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N.B. Trilby


Trilby Tim

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I like the look of that!

 

I reckon if you sharpened the edges a bit more you'be be able to scythe through any waterborne debris just by swinging the tiller round.

 

It could be a bit heavy on the arms, but there's only one way to find out, as you say.

 

Does the 'hard over in reverse' position involve swnging the tiller right round so it's pointing off the boat? Could be rather difficult getting it back again, particularly if it is heavy. Whatever you do make sure that isn't the resting position it prefers, otherwise it'll be forever swinging round and might take you with it...

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Great to see the pictures and the progress being made. The VW engine solution looks good and there are plenty about for spares. I look forward to seeing it finished - I like the underfloor heating and see no reason why it should not work - can you connect the engine cooling so that it goes through the calorifier and then the heating circuit? or are you going to use a diesel boiler?

We have shares in an R&D boat built around 1987 - It appears to be very well put together and it really swims well. Its 54ft long with a deep hull and a long elliptical stern which I'm sure helps the swim. The only boats that I've steered that are better than it are either Little Woolwich motors or Braunston copies of them.

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You're bonkers! :lol:

First the VW engine, then the flowerbed flooring, now a kitchen rudder, I can't wait for the next update :lol:

 

Love it!

- I feel a little sad inside for the poor polo having its engine removed, but cracking work, i would love to have a look over the boat sometime.

 

As a step toward altering the handling of our boat I fitted a shilling rudder a few years ago. It had a marked, if not massive, difference to handling which is quite nice. Particularly as i used fairly tame and compromised dimensions in order to fit it within the existing steelwork of the hull (Really it wanted to be longer, wider, fatter, and further away from the prop but there we go). So i look forward to who the kitchen goes.

 

But yeah. Good fun!

 

 

 

Daniel

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  • 3 weeks later...

Well, she's now on the water and she floats! :lol:

Apart from the odd teething trouble everything was pretty much a complete success. Didn't get a lot of pictures on my camera, I was too busy. My dad took a lot on his camera, but I haven't got them off him yet.

i had a pretty hectic week the week before, took time off so I could concentrate on getting the boat ready for the water. Unfortunately the weather wasn't on my side, each time I got my tools out the heavens would open and throw down on me. Mind you got a good photo out of it:

gallery_6055_419_48961.jpg

The rainbow's clearly going in through our Houdini hatch. Bloody leprechauns must have buried some gold under our shower room floor, mind you I'm not digging up the underfloor heating to find it. As you can see later we need the ballast anyway :lol:

 

gallery_6055_461_22449.jpg

On the day, the crane being set up to lift. Both companies involved (Walkers cranes and Roses Haulage) were excellent and I'd fully recommend them. Lovely sunny morning, but it didn't last. An hour later and it was chucking it down for the actual launch :lol:

 

Unfortunately didn't get any more pictures of the actual launch, I'll post some more when I get them, anyway, here she is on the water:

gallery_6055_461_78803.jpg

She was put in in Rotherham at AMA steel transportation company. You can see in this picture that she needs more ballast, especially at the back. I think the slipper stern is more buoyant than a standard one. The counter is about 3 inches out the water, so the prop is barely covered, which means that putting it into gear results in whipping up the water into a froth and only gently moving the boat. The front was a little high too, but probably will be OK when the water tank is full and all the furniture is in. This is good, because having to remove some of that concrete we'd poured in would have been very bad. For the first voyage I started the engine (first time) cast off, but got my dad to stand on the bank with hold of a rope just in case. We got about a yard before the engine cut! Brief panic before I remembered I'd not turned the fuel cock back on! It's amazing how much better an engine runs when it has fuel! As said before when you put it into gear there's much white water behind the boat, a fair bit of vibration through the tiller and only a sedate movement forwards. However once she gathers a little speed she sucks herself down into the water and suddenly the white water vanishes and everything goes very smooth. The rudder is actually better than I was expecting when travelling forwards. I was worried it would be rather twitchy like a stern drive or else would be heavy or trying to pull to one side. In fact I reckon it's better than a conventional rudder. Admittedly my only experience of a narrowboat was a fairly ancient hire boat, but that was only 40 foot, and this is much more responsive than that despite being 20 foot longer. It's also very well balanced, I could easily take my hands off the tiller and it would keep going where it was pointed. Reversing is very slow at the moment, but again there's much white water whipped up, so I'm hoping that will improve when she's ballasted down to get the prop fully into the water. She is fully controllable in reverse though, she'll easily turn left or right, likewise while stopping she can still be steered, but you do have to move the tiller in the opposite way to if the clamshells were open, which was getting me horribly confused. I think she'll be able to spin in her own length, although my only attempt at that got messed up by the wind catching us as we were broadside across the canal and carrying us off! The wind was a big feature of the day, again I reckon with more ballast she'd be less effected, and more practice on the part of the helmsman to better account for it would help too! The fact the rudder doesn't stick out from the stern also helped us get through the tight locks. On a couple of occasions on leaving a lock we had a chunk of driftwood go through the prop. It made a nasty noise and kicked the tiller, but didn't seem to do any harm. I'm really looking forward to getting her ballasted and properly putting her through her paces.

