Rudder stock porn

[Presuming Ed 193]

Saw this on the Carbonicboats blog. Shexy.

 

Wonder what they're using for bearing surfaces. Wasn't there a time in cycling when people drilled holes in everything, then worked out that the aero drag penalty more than offset the weight loss benefits? Wonder if they'll stick a clear film on. Or perhaps the flow is such a mess back there is doesn't matter. Who's to know?

 

 

Nice solid pintle/gudgeon set up.

 

[Doug Lord 1,219]

Thats a brilliant solution to get a balanced rudder out of a cassete installation-just fantastic.

[SimonN 380]

Try again, Doug. That's not the main reason why Dario has done this

[macca 14]

Try again, Doug. That's not the main reason why Dario has done this

 

Its the main reason why we did it... We get a balanced foil that we can adjust the height by lifting and lowering in the rudder case.

 

We can also adjust the elevator foil angle by tilting the transom, Paradox achieves this in a different way, but its essentially the same.

[SimonN 380]

So, Macca, as you say, the main reason is so you can adjust the height without altering the balanced rudder effect and it compensates for the effect you get as you heel.. You can achieve the balanced rudder in other ways, as most cats do, but the problem with that is that as you adjust the height and/or heel, the balance changes. For most applications, where you don't need to alter the height of the foil in the case, there are simpler ways of getting the balanced rudder effect.

 

Having said that, i personally believe that Dario makes too much of an issue about the change in balance as you fly a hull on the A. I sail with the most aggressive tuck under of almost anybody i know and don't have a problem. Everybody who has sailed my boat loves it once they get used to it. Maybe it's just personal taste, becaus eI don't think you can get over sensitive, although itr can take getting used to.

 

This system has advantages (as above) but also disadvantages. For instance, changing the amount of "balance" is a lot more difficult with Paradox set up (not sure if that is so for your boat, Macca). On the A, we simply rake the foil more or less under the boat. With the rake now being used and some playing around with significantly different rake settings for different conditions, the amount of balanced effect is an important tuning aid.

 

Having said all of that, it is a very neatly designed set up, although i prefer Macca's beautiful carbon stocks!

[Doug Lord 1,219]

Try again, Doug. That's not the main reason why Dario has done this

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There you go again, Simon...... Thanks Macca for helping out here. Here is a quote from Dario:

 

This assembly determines the position of the pivot axis relative to the rudder blade and the angle of the blade relative to the tiller.

The position of the pivot axis is critical to the balance of the rudder: The further back along the blade (more foil area ahead of the pivot axis) the more ‘compensation’. Meaning more area helping to turn the rudder relative to the area behind the axis pushing to straighten the rudder.

[Dyneema_forever 0]

Wrong again SimonN!

[SimonN 380]

Having spent time chatting with Dario about it, I know exactly what is going on. Everybody has been sailing with balanced rudders on A's for a long time. It's a key tuning aid. And you can do it on a dagger style rudder without the system being used on the Paradox. In fact, if it was just to get a balanced rudder, it is a way over the top solution. It is the perceived benefits above and beyond the basic balanced rudder that makes this system interesting, not the fact it is a balanced rudder.

[nacrajon 2]

Not wanting to get involved in this dispute but if the primary aim was to achieve a balanced rudder, why wasn't the pintle position set at 1/4 chord as per the fullcarbon cassettes shown in the later photo?

[macca 14]

It depends on the foil section shape and the tiller arm length to get the right balance and feel.

 

We have quite short arms on the GC32 so we go for more "blade" balance.

[AClass USA 230 48]

One thing is for sure, the Carbonic Boats workmanship is incredible and I was told by a competitor at the recent event where it debuted that if the boat's performance matches that workmanship, it will be a winner. Certainly looks like you could retrofit their rudder system to a boat like the DNA, Scheurer, or Nikita as long as the transom heights and pintle spacings are compatible. The rudder seems projected relatively far away from the transom. Good or bad?

[Doug Lord 1,219]

One thing is for sure, the Carbonic Boats workmanship is incredible and I was told by a competitor at the recent event where it debuted that if the boat's performance matches that workmanship, it will be a winner. Certainly looks like you could retrofit their rudder system to a boat like the DNA, Scheurer, or Nikita as long as the transom heights and pintle spacings are compatible. The rudder seems projected relatively far away from the transom. Good or bad?

-------------------------

With a T-foil-good. But is it legal to move the rudder back any amount or is there a limit in the A class?

[dacarls 11]

No limit.

[Doug Lord 1,219]

No limit.

==============

Thanks ,Dave-that opens up some interesting possibilities.....

[Waynemarlow 138]

The rudder seems projected relatively far away from the transom. Good or bad?

 

Certainly in the experiment I tried with a T foil and the whole cassette set back about 200mm on my F16, I came across some real negatives in moving it back beyond the normal pintle length. Principally the bottom of the cassette seemed to be in much less turbulent water and therefore the broadness of the cassette became quite a drag ( aerated turbulent water is much less dense ), enough that I smashed off the normal pintle bolts I had been using without problem for some years. Put in heavier bolts and ended up pulling those and the mounts out through the transom such were the loads of the T foil. I was quite surprised. Moved the same cassette back to very close to the transom using smaller bolts without problem and I have noticed how smooth the flow away from the rear of the rudder where as with it back further you could almost see a " rooster tail "

 

Most gliders for efficiency have a T tail with a lead weighted leading edge of the rudder to try and stop flutter and to allow the pivot point to be moved foward so that the rudder becomes much more streamlined to the air flow without risking the rudder stailing or over compensating at higher speeds, as per a compensated rudder system. I am surprised we haven't gone down the route of the glider T tail where the T and leading edge doesn't rotate and is fixed doing away with all these fancy and bizarre looking pintle systems we are seeing. Only about 2/3 rd or the rudder pivots, in denser medium such as water it should have minium drag and yet generating similar forces. The Moth boys seem to have worked out how to use a composte hinge system with a mylar strip on the opposite side to stop water transfer. Mmmm this maybe a much better and cheaper system to make as well.