Canting mast

[san.dam]

Yes Gonzo,but I mean minimalist and EFFECTIVE. Think that we are speaking of a rotating wing mast with a chord of 1/10 of the main base. The flexible mast works well,but you are not able to adjust the rake(I think that this is in part the problem of FREEDOM) and you loose the possibility to cant the mast upwind when needed...

[SailDesign]

san.dam,
Simple. Cheap. Effective. Pick any two

You have to look at the overall definition (wrong word, but.....) of "effective". There is a corollary to Murphy's Law (Anything that can go wrong will go wrong) that applies to boats - "Anything that can break, will break."
Any added complexity to a system will make it less effective simply because it is more likely to break. Unfortunately, making complex things is much easier than making simple things to do the same job. Sad but true.
Steve

[pjwalsh]

Dick Newick designed a wingmast that could be canted to windward for the original incarnation of Ocean Surfer, a 40' ish trimaran for the OSTAR. The arrangement of this was pretty simple - the mast step was set on a large traveller car and track similar to a mainsheet traveller (made by schaefer I think). The track was part of a circle with radius equal to the distance between the hounds and step.The standing rigging was the usual two cap shrouds and headstay. The butt of the mast was controlled by a multipart tackle from each side. It wasn't very heavy or complicated and it did work.

Dick said that performance was improved when hard on the wind but not significant on other points of sail. He never mentioned using leeward cant to spill wind. His intent was to get a vertical component to the sail force or at least keep the mast vertical while the boat was heeled. Mark Rudiger who sailed her in the OSTAR did not use the feature much, and the boat proved uncompetitive due to more robust construction as compared to the rest of the OSTAR fleet that year.

When Ocean Surfer was converted to a cruising boat the canting feature was abandoned for a fixed step.

A wrinkle I just though of with this arrangement: If the butt of the mast is to leeward and the rig is a fractional sloop then the headsail/mainsail slot will become smaller because the headsail is not canted while the mainsail is. Anyone have ideas how this might affect performance?

[CT249]

What about the fact that a canted rig would actually develop downward force, thereby increasing displacement to a minor extent? Furthermore, moving the CLR out to lee further will exaggerate weather helm and therefore increase drag. Ask the guys who sail the 60' tris. They have 2.5m rams on the stays to rake the rigs back to vertical when the boats are heeled. Before they tack, they dump the ram to allow the rig to flop to leeward (it's too much hard work to pump the windward ram). The problem is that the boats develop bad weather helm when the rig drops to leeward.

Re the comment "Also, like on a windsurfer, it would provide lift." Sailboards get surprisingly little lift, generally, from their rigs and they rarely try to. Why develop lift vertically, when it costs you drag? We want to go forward, not up. Mistrals, which are restricted in rig size, try to keep the rig vertical as much as possible. This is confirmed by guys like the '99 world champ, Barcelona bronze medallist, adn our #3 Mistral sailor who was also 3rd in the 29er worlds..

FW boards do rake about 15 degrees to weather, but they are very different to boats, having massive rigs and not sailing in light winds.

The surprising thing is that boards, which could rake to windward and could keep their hulls flat, normally try to keep the rigs vertical and heel the hulls!

The idea of a leeward-canting rig, by the way, is so old that it appeared in an "Ancient Interface" symposium article about "early sailboat patents". The reason it hasn't caught on is that sailing fairly level (skiffs and some Laser sailors know windward heel is good) is fast. Gee, how strange that doing what the gold medallists do (sailing flat) actually works!

Boards don't get much lift from their rigs. Mistral sailors try to have the

[san.dam]

What Steve said about the breaking risk, is in true the thing that has screwed my mind... But,steve, you have to know that the boat is (just for the first issue) only a 28 ft and 700 kg. On these dimensions the matter become sligthly easier... As you said,the break is ever around the corner, but I have put in balance that almost two masts will be done.
I guess a little bit of confusion here,somebody talk about canting mast on a multihull, as the Newick or others, but I think we can not to do a paragon between multi and mono... The positions of the centres(sails and apendages) are different,and even the ratio between respective surfaces. Are you sure that the cant to windward allows,in the global equilibrium of the forces,to some kind of lift( say a displacement reduction)?
Perhaps this happens on multi,wich have great stability,low displacement and fins very small and asymmetrical..
It is true,the reasoning that canting up we have some lift is intuitive,but... the surfboard,how can you to stand on the table against the sail force if you do not cant? It seems to be a must.
The shift of the sails centre off of the symmetrical plan(to lee) is the core.

[pjwalsh]

san.dam,

I don't think the situation re: a canting rig on a monohull vs. a multihull is really all that different at least in a qualitative way. Sure, a mono will have less initial stability and possibly different foil locations and areas than the multi, but you are still talking about optimizing the attitude of the rig for varying angles of heel and points of sail - in the big picture the idea is similar in spite of the possibility of differing details in terms of degree of cant and location of underwater appendages.

I think it is quite probable that canting the rig to windward will result in an upward component of force on the rig. This because the wind pressure on the mainsail is acting normal to the surface of the sail at each area element. If you sum up all the forces acting on each area element of the sail the resultant will be very likely be upward in the windward canted case. Conversely if the rig is canted to leeward there will probably be a component of downward force.

(edit: Also, the leeward movement of the center of sail force will likely cause more weather helm in the mono than in the multi case - for the multi the drag of the leeward hull will cause a counteracting moment - in the mono the beam of the hull will be less and so the counteracting moment.)

Another post described the idea of changing the length of the transverse staying to accomplish the mast cant. An advantage I can see for this is that the relative position of the headsail luff and mainsail leading edge will remain at constant relative position. However, the act of tacking with the mast vertical then, pulling the loaded windward shroud in seems to me to be fraught with danger in terms of keeping the rig standing relative to the approach of allowing the butt of the mast to go to leeward.

(edit: I see on rereading CT249's post that they actually tension the lewward shroud THEN tack - seems perhaps less dangerous then)

It just now strikes me that an older way to accomplish full adjustability of the attitude of the sails relative to heel angle and point of sail is by the use of the lateen sail. Of course any way you cut it the additional degree of freedom represented by any of the solutions suggested results in the issue of needing to control it. The characteristic in common will all three arrangements is some increased difficulty and danger in tacking or wearing the ship.