How Fast Are You REALLY Going.

[alan_fincher]

I've always assumed I have a fairly good idea of our speed when under way, based on things like comparing to walkers on the bank, or measured time over known distances.

 

However when we took the boat out a week ago, a friend turned up with a hand held GPS, allowing us to see rather more accurately.

 

I was quite surprised by the outcome.

 

The route was from Cowroast across Tring Summit, down the Marsworth flight of locks, and back. Tring Summit is not renowned for being the deepest bit of the Grand Union, although Chalice seems to slip through the water there better than many boats I've witnessed.

 

What we found was....

 

1) Even though I think I enter locks at a crawl, to avoid excess smoke when stopping, I was consistently driving into locks (through a single gate) at at least 2.5mph. Where this exceeded 3mph, although stopping was easily possible, our elderly engine made more smoke than I would like. I'm sure many modern boats with powerful smoke free engines enter locks at around 3mph.

 

2) Even where I pulled over just below a lock apron, where a lock was not ready, within a couple of boat lengths of starting off again I was as 2.5 to 3 mph. I thought it took much longer to get up to speed.

 

3) Across the summit, round about 3.8 mph was possible with no wash, and the engine working easily. Pushing harder the 4 mph speed limit was just about attainable, though the engine sounded much harder worked, (and was presumably using a lot of extra fuel) for only a marginal speed increase.

 

4) Trying to go faster, (and clearly wasting fuel), the boat slowed by at least half a mile per hour. It didn't feel like we were going slower, but we clearly were - conclusive proof (on this stretch, at least) that trying to exceed a certain speed is futile.

 

5) When passing through (double width) bridge holes, without touching the throttle, the boat typically lost at least 1 mph in speed. You certainly don't notice this effect, other than on the GPS.

 

6) (I'll get down firmly behind the parapet for this one, I think! ) When passing lines of moored boats, on (genuinely) little over tick-over, our speed was consistently around 2.5 mph. We were moving them almost not at all, and got quite a few friendly waves and greetings, so no evidence we were going too fast. I had assumed my speed in these circumstances to be in the range 1.5 to 2 mph, so clearly am always passing moored craft faster than I have estimated.

 

I've already learnt quite a bit from this, but now realise that when you slow for mile after mile of boats on linear moorings, you are not actually going massively slower than normal cruising speed, even though it feels very pedestrian.

 

I was sufficiently taken with the features and capabilities of the friend's GPS that we have now bought our own. So now if anyone yells "Do you know how fast you are going?", (they don't of course ), the answer will simply be "Yes!".

[magpie patrick]

Interesting stuff: I use the good old fashioned mileposts although they don't give spot speeds of course. On the G&S 4mph is comfortable, but then it is a bit deeper and wider than most canals. On the Macc we typically did 22 minute miles.

 

On the "pedestrian" bit it is common for motorists to be convinced they are being delayed when having only a couple of miles an hour knocked off their speed by the vehicle in front. I'm also guilty of this and have learnt to look at the speedo before judging whether to overtake: the number of times I'd like to be doing 50 and the lorry in front is "only" doing 48...

[WJM]

Interesting piece in one of the monthly magazines this month on operating a commercial barge in Europe. One of the key pieces of equipment is a GPS. When the driver sees a drop in speed it tells him the boat is running in shallows and needs, if possible, to move to deeper water. apparently the GPS shows the speed drop long before the humans notice it.

[johnjo]

Alan, what make & model GPS unit is it, sounds useful. Does it log time & distance travelled with coordinates and or postcodes?

John

[Bones]

When Maffi and I were on the Rochdale with RJ and Janet, RJ had a GPS thingy too. I was amazed at how slowly I drive (as was Maffi), we rarely went above 2mph and when we did make it up to 3mph we thought our hair would fly off. I suppose it makes a difference which waterway you normally cruise on, and the Oxford is quite shallow, but still!

[chris w]

2) Even where I pulled over just below a lock apron, where a lock was not ready, within a couple of boat lengths of starting off again I was as 2.5 to 3 mph. I thought it took much longer to get up to speed.

