Dalslandia
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Posts posted by Dalslandia
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If you can get the prop in a lathe and take of a 1/4" on each blade, with 3 blade that will reduce diameter with 3/4" (well yesterday it would)
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2 hours ago, Crow said:
Thanks lads I'm pleased your still on the case,I've got 900 rpm at tickover now It's as low as I can get Same as the book says
It same engine as vetus mariniise and call a m3 09. ,reason tickover was 1000 was the rack in the pump was to loose and was hunting real bad at 900 so that's all sorted now, all I can do is try it again then keep grinding prop blades till it comes ok,
at least I can wind leg up to do it,
If you wind the leg up it will not go so fast :-)
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I Think he said he had 1000 rpm minimum when he tested her, but have screwed it down to 900, might still be a bit on the high side.
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It have a 1.65:1 gear ratio,
What I can Think is that the strange swim slow down the water into the prop, if if wasn't it might have been different. but it would have been a very big job internal to weld in some fairings.
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yes I know, he also got the idle rpm down a bit, that will help. a lower pitch would have been the best, thats like changing gear, a boat propeller shop might be able to take the pitch down.
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I sugest a half inch smaller diameter to start with, Crow now get 3000 rpm and some black smoke, if we consider a 3600 rpm beeing standard on this Engine size, we would Think 3600/3000=1,2 or 3000/3600= 0,83 would be a good adjustment for the Power the propeller load the Engine. (as aiming Point)
prop diameter change Power with 5th Power (all the other remaining the same)
0,833^1/5= ,964
13"x,964=12,53"
with 12.5" D the Power needed at 3000 RPM will be some 82% of what ever it is now.
going to 12" and 67% is needed, I Think it is to Little.
An extention of the exhaust pipe down into the water with a row of small holes as a piccola on the way down and squize the end oval might do good on the Music, on the video the noise limiter let the mecanical noise be heared, some lead rubber and foam insulation will do good.
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I would say it is because the airfoil is cambered to work good in FW. and not at all in reverse it stall out a lot easier going backward (the propeller)
I don't understand why someone don't make a propeller with airfoils that is equal good in both directions. with some nosecamber at both the LE and TE
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My first thought was that the propeller have some cup but that is not common on low speed propellers, if the gearbox slip there will be no prop walk, atleast not more then stopping Power.
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So, you just need to mount the propeller the other way, it will go better in reverse then forward, the cone on the shaft need to taper the other way though. :-)
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We have a barras shire 50hp engine in Nightwatch.
No idea how much diesel it uses, but it didn't half move on the Ouse!!
We also have a 17" propeller on/under the back end. I sometimes think it's not big enough,as to cruise we have to maintain about 1100 revs.
Martyn
You might or might not need a different propeller, for sure.
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Thank you, I had forgot it was my birthday, this morning but was reminded by messenger.
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Liter per HP hour isn't a constant, but vary with the %load, and a small diesel engine use little more then a large engine.
.190 to .210 at WOT
but .330 at 10% power, like 4.5 HP of 45 HP ~1.5 L/h
that's why a smaller engine will be more economical on fuel in a slow boat, it need to work harder.
say it have a 20 HP engine, using the same 4.5 hp at cruise it will use ,255 l/Hph or 1,15 L/h
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stearing kort nozzle
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I have one, in a box somewhere, only time I want one is when leaving the lock before i engage the propeller, and forgot where i have the rudder. have a hydraulic steering with 7.5 turns stop to stop. 41+41 degree on the rudder, when going to 65+65 i will install it.
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The canal I trafic, most often same length every day, up or down, have some sharp bends, just after or before locks and narrow canals, most is a shallow 6 feet, plus some between the locks, I can tell by the water level in the pond between the locks how well Dalslandia will turn that day, (also depending on load) before I remade the plane plate rudder to a Schilling rudder, some turns was very marginal, will it go well or not was the question, with or without using the BT. but with the Schilling there is always a marginal if i make the turn or not, so saying that a boat can't be improved is just a way to say "I am jealous on those that have the insight"
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An NB takes about 1 liter of fuel or less per hour, if charging isn't counting, that's 3-4 HP or 2,2 - 3 kW
say 2,5 kW, (some can probably be saved without gearbox, and with a low friction prop shaft, and a big propeller.
with 10.5 kWh it will run for 4 hours between the locks. that's a full day if there is lots of locks.
1.6kW of solar will give 5-8 kW in one day in summer. so cruising one day and resting one will do. they will charge the day out cruising also.
it will not work if we say it is impossible,
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Two airfoils used on ships, the right hand one is a high lift Schilling type, the left one is almost as good with slightly less drag, in both 20 and 25% thickness, the one below is a hybrid between the two, in 25% thickness.
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I know Biggles did
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Here is some simple example of shilling that any blacksmith, should be able to do
the more refined classic Schilling and the Icecream cone rudder, one with 20% thick blade that end at 60-80% pf the blade length. and one 25% thick overlayed that goes to 100% length, is said to steer well in reverse.
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All those small trick and tips is used om F1 cars and airplanes, as well as on boats. it does not cost much to do it right from start, but cost some to re-do it afterward when the fabrikator didn't know, or thought he know better.
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Did someone not got the christmas present they wished for?
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The NACA symetric 00xx airfoil is not a bad airfoil for thin keels and rudders, like 10-15% thickness, perfect for keels and rudders on standard sailboats
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Boundary layer is the closest layer of fluid neer the surface, the transit from standing still closest to the surface to moving along with the free stream.
the boundary layer will be first laminar and then turbulent layer, the turbulent layer contain more energy and can hold on longer on the back side then the laminar flowing layer.
when the boundary flow can't follow the surface anymore because of big angles it is said to stall.
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Not once you get really picky about it!
Which weighs more? A ton of lead or a ton of feathers?
The lead, obviously....
yes, just drop it on the toe and you know...
Exhaust/ silencer
in Boat Building & Maintenance
Posted · Edited by Dalslandia
It would have been a April first joke, if I wrote it on the right day...
I suggest to start with a half inch on the diameter, that because it is what my thought and calculation say, and it is easier to take off material then add on.
Then for exhaust noise, using a pipe that goes straight down in to the water some inch, (with a 90 deg bend at the outlet from the transome) and drill a serie of small hole 1/8" on the rear side of the tube as a picola fluit. and form the end of the pipe as a oval, this sort of silencer is sometimes used on airplane. the holes will prevent it from suck water in when Engine is shut off.
The muffler Crow have is small, but there isn't much space for a bigger one under the "bonnet"
when lower one noise to the level of other noises, or less, the other noises need to to be reduced to lower the overall noise.