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Canal Runner

What happens to boat speed in tunnels / shallow / narrow sections?

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Hello! My first post as I've just discovered this forum. In October I had the great pleasure of narrowboating for the first time when we hired a 50ft narrowboat for a long weekend.

 

On our first passing through Braunston Tunnel, I just chugged along a discrete distance behind a boat in front. On the way back, I had a clear view all the way through. I set the throttle reasonably low for a quiet life and found I was making reasonable, if not amazing progress. However, there was a boat coming up from behind at quite a pace and it had caught me by the middle of the tunnel, in spite of my moving the revs up a notch. If anything, I seemed to lose boat speed relative to the tunnel, especially when the following boat came within a few metres of my stern. I'm not sure what was happening to my speed through the water though. I then heard a somewhat impatient shout telling me to "get a move on!", to which I replied that this was my maximum speed. I pushed the throttle forward more, but just got a louder noise. A couple of questions:

 

1) As a matter of etiquette, should I have tried to let him past? I would not have been confident in steering the boat tight alongside the wall for the amount of time it would have taken, accounting for his wash etc. I pulled over as soon as we were out of the tunnel.

 

2) Is there something hydrodynamic going on, which means I lose boat speed when another boat is close behind. Something like generating a local counter-current so the boat squats down in the water more and has to climb a steeper bow wave? Or could it be that the prop was not suitable for the higher revs and was just churning the water or cavitating?

 

 

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Two possible effects in play. One is shallow water effect where more power will tend to squat the back end down without adding speed. The other is that you're pushing a wedge of water ahead of you which has to rush back past you slowing you down. This is more noticeable in narrower gaps, such as single track tunnels or aqueducts. Telford very cleverly counters this on the Pontcysyllte Aqueduct where the narrow trough actually extends under the towpath to allow the opposing flow somewhere to go.

 

Oh, and the man behind was quite possibly an impatient git. ;)

  • Greenie 1

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October? Leaves on the prop without a doubt

 

Quick burst of revs in reverse would have cleared it.

 

In narrow, shallow, places dropping the revs is always good because high revs will drag the bottom down etc reducing hydrodynamic efficiency so yes you are right about that.

 

The bloke behind you? his job is to maintain his distance or offer a positive solution - not risk pushing you into an error

 

He was a pillock

Edited by Barry

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Oh, and the man behind was quite possibly an impatient git. ;)[/quote

 

I think this is the truth of the story.

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October? Leaves on the prop without a doubt

 

Quick burst of revs in reverse would have cleared it.

 

In narrow, shallow, places dropping the revs is always good because high revs will drag the bottom down etc reducing hydrodynamic efficiency so yes you are right about that.

 

The bloke behind you? his job is to maintain his distance or offer a positive solution - not risk pushing you into an error

 

He was a pillock

 

 

I'd go further than that. I'd say he was a grass hole.

 

Totally unacceptable behaviour. Far better to have sent someone to the bow of his boat to enquire of you calmly if there was a problem, as you seemed to be going rather slowly.

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He was probably scared stiff and desperate to get out. Also the boat could be pushing a big tree branch along, stuck on its bow. Happens a lot around here.

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Thanks for the replies. I did check the prop once out of the tunnel and there was nothing snagging it, but then I guess any leaves fell away when I pulled in to the bank.

 

Also, I'm glad that your views on the following skipper match mine! With this one exception, we were welcomed, helped and our newbie errors forgiven with ready smiles the rest of the time. Overall, we finished our little cruise with a very positive view of canal folk.

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I'm happy to be corrected by those it may have happened to, but I wouldn't really expect leaf fall to be a major problem in Braunston tunnel.

 

I accept there is some very slow flow, and some will get drawn in, but I wouldn't expect amounts large enough to produce adverse effects all the way through.

 

It's also fairly deep, and I'm surprised if putting on a bit more revs in a typical hire boat (usually shallow draughted), would cause the boat to squat down and slow down.

 

Most boats will easily make normal maximum canal speed through this tunnel, even deep draughted ones.

 

I think if you are not used to steering narrow boats through tunnels that judging actual speed is really quite difficult.

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If someone gets too close to me and stays there when driving a car, I pull over sharply, but safely, and let them past - I might slow down gradually, then stop, so they have to pull out to overtake. Sometimes they're hacked off at what I've done, and other times I get thanked for letting them by.

 

If I had this experience in a tunnel, I'd probably stop and ask what the rush was as they were passing. If there wasn't room to pass, I'd stop and ask them what the problem was, or just slow down even more, or something equally irritating.

 

Why be on a canal if you're in a hurry????

  • Greenie 1

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I went through Braunston tunnel many times and all I can say is that you stick to whatever speed you feel comfortable with and can manage boat..as tio him behind...well he should slow down..overtaking in a tunnel to me a no no

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Why be on a canal if you're in a hurry????

 

Do you really have so little imagination?

 

 

1) You want to get to the pub before it closes

2) You want to get to the pub before they stop serving food

3) You want to get to your mooring before nightfall

4) You need to get back to the hire base by close of trading or lose your deposit

5) You need to get past the three week CRT stoppage starting in the morning

6) You need to get back to your mooring as you have to get to your car to go to work in the morning

7) You're low on diesel and the yard two miles away closes in half an hour and it's closed on Mondays (tomorrow)

8) You need to get to the railway station to catch the last train back to where you left the car

 

 

Any more reasons to be boating to a deadline, anyone?

