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jenevers

Hour meter yes! Tachometer why?

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I can understand having an hour meter on a canal boat, but why would someone want a tachometer?

Edited by jenevers

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23 minutes ago, jenevers said:

I can understand having an hour meter on a canal boat, but why would someone want a tachometer?

Completely agree on a diesel engined narrowboat, a complete waste of time. However on a proper boat shaped boat maybe with twin v8 jobbies it may assist.

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17 minutes ago, mrsmelly said:

Completely agree on a diesel engined narrowboat, a complete waste of time. However on a proper boat shaped boat maybe with twin v8 jobbies it may assist.

 

Balancing the revs on both engines stops you going around in circles.

 

(I've not got twin V8's, only twin straight 6's)

44 minutes ago, jenevers said:

I can understand having an hour meter on a canal boat, but why would someone want a tachometer?

It shows you the engine is running.

 

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Just now, Alan de Enfield said:

 

Balancing the revs on both engines stops you going around in circles.

 

(I've not got twin V8's, only twin straight 6's)

Yes it certainly does. Many on here though only have narrowboat experience and dont understand how twin screws work. Straight sixes have a different but very nice burble innitt.

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My boat agrees. The hour meter works fine but the tachometer only very intermittently over the last 25 years.  I suppose it might be useful for new crew, to give them a (rough) idea of the sort of speed they should be going in normal cruising, going past moored boats etc, to supplement the Mark I eyeball. 

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51 minutes ago, jenevers said:

I can understand having an hour meter on a canal boat, but why would someone want a tachometer?

 

People use it as a proxy for the speed at which they are cruising along. You see it all the time in threads on here. 

 

"I normally cruise at 1,600rpm, but if I cruise at 1,800rpm the temperature starts to rise", sort of thing. 

 

 

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4 minutes ago, mrsmelly said:

Yes it certainly does. Many on here though only have narrowboat experience and dont understand how twin screws work. Straight sixes have a different but very nice burble innitt.

Yes, but these ones are a bit 'lumpy and noisy' being Ford's. A previous boat had twin Volvo straight 6's, were nice, smooth and quiet but expensive when a Turbo 'blew up'.

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I think it depends on the engine. If you have a chug chug engine it’s fairly easy to judge the rpm. If you have a smooth multi-cylinder well silenced purring engine like ours, it is much harder. Obviously we could cope without a tacho but it would be a drawn out process of trial and error to end up at the optimum rpm. Set a random throttle position, wait for boat to settle and then adjust down if too much wash, up if going too slow. Very difficult to judge the rpm from the sound and feel (because there is no noticeable vibration).

With the tacho I simply set 1300rpm (narrow canal), 1400rpm (wide canal) 1500 rpm (river) etc and forget. 

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 I tend to go by "feel" and the prop wash, tells me much more about depth of water. The boat just feels and sounds right when all is in harmony.

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I find it quite useful. After a really long day especially on rivers when you are desperate to stop but there is nowhere to tie it can feel like you are hardly moving and the temptation is to increase speed a bit. Then a bit more. Then another bit more. Then its useful to tell yourself to slack off a bit back to the usual rpm. Also we seldom run the engine to charge batteries but about 1100 rpm (I think) is about right for temp and charging. Its not a vital bit of kit though and if it packs up it will not be at the top of the 'to do' list.

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Hire companies can use them for general guidance on appropriate speeds for their local canal.  Something like "1300 for normal crusing, but 1100 when passing other boats" is easier for novices to understand than "do not exceed 4mph and avoid creating a breaking wash or eroding the bank"

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6 minutes ago, Cheese said:

Hire companies can use them for general guidance on appropriate speeds for their local canal.  Something like "1300 for normal crusing, but 1100 when passing other boats" is easier for novices to understand than "do not exceed 4mph and avoid creating a breaking wash or eroding the bank"

Exceeding 4mph in a narrow boat on most of the network is almost a physical impossibility. A a breaking wash is easy to see and a better signal to slow down that blind reliance on a rpm reading "because the boatyard said that's OK.

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On a road vehicle you use the 'speedometer' to set your desired speed.

In a boat you only have a rev counter to give you an idea of how fast you're going.

(Yes, I know they're other ways of doing it...)

 

Possibly the only really useful function is to set the optimum engine speed for battery charging?

 

 

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2 hours ago, nicknorman said:

Obviously we could cope without a tacho but it would be a drawn out process of trial and error to end up at the optimum rpm. Set a random throttle position, wait for boat to settle and then adjust down if too much wash, up if going too slow. Very difficult to judge the rpm from the sound and feel (because there is no noticeable vibration).

With the tacho I simply set 1300rpm (narrow canal), 1400rpm (wide canal) 1500 rpm (river) etc and forget. 

