UncleBob said..

julesmoto said..

troubadour said...


Use a hole saw but very carefully. If it grabs it hurts

:) Thanks. Have to see if I've got one with smallish teeth. I am envisioning a mess with wire strands hanging out everywhere :-(.

The mess is nothing compared to the black s**t that will be on your topsides if you ever use it as a fender.

I meant as an emergency fender.

Ramona said

40mm hole saw in a cordless drill does it effortlessly. We did a heap of tyres in the tyre wall at the local hillclimb a few weeks back.

Nothing like someone who has done it. Thank you very helpful as usual :-)

julesmoto said..

2bish said..

Hi Jules, yes ... Let me know what you think of the vid.

Thank you for that.Yes it does seem impressive. Presumably folds into a relatively small package too.
Any idea what they mean by the predetermined maximum speed set by the owner at 1 minute 40 seconds? Is there some sort of adjustability.
The thing that always scares me about drouges is actually slowing the boat down enough to deploy them without ripping a winch or cleat out or snapping the rope.

Presumably the size ordered is fairly critical as well. My boat isn't that far above the limit for the smaller one but I noticed the next size up is said to be appropriate for boats a hell of a lot bigger at the upper end. Wouldn't want to get pooped regularly because it was too large.

Can't really test these things (as a sea brake) until you desperately need them so it is nice to know that they have tested them rather than relying on a home made tyre or milk crate that has never been tested in anger. The guidance as to the length and thickness of rope as well as weight of chain might be applicable to other homemade solutions.

I think there may have been some kind of adjustability in the very early models. Now that Burke manufactures them, they don't have it anymore. it stuffs into it's own bag with a velcro closure, flat package but it's still a relatively large diameter. I agree with Tarquin, if you only want it as an emegency steering device, then the smaller model and less line would suffice.

garymalmgren said..
Huntress wreck found.
I get the feeling that a sturdy skeg might be the way to go. Only saying that because that is what I have.
www.abc.net.au/news/2023-01-06/sydney-to-hobart-huntress-beached-cape-barren-island/101830434

There's skegs and skegs. Apparently a Moody sunk in the USA after the whole skeg ripped out, leaving a massive hole.

When I went sunfish hunting and snapped the spade, the rudder snapped off cleanly leaving the hull perfectly fine. Conditions weren't as perfect as Kankama recalls since at the time of impact the forward hand was watching the log which was reading over 9 knots, coming down from a 12 knot surf - that's quick for a half tonner, as shown by the fact that the rest of the halves were well astern at the time.

Designing a skeg that will take that sort of impact doesn't seem to be trivial engineering. Two Malos have suffered severe damage to the skeg, and they have a pretty good rep as a tough, well built boat; author Nigel Calder says his Malo was almost lost when the skeg partly fell off after running aground, and another Malo sank after suffering a similar issue. A Sadler 32, with skeg, sunk after rudder damage from an orca attack off Spain.

garymalmgren said..

Huntress wreck found.

I get the feeling that a sturdy skeg might be the way to go. Only saying that because that is what I have.

www.abc.net.au/news/2023-01-06/sydney-to-hobart-huntress-beached-cape-barren-island/101830434

Quite a few references quoting a 1% failure rate for spade rudders doing ocean passages. Skeg rudders often are matched with longer keels, which do provide more collision protection for the rudder area.

Chris 249 said.

There's skegs and skegs...

As I have posted here before my boat in the hands of a PO with a 2/3 skeg lost it's lower skeg to rudder pintle/ bearing off Bega causing the rudder to skew sideways and a massive leak necessitating an emergency pump out, rescue and tow. Upon buying the boat I chose to extend the existing 2/3 width bulkhead (which is about 2 ft in front of the skeg) so as to span the full beam creating a water tight compartment aft.

I seriously doubt that naval architects/designers (when most boats incorporated skegs 35 years ago) considered the relative strength of the skeg itself vs the surrounding hull structure so as to make them sacrificial. Anyone for a saw cut a third of the way through their skeg near the top? :-).

Speaking of the relative strength of bits and pieces on boats it is interesting that the keels of many modern catamarans are sacrificial comprising thick foam with a relatively flimsy skin relatively flimsily bolted to sturdy hull recesses.

