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Old 25-07-2013, 16:22   #1
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Question Rudder Design

Does anyone have any good information on the durability (both over time and under stress) of the various rudder designs? Also interested in the effect that the type of rudder has on the boats ability to back under control.

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Old 25-07-2013, 16:58   #2
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Re: Rudder Design

When you say rudder design can I assume you mean:
keel hung
hung on a partial skeg
unprotected spade rudder
transom hung, both fixed and kick up.
And whatever type I've forgotten.
The keel hung is more protected if you're going to run into stuff, and the kickup has more moving parts to fail.
Aside from that, I think the quality of construction is the most important factor.
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Old 25-07-2013, 17:27   #3
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Re: Rudder Design

Yes - that's basically what I had in mind. I'm trying to guage the validity of my own bias (based on reading rather than personaly experience) against the type of arrangement common on most modern production sailboats - a spade rudder behind a pronounced fin keel.
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Old 25-07-2013, 17:31   #4
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Quote:
Originally Posted by Dave6330 View Post
Yes - that's basically what I had in mind. I'm trying to guage the validity of my own bias (based on reading rather than personaly experience) against the type of arrangement common on most modern production sailboats - a spade rudder behind a pronounced fin keel.
What is the point in presenting information to someone already biased. ??


Go sailing build done experience , then form an opinion. Rather then reading one biased opinion or another.
Dave
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Old 25-07-2013, 18:12   #5
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Re: Rudder Design

Given that the purpose of a rudder is to steer the boat, the best rudder is the balanced spade.

The thing is you can not plan to run around hitting stuff with it. Which means the most important thing to a rudder is that it isn't longer than the keel.
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Old 25-07-2013, 18:21   #6
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Re: Rudder Design

Makes sense - so the balanced spade is more effecient than a skeg or keel hung rudder? That's the most common type on the current production boats, isn't it?

Have you ever damaged one? Isn't going aground a fairly common occurance? We have VERY deep water up here but I understand that a soft grounding is not at all uncommon in the lower 48.
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Old 25-07-2013, 18:50   #7
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Re: Rudder Design

Don't ever remember seeing a boat underbody with the rudder as deep or deeper than the keel . Even a full keel boat rudder attached will have the rudder a few inches above the keel. Still, running aground often bends the rudder shaft on spade rudder boats. It is less likely with a skeg because of the extra support that the skeg supplies. That's not guaranteed, however. A boat with a skeg rudder recently sunk in Florida after it had a gentle grounding on a mud bar and the skeg ripped off. Full keel boats usually fair well in a grounding because of the length of the keel and strong support of the rudder at the top and bottom and often along its length.

As far as handling, spade rudder boats turn on a dime and usually will back with control. Boats with skegs are slightly less maneuverable but still pretty easy to control. Full keel boats can be a handful going both forward and back. My W32 would back reliably once she was moving in reverse then put the engine in neutral. Had a pretty wide turning radius but never had an issue getting her in a slip. My Pearson 35 with it's shallow full keel with cutaway forefoot is a nightmare. It goes where it wants, when it wants in revcerse. I just put it in reverse and pray it goes somewhere I want. Sometimes it will swing in the direction I want but other times will end up backing who knows where and hoping to be able to put it in forward and turn in the direction I want to go before hitting something. Often takes several tries to get moving in the right direction. Going forward has better control but still a pain if the wind is blowing into the slip. If the wind is above 10k, the bow falls off as it reaches about 45 degrees to the wind will not continue turning. Have had that happen twice and, strangely, after a lot of backing and filling ended up backing into the slip.

I ran the small skeg'd Morgan 35 aground a bunch in the ICW. Never had a problem as it was mud and kedged off from the stern. Having said that, practically every boat yard I've been in has a trophy spade rudder with a pretzel shaft. Think most of them get in trouble when they run aground going forward and current, waves or a tow boat swivels them around the axis of the keel. Have gotten away from sailing in thin water so haven't had much experience running aground recently. The one time I ran aground in a full keel boat, just put out a kedge anchor and waited for the tide to lift the boat off with nothing but a few scratches to show for it.
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Old 25-07-2013, 19:41   #8
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estarzinger

Spade rudders offer better control.

As to durability, it all depend on how they are designed and constructed. You can have a weak skeg. You can also have a very strong spade . . . . We have one if those . . . . 5" solid aluminum shaft and 10mm skins . . . . Have twice accidentally bashed it very hard on rocks, did not break.

One thing that's not often mentioned about spades, is that you can pretty easily drop them out of the boat while the boat is still in the water, to inspect or repair them. With a skeg you pretty much have to be hauled out to work on the rudder.
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Old 25-07-2013, 19:48   #9
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Re: Rudder Design

The balanced spade will steer better in forward or reverse... but it's a big generality. it's the most unprotected, and I know two boats personally that bent theirs badly. Every thing is a trade off. A spade is such a pleasure to steer with compared with an unbalanced rudder....
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Old 27-07-2013, 09:18   #10
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Re: Rudder Design

Quote:
Originally Posted by roverhi View Post
Don't ever remember seeing a boat underbody with the rudder as deep or deeper than the keel . ---
Actually there have been a number of boats made with that flaw. Usually happens when the manufacturer offers a shoal draft keel option but doesn't redesign the rudder. I think Catalina made several models with that problem, probably some other manufacturers also. Hopefully the practice has stopped.
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Old 27-07-2013, 09:22   #11
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Re: Rudder Design

Quote:
Originally Posted by FSMike View Post
Actually there have been a number of boats made with that flaw. Usually happens when the manufacturer offers a shoal draft keel option but doesn't redesign the rudder. I think Catalina made several models with that problem, probably some other manufacturers also. Hopefully the practice has stopped.
Yep, I have seen Catalinas with a wing keel and a spade rudder that was noticeably deeper than the wing... a REALLY bad idea IMO. What are they thinking???

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Old 27-07-2013, 10:03   #12
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Re: Rudder Design

Could be the laminate in the lower part of the rudder a bit thiner so in case of grounding or collision the rudder take the impact in the lower section saving the top portion of the rudder and saving the rudder stock integrity?? I wonder if this solution can work with long spade rudders ... something like loosing the lower part and saving the top...?
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Old 27-07-2013, 10:05   #13
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Re: Rudder Design

A few interesting discussions:

Are Spade Rudders A Good Option For Ocean Going Sailboats?
Boats.
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Old 27-07-2013, 20:02   #14
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Re: Rudder Design

Quote:
Originally Posted by Jim Cate View Post
Yep, I have seen Catalinas with a wing keel and a spade rudder that was noticeably deeper than the wing... a REALLY bad idea IMO. What are they thinking???

Cheers,

Jim
They were thinking they could save money by just using the same rudder for the wing as for their deeper fin. More about money than common sense. I do like Catalinas but there have been some errors.

kind regards,
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Old 27-07-2013, 22:49   #15
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Re: Rudder Design

Brand new shinny Hunter 50s come straight from the factory in the USA with a long dangly exposed fin/spade type rudder the same depth as the keel (or very close)... not shoal keel either AFAIK.

From my experience it is no fun running aground with that type of rudder.
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