 

This is the bit I just don't get. Why is it a drawn out process to get the right speed? Just set the speed lever at about the usual speed, then tweak it up or down a bit as conditions require. No need to know what the engine revs are all the time, and would work just as well with a completely silent engine. Conditions rarely stay constant for any length of time, with varying canal width and depth, bends, bridgeholes, moored boats, oncoming craft etc., so I would expect to be modifying the speed as I go anyway.

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3 hours ago, mrsmelly said:

Yes it certainly does. Many on here though only have narrowboat experience and dont understand how twin screws work. 

The OP did say "canal boat" - whilst that is somewhat broader than "narrow boat" (pardon the pun) I struggle think of a typical UK canal boat that has more than one propellor.

 

I don't doubt some such penetrate the canal system (although not very far) but I'd suggest they're not "canal boats"

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2 minutes ago, OldGoat said:

On a road vehicle you use the 'speedometer' to set your desired speed.

In a boat you only have a rev counter to give you an idea of how fast you're going.

On a road vehicle the Speedo tells you your speed within a very few percent. On a boat it gives only the vaguest indication. Actual speed (as in miles per hour over the ground) on a boat is irrelevant, your progression is limited by other factors.  With deep drafted boats on shallow waters there's actually a negative correlation. Increasing the revs pulls the stern down meaning more drag on the bottom and slower progress overall. Easing off on the engine speed can mean faster progress, less noise, lower fuel consumption, less engine wear, less wash and damage to the canal bank and less stress all around. What's not to like? Reliance on a tacho won't give any of that.

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4 hours ago, David Mack said:

 

This is the bit I just don't get. Why is it a drawn out process to get the right speed? Just set the speed lever at about the usual speed, then tweak it up or down a bit as conditions require. No need to know what the engine revs are all the time, and would work just as well with a completely silent engine. Conditions rarely stay constant for any length of time, with varying canal width and depth, bends, bridgeholes, moored boats, oncoming craft etc., so I would expect to be modifying the speed as I go anyway.

I find that 1300rpm is a good speed that suits the shallow narrow canals we mostly cruise on. We generally don’t need to slow down for bends or bridge holes (the latter only on remoter parts of BCN) or oncoming boats (because we aren’t going very fast in the first place). For moored boats we generally go to tickover. But when we do have to change speed for moored boats or occasionally other circumstances, once that circumstance is passed it is easy to get straight back to 1300rpm by looking at the gauge, rather than tweaking it over a period afterwards. Less faffy.

 

Of course you are right that without a tacho, we would still survive, but it is one of those little things that makes life slightly easier.

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8 hours ago, nicknorman said:

 

With the tacho I simply set 1300rpm (narrow canal), 1400rpm (wide canal) 1500 rpm (river) etc and forget. 

Amazing that you find all canals have the same profile & width throughout not to mention bridge holes or moored boats so you never need to vary the speed...🙄

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9 hours ago, Mike the Boilerman said:

 

People use it as a proxy for the speed at which they are cruising along. You see it all the time in threads on here. 

 

 

 

 

 

Yes, I use mine all the time to get a better idea of my speed for things like moving past moored boats.

10 hours ago, jenevers said:

I can understand having an hour meter on a canal boat, but why would someone want a tachometer?

 

Is a tachometer really any more useful on a car than on a boat? Probably not but most modern cars have them.

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6 hours ago, David Mack said:

Exceeding 4mph in a narrow boat on most of the network is almost a physical impossibility. A a breaking wash is easy to see and a better signal to slow down that blind reliance on a rpm reading "because the boatyard said that's OK.

 

Depends what you mean by "network". There are plenty of rivers both tidal and non-tidal where canal boats can go faster if they're appropriately powered, propped and cooled.

 

On the other hand if you're not including rivers in the network then you're not alone on here. A lot of narrowboaters are similarly blinkered.

Edited by blackrose

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8 minutes ago, blackrose said:

 

Depends what you mean by "network". There are plenty of rivers both tidal and non-tidal where canal boats can go faster if they're appropriately powered, propped and cooled.

 

On the other hand if you're not including rivers in the network then you're not alone on here. A lot of narrowboaters are similarly blinkered.

Just narrow-minded, shirley! :D

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2 hours ago, blackrose said:

 

Depends what you mean by "network". There are plenty of rivers both tidal and non-tidal where canal boats can go faster if they're appropriately powered, propped and cooled.

 

On the other hand if you're not including rivers in the network then you're not alone on here. A lot of narrowboaters are similarly blinkered.

Yes you're right. I meant "canal network" but missed out the word "canal" and even then would need to exclude the northeastern waterways. 

Doesn't really affect my point though. For the typical canal boat (narrow or wide), on larger waterways you can open up as much as the conditions or your engine/prop/cooling will allow without needing to know your rpm, (although you might exceed the speed limit).

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I use ours a lot. Could do without it but it just makes life easier to set a cruising speed.

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