JohnO Posted December 30, 2016 Report Share Posted December 30, 2016 (edited) ah, erm... yes maybe not sure about these force thingies, just know when people mention channel sides and the parallel slab hull there are a only few things you need to know, that effect being one. We have ice now, come back and break some, see how your steerage performs then. Not sure if bowthrusters like it though. edit: IanM & IanD sounds good to me. Edited December 30, 2016 by JohnO Link to comment Share on other sites More sharing options...
David Mack Posted December 30, 2016 Report Share Posted December 30, 2016 (edited) Lots of work -- both theoretical and backed up by experiments -- has been done over the last couple of hundred years on how to optimise hull design, even for unusual cases like narrowboats in a relatively shallow canal, though most of the effort has been deep sea ships for obvious reasons And while there is an obvious commercial motive for seagoing freight operators to optimise their hull designs, there is virtually none for narrowboat builders.Most narrowboats are built by steel fabricators with little or no interest in the finer points of hydrodynamics, and are selling their boats to an uninformed and largely uninterested buying public. So shells are designed for ease of fabrication, minimum cost, provision of usable internal space and general good looks, which for the middle market means looking like every other clonecraft, and at the top end means looking like a working boat. The boatbuilder has no incentive to refine the underwater hull shape for better performance. Edited December 30, 2016 by David Mack 1 Link to comment Share on other sites More sharing options...
Guest Posted December 30, 2016 Report Share Posted December 30, 2016 (edited) The boatbuilder has no incentive to refine the underwater hull shape for better performance. I absolutely agree. Engine horse power is cheap, 43 being the norm, so who cares. When the tide turns for diesel-electric I think the mentality will change as batteries cost a load and take up valuable space. My boat goes further than your boat will be the subject of much debate in the future, I'm sure. We just need recharging points at the 48hrs mooring points and then the scene will take off IMHO. Technology's making the prospect of complex shaped hulls much easier with precision laser cut kits, only a couple of clicks once you've got a 3D model. Put them together in Eastern Europe and ship them over in standard containers to weld shut here and add whatever fancy superstructure the customer asks for. When you leave the hull structure to "fabricators" rather than boat builders then a whole new world of equipment opens up. My potential hull fabricators have a gantry 3D scanner with mm precision and 20mm sheet rollers. Even their "apprentice" welders are multi-coded; it's a different world to that on the cut. If you request their apprentices and forgo official engineering certification then you can find nuclear industry build quality at canal-side prices. The difference is being able to the slacken the build tolerances to mere whole millimetres!! Edited December 30, 2016 by dpaws Link to comment Share on other sites More sharing options...
IanD Posted December 30, 2016 Report Share Posted December 30, 2016 (edited) I absolutely agree. Engine horse power is cheap, 43 being the norm, so who cares. When the tide turns for diesel-electric I think the mentality will change as batteries cost a load and take up valuable space. My boat goes further than your boat will be the subject of much debate in the future, I'm sure. We just need recharging points at the 48hrs mooring points and then the scene will take off IMHO. Technology's making the prospect of complex shaped hulls much easier with precision laser cut kits, only a couple of clicks once you've got a 3D model. Put them together in Eastern Europe and ship them over in standard containers to weld shut here and add whatever fancy superstructure the customer asks for. When you leave the hull structure to "fabricators" rather than boat builders then a whole new world of equipment opens up. My potential hull fabricators have a gantry 3D scanner with mm precision and 20mm sheet rollers. Even their "apprentice" welders are multi-coded; it's a different world to that on the cut. If you request their apprentices and forgo official engineering certification then you can find nuclear industry build quality at canal-side prices. The difference is being able to the slacken the build tolerances to mere whole millimetres!! The extreme case of having a real *need* to minimise required power was Keith Jones's steam-powered "Firefly", which IIRC had about 3SHP at 200rpm flat-out. Also had a very well-shaped hull with long swims, a relatively big prop (26"?) and deep draft (32"?). On most canals it just glided along with hardly a ripple, but you couldn't keep up easily walking. On shallow canals it slowed down quite a lot, but didn't have enough power to make the stern squat so still wafted along, just more slowly. For stopping however you'd be quicker throwing out an old boot on a rope... It meant you had to think more like a supertanker captain, planning both acceleration and stopping much more in advance than with a nice big 43HP diesel, but there was something satisfying about timing it just right and going astern before the bows had even entered a lock so that you just came to a silent halt before touching the gate :-) For cases like this (power-efficient battery-electric) it would be interesting to really put modern CFD and double-curved hull fabrication to the test and see just how low-drag such a hull could be made in a modern canal. My guess is that typical cruising power requirement could be kept down to something around 3kW/4HP which would give a pretty big range (several days) between recharges with a typical 48V/800AH traction battery bank. Edited December 30, 2016 by IanD 1 Link to comment Share on other sites More sharing options...
ditchcrawler Posted December 30, 2016 Report Share Posted December 30, 2016 Why not just make it lighter using wood or glass fibre and dump the steel, come in at 10 ton and not 20. Link to comment Share on other sites More sharing options...
