nb Beech

[gazza]

Tony is right insomuch as the desired profile can be achieved by using strips rather than sheet and a sensible thickness of material (6mm rather than the ridiculous 8mm that is the fashion) you can fairly easily get the steel to take any form you wish - particularly when using robust temporary framing to produce the desired profile.

Couple that with the judicious use of heat and a knowledge of how to approach the job almost anything can be achieved.

[Guest]

Couple that with the judicious use of heat and a knowledge of how to approach the job almost anything can be achieved.

 

That seems to be the juxtaposition - the guys who really know how to heat and work the metal seem to be the ones most adverse to the idea of CAD templates...

Edited January 10, 2016 by dpaws

[Stilllearning]

I know that a friend of mine went to Ellesmere years ago and spent hours measuring a motor, then had his boat made. It is a beauty, so it can be done. A builder like CTS at Norton Canes might do it.

[gazza]

 

That seems to be the juxtaposition - the guys who really know how to heat and work the metal seem to be the ones most adverse to the idea of CAD templates...

Only in a cottage industry!

 

If you could come up with a set of templates that assured accuracy and repeatability and I were in the business of building floating cottages you'd soon become a partner rather than a customer!

[MtB]

Sam Springer would have loved CAD templates.

 

The narrowboat kits he sold for you to stick together with a Halfords buzz welder were famous for the shapes not fitting!

 

Or maybe that was down to the dodgy welding...

[Derek R.]

 

(snipped) . . . but I see many asking what is it that makes a boat swim well, and that answer lies within the numbers. It interests me, but probably no one else!

 

It's a subject that was close my heart, as was the working out of engine hp, rpm, reduction ratios, prop shape, pitch and diameter for a given displacement relevant to hull length x breadth. Quite a few fiddle factors were involved to with slip, canal depth and a bit more - like entrenched beliefs!

 

A bulbous bow is efficient, but for a narrow boat, the back end swim is more directly important. YARMOUTH got rebuilt with an eighteen foot swim and went very well with little or no wash. Stopped in just over her own length (62'), though would have been better with rounded chines instead of square.

[mark99]

Rather than re-invent the wheel / commission a very expensive one off take a look at boats built via the following boat builders. Some of them have already measured the Josher compound curves carefully and have them filed (and scaled down a bit as deep drafts not necessarily required nowdays).

 

1) Simon Wain

2) Steve Priest

3) Roger Fuller

4) Norton Canes G Edgeson

5) Dave Harris

 

If you don't like their steel hulls then, goodness gracious.

 

Ours is a 2007 R Fuller. (Its looks better without cratch cover).

 

Edited January 10, 2016 by mark99

[Guest]

Wow! What a wonderful day! I have acquired permission from her owner to arrange a measuring party...

 

I'm not sure which will arrive first, the warmer weather most suitable for wriggling into tiny spaces or the technology that recreates 3D solid models from regular smartphone camera pictures, we'll see!

 

Nice to hear that I'm not alone Derek - I've always had the need to know why, it drove my mother crazy! Not so sure about the rounded chines though - I had the same instinct until I read about the issues with the "middle" sized working boats and their instability. They may well have been marginally better on the flowing waters, for which they were designed, but conversely I have yet to find handling complaints regarding the Town and Royalty Class boats on rivers with their square knuckles.

 

I recall that David Harris concluded that tapered aft swims can only be appreciated every two years during blacking, cost more to produce but have minimal influence on the handling. Due to my internal space requirements I'm more inclined to deviate from the norm and optimise a "slipper stern" type profile instead, rather like the beautiful Bushell's Progress whose fascinating reconstruction is covered elsewhere on the site.

[Guest]

Thanks for the advice Mark - you're not the first, and you won't be the last... I think you've done well to list the avenues to a very expensive boat - and yours is very elegant, my compliments. She's a bit light on the rivets though... I doubt there'd be enough to hold it all together if they were real. I've attached a photo of a nude David Harris masterpiece for comparison, albeit of a different model. I've never priced it up, but at £40ish an hour for false rivets that's a considerable part of the budget that I'd prefer to allocate elsewhere on the build. They all construct wonderful boats and I have the greatest respect for their craftmanship. David Harris is an absolute gent to boot.

