Very good, Jake! Do you think it would be possible to have a cassette that would be versatile enough to use with a variety of different rudders? Rudders are pretty expensive items to replace just to get a different mechanism for raising/lowering. And most people want to have class-legal rudders if they do any one-design racing. If everyone could still use their stock rudders but just change to the cassette system -- and if the new mechanism could be made class legal, it would be much more marketable, maybe.

Just giving you a new challenge to chew on.

that was part of the reason I thought adding a slot in the center might help. It's not the ultimate solution but we could make a double sided plastic roller that would stick out of the sides of the rudder (kinda like frankenstein's bolts in his neck) and fit in that slot. One simple hole drilled in the rudder will do. They would take the majority of the frictional load and make rudder shape less of a problem. However, I'm not sure the slot could be made as long enough (it would need to be as long as the vertical travel of the rudder). In any case, something somewhere would still have to be shimmed to fit - I'll continue this thought next time I'm in my design office (the bathroom).

I literally have a folder with various toilet paper and restaraunt napkin scriblings in it! (was that too much information? )

still needs T-foils :P

Dear Lord in heaven, Jacob. I think I speak for everyone when I say yes, that was too much information; particularly after you mentioned a "quick and dirty 3 minute sketch" earlier. Mary, I swear I've never seen this folder and I'm afraid to ask where he keeps it.

Mary

Dagger rudders were mentioned here and I believe their features should be present in the ideal beach cat rudder. 49ers, 29ers and some Malcolm Tenant designs feature this kind of rudder. They are interesting for two reasons:

-The blade can be raised vertically in low wind or for beaching, reducing drag and draft but still allowing effective steering.

- The blade is totally removable, simplifiying replacements and maintenance.

The obvious and serious problem is that the blade does not pivot when hitting the bottom or floating debris.

My proposal is a pivoting dagger rudder - something that would do both tricks: pivot back and retract vertically.

Ian Farrier recently designed one for his F-33, and (correctly) called it kick-back dagger rudder. Unfortunately, his solution is not satisfactory for a beach cat, mainly because it relies on one attachment point only when kicked back - the upper gudgeon.

(It features an additional horizontal hinge in the upper gudgeon of the dagger rudder trunk, and a release mechanism in the lower gudgeon. When the blade hits an obstacle, the entire trunk and blade assembly pivots back, supported only by the upper gudgeon, which will has to support the extreme loads)

This design is very probably unsteerable after the lower gudgeon is released so it is not really safe for a beach cat, like most cats compared to the Supercat/ARC.

I was also dreaming of a pivoting dagger rudder for my boat because it has additional advantages in the particular case of the Catri (motoring in shallow waters with the engine on the rudder).

Then I remebered a very interesting daggerboard design from an old (10 or 15 years ago) windsurfer. As far as I know, it has not been used in rudders, but who knows... Anyway, I adapted that design to a rudder.

It is a simple concept and the rudderhead can be made as strong as necessary to please Bill Roberts, without oversized gudgeons, as in the F33.

The basic drawing is attached. The real plan is almost ready and I intend to use it when sailing in shallow waters.

I hope you like it.

Cheers,
Luiz

Looks great, Luiz! Let us know how it works when you get it in the water. It's not really clear to me how it is held in place when fully down so that it won't tend to kick back just from water pressure on a cat sailing at high speed, but I'm sure you have that covered.

Now you have given Jake something else to think about when he is in his design room.

Your rudder drawing shows potential, Jake! How would it suffice against those monster jellyfish at 20+ kts? Or maybe even a loggerhead turtle? In those situations, the rudder would be in the full down position. Would that place undue stress on the upper gudgeon?

I presume you'd control the depth of the blade with lines akin to the Nacra or SuperCat system? Who's job would that be while surfing down a 6'+ wave with the spin up?

Mary,

The line cleated in the kick-up camcleat keeps the blade upright - it is exactly the same line that brings and locks the rudder to the vertical position in the Laser.

When the blade hits an obstacle, the cleat frees this line and the blade rotates back.

The other line serves to rotate the blade in the other direction (to the back).

