Schilling rudder project on narrowboat

[IanD]

12 minutes ago, Martin Nicholas said:

An update on the Drag coeffieicnts of Schilling rudder profiles, taken from
this reasearch. In a straight line, Cd ranges between 0.015-0.055 depending on the type of fish. A NACA 0024 foil shape was measured at 0.01 in this paper.

The introduction is a good read.

Yes that's true, and it's relevant to the normal rudder use case (where all the analysis is done) which is large relatively high-speed (typically 16kts) ocean-going ships, where a tiny increase in drag costs a lot of money, given fuel consumption of about 10 tonnes an hour for something the size of the Ever Given.

 

For a narrowboat travelling much slower than this in a canal where the rudder drag is much smaller and the profile/channel drag is much larger, the rudder drag -- Schilling or not -- is utterly insignificant, probably smaller than the sacrificial anodes, or other non-ideal hull features like too-short swims, protruding baseplate edges, BT tunnels...

Edited December 6, 2022 by IanD

[David Mack]

This drawing on the CRT archive shows what looks very much like a Schilling type rudder, described as a 'balanced reaction rudder'. The drawing is dated 1935 and shows a rudder which it appears was to be fitted to GUCCCo motor boats.

But were any boats actually so equipped?

https://collections.canalrivertrust.org.uk/bw58.10.6.3

[MtB]

On 04/12/2022 at 15:34, IanD said:

I know, but its owner actually knew his stuff about rudders...

 

 

And particularly, propellers IIRC.

 

 

[blackrose]

On 04/12/2022 at 13:03, IanD said:

And Dalslandia -- a voice of reason on the forum, sadly no more -- also had one. And a couple of others have tried them as well.

 

AFAIK every one who has tried one has been very pleased with the result, as have all the other users of them on low-speed non-canal boats where any extra drag is utterly insignificant, almost certainly much less than that from anodes... 😉

 

R&D would undoubtedly have found them unpopular because few people are willing to spend the extra money to have one made -- not far short of a grand today, for anyone interested. There's also the famous resistance of the canal world to anything new, on the principle that the ODGs knew best and nothing can possibly improve on the old ways of doing things... 😞

 

None of which changes the fact that all the analysis and trials have shown them to give better steering than a flat plate rudder, especially at large angles. Not saying that a boat can't steer well with a flat plate, but that it'd steer even better with a Schilling or similar rudder... 🙂

 

I've got to disagree with some of this. As I said previously, there are more significant factors that will make a boat steer well or badly than rudder design. 

 

I'm afraid this statement you made differs from what I've heard: AFAIK every one who has tried one has been very pleased with the result, as have all the other users of them on low-speed non-canal boats where any extra drag is utterly insignificant.

 

I've heard anecdotal evidence from one person who fitted a Schilling rudder and found it resulted in a lot of tiller vibration and it didn't improve steering at all. 

 

In general I agree with you but your statements are too absolutist. A boat may or is likely to steer better with a Shilling rudder is about as far as we can go - there are exceptions to the rule because of the other primary factors.

Edited December 25, 2022 by blackrose

[IanD]

9 hours ago, blackrose said:

 

I've got to disagree with some of this. As I said previously, there are more significant factors that will make a boat steer well or badly than rudder design. 

 

I'm afraid this statement you made differs from what I've heard: AFAIK every one who has tried one has been very pleased with the result, as have all the other users of them on low-speed non-canal boats where any extra drag is utterly insignificant.

 

I've heard anecdotal evidence from one person who fitted a Schilling rudder and found it resulted in a lot of tiller vibration and it didn't improve steering at all. 

 

In general I agree with you but your statements are too absolutist. A boat may or is likely to steer better with a Shilling rudder is about as far as we can go - there are exceptions to the rule because of the other primary factors.

You do know what AFAIK stands for, don't you? 😉

 

Of course the rudder is not the only thing that determines whether a boat steers well or not, but it is an important factor -- and the question is whether the boat handling is *improved* by the Schilling rudder. It might turn a poor handler into a barely adequate one if the rest of the hull is hopeless, but that's still an improvement.

 

If fitting one resulted in a lot of tiller vibration and no improvement in steering then that's strange, because it's not what the other reports *that I'm aware of* have found. Maybe there were other problems with the boat design, for example prop too close to hull (common in narrowboats) or rudder (less common), or the rudder balance was wrong.

 

It's also possible that there may be more vibration with a standard 3-bladed prop as the blades alternately pass the top and bottom of the leading edge of the rudder -- which is one reason I'm fitting a 4-bladed prop.

 

When my boat is finished I'm hoping there will be another similar boat in the water with a conventional rudder so we can make a direct comparison, maybe even some thrust measurements.

[Murflynn]

6 minutes ago, IanD said:

You do know what AFAIK stands for, don't you? 😉

 

 

 

yeah but .............  that just leaves you vulnerable to the suggestion that you don't actually know very much.

 

...............  just sayin'    😉

[blackrose]

3 hours ago, Murflynn said:

 

yeah but .............  that just leaves you vulnerable to the suggestion that you don't actually know very much.

