Canopus and Sculptor

[Guest]

Well from the pictures, if the original blade was 24", then the draught under the uxter seems more than 2' 6".

 

You're right Alan. Apparently there's 23mm ish to the skeg plus 100mm to the uxter plate, so 783mm total distance from uxter to upper skeg face, so 800mm overall ish top to bottom, that's 31.5" old money = 2'7.5" static draft, so it's safe to say around 3ft when underway.

 

The prop while I remember is 26" dia, 24.5" pitch - BUT - it has a 110A 24V alternator fitted that is always online. At 3kW there's a 4hp+ loss to consider for the prop calc too, so the usable engine power would be say 30hp ish @ 1200rpm.

 

I did question the tip clearances for the 26" but Clements were perfectly correct with their installation, all minimums had been met, if not exceeded, so fair enough.

 

I recognise many of the handling characteristics kindly mentioned by posters above, so it's seems my initial expectations are at fault too.

 

Next time she's out of the water I'll do a full measure up and see what we've got. If over the next few years I can't improve the handling then I'll gracefully resign and take up crochet. I still have the possibility of a high lift rudder section up my sleeve and that would certainly improve the glide performance. I'll have a full measure up when she's next out of the water, I'm particularly interested in the prop to rudder distance.

 

The rudder's balance seems reasonable, it's just that I want it do do something more in return for my arms aching.

[IanM]

The fat line sounds like the best idea to start with, and could work out to save you a lot of money too, unless these experienced hands will encounter the same problems as you have.

 

Don't do anything that's not really necessary, but if you decide (one day) to cut this strenghtening bar, you could add a compensation plate on the rudder, which will make the steering a lot lighter.

 

Peter.

 

What he said ^^^^^

 

OP, a lot of posts you make on the forum have a lot to do with theory. I suggest that the anode on the swim which you have an issue with makes bugger all difference in the real world to how the boat handles and would not be noticeable if it was there or not.

 

As we're all posting pictures of swims it seems, have another

 

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

[matty40s]

Well from the pictures, if the original blade was 24", then the draught under the uxter seems more than 2' 6".

The draught is almost certainly more than that. Canopus was sitting on the sleepers at the back end with about 3" of water removed from the dock, suggesting 2'9" or more. This was after belongings removed so no additional weight.

 

You are right Alan,,Dave Harris doesn't do spooning , completely flat under there.

 

I've also edited the Prop information in my first post, prop manufacturer is clements nit Crowther and it is clements make the axiom.

Edited December 26, 2016 by matty40s

[Derek R.]

The calculations for prop dia/pitch against engine power/rpm and gearbox reduction need also to include a "fiddle factor" for slip (which may be different from one manufacturer to another, and for the destined waterways and use thereon) - also hull length as well as displacement. Even then, and with particular note for canal use, any theoretical top speed will be greatly affected by the width, depth, and cross section of the canal in relationship to the hull cross section, which will determine maximum speed on narrow shallow canals (including much of the G.U.).

 

YARMOUTH was a reconstruction of a motor stern on a 1914 Braithwate & Kirk horse boat, and with an 18' long vertical swim (no double curvature). There could have been more space for the prop as can be seen in this image, but we still managed to get a 24" x 27" equipoise 3 bladed prop in there. The engine was a Petter PD2M (18hp @ 1500rpm) driving through a Parsons F box with 3:1 reduction. On deep water (N.Easter waterways and Trent) boats of a similar length with twice the horsepower could keep up - but not pass us. Also note the bracing of the inverted 'U' sectioned skeg.

 

 

YARMOUTH was 62' in length, steered to perfection so much that my wife would happily take the tiller anywhere. She would stop in one and a half times her own length, and like TYCHO, would steer out of gear whilst forward motion remained. But drag the bottom and another common story can be told. However, with her in a lock, she could be manoeuvred away from a wall and from behind a gate using stern gear only. Bow thrusters not required (though they may well help against wind in some situations). Under way she would pull down to three foot, and raise barely a ripple.

 

 

PS Louise never did steer TYCHO - too heavy, and apt to climb the banks without full attention!

 

Edited December 26, 2016 by Derek R.

[Dalslandia]

Dpaws,

If your arm is feeling like a raw pork loin, at the end of the day, the rudder forces is to high, steering forces or just out of trim.

when you take the vertical bar out, you can lengthen the balance area of the rudder to 20% total (25% of the rear portion)

can also make a fixed trim tab so it goes straight with out a force one way or the other.

[Laurence Hogg]

 

 

"Whilst the vertical strut is a poor design choice in our opinion, it does seem that what I've experienced so far is unique to my set-up alone and not commonplace across all strutted designs."