This control system with two lines is just ilustrative. For a beach cat, I think a rigid control bar (like the Tornado/Taipan system) would work better.

Also, control lines could be improved using the system designed by Bill Roberts, with spring locks released by the same lines - but the drawing would not be clear to demonstrate the concept.

The tricky part was finding an elegant solution to raise and lower the blade vertically. A tall rudderhead with vertical lines is obvious but ugly. And three or four control lines in a rudder are not desirable. Lets see who finds my solution.

now that's a beautiful thing Luiz! Wow. I'll process that more thoroughly soon.

I like Luiz's design, very much outside the box. The rudder would be very much vulnerable while halfway down. The delicate (thin) trailing edge would not have much support. I would think it easy to damage while inserting/removing it, or if you hit something with it halfway.

How would the blade stay in the half up/down positon?

My only other thoughts would be sand jamming the blade into place. Could you trust it in a Worrell style situation to "kick" up as you hit the beach?

Nobody else has addressed the thing I said earlier about the rudder getting jammed into the sand backwards, but if the blade was only half down, the likelyhood would be reduced.

I also wouldn't want to have to be in the back of the boat for a rough lemans style launch....gotta keep the weight forward.

sorry....rambling....

p.s. the mod Hobie thing...it tough to explain, you would have to see it.

I know of Luiz' idea, as I have a Mega Cat racing windsurfer (one design class) with this very daggarboard design. High aspect, variable angle with recessed well, controlled with your foot.

The only drawback I see is that in the "kickback" position, I would think there would be a lot more force on the gudgeon if you were trying to steer, and could possibly cause failure in that area.

I'm sure there is a way to work out the control lines so that you can secure the rudder in the down or mid-down postion. My only question is when my leeward rudder kicks back when I'm on the wire in a blow with the spin up. The I-20 system works mildly okay, as I just need to drive deep and push the tiller bar (which can occasionally be done from the center/windward side of the tramp. If I had to go to the leeward hull and fiddle with lines while I try to steer and my crew yells at me, I guess I could be in trouble...

And with that "T" rudder, if you are flying a hull, would that direct forces in the wrong direction? I can understand how it works on those Hobie Raves, since I think they don't roll (I think that's the term), but a cat pitches, rolls, and yaws...

Two years ago, I modified the cams on my Hobie 17 system, and it works great. This is not a new idea, but it solves the problem of the cam sticking down in the locked position, then the problem of putting the rudder back down. Simply cut off the top end of the cam, about 3/8 inch. This allows the rudder to be put down, with the cam in either position. It works well in the surf. There is still enough cam slot to hold the rudder down, even in a blow.

Caleb Tarleton

Jake,
If you want more details and a simple setup to move it up and down, please send me an email: sysfx@yahoo.com
Cheers,
Luiz

"Okay, so how does it work? And can that system be adapted to other boats?"

- rudders locked up in "park" ....release the line and they lay on the sand....start sailing out through the surf with them hanging down....tiller and crossbar are in the normal position unlike some other systems.....going through the surf they will not lock down inadvertently so you can't come back down on them.....once through the surf pull the rope and they become locked in. To release pull the same rope then pull the other one to raise them.


I don't see why they couldn't be put on other boats, certainly no problem bolting the whole system up to the back of the boat....may reqiure a little "sailor engineering".....great system IMHO

During normal sailing the forces in the gougeons are relatively low. Higher loads occur with the blade pivoted back. Then, higher loads are generated in this design due to the longer distance between the rotation axis and the gougeons. However, the load is divided between two gudgeons, while the F-33 configuration puts all the load in one gudgeon only - and still works (but not as a beach cat).



Not necessarily lines. A control bar is a good option. The tiller bar can also be used.



Agreed. If you are trapezing to the beach with the rudders down and your rudder kicks backs, I think you are in trouble regardless of rudder type...
For this specific situation the best rudder setup is the Dotan style - up, down, ready. Note that the Hobie and Supercat rudders are also problematic in the same situation. A pivoting dagger rudder would enable you to raise the blades vertically a bit before heading to the beach and steer the boat more effectively then with a pivoted rudder. An accidental kick back is... accidental.



