New A Class Catamaran Rig: Square Top Jib

[Doug Lord]

Originally Posted by petereng

Jib on A=Class
Anyone who does the research and the maths without two much digging will find that the jib is not the way to go. Even from a trimming point of view he'll be flat out trimming main and jib losing time for tactics and getting his head out of the boat. But he may have a balance problem and since he can't move the mast fwd this is a solution. Not the ideal but a solution. Don't be too critical of these things they will easily work/notwork on the racetrack. Cheers Peter S

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Peter, from what I've read thru the bs on Sailing Anarchy, Smyth has convinced himself that you are right.

Some thoughts:
-- If he had a balance problem,he could move the daggerboards forward which would help in a number of ways particularly if he was using lifting foils. Pioneered on the Arc 21 and maybe others. Bill Roberts uses his concept of "shared lift" on the Arc 21 which places the daggerboard(smaller than usual) forward of the front beam. http://www.aquarius-sail.com/catamarans/arc21/index.htm
-- The designer of the Swift Solo(singlehanded Skiff) came up with an excellent sheeting system that allows the main and jib to be trimmed with a single sheet. Has a "relativity control" that allows the slot to be adjusted. I used it on my boat and it works well.

click on image:

[petereng]

Yes I've admired that system and would do it next time I had a small dinghy suitable, but onward to Wings! Re: Arc21 - we catamaran sailors have not explored properly underwater foil configurations. There is a lot of scope for canard type fwd foils for windward control and tacking ease. But usually the damn rules are written to restrict controlled surfaces and number of surfaces. Image if Boeing had rules that they can't have trim tabs on their rudders! or no airolons on their wings? We now have situations in various classes where we allow banana boards which are very expensive and fiddly and not much better than straight boards yet they were created to get around the max width rules. If we said the max width was only on the hull then we could use an easy straight board to acheive the same thing. Its about time we let physics and good engineering develop boats and get away from prescriptive rules. Peter

[petereng]

Gary Baigent - By "4 element" do you mean 4 elements or two elements each with flaps? A proper multielement 4 element rig will give huge lift and would need to be much smaller than the current AC72 wing profile would allow, interesting when teams would start asking to use smaller "sails". But what a mechanical beast that will be but its the future. Peter

[Gary Baigent]

hi Peter, well, that was just me looking too far ahead - I'm thinking, once the AC72's get bored with their 2 element rigs, real sophistication will appear - meaning 3 element rigs, like Lindsay Cunningham C Class designs, but with sliding elements and "zap" flaps; maybe they could go to even 5 elements ... and then downwind, all the sailmakers will begin crying into their cafe lattes, because that will be the end of soft sails ... because the multi-slotted wings will develop tremendous lift ... and upwind, the slots will slide together or away and the rig will become aerodynamically clean. I bet the design engineers (and crazies) will be already thinking along these lines.

[petereng]

Hi Gary- I've been working on twist control and multielement control. Being a design engineer (and perhaps crazy) been thinking about this for some time. Lots of thought balloons and semi conscious ZZZZZ's. Quite a problem. I think twist is out for the big rigs. The loads required to twist rigs much bigger than a C=Class get quite big. So if twist is the goal we need very clever "soft" structures or multi multi element type rigid wings. I'm not sure if the C=Class rig with the small panel 2 is really a 3 panel design. Some serious definition work has to be done by the aerodynamists for wing sails! Would be good to be in Auckland to see the AC45s! Cheers Peter S

[petereng]

twist control model - cheers Peter S

[brian eiland]

Originally Posted by Doug Lord

How about headsails on fast tris:
--Smyth finished mid fleet-not too shabby first time out
--How about Tornados, USA 17, Extreme 40 catamarans


Pix: hydroptere, BMW/USA 17, Extreme 40 cats with, yes, headsails:

How about the J-90 Eric Hall was experimenting with a uni-rig, ....
...Eric is now on his third-generation, free standing ,carbon wing rotating mast, with a una-rig mainsail. His “ thought process (and maybe not entirely logical) was: If biplanes became monoplanes and monoplane wings shed wires, why not an unstayed una-rig upwind” Boy, you would surely think this was the ideal upwind rig. In responding to an inquiry on upwind performance, Eric responds, “ first, of course, the boat would be improved upwind with a No.1 jib. Generally, we could not point as high as the others here (Block Island)....

Analysing Upwind Performance

[petereng]

Re: AC72 Artemis wing rig. I watched a video interview with Paul Cayard from Artemis and they plan to use hydraulics to control their AC72 wing. They will have two sailors pedaling or hand cranking hydraulic motors full time. The rules state that there can be no stored energy so the "grinders" will be running all the hydrualic systems. This makes sense as the loads are huge and rope tackle won't be up to it. Its a bit of a shame having to go this way with human engines but we are close to this anyway with big sailing rigs. Peter

[Silver Raven]

Originally Posted by petereng

Hi Gary- I've been working on twist control and multielement control. Being a design engineer (and perhaps crazy) been thinking about this for some time. Lots of thought balloons and semi conscious ZZZZZ's. Quite a problem. I think twist is out for the big rigs. The loads required to twist rigs much bigger than a C=Class get quite big. So if twist is the goal we need very clever "soft" structures or multi multi element type rigid wings. I'm not sure if the C=Class rig with the small panel 2 is really a 3 panel design. Some serious definition work has to be done by the aerodynamists for wing sails! Would be good to be in Auckland to see the AC45s! Cheers Peter S

G'day 'petereng'. Re; "So if twist is the goal we need very clever"soft" structures or multi multi element type rigid wings."
So are we - going 'back' to the future? Semi soft structures might be a good place to start. Variable - wind strenght controlled - wing mast - was/were around back in the mid 60's. Successfully won many very competitive races over many years. Maybe one day someone really smart & high tech will do it for bigger & faster yachts. That'll sure leave me out though. Ciao, james