I use a GPS for speed indication too. Many a time when a fisherman has shouted at me that I am over the speed limit, I have only been doing 2.5mph. Maybe other boats go even slower, so the anglers are making a distorted relative measurement rather than an absolute measurement.

 

With regard to the acceleration you mentioned above in point (2), this is actually extremely slow acceleration (as one would expect). If you run the maths, it calculates out to be an acceleration of just about 2 INCHES per second² and it would take 27 seconds to travel 2 boat lengths (say 2 x 60 feet) from a standing start at that acceleration.

 

Chris

[Naughty Cal]

Steady on you lot you will get nose bleeds with that sort of speed and acceleration.

[alan_fincher]

Alan, what make & model GPS unit is it, sounds useful. Does it log time & distance travelled with coordinates and or postcodes?

John

Even the fairly basic one my friend had, a Garmin eTrex "Somethingorother" will do most of the above, (though co-ordinates only, I guess, not Postcodes without installed maps). His was a £30 eBay acquisition, and probably gave you all you need on canals, albeit in black and white, not colour.

 

I haven't really got to grips with the one I've bought (Garmin eTrex Venture), but it will certainly log time, (moving/static/total), distance, speed, average speed (moving/overall).

 

It also keeps tracklogs, a plot of everywhere you have been, with your statistics at points in time.

 

I did wonder if I could make much use of this without Garmin's (expensive!) maps, but find I can download into Google Earth, and it then overlays the Google Earth image with where we have been.

 

Pretty cool really, only counting the bits I've worked out how to do yet.

 

I'm sure it will do more, but I'm at the start of the learning curve.

 

A great toy, which if I ever get back to serious cycling, could have enormous application, particularly on those occasions where I've got myself "somewhere", but have no idea where "somewhere" is! It does feel a bit like big brother though, when a track on a map shows you everywhere you have been when out, including a detour to the loo!

 

Alan

 

 

 

Steady on you lot you will get nose bleeds with that sort of speed and acceleration.

Fortunately we can usually persuade our son to walk ahead with a red flag.

[Naughty Cal]

Fortunately we can usually persuade our son to walk ahead with a red flag.

 

 

How often does he have to stop and wait for you to catch up?

[alan_fincher]

How often does he have to stop and wait for you to catch up?

No idea, as he is usually home hours before we are.

[Naughty Cal]

No idea, as he is usually home hours before we are.

 

Ah but does he have the kettle on and tea and the table by the time you are home? That would be useful

[Theo]

When Maffi and I were on the Rochdale with RJ and Janet, RJ had a GPS thingy too. I was amazed at how slowly I drive (as was Maffi), we rarely went above 2mph and when we did make it up to 3mph we thought our hair would fly off. I suppose it makes a difference which waterway you normally cruise on, and the Oxford is quite shallow, but still!

I would say that that is more our experience. Unfortunately our tomtom only reads to whole miles per hour.

 

N

[NB Alnwick]

I use a GPS for speed indication too. Many a time when a fisherman has shouted at me that I am over the speed limit, I have only been doing 2.5mph. Maybe other boats go even slower, so the anglers are making a distorted relative measurement rather than an absolute measurement.

 

I also use a hand held GPS - its a fairly old model Garmin originally designed for yachtsmen but it is extremely accurate - often down to a couple of metres. Before buying the boat, (and before I retired) I used it to time the speed of trains - most of our locomotives did not have accurate speed measurement devices.

 

To get back on topic, the results on Alnwick are very different to those observed by Alan - I suspect this may be due to our deeper draught (about one metre when underway) and much larger propeller.

 

As discussed in great detail in a previous topic (click here to view) below the theoretical hull speed, the speed through the water, and its effect, is largely dependent on the amount of water beneath the boat. Alnwick rarely achieves much more than 3.0 mph on shallow canals with the engine running at 280 rpm and although this is too fast to pass moored boats without creating a slight disturbance, there is no significant 'wash' and it returns the most efficient fuel consumption (approximately 1.5 litres an hour which is equivalent to about nine miles per gallon) - we pass moored boats at a tickover (about 160 rpm) which equates to between 1.8 mph and 2.5 mph depending on depth of water and this causes minimal disturbance.

