Association Forum - Rudder Drag

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Rudder Drag

New Topic

Topic Locked

Printer Friendly

Author

Topic

Mark Maxwell
Captain

Member Avatar

USA
329 Posts

Initially Posted - 10/10/2001 : 12:49:56

I've been following the post about the new balanced rudder and that it may cause more drag than the older style. I may be wrong but the way I see it is that rudder drag is the effect of the blade being moved to create low pressure on one side and high pre

Edited by - on

Douglas
Master Marine Consultant

Members Avatar

1595 Posts

Response Posted - 10/10/2001 : 22:14:19

Might be true on an aircraft but not a boat. Not enough to notice anyway. When you turn the rudder to one side its not lift or lack off that turns the boat its sheer water pressure on the side of the rudder and the direction the water i deflected to.

Edited by - on

eric.werkowitz
Captain

Members Avatar

USA
283 Posts

Response Posted - 10/11/2001 : 00:09:35

Douglas,

We've had this debate in the past without resolution. But, if no lift is generated in water, why do boat builders waste time, effort, and rudder strength by fashioning them with a foil design instead of a flat, round-edged slab?

Eric Werko

Edited by - on

n/a
deleted

Members Avatar

26 Posts

Response Posted - 10/11/2001 : 11:19:53

Eric,

Good question. Is there a marine engineer out there who can give us a quick dissertation on the subject?

George Seaborn #1190

Edited by - on

Douglas
Master Marine Consultant

Members Avatar

1595 Posts

Response Posted - 10/11/2001 : 13:30:07

1) It wouldn't look good if it was shaped like a door.
2)Yes there is some drag that is eliminated but unless you are racing and realy into the big buck racing it doesn't make a lot of diferance.
3)I am in Aviation and for something that small to gener

Edited by - on

Dave Seely
1st Mate

Members Avatar

46 Posts

Response Posted - 10/11/2001 : 14:12:15

I'm not a marine engineer but I am a mechanical engineer with some fluid flow experience and I think I can explain a few thinks.
Whether a rudder is balanced or not has nothing directly to do with drag. A foil (the rudder in this case) using a NACA00 p

Edited by - on

Brian G Smith
Deckhand

Members Avatar

Canada
4 Posts

Response Posted - 10/11/2001 : 19:26:10

Having owned the 1980 rudder and then built a balanced rudder for the C25 I can attest to its qualities. The balanced rudder places the leading edge forward where it should have been to begin with. Hence not only is the rudder more balanced on its pivot i

Edited by - on

eric.werkowitz
Captain

Members Avatar

USA
283 Posts

Response Posted - 10/11/2001 : 22:44:17

To Douglas and Dave,

You both mentioned that a rudder foil is symetric and that the symetry differentiates it from an aircraft wing in regards to lift. The implication being that the air flowing over both sides goes the same distance and, therefore,

Edited by - on

Dave Seely
1st Mate

Members Avatar

46 Posts

Response Posted - 10/12/2001 : 09:08:13

Your argument about the flow paths being different lengths is correct but would you call this lift from the profile of the foil or would you say that it creates lift due to the angle of attack more efficiently than a thin flat plate? Your argument could a

Edited by - on

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2984 Posts

Response Posted - 10/12/2001 : 18:33:33

When comparing fluid dynamics... there is considerable differance between the effects of water and air. A good example of this is the effort required to balance the helm. While considerable adjustment is needed on the sails, mast rake, etc. (which have

Edited by - on

eric.werkowitz
Captain

Members Avatar

USA
283 Posts

Response Posted - 10/12/2001 : 19:28:39

Dave,

In re to your question about the 2x12 with a rounded nose, I would say the thick trailing edge would add some uncertainty (and turbulence) to the path lengths. The result would be what Arlyn notes as a poor lift to drag ratio.

I believe the r

Edited by - on

Dave Seely
1st Mate

Members Avatar

46 Posts

Response Posted - 10/13/2001 : 22:20:54

Eric, Actully its called Magnus lift. Corriolis force or the corriolis effect has to do with the trajectry of objects within a spinning refferance frame. Try www.howstuffworks.com/airplane4.htm for an explination of magnus lift. I shouldn't have even bro

Edited by - on

eric.werkowitz
Captain

Members Avatar

USA
283 Posts

Response Posted - 10/14/2001 : 14:24:25

Dave,

Yeah, Magnus effect. Some company was trying to build an airship that used the Magnus effect to controll it lift without using ballast. Don't think they made it.

In re to rest of thread, I've exhausted my knowledge (probably some time ago)

Edited by - on

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.