Guest Posted December 30, 2016 Report Share Posted December 30, 2016 (edited) Why not just make it lighter using wood or glass fibre and dump the steel, come in at 10 ton and not 20. If you want the same draft then you'll need the same displacement - you could make it out of paper but you'd need to fill it with ballast just the same... and besides, you'd look like a Broad's bathtub... Edited December 30, 2016 by dpaws Link to comment Share on other sites More sharing options...
ditchcrawler Posted December 30, 2016 Report Share Posted December 30, 2016 If you want the same draft then you'll need the same displacement - you could make it out of paper but you'd need to fill it with ballast just the same... and besides, you'd look like a Broad's bathtub... But why have a 3 foot draft if you want maximum propulsion efficiency Link to comment Share on other sites More sharing options...
MtB Posted December 30, 2016 Report Share Posted December 30, 2016 and besides, you'd look like a Broad's bathtub... Some of the early GRP hull broads boats are actually rather handsome boats. I'm thinking of some of those with the mahogany superstructures. There is a very sad and neglected one on the Moon Boat moorings at Honeystreet. Link to comment Share on other sites More sharing options...
Guest Posted December 30, 2016 Report Share Posted December 30, 2016 But why have a 3 foot draft if you want maximum propulsion efficiency Have a look at a Peter Nichols build, it depends on your aesthetic tastes. Springers too I suppose to be fair. We all need 6ft+ headroom interior, so if there's less underneath then there's more sticking out the top. But you're right of course. You've two choices - get sucked off course with a deeper hull or get blown off course with a higher superstructure Link to comment Share on other sites More sharing options...
MtB Posted December 30, 2016 Report Share Posted December 30, 2016 You've two choices - get sucked off course with a deeper hull or get blown off course with a higher superstructure Three actually. The third being buy a motor home... Which brings me onto a subject swerve. I keep noticing scruffy liveaboard motorhomes parked up (sometimes for months at a time) in CRT VM car parks. I think this is a new and generally unrecognised use of CRT facilities. I noticed one back in the summer using a CRT key to empty their cassette... Link to comment Share on other sites More sharing options...
GUMPY Posted December 30, 2016 Report Share Posted December 30, 2016 (edited) Three actually. The third being buy a motor home... Which brings me onto a subject swerve. I keep noticing scruffy liveaboard motorhomes parked up (sometimes for months at a time) in CRT VM car parks. I think this is a new and generally unrecognised abuse of CRT facilities. I noticed one back in the summer using a CRT key to empty their cassette... Let me fix that for you Edited December 30, 2016 by Loddon Link to comment Share on other sites More sharing options...
davidg Posted December 30, 2016 Report Share Posted December 30, 2016 (edited) "Rudder forces aren't consistent and change with speed. Typically the right arm aches a lot more than the left on an evening after cruising. At close to 90kg I'm not lightly built and it takes my full strength and full rudder deflection at times with very little effect." My antennae pricked up at this earlier and since nobody else has bitten I will: When I'm steering the tiller doesn't swing outside the slide runners much, and very rarely outside the handrails. Full rudder deflection? Never, it's a waste of time and effort. A group* of us were in The Folly last night & this thread came up several times with varying degrees of incredulity/head shaking/nodding sagely/choose your own reaction. At risk of causing offense, here's one summary, related to me by Ian Sly a long time ago: "So Ian, what makes your boat go so well?" "There's four things make a boat go well." "There's the right engine; the right blade; the right hull shape and then there's the most important thing of all..." (Leaning inwards to catch this pearl of wisdom) "Ooh, what's that Ian?" "The twat with his hand on the speedwheel" *collective boat owning/steering/building experience approaching the age of the universe Edited December 30, 2016 by davidg Link to comment Share on other sites More sharing options...
Guest Posted December 30, 2016 Report Share Posted December 30, 2016 Rudder forces aren't consistent and change with speed. Typically the right arm aches a lot more than the left on an evening after cruising. At close to 90kg I'm not lightly built and it takes my full strength and full rudder deflection at times with very little effect. Have you been moonlighting on Canopus? I genuinely double-taked to see if that was one of my old posts! Link to comment Share on other sites More sharing options...
