without their thrusters and don't have any crew willing to go in the water to remove them?

[Dockhead]

Originally Posted by Auspicious

I'

Blanking plates are fine. I have no idea why more racers don't use them. They cut toothbrushes in half to save weight and then drag the equivalent of a bucket around with them. Foolish. Perhaps owner/drivers are confident of being able to dock after a race without their thrusters and don't have any crew willing to go in the water to remove them?

Well, the reason why racers rarely put blanking plates on I already said - on modern boats with well designed tunnels, blanking plates make little difference. Just read the RORC discussions about it. If it were otherwise, you can be sure racers - who as you say "cut toothbrushes in half to save weight" - would use them religiously.

[Auspicious]

Originally Posted by Dockhead

If it were otherwise, you can be sure racers - who as you say "cut toothbrushes in half to save weight" - would use them religiously.

Science is not a strong point in recreational boating. If it were people would not cut toothbrushes in half and then load on cases of beer.

[rslifkin]

Originally Posted by Auspicious

Science is not a strong point in recreational boating. If it were people would not cut toothbrushes in half and then load on cases of beer.

As much as we might all think it's stupid, I can see the logic. Get rid of all weight that isn't providing a direct benefit, but keep anything you find beneficial. I guess for some, a large quantity of beer falls into the second category.

[Dockhead]

Originally Posted by Auspicious

Science is not a strong point in recreational boating. If it were people would not cut toothbrushes in half and then load on cases of beer.

I've not seen serious racers with cases of beer on board for a race.


Those guys are by and large testosterone-poisoned (very unpleasant to share a bit of ocean with them) and hyper-competitive. If blanking plates on thruster tunnels provided a material edge I think you can be really sure that they would always be on. Those guys are always analyzing every tiny thing they can do which influences performance by even ridiculously small margins by our standards.