 

Virtually all early FMC steamers had a strut aft the prop except it also housed a rear bearing.

Edited December 26, 2016 by Laurence Hogg

[alan_fincher]

PS Louise never did steer TYCHO - too heavy, and apt to climb the banks without full attention!

 

 

It's a shortened Middle Northwich thing.....

 

Although "Sickle" is otherwise a joy, I can't let go of the tiller long enough to get my arm down one sleeve of a coat, without suffering a magnetic attraction to the nearest bank!

[mark99]

The south gu track I frequent mostly around my mooring makes my boat feel like a rubbish steerer. However if I go the north track from mooring I feel like a steering hero. Purely one direction is a shallow bowl of a cross section the north has got better depth and better underwater profile. Night and day is the difference.

[FadeToScarlet]

Dpaws,

If your arm is feeling like a raw pork loin, at the end of the day, the rudder forces is to high, steering forces or just out of trim.

when you take the vertical bar out, you can lengthen the balance area of the rudder to 20% total (25% of the rear portion)

can also make a fixed trim tab so it goes straight with out a force one way or the other.

Even with a balanced rudder, if you're having to fight a 3' draught boat which wants to be in the channel, because you haven't got the experience to steer it correctly, your arms will get very tired indeed.

 

So much so that I steer mostly with the small of my back- still getting to grips with a deep boat after a few years.

[Guest]

The south gu track I frequent mostly around my mooring makes my boat feel like a rubbish steerer. However if I go the north track from mooring I feel like a steering hero. Purely one direction is a shallow bowl of a cross section the north has got better depth and better underwater profile. Night and day is the difference.

 

That's really useful feedback, thank you - that may well explain why the steering feedback seemed so illogical, reasonable for a short while and then a nightmare for the next stretch etc. It was this unpredictability that rattled my confidence. Once I've spent more time cruising regular stretches I'll get a better understanding. Meanwhile I've actually got a little depth finder (as part of my fishing equipment); I'm now extremely curious to know what my actual under keel clearance is at any one time.

 

Even with a balanced rudder, if you're having to fight a 3' draught boat which wants to be in the channel, because you haven't got the experience to steer it correctly, your arms will get very tired indeed.

 

So much so that I steer mostly with the small of my back- still getting to grips with a deep boat after a few years.

 

Ahh, I discovered the "small of the back" technique, around Weedon that seems to work very well indeed, very comfortable. Further north on the GU, and particularly after turning north at Braunston it all went pear shaped very quickly.

 

With hindsight and in light of all the helpful feedback you guys have provided I'd obviously entered a shallower stretch of the cut that's narrower too - so far more critical for staying in the "channel". Maybe I didn't do so badly after all but yes, I can see that it's going to be a slow and patient process.

 

There's clearly a number of things that I can do to improve the handling of the boat, and they'll likely be undertaken over time. Once I've optimised the back end then the rest is simply a consequence of my inexperience and time spent at the tiller will resolve the rest.

 

However optimised the back end ends up I still can't avoid the physics of the canal and the forces on the hull. I'm confident that the closer that Canopus becomes to Sculptor under the water, the better she'll behave.

 

The skeg is overlong on Canopus compared with Sculptor (and other real working boats), no doubt that's led to the vertical support as the skeg doesn't have the room to achieve the vertical section it needs to achieve the required stiffness. Brinklows have kindly send me a dimensioned drawing of a typical working boat skeg and it's noticeably shorter and the whole assembly is far more compact.

 

The distance between the prop and the rudder on a working boat is much shorter that on Canopus, this again will increase the effectiveness of the rudder. Whilst I can't move the rudder I can extent the deadwood aft a little and the prop further aft a little more.

 

There are many examples online, but the guide I've just googled suggests minimums 27% dia from hull to prop and 10% from prop to rudder. (at 35% of propeller diameter). A 3:1 ratio ish, it's easier. Canopus though is vastly different, from the best photos that I have maybe a 1:3 ratio?

 

http://www.fao.org/docrep/x0487e/x0487e04.htm- note the comments

 

In general:

• Tip clearances should be as small as possible within guidelines, in order to accommodate the largest possible propeller.

• The distance from the propeller to the rudder should be kept small to maintain steering control.

• The distance from the deadwood to the propeller should be large.

It specifically refers to steering control - whilst this is only theory, one can look at the photo of the Canopus stern and appreciate the potential for steering control issues.

 

The anode placement is clearly too close to the prop on Canopus; note that the sacrificial anodes are much further away on working boats. At present the boundary layer flow will become disturbed/chaotic and has insufficient time to re-attached prior to the prop intake.

