bizzard
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Posts posted by bizzard
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Some of you may remember,way back when the QE2 was nearly new. It was returning to New York from a cruise in the Caribian and was running late. It was steaming on its usual course for that trip up the eastern seaboard of the USA and had increased speed from cruising to near maximum and was going over a shallower stretch of water as usual when its props struck bottom and damaged them. The difference in draft at these two speeds on a ship that size they reckoned was about 12 ft.which the crew had not accounted for. bizzard.
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A displacement boat given a huge amount of power and not able to climb completely over its bow wave and onto the plane will just bury itself in its own hole and sink,Known as maximum displacement hull speed.
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When the flat bottomed narrowboat's bow is higher than the stern the bottom plate is like a ramp forcing through the water, when it's level there is no obstruction to the water flow under the hull. this shows up as extra wash, which is wasted energy. If you rip the arse out of an unloaded working boat, with some ballast up the back end the wash is outrageous.
that's my pet theory, if anyone can rip it apart then go ahead.
Quite correct its trying to climb over its own bow wave. You'll notice that the faster you try and go like that the bow wave moves further and further aft.
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Thats not bad Laurie'Booth - who did them?
I was also looking at these to put in my existing steel doors: http://www.ebay.co.uk/itm/NARROWBOAT-DOOR-WINDOW-/320767389101?pt=UK_CarsParts_Vehicles_BoatEquipment_Accessories_SM&hash=item4aaf39edad#ht_500wt_949
Would be a bit nervous cutting through myself though incase i eff it up! What tool would I need??? I have a jigsaw at the mo, and drill etc. is there special blades for a jigsaw for cutting through steel?
Angle grinder with metal cutting disc along the waste side of the line and the short bits into the corners with jigsaw.
Thats not bad Laurie'Booth - who did them?
I was also looking at these to put in my existing steel doors: http://www.ebay.co.uk/itm/NARROWBOAT-DOOR-WINDOW-/320767389101?pt=UK_CarsParts_Vehicles_BoatEquipment_Accessories_SM&hash=item4aaf39edad#ht_500wt_949
Would be a bit nervous cutting through myself though incase i eff it up! What tool would I need??? I have a jigsaw at the mo, and drill etc. is there special blades for a jigsaw for cutting through steel?
Angle grinder with metal cutting disc along the waste side of the line and the short bits into the corners with jigsaw.
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You’re mistaking ventilation of a propeller for cavitation two totally different animals.
As for the rest.
Yes a fully loaded working boat will probably be still slower on the Thames than when unloaded this does not mean it is working more efficiently in that state just that it is underpowered for its displacement.
A 70 foot boat weighing 15 tons in simple terms has to shift 15 tons of water to someplace else to move 70 foot, put 25 ton of coal in it and you now have a 40 ton boat that has to shift 40 tons of water to move 70 foot. It would be interesting to see the comparison between a working boat at 15 tons and 40 tons by taking a relationship between fuel consumption/ speed and your displacement , you may find you are running allot more efficiently fully loaded than with your bows up in the air.
My own boat works better at 24 tons for a 63 foot boat if I could I would push the head down even more and I think she would be more efficient through the water.
They both amount to the same effect on the prop,Ventilation by air drawn down or a propeller either too small and or revolving too fast for a heavy displacement and so its grip efficiency on the water breaks down,can't shift the water aft anymore to provide propulsion so just makes the water boil,nowt doing,cavitation. This situation puts huge strain and stress on a propeller,a high frequency vibration and has been known to shatter them. bizzard.
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But you have to propel all that extra weight along, and displace all that extra water.
If that theory held, a loaded narrowboat should get along better than an unloaded one.
They don't, (even on the Thames!).
I wasn't concerned about weights and loads,I was just stating that a propeller is at its best efficiency deep and so less disturbed by surface popple,wavelets ect.
What you mean is, the weight and extra shove through the water although the props deeper they will cancel each other out.
A cargo ship unladen and not in ballast usually have their prop tips threshing around out of the water.So if traveling empty have to take on water and or fuel ballast,obviously for stability purposes and secondly to get that prop down deep so that it grips.
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I might measure how deep his prop is tomorrow. When in the lock and both putting our boats in gear, his churns out more water than mine. Is it the deeper the better? or maybe he just has a better pitch.
Deeper the better.Waters denser less unruffled and less likely to draw down air,and cavitate. more grip on the water.
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The ratio's need working out,i nice large diameter pulley on the alternator.
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Pointy bit down.
They do work the other way,dome or pointy bits upwards but don't shed the light so widely inside because of roof to ceiling thickness.
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I don't think it's practical. Surface speeds too high, bearing in mind theflywheel is probably a fairly imperfect piece of cast iron, plus inevitable movement from engine vibration. You might think the crankcase and mounts are a rigid item together, but they're not.
Tim
Mmm i dunno.With Cintride,tungston carbide tool bits and constant coolant and gentle feed i think its quite possible.
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Some folk seem to machine a V groove in the flywheel. Others use a polygroove belt which sits nicely on the bare flywheel surface as on this RN.
Inside out.
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Just when I thought the relay problem was solved, the new fuse blew.
I was hooked up to the mains at the time, with the chargers charging, and gave the bow thruster a few celebratory volts. Nice powerful whirring sound from up for'ard, and the bow swung round vigorously for a short distance before the bow breast rope held it in check.