 

gallery_6055_461_61758.jpg

First journey was just down the canal to Eastwood lock where we turned round and came back to moor at Ickles lock over night. Our first experience of locks (we didn't have any on our weekend hiring) was the Tinsley flight. Luckily there was a friendly lock keeper and we were going through with another more experienced boat. However our 60 foot was bang on the limit for fitting through so we were very tight. In one of the locks the water was flooding over the top gate in a waterfall which we had the put the bows right under to just about scrape the bottom gate closed. I suppose this is the sort of thing that you get used to, but it all seemed very dramatic on a first voyage.

gallery_6055_461_8333.jpg

All in all, not bad for a first voyage, as said some teething problems to sort out, but mostly complete success :lol:

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  • 8 months later...

Some more photos now she's on her mooring.

gallery_6055_419_43434.jpg

Just about got the stove fitted before the weather really took a turn for the worse! Used thin copper sheet as a cladding behind it (masterboard with an air gap behind that). Works very well as a heat shield, you can hold your hand on it even with the stove going full tilt, and with the masterboard and air gap too there's no detectable heat coming through into the cupboard behind. Not cheap, but works out similar to expensive types of tile, was £60 for enough to do that (and I do have enough for the infill panel on the left, just haven't got round to doing it yet!). I was going to distress the copper with acid to get green and black marbling, but I decided it looks so nice as it is it's a shame to, so I'll let it distress naturally from the heat of the stove and see what patterns I get that way. If I don't like it I can always polish it back up and lacquer it.

 

gallery_6055_461_22603.jpg

Lucky we got the stove in before this happened! The boat was locked in so firmly it didn't even rock when you walked in it!.

 

Overall we're pleased so far with the results, only time (and more miles on the clock) will tell whether the more unusual additions have worked, but so far my impressions are as follows:

-Engine: Pretty good. Plenty of power, very quiet and smooth at tickover. More vibration than I'd like when cruising. It's about the same as a hire boat we had, but I was hoping to not be able to tell when it's running. I think The flywheel may not be perfectly balanced after bolting in the drive plate, I aligned it on a milling machine to drill the holes, but without any way to check the balance after fitting it must be slightly less than perfect. I'm going to take it out and have it rebalanced and more mass added. Also I still need to add soundproofing to the engine bay. If I was doing it again I would have kept the car gearbox, locked the diff, selected a forward gear to use, and used one of the drive shafts, complete with CV joints, to connect the drive. That way I'd have saved £££'s on marine gearbox and Python Drive, and I never use reverse gear anyway since the kitchen rudder works so well. Reliability's been fine so far. The only reasons it's not ran have been: Forgetting to turn the fuel on (whoops-maiden voyage as well!), an earth coming off (found in ten mins) and immobiliser problems when I mounted the ignition switch in an aluminium panel (solved when I remounted in a wooden panel, must have been the aluminium blocking the signal from the chip in the key). I did have problems with it chewing up drive belts, but it turned out I hadn't aligned the pulleys quite right and touch wood its been fine since I did that. It did start to smoke when we had been running it for hours and hours (over the course of several weeks) to charge the batteries without going anywhere. It cleaned up very quickly when we took it for a cruise, and generally doesn't smoke at all. Runs fine on 50 % bio.

-Kitchen rudder: Fantastic. Works exactly as I'd hoped now the boat's ballasted so that the rudder's actually in the water! Stops the boat in well under her own length, allows you to steer when reversing and allows you to spin the boat on the spot. Gives really good handling when going forwards too. The only vice is that it needs a lot of strength when in the reverse position. Putting power on makes the tiller pull hard across, as a fairly fit 20 something I'm fine with it, but it could do with being less heavy to use. When she first needs re-blacking I'll take the opportunity to replace the rudder shells, I reckon I can work out a more efficient shape that'll require less force to move them in the closed position.