 

The present 26" four blade masks the flow of water to the rudder when gliding. Whilst a larger prop will indeed give a greater efficiency that's only part of the big equation, and as with most things, if you optimise one aspect then other aspects are compromised. I'm happy to increase the steering performance at the cost of propulsive efficiency. Dave Harris fitted a 24" prop despite there being the physical space for a 26" with compliant minimum tip clearances.

 

Of course all of the above in combination may only give me a nominal improvement; the channel's dominance over my hull will still remain. I'll see if I can reduce the overall draft by an inch or two as well, that will certainly help, maybe more than all of the above! We'll see....

Edited December 27, 2016 by dpaws

[Athy]

One thing has just occurred to me, and my apologies if it's been mentioned already: did you not test-drive Canopus before buying her? If so, did you not notice that her steering was problematical? If not, why not?

[junior]

Sounds to me like you are spectacularly trying to over complicate things.

 

My advise would be to get someone who is unused to steering a deep draughted boat (preferably historic) to come and have a steer for a little while. You shouldn't have to do too much persuading as it looks like you've got a nice boat there. Listen to their feedback and they might just tell you that it feels completely normal to them. This could save you a lot of time and money.

 

It sounds like Alan Fincher is not a million miles from you, perhaps he could be the man.

[roland elsdon]

I think you are missing the point. You are comparing apples and pears.

Canopus a welded modern replica with a full length top and , with a working boat designed to carry loads and tow a butty at speed on a deep canal.

Loaded boats are down by the head, modern boats are down by the stern..

The builder of Canopus is a genuine expert on building superb boats with enviable experience and has done so here so I doubt if his original speck would be far out. But you can' simply apply the principles of one to the other.

Having gone from an unconverted full length town to a short cabined 57 foot town (with the correct front and back,) and the same engine and box I assure you they have completely different characteristics.

[Derek R.]

 

It's a shortened Middle Northwich thing.....

 

Although "Sickle" is otherwise a joy, I can't let go of the tiller long enough to get my arm down one sleeve of a coat, without suffering a magnetic attraction to the nearest bank!

 

Yes, so much of the 'Dog' has been removed that the 'tail' takes control!

[Alan de Enfield]

I think that "Mr Paws" may slowly becoming around to accepting that the 'environment' plays a much bigger part in the handling and performance of a flat bottomed boat (skip) on a muddy ditch than all the computer programmes and 'theories' surrounding dimensions and curves which dictate down to the last micron.

[alan_fincher]

One thing I had already noted was the difference between davidg's "in primer" photo, and the one in the RBS sales brochure.





To me, the boat looks far more ballasted at the front in the form it was offered for sale, than it was when the first picture was taken, (not surprising, I guess, as probably not fully fitted out then).

 

However, I would suggest that many of the modern boats that are to some extent working boat copies, sit in the water more like the first photo than the second - i.e. significantly "nose end high".

 

Of course, in general getting it more level is no bad thing, but it does then mean the resulting boat will be at a significant draught throughout its entire length, and will obviously be both a lot heavier, and generally far more affected by getting out of channel.

 

Our converted working boat, whilst still very "nose high" sits massively lower in the water at the front than the converted equivalent. I had not fully appreciated what a huge difference this would make. Here our "Town class" boat lies on the outside of two unconverted "Towns". I have also spent a couple of days steering "Chertsey", moored against the towpath in that picture. Both have engines and gearboxes with similar powers and reduction ratios. There is absolutely no comparison between the two, and if I try using techniques I would easily have got away with on "Chertsey", I would be, (and on occasions have been!), in severe trouble with "Flamingo"

 

[bargemast]

Sounds to me like you are spectacularly trying to over complicate things.

 

My advise would be to get someone who is unused to steering a deep draughted boat (preferably historic) to come and have a steer for a little while. You shouldn't have to do too much persuading as it looks like you've got a nice boat there. Listen to their feedback and they might just tell you that it feels completely normal to them. This could save you a lot of time and money.

 

It sounds like Alan Fincher is not a million miles from you, perhaps he could be the man.

 

I suppose that this was a slip of the finger, and if it was, that is what dpaws said already in his post #50, he was going to invite experienced steerers in april to find out if it's just him, or the boat.

 

Peter.

Edited December 27, 2016 by bargemast

[BEngo]

In addition to the good advice on here could I also recommend that dpaws obtains and reads carefully a copy of "The Boaters Guide to Boating" by Chris Deuchar. I should think the NbOC bookshop will have it. It contains much practical advice born of long experience with deep heavy boats.

