rudder fairing

[ebb]

Ariel rudders, are they faired to a chord from keel to trailing edge?
OR is the rudder totally flat on its two sides?

I'm inclined to make the surfaces very slightly convex - because it looks right.
But is there a case for the rudder as an extension of the keel diminishing in flat sides to a razor's edge?

They talk about modern stand alone rudders as having lift, because of their curved sides, but I don't understand how lift can happen if there are symetrical curves on both sides. Seems like turbulence would be a problem whatever the chord of the blade.

Modern rudder blades seem also to go from a rounded front to a squared off trailing edge. IE, two trailing edges. Whatzat fer?

Question is: what is the ideal shape (plan view) for an Ariel rudder?

Another kind of 'fairing'....

Question #2: Has anybody faired (or contemplated fairing) the keel to the rudder to eliminate the supposed turbulence made by the round rudder behind the squared-off keel? I think fabric has been used, tempered bronze strips, what else? Would it help to win a race.....?

[Greg]

Speaking only for myself (and Ava, of course), the trailing edge of the keel is coved around the rudder shaft. Tough to scrape paint off of, but fast as hell I suppose. A true greyhound of the seas with that smooth transition...

[Greg]

...Oh, the rudder is flat as a pancake on both sides. Parallel, I presume, too.

[Hull376]

Rudder is as flat as my bike tire was last Saturday morning on a long ride from home.

[ebb]

Inspiring phrases for the all important rudder.

Flat as a toad in the road.

[ebb]

Inspiring phrases for our all important rudder.

Flat as a toad in the road.

[Scott Galloway]

Ebb,

Grab yourself a copy of "Chapman Piloting" and go to Chapter 10, "Seamanship Under Sail" and read the section there about why boats sail. Chapman explains in text and graphic form how a rudder, and how a keel for that matter, function as foils. I just happened to turn to that section this morning for quite a different reason before I saw your post. Anyway, pretty pictures there to behold: pictures that are worth a thousand words.

[ebb]

Will do, Capt Scott, next time I can Take an Hour for Borders. Another gobbler of good ole neighborhood book stores (like WM did to the local marine stores. 'Local' B has a pretty good selection of boat books.

Chapmans seems dated about right for our boats, rounded and barndoor rudders went out of style just about the time the legendary Alberg lifted his pen from the drawing board.

Been working on 338's bronze strap constellation rudder. I'm just not going to get a pointy enough trailing edge, for me, because I committed to a very picky take-apart design that is fatter than a standard welded strap would be at the trailing edge. Though skinnier than edge bolted wood. I may finally glass the concept shut.

I'm assuming that nobody else is upgrading to the constellation shape that has a long vertical trailing edge - that is a true extension of the keel. IMCO

I would be interested to read an essay on the difference between the two in terms of boat handling and in their section design - if their sides are other than flat. Like a whale's tail.

I see fin keel boats come into the yard with skeg and stand alone rudders. The younger ones have the trailing edge of their rudders sharply blunted. Wonder if this would be a benefit on 'flat-sided' A/C keel hung rudders whatever the profile?



By the by, I have C.A.'s palimpsest drawing of the two rudders blown up on the wall. They have the same area, the triangular constellation style actually may have a little less wetted surface.

[mrgnstrn]

since i am thinking about building a new rudder, this is all very interesting.

Ebb: by constellation, do you mean the squared off looking alternate rudder drawn in the manual? why would this be hydrodynamically better? because the center of force of the rudder is farther away from the center of bouyancy (longer lever arm, greater righting moment for the rudder angle)?

(the shape is similar to some Bristols and old Cape Dory's, right?)

much grass.

[ebb]

don't know, don't know, need a fillet mignon yahht designer who can talk turkey.

Check out the Sparkman & Stephens Association Newsletter March 1998. Wear a suit and tie. Oh, and white shoes.

http://www.s-and-s-association.org/archive/mar1998.pdf

Page 3, about half way down under the title 'Brokerage'

Alberg and everybody else put them on their later full keel designs.


[I checked and couldn't get in using that address.
Try google with "constellation rudder" in quotes. You'll get that one hit.]

[mrgnstrn]

Got it!
ok, so the constellation style IS the one drawn in phantom on the lines drawing in the manual.

my gut feel is that since it puts more area lower in the water, the righting moment when heeled over is more than with the heart shaped rudder.

maybe i will put one of these on (except that i don't want to be confused with a bristol or CD).

[mrgnstrn]

this is what YAHOO told me a "constellation style rudder" was:

http://www.norwalkcove.com/mariner.htm

[ebb]

yup! thar she be! That boat looks like it would be crewed by skinny 7' basketball player types.

You notice on the Ariel phantom that C.A. couldn't help rounding off the bottom corner!


[meant to ask:
more righting moment, is this a good thing? Won't change that sweet softness we have sailing? Means better control? What?]


The CD I swear has a bigger butt than Ariel.
NObody will ever be confused!!!

[Tony G]

...rebuild the rudder? You bet. Don't you HAVE to once your in it so far? Being the rudder bearing is missing on top and I may have injured the shoe area of the keel by resting her on it, the whole rudder rebuild is a go. I never thought it would get its own thread in the discussion forum though. This will be one to watch closely.

[Bill]

Your association has just received a supply of newly minted rudder post bearings. Have not had time to post the info on the home page, but will as soon as the Webkid can get around to it.

New bearings were manufactured using the Pearson tech drawing in the manual. They come complete with the necessary "O" rings and are made from a new up-do-date, black plastic, not the stuff noted in the drawing. And, it is not the same stuff as they sell for pipe in the local hardware store.

Figure the price will be $40 plus S&S, but have not been to the USPO to get the exact postage. I'll post the info in the next week. [Note: for a single bearing, the mfg wanted $140. For two, it was $75 EACH.]