How much performance could be gained with the Tornado if it were to change from a centerboard boat to a daggerboard boat? I have no aspirations of owning one just curious.

There is only way to find out!

As I understand, there are trunks out there made to fit into the centerboard well for just this purpose......

From sailing a Tornado the last seven years, I would say not much. I think it would be easier to make the boat go really well upwind with daggerboards replacing the centerboards, especially in sub-trapeze conditions. The difference in L/D would of course make it a bit faster upwind, but not that much. So for a changeover I think we would see a better VMG to windward. How large?? Who knows.. There have been tests done, but it has not caught on.
Downwind I dont think we would see much difference in speed/VMG.
I think sail development have been far more important for the performance of the Tornado today. Just look at the mixed events like Texel and the results the boat scores without olympic crews.

Instead of souping up the Tornado platform further, which is so very dear, I would like to see a new 20 foot platform emerge based on the same parameters as the Tornado/B class. Put a Tornado rig on it, and you might have a really fast platform. Looking at all the "Tornado killer" all-carbon projects out there, I think where they miss out is with the rig. The fast and easy way to get a fast rig is to simply prop a Tornado rig with Tornado sails on top of a new platform.
Sorry if I hijack the thread <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

All,

I plugged the numbers into the SCHRS calc here

And rating the Tornado as a new boat (as it would be with a changed hull) so using just LOA, the rating with the current plates would be 0.927 (but as the tornado was measured before the rules changed it is rated with LWL and LOA and so comes out at 0.935 for the current boat).

So old plates, new measurement = 0.927

New hi-aspect plates = 0.913 so SCHRS suggests that daggers would gain you a little over 1%.

One reason NOT to put daggers in a standard Tornado hull would be that it would be measuered as a new hull (as it has been changed), better to build a new hull shape based on more modern thinking.


However, I totally agree with Rolf, that if I was building a new 20 foot boat, I would put a Tornado rig on it.

Exactly right !

That is one thing they did right with the Volvo Extreme 20 boats. Although they had to increase the mainsail area again, meaning they can't make use of future Tornado rig developments.

Personally, I would love to see a Blade 20 footer platform with a modern Tornado rig on it. Let the Olympic boys develop the rig to perfection and have the proven hull shape of the Blades. Then use the rudder profile of catamaranparts.nl and the carbon stocks of AHPC, possibly with small Stealth marine T-foils on the tips. Then steal the daggerboard design of the Capricorn and use the Topcat snuffer hoop and bag. Or make the back out of smoke grey pentex to make it look nice.

That boat is going to be a dream to sail. With the Blade hulls and T-foils it will be an excellent distance racer and won't pitch at all. It also won't slap the waves with the rearbeam. Cost ? Make the hulls out of vinylester and kevlar reinforced glass and it's be under 20K Euro's ready to sail.

Wouter

Straight line you should get slightly more hight from high aspect dagger boards, however I don't think you will find much difference around the cans.... Infact it may be slower.

The beauty of the T is that you leave the boards down all around the course. Think of the amount of time wasted when you have to raise and lower the boards. I believe it is quicker to forget and concentrate on making the boat go fast and positioning yourself well.

Futher more the T is very clean around the c/board cases when the boards are in the up position. Downwind the boards stay down and don't get in your way. Also ask Mitchy how he feels about centerboards when you stick a bow in and slide forward into the sharp edge of the board.

Also the shape of the T boards do not tend to collect weed which is a major plus..... Personaly I would like to try a simular board set up on a Capricorn or Infusion and see the difference around the cans. May be very supprising.

To some extend we already know the difference of this due to the experience with the various F16 who basically all went from low aspect boards to higher aspect boards (but not very high aspect).

In the light and strong winds there is no noticeable difference that can be solely attributed to the daggerboards. I personally would also add unstable conditions to this, significant waves and gusts. In the medium wind conditions the higher aspect boards seem to do slightly better (roughly 7 to 13 knots). The largest benefit of higher aspect boards is that you can raise them a little without totally losing pointing or drive. With the low aspect F16 boards this is an issue and thus the reason why these low aspect boards are always kept fully down just as with the Tornado. On the F16's it is especially important to be able to raise your boards as when you are sailing 1-up you really do want to have less board area in the water then the 2-up version.

With respect to hurting yourself on the trailing egde. The older F16 boards all had a rectangular crosssection in the top halve of the board. Here the trailing edge is 20 mm thick and that hurt a whole lot less then a sharp trailing edge. Sadly, this is more work to make and therefor alot of boards makers just forget about this issue. The newer F16 daggerboards try to compromise on this by cutting away the trailing edge on the top 1/3 of the board. This thickens the trailing where you can hit it. The jury is still out on that however.

In the sailing and tuning seminar that Greg Goodall held at the F16 Global Challenge last august he discussed the issue of raising boards at some length. He said that experience to this point had shown them that leaving the boards all the way down even on spinnaker legs was the fastest. He doesn't pull the boards up unless he has to do so on the upwind leg and basically keeps them were they are for the whole race.