Whilst on the subject of catamarans I also recently read that centre boards (which need to be constructed quite strongly due to the forces they are called upon to bear in large-ish vessels) have been known to slice through their centreboard casings and the bottom of the hull when grounding. Presumably the same would apply to maxis..Ouch!

In the same vein of sacrificial bits and pieces it is also interesting to note the appearance of load limiters and load measurement devices in modern rigging of fancy boats such as fancy catamarans and maxi s.

Kankama said.. Also I haven't ever hit a sunfish so that makes me a better helm.

Oooooohhhhhh........ I've been burned.

It took a lot of skill to find and hit that sunfish once I realised that the alternative was to face the forecast bash across the Strait and up the Tassy Coast.

garymalmgren said..
Huntress wreck found.
I get the feeling that a sturdy skeg might be the way to go. Only saying that because that is what I have.
www.abc.net.au/news/2023-01-06/sydney-to-hobart-huntress-beached-cape-barren-island/101830434

Given the topic here and the news about Huntress, I couldn't help wondering if they tried using any kind of warps / drogue to regain some steering before abandoning the vessel?

www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjf77C8tLX8AhU7ilYBHWAHAFMQFnoECAgQAw&url=https%3A%2F%2Fkrakenyachts.com%2Fwhats-wrong-with-spade-rudders%2F%23%3A~%3Atext%3Dor%2520towing%2520lines.-%2C%27%2Cwhales%252C%2520containers%252C%2520and%2520lumber.%26text%3DOne%2520case%2520highlighted%2520in%2520detail%2Cand%2520a%25201.5m%2520swell.&usg=AOvVaw0_N1dGVsPJFxwSIhZn4MPU
Sorry for the long link, but that is where I got the statistic on failure rate. Backed up by the latest S to H failure.

Long post

I like podcasts - 59 North are great and they had Bob Perry on. I have his books too, where he says that he saw some of his rudders supporting skegs. He reckons that new carbon stocks are stronger than old skeg rudders.

So I joined the Perry facebook group and he sometimes posts there. After a few weeks he had a rant about a client not liking his very deep spade rudders. I tried, (gently) to disagree with the idea that a modern skeg rudder would be weaker than an equivalently engineered modern spade rudder. I have built a few boats and designed a few rudders, I am nowhere near as clever as Perry but I understand basic cantilever engineering. I was polite. He didn't want to engage and got dismissive. His spade rudders are really deep. So I am not in the group anymore.

I do think sailors have a blind spot about rudders and I disagree with the Perry idea that you can build a spade rudder that is as strong as a skeg (especially from fore and aft impacts like those commonly caused by strinking bottom or objects). A modern skeg could have some rake to improve ability to ride over objects and can be made from high quality materials with a much higher second moment of area than any rudder stock. If you compare chop strand mat skegs with carbon rudders then you have a point but a equivalent modern skeg has much more area where it connects the hull than a rudder - it is simple engineering. A skeg can be slightly wider than a rudder shaft but much deeper fore and aft as well. Resistance to bending is related to the depth cubed - so any increase in dimension gives great returns on bending reduction and stress reduction too.

I think Perry's blind spot to spade rudders is reflected in many modern boats. His spades are very deep and this is problematic for those who run aground (which is everyone) and great rudders can lead to designers producing highly directionally unstable designs with easy to use low transoms. Then if the rudder breaks off then the boat is unusable.

I once was in a Laser clinic with some of Australia's best Laser sailors. The coach asked us to sail without using the rudder, no one could, even the best Laser sailors could not get a Laser to move without a rudder. My point is that designers will keep on designing Laser like yachts because they are fast and nimble, but they will probably be unusuable without the rudder. I can sail a 420 without a rudder but have to rake the centreboard aft (which you can't do in a yacht) and can only sail upwind and on a reach. Dinghy like shapes are inherently directionally unstable. So go out sailing without a rudder and if your boat is uncontrollable, then design an emergency system with permanent gudgeons somewhere and a shortened and easy to fit emergency rudder living in the bilge. The designers are enthralled with the performance of a nice deep spade, but it is the owners who have to put up with the significant ramifications of their failure. The washboard on a kite pole emergency steering system is a joke and may work on a Currwong 30 or S and S 34 but is probably useless on a modern dish shaped boat.

Kankama said..
Long post
A modern skeg could have some rake to improve ability to ride over objects

I think this is on advantage of the skeg which is often overlooked. As long as the gap on the leading edge between the bottom of the skeg and the blade is kept close then accidents with mooring risers and stray ropes can be avoided.

cammd said..

