Rudder Length

Another Question on the Rules. Sorry if it has been asked before.

I have looked at the Rules and was wondering if there is a restriction on the Length of rudder that can be used. All I can see is a restriction on how far aft (51mm) and thickness (6.3mm).

The Box Rules provides a gauge that is 200mm from top of box but isn’t clear if this is a restricted length. :confused:

Can a rudder extend beyond the 200mm Gauge providing it meets other rule restrictions?

Probably a ridiculous observation, but could the Rudder extend beyond the depth of the Box providing it meets the restrictions?

I would see a rudder extending beyond the box in depth would be outside the spirit of the Rules but it could have some weight advantages. :sly:

I know it would need a Higher Torque Servo to control. Just asking as I think I’ll need a bigger rudder (Longer)

Cheers :zbeer:


Also posted on Fotty USA forum but it didn’t seem to take.

the rules pretty clearly state that the boat in racing trim must fit into the 12x12x6 box, and, to my reading that the rudder while it may over hang can only do so by the amount specified. however, i could see say a 6" deep - 7"deep rudder under the boat as being helpful…:graduate:

Exactly what I thought.

The 51mm overhang deals with the Horizontal Plane yet there doesn’t seem to be any restriction on the Vertical Plane. Other than an inferred suggestion of a 200mm gauge.

Depending on rudder design, the Rudder could be completely external to the Box and therefore not subject to any Vertical Plane restrictions. I could see the Box placed on a flat surface stopping the use of exceptionally long rudders. But I can’t see any rule that stops longer rudders providing the boat sits in the box and the rudder does not extend beyond 51mm on the Horizontal plane.

Am I wrong?

Looking at the rules…
The 200mm slot in one narrow side of the box will restrict the length of the rudder if the rudder sits through the slot.

If the rudder is inside of the box then it could be as deep as the box depth I imagine but… you could fall foul of the ISAF definition of ‘rudder’ if trying to use it as a ballast device.

As to outside the box, I suspect that as the rudder is a hull appendage rather than part of the rig, then it will have to fit either inside the box or through the slot.

Any more authoritative answers?


ISAF Equipment Rules of Sailing 2005-2008

E.1.10 Rudder
A movable hull appendage primarily used to affect steerage

If you were using the rudder as ballast, I think you would quickly reach a point where the “primary” function ceased to be steerage… but more importantly, in order to be able to control the greater mass of the rudder, and the increased resistance from a larger surface area (which would presumably in turn create extra drag), you would need to have a bigger servo in the hull.

I imagined the question to be something like “if the tiller arm extends through the slot, can the rudder descend below 300 mm?”


Thanks for the input. I wasn’t considering an excessive rudder but one that might help in the gusts. I was thinking well inside the box depth but say up to 250mm from the sheerline, which shouldn’t be too extreme.

Not considering it as ballast as the primary function is steerage with any reduction in weight being more of a bonus than a consequence or an alternative.

The obvious concern I had was whether a Rudder post/fixing point was considered part of the Rudder Fitting and therefore not measured in the Hull Length. From past experience you can get away with the fitting providing it isn’t excessive to its intended purpose. :wink:

From my scale boat and Fast Electric days I have a few innovative and strong rudder configurations that would fit nicely within the 51mm. Might Sacrifice a few extra grams for greater steering ability.

Testing different rudder sizes on my Model A600 definitely has shown up some steering advantages with the longer rudder in the gusts and to windward. Running was marginal.


ISAF Equipment Rules of Sailing 2005-2008

[b]E.1.10 Rudder
A movable hull appendage primarily used to affect steerage

If you were using the rudder as ballast, I think you would quickly reach a point where the “primary” function ceased to be steerage… but more importantly, in order to be able to control the greater mass of the rudder, and the increased resistance from a larger surface area (which would presumably in turn create extra drag), you would need to have a bigger servo in the hull.