-Underfloor heating: pretty good. The system works and does make a pleasant background heat in the front half of the boat. The problem is that the Squirrel stove just doesn't really put enough heat into the water to get the UFH warm enough. It does if you really stoke it heavily, but then you cook in the back half of the boat (where the stove actually is). Running the engine gets it lovely and warm, so it would be fine for cruising. I'm thinking of fitting a diesel or gas water heater for next winter.

-Portholes: I love them. They add so much character, condensation in winter but then I think that's true of any single glazed window. Still need to make liners for them.

-Composting loo: Generally good. Odourless, liquids need emptying once a week and solids less than once a month. I tried burning the solids on the stove, but that really wasn't a good idea, the smoke was not pleasant :lol: ! Am currently having problems with lumps forming, but I think that was caused by trying to use sawdust as bulking material, have now changed back and hopefully that'll solve it.

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. . . . . .

-Composting loo: Generally good. Odourless, liquids need emptying once a week and solids less than once a month. I tried burning the solids on the stove, but that really wasn't a good idea, the smoke was not pleasant :lol: ! Am currently having problems with lumps forming, but I think that was caused by trying to use sawdust as bulking material, have now changed back and hopefully that'll solve it.

 

Great photographs Tim . . and the update is very interesting . .

 

With regards to the Composting Loo / lumps forming

 

You shouldn't eat sawdust - not even as a bulking material - - All Bran should work perfectly

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  • 6 months later...

During the course of the year I've been having some problems with the drive system. Being a prototype, it's not entirely surprising, also the blacking was in a state after we went ice-breaking in February so I decided to have the boat out the water to re black and fit an improved rudder. The issues I wanted to improve were:

-Generally better engineer the rudder. It was too flimsy, and bumping it on things like lock gates (the boat is 60 feet long and we have a flight of 61 ft locks to go through if we want to get anywhere, so bumps happen!) had made one of the shells slip on it's shaft. This meant it wasn't closing or opening fully and was getting very stiff to operate.

-Improve the shape of the shells. I think the old shells were making a major contribution to drag and their shape made them very heavy to operate in reverse.

-Reduce noise and vibration. Bearing in mind the engine itself is very quiet and smooth, there was way too much noise and vibration when we were under way, and also white water behind the boat. I thought this was partly due to the shaping of the shells and their increased drag and partly due to overloading the engine with too big a prop. The engine could only rev to 1500rpm flat out, and being a car engine which redlines at over 4000 rpm, this is very low revs for it.

So, it came out the water, I fitted a reduced pitch prop, a weed cutter to the prop shaft and a re-designed rudder. Unfortunately I didn't get any photos while it was out the water! I was working on the rudder right down to the wire and there was someone queuing behind me to use the slipway, so by the time I'd finished work I didn't get time to grab my camera before it was going back in the water! I've got the CAD drawing of the new rudder here:

gallery_6055_402_7778.jpg

You can see I've added fixed sections to the hull that extend below the water slightly beyond the rudder to protect it from bumps. You can also see the top one in the photo here:

gallery_6055_461_136421.jpg

And there's a better view of the redesigned mechanism here:

gallery_6055_461_78141.jpg

 

On the whole, the results have been good. It feels much sturdier, there's no slack in the mechanism and it's really smooth to operate. It's less heavy to steer in the closed position, but still a little heavier than I'd like. I need to put a stop on the hinge because the shells now try to push further open and push the tiller against the handrail, but that should be fairly simple to sort. The engine sounds much happier to be allowed to rev a little higher. I logged some of the data from the engine while I was on straight sections of the South Yorkshire Navigation on the way out and the way back. Fuel efficiency at tickover went up from 22mpg to 25mpg, although at 40% throttle it went down from 17 mpg to 16 mpg. The speed at 40 % throttle went up from 4.3 to 4.4 mph though. Propeller slip was reduced at tickover from 36 to 31 % and at 40 % throttle from 38 to 35 %, although this is still a little higher than I'd like. Just as well that it is working well again. On the way back up the Tinsley Flight the gear shift cable broke sticking us in forwards gear. Being able to stop and reverse with the engine running forwards is definitely good in that situation.