But really I think one of the reasons for the popularity of spade rudders among builders is cost, they are cheaper to build than a skeg, much of the modern design is as much about cost saving as it is about performance if we really get into the reasons behind why this over that, particulary in contemporary production yachts, it might be dressed up as performace but mostly its about cost.

I absolutely agree the default position for production boats is primarily cost, not 'best'. But that's not a fault of spade rudders per se. IMO having dual rudders improve the benefits and mitigate the negatives even more compared to single spade rudders. I don't believe the hype about dual rudders increasing the possibilities of hitting stuff, it was always the keel which took the hit of any UFO's I experienced.
I could sit on the hard on my dual canted spade rudders (couldn't bring myself to do it, but it's engineered for it). I did it once inadvertently on a sandbank, it sat level, didn't dig in and floated off just fine. Was actually kind of cool!
-Dual rudders meant they were stubby which would aerate the windward rudder in anything over 20 degree heel, ie: little chance of hitting anything.
-The leeward rudder has enormous grip (canted==heel) even though it's a wee stubby thing. A 4' draft doesn't have much mass moving through the water to hit things and the grip is amazing, it's akin to being on rails.
- The stubbiness meant the rudder posts had much less shock loads. The similar distance between the upper and lower bearings with a shorter rudder meant less chance of damaging the post and bearings and making new holes in the hull.
-As you mentioned, the position of the rudders and the offset pivot can be chosen and not dictated by the keel shape and position. Which makes helming in any conditions a fingertip experience.
-Dead simple to remove and replace , I could drop a rudder out under 10 mins in the water. They don't take up that much space, I could fit a whole rudder in the rear cabin in the bookshelf.

Like everything in boats, it's horses for courses. Skeg hung rudders are damn good in some areas (eg: ice), spade rudders are damn good in others. I think we all agree one is not better than the other, they're just different.

DrogueOne said..
Alubat ovni has a bit of everything. I think there is a sacrificial 'something' that will allow the bottom bit to pivot if it hits something.

That's pretty interesting but the hydrodynamics of that upper section must be truly awful with that wide squared off rear end. Probably doesn't matter much because the laminar flow would have already been totally destroyed in that upper section by the skeg, prop and void.

One wonders whether perhaps a spade rudder with a bearing at the bottom of its pivot axis on a triangular plate stayed to the hull forward and to each side might have any merit? Would deflect objects and hopefully introduce only limited turbulence. Perhaps even a thin rod foreward. Works for rotating masts :).

One thing that has struck a chord with me after reading these comments is that a skeg mounted to the hull along a very short vertical portion of its upper regions may well not be anywhere near as well braced as a spade rudder with a bearing in the hull bottom spaced quite a distance from another bearing level with the cockpit floor.

cammd said..

julesmoto said..

One thing that has struck a chord with me after reading these comments is that a skeg mounted to the hull along a very short vertical portion of its upper regions may well not be anywhere near as well braced as a spade rudder with a bearing in the hull bottom spaced quite a distance from another bearing level with the cockpit floor.

Its the spade bit below the hull that breaks off, will be hard to steer with just a well braced rudder stock.

There are two priorities here. The first priority is making sure the boat doesn't sink. I'd much rather have no holes in the boat than a snapped off rudder, that's why hull and rudder post integrity is important.
The second is re establishing steerage. Whether your emergency tiller needs the post or some transom brackets is up to the individual boat.
Not much point having a flash washboard and guy pole setup for emergency steering if you've a dirty great hole in your boat that doesn't have a watertight bulkhead or any ability to plug a sheared off rudder post.

DrogueOne said..
Alubat ovni has a bit of everything. I think there is a sacrificial 'something' that will allow the bottom bit to pivot if it hits something.

Onvi's aren't as simple as they could be. There is a sacrificial stainless diaphragm in both the lifting keel and rudder hydraulics. If there is an impact the diaphragm splits andneeds to be changed and system rebled. Owners keep spare diaphragms in their spares kits. I assume they couldn't get a pressure release valve to dump fast enough to protect the boat.

Don't worry about the slot at the rear of the rudder, the bigger issue is most OVNI have a flat plate centreboard. They are not a boat designed to sailed close hauled for a significant passage.