I imagined the question to be something like “if the tiller arm extends through the slot, can the rudder descend below 300 mm?”

Waboats, be careful when using your rudder fittings to make sure the apparatus fits within the “V” at the top of the rudder slot. If the fittings prevent the stern from being able to go down into the box to the point where the deck is at least level with the top of the box, the boat would not be legal.

This is the one area that I’m not entirely happy with in our current rule, because I think it gets overly tricky sometimes.

Bill H

No problem with the “V” area for the fitting. A design I am working on will easily fit.

The Length of rudder is my only concern.

It does seem a little tricky, hence my question.

I would suggest that if the rudder is inside the box and clearly made of material such that it is not acting as ‘ballast’ then it could extend to the bottom of the box if you wished. Remember it is the CD (Comp. Directors) opinion that counts here if you wish to race.

Where I would see a problem and a need for an interpretation is if the rudder where fully outside of the box and deeper than the rudder slot. The slot is 200mm deep to keep things accurate here. I do believe this is already covered in the rules though as stated above.

Allowed practice so far, and I only did it after consultation with Brett long ago, is to allow rudder mounting structures (like a small standoff) to extend into the slot. Therefore being in addition to the hull length. The ‘V’ is available for use too and has ample room for simple pushrod/tiller systems.


As I understand it the question is whether a rudder that projects through the slot may be deeper then the slot outside the box. That is a very good question. Like you I would hate this class to get tied up in legalisms and it is good that a young rule be tested early on in good spirit.

The question is an interesting one. The definitions in the rule were never claimed to be razor-sharp and interpretation is left to the good (or bad) sense of the technical committee. As a member of that conmiittee I would personally welcome a properly suported request for interpretation (see Official Footy Website). However, rember that the committe requires requests to be clearly specified and will rule on the request: its function is to interpret the rule, not to change it.

Obvioiusly it would be invidious if I were to give my opinion on the likely result now, especially since I am not entirely sure I understand the specification of the problem.


Good news is I’ve sent off a rather detailed Interpretation Request with regards to the Rudder Length issue. sorry your email was private so couldn’t send you a copy.

Hopefully a detailed explanation will be more enlightening. I’m happy to elaborate on anything that isn’t clear by way of a simple drawing.

Not a legal Minded Person but do understand that rules must be addressed to avoid anarchy and an eventual demise. Address these in developing mode and the future is always brighter. That’s what developing is supposed to be. R&D also includes the rules.

In some way I have perhaps found an unintended Loophole and one which was not considered. But then again the US did that with their big Cat against NZ.

Hope you guys can make sense of my ramblings as it clearly needs some rule feedback, regarless of whether it is considered a benefit to a Go Fast Boat or not. If it’s of no benefit to the boat then why would anybody worry about whether it was put on a boat or not?

Don’t have any misgivings about the rules as all I want to make sure of is that I have the right interpretation before I commence doing some more R&D as they say. Can’t say much but know of a large tank with lots of Gizmos attached somewhere close.

I’ll double post under the Legalism Thread in the hope of stopping some of the backdoor angst.

John :zbeer:

6th January 2007

I have been requested to put a question to you that has been openly discussed on the Footy Forum. Angus suggested including Bill & Himself. Angus’ email is private and cannot be located so I can only do what I have available.

My primary question surrounds the Length (Depth) that the Rudder my extend on the Vertical Axes for the Footy.

By reading the Rules there doesn’t seem to be an exact determination of what the Overall Restrictive Length of the Rudder might be. There is however the assumed 200mm slot but no formal rule to provide for this eventuating.

FOOTY CLASS RULES for radio sailing
These are open class rules in which anything not specifically restricted or prohibited is permitted.

B.1 With the exceptions listed below in B.2, B.3 and B.4, the boat in racing trim shall be

capable of fitting into an open-topped rectangular measurement box of internal dimensions

305mm long, 305mm deep, 153mm wide, with 6.3mm wide slots for projecting spars and

rudder, as shown in the diagram.