 

...............  just sayin'    😉

 

Exactly.

 

Of course I know what AFAIK stands for, but prefacing one's knowledge of a subject with "as far as I know" doesn't preclude someone else offering additional knowledge or opinion.

[IanD]

4 hours ago, blackrose said:

 

Exactly.

 

Of course I know what AFAIK stands for, but prefacing one's knowledge of a subject with "as far as I know" doesn't preclude someone else offering additional knowledge or opinion.

My point was that I used that acronymn to make it perfectly clear that I was *only* speaking about what I knew about, not making an absolute statement of fact -- there aren't many Schillings on the canals but all the ones I'd heard of were happy with them, there are more in other lumpy water forums and again the feedback I could find is almost entirely positive.

 

Your anecdotal evidence (which is of course welcome...) is similarly what *you* have hard -- and (as you say) it's one anecdote, which I'd say doesn't outweigh the multiple other cases of "I tried a Schilling and it worked really well" if it comes to a balance between "it works" and "it doesn't work"... 😉

 

It would be interesting to hear more details about the "didn't work" case to try and figure out what went wrong, if you have them 🙂

 

(was it a properly designed/built/fitted Schilling or a "bodge job", was it sized and installed with recommended prop clearances, what type of boat/hull/prop...)

 

Of course confirmation bias might also exist on both sides -- if you build and fit a Schilling expecting it to be better then it's easy to be convinced of the fact, and the reverse if you expect it not to work. The only real proof is lateral/forward thrust tests, and the ones I've seen results for show that the Schilling is a lot better on low-speed boats (like narrowboats) than a flat plate, and if I get the chance I'll try and confirm this. But it will need another similar (but non-Schilling) boat for comparison, as well as strain gauges or spring balances to make the measurements, so I don't know if this will actually happen or not...

Edited December 26, 2022 by IanD

[ditchcrawler]

7 hours ago, IanD said:

You do know what AFAIK stands for, don't you? 😉

 

Of course the rudder is not the only thing that determines whether a boat steers well or not, but it is an important factor -- and the question is whether the boat handling is *improved* by the Schilling rudder. It might turn a poor handler into a barely adequate one if the rest of the hull is hopeless, but that's still an improvement.

 

If fitting one resulted in a lot of tiller vibration and no improvement in steering then that's strange, because it's not what the other reports *that I'm aware of* have found. Maybe there were other problems with the boat design, for example prop too close to hull (common in narrowboats) or rudder (less common), or the rudder balance was wrong.

 

It's also possible that there may be more vibration with a standard 3-bladed prop as the blades alternately pass the top and bottom of the leading edge of the rudder -- which is one reason I'm fitting a 4-bladed prop.

 

When my boat is finished I'm hoping there will be another similar boat in the water with a conventional rudder so we can make a direct comparison, maybe even some thrust measurements.

If someone spent three grand on a new fancy rudder do you think they would say it was crap. just like no one owns a crap car, everyone who spent money on a square bladed prop said they were wonderful, but not all of them kept them on. Because people say they are always good is not eveidence.

 

[IanD]

1 minute ago, ditchcrawler said:

If someone spent three grand on a new fancy rudder do you think they would say it was crap. just like no one owns a crap car, everyone who spent money on a square bladed prop said they were wonderful, but not all of them kept them on. Because people say they are always good is not eveidence.

 

Please read what I just posted, which said exactly this... 😉

 

P.S. Less than £1000... 🙂

Edited December 26, 2022 by IanD

[ditchcrawler]

What about this arrangement

 

 

[IanD]

5 minutes ago, ditchcrawler said:

What about this arrangement

 

 

 

Would be rather prone to damage on canals, and like a ducted prop (also used at sea in low-speed vessels like tugs) more prone to fouling -- meaning not just weed, but the other stuff you get round the prop on canals... 😞

 

Incidentally the Schilling rudder works very well, light and very responsive to steer, and when hard over (75 degrees?) the wash comes out sideways and the boat moves laterally as if there was a stern thruster. Which is nice because that's what I was hoping for, which I'm sure will disappoint the sceptics... 😉

 

I didn't get a chance to make a direct comparison or measurements because there wasn't time, but Ricky had taken the boat out several times on trials, and his assessment agreed with mine -- and unlike me he's done the same with several otherwise identical boats with bigger conventional flat-plate rudders. The only downside he noted was poorer steering when not under power when there's no prop wash over the rudder, which isn't a surprise given that it's considerably shorter than a flat plate rudder, but then this isn't exactly a common use case.

[JungleJames]

So a slightly larger Schilling is the answer!!

Anyway, I wouldn't expect much steering at under 4kts with no engine power. Certainly won't give you much control.

 

[IanD]

8 hours ago, JungleJames said:

So a slightly larger Schilling is the answer!!

Anyway, I wouldn't expect much steering at under 4kts with no engine power. Certainly won't give you much control.

 

Agree about the steering at low speed with no power, that's why I said it didn't bother me.