 

It's a very personal thing but I don't care much for fake rivets, I'd rather either restore an original or spend my budget on the design process of a new build. I've never been one to follow the crowd, no offence intended. Does it make sense that I don't want a "Josher" bow, because I don't want the Josher hull that fits that Josher bow, because it doesn't work for me.

 

I want a fine bow and a fine stern, hydrodynamically balanced and suited to my needs - I've no intention to carry cargo so why would I commission a cargo barge? I don't want real rivets because welding is a technically superior method of joining two metal panels together, and I can afford a better corrosion protection to a welded seam than I can to a riveted joint.

 

That doesn't mean I won't stare longingly at classic hulls, but in this period and for this boat that's not the priority.

Harris Northwich.tiff

Edited January 11, 2016 by dpaws

[MtB]

 

I've never been one to follow the crowd, no offence intended. Does it make sense that I don't want a "Josher" bow, because I don't want the Josher hull that fits that Josher bow, because it doesn't work for me.

 

But Sir, SIR, Beech IS a Josher!

[alan_fincher]

Rather than re-invent the wheel / commission a very expensive one off take a look at boats built via the following boat builders. Some of them have already measured the Josher compound curves carefully and have them filed (and scaled down a bit as deep drafts not necessarily required nowdays).

 

1) Simon Wain

2) Steve Priest

3) Roger Fuller

4) Norton Canes G Edgeson

5) Dave Harris

I hope I'm not giving wrong information, but I believe Graham Edgson has now retired.

 

Most (but not all!) of Simon and Steve's output tends to be "Grand Union" type "remakes", (as they tend to call them, I think).

[Guest]

Mike - Yes, I accept, but you missed the point - indifferent if she was a "Josher" (she was rebuilt / modified) or not, the point is that bow on Beech is fine and the shearline is elegant, more so than our friend's expensive Fuller boat.

 

That's very different that specifying that I want a Josher bow to a builder - which I don't want to do - because people don't understand the difference between a fine bow (which was the whole point of the Josher) ,and a pinched nose distortion of metal plates which is often the result of such requests due to ignorance.

 

For sure the A list of builders will yield more reliable fine bow results, but typically they're not interested in following an alternative stern profile - Richard hit that nail on the head earlier!

Edited January 11, 2016 by dpaws

[Laurence Hogg]

Wow! What a wonderful day! I have acquired permission from her owner to arrange a measuring party...

 

I'm not sure which will arrive first, the warmer weather most suitable for wriggling into tiny spaces or the technology that recreates 3D solid models from regular smartphone camera pictures, we'll see!

 

Nice to hear that I'm not alone Derek - I've always had the need to know why, it drove my mother crazy! Not so sure about the rounded chines though - I had the same instinct until I read about the issues with the "middle" sized working boats and their instability. They may well have been marginally better on the flowing waters, for which they were designed, but conversely I have yet to find handling complaints regarding the Town and Royalty Class boats on rivers with their square knuckles.

 

I recall that David Harris concluded that tapered aft swims can only be appreciated every two years during blacking, cost more to produce but have minimal influence on the handling. Due to my internal space requirements I'm more inclined to deviate from the norm and optimise a "slipper stern" type profile instead, rather like the beautiful Bushell's Progress whose fascinating reconstruction is covered elsewhere on the site.

"Royalty" class boats have rounded chines (what you call knuckles) for estuarial and river work, they effectively produced the "middle" GU boats.

And I would not refer to Bushell's "Progress" as having a slipper stern, its a normal counter stern with a two plane run in. The only motors which had a different stern were the Chas Nelson steamers and some tunnel tugs, ie "Sharpness".

Edited January 10, 2016 by Laurence Hogg

[Guest]

Thanks Laurence, I'm easily confused with the historical variations.

 

I used the wrong phrase with the slipper stern, but I'm sure we can agree that the curves on Progress are simply beautiful - and what looks beautiful to the eye is often excellent for the hydrodynamics... My aft swim will taper more from the base plate up to the counter stern than from the sides inwards to the sternpost - hard to describe here but performs very well under flow simulations.

Edited January 10, 2016 by dpaws

[alan_fincher]

Nice to hear that I'm not alone Derek - I've always had the need to know why, it drove my mother crazy! Not so sure about the rounded chines though - I had the same instinct until I read about the issues with the "middle" sized working boats and their instability. They may well have been marginally better on the flowing waters, for which they were designed, but conversely I have yet to find handling complaints regarding the Town and Royalty Class boats on rivers with their square knuckles. .