The biggest problem is that the vibration hasn't gone away. At low throttle settings it's pretty much gone, I think the fact the engine's no longer labouring has cured this. But it suddenly kicks in at around 3.5mph (about 30 % throttle). I now think it's due to the prop starting to cavitate. Possibly the shaping of the shells is restricting the flow of water onto the prop. At least the design of the shells should now allow me to remove them while the boat's in the water (I'll need a wetsuit :lol: ), so for next year I might try re-shaping them again. Either that or get an equipoise prop. Anyways, now that it's all working reliably again SWMBO has decreed that I should get on with finishing the inside of the boat before doing any more tinkering to the rudder!

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  • 3 weeks later...

Good to hear an update!

 

I presume that so far 'no news is good news' on the topic of picking up debris and getting jammed up with stuff?

 

From the above cad image and photos, you lift to reverse. Then the tiller/swanneck then drop down level in to cruse? Onto the stops that arnt there.

 

Any videos of turning/stopping manoeuvres?

 

 

Daniel

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  • 2 months later...

http://www.youtube.com/watch?v=q-p5ic2jAB8


Just got round to uploading a video of the rudder in action, you can see how it effectively works like a stern thruster, still need some adjustment to get it to close more completely, but I'm waiting til next summer to do that in a wetsuit! The engine's in forward gear for the whole manoeuvre, the only time the throttle control is needed is just to reduce the revs a bit as I open the rudder to move forwards. Edited by Tim Swait
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http://www.youtube.com/watch?v=q-p5ic2jAB8

Just got round to uploading a video of the rudder in action, you can see how it effectively works like a stern thruster, still need some adjustment to get it to close more completely, but I'm waiting til next summer to do that in a wetsuit! The engine's in forward gear for the whole manoeuvre, the only time the throttle control is needed is just to reduce the revs a bit as I open the rudder to move forwards.

Cant believe Ive missed this thread. Good man not going with the flow!. Kitchen rudders were fitted by the admiralty especially to Dorman engines. I have had a few Droman engines through my hands and most have just Clutches on the back, no gearbox The housing looks the same just not the same internals. Never actually seena kitchen rudder, I was always let to belive it was another name for a variable pitch type prop thingamajig, never to old to learn!! good job on the build and silenced some disbelievers I,m sure. Well done that man.

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  • 3 months later...

I've just been referenced to this blog, Tim.

 

I'm interested in how the Kitchen gear works on a narrowboat having used it in my navy days.

 

I note you find steering rather stiff, but could that be because the end of the tiller arm is not far forward from the fulcrum point of the gear?

 

Are you picking up a load of crap from the water?

 

How is access to the prop for clearing it? Sufficient?

 

cheers

 

Tone

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The steering's only heavy in reverse, in forwards it's fine. I think you're partly right about the short leverage, you can see when the tiller is in the up (rudder closed) position the horizontal distance between the pivot point and the grip is shorter. However I think it's also got a lot to do with the shape of the clamshells when they're closed. It tries to pull strongly across to full deflection one way or the other when you give the engine some welly and the rudder's closed. I don't have very much experience controlling conventionally ruddered boats in reverse, although I've heard this also happens with these (put the engine in hard astern and the tiller will push strongly to full deflection on one side or the other). I'm not sure if it's any worse with the kitchen rudder.

Again, I don't really have enough experience with conventionally ruddered boats to make a direct comparison on picking up debris round the prop. I did sometimes get bags and weed wrapped around it, but it wasn't too hard to remove (although probably harder than with a conventional set up as the prop's set slightly back from the hatch so you have to reach further). When I fitted the Mk2 design I also fitted a R&D rope cutter, and I haven't had anything foul the prop since.

What did you use the kitchen rudder on in the navy? Was it the pinnace cutters? How did it work on those? Did you find the tiller push across when opened the throttle in reverse? Was it closed by winding a handle on the tiller?

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I've been wracking my bit of brain (wots left) trying to visualise how the controls looked on Kitchen steered motor cutters and pinnaces, but it was all some fifty years ago.

 

I seem to remember that there were two kinds, a smaller version for motor cutters that was steered by tiller, with a wheel attached for forward and reverse. I'm pretty sure that I also skippered a pinnace, an admirals 'barge', that had wheeled steering, with a smaller wheel alongside for forward and reverse.

 

In my land-based store I have my old seamanship manuals, and I'm sure there were full instructions and diagrams in them. Next time I go to the store I'll dig 'em out.

