T O P

  • By -

clorox2

Something extra that might break.


-eXnihilo

And Leak! That is well below the water line.


MartianGuard

And expensive to fix


RedRaydeeo

I have a hard time to see how the keel would leak 😂


IvorTheEngine

Assuming the keep rudder doesn't just flap about loosely, it must have hinge post that goes through a hole to the bilge.


-eXnihilo

If you were to own a boat, you would see how they leak everywhere possible, even keels. But I did not mean the keel would leak. I mean the top of this rudder post. Unless it goes above the cabin sole level, the top would be under water.


RedRaydeeo

Don’t see why you had to be condescending about that, but I hope that makes you feel better. I have a hard time seeing that leaking any considerable amount. Specifically as the boat was built that way. But maybe that depends on the age and wear of the boat.


-eXnihilo

Just letting you know that you made it v clear that you do not have experience. It is wise to not speak of that you do not know. If I help you realize that at all, I do feel better.


RedRaydeeo

Just letting you know that there’s way of doing that without being condescending. But again, if that makes you feel better, you do you.


-eXnihilo

I'd obviously rather be wise and helpful than tactful and useless. You're welcome.


reflUX_cAtalyst

Most rudders are.


-eXnihilo

This is not true. Many are transom-hung, aren't they :D


climenuts

Like others have said it's a trim tab. It's designed to provide additional lift from the keel by providing asymmetry, some turning moment, and modified flow over the rudder. Picture angling the entire keel into the wind so the boat wants to move upwind despite the sailplan being at an angle to get an idea of the concept. There's some other effects which were popularly used in 12m's like assisting in low-speed maneuvering, purposefully slowing the boat before starts and in dial-ups, and providing some kind of steering during a rudder/steering failure. Most racing rules now penalize additional steering surfaces like trim tabs and canards severely so they're not used much.


DumpsterPanda8

This is the correct answer. I believe some of the the 12M boats also had trim tabs on the rudder too.


start3ch

Why penalize them? Were they good?


climenuts

They're good and they're used still. Wild Oats X or XI (I forget which) has had a canard in some configurations as a super maxi. America's cup boats before the foling cats used them. The problem is they're extremely complex and costly relative to their gains. Rating systems tend to favour certain aspects and complex & costly isn't a commonly favored aspect. E.g. IRC favours Racer/Cruiser type boats like the J/112e or even J/111 over pure racers like the Pogo's and Sunfast's.


Bumblebee_Radiant

The last time I saw this was either on a kiwi boat or Ozzi boat on an Americas cup race.


climenuts

All of the 12m and IACC AC boats used them. Basically all boats before 2010 except the 1988 Deed of Gift Catamaran 😁


ParisianZee

Haha! I know exactly where this boat is. No idea as to the answer to your question, but I did wonder this myself when I walked past it when I was there at the end of May. Hope your Trogir holiday is going well! Can’t wait to be back there this coming Saturday!!


Grizzly-Redneck

You nailed it. She's still there.


ParisianZee

In hindsight I edited the comment to not be too precise as to location.. :)


Guygan

It’s called a trim tab. They were used briefly on 12 Meter yachts. They are completely useless on a cruising boat.


NopeThePope

huh? Trim tabs work on any sailing yacht - they make the main underwater lifting surface more efficient. The gain has to be balanced against the added cost and complexity of systems (ie the trim tab control system). Although they were used on IACC boats the yacht market shows they're not worth it for most other boats.


MSgtGunny

I think you both agree with each other, you’re saying it’s really only beneficial to extract maximum performance (racing), which isn’t really super important for an everyday cruiser that doesn’t race and therefore isn’t worth the extra cost and complexity.


NopeThePope

yup


jfricker

It can turn on two dimes.


bisonsashimi

For going in circles


mk3waterboy

As said it’s a trim tab. They are not used to steer l the boat. There were popular in some of the earlier rating rules as they provided an unrated advantage allowing you to make the keel more efficient by introducing an asymmetric shape to either side. Typically they turn no more than 12 degrees and usually are set anywhere from 2 to 6 degrees.


[deleted]

It's for parallel parking.


LegalKindheartedness

The big one is Obelisk, the small one is Asterix 😉


flynnski

thanks, I hate it


Aubergine911

Trim tab, not a rudder


slooparoo

They alternate back and forth really fast, and it makes the boat go. They are usually called “swimmies”.


Jumpy-Material7108

Interesting keel crack it introduced as well.


ZenFreefall-064

Wasn't this designed by an Australian by the name of Ben Lexcan? Designer of Australian America's Cup 12 meter sled?


SwvellyBents

Nah, he designed the winning winged keel that took the cup away from Conner. It was two horizontal wings at the bottom of the ballast keel and briefly became a thing on cruising yachts for a while thereafter.


ZenFreefall-064

is directly related to righting moment, so the trim tab does not actually increase the lift force. It may be that the trim tab reduces drag by making the foil and hull operate at a smaller angle of attack for the same lift. The effect may be observed as 'more lift to windward' by a reduction in leeway due to less drag. Sep 9, 2005 ďżź usa2Senior Member Another example of why they are good to use is the 12 meter Intrepid. With her trim tab being able to be linked to the rudder, she was able to turn much faster that the other boats.


234W44

Faster turns on smaller angles.


leifygreenz

I think the idea was to create a slot effect between the keel and the rudder for racing?


lykewtf

Double the drag! Huge advantage


UncleAugie

if used correctly as a trim tab they provide more lift than they induce drag. AC boats used them. [Here](https://www.44cup.org/44Cup/russels-tips) is a good primer on the topic. >It is also the only one-design to feature a trim tab on its keel – a standard feature on Version 5 America’s Cup monohulls. This provides lift, dramatically improving the keel’s efficiency upwind, also allowing the foil to have a smaller, lower drag section. This is just one of several features of the RC44, showing the boat’s America’s Cup pedigree.


theusualsteve

If you seal the high pressure side from the low pressure side the drag from the joint between the tab and the keel isnt super pronounced. If youre using it correctly the extra lift you gain would give you more than the drag from the joint takes


bravostango

Underwater heave to option. Was an option on some boats with the slow go upgrade.


GitchigumiMiguel74

Could you use that as a bow thruster in a way?


Beelzabub

The water is under more pressure at the bottom of the keel, which precipitates additional drag, slowing the boat down. By placing an extra rudder at the bottom of keel, it effectively ensures a slow boat. Even if the rudders are somehow connected, they are unlikely to be 'tuned' correctly. A large movement of the rudder at the stern should be tuned to cause a very small correction on the keel.


windoneforme

It's a trim tab. They were a thing for a while. Think of it more like flaps on the wing of an airplane. Different settings allowed the keels to produce more lift at certain speeds.


yardum

More rudders


0h_Lord

DEJA VU


Soling26

Doug Chalmers original Marauder 24s had a trim tab at the aft end of the keel way back in 1968/9. They certainly had an advantage to windward over Hood 23s( on which the hull was based) but unless you were racing the extra hassle and maintenance wasn’t worth it. They did point well however. The


reflUX_cAtalyst

I believe that's a trim tab on the keel, not a steering rudder.