B.2 The following may project above the top of the measurement box: sail(s), mast, spars,

rigging, aerial, associated fittings.

B.3 A bowsprit may project forward of the measurement box.

B.4 The following may project aft of the measurement box: bumpkin, rudder.


E.1 The overhang of the rudder is restricted to 51mm aft of the measurement box.

E.2 Except for the rudder, the following are prohibited: retractable and or movable hull


E.3 Rudder thickness shall not exceed 6.3mm.

E.4 Materials shall not be of density higher than lead; 11300kg/m3.

Also in addition to this there is somewhat of a confusion on my part re the Construction of the Box. I’ve seen many tact’s with some made from simple Ply to others made from 20mm MDF Board. Each have varying restrictive degrees on how a boat can be placed. The more robust teh construction of the Box in effect brings into play the 200mm guide slot to allow rudders which attach or are positioned under teh hull.

In progressing a Rule Interpretation I have provided for an attachment which hopefully explains what I am contemplating, albeit with a straight rudder and not one as described in my suggested alternative.

In summary
[li]Assumed the Boat is placed in the Box along the Vertical axes and is not slotted in from a variety of Axes merely to overcome a restriction or conversely to deny a competitors right to address the rules as they stand.
[/li][li]A rudder Attaching Post extends from the boat through the “V” to no more than 51mm aft of the interior of the box.
[/li][li]with a box construction of 1mm ply this could mean a maximum rudder width of 50mm.
[/li][li]A Vertical hole for Inserting Rudder is drilled through post.
[/li][li]The Rudder is attached through hole on rudder post by Tiller Arm Fitting.
[/li][li]The Rudder of varying length up to 250mm (possibly out to 305mm without ballast restriction), yet not more than 6.3mm in thickness, can be attached via rudder post with no part of the rudder entering the slot in box.
[/li][li]Can the Push rod be bent (say 90 deg) to accommodate a longer Tiller Arm? This might extend beyond the “V” but still fits within the box if placed from the vertical axes.
[/li][li]Construction Material could be Carbon Fibre, Glass, Ply, Aluminium or any other material lighter than current ballast.
[/li][li]Additionally can there be an Alternative consisting of;
[/li][li]varying shapes of rudders that could have a portion under the boat
[/li][li]extending downward and exiting the slot at less than 200mm
[/li][li]with a Vertical Thinner trailing section extending further downwards.
[/li][li]At no time extending along the Longitudinal axes greater than 51mm aft of the internal of the Box


[li]Greater Steerage Control in Gusts.
[/li][li]Marginal Performance Increases to Windward
[/li][li]Negligible but minor Benefits Running
[/li][li]Improved Tacking in higher winds
[/li][li]possible reduction in Ballast weight giving greater steerage control and increased all round performance due to weight displacement.
[/li][li]Less Weight - Less Force Require to move static object.
[/li][li]Greater Sideways Resistance against force of wind enabling a reduction in notional ballast

[li]Greater Drag
[/li][li]Greater Weight depending on construction.
[/li][li]Perception of unfairness and outside spirit of Box Rule 200mm Slot
[/li][li]High grade Servos Req’d
[/li][li]possible reduction in ballast weight and perception of using rudder as ballast

The only limitation on what I am proposing is where it states at Rule B:1, where it states, "the boat in racing trim shall be capable of fitting into…as shown in the diagram ".

This could be interpreted that some portion of the Rudder must fit within the confines of the Box. From here however my Alternative rudder configurations would seem to be applicable.

Can you investigate whether my Rudder Length is a problem within the rules and whether there should be a formal Interpretation Issued to clear-up any misgivings about what size rudder/ Length of Rudder can be used.

As an aside there has been some mention of foil rudders which if attached in my estimation would exceed the greater thickness of 6.3mm for the rudder. Are Foils on Footy’s permissible by way of attachment to the rudder and thereby not allowing passage through the slot.

