Balanced spade rudders with only one support for the shaft - at the top
- are far more prone to failure than rudders with top & bottom support
as provided by a full keel.

Thought that was obvious.

Keep in mind the discussion is seaworthiness, not performance.

In article , Donals Dilemma
wrote:

On Wed, 03 Dec 2003 16:14:37 +1100, Peter Wiley
wrote:


On boats with unseaworthy, poorly (or no) supported rudders, yes. On
boats designed for extended cruising with a protected and well
supported rudder, no. Which category does yours fall into?

PDW

Huh?



Oz1...of the 3 twins.

I welcome you to crackerbox palace,We've been expecting you.

I can see an enginnering basis for that asserion but is it really true?
The rudders with top and bottom support should have a thinner stock
which would break more easily if the boat fell back from a breaking
wave??? Of course impact damage to spades is different problem...

Cheers MC

Peter Wiley wrote:

Balanced spade rudders with only one support for the shaft - at the top
- are far more prone to failure than rudders with top & bottom support
as provided by a full keel.

Thought that was obvious.

Keep in mind the discussion is seaworthiness, not performance.

In article , Donals Dilemma
wrote:


On Wed, 03 Dec 2003 16:14:37 +1100, Peter Wiley
wrote:


On boats with unseaworthy, poorly (or no) supported rudders, yes. On
boats designed for extended cruising with a protected and well
supported rudder, no. Which category does yours fall into?

PDW

Huh?



Oz1...of the 3 twins.

I welcome you to crackerbox palace,We've been expecting you.

It does seem to be true in practice, from what I've read. You need
better engineering to build a spade rudder properly than for a rudder
supported top & bottom. Therein lies the rub....

Spades are a lot more likely to be damaged from impact but is this a
seaworthiness issue? Most small boats aren't designed for collisions or
groundings and really only steel copes reasonably well with one if it's
rock or coral.

Spade rudders are also a lot better for snagging mooring lines, pot
lines, gill nets etc etc.

I have a few other problems with these sorts of thing but they're all
related to maintenance in places with minimal facilities, not
seaworthiness issues. I've seen, for example, an awful lot of rudders
where the shaft is a solid rod from tiller to rudder bottom. This is
wonderful - until you want to remove the damn thing and oooops -
where's the big hole to drop it into under he boat? Better hope the
tube is brought above the WL if you're going to drop it in the water.
Now, if it's a spade rudder having a flange under the hull & the rudder
blade bolted to it is going to require a bigger flange/stronger bolts
than the same for a keel hung one. Is it worth the hassle? Depends on
where you're going to go.

How about rod rigging? Is this seaworthy? You aren't going to fix a
broken rod easily. An engine buried under a cockpit sole requiring a
contortionist midget to service it, and a chainsaw to get it out if it
breaks? Ditto lack of access to stern glands. Personally such things
interest me far more than whether a vessel has an EPIRB, a SSB or a
liferaft. Those things only help you (at public expense) to be rescued
*after* you have a major problem.

Engineering for long-term maintenance isn't necessary to have a
seaworthy boat, but it saves a lot of pain down the track.

Did Bill Tilman have a seaworthy boat? Would it have passed your NZ
compliance rules?

PDW

In article ,
The_navigator© wrote:

I can see an enginnering basis for that asserion but is it really true?
The rudders with top and bottom support should have a thinner stock
which would break more easily if the boat fell back from a breaking
wave??? Of course impact damage to spades is different problem...

Cheers MC

Peter Wiley wrote:

Balanced spade rudders with only one support for the shaft - at the top
- are far more prone to failure than rudders with top & bottom support
as provided by a full keel.

Thought that was obvious.

Keep in mind the discussion is seaworthiness, not performance.

In article , Donals Dilemma
wrote:


On Wed, 03 Dec 2003 16:14:37 +1100, Peter Wiley
wrote:


On boats with unseaworthy, poorly (or no) supported rudders, yes. On
boats designed for extended cruising with a protected and well
supported rudder, no. Which category does yours fall into?

PDW

Huh?



Oz1...of the 3 twins.

I welcome you to crackerbox palace,We've been expecting you.

Peter Wiley wrote:

It does seem to be true in practice, from what I've read. You need
better engineering to build a spade rudder properly than for a rudder
supported top & bottom. Therein lies the rub....

Spades are a lot more likely to be damaged from impact but is this a
seaworthiness issue? Most small boats aren't designed for collisions or
groundings and really only steel copes reasonably well with one if it's
rock or coral.

Spade rudders are also a lot better for snagging mooring lines, pot
lines, gill nets etc etc.

I have a few other problems with these sorts of thing but they're all
related to maintenance in places with minimal facilities, not
seaworthiness issues. I've seen, for example, an awful lot of rudders
where the shaft is a solid rod from tiller to rudder bottom. This is
wonderful - until you want to remove the damn thing and oooops -
where's the big hole to drop it into under he boat? Better hope the
tube is brought above the WL if you're going to drop it in the water.
Now, if it's a spade rudder having a flange under the hull & the rudder
blade bolted to it is going to require a bigger flange/stronger bolts
than the same for a keel hung one. Is it worth the hassle? Depends on
where you're going to go.

How about rod rigging? Is this seaworthy? You aren't going to fix a
broken rod easily. An engine buried under a cockpit sole requiring a
contortionist midget to service it, and a chainsaw to get it out if it
breaks? Ditto lack of access to stern glands. Personally such things
interest me far more than whether a vessel has an EPIRB, a SSB or a
liferaft. Those things only help you (at public expense) to be rescued
*after* you have a major problem.

Engineering for long-term maintenance isn't necessary to have a
seaworthy boat, but it saves a lot of pain down the track.

Did Bill Tilman have a seaworthy boat? Would it have passed your NZ
compliance rules?


It sure *looked* like a good seaworthy boat. Don't forget the safety
inspection includes the abilities of the skipper.


Cheers MC

In article ,
The_navigator© wrote:

Peter Wiley wrote:
[snip]

Did Bill Tilman have a seaworthy boat? Would it have passed your NZ
compliance rules?


It sure *looked* like a good seaworthy boat. Don't forget the safety
inspection includes the abilities of the skipper.

Hmmm, that's basically an avoidance answer. Would Tilman's boat have
passed the NZ compliance rules or not? It's a really simple question.

Peter Wiley

Since it's not available for my inspection how can I say?

Cheers MC

Peter Wiley wrote:

In article ,
The_navigator© wrote:


Peter Wiley wrote:

[snip]


Did Bill Tilman have a seaworthy boat? Would it have passed your NZ
compliance rules?


It sure *looked* like a good seaworthy boat. Don't forget the safety
inspection includes the abilities of the skipper.


Hmmm, that's basically an avoidance answer. Would Tilman's boat have
passed the NZ compliance rules or not? It's a really simple question.

Peter Wiley

Peter Wiley wrote:

Balanced spade rudders with only one support for the shaft - at the top
- are far more prone to failure than rudders with top & bottom support
as provided by a full keel.

Thought that was obvious.

Keep in mind the discussion is seaworthiness, not performance.

Well, a spade rudder hung on a post, with no other support, can be strong
enough. It takes more care with the engineering & materials than most
mass-produced boats can muster.

One of the problems I've seen is that high loads on these type rudders tend
to increase play at the bearings & bushings, which then results in impulse
loads as it begins slamming back & forth. Then the post starts to bend more
on each cycle and fatigues more rapidly. Next thing you know, all you've
got down there is twisted stub.

Another great flaw in 99% of production boats is that the emergency tiller
is laughable.

Fresh Breezes- Doug King