Latest News: Forums Technical Rudder blades; Two types?

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  • #23010

    I’d like to make improve my boat’s offshore ability, especially in big seas and high winds.  My rudder blade is the older swept back model, but I’d like to know the advantages of the deeper straight down blades.  Do all racers use these and why?  Given the wetted areas are similar (are they?) then the drag comes from how much wiggling you do?  Maybe the deeper one stalls later?  Does one have a poorer failure history?  When rudders break, which bit gives: do blades ever shear off on their waterlines or is it pintels (or gudgeons) which fail?  Mine swept-back blade is slightly balanced, in that about 15% is fwd of the pivot line; certainly if its even an inch off fully down the helm feels heavy and pretty unpleasant.  Maybe a straight-down blade gives better control in extreme conditions?  Can anyone advise?  Thanks,  Jeremy Warren.  W10022 Hafren

     

    #23073
    Dave Barker
    Keymaster

    Hi Jeremy,

    I won’t attempt to advise, but I have used both patterns of rudder blade, so I’m aware of the main practical differences between them.

    The first difference that is immediately noticeable when helming is the lighter feel to the deep, narrow blade. This is unsurprising, considering the shape, but very obvious in comparison with the traditional pattern rudder. Clearly the additional length of the deep blade will be an important consideration in shallow waters, but the length may be part of its appeal to you for use in waves? (I seem to remember waves/troughs being the reason for the alternative pattern blade being introduced in the first place). It’s probably even more worthwhile to fit a protective metal tip to the deep pattern blade than to the trad!

    I would guess that the deeper, narrower blade would stall earlier, not later than the traditional pattern, but I have no evidence for this.

    Whether or not the rudder is somewhat balanced depends as much on the stock as on the rudder shape (and the position of the pivot hole). We use an alloy stock (RWO) and I’ve found that the pivot hole position on the official rudder drawings needs to be tweaked slightly to make the blade align “properly” with the leading edge of the stock. (Without this adjustment the blade would project forward towards the transom, but this has been the case with every rudder that we have used in this stock).

    #23076
    Swiebertje
    Participant

    The deep rudder is supposed to work better in waves but I find it only to marginally better. The old style blade is a little more sensitive in the sense you need less rudder angle to achieve the same. The choice of rudder is the last thing to worry about IMHO. Far more important is that it has no play what-so-ever. The least bit of play will ruin that all important feeling for  the boat through the tiller.

    Use a rubber hinge on your joystick and not one of those mechanical things. Get rid of that fluffy rubber hand hold on the joystick. Use some duct tape or ‘tennis racket tape’ instead. Don’t use an adjustable tiller, they always loosen at the worst possible moment. Buy one that is too long and saw it back to the length you prefer. (Or  make your own joystick from a piece of Aluminium pipe, a rubber joystick hinge and some tape and save some money).

    Make sure the tiller wedges in to the rudder stock and get rid of the tiller pin (used on old boats). Use a bit of bungee to ensure the tiller is pulled in to the rudder stock at all times. Check the taper of the rudder stock and tiller. Add a small plastic wedge if the fit isn’t perfect.

    Make sure the rudder and the rudder stock are perfectly parallel.  The rudder is supposed to float up when the downhaul is released. I have added an uphaul so I can tighten the wing nut a bit more to make sure there is no play between the rudder and the rudder stock. Obviously it then does not float up by itself anymore hence the uphaul. Mind you, it still comes up when it hits something under water. In some cases you may want to add a filler piece between the rudder and the rudder stock, again to minimize play.

    Check your centre board, its position fore/aft,  its angle of dangle and depth. Find the limits as defined by the class rules and make use of it. Make sure the CB meets the maximum allowed sizes.  IMHO, a well set-up CB makes you point higher and that is a far more effective way to win races than the choice of rudder.

     

    #23148
    john1162
    Participant

    I like the deep rudder blade with its lighter feel. I remember breaking the older pattern one which was originally swept back a little. I broached on a big wave and ripped the rudder fixings off, leaving me with a rudder on a stick. Interesting. With the deep rudder blade I have never felt as though I was anywhere near that position. Perhaps the 30+ year gap (experience) between then and now might have something to do with it though.

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