MtB Posted December 30, 2016 Report Share Posted December 30, 2016 Let me fix that for you What did you fix??! Link to comment Share on other sites More sharing options...
GUMPY Posted December 30, 2016 Report Share Posted December 30, 2016 What did you fix??! Use to abuseOh never mind Link to comment Share on other sites More sharing options...
Guest Posted December 30, 2016 Report Share Posted December 30, 2016 One of the most beautiful aspects of 3D CAD sketching - you really can see what the water can "see" - and get a feel for the flow through the swim Link to comment Share on other sites More sharing options...
MtB Posted December 30, 2016 Report Share Posted December 30, 2016 Use to abuse Oh never mind Bugger, Thats what I meant to type! Link to comment Share on other sites More sharing options...
Dalslandia Posted December 30, 2016 Author Report Share Posted December 30, 2016 Snip20161230_31.png One of the most beautiful aspects of 3D CAD sketching - you really can see what the water can "see" - and get a feel for the flow through the swim what airfoil did you use on the propeller? and water temp? Link to comment Share on other sites More sharing options...
Guest Posted December 30, 2016 Report Share Posted December 30, 2016 (edited) what airfoil did you use on the propeller? and water temp? I'm sure it was one that you sent me! 60°F naturally, as it was an American that developed and published the Schilling section, full CFD analysis by XFOIL Edited December 30, 2016 by dpaws Link to comment Share on other sites More sharing options...
mark99 Posted December 31, 2016 Report Share Posted December 31, 2016 Just need Cart to dredge and construct the canal profile according to Schilling, drop in a few waterbath heaters to maintain 60f and the job is done. Link to comment Share on other sites More sharing options...
Guest Posted December 31, 2016 Report Share Posted December 31, 2016 (edited) Just need Cart to dredge and construct the canal profile according to Schilling, drop in a few waterbath heaters to maintain 60f and the job is done. I'll start preparing the risk assessment.... ...yip, it's risky; there's a chance it could actually work... Edited December 31, 2016 by dpaws Link to comment Share on other sites More sharing options...
Dalslandia Posted December 31, 2016 Author Report Share Posted December 31, 2016 Schilling is a rudder profile, comes in different refinements, it works, it works a lot better then a flat plate rudder does, a thick Schilling works better then a Thick NACA 00xx profile. Dalslandia have a Schilling of my own design, it was a WOW factor when first tested it. Dalslandia have a 400 mm diameter bow thruster, it works very well too. Non of the Schilling or bow thruster replace the other. they are there to be used. Link to comment Share on other sites More sharing options...
IanD Posted December 31, 2016 Report Share Posted December 31, 2016 Unlike some of the other (marine) hull refinements, there's absolutely no reason a Schilling rudder shouldn't have all the advantages over a flat plate one that numerous tests (and simulations) have shown, and which have been borne out by those few intrepid narrowboaters open-minded enough to try one -- better rudder response and working effectively to much bigger rudder angles, which is if anything even more valuable on the canals than at sea. The only reasons for not using one are probably increased cost, the fact that most (all?) boatbuilders don't offer it as an option, and entrenched disbelief that improvements in a hundred-year old motor hull design are possible because the old guys knew everything ;-) 1 Link to comment Share on other sites More sharing options...
bargemast Posted December 31, 2016 Report Share Posted December 31, 2016 For people that are stuck to (their) old ideas, all the changes that have been done over the years, and that took a lot of time to be accepted i.e.: The change from wooden to steel (iron) boats, with some hesitation at first still using a wooden bottom. Welded instead of rivetted construction, welds were something that many boat people had difficulities with too. In the future we may see more "Shilling" rudders being installed on narrowboats, for the time being, I only know of one. It all takes time, but maybe one day we will see a new kind of narrowboat arriving, with less draft and better underwater shape, as they don't have to carry cargo anymore for which the traditional shape was developped. Peter. 1 Link to comment Share on other sites More sharing options...
twbm Posted December 31, 2016 Report Share Posted December 31, 2016 Meanwhile if you have no concept of where the channel is likely to be and can't read the clues the boat constantly gives you regarding your speed and position, you'll still struggle. Bottom line, your boat's a moving hole in the water. If there's not enough space around you for the water to get past and refill it, all calculation and theory is irrelevant. Link to comment Share on other sites More sharing options...
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