Originally Posted by Paul L
Interesting, I guess I think of a balanced Spade as one that is totally held by its shaft and with a portion of the area in front of the shaft. If you removed the 'lobster strap' I guess the IP would qualify. Is the strapping really not structural? If this a spade rudder, how come they have such a poor rep for backing up? Or is that myth too?
I believe not backing up well is more of a function of a full keel
than what type of rudder. If I can get 1 kt backwards, she will turn in either direction, or if barely moving if placed in neutral, inertia will carry her in either direction (assuming no wind). It's getting her going until there is enough water
flow over the rudder for it to become effective that it prop walks to port, remember of course the only flow of water
over the rudder in reverse is from the boats movement, in forward of course wash off the prop goes over the rudder and it's very effective, so if you find yourself slowly backing to port towards a post for exampe, a quick blast of fwd thrust with the rudder held to port will bring the stern smartly to starboard without any forward movement of the boat.
Personally once I got used to it, knew how much of it there was, prop walk became my friend. Great for coming along a dock
, just before the port side bow touches the dock
, rudder over to starboard, and a good shot of reverse prop walks the stern in leaving the bow where it is
It's a post hung spade rudder, the lobster strap supposedly isn't required structually, but obviously does add to the strength and protection. Being a balanced rudder is why they have light wheel
force and can get away with that little wheel, of course you can balance a skeg hung rudder too.
I'm the furthest thing from a Naval Architect, but as a novice
looking at the thing, IP's seem to be sort of a modernized version of a classic design, a purist may tell you it's not really a full keel
either, and they may be right.
Last comment, you know the Elephant in the room, how many IP's have broken up and sunk this year?