New low-cost "hardware store" racing class; input on proposed rules

CT, that is a load of slithering and sliding.
From now on I won't read/reply to any more of your nonsense.
cheers.

 

Yippeeee!!!

And all because I dared to use a term in a way you don't like it to be used.....

 

Get together and make out on another forum ladies
This thing was interesting until you started a dickswing
Now allow it to get back to the valuable discussion it was

 

No, that's not the reason.

 

Gary,

You can't believe how pleasant it is now that I put an "ignore" on Doug Lord.
You might try it for a while with someone that bothers you.

Unless you don't see this because you assigned it to me.

 

Personally I think CT249 knows more about many different types of boats than most on this forum

I sailed a Multi23 trimaran a couple of weeks ago, we sailed it goosewinged downwind as it was faster

Years ago the Quornings took a Dragonfly 8m to a European micromultihull championships with a symmetric spinnaker set on a long pole, they sailed dead downwind in the light air regatta and won, beating Firebirds, Shuttleworth, F boats, even me!

Low aspect sails are efficient at high angles. The Laser is surprisingly well optimised. A great hull for displacement sailing and a good rig for downwind sailing (the unstayed mast helps of course). The IC10 is "slow" in light winds (it's poor low speed hull shape doesn't help), as are many skiff classes

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

That's nice. It's also the least important part.

 

I've recently been wondering how often people who think they are running absolutely dead downwind actually are. Its odd how the windex on my Canoe appears to point dead fore and aft a long way before the boat is actually at 180 degrees to the true wind. My experience is that, no matter how deep I think I am sailing, even with poled out goosewinged jib, there is always a right gybe to be on and a wrong one, which must mean I'm a few degrees off dead square. And I've never seen a polar diagram in which 180 degrees was not deadly slow, even if the best vmg was at 175 degrees or something. Certainly where I am square running doesn't seem to mean exactly 180 degrees, usage seems to be "deeper than a broad reach".

The other advantage the Laser has in gusty inland conditions, IME, is that it has exactly the right performance to say in the gust front all the way down. A Canoe, for example, will tend to sail out of the gust front into the lighter wind beyond, at which point it will slow down. So the Laser will be in the main body of the gust, vmg at gust speed, and the canoe will be in the unsteady air just preceding the gust front, in less wind, and still vmg at gust speed.

 

I think the word "appears" is probably the right one. You are bound to have parallax errors

Simple geometry shows you can be 10deg off course without affecting distance sailed. Even 15deg makes little difference

Of course in an unstayed boat like a Laser you are running by the lee for speed, so are also not dead downwind

going with the waves is always faster so that might determine your best gybe

RW

 

Excellent question CT.

Aspect Ratio; is defined as the square of the span divided by the area of the surface. Is this Whimpress area, i.e. the sail projected down to the water surface, or plane area, as measured by the sailmaker. A comparison of Wimpress area AR’s, especially on dinghies, makes interesting reading. AR is affected by, and effects, the distribution of chord over the span but is only one of a large number of important numbers when designing a lifting surface. One measure being which part of the lifting surface is doing the most work/unit area too. This is not constant, or even particually consistent.

Aspect ratio is an odd measurement. It really helps when AREA is restricted for some reason. Examples being the older Square Meter class, and in aviation, sailplanes, also in Square Meter classes. The real advantage lies in long leading edge's, not just span. In aviation, span is often limited by something unrelated to performance, gate width being typical for commercial aircraft, but eventually structural weight is a severe limit. Quite astounding aspect ratios were attained by WW1 single engine bombers, the Fairey III being an excellent example. Incidentally this aircraft also sported an amazing variable camber scheme, one well worth studying.

Some advantage accrues from simply getting the sail up higher above the water surface, as much out of the earths boundary layer as possible. This is most noticeable when different classes, especially keelboats, are racing together, taller is almost always better.

Just as an airplane wing approaches a serious structural limit with span, a sailboat mast also reaches a limit, needing more beam to support, more spreaders, or both, eventually reaching a point of limited returns. Interference drag becomes dominant, and larger diameter free standing masts become slightly suspect too.

Sailing with wind abaft the beam, the sail is classically a simple drag device, area only is effective, regardless of shape, or aspect ratio. In fact, the nearer to square the better in this case. Modern boats, and ice boats, attempt to defeat this principle by 'tacking' downwind. This increase to apparent wind velocity across the sail artificially increasing sail performance by having the air move dynamically across the sail surface. A case can be made that high aspect ratio sails will find effectiveness at lower apparent velocity, they need less velocity differential to create lift. High aspect ratio surfaces are also far more subject to apparent wind angle, AOA for an aircraft Ie they stall,and loose lift through inducing a turbulent flow across their leeward surface. As soon as this happens the sail becomes a drag plane, with no dynamic assistance.

