Rudder type

[ppaalo]

Just lifted our Albin 25 for the first time (it was in the sea when bought 6 weeks ago) and was surprised to see the rudder, it's not the kind I've seen on other people's pictures:

albin_rudder.jpeg

What is that kind of rudder even called in English? Short googling didn't help me much...

[Tree]

It's almost like a Kort Nozzle - except it turns.

[Dieselram94]

That’s interesting, how well does it work?

[kerrye]

Fascinating. I'd like to see a side by side comparison of that and a typical rudder. I wonder why it was installed. My suspicion is that it wouldn't work as well in reverse as a standard rudder but maybe it sucks a lot of water thru it making it more effective in reverse. Never seen anything like it.

[kerrye]

I looked up Siuntio. Your coastline looks like a fascinating place to cruise.

[DesertAlbin736]

What is that kind of rudder even called in English?

I think the English word you're looking for is "Bizarre".

Interesting though. I wonder how effective it is compared to a conventional rudder? Certainly one of a kind for an Albin 25. Someone went to a lot of effort to make & install it. Could it have been a one-off experiment by Albin?

[ppaalo]

It's pretty bad going in reverse but feels good going forward. Haven't driven any other kinds to compare but doesn't that sound like the behaviour of the original/normal rudder

Did even more googling and yet to find a single picture of a similar kind of rudder, strange...

[kerrye]

Yes, you're right. It would be hard for rudder performance in reverse to get worse.

[DesertAlbin736]

It would be hard for rudder performance in reverse to get worse.

True. Very few single screw inboard boats are good at backing up, especially those trawler types with fixed prop. In turns going forward a conventional rudder deflects half of "prop wash", that is the half striking the turned rudder, the other half going past it. This nozzle ring type would tend to deflect all or most of the prop wash somewhat like the turned lower unit of an outboard or I/O drive. But only in forward gear. In slow speed reverse "prop walk" would be the dominant force until the boat gets moving enough to have water striking the rudder. Just looking at it one wonders if it is even as effective as a normal rudder in forward and even less so in reverse. These rings, or Kort Nozzles if you will, are often seen on outboard sailboat kicker motors, mostly as a propeller guard safety feature. Kort Nozzles lose their performance advantage at speeds over 10 knots because increased drag exceeds the benefits of the nozzle.

But a Kort type ringed rudder is truly unique and would be an interesting study comparing effectiveness vs drag to conventional rudders. My guess is there's a reason why they're hardly ever seen.

https://en.wikipedia.org/wiki/Ducted_propeller

[Beta Don]

The simple solution for improved rudder performance is to add to the leading edge of the rudder, ahead of the pivot point, so when the rudder is turned it deflects more than 50% of the prop wash

On my early A27 with the big 'barn door' fiberglass rudder I added 4 inches to the front of it. I tapered a 2 X 4 and lag screwed it to the front of the rudder and then covered everything with many layers of fiberglass cloth soaked in epoxy resin. I faired it all out perfectly and the result was a much more aerodynamically shaped leading edge

Even just a 4 inch addition can reduce the turning radius by nearly 50% because you are catching a much larger percentage of the propwash from a 15 or 16 inch prop. This also makes the helm much lighter feeling since that new extra area is balancing out the rudder somewhat. If you're unhappy with how your boat responds to the rudder, especially during slow speed maneuvering, adding to the leading edge can make a real change in how the boat handles, especially while docking - The bow thruster I added made a huge difference too!

Don

[Sprig1]

I can wholeheartedly agree with Don. When he suggested the rudder extension I did mine. It does seem to backup some what. You make all your corrections going forward. The helm feels pretty light. But I have no reference since this is the only boat of this type I've driven. Thank you Don. Sorry to high jack thread

[DesertAlbin736]

The simple solution for improved rudder performance is to add to the leading edge of the rudder, ahead of the pivot point, so when the rudder is turned it deflects more than 50% of the prop wash

My stock rudder is already somewhat "balanced" with the leading edge 3 or 4 inches ahead of the rudder stock pivot axis & is a fairly light helm. Unlike a sailboat, there's no issue with "weather helm". As it is there's barely room to add a prop nut zinc & no room at all to add a shaft collar zinc ahead of the prop.

[ppaalo]

As an FYI it seems this rudder type is not that unusual, asked around on a Swedish forum for Albin 25 owners and got multiple reports of similars on their boats so it must (?) be an original. And no one had experience with "both" so could not say which handles better.

[DCatSea]

It almost looks as if someone tried to build a Kitchen Rudder, (Not "Kitchener" BTW) which was a much loved device in use on Royal Navy cutters and other War Department small craft in the early to mid 20th century. It involved a split conical tunnel rudder that could be altered from the tiller to change the direction of water flow for'd and aft. There is a much better description at https://en.wikipedia.org/wiki/Kitchen_rudder.

I had the pleasure of using one on a Thames launch in the 60s, and now that I have been reminded of it, I wish I had one on Mazboot. This would be tricky, because it needs tiller steering, but what a difference it would make when going ass-first.

Also, see the ref. to a Kort Nozzle.

[DCatSea]

Like DesertAlbin, I googled Siuntio to see it on the chart. Wow! - I am very impressed - great Albin cruising waters. Hope you enjoy your 25.

Nice to know that AOG reaches Finland as well. Welcome Aboard - Tervetuloa mukaan; (hope that's correct).