Basically high aspects boards are a performance refinement rather then a performance improvement. As such their effect is relatively small. I personally belong to the camp that believes that an aspect ratio anywhere between 3 and 4 is enough. Old Taipan boards had ratio of 1.85 which is indeed low, and modern F18's have ratio's of 4.5 to 5.5. The efficiency is also a strongly non-linear behaviour, meaning that going from ratio 2 to ratio 4 will create some benefit X but going higher again to say ratio 6 will not nearly have as much benefit. I think the rule of thumb I derive for the boards some years ago was that with each increase in aspect ratio by 1 point you would win 2/3 of the efficiency of the former step (but I'll have to check that). Example :

difference efficiency going from aspect ratio 1 to 2 = say 1 ; total = 1
difference efficiency going from aspect ratio 2 to 3 = 0.67 ; total = 1.67
difference efficiency going from aspect ratio 3 to 4 = 0.44 ; total = 2.11
difference efficiency going from aspect ratio 4 to 5 = 0.29 ; total = 2.40
difference efficiency going from aspect ratio 5 to 6 = 0.18 ; total = 2.69

As can clearly be seen after aspect ratio 4 the difference in almost negligiable. Of course the drawback of high aspect boards is that they become increasinly sensitive and it will be hard to make them stiff enough. All these factors need to be balanced to one another. And here we find the reason to favour aspect ratio between 3 and 4.

I hope this is clear enough for most readers here.

Wouter

T_A,

I think you would loose out with low aspect "plates" like the Tornado has in your Capricorn. In high winds I think you would be competitive, but not in the lighter winds. You know yourself how you have to coax the T in light winds to make it go well to windward. The Tornado was originally designed for the coast of england, which have quite nice winds and not that much light winds. The F-18s become fully powered up a bit faster than the Tornado I think.

Are you raising your boards on the Cap. when going downwind? Why?

Come to think of it, the Cap floats a lot higher in the water whan the T. May be able to get away with it a bit more on a Tiger. Still, think you may be a bit better off with lower aspect blades on the Cap.

Lifting the boards on the downwind particularly in the fresh stuff helps stop the boat from tripping over then.... They run a lot deeper than the T. Yes, tou do notice a big difference with this on the Cap. Futhermore, leaving the boards down on a fresh downwind is loading up the board a lot and inviting trouble. Also the Cap boards are Gybing, with the leading edge gybing to windward under load. This is great for hight on the upwind, however not to good when you are looking for depth on the down. Lifting the board stops the board fro gybing.

I am sure most people now know how a gybing board works.... Don't have a lot of time to go into it, howvere the Cap boards pivot in the case at about 60% aft of the leading edge. Windward board gybes 3 degrees whilct leeward gybes 1.5..... Different angles helps stop cavitation.

How can one board gybe less then the other depending on whether it is on windward or leeward side ?

How does the board know on which side it is ?

I think the Capricorn boards are very high aspect. I seem to recall they are 220 mm by 1100 mm which gives it an aspect ratio of 5. Tiger boards are just below 4 if I remember correctly.

Wouter

The Tornado rig is optimized for the Tornado hulls and platform and for an upwind/downwind race, not for distance racing. If you put that rig on a lighter platform with "modern" hulls, better centerboards and rudders you have a more easily driven boats and then you don't have the optimum rig anymore!

/håkan

That is right Håkan, but how large is the difference? I think the rig/sails will still be a far better powerplant than another design. The amount of development going into the Tornado rig/sails is immense and the rig/sails are far better than a "special" design. I did not say anything about lighter hulls, hard to amateur build cheaply in wood below 165Kgs, so righting moment will be approximately the same and hence also gust response. Then what's left is the difference in prismatic coefficient for the hulls and L/D+effectiveness of the foils. Also consider that the rig is very well known, so you know what is going to happen when you start tuning it.
I think the rig will be superior on a new platform, and hopefully we will find out soon.

What should the sailplan be optimized for, Upwind/downwind or distance racing?

For distance racing, example Round Texel, the sloop rig would probably be the long term winner but for a pure upwind downwind racer the Uni rig is a better choice.

/hakan

Håkan,

if the sailarea is limited by class rules, an uni rig might be the better choise, but otherwise I think the rigs are more equal? Mathematically and theoretically the uni rig is better to windward when sailarea is unlimited, but I am not certain if it works out like that in the real world? Low aspect rigs are good in high wind condtions when high aspect rigs become overpowered (Hobies did well during SM, but the Tornados struggled). The M20 is the only 20 foot uni rig with some success so far and they seem to be doing well at distance races as well, or? At the same time, it's been quiet around the F-18HT.
Anyway, I think the Tornado rig shold do well on both a distance racer and up/downwind. These days the rig is optimized for up/downwind, but it's fairly good on a shy reach as well. For a proper reach an overlapping jib would be better, but the selftacker is so nice to sail with that you would not like to drop it. No selftacker would also make the boat slower downwind.
In the end the sloop rig should be more versatile while the uni rig should be the best upwind. Selling point is: you can pick up a very advanced, well known and fast rig at a good price with affordable used sails. Will a modern platform designed for the Tornado rig be faster than a Tornado both around the course and distance racing? After all, the Tornado is still the benchmark. Who knows? But finding out will no doubt be great fun. I know what I believe <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

The answer to the Uni vs Sloop debate was found a long time ago.

