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Clearing the prop


magictime

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By 'eck it's been a bit of a slog through Blackburn and Burnley! I've had to clear the prop five times in the last ten hours or so of cruising - two run-of-the-mill carrier bag/underpants combos, one with a bit of blue rope thrown in, a good chunky bike tyre, and this morning a nice fluffy duvet. 

 

So... question re: keeping the prop clear. I've got in the habit over the years of giving a quick blast of reverse when I start to suspect things feel wrong, which I thought was 'the done thing', but I'm starting to wonder if this is actually doing more harm than good because that blast of reverse is churning stuff up of the bottom and sucking it into the prop. Twice now I've tried the reverse trick and felt things have got worse: once it turned out to be the tyre, the second time the duvet, and I have to wonder if those things were even on the prop before I hit reverse. Thoughts?

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1 minute ago, magictime said:

By 'eck it's been a bit of a slog through Blackburn and Burnley! I've had to clear the prop five times in the last ten hours or so of cruising - two run-of-the-mill carrier bag/underpants combos, one with a bit of blue rope thrown in, a good chunky bike tyre, and this morning a nice fluffy duvet. 

 

So... question re: keeping the prop clear. I've got in the habit over the years of giving a quick blast of reverse when I start to suspect things feel wrong, which I thought was 'the done thing', but I'm starting to wonder if this is actually doing more harm than good because that blast of reverse is churning stuff up of the bottom and sucking it into the prop. Twice now I've tried the reverse trick and felt things have got worse: once it turned out to be the tyre, the second time the duvet, and I have to wonder if those things were even on the prop before I hit reverse. Thoughts?

It may be a function of prop size, but I have always "chucked back" with my various working and ex working boats and I have found it has saved a lot of ferreting about with the shaft clearing the blades.

 

George

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7 minutes ago, magictime said:

By 'eck it's been a bit of a slog through Blackburn and Burnley! I've had to clear the prop five times in the last ten hours or so of cruising - two run-of-the-mill carrier bag/underpants combos, one with a bit of blue rope thrown in, a good chunky bike tyre, and this morning a nice fluffy duvet. 

 

So... question re: keeping the prop clear. I've got in the habit over the years of giving a quick blast of reverse when I start to suspect things feel wrong, which I thought was 'the done thing', but I'm starting to wonder if this is actually doing more harm than good because that blast of reverse is churning stuff up of the bottom and sucking it into the prop. Twice now I've tried the reverse trick and felt things have got worse: once it turned out to be the tyre, the second time the duvet, and I have to wonder if those things were even on the prop before I hit reverse. Thoughts?

 

If you are regularly going to be in 'regular weed hatch' waters, have you considered a Kort-Nozzle ?

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I have found prop/engine size/type /draft makes a huge difference. What works well for one boat achieves nothing on another.

The section you mention I did on a 3ft draught widebeam last year. I stopped using reverse unless I really had to as half the time when I did the prop fouled and I couldnt stop anyway!

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Modern narrowboat drawing around 2', I've found going gentle, with low revs in forward and reverse when stopping in locks minimises the amount the horrors on the canal bed are stirred up and head for the prop. If you think Burnley and Blackburn were bad, try Rochdale!

 

Jen

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On that stretch I find it best to drop to neutral and coast a bit as soon as you feel something on the prop, reserving chucking back for if it doesn't work.

 

You have to coast for longer than you think sometimes.  This also works very well in Autumn whe the canals are full of leaves - you don't lose as much forward momentum as using reverse, so you can do it much more often.

Edited by TheBiscuits
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I gave up using reverse in Burnley, unless absolutely essential, about 2 weeks ago after twice getting huge amounts of plastic on the prop when using reverse, in one case losing all propulsion in either direction, and steering, and ending up bow into the far bank on a corner. I agree, reverse seems to stir up the stuff and attach it to the prop.

 

Heading back through Burnley in a few days, not looking forward to it.

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11 minutes ago, PeterCr said:

I gave up using reverse in Burnley, unless absolutely essential, about 2 weeks ago after twice getting huge amounts of plastic on the prop when using reverse, in one case losing all propulsion in either direction, and steering, and ending up bow into the far bank on a corner. I agree, reverse seems to stir up the stuff and attach it to the prop.

 

Heading back through Burnley in a few days, not looking forward to it.

Sometimes slower is faster

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I find being selective about where you engage reverse helps making sure you don't give a blast when you are in a bit likely to be full of rubbish such as near a bridge. I knock it out of gear as I go in to bridges and drift through making sure I'm well clear before engaging forward again.

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Blackburn strikes again I see.

 

The problem is I guess the locks haven't seen much use lately and all the rubbish deposited in the canal by the good folk of Nelson, Burnley, Clayton etc will have been slowly building up waiting for a juicy prop to come along.  Normally it all backs up just before the Blackburn locks so you expect a trip down the hatch as you transit the locks but usually only once unless you are really unlucky.  

 

I honestly think you would get a fouled prop in Blackburn even if you bow hauled the boat, it's that bad.

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Thanks all - yes, I think engaging reverse near bridges is exactly the mistake I made when I acquired the tyre and the duvet. I'll try to keep it as a bit of a last resort on 'problem' stretches in future, and be a bit more consistent in my use of good practice like coasting through bridges and simply going slowly. And I'll look up those Kort-Nozzle thingies.

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Using reverse is variable, if its plastic bags and stuff like that then you can often throw it off, but if its rope or clothing reverse can sometimes tie it in a knot round one of the blades.

 

My reverse technique:   wait for clear water...not a bridge ole etc.  engage reverse and go straight to full revs (with a satisfying plume of black smoke), then straight back to tickover and neutral gear (all within about 3 or 4 seconds). This does allow time to suck up crap of the bottom. Now wait about 30 seconds for all the stuff swirling about in the water to get out of the way before going back into forward. 

 

Technique not suitable for those lucky enough to have an engine with a proper flywheel.

 

............Dave

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Just about every significant prop foul I have had on three different boats has been when in reverse, and often when I was hoping to stop quickly.  I very seldom "pick up" in ahead gear.  iInow try to use reverse as little as possible where fouling is likely, and where i have to as gently as possible.  When I hit problems is is usually when i haven't managed to do that.

 

Mostly I have little success in clearing any real prop foul by short blasts of reverse.  OK for leaves and weeds.  Generally no good for assorted rubbish.

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1 hour ago, alan_fincher said:

Just about every significant prop foul I have had on three different boats has been when in reverse, and often when I was hoping to stop quickly.

Probably because, when going ahead, the boat pushes stuff out of the way before it can get to the prop. In reverse, once past the rudder, the prop is wide open to everything.

 

When I go up to the clubhouse to top up with water, and empty the bog, I usually reverse back to the mooring. (Partly because it saves time turning round, but mostly because it's good practice for when I need to reverse in anger). Every now and then I shut the throttle down to allow some rubbish to float by but, occasionally, something chunky gets by me, and I hear a clunk clunk :(  

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