Canopus and Sculptor

[ditchcrawler]

 

Perhaps you can come up with an example?

No I can't , that is basically what I said. until someone tries it on an boat that is ether old or of old design and Canopus seemed to be the closest we will get to that, we will never know the answer.

[mark99]

Did not the research centre of BW commision come up with a optimised carrying boat known on the cut as a "dustbin"?.

[Guest]

I went looking for some photos of Chertsey's undersides in an attempt to see shy she steers so well (but NOT in shallow water; no deep drafted boat will) and particularly why she steers so well in reverse, and I was surprised by how little balancing plate there is on the rudder.

 

That's not the original rudder, but it looks pretty similar to this one, which I am told was.

 

That's one of the best prop spacings I've seen - the prop's meant to be back there with it's nose close to the rudder's leading edge. You can fine tune the handling here quite easily by adding leading edge up to (I can't remember what Jan recommended) 15% of the rudder length.

 

Widgeon looks good too - lots of space between the deadwood and the prop

 

 

From book Walkers of Ricky:

 

 

Look how close the rudder cup is to that post, the vertical post is correct in this application but the rudder won't be balanced as there's no room for a leading edge. I am sure these boats are heavy on the tiller. Nice "s" curvatures though.

 

You can do one or the other, you can't mix the two layouts and retain an optimum configuration. Either vertical post and no leading edge for balance - or a balanced rudder but no vertical post (so a deeper skeg instead).

 

Rudder leading edges forward of the pivot and vertical posts are bad together; this is a fix for those less inclined to cut metal - a bulbous nose with a tight clearance to the trailing edge of the post:

 

Edited January 15, 2017 by dpaws

[Guest]

But has anyone ever tried a Shillings rudder on an old boat, if not we don't know if it would be better , worse or just the same.

 

Not that I'm aware of though I'm sure I'm not the first. The rudder will be much more effective at slower speeds - one day I'll find out if that's a good thing or a bad thing. It will act pretty much as a rear thruster at full deflections, should be able to spin on the spot with the bow thruster in combo... don't need to, obviously, but could... Maybe more useful on a gusty pound for example would be the ability to parallel traverse...

Edited January 15, 2017 by dpaws

[ditchcrawler]

 

Not that I'm aware of though I'm sure I'm not the first. The rudder will be much more effective at slower speeds - one day I'll find out if that's a good thing or a bad thing. It will act pretty much as a rear thruster at full deflections, should be able to spin on the spot with the bow thruster in combo... don't need to, obviously, but could...

I look forward to your results, I must admit I doubt you will get what you want but until you try we wont know.

[Guest]

I look forward to your results, I must admit I doubt you will get what you want but until you try we wont know.

 

No, as Sarah wrote earlier, you still can't change the fact you've got a deep fat hull going though a shallow narrow channel, but in open and deeper water I expect some positive differences will be apparent.

 

I expect a huge noticeable difference from the prop - 26" 68% DAR under-pitched four blade down to a 24" 46% DAR over-pitched 3 blade - almost half the metal in the water.

 

Reversing will start to work once the rudder/post gap has been resolved, and will then improve (slightly?) with the prop further aft in the same space.

 

The Schilling should allow me to increase the prop DAR without compromising directionality during a glide, slight loss of efficiency but better crash reverse performance.

 

That's the theory.... doesn't mean it'll work out that way...

Edited January 15, 2017 by dpaws

[alan_fincher]

I've been trying to sort out where some recent photos were, and found a few more of "Flamingo's" arrangements....








EDIT:

I conclude that "Flamingo's" (aka "Letchworth's") rudder looks very like the one that Ray posted a picture of for "Thaxted", (aka "Widgeon"). Both are "Large Northwich" Yarwoods boats, so either those rudders are something like original, or both have received a replacement somewhere similar, (e.g. under Willow Wren ownership?).

Edited January 15, 2017 by alan_fincher

[FadeToScarlet]

 

And for comparison, a "tree class" Severner rudder, will need to double check the plans about how original it is, but I think it is. Not much shape, no real external boss for the propshaft, a small bit of double curve on the swims but not much.

[Guest]

Flamingo is spaced well too - I'd expect true original designs that have come from issued drawings to all work relatively well, albeit differently from each other certainly.

 

It's the "reproductions" of original designs that seem to suffer as variations creep in, and their implications aren't necessarily well understood.

DSC_0996.JPGDSC_0995.JPG

And for comparison, a "tree class" Severner rudder, will need to double check the plans about how original it is, but I think it is. Not much shape, no real external boss for the propshaft, a small bit of double curve on the swims but not much.

 

That's a tight configuration, quite a small prop for the space - is that typical and thus maybe help with handling or is the diameter solely your choice based on your engine/gb combination?

[FadeToScarlet]

That's a tight configuration, quite a small prop for the space - is that typical and thus maybe help with handling or is the diameter solely your choice based on your engine/gb combination?

It's got a 19" blade at the moment, pretty small because the engine until I can afford to change it is a modern Lister-petter LPWS4.

 

Originally, with a 8/10hp Petter S Type semi diesel, revving to I think 400rpm flat out, it would I suppose have had something monstrous squeezed in.