It goes something like this.



Give me your uni-rig design and I'll put a 25 % jib in front of it and beat you.

You will come back of course claiming that this isn't fair, because I have more sailarea.

"Naturally" ; you say :"if I can put that jib area in my mainsail it will be more efficient"

So I give in and allow you to put the jib area into your mainsail.

Then I ask to have your uni-rig again so I can put another 25 % jib in front of it and beat you again.

By now you are getting angry at me or you start to realize that the benefit of the sloop rig is not found in whether it is the most efficient rig of them all but in the fact that it can hold enough sailarea to compensate for the reduction in mainsail efficiency and still get some additional drive.

Of course at some point the mainsail is maxed out in area, adding more area will not add more drive. At that moment a sloop rig can still add 25 % more sail area by having a jib and get roughly 20% more drive while the uni-rig is stuck at being maxed out.

And this is the reason why unlimited racing classes like the 18 foot skiffs have never gone down the uni-rig route.

Now set the class rules to a total area that is 125 % of the amount that you can realistically have in your mainsail and the uni-rigs can shake it.

Anybody who doesn't believe these comments is welcome to come to any Tornado or F18 event and race the sloops rigs as a uni-rig by leaving the jib in the bag. You will learn soon enough that the additional pointing ability is not enough to compensate for the lost drive c.q. speed upwind. I think this was the experience Tornado_Alive shared with the world a few years back. The difference may be small but will definately be there. And of course as soon as you are on a shy or broad reach (non-spin) it will be bye-bye baby.

So basically a sloop is not losing on the upwind in VMG while does retain "another tool in the shed" when the racing goes below "pointing as high as you can" due to a windshift, overstanding the mark or doing a distance race.

End of story.

Wouter

Your are making thinks too simple Wouter! In some cases less is more.

You can either go the "lets add loads of sails, lines and other fancy stuff" or "lets remove all things not needed to save weight and windage". Two examples of the two different roads are Eagle Cat and M20 (Marstrom original version at 115 kg, not the modified versions).

The M20 beats the Eagle Cat on the upwind.

Is it ok for you if I show up with an F18ht at an F18 event, or is that unfair? The F18ht is designed with all the benefits you get from loosing the jib, less gear, less weight....

/hakan

yes wouter, you will win because you have more sail area...........

If you set the class rules at 100% of what a Uni rig can carry, what would you have

100% mainsail
or

75% main and 25% Jib ?

Wouter

I believe that Goran Marstrom initally designed the M20 as the olympic replacement. (Word of mouth from Robbie D) He argued that ultimate speed was not the point of the OLYMPIC one design ... what he as a designer was trying to do is come up with a boat that REALLY stretched the crew work in sailing the boat at max performance . So... Light weight.. ... eg ultra responsive to team position and dynamics... and Fast to tack and jibe to maximize the tactical aspects ... all be it at high speed.

He argued that upwind... the skill in getting the uni to go upwind with helm on the down haul... cunningham and the crew working the sheet and rotation would be the ultimate in skill requirement.

I am sure I have forgotten all of the subtle details of his argument though.

So... IF you were to change the olympic boat to something new.... and the the question is not ultimate performance.. or what is the most efficient rig solution.. What are the options.

Is their some performance aspect that is emphasized or ehnanced by the main and spin configuration in a WL course.



Thoughts???

Sorry Hakan, <img src="http://www.catsailor.com/forums/images/graemlins/tongue.gif" alt="" />

That dog won't hunt.

A complete selftacking jib setup weights less then 2 kg's and can be made to work well with only one line; the sheet. Pins in the traveller track will be enough to set the jib car and it is not really needed to adjust the jib luff tension on the water.

By adding a bridle foil you can even have a jib on a platform that was not designed to handle the bridle loads. How much weight will that add ? Another 2 kg when using a 50x1.6 mm round alu tube with 4 mm stainless steel wires. Cold be light when made from carbon.

Hell, lets add another kg and say that the total jib package will add 5 kg to the boat.

You call that "all the benefits ... from losing the jib", I call it negligiable.



An F18 is a sloop rig at 180 kg, the 18HT is a uni-rig at 130 kg. The F18 only has 6% more sail area then the 18HT and needs that to overcome its additional 50 kgs (18% of the total boat+crew weight). Not really a fair comparison right ?

How about having the F18 at 135 kg and the 18HT at 130 kg while giving the F18 the same rig as the F18HT but with an added 25 % jib. What do you think will then happen then ?


Wouter