My suggestion of longer than the box was merely to get the members of the Forum thinking of the possibilities where some unscrupulous sailors might try to exploit the rules to their benefit. To some degree this was successful, if somewhat naive on my part given the aversion to addressing rules and regulations within a developing Class .

Many Thanks & sorry for raising such an issue but the debate has grown beyond a simple request for feedback


6th January 2007

Hi John, we’ll talk over the length issue and give you an interpretation as soon as we can coordinate. I had an immediate reaction to your comments about the box, though, that I want to pass on to you. All length, width, and height dimensions of the box are interior dimensions. The 51mm extension of the box is measured, as indicated in the drawing, from the INSIDE surface of the box. Rudder extension, therefore, is consistent regardless of the material thickness used in box construction.

7th January 2007

The reason I mention the box size of construction is that if I use 1mm ply to construct, i.e. requiring 50mm gauge outside the box I have an ability to use a rudder up to 50mm in width which can extend downwards without any obstruction from the slot (has no need to enter the slot at any time).

If the Box were constructed from say 20mm board thickness, i.e. requiring a 31mm gauge outside of the box, for example then the rudder of 50mm in width would be restricted downwards by the 200mm slot blocking the rudder.

Same Box Internal Measurements but different thickness of construction provides for different outcomes,
i.e. One Fits & One Doesn’t.

Hence my inclusion and comments on the Box Construction as being perhaps a requirement in determining the Rule more effectively.

My Interpretation on the rudder length and the spirit and intent was that it should be limited to 200mm from sheerline. I’m happy with that if this were stipulated.

I would see however that a slightly longer rudder might be of great benefit to the Footy given its’ size.

I would see to restrict the rudder length by the inclusion of a stopper at the limit of 200mm which would be fair to all whether the rudder is external or under the boat. Box construction would then in theory not be an issue.

All this and my local club (scale boats) decided on one Design sailing as a first entry. Suck It and See was their opinion. Had to agree didn’t want to scare them off because of the ongoing design aspects etc.

Hope this clarifies my reason for raising the Box Construction as I feel it does have some impact on what can and can’t be achieved with different thickness of box construction material.


8th January 2007

Point well taken, John…sorry I didn’t get it the first time! We’ll have
to consider making the box of standard material thickness. None of us
thought of it at the time we made the rule…even with three of us, we
weren’t smart enough to anticipate everything.

9th January 2007

My Fuzzy Logic kicked in when I was playing with the imaginary box (computer drawing). Constructed a cardboard cutout of a stern from free plan with my rudder mods. Looked good in principal until I messed around with the box end I constructed (not complete)

Couldn’t work out why the rudder didn’t fit even after I double measured. Two glasses of Margaret River Red and it dawned on me the Box was 1mm in my head and 10mm in reality…

Looks like the interpretation request deals with two unexpected clarifications… Box & Rudder Length.

Sorry about that… Didn’t mean to push the envelope, it was just an innocent question that got out of hand…

Anyway, happy to abide by any decision as the Fun & Spirit of the rule is more important to me than the advantages that might be gained by confusing people with legalisms and lawyer speak (as Angus put it) . Not my intention just a bad habit from Business Days that sneaks in every now & then.



Now it’s open for all to see what was discussed in the Interpretation Request. Delete the Post if you wish to censor or if its an open forum.

Had to somewhat edit the file attachment for size issues. Safe to say the detailed attachment was submitted to the Technical Committee.

They would have to agree it corresponds to the explanations provided and Interpretation sought.

The first thing I think of when you mention a very long rudder blade, is that if the shaft isn’t strong enough or if the shaft log isn’t mounted strong enough the rudder blade will start to flap in the water, which is not good all.

Otherwise, the most important question to be, what is the smallest practical size of a rudder blade, to provide steering. You’ll have to consider all the stress factors on the hull to deternmine that.