Windie 14 tiebar length

[Hockeye]

Was just fitting up a new set of springs in my tillers over the weekend. Has everyone who's done this had to angle grind off part of the pigtail on one end of each spring in order to get the rubber knuckle on? Can the springs be pre- treated in any way to prevent corrosion?

I'm also replacing the tie bar between the tillers. I presume you set each tiller parallel with its hull, and with the deep water rudders toeing in before measuring the length of the tie bar to fit onto the rubber knuckles. Any tips would be appreciated.

Thanks

Hockeye

[tonyquoll]

Hey,

On paper tigers it's definitely best to have the blades parallel when in the straight ahead position. Handles are bent towards each other to provide toe-in, sorry haven't got the dimension handy.

The local champ here sails a Windy sloop with badly aligned rudders, which he compensates for by lifting the windward blade every time he tacks! Reckon it'd be more time efficient just to fix 'em.

Good luck with yours

[Hockeye]

The Windie 14 has a preset toe-in on the cheek casting that holds the rudder, relative to the tiller bars. I think that I should shorten my new tie bar so that the rudders are sligned with the hulls in staight-ahead position. This means that the tillers will both face inboard by the same angle as the toe-in.

Someone might like to explain to me how this helps. Is it to do with sailing on a reach or simply to shorten down the tie bar to keep the steering assembly generally within the hulls?

[tonyquoll]

Intro

Yep, agree on making the cross-bar length so that the rudders blades are parallel to hulls when both pointing straight ahead. Swing the blades to point backwards to help check this alignment.

The end result of bent handles and a shorter crossbar is that when you turn, the inside rudder is on more of an angle than the outside one. This helps reduce drag as you turn.

How it works is harder to explain:

Geometry

Having the pivot off-centre means that as you rotate each rudder arm, then distance from pivot axis at the transom to pivot point at the cross bar varies, which in turn changes how far the bar moves laterally (across the boat).

If you imagine a point about which the boat turns, at right angle to the middle of the boat, then draw a circle from that point through each rudder. The one on the outside is a bigger circle, and smaller angle to the hull, while the one on the inside is smaller circle, and a larger angle.

I think this is referred to as the Ackermann steering geometry.

The bent rudder arms help achieve this.

Foil angle

If you angle a rudder blade (foil) beyond a maximum angle to the direction you're traveling ( and the water is flowing at past the foil) it will stall. When it stalls, it creates drag and very little lift, so the boat slows down but doesn't turn.

A bit like this:

The angle at which a blade stalls at depends on its shape, and how thick it is compared to its width (leading edge to trailing edge).

So, having bent rudder handles helps keep each foil within the range that it works without stalling, which helps make the boat turn without slowing down.

Tip

With the stall angles in mind, it's best to begin a tack by pushing the rudder across a small amount, then pushing further once the boat starts turning.

The guys who slam the rudders over hard are the ones who come to a stop during tacks and get run up the back of at mark roundings.

It can help to tie a bit of rope or elastic from the ear beam to the cross bar to limit how far the rudders can be angled.

Conclusion

Your ideal setup is well shaped blades with about 10% thickness to width, which can handle a reasonable stall angle, mounted on rudders which have toe-in to keep them flowing during a tack.

Regardless of hardware, each boat has a limit the rudder can be pushed to, beyond which they slow the boat instead of making it turn.

Hoped that helped, good luck!

[This message has been edited by tonyquoll (edited 26 February 2010).]

[Hockeye]

Tony

Your detailed reply is much appreciated! As an ageing mechanical engineer, I got your "drift". I used to sail a cat rigged Hawke surfcat in WA in 1975 and later at Vic's surf beaches. Enjoyed breaking masts whilst broaching on large waves! However the thrills were many, except for nearly slicing myself in half on a shroud once when my leward nose dug in on lumpy seas and the boat cartwheeled! I'm looking forward to getting my S/H aged sloop rigged Windie 14 revived and into some flat water sailing, even if I have one new and one old deep water rudders.

Regards

Bruce

[tonyquoll]

Cool.

A few weeks ago cartwheeled and did a faceplant onto stay wires - on flat water. Interesting look with a big red line from forehead to chin. Note to self; "dont bear off sharply in strong gusts!" I've also learnt to have the vang loose downwind which makes a huge difference.

Those mis-matched blades will be annoying. I've been running a crappy old 'spare' on one side lately & found I can tack well onto port, but kept getting into irons going to starboard.

Damn rudders, must've spent more time designing, shaping, building, fibreglassing and modifying them than all the rest of the work on the boats put together, AND still to do a heap of work there.

All worth it when you're flying low over the lake, at one with the wind.