 

Yes, holding a rudder over whilst steering in reverse is quite hard as it does not naturally centre, as it would going forward.

 

I can't remember Kitchen gear being any harder to control in reverse. It was always quite stiff to steer though.

 

Have you seen this? There's a lot of info if you scroll down

 

http://www.scribd.com/doc/22236032/Kitchen-Rudders-Going-Full-Circle

 

And I found this quite amusing:

 

 

Is the stand-alone lever on the left of your steering position the throttle?

 

Tone

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That's a really good article, I'd not seen it before. I had seen most of the drawings, but I hadn't heard of Ranger One before. It looks quite a neat arrangement with the large steering wheel and a smaller concentric wheel for opening and closing the rudder. A very complex arrangement of linkages and chains to operate that though. It would be something that would be much easier to make nowadays using hydraulics.

Yes, the stand alone lever is a conventional Morse throttle/gear shift. When I was fitting the engine I wasn't 100 % sure how well the kitchen rudder would work so I fitted the engine to a standard marine gearbox with forwards and reverse. I never really use the reverse gear on the box though, so in hindsight I could have saved myself ££££ by keeping the car gearbox, locking it into a gear and relying on the rudder.

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I've been wracking my bit of brain (wots left) trying to visualise how the controls looked on Kitchen steered motor cutters and pinnaces, but it was all some fifty years ago.

 

I seem to remember that there were two kinds, a smaller version for motor cutters that was steered by tiller, with a wheel attached for forward and reverse. I'm pretty sure that I also skippered a pinnace, an admirals 'barge', that had wheeled steering, with a smaller wheel alongside for forward and reverse.

 

In my land-based store I have my old seamanship manuals, and I'm sure there were full instructions and diagrams in them. Next time I go to the store I'll dig 'em out.

 

Yes, holding a rudder over whilst steering in reverse is quite hard as it does not naturally centre, as it would going forward.

 

I can't remember Kitchen gear being any harder to control in reverse. It was always quite stiff to steer though.

 

Have you seen this? There's a lot of info if you scroll down

 

http://www.scribd.com/doc/22236032/Kitchen-Rudders-Going-Full-Circle

 

And I found this quite amusing:

 

 

Is the stand-alone lever on the left of your steering position the throttle?

 

Tone

 

 

Hello Tone,

 

thank you very much for posting all those details about the workings of the "Kitchen Rudder Gear", I'm really pleased to be able to study this subjet a bit more in depth now.

 

Peter.

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  • 2 years later...

I know this is an old thread, but still interesting.

Trilby Tim,

As they said in the commercial, "I am not just a dentist I am a mother too"

I am not just a canal boat Skipper, I am also a airplane propeller designer, www.jcpropellerdesign.com (and a father too) and have also studied ducted propellers (Kort) and shrouded propellers a little. I designed a Shilling rudder of my own design, for my canal boat. www.dalslandia.com

onboard her I have passed 50-60.000 locks.

 

When reading about your vibrations from propeller, I can think of 2 reasons in relation to the Kitchen rudder.

At forward drive with some amount of power, the propeller sucks in (induce) a lot more water then the forward speed, you say you have about 35% slip.

if we consider the slowed down water at the rear of the keel we can think it is even higher, maybe 50% When accelerating probably 100%

this mean the propeller suck in water into the duct or shroud shaped rudder with a lot of force and speed, so the water isn't coming from just straight a head of the duct but also from the side like a trumpet shaped funnel. at low speed the water even come from behind of the leading edge lip, So the water is going around this lip at a high velocity so it can't follow the inner side of the entrance if it is to sharp, (think centrifugal force here) So it need a big radius lip for the water to stay attached and not going turbulent, a good lip here will also give extra thrust.

 

The other reason I can think of is the shape of the hull just forward of the propeller, yours look somewhat blunt, it rise 2 questions can the water follow the sides? and at what angle is the water going into the duct and propeller?

 

Will a propeller with more rake be better?

 

 

Jan

Edited by Dalslandia
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  • 2 years later...

Hi Tim,

I have a quick question. How are you finding your under floor heating? Also what flooring finish did you put on it in the end, carpet or wood ect?

 

It is so nice to see a boat that pushes the designs. I am going to build a kitchen rudder for mine (though the Becker looks quite good too!) and hope to be having under floor heating if I can!

 

All the best

Chris

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  • 3 months later...