 

Given that the (smaller) Schilling rudder I've got already gives better steering response than any other boat I've been on, a bigger one would be overkill and just make the tiller heavier for no real benefit.

 

The other reason for me using this rudder was to reduce the amount the rudder protrudes past the stern of the boat (halved to about 8") to make it easier to get a 60' boat through the shortest locks on the Calder and Hebble, and this was successful -- we got through the shortest one (Salterhebble middle lock) without having to lift any fenders or have the rudder hard over... 🙂

[JungleJames]

3 minutes ago, IanD said:

Agree about the steering at low speed with no power, that's why I said it didn't bother me.

 

Given that the (smaller) Schilling rudder I've got already gives better steering response than any other boat I've been on, a bigger one would be overkill and just make the tiller heavier for no real benefit.

 

The other reason for me using this rudder was to reduce the amount the rudder protrudes past the stern of the boat (halved to about 8") to make it easier to get a 60' boat through the shortest locks on the Calder and Hebble, and this was successful -- we got through the shortest one (Salterhebble middle lock) without having to lift any fenders or have the rudder hard over... 🙂

Yeah complete waste.

The only reason you'd try turning with no power, is to reduce headway. But as a small Schilling basically does that anyway even with power, you may as well have the small Schilling, keep the power on, and keep control.

 

Your builder said the small Schilling was worse with zero power. Accepted. What he never said was the Schilling with power does as good as, if not a better job, than the conventional rudder without power.

[magnetman]

I like being able to steer the boat out of gear. It is a very important feature. 

[IanD]

3 minutes ago, JungleJames said:

Yeah complete waste.

The only reason you'd try turning with no power, is to reduce headway. But as a small Schilling basically does that anyway even with power, you may as well have the small Schilling, keep the power on, and keep control.

 

Your builder said the small Schilling was worse with zero power. Accepted. What he never said was the Schilling with power does as good as, if not a better job, than the conventional rudder without power.

 

Since he said it did a better job than a conventional rudder *with* power, I'm sure it's even better than a conventional one *without* power... 😉

 

He was impressed enough that he's going to offer it as an (extra-cost, obviously...) option on his narrowboats in future -- and especially if anyone requests a stern thruster, because it's just as effective, cheaper, quieter, more reliable, easier to fit in, and easier to use. Oh yes, and it acts as a rather more effective step for getting out of the water than "yoghurt-pot slashers" as well as avoiding the possible damage/snagging issues with them, which is why they were removed later on in the build... 🙂

 

[ditchcrawler]

43 minutes ago, IanD said:

Oh yes, and it acts as a rather more effective step for getting out of the water than "yoghurt-pot slashers" as well as avoiding the possible damage/snagging issues with them, which is why they were removed later on in the build... 🙂

 

Will you be chopping them off when you come out for blacking?

 

[IanD]

Just now, ditchcrawler said:

Will you be chopping them off when you come out for blacking?

 

I'm confused -- they're not there right now...

 

 

[ditchcrawler]

1 minute ago, IanD said:

I'm confused -- they're not there right now...

 

 

I thought it was your boat in build

 

[IanD]

2 minutes ago, ditchcrawler said:

I thought it was your boat in build

 

They both are -- the first (bare steel) photo was from Tim Tyler's workshop in June 2022, the second one was from launch at Finesse in Sept 2023...

[ditchcrawler]

28 minutes ago, IanD said:

They both are -- the first (bare steel) photo was from Tim Tyler's workshop in June 2022, the second one was from launch at Finesse in Sept 2023...

So you had it chopped off before completion. Makes sense. 

[IanD]

Just now, ditchcrawler said:

So you had it chopped off before completion. Makes sense. 

Yes -- actually Ricky chopped it off for the reasons I explained. See discussion about escape steps in another thread, the tiny half-moon "steps" are essentially useless (too high) but they "tick the box" that a means of escape must be provided...

[JungleJames]

8 hours ago, IanD said:

 

Since he said it did a better job than a conventional rudder *with* power, I'm sure it's even better than a conventional one *without* power... 😉

 

He was impressed enough that he's going to offer it as an (extra-cost, obviously...) option on his narrowboats in future -- and especially if anyone requests a stern thruster, because it's just as effective, cheaper, quieter, more reliable, easier to fit in, and easier to use. Oh yes, and it acts as a rather more effective step for getting out of the water than "yoghurt-pot slashers" as well as avoiding the possible damage/snagging issues with them, which is why they were removed later on in the build... 🙂

 

Good for you.

Should be applauded for daring to show what can be done.

Schilling rudders and 4 blade props should be a given, unless you are creating a replica of something.

 

Of course, Becker Rudders would be even better, but you've got to be sensible!

 

I recall the day many years ago, with the Chief Engineer trying to work out what was wrong with our steering as arrival had shown something amiss.

Calls up to the Bridge- "Stop, stop, stop"!!

The flap wasn't working as it should, and with nowhere to release, this was causing hydraulic pressure to build up far too much!!