All; the updraft from a sail running downwind, its tip effect if you like, will impart a swirling flow around a wind direction monitor mounted in front of the mast. This means this monitor could be as much as 30' off in any direction, and you couldn't know. A monitor would have to be mounted quite far aft of the mast, above the tip, to avoid this phenomena. Note, wind monitors are mounted in front of the masthead on the assumption they will give a better apparent wind direction for beating.

Unlike classes with restricted sail area, this hardware class can simply add area in compensation. Like a combustion engine, there is no substitute for cubic inches, or in this case, square feet.

Yes, CT, from your comment back in 2005, aircraft wings, including the aluminum 747 wing DO use ‘ wist on bend’ to relieve stress. When you see a Boeing wing bend up in flight, it is relieving load, limiting bumps, just like a leaf spring, it's a good thing. The 787 wing uses orientated carbon fiber to REALY take this principle to a next level. I assume a sail and mast can be set up to do a similar function, twisting to relieve load dynamically.

I am planning to add fibers to my mast, possibly to control twist, probably because i can.

Note: the most efficient wing tip known today is the 787's raked wingtip, possibly closely followed by the Dornier NGT (Neuen Trag Flugal). The original 747 wingtip was instigated because it was deemed too expensive to move the wing assembly tool away from the factory wall for the limited number of 747-400's projected. Now, 1300 747’s later, it's wingtip is a classic marketing success. Turned up wingtips, aside from being a marketing trick to fool people into thinking airlines are making an effort to reduce fuel consumption, do increase the apparent span by about half their height. A slight advantage when airport gate width is restricted.

 

Though thick, low chord, wings revolutionized the Biplanes of WW1, Platz designed them for Antony Fokker, and they were operating in the, 100Kt range, i.e. in typical sailboat wind velocities, they were still 10-20% thickness, i.e. still quite thin by todays standards. Much of their benefit came from reduced external bracing, and not just increased aerodynamic efficiency. In fact, just cleaning up the engine installation could have been the largest contributor.

If this is the case, we should be looking at enclosed aerodynamic cockpits, aero suits for the crew, and greatly reduced rigging. Remember when crews had to hide behind coamings on keelboats, especially Skerry's and Meterboats.

A round, semicircular, front to any aerodynamic surface is not a good idea. All aerodynamic surfaces are a series of curves, no arcs inviolved at all. Circular poles are used for their convenience, not efficiency.

No matter how you configure it, sail area is a necessity. If you want just 2' chord, then the sail height must increase in proportion, increasing staying issues, but gaining advantage from having sail area up high. This in turn increases the destabising force of heeling, the CP moves up as the mast height moves up.

The CP of each sail contributes to the total CP, and this must be compatable with the keel CP and and hull shape. These positions must be compatable with the hull/rig healed as well, otherwise the boat will not 'balance' and incur trim drag from the surfaces correcting for the inherent lack of trim in the boat.

Its interesting that over all the millenia of sailing, many rigs and sail shapes have been tested, but we still see a predominance of sloop riggs, especially in dinghies. How much do we blame the racing rules for this? In fact an excelent case could be made for the Gunter rig, and posibly the high peaked Lug as well, and both do exist in developed form. This hardware class is an excelent place to experiment, no huge investment in spars or sails, so tests can be made.

In spite of this, and even with the help of our aerodynamicist(s), we are building 3 different single stick rigs, with different main/jib proportions, and even different AR's. Our new masts are being treated as part of the sail, inducing positive lift effects, rather like a Kruger Flap on a wing.

 

You can also control twist by using different species of wood in different parts of the mast, as they did in the 1960's. Very expensive to build like that though

And you are right, high AR foils are much trickier to use, whether above or below the WL

So, Alan, why is it quicker to sail a Laser by the lee?

RW

 

And have been for the last thirty years or so.

Not at all if we have any sense, because the key development classes don't especially mandate bermudan sloop rigs.

 

I think most people missed the the point of my proposed 2' chord rigid wing sail. It would be a sail plan with a normal height, a very structural but small area wing sail for the main and most of the sail area in the foresail.

 

Thank you for the clarification

Something like what Chris White has done on his catamarans?

I doubt it would work on most dinghies. Check out the Bembridge Redwing class, completely open rule for sail area. One even was fitted with a autogyro propellor and was class legal

RW