[IanM]

 

 

EDIT:

 

I conclude that "Flamingo's" (aka "Letchworth's") rudder looks very like the one that Ray posted a picture of for "Thaxted", (aka "Widgeon"). Both are "Large Northwich" Yarwoods boats, so either those rudders are something like original, or both have received a replacement somewhere similar, (e.g. under Willow Wren ownership?).

For comparison, here's Nutfield's which with the riveted portion I would think is fairly original? But then again...

 

Nutfield - Braunston Dry Dock 16/10/2016 by Ian, on Flickr

[alan_fincher]

For comparison, here's Nutfield's which with the riveted portion I would think is fairly original? But then again...

 

Nutfield - Braunston Dry Dock 16/10/2016 by Ian, on Flickr

 

That does look perhaps more like what I might expect.

 

I'm always curious about those that have rivets through the raised top, as the only possible reason for these would be if the rudder were fabricated from two thinner bits of steel. I can't for the life of me see why you would do that - a single plate surely being easier, without the prospect of corrosion getting between 2 layers.

 

EDITED TO ADD:

 

Sickle apparently sports rivets at the top of its rudder, but (horror of horrors!), I think they may be fakes!

Edited January 16, 2017 by alan_fincher

[IanM]

Possibly the blade of the rudder was made out of one sheet and the top riveted on to strengthen it? Wish I'd taken a picture of the other side now to compare.

 

As for Sickle's, could it possibly be the original riveted top welded on to a new blade and therefore they are not fake but real rivets?

[ditchcrawler]

It would be great if you lot could all get together and try out Canopus after she has been reworked, say down the W&B and then out on the river Severn or Oxford and Thames. It could be a good day out for all.

[Guest]

Possibly the blade of the rudder was made out of one sheet and the top riveted on to strengthen it? Wish I'd taken a picture of the other side now to compare.

 

As for Sickle's, could it possibly be the original riveted top welded on to a new blade and therefore they are not fake but real rivets?

 

I'm sure someone said that if you can see both sides of the rivet then they must be real...

 

 

It would be great if you lot could all get together and try out Canopus after she has been reworked, say down the W&B and then out on the river Severn or Oxford and Thames. It could be a good day out for all.

 

That sounds a fine excuse for day out indeed! Italian grub obviously, homemade lasagne, fresh Tiramisu and moka macchiatos all round?

[alan_fincher]

It would be great if you lot could all get together and try out Canopus after she has been reworked, say down the W&B and then out on the river Severn or Oxford and Thames. It could be a good day out for all.

 

My vote would still be try try Canupus before it is reworked!

 

(Just in case it doesn't actually need "reworking"!).

[cuthound]

My vote would still be try try Canupus before it is reworked!

 

(Just in case it doesn't actually need "reworking"!).

Exactly.

 

When is Matty supposed to be trying her out?

[IanM]

 

(Just in case it doesn't actually need "reworking"!).

 

But it does, an experienced and respected naval architect said so

 

 

 

 

 

 

 

 

 

Sorry....

[David Mack]

And a large Woolwich version on Fulbourne.

 

 

Not a great picture of the rudder blade. The top and bottom straps and the top section are original. The main part of the blade and the balance section have been replaced c 1987. The top is indeed two plates riveted together, and the edges have been forced apart a bit by corrosion between the plates.

 

 

 

 

[alan_fincher]

And a large Woolwich version on Fulbourne.

 

PICT0270.jpg

 

Not a great picture of the rudder blade. The top and bottom straps and the top section are original. The main part of the blade and the balance section have been replaced c 1987. The top is indeed two plates riveted together, and the edges have been forced apart a bit by corrosion between the plates.

 

Do you happen to know what diameter and pitch prop Fulbourne has, please David?

 

I've received conflicting information about what might be "normal" with a National or and RN, and a Brunton's box.

[ditchcrawler]

 

My vote would still be try try Canupus before it is reworked!

 

(Just in case it doesn't actually need "reworking"!).

Its a good idea to try first and you may all say no work is needed, but if you don't do the work you will never know if it makes a difference, ether better or worse.

 

But it does, an experienced and respected naval architect said so

 

 

 

 

 

 

 

 

 

Sorry....

Just like all the old boaters said horses were fine for Narrowboats until someone tried an engine.

[Tonka]

I think Dpaws is not going to be happy until Canopus is a Gondaler

[MtB]

I think Dpaws is not going to be happy until Canopus is a Gondaler

 

 

Not so sure about that. My view is that he would have found fault with any boat he purchased and like with Canopus, he would have the feeling the faults can be cleared up by improving the underwater design.

 

The fun lies in the development of the plans for some alterations in line with contemporary naval architecture thinking, the execution of those alterations and finally, the testing of the results of those alterations and seeing what a big improvement the application of the theory has had. Or not as the case may be.

[Chertsey]

But what he'll never be able to do is make the hull the same shape as a Woolwich or a Northwich. And for my money that's a big factor.

[Tonka]

Wrigglefingers said that Cobbet had a bar and handled ok. Our D Harris has the bar and handles ok but like Cobbet does not have fake rivets. Perhaps it is the fake rivet heads below the water line that is disturbing the flow of the water to the prop.