If your concern is keeping a foiled blade down using a pivoting dagger rudder, the answer is that both lines holding the rudder in position need to be fastened to separate kick-up cleats (or the control bar should be held in position fore and aft). This will keep the blade down.

If your concern is about the contribution of T foils when the boat moves changing the angle of attack of the foils (due to heeling, yawing, pitching, rolling, passing waves) then it is very complicated and I don´t know enough to answer.

Back to the pivoting dagger rudder, in another post someone expressed concern that the trailing edge of the blade would be too exposed. The rotating axis is a plastic tube, free to rotate over the inner bolt. The tube has to be softer then the blade, to protect it. It can even be coated with ruber, if desired. Otherwise, the trailing edge is as exposed as in a non-pivoting dagger rudder.

Cheers,
Luiz

Why is it so important to have rudders that kick up, we have used the dagger rudders for 5 years now, first just standard blades, then with t-foils on. They work well and are easy but just different.

When leaving or approaching the beach, the rudders are lowered partially, about 8 ins, this gives as much stearage as a pivoting rudder half way up, but does not have the tiller loads of the pivoter.

Once sailing the rudders draw less than the daggerboards, so unless you are going fast backwards you will strike the daggerboard first.

No-one seams to feel that pivoting centreboards are a must but a pivoting rudder behind a fixed daggerboard will never have to take a hit unless you break the daggerboard.

As previously mentioned the main concern with all these systems is if the surf dumps the boat backwards on the beach, it's never happened to me so I don't know, but I think that if the rudder was only slid 8 ins down the cassette it would have a better chance of survival than a pivoting one.

regards


john

When you're sailing out through the surf you already have the dagger-boards up. You've gotta steer though so the rudders are down. A nice wave hits the nose, shoves it up high and pushes the boat back. Rudders touch bottom and, if turned, crumple sideways. If they were being held straight they likely damage the housing if not the transom.

John,

I don't know what boat you are sailing, but almost certainly what you wrote makes perfect sense for all boats sharing the following features with yours':

A) The rudder blades are exactly aligned with the boards AND
B) The rudder blades are significantly shallower then the boards.

For all boats sharing this design features, the pivot in the rudder is not so important and the dagger rudder is an excelent choice.

However, some beach cats don't have boards and in this situation the pivoting feature is VERY important.

Other cats have board blades nearly as deep as the rudder blades (ARC 21, for example). If the weight is in the back or there are waves, the boards will be shallower and the rudder can hit the bottom first. In this case, the pivot is also necessary.

Cats may also be designed with the boards positioned differently from the centerline (athwartships) then the rudders and/or inclined in relation to them. In any of this cases, the boards may just miss an obstacle that will hit the rudder - and the pivot is necessary again.

Each cat design will require different rudder characteristics, so there is no "best" rudder design. Each rudder design is best for specific global design purposes and each has its own pros and cons. The best design is the one that better matches the boat's design goals.

The Tornado/A Class/Taipan style is very light, so it is very good for racing without runing aground frequently. In light conditions, a dagger rudder (of equal weight) is even better, because you can reduce the wetted surface with less dramatic rudder aspect-ratio reduction.

For frequent beaching, a pivot rudder is necessary. I dislike the Hobie rudder because it is fragile and difficult to adjust, but it is easy to find replacement parts. The Supercat/ARC rudder is more resistant to abuse and more sophisticated - its only con is that it has more components (springs, bolts, lines, etc) to fail or jam - but they do not fail or jam frequently.

The pivoting dagger rudder mixes features (pros and cons) of pivoting rudders and dagger rudders. It is an interesting compromise for a dual purpose boat, suitable for speed and for frequent beaching. It is obviously not the best design for all cats, but it certainly works. And since it has never been used in cats (as far as I know), its features must be carefully examined before deciding for or against it.

Cheers,
Luiz

If I could have anything I wanted for surf, it would be the Marstrom design with the "hell for stout" construction of the NACRA or Supercat.

How about just popping the rudders up and steering via the sails alone? This should work long enough to get you ashore.