Went to look at the Smartguage, and woe is me. Main batteries reading 13.85, and BT batteries reading 12.60. Both, of course, should be the same when charging (in my case the primary battery is the domestic bank, which is always fully charged when on mains power).
So, yes, the new fuse has blown. But why? The (12V) batteries are in series when powering the (24V) BT, so they must be disconnected from the charging system. How, then, can they blow the fuse in the charging circuit?
It's a conundrum.
Calm yourself Sebrof. Will dispatch Trixie forthwith to comfort you. bizzard. Short or overload,is bowthruster perfectly free to turn. You could substitute the B/t unit with a Magimixer.
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I'm getting rid of the tiny old Lucas alternator on my JP3 and want to replace it with a man-size 90amp Leece Neville. There's very little clearance for a drive belt - the old alternator was driven from a pulley behind the flywheel using one of those leather link type belts which was the only way to get a belt past the flywheel and engine bearers.
I want to run the new one using a poly-vee belt direct off the flywheel, fabricating a new alternator mounting plate. Is this likely to throw up issues? Will the flywheel surface be true enough to run a belt? At the moment the engine is not running so ought I get it running to check the trueness of the alignments before making an alternator mount?
All advice gratefully received!
I f your a bit handy with machine tools,an old centre lathe top slide tool holder could be solidly bolted to engine mount beam,and with appropriate tool bits, machine belt grooves on the flywheel with the engine running.
This is common practice on large installations such as ships engines,power station commutators ect.And reprofiling railway wheel tyres. bizzard.
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It might have paid to rev the engine on the one that caught fire as any nearby flames and smoke would be sucked into engines air intake and possibly self extinguish.
Carburetter vehicles would often pop back through the carb and sometimes set the plastic aircleaner and element alight,and the first thing to do was to restart the engine,rev it hard,hey presto fire out.
Once on holiday in Cornwall this had happened. At traffic lights an elderly couple in an HB Viva were in a big flap with flames and smoke emitting from around its bonnet and frantically throwing out all their holiday and personal effects,and me being a ''Knight of the road'' as well as the river,ran across the road at great risk ahem,grabbed the keys restarted it and revved the hell out of it,fire was sucked out by the engines carb,i then did temporary repairs to wiring, HT leads ect with insulting tape.
They were so pleased and very very grateful, i had a lump in my throat,and their holiday wasn't ruined.
I didn't charge em much. bizzard.
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Steel doors with double glazed units.
Alex
Thats it superb,and i bet if you did it yourself it didn't cost silly money.
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Do it the Bog standard way.
If during WW2 the Germans had adopted the ''Doodle Bog''instead of the ''V1Doodle Bug''it would have been far more devastating than normal ''HE''.Full up Elsans raining down all over everything would have been terrible.
However because of their lack of imagination they didn't think of it thank goodness and so lost the war.
bizzard.P--s. I wonder why we didn't think of it.The war would have been won in 2 years instead of 5.
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Where's Starry got to these last couple of days anyway? Probably discovering her boat from top to toe and wondering where she's going to stow everything. Come in, Starry, how are you and how is the boat?
She'll be full of it, the excitement,planning and all.She'll pop up sooner later with a question like. ''What sort of fenders do i need.''i expect. bozzard.
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Ahoy SC.
You are now a star in a reasonably priced boat.
bizzard. -
The perspex suggestion of Chertsey's is a good plan.
A whole sheet slid down slots from above or double hinged doors.
But to be honest with just ordinary DIY skills the existing steel doors could be converted.It doesn't need cabinet makers skills to do the following.
Take interior wood trim off,cut out rectangular window holes with jigsaw or angle grinder with metal cutting disc.You will cut straighter with an angle grinder.
Stick laminated glass with glazing silicon overlapping by about an inch on inside face. Adapt inside panels a little to fit over the 4mm or so of glass put panel back.
For the outside face,saw thin plywood sheet to the size of the doors,cut out window apertures,stick panels on steel door faces with Gripfill or No nails.Now get from any of the DIY places lengths of moulding,this comes in all widths and patterns,hardwood,usually Ramin. Buy a cheap Mitre-saw,and spend a pleasant hour or two planning and cutting with mitre saw,nice moulding surround,panel work ect.Stick onto ply panels using exterior PVA wood glue.Varnish,paint,Danish oil to finish,stand back and admire. All for i'd say less than £100.bizzard.
PS.A surform is handy for shaping edges of ply and a couple of sharp chisels for odd relieving for locks,hinges ect.
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WaS that when you entered the tunnel, or when you finally made it back out ?
We didn't back out we kept at it,going forward.The north end keeper asked if we'd broken down in there. 1 3/4 hrs.
Good old Lister SR2, the rhythm of which at that speed was heaven.
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Ah!
I think we have had the misfortune to be the next boat fed in 2 minutes after you entered Harecastle.......
It was July or August 1991.
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They invariably are upside down though. bizzard.
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Ah, but what's in the can?
Only windlasses i've ever seen or life savings?.As virtually all boats have got a water tank and pump these days,just extra weight and top hamper.
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Hey Biz, you're close, why don't you go and fetch him?
He couldn't afford me.If i was near or passing,yes. It would be a 50 or more mile round trip.
bizzard.
bizzard.
Driving an alternator direct from the flywheel
in Boat Building & Maintenance
Posted
Well maybe not then if you reckon those old flywheel castings are that crappy,too porous and rough.