Sorry, not been on this forum in ages. The underfloor heating is nice, and still working without problem (touch-wood) after 5 years, which is a lot more than can be said for the Mikuni that I often use to heat it!

The wood-burning stove doesn't really put enough heat into the water to be very effective at heating the UFH, unless you really stoke it up heavily! However the stove alone does do enough to take the chill the chill off the floor even though it doesn't really heat the bedroom/showeroom that effectively. Running the engine is very effective at heating the UFH and gets the rooms nice and warm. When the Mikuni is actually working then this also heats the UFH very effectively. If the UFH is properly warm (i.e. has been heated by the engine or the Mikuni, not just by the stove) when I go to bed then it will still have some warmth in it when I wake up.

I've put tiles on it as you can see in this image below. The more insulation you have between the heating and the air the worse the performance of the UFH will be, so tiles best, wood or laminate OK, thin carpet bad, thick carpet hopeless.

Showeroom and bedroom

One point if you're having a shell built: I recommend getting lower pieces of angle section floor bearers welded into the floor in the area you're fitting the UFH. I have 2" angle across the floor all the way through. These are ideal if you're screwing a wooden floor to them and have to fit ballast underneath, but in the case of the UFH they get in the way and I wish I had had 1" used in the UFH area. I had 2" of sprayfoam put over the floor in the UFH area, so where the angle irons were there were really big lumps! This then meant that laying the pipes was hard and when the concrete went down it couldn't be constant thickness and was really hard to get level. In the end I had to put more floor levelling compound over the top of the concrete, and then the tiles on top of that. The extra floor levelling screed also helped ballast the boat better as she was a little high at the front when she went on the water. The floor in the UFH area has ended up about the same height as the floor in the rest of the boat despite the difficulty though.

I was worried that a lot of heat would be wasted into the water, but this doesn't appear to be the case. The UFH seems to hold it's heat well, as I say it's often still warm in the morning even when there's been nothing heating it overnight. Also on the occasions when the canal has been frozen over I've not noticed the ice melting around the front (UFH area) of the boat any differently to around the back (not UFH area), so I don't think much heat is being lost into the water.

 

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  • 1 month later...
  • 7 years later...

 

So, 10 years on and the latest instalment in the engineering vanity project known as fitting a kitchen rudder to a narrowboat! Earlier in the year I tried to take the boat out for a cruise but one of the rudder clamshells failed around the weld on the top. I think this was galvanic corrosion caused by the stainless steel shafts (at least as it runs in plastic bushes the shafts and rudder are isolated from the hull of the boat anyway). Actually the boat was still pretty controllable with only half the kitchen rudder (once I managed to remove the half that was now loose), probably about as manoeuvrable as a normal narrowboat. I did consider replacing the kitchen rudder with something simpler like a Kort nozzle, but basic stubbornness made me double down, design a new version of the rudder, get it made and fit it with a new prop and new gearbox. I attempted to use CFD to design it, but wasn't able to get very meaningful results so ended up using rules of thumb and intuition again. Got the new version fitted and the boat refloated a week ago and I have to say, it's pretty good, a definite improvement over the previous version. The boat stops very quickly, requires less force on the tiller to do it and it still spins on the spot or steers where you want it in forwards or reverse. It really is very manoeuvrable indeed. Still not perfect though, now it's introduced a directional instability into it in forwards (open) position, which is very annoying. The next time it's out the water I'll need to do more changes, although I'll probably just be able to do it by fettling this one with an angle grinder (remove area from in front of the pivot line) rather than making a whole new version. The new prop and gearbox are also a big improvement, it allows the engine to rev more comfortably and I don't get cavitation like previously, it just seems to grip the water and go.

 

If anyone else is remotely tempted to indulge in engineering self-flagellation then I've made the whole design Open Source, so you can download it from here:

https://gitlab.com/trilbytim/kitchen-rudder

If anyone has any CFD skills and fancies a bit of a challenge then it could be a really interesting design problem. I've included my attempts in Sparselizard and OpenFOAM in the repo. It would be interesting to really optimise the shapes of those clamshells using CFD.

 

2krudder4.jpg.696374caf453c9a661c91fd9502b74ba.jpg2krudder3.jpg.bfd0dc2e1214cb12d9530072cac57234.jpg2krudder2.jpg.c75bf97512fb0c0958c37b3bf2e51369.jpg2krudder1.jpg.e477c95477ba16d59d6c9055fe2a1972.jpg

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