Hi George,
You can make the rudder any foil you want....... but same as sails, performance can suffer
with a lesser design. Symmetrical has somewhat less lift than the specified NACA 0012.
Symmetric would definitely be OK under normal operating speeds. Maneuvering in marina
may not be so good or possibly very hazardous in a following sea. So option would be
longer-deeper rudder. Always a trade -off in solutions. I will be trying shorter, (1) meter
deep with endplate for reduced vortex shedding and avoid cavitation. My boat will be in
the Carolinas so more bottom changes and ICW issues. Less draft always better.
My rudders will be driven by wormgear to spur gears on the rudder shaft, infinite rotation.
Not expecting much feedback which is better for me. Only autopilot solution so far for
these boats is a Raymarine wheel pilot and they have NEVER been very robust. (bring
spare parts) So less effort they have, longer they will work. Don't think any autopilot has
been actually performance tested on an HP boat. Expensive toys to play with.
Have no idea yet if mine could ever self-steer. No jib or foresail to balance response. Am
REAL sure I could lock wheel for a minute or so.
I agree with Rob you could rudder brake but shear plates if designed to trip on hitting
bottom should have sheared the retaining plates if you are braking at at any significant
speed. For instance: 90 degree stalled HP rudder per Rob Denney Visionarry design at
1.2meter depth: 7 knots 395 kg, 10 knots 808 Kg, 15 knots 1818 kg ( if you didn't shear
the plates your rudder post might have) and 20 knots 3232 Kg. My reco bad idea. Be nice
to your rudders and they won't float away.....
Just need to get some boats out there and try a few things, carefully. Way too costly for
destructive testing, right ? George, planning to put your in the big bay or major cruising ?
Some great ideas for larger boats. Interesting to see what is the wind load on Seabattical
and other larger type. Difficult to keep the profile low.
Regards,
JT
--- In harryproa@yahoogrou
>
> If rudder is symmetric there would never be any reason to rotate more than 180 (and
likely less than + or - 45), You would simply switch leading edge on rudders when you
shunt.. Is this what you envision or will you expect to rotate rudder 180 when you shunt ?
If you do plan on rotating 180 then would it make sence to have a 40/60 or other balance
ratio on rudder so it will have a tendency to rotate on its own when you shunt. This would
also prevent ruder being stalled at 90 degrees and possibly risk braking sheer plate and
would add some feel to rudder .
>
> One other question I have had that may be related to rudder design is the ability of the
Harryproa to self steer by setting sail and locking rudder. It may require less than optimal
settings for top speed but is it possible to let boat steer itself and on what points of sailing
would this work best. This would be a good trait of the boat if it could be done without
the use of autopilots or wind vane, even if only as a backup for other system.
>
> Happy sailing,
> George Kuck
> Chestertown, MD
>
> Rob Denney <harryproa@.
> On Sat, Apr 12, 2008 at 10:31 PM, George Kuck <chesapeake410@
>
> > Hello Rob,
> > With wheel steering as on a 40' Harryproa will it rotate 360 and then have
> > to go back 370 to go an additional 10 degrees or will it be continuously
> > rotatable (to 370 or more). ? Will it be balanced so that there is no load
> > (50/50)or (40/60), or other ? Can rudders be rotated 90 degrees to use as
> > brake when at speed ?
> >
> > Happy sailing,
> > George Kuck
> > Chestertown, MD
> >
> >
> G'day,
>
> Continuously rotating. Pretty much balanced although there are
> variations in the balance depending on speed, course, foil shape,
> fairness and smoothness. You can use it as a break, at least until
> the sheer pin breaks.
>
> regards,
> Rob
>
>
>
>
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