 

It is an easy read and will provide pointers to what is going on in and around the boat as well as hints on how to make it behave the way you want.

 

N

Edited December 27, 2016 by BEngo

[matty40s]

Canopus needs the engine winding up faster than the previous owner may have shown you how. This will give you a bit of oomph to help you with steerage.

It was incredibly frustrating trying to get him to maneover around the dock as he wanted to tick over in and out, achieving nothing as the bottom was on the silt.

Sometimes you have to give it some welly.

Canopus can and will work for you if you ignore normal modern hire type boat skills.

 

I brought a deep slab sided wide boat up from Ivinghoe last week, sometimes it went OK, sometimes (below Slapton, above Cosgrove ) it wouldn't move, woffled around the canal like a beached whale. The pounds were shallow and the channel not wide enough for the beast.

[mark99]

Re the widebeam. Did you display the special widebeam licence concession that allows you to leave every lock with both gates open for other mugs to close them? Very popular on the Southetn GU.

Edited December 27, 2016 by mark99

[matty40s]

Unfortunately, the CRT isduing offices were shut for Christmas from November to March so I shut every gate except 3rd from top at Stoke Bruerne........they never stay shut anyway

 

I find it far easier closing gates with a widebeam than a narrowboat, especially when windy.

Edited December 27, 2016 by matty40s

[wrigglefingers]

Canopus needs the engine winding up faster than the previous owner may have shown you how. This will give you a bit of oomph to help you with steerage.

 

.....

Sometimes you have to give it some welly.

 

.....

Canopus can and will work for you if you ignore normal modern hire type boat skills.

 

Exactly this. It took me ages to work just how much welly Cobbett needed to get her working for me. It's a completely different skill set and I was utterly nonplussed at first. You don't need to be in the least bit subtle with the power. I was generally too timid with Cobbett.

 

Partly, that was because I had the wrong engine in her, I think, in hindsight. I'd been talked out of having a Gardner 3LW on the grounds that it would be massively over-specified and I didn't have the skills to maintain it. The secondhand Beta JD3 was a disaster although the new short engine that replaced it was fine once Richard did some modifications to her. Nonetheless, it revved far higher than a Gardner would, and so I was extremely timid around over-revving her.

 

I did get far more confident with her over time though and found when I went back to helming a modern narrowboat that it slipped all over the place and was far more twitchy. If I could get Cobbett into a deep channel, she'd helm herself and not deviate; in shallow water, much less easy. She always swam well, though, in chug-a-long mode she barely disturbed the water.

Edited December 27, 2016 by wrigglefingers

[blackrose]

 

The builder is Dave Harris, one of the nicest and most honest guys you could ever wish to deal with and a highly skilled and experienced fabricator of sheet metal.

 

He is the first to acknowledge (and one of the very few that will) that he is not a naval architect and has never studied the principles of hydrodynamics.

 

Does one really need to have formally studied the subject to understand that a skeg support between the prop and rudder won't aid hydrodynamics and is undesirable? My bog standard Liverpool boat has a self-supporting skeg made from a piece of 10mm thick 4" x 2" U shaped channel.

 

Also what's all this business about seeking copyright before posting images? I've posted hundreds of web images on this site over the years and nobody's ever worried about copyright. Or has the new concern been raised exclusively to protect the delicate sensibilities of traditionalists and the owners of historic narrow boats?

Edited December 27, 2016 by blackrose

[WotEver]

Also what's all this business about seeking copyright before posting images? I've posted hundreds of web images on this site over the years and nobody's ever worried about copyright.

It's pathetic. An image that's already in the public domain was linked here. So what? Nobody was harmed, nobody lost any income, nobody's reputation was questioned.

 

The laws against copyright theft are generally to prevent someone either passing off another's work as their own, or to profit from someone else's work. To claim 'breach of copyright' for a public domain photo linked to on a forum is beyond petty childishness.

[Guest]

I think that "Mr Paws" may slowly becoming around to accepting that the 'environment' plays a much bigger part in the handling and performance of a flat bottomed boat (skip) on a muddy ditch than all the computer programmes and 'theories' surrounding dimensions and curves which dictate down to the last micron.

 

Thanks Alan, but actually you've missed the point. My own hull design was based on theory and optimised to minimise these effects, hence the reason for involving Dr Barrass as a consultant.

 

I've been very aware of the presence of these forces, but taken by surprise at the magnitude of their strength, which can be measured in terms of muscle burn and adrenalin!

 

I've watched a lot of historical boats being steered and only now I realised what an involved skill it is, you all make it look so ruddy easy! My sincere compliments one and all!

Edited December 27, 2016 by dpaws