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deep rudder wanted

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frfletch View Drop Down
Commodore
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Joined: 13 May 2008
Location: Canada
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Post Options Post Options   Thanks (0) Thanks(0)   Quote frfletch Quote  Post ReplyReply Direct Link To This Post Posted: 22 October 2014 at 11:00pm
On any given foil, its shape is determined by specific numbers of the half section. Lets take a common foil (wing) that is a straight taper. If a straight taper, one only needs the exact shape of the base (say top of keel) and the shape of the bottom (say foot of keel). For fun, lets assign 10 measurement stations to each starting at the leading edge. Lets space each of them in 10% increments from the leading edge. Most of our sailing foils have their fullest sections about 40% back from the leading edge. If one drew s center line from the center of the leading edge to the center of the trailing edge, then the half values are the distance from the center line to the outside of the foil at each measurement station. So, when shaping a foil with a straight taper, one makes a template (female) that goes over the foil to be shaped with each measurement station marked on each side. He also makes a solid foil shape for the foot and attaches it to the foot of the foil to be shaped. Then one just trims the material between the measurement stations using a straight edge. I number each station say 1-10 or whatever, then use a piece of 1 1/2' x 1 1/2" aluminum angle as the straight edge. If it is hollow I fill it. If it is proud, one sands it off.

When making a foil from scratch, I use foam and a hot wire strung tight on a bow tensioned by Spanish windlass. This is attached to 12V DC or AC. A car battery with jumpers works fine. Then with one person each side of the bow, set the hot wire down on measurement station zero, and progress it. I call out the station from the leading edge position such as zero, one half, one, one and a half, two, etc, and ask the trailing edge person to keep up.   When done, you have a near perfect foil. I first used this process is building model airplane wings. With a straight foil, or a straight tapered foil, one only needs two patterns. Top bottom, or with a wind, inside and wingtip.
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WJRyan View Drop Down
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Joined: 12 February 2008
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WJRyan Quote  Post ReplyReply Direct Link To This Post Posted: 22 October 2014 at 8:59pm
Silly question but what is an offset?   
Bill Ryan,

Room4Crew, #155
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frfletch View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote frfletch Quote  Post ReplyReply Direct Link To This Post Posted: 22 October 2014 at 6:15pm
No progress yet. I can modify, etc, but that would definitely increase the drag bucket. I have no trouble making the rudder if I can get the offsets. Farr provided me with offsets to the keel, but they would not release the rudder details.
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fatjohnz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatjohnz Quote  Post ReplyReply Direct Link To This Post Posted: 17 October 2014 at 9:59am
Interesting; did you make any progress on this fletch?
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frfletch View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote frfletch Quote  Post ReplyReply Direct Link To This Post Posted: 21 September 2014 at 10:48am
Ah yes! But was it faster? I remember it being said that the deep rudder option while deeper, provided no additional wetted surface or drag. To achieve that would require that it was either thinner, narrower, or both.
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Mad Max View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mad Max Quote  Post ReplyReply Direct Link To This Post Posted: 21 September 2014 at 10:29am
Many years ago I also looked for the deep rudder, found one but didn't want to part with the money.  Talking to Bill he mentioned the cheap way would be extend the original which I did.  I made a female mold of the tip and cast a new foot.  The rudder was extended 4'5 inches and all lines fared to match the original.  I don' know if this would be accepted as a class deep rudder but it made a major difference in the handling of the boat.

Dick
Dick #122
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frfletch View Drop Down
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Joined: 13 May 2008
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Post Options Post Options   Thanks (0) Thanks(0)   Quote frfletch Quote  Post ReplyReply Direct Link To This Post Posted: 19 September 2014 at 6:51pm
Does anyone have have a Laser 28 deep rudder that they would like to sell? Please let me know if so.

Thanks.
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