Search found 503 matches

by Bill Roberts
January 16th, 2019, 10:43 am
Forum: Technical Forum
Topic: Righting a SC15, Parts, and Repairing
Replies: 19
Views: 8641

Re: Righting a SC15, Parts, and Repairing

I just came up on this forum item by accident. I have never read such a misunderstood, misused and abused righting system in my life. Also people are giving advice that is wrong and or omitting important points. It makes me wonder, why did I design a mast raising and lowering system and righting sys...
by Bill Roberts
December 16th, 2018, 9:29 pm
Forum: Technical Forum
Topic: spinnaker, CE, and attitude
Replies: 11
Views: 3432

Re: spinnaker, CE, and attitude

havliii You are welcome for the discussion. The mainsheet load travels up the leech of the main sail to the head of the sail where it is handed off to the mast at the halyard lock. Then this load travels down the mast and is added to the other vertical loads at the hounds. If the mast is rigged with...
by Bill Roberts
December 14th, 2018, 10:59 am
Forum: Technical Forum
Topic: spinnaker, CE, and attitude
Replies: 11
Views: 3432

Re: spinnaker, CE, and attitude

havliii, The compression loads coming down the mast come from the rigging, the wires. All of the rigging wires connecting to the mast at the hounds are in tension, especially when sailing. All of these tension loads have vertical components and they are delivered to the mast at the hounds with the e...
by Bill Roberts
December 10th, 2018, 12:00 pm
Forum: Technical Forum
Topic: spinnaker, CE, and attitude
Replies: 11
Views: 3432

Re: spinnaker, CE, and attitude

Hi havliii, You are educating yourself and that is good. I point out that on high performance boats the spinnaker is usually trimmed in close. That is because the boat goes faster on a beam reach initially and then the boat accelerates which bends the relative wind forward and now you are sailing wi...
by Bill Roberts
December 9th, 2018, 8:23 am
Forum: Technical Forum
Topic: spinnaker, CE, and attitude
Replies: 11
Views: 3432

Re: spinnaker, CE, and attitude

havliii Pitch, yaw and roll describe the three types of motion of a yacht, the dynamics of a yacht's movement about its three major axes. Something to think about: let's consider a mainsail and keep in mind that the force from a sail is always perpendicular to the sail cloth. When normal sailing a m...
by Bill Roberts
December 7th, 2018, 12:16 pm
Forum: Technical Forum
Topic: spinnaker, CE, and attitude
Replies: 11
Views: 3432

Re: spinnaker, CE, and attitude

haviii, For this discussion, think of this headsail as a flat plate, tack to head to clew. That flat plate has a resultant force perpendicular to its surface at the centroid of the flat plate. This resultant force is made up of three component forces. One component force is sideways. Another is forw...
by Bill Roberts
December 6th, 2018, 10:33 am
Forum: Technical Forum
Topic: spinnaker, CE, and attitude
Replies: 11
Views: 3432

Re: spinnaker, CE, and attitude

havliii, Remember that the force from a sail is perpendicular to the sail cloth. Therefore if a spin or gen is leaning aft from the side view and inward at the head from the front view of the boat, then there will be some vertical lift from these flattish cut sails. These sails are made/shaped to pr...
by Bill Roberts
November 17th, 2018, 4:38 pm
Forum: Technical Forum
Topic: Solo righting a SC 17
Replies: 5
Views: 2570

Re: Solo righting a SC 17

I read these descriptions of trying to use the righting system on any SC and I don't hear anyone say they !. opened the shroud lever and 2. pulled the pin that extends the shroud. Then and only then can one person right the boat. Opening the shroud lever does nothing to help the geometry of righting...
by Bill Roberts
November 12th, 2018, 4:01 pm
Forum: Technical Forum
Topic: New Question, What foredeck shape makes the least drag?
Replies: 5
Views: 2192

Re: New Question, What foredeck shape makes the least drag?

Hi Folks, I saw a Nacra 15 the other day and the foredeck shape for all functional purposes is the same as the SC 15. The N15 foredeck is made up of three flat surfaces that would be tangent to the elliptical foredeck of the SC 15. How about that, we have Marino and Melvin coping the 30 year old SC1...
by Bill Roberts
November 1st, 2018, 8:02 pm
Forum: Technical Forum
Topic: New Question, What foredeck shape makes the least drag?
Replies: 5
Views: 2192

Re: New Question, What foredeck shape makes the least drag?

Hi T. Peterson, It looks like you and I are the only ones interested in foredeck aerodynamic drag. With air, a smooth continually curving surface is low drag from the aerodynamic point of view. Centerline ridges and corners are a no, no. An external hull to deck flange is draggy. It traps the airflo...
by Bill Roberts
October 31st, 2018, 10:14 am
Forum: Technical Forum
Topic: New Question, What foredeck shape makes the least drag?
Replies: 5
Views: 2192

Re: New Question, What foredeck shape makes the least drag?

The bow is formed at the intersection of the sides of the hull at the front end of the boat. That intersection is called the stem. The part of the bow that I am referring to is where the bow and the deck intersect. It could also be called the top of the stem. To catamaran sailors, it is that part of...
by Bill Roberts
October 30th, 2018, 8:07 pm
Forum: Technical Forum
Topic: New Question, What foredeck shape makes the least drag?
Replies: 5
Views: 2192

New Question, What foredeck shape makes the least drag?

In the past several years we have seen all sorts of shapes on fore decks. The foredeck shape makes aerodynamic drag while normal sailing. 1. Consider the wind flowing perpendicular over the hull upper half and deck. sideways to the wind. 2. Consider the wind flowing over the top half of the hull and...
by Bill Roberts
October 29th, 2018, 9:33 pm
Forum: Technical Forum
Topic: Strong Bows VS Weak Bows
Replies: 2
Views: 2813

Strong Bows VS Weak Bows

Hi Folks,
I can't resist comparing these two pictures.
A picture is worth a thousand words.
by Bill Roberts
May 8th, 2018, 5:57 am
Forum: Technical Forum
Topic: One more Squaretop vs pinhead question
Replies: 5
Views: 3225

Re: One more Squaretop vs pinhead question

I'm not sure I understand your question. I think you are talking about a pinhead SC20 mainsail. You are suggestion coming down the luff at the head 2 ft and cutting the sail across to the leech to form a square top sail. Then you ask what is the difference in foot length between a pin head sail and ...
by Bill Roberts
April 29th, 2018, 1:07 pm
Forum: General Discussion
Topic: Food For Thought
Replies: 0
Views: 4763

Food For Thought

Foiling Boats, talking about foiling sailboats: A sailboat is a vessel for travel across water that is powered by the wind acting on sails. The vessel travels across water either in the displacement mode or a planing mode. What is a device correctly called that flies above the water using sails or w...