 

Nevertheless, I still enjoy giving the old Kelvin a chance to stretch her legs where conditions allow

Edited February 26, 2009 by NB Alnwick

[alan_fincher]

I would say that that is more our experience. Unfortunately our tomtom only reads to whole miles per hour.

 

N

I'm not convinced about the TomTom on a boat, Nick.

 

Unless yous is very different from our (early) one, it is programmed to try and track roads, rather than to accept it's where it really is. This I think distorts the recorded speed, as it will keep transferring it's plot of your route onto any road or track that happens to go near, (or over or under) the canal.

 

I may me wrong on this, but on the couple of occasions we took ours on board, I concluded it was meaningless.

 

I suppose it might be better on the GU Leicester Summit, where roads don't seem to exist, I'm not sure.

 

Now if later versions have a "don't track the roads" option, I'd retract all that explanation.

 

Alan

[Yoda]

I think the real answer to the above question is:- it's all relative.

[Nine of Hearts]

I think the real answer to the above question is:- it's all relative.

 

As Einstein states that energy is related to mass, I measure my speed by standing at the tiller on a set of bathroom scales and dividing the display by the speed of light squared. I find that my speed increases dramatically when I eat a sandwich.

[Ray]

I bought a Garmin 12 gps device many years ago. I tried it in my car and reckon that it wasn't too accurate when I checked my speed with several other people's speedos so I always take its results with a pinch of salt.

 

Notwithstanding that, I took it out on the boat last autumn and was surprised that I wasn't going as fast as I thought I was. I hate to "race" an engine - I judge racing on the noise it makes and if I can accept the noise it isn't racing (to my mind), so I always tend to keep the Beta 43's revs low at around 1300 rpm. That only seemed to equate to about 3.2-3.4 mph according to Garmin. I found that I need to run at around 1500 rpm to get 4mph and even with steady engine revs the speed was fluctuating.

 

Is it legal to steer a narrowboat and use a gps?

[RLWP]

As Einstein states that energy is related to mass, I measure my speed by standing at the tiller on a set of bathroom scales and dividing the display by the speed of light squared. I find that my speed increases dramatically when I eat a sandwich.

 

Yes, that would be correct. What you are measuring is the upthrust of the boat onto the soles of your shoes caused by the gravitational attraction between it's mass and your own. As you pick up the sandwich from the plate you are removing mass from the boat. As the total energy in the boat is constant, it has to speed up. Very neat.

 

Richard

[Nine of Hearts]

Yes, that would be correct. What you are measuring is the upthrust of the boat onto the soles of your shoes caused by the gravitational attraction between it's mass and your own. As you pick up the sandwich from the plate you are removing mass from the boat. As the total energy in the boat is constant, it has to speed up. Very neat.

 

Aha! So, if whilst passing moored boats the occupants were to pass me sandwiches, that would be introducing mass from outside the system and consequently I would slow down. Result!

[PaulG]

Yes, that would be correct. What you are measuring is the upthrust of the boat onto the soles of your shoes caused by the gravitational attraction between it's mass and your own. As you pick up the sandwich from the plate you are removing mass from the boat. As the total energy in the boat is constant, it has to speed up. Very neat.

 

Richard

 

Actually, for complete accuracy, the nature of the sandwich must be taken into account. Never be tempted to substitute buttered toast, for example. It is well known that this will always land butter side down when dropped, and therefore the force due to gravity will vary according to which way up you are holding the toast.

 

The power of this phenomenon can be demonstrated by the fact that UFOs are powered by large banks of cats (which always land on their feet) with buttered toast strapped to their backs, producing two opposing forces that cancel each other out, thus producing a zero-gravity field.

[RLWP]

Aha! So, if whilst passing moored boats the occupants were to pass me sandwiches, that would be introducing mass from outside the system and consequently I would slow down. Result!

 

Yes, but because everything is relative, the moored boats would speed up, so I don't think that would work.

 

Richard

 

And yes, buttered toast is especially relative.