 

I think you are under a few misapprehensions.

 

"Royalty" boats have round chines, probably to almost identical radius to those on a "middle" boat. I can't see why they should roll significantly less, and I would have thought it could easily actually be more, because of the extra high up mass added by sides that are considerably deeper.

 

EDIT.

 

Beaten to it by Laurence, it seems!

Edited January 10, 2016 by alan_fincher

[Guest]

Ahh, have I confused again? They rolled more, not less, and apparently were unpopular with the crews - or so I've read on this forum. More roll when turning too, (less grip on the water I suppose, if that makes sense in simplistic terms) - more roll means more weight transfer about the roll centre.

Edited January 11, 2016 by dpaws

[FadeToScarlet]

Thanks Laurence, I'm easily confused with the historical variations.

 

I used the wrong phrase with the slipper stern, but I'm sure we can agree that the curves on Progress are simply beautiful - and what looks beautiful to the eye is often excellent for the hydrodynamics... My aft swim will taper more from the base plate up to the counter stern than from the sides inwards to the sternpost - hard to describe here but performs very well under flow simulations.

Looks like it'll be drawing a lot of water up from under the baseplate, to my untutored eye- and so might draw a lot of rubbish off the bottom into the blade?

[mark99]

PJ Barber makes/made fine overall balanced looking boats too.

 

Note there is more than one type (maker) <in fact several> of Josher too. (Laurence will testify )

 

Re rivets - yeah well they were already there (2nd hand) and were not a deal breaker to me.

 

Re hydrodynamics - would not get too hung up over that optimisation - after all most canal boats are pushing through shallow ditches full of obstructions - no fancy hydrodynamics are going to overcome that fact.

Edited January 11, 2016 by mark99

[mark99]

Steve Priest hull

 

 

 

 

Dave Harris

 

 

I always liked Jasons Bow too.

 

[Guest]

It's interesting to see them all side by side, all beautiful in their own way - but Jason does seem to have an elegance that the others don't quite achieve - maybe it's her aged look that adds character, maybe it's because the rubbing strakes are less pronounced to the eye, not sure... it could just be the white band that draws the eye towards the shearline..

[alan_fincher]

Ahh, have I confused again? They rolled more, not less, and apparently were unpopular with the crews - or so I've read on this forum. More roll when turning too, (less grip on the water I suppose, if that makes sense in simplistic terms) - more roll means more weight transfer about the roll centre.

 

Yes, a "Middle" boat with rounded chines has more "roll" than a "Large" or "Small" one that didn't have them - that is undisputed.

 

However the bit Lawrence and I was challenging is why you grouped the ("very large") Royalty boats with the "Large" ("Town") boats, as the Royaltieshave round chines near identical to the "Middles".

 

The "unpopular with boatmen" bit is I would say not a universally proven view. Tam Murrell of this forum who operated "Middle" boat Leonids in trade has commented very favourably about it in past posts, (and Tam should know!).

 

Part of the "Middle" boats reputation, I think stems from the fact that 4 of the motor boats (half of alll those built), were converted to ice breakers when only 6 or 7 years old. That conversion took away 31' 6" of the hold, resulting in boats of just 40 feet, of which a very large part is front (or particulaly) rear swim. If you look at pictures of one of these boats docked, the impression is of the shape of a whale, rather than a modern box build narrow boat. It is hardly surprising that they roll a bit, (though keeping ballast low down helps hugely).

 

However I think with the 31' 6" still present they are fairly stable. I stepped repeatedly on and off the full length "middle" boat now known as "Severn Dolphin", (which may or may not have originally been Taygeta), when moored alongside it last Autumn, and I did not get the impression of a boat significantly more "tender" than a "Small" or "Large" one. Having done a trip on a "Royalty", despite the round chines, I was not aware of a lot of "roll".

 

The round chines help enormously if you manage to get out of channel and into the shaller bits of cut at the side. Our "middle" boat "Sickle" will often slip back off and help the steerer out of their error - our "large" boat "Flamingo" is far more likely to just stem up.

