Search found 503 matches

by Bill Roberts
September 26th, 2016, 9:43 am
Forum: Technical Forum
Topic: Lowest Aerodynamic Drag Foredeck/Hull Shapes
Replies: 6
Views: 7467

Re: Lowest Aerodynamic Drag Foredeck/Hull Shapes

Drew, The most commonly used sales point for selling sailboats is the "RACER CRUISER". My point is that the 27 and 30 can do both jobs very well. The 27 and 30 are excellent Racer Cruisers. You don't have to fill the tramps up with people every time you go out, just take one or two couples...
by Bill Roberts
September 20th, 2016, 10:48 am
Forum: Technical Forum
Topic: Lowest Aerodynamic Drag Foredeck/Hull Shapes
Replies: 6
Views: 7467

Re: Lowest Aerodynamic Drag Foredeck/Hull Shapes

Hi TP', Thanks for your comments. The 27 and 30 are totally different boats from the 15 thru 22. They are aimed at a totally different market. These two boats have two large tramps; lots of room. Therefore they can carry several people at one time. These two boats are excellent day sailing boats. Th...
by Bill Roberts
September 19th, 2016, 8:11 pm
Forum: Technical Forum
Topic: Lowest Aerodynamic Drag Foredeck/Hull Shapes
Replies: 6
Views: 7467

Re: Lowest Aerodynamic Drag Foredeck/Hull Shapes

HEY, WHAT'S UP? Where are the comments? Here's what I have heard from A cat World Class Sailors. They see no difference in speed sailing to windward. Downwind the boat is much harder to sail----- prevent/avoid pitchpole. Aerodynamics: Suppose we had a shape of 1 cubic foot, 1 ft by 1 ft by 1 ft with...
by Bill Roberts
September 17th, 2016, 8:49 pm
Forum: Technical Forum
Topic: Lowest Aerodynamic Drag Foredeck/Hull Shapes
Replies: 6
Views: 7467

Lowest Aerodynamic Drag Foredeck/Hull Shapes

Foredeck shapes? Has anybody seen any test results, real data, numbers, that show or prove there is a boat speed advantage associated with downward sloping foredecks. I've heard talk that there is less aerodynamic drag. Most of these deck downward sloping foredecks that I have seen have an outstandi...
by Bill Roberts
September 11th, 2016, 3:21 pm
Forum: General Discussion
Topic: Looking for help on a telescoping trailer
Replies: 7
Views: 8310

Re: Looking for help on a telescoping trailer

Drew, These pictures are of someones home spun idea of how to build a telescoping trailer. This is all junk. The rollers have to be steel or aluminum. The inner, moving beam, must be moving on rollers at all times. At the outlet of the fixed half of the telescoping system there must be a roller abov...
by Bill Roberts
September 6th, 2016, 9:35 pm
Forum: General Discussion
Topic: Looking for help on a telescoping trailer
Replies: 7
Views: 8310

Re: Looking for help on a telescoping trailer

Here we go again. `1978 factor telescoping trailer. Cost then was $2500, cost today $5000. Telescoping in or out was controlled by a continuous cable thru both beams. Movement out and in was always in concert, never jammed. Set up time was 15 minutes from 8 ft wide to 12 ft wide with tight tramp. Co...
by Bill Roberts
September 5th, 2016, 1:46 pm
Forum: General Discussion
Topic: the golfball effect
Replies: 2
Views: 4782

Re: the golfball effect

The golf ball moving through the air presents a unique problem. The ball is going 100 mph plus and the curvature around the ball is quick. The air cannot stay attacked to this short radius object at the speeds it normally travels. The dimples are on a golf ball to keep the airflow attached to the ba...
by Bill Roberts
September 3rd, 2016, 8:40 am
Forum: General Discussion
Topic: Dagger boards versus shared lift
Replies: 35
Views: 32056

Re: Dagger boards versus shared lift

Glad to help, Drew. You are right, shared lift is just another way to balance the CE and the CLR. The equation of max hull speed equals 1.4 times the square root of the LWL applies to keel boats and power boats. It does not apply to high fineness ratio hulls like beach cats. Power boats overcome thi...
by Bill Roberts
September 2nd, 2016, 8:39 pm
Forum: General Discussion
Topic: Dagger boards versus shared lift
Replies: 35
Views: 32056

Re: Dagger boards versus shared lift

Drew, The top speed limit on beach cats is pitchpole. Here's the situation, The forward sail thrust acts at the sail center of effort about 10 to 15 ft above the water depending on the size of the rig. The hull drag occurs about 6 ins below the surface of the water. The forward sail thrust and the h...
by Bill Roberts
September 1st, 2016, 6:48 am
Forum: General Discussion
Topic: Dagger boards versus shared lift
Replies: 35
Views: 32056

Re: Dagger boards versus shared lift

Drew, I don't mind if you change the design, just change it for the better.
by Bill Roberts
August 31st, 2016, 12:55 pm
Forum: General Discussion
Topic: Dagger boards versus shared lift
Replies: 35
Views: 32056

Re: Dagger boards versus shared lift

Drew, If you had taken a course in school on basic aerodynamics, you would understand all of this. The part of the centerboard drag that you are missing is the induced drag, the drag due to making lift part. The total CB drag equals the parasitic drag plus the induced drag. The parasitic drag, frict...
by Bill Roberts
August 29th, 2016, 8:20 pm
Forum: General Discussion
Topic: Jib Barber Hauler system SC 20
Replies: 11
Views: 10462

Re: Jib Barber Hauler system SC 20

Dan, the SC20 jib sheeting system is superior to the self tacker with no spinnaker. The barber hauler system will let you trim the sail for sailing close haul perfectly and it will let you trim the sail perfectly for sailing off the wind adjusting the barber hauler out. The self tacker, straight tra...
by Bill Roberts
August 29th, 2016, 7:15 pm
Forum: General Discussion
Topic: New Sails - Help, Tom!!??
Replies: 10
Views: 9410

Re: New Sails - Help, Tom!!??

Dan, colored sailcloth is fine. It does not have the strength of white cloth. The max strength of sailcloth is not tested until you are sailing in strong winds and max righting moment. The sailcloth is not going to tear. It is going to stretch with many repeated uses in heavy air. The leech will str...
by Bill Roberts
August 29th, 2016, 5:47 pm
Forum: General Discussion
Topic: Generic Sails
Replies: 4
Views: 6093

Re: Generic Sails

Dan, You have equal fractions of the jib sheet tension in the foot and leech of the sail when a line extension, a straight edge, of the slope of the jib sheets as they approach the sail are extended onto the sail and this line on the sail bisects the clew angle. Then 50% of the jib sheet tension goe...
by Bill Roberts
August 28th, 2016, 11:23 am
Forum: Technical Forum
Topic: Square Top vs Pin Head
Replies: 25
Views: 24790

Re: Square Top vs Pin Head

gahamby, good to hear from you. The knuckle at the bow is the intersection of the stem and the keel. So you have it right. Keep those blue stripes at the bow just underwater on all points of sail and in any wind condition and you will have the hull trim just right. In light winds, you will be sittin...