 

When I'm boating its rare not to be trying to get somewhere by some particular time or other!

  • Greenie 3

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Wouldn't a boat close behind be a drag on the one ahead? In any channel of limited depth or width, you can see the water ahead being pulled being pulled towards you (bending of reeds, etc.)so a boat close behind will slow down the one in front. No?

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Wouldn't a boat close behind be a drag on the one ahead? In any channel of limited depth or width, you can see the water ahead being pulled being pulled towards you (bending of reeds, etc.)so a boat close behind will slow down the one in front. No?

I must admit I thought that the draw of water from a boat close behind could slow you down in a narrow channel such as in a tunnel.

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Wouldn't a boat close behind be a drag on the one ahead? In any channel of limited depth or width, you can see the water ahead being pulled being pulled towards you (bending of reeds, etc.)so a boat close behind will slow down the one in front. No?

 

Well, I couldn't see what the water was doing, being blinded by his headlight and concentrating on not hitting the walls. However, I got the distinct impression from looking at the brickwork that our boat slowed when he came close. The irony was that he complained about the fumes as he passed us out of the tunnel.

 

As for being in a hurry, it turned out that he was returning to the same boatyard as we were. I was happy not to be going down through the locks with him.

 

Sorry, I didn't really want this to turn into a moan about another boater. More a query about my canal etiquette and the best way of making way through tunnels.

Edited by Canal Runner

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Do you really have so little imagination?

 

 

1) You want to get to the pub before it closes

2) You want to get to the pub before they stop serving food

3) You want to get to your mooring before nightfall

4) You need to get back to the hire base by close of trading or lose your deposit

5) You need to get past the three week CRT stoppage starting in the morning

6) You need to get back to your mooring as you have to get to your car to go to work in the morning

7) You're low on diesel and the yard two miles away closes in half an hour and it's closed on Mondays (tomorrow)

8) You need to get to the railway station to catch the last train back to where you left the car

 

 

Any more reasons to be boating to a deadline, anyone?

 

When I'm boating its rare not to be trying to get somewhere by some particular time or other!

Thanks Mike, I absolutely agree, sometimes reading posts on here I feel I should be feeling guilty for needing to be in a certain place at a certain time. I think we should all be free to use the canals in a way that suits us as long as it doesn't impact on other users of the canal or the canal structure itself. (as in the case of the original post when clearly the second boat should have hung back and slowed down.)

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Any more reasons to be boating to a deadline, anyone?

 

Roving traders need to get to the next floating market, fair, festival, selling venue

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Do you really have so little imagination?

 

 

1) You want to get to the pub before it closes

2) You want to get to the pub before they stop serving food

3) You want to get to your mooring before nightfall

4) You need to get back to the hire base by close of trading or lose your deposit

5) You need to get past the three week CRT stoppage starting in the morning

6) You need to get back to your mooring as you have to get to your car to go to work in the morning

7) You're low on diesel and the yard two miles away closes in half an hour and it's closed on Mondays (tomorrow)

8) You need to get to the railway station to catch the last train back to where you left the car

 

 

Any more reasons to be boating to a deadline, anyone?

 

When I'm boating its rare not to be trying to get somewhere by some particular time or other!

I had to get from Birmingham to Huddersfield in a hurry once. I had left a job in Brum and taken a job in Hudds and only had a limited number of days to make the trip. Every day I was in a hurry.

 

A year later, I had the same problem coming back the other way.

 

Another reason for hurrying is that you have a booking for certain tunnel, lock, sea passage etc. and you're trying to make the booking time.

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Any more reasons to be boating to a deadline, anyone?

 

When I'm boating its rare not to be trying to get somewhere by some particular time or other!

 

I don't think it needs a specific deadline. Some people walk briskly, some like to dawdle - boating is not different. There is certainly no edict that says you have to go slowly other than whatever speed limits there are. Even those are often silly - I am more persuaded by not making substantial waves, and sometimes that can be less than the limit and sometimes more than the limit. I won't press someone who is dawdling if there is no way to get past, but once there is room I will expect to.

 

Tam

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I think everybody should be allowed to go at whatever speed they want as long as that doesn't mean that other boaters suffer. If there's a very slow boat in front of me and I catch him up, I hope he will let me pass when safe so we can both proceed at our preferred speed. If he doesn't then he is imposing his regime on me and that isn't fair. In my view, not enough boats do move over for those who may be in a hurry for whatever reason.

Edited by Proper Charlie
  • Greenie 3

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I think everybody should be allowed to go at whatever speed they want as long as that doesn't mean that other boaters suffer. If there's a very slow boat in front of me and I catch him up, I hope he will let me pass when safe so we can both proceed at our preferred speed. If he doesn't then he is imposing his regime on me and that isn't fair. In my view, not enough boats do move over for those who may be in a hurry for whatever reason.

You are exactly paraphrasing what I wrote in a different thread earlier this morning - except that I quite often find that the "pootler" in front does move over, or pull up completely, to let me past.

 

Canal Runner, there is nothing wrong with your canal etiquettes as far as I can discern. The chap behind, howver...

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