[Tony Dunkley]

Ahh, have I confused again? They rolled more, not less, and apparently were unpopular with the crews - or so I've read on this forum. More roll when turning too, (less grip on the water I suppose, if that makes sense in simplistic terms) - more roll means more weight transfer about the roll centre.

 

 

There really isn't anything called a "roll centre" that is of any use in determining stability, and weight doesn't get 'transferred' round anything.

Stability, in the context of a vessel's resistance to rolling and it's ability to return to the upright from being heeled over is dependent on the position of the C of G of the whole structure in relationship to the transverse metacentre, which is in turn, dependent on the lateral displacement of the (transverse) Centre of Buoyancy for any given angle of heel.

 

 

dpaws, on 10 Dec 2015 - 4:35 PM, said:

I'm surprised the roll centre was so high, . . . . .

When you say "roll centre", I'm assuming that you mean the point about which the boat rotates, or rolls, transversely. For practical purposes, this point is at the intersection of the vertical centreline and the waterline, irrespective of whether the vessel is upright or listing, and so it's height can only vary if measured in relation to the vessel's keel, after a change in the draught.

Transverse stability is determined solely by the position of a vessel's [transverse] Centre of Gravity (G) relative to the position of the transverse metacentre.

The transverse metacentre (M) is the point where the vertical centreline is intersected by a vertical line through the [transverse] Centre of Buoyancy at small angles of heel. The separation distance of G and M is the metacentric height (GM), and is the basic measure of a vessel's stability. In simple terms, if G rises above M, the vessel capsizes, but if M is above G, all is well, with stability increasing as the value of GM increases, and vice versa.

[Derek R.]

You probably won't be going for rounded chines, but I can say that TYCHO rolled quite a bit more - but with the caveat that it was the shortened (to 40') version. SEAGULL, the Cowburn & Cowper Northwich built at 70' with rounded chines, didn't seem to roll any more than a full length Josher or GUCC boat. Ask David Lowe (SWALLOW), he runs a 70' Cowburn & Cowper. The squared chine will act like a damper in the roll mode, and quite why those rounded chine craft are faster for a given length and engine HP I don't know, but SEAGULL was one very fast boat (given depth of water) with just the old Hercules at 18hp (IIRC).

 

You can get a bit nearer the bank as well!

 

PS Tony has it precisely.

 

PPS Just in case the "speed" factor seems to be predominant in my posts (length ratio to breadth will limit that), it's really more efficiency through the water - and shallow water at that. I don't think a square chined canoe would be able to keep up with a round chined canoe given the same propulsive effort, and less effort for a given speed means saved fuel.

 

Dave Harris is correct when he states you really don't appreciate a fine stern swim until it's docked - because afloat you cannot see it - but you can certainly feel, and see the minimal wash from a long swim aft. Did it handle well? You betcha! My wife would steer YARMOUTH and manoeuvre anywhere, but would not take the tiller on TYCHO, and never did.

Edited January 11, 2016 by Derek R.

[Guest]

However the bit Lawrence and I was challenging is why you grouped the ("very large") Royalty boats with the "Large" ("Town") boats, as the Royaltieshave round chines near identical to the "Middles".

 

You're both very kind for correcting me, I hadn't made the connection between the two different classes sharing a similar rounded profile. Interesting to hear your positive comments too.

 

I'm mindful of the need to taper the base plate somehow having witnessed Mary struggle in the margins with nb Swan towards Ellesmere Port last Easter.

 

I noted somewhere that Peter Nicholls includes a 45° section at the base plate knuckle/chine and his craft are usually complimented for their handling. A flat centre section with shallow v'eed sides could work too, and would suit my stern profile - the flat section to give her some stability when grounded in drydock prior to chocking.

[Guest]

Looks like it'll be drawing a lot of water up from under the baseplate, to my untutored eye- and so might draw a lot of rubbish off the bottom into the blade?

 

You are correct indeed Sir... though the original boats changed from slab sided in wood to a bottom favoured profile with their shaped swims in steel. Conversely of course it won't draw in so much from the surface - is it a rock and a hard place thing?

 

Stern 1 is probably as fine an aft profile as I can achieve with the engine in it's present position in the hull. Stern 2 is more of a refined slipper stern type ( as in XR&D slipper, not Thames) with a flared central "pod" to accommodate the engine bulge.

STERN_1.tiff

STERN_2.tiff

Edited January 11, 2016 by dpaws