Search found 503 matches

by Bill Roberts
December 9th, 2003, 8:25 am
Forum: Technical Forum
Topic: NACA Foil Sections Continued (Was "Bill Roberts")
Replies: 6
Views: 7824

Hi Thom, I think those race results speak for themselves. The Smyth boat was faster. Local knowledge: This is something that exists sailing on lakes and rivers due to land contour around the body of water. In the ocean the closest thing to local knowledge is high and low tide time and that is publis...
by Bill Roberts
December 8th, 2003, 2:54 pm
Forum: Technical Forum
Topic: NACA Foil Sections Continued (Was "Bill Roberts")
Replies: 6
Views: 7824

Hi Thom, What I see in your picture is a swept back and curved aft rudder leading edge. This geometry leads to ventilation at high speeds, 20mph + . Of course if the boat never goes that fast, ventilation is no problem anyway. There were several F boats here in Stewart this weekend and I noticed fen...
by Bill Roberts
December 8th, 2003, 8:54 am
Forum: Technical Forum
Topic: NACA Foil Sections Continued (Was "Bill Roberts")
Replies: 6
Views: 7824

Thom, The NACA foil sections specify the foil cross section only, the thickness distribution. The plan form, length and width or span and chord, are whatever your class requires underwater. I'm not sure what you mean by 'underslung'. Does that mean with a large knotch cut back into the leading edge ...
by Bill Roberts
December 7th, 2003, 8:36 am
Forum: Technical Forum
Topic: NACA Foil sections
Replies: 3
Views: 4245

Thom, The NACA foil sections are described in terms of % chord, 0 to 100%, and the thickness or the half thickness is described in therms of % chord also. There are no drawings of a specific size. What is provided is dimensionless and allows easy scaling to any chord dimension desired. The 63 series...
by Bill Roberts
December 7th, 2003, 8:16 am
Forum: Technical Forum
Topic: Crew Of 3
Replies: 12
Views: 9800

Thom, The ARC products designed for three and or four person racing are the RC27 and RC30. The 27 is the three men or two couples, racing boat. The 30 is designed with 500 pounds more displacement in the hulls than the 27 so that it can be used for cruising, carrying outboard motor, fuel, bimini top...
by Bill Roberts
December 7th, 2003, 7:02 am
Forum: Technical Forum
Topic: Crew Of 3
Replies: 12
Views: 9800

Thom, Two things are being coordinated here with the forward swept leading edge foil. First, 'ventilation' is being eliminated, does not happen. This applies to dagger boards as well as rudders. Second, the rudder is becoming balanced. About 20% of the rudder area is in front of the axis of rotation...
by Bill Roberts
December 6th, 2003, 4:34 pm
Forum: Technical Forum
Topic: Crew Of 3
Replies: 12
Views: 9800

Thom, The entire SC product line,1978 through 1980, of ARC catamarans was designed for sailing off the SE coast of Florida in the Atlantic ocean. The chop here is 2 to 3 feet summertime and 3 to 4 feet winter. This adds 6 to 8 inches of additional hull height to the normal beach cat designed for lak...
by Bill Roberts
November 19th, 2003, 7:18 am
Forum: Technical Forum
Topic: Ackerman Steering Compensation For Catamarans
Replies: 0
Views: 7673

Ackerman Steering Compensation For Catamarans

Hello Catamaran Sailors, Here's the Ackerman steering compensation story. When our catamarans make a turn, like tacking for example, the hulls follow curved paths. The hull in the inside of the turn is making a sharper turn , turning on a path with a shorter radius of curvature, than the hull on the...