Hi Mike,   What is your own interests? Prospective project? Bought plans yet? And where are you located?   Fair enough on pin corrosion - is that because of wear at that point  - I am not familiar with stainless pintles really corroding much. Was that the lower - probably sometimes submerged part that is down near to the waterline?   My point was though that these rudders are so much more heavily loaded. Also that the transfer of load must be taken all the way through into the hull and bulkhead (or crossbeam if that is your preference).   I am not fully sure what was really the problem on Rare Bird - I have used the stainless steel pin through two gudgeaons on sidecar and actually bent the pin because my points of connection were too close together. I think my glass gugeons also were ripped apart for the same reason. Spacing out vertically further was the easy solution there. This is also a good thing to avoid what Rob said he found happened on El when at high speed his steering was pinched tight and stuck solid.   Also I might mention that a good observation I have made sailing on Sidecar in shallow water is that the steering, control and so on is actually quite good when there is practically no rudder left down at all. I mean that when I swing the rudder back in about a foot and a half of water I can still sail oncourse and steer. Herb could back that up, as we were running over some shallows fairly often around the edges of the Walpole inlet. And because of the balanced shaft type of steering it has no extra weather helm like you get on your transom swing up style rudders.   Doug Western Australia. --- On Mon, 16/5/11, Mike Crawford <mcrawf@nuomo.com> wrote: From: Mike Crawford <mcrawf@nuomo.com> Subject: Re: [harryproa] Practicality please To: harryproa@yahoogroups.com.au Date: Monday, 16 May, 2011, 9:24   <<Okay so this is obviously an America's Cup analysis now.>>   Yes!  But aren't we lucky to have Rick to take this from the realm of opinion to numbers?  We've hashed this over for years, and it's great to see a real discussion of the impact. <<Rare Bird hardware failure is easier to explain as underestimated rudder loads.>>   As I recall, the stainless pin was corroded almost completely through when it failed, so I wouldn't necessarily chalk this up to underestimated loads.    That said, twice the pin size could handle twice the corrosion, so I definitely support the new beefier pins.  And if the new pins are a better grade of stainless (perhaps the old ones were sold as grade A, but were really grade B), so much the better.  I'll bet that the new ones weren't from an anonymous low-cost asian supplier who takes liberties with grading. <<When people listen to the BD debacle it must be a put off.>>   I imagine so.  That's the problem with a public forum that discusses works in progress.   One thing that some forget is that BD has very challenging design criteria -- going for very shallow draft, while also allowing kick-up foils to handle the skinny water, is a tall order.  This has been complicated by BD's governing committee having not quite yet worked hand-in-glove with Rob as a team to sort out all the factors.    Solving the problem will probably require a continuous feedback circle, where Rob can make suggestions, the committee can verify the results of all the suggestions, allowing Rob to hone in on what to do (perhaps with the help of knowledgeable contributors like Rick).  And so on, through several iterations.  Rudolph has thankfully been very open and patient.  <<I am talking about real visible stuff, not a number on a page.>>   And the good news is that you've verified how well things can work, even without the extra knot or two of optimization.  That's more than most of us can say.         - Mike   Doug Haines wrote:   Okay so this is obviously an America's Cup analysis now. We can play at being Ben Lexcen's. (Ben Lexcen was the designer of Australia two's winged keel back in1983)   I think that if you can see air bubbles eg. in the wake, or waves formed from the objest when it is underway, then you must have turbulence or resistance ie energy lost.   If it is smoothe and making no wake or frothy foam bubbles, then it must be pretty efficient. What I was finding on Sidecar, was that when the rudders were too small (0.8m underwater depth-draft) there was problems. I am talking about real visible stuff, not a number on a page.   This can be where critics can question the Harryproa legitimately, because some problems seem to occur with steering as well as with the drag. When people listen to the BD debacle it must be a put off.   Rare Bird hardware failure is easier to explain as underestimated rudder loads.   Doug