Re: a question about rudder angle
> About the best we can do is to agree on some arbitrary standardI've been waiting my whole life for someone to figure a way to get rid of time zones and the dreaded International Date Line. But, seriously, if we have to change the clocks instead of going to work on Summer Hours, there's not much hope.
> calendar (Gregorian) and some arbitrary unit of time
> (the standardized second as definedÂ with reference toÂ
> the "official" atom - no kidding).Â All of which is quoted
> WRT an arbitrary point on the earth, UTC.Â And we're good to go,
> or as close as we're ever likely to get
>(maybe something will replace the official atom,
> that's about it really).
- As you probably know Phil Bolger has used end plates very successfully on several of his designs. He writes about them in his book "Boats With An Open Mind." I think he first used one on his Tiny Cat. It improved rudder control a lot on the old traditional catboat "barn door" rudder design. And the chapter on it explains why he felt it worked well. Catboats were notorious for bad steering control downwind.http://www.instantboats.com/images/tinycatst600.gifThen he tried them on his Micro series. The Micros have inboard rudders so a deep rudder that can be raised doesn't work with an inboard rudder. This also allows the OB to be mounted on the centreline of the transom and in-line with the rudder. And the rudder (and motor) are protected by the shallow keel forward. An inboard rudder is also an advantage on his Micro Navigator allowing one to steer the boat from inside the cabin with a shorter tiller.His original Micro plans did not have an end plate but now has been added and it did improve performance. But all these are flat-bottomed hulls so I think you are correct Graeme - probably not as effective on a vee bottom. And I think also work better in a design with more displacement . The inboard rudder is further forward and in deeper water than one hung off the transom, so is more effective even going downwind.Jim did design one hull called Eisbox that has the exact same rudder system as Micro - at the insistence of the person who commissioned it. But it had no shallow keel forward so needed a skeg ahead of it for protection. This meant the draft would be more and Jim doesn't like a hull with more than 4-5 inches of draft at most, so withdrew the plans for sale. I really liked the design and managed to convince Jim to haul out the mylars and send us some.Nels
--- In email@example.com, "graeme" <graeme19121984@...> wrote:
> I was reading where Jim Michalak said he had trouble not rounding up when running DDW with a shoal low aspect rudder with endplates. He fitted larger and larger endplates but without effect - the issue remained. He scrapped the rudder, fitted a deeper high aspect one, and fixed the trouble that way. He wrote he never went back to shoal rudders / endplates, and he has stuck with deep rudders since.
> Now surely past a certain point there is nothing to be gained by increasing the size of endplates - except an increase likely in wetted area drag... Endplates is endplates - to reduce losses at the foil tip. Why not test increasing rudder area before condemning/rubbishing low aspect rudders and endplates?
> Also, the issue was on one boat only. Short, wide, and deeply V'ed. The rudder may have been in surface layer water flowing with the boat on a run - dragged behind the V. The issue with any size endplate tried went away with broad reaching - perhaps leeway introduced some cleaner water flow to the rudder?