[Tam & Di]

Yes, but because everything is relative, the moored boats would speed up, so I don't think that would work.

 

Richard

 

And yes, buttered toast is especially relative.

 

No relative of mine, as far as I know.

[Naughty Cal]

So if i were to go past a moored boat with cal at tickover, say 3mph, and someone passed me a sandwich i would slow to a reasonable pace?

 

There in lies the answer. I need a lot of sandwiches from moored boats

[mykaskin]

However when we took the boat out a week ago, a friend turned up with a hand held GPS, allowing us to see rather more accurately.

 

I was quite surprised by the outcome.

 

The route was from Cowroast across Tring Summit, down the Marsworth flight of locks, and back. Tring Summit is not renowned for being the deepest bit of the Grand Union, although Chalice seems to slip through the water there better than many boats I've witnessed.

 

I've been using what seems to be a very accurate GPS on boats for the last 3-4 years now. It's a HP IPAQ with Navman GPS sleeve.

 

I usual find that the GU is capable of 4 mph along most of it's length, except some sections that are not piled (so you have to slow down to avoid wash). Mostly you can manage 4 mph along piled sections without breaking wash (in a modern 50ft 2.2 ft draft boat), but you often get a lump of water. You sometimes need to place yourself away from the center of the canal to even out the canal profile. The summit pound is very deep and usually manage 4.5 mph easily in both Shoestring and Kismet without wash on the piled sections. The non-piled sections you do need to slow to about 3.8 mph.

 

With Victoria (71.5ft, 3.5ft unloaded motor) I found we could manage 4 mph at most places, but depth and channel widths effected her a lot more. The ice didn't help either. On the deeper pounds around London I can get 5 mph in some places without breaking wash (she will do just over 6 mph in open water).

 

Entering locks - generally 2.5 mph would be my top limit in a boat like Victoria, or Shoestring due to their poor stopping. Kismet (modern 50ft with 1.7l Isuzu) will go in much faster (my best was 4.7 mph into the top of a narrow lock from an angle without touching the sides, but I got my Dad's feet wet! :-)

 

I've yet to find extra revs on the engine slows the boat down, and usually did increase the speed, but only by 0.1 or 0.2 mph extra - most of the energy was going into heating the canal and surrouding area up. The canal and design of the boat will dictate your maximum speed, you can't go faster no mater what power you have.

 

Victoria slows down going through bridges hell of a lot - in fact you can see all the water disappearing, hence the reason for lifting off the throttle in trad boats through bridge holes. In Kismet we managed Blisworth at 5 mph average (flatout), but Victoria couldn't even manage 4 mph in the same confines.

 

I find that passing boats on deeper canals like the Paddington Arm can be done at 3 mph without problems, but shallow canals we usually pass at 2.5 mph (and get no complaints - well there is always one, and his loose ropes didn't even tighten!). Important note when passing boats, get away from them as far as possible it reduces the water flow around them.

 

Of course, 3mph sounds quite good while passing boats, but it's the same as doing 52.5 mph on a motorway. When you are doing serious distance at them speeds it starts to make a real difference. Has anyone measured the mileage of moored boats on the lower GU?

 

I bought a Garmin 12 gps device many years ago. I tried it in my car and reckon that it wasn't too accurate when I checked my speed with several other people's speedos so I always take its results with a pinch of salt.

 

Not sure of the acuracy of the Garmin 12, there can be a wide range in accuracy for speeds on GPS, but most car speedo's read high (designed that way to stop accidental speeding). I have to do 63 mph on the speedo to get to 60 mph on GPS.

 

TOM TOM's are virtually useless on canals, for speed anyway. My Dad finds his useful for finding MacDonalds while on holiday!

 

What speed where you doing there then? Very impressive looking - must be getting on for 7 mph at least.

 

Cheers,

 

Mike

[alan_fincher]

In Kismet we managed Blisworth at 5 mph average (flatout), but Victoria couldn't even manage 4 mph in the same confines.

Does the GPS work in the tunnel, or is this a case of an average speed based on time in, and time out ?