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Why do some narrowboats appear to sit stern down in the water?


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Why do some narrowboats appear higher at the bow than at the stern? Are they meant to do this or do they just have too much weight at the back? Does this mean that the floor inside the boat also slopes?

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Design, I think. You want the prop nice and deep. Plus, the engine, mostly these days at the stern, is the heaviest thing on the boat, balanced a bit by the water tank at the front.  Hard to balance out that great lump of iron.

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My take on this is - the stern is lower to keep the uxter plate below water level so there is less chance of the propellor being near the surface of the water and sucking air down.

 

I am not aware of our boats floor sloping.

 

Crossed with Arthur.

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Working narrow boats were designed to be loaded so the gunwale was more or less level and a few inches above the water line. When empty, horse boats and butties are similarly level, with only a few inches draft. Empty motor boats have the stern ballasted down, to keep the prop in the water, and because the weight of the engine is there. 

Modern leisure narrowboats are loosely based on the design of working motor boats, and so the slope of an unloaded boat was carried through. You can of course ballast a boat level if you wish, but that involves putting a lot of paving slabs, bricks or chunks of steel under most of the floor.

And yes the floor does slope (along with beds, tables, kitchen worktops etc.). Do you notice it? No, as long as the outlet from sinks and shower trays is arranged to be at the downhill end.

Edited by David Mack
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Not directly part of this discussion - but it helps the boat swim better if the bow is slightly up. We hired a boat many. many years ago which was trimmed 'dead flat' and it steered like a pig...

 

Come to think of it - I have two tons (!) of batteries just forward of the engine which is rear mounted and it swims beautifully.....

Edited by OldGoat
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Lots of boats in Winter have empty water tanks at front and full fuel tanks at back.

 

A friend has just moved a 70 foot boat up North,  the tank was filled before he set off, and as the boat has an enormous bath, it also has an enormous water tank. Front end gunnel was about 2" lower than rear end gunnel. The boat steered like a pig, even after keeping a tap running for most of the first day.

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Can confirm the notes about trim - having its butt sit heavy in the water is always a good thing. Mine has an rather large water tank in bow bow at just over 1000 litres and to make it steer nicely when the tank is full, I've had to heavily ballast the back. This means when the tank's empty, the back sits noticeably lower...and the sliding bathroom door closes itself.

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3 hours ago, Northener said:

Why do some narrowboats appear higher at the bow than at the stern? Are they meant to do this or do they just have too much weight at the back? Does this mean that the floor inside the boat also slopes?

 

 

It's to make them look as if they're going faster.

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To add....... Any water in the bilge will drain to the lowest point where the bilge pump is. Alot of older boats had a wet bilge with front well decks lower than the waterline.

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Most boats ( and all ships!) steer much better with some stern trim as mentioned above by other people of this parish.    
 

if level,  or worse bow down, you will have to work harder to steer, this is called “griping” aka “steers like a pig”! 

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15 hours ago, David Mack said:

And yes the floor does slope (along with beds, tables, kitchen worktops etc.). Do you notice it? No, as long as the outlet from sinks and shower trays is arranged to be at the downhill end.

 

When we had the 74' x 12' 6" wide boat Progress the floor sloped to the stern to some extent. We didn't really notice it until we were in dry dock for the first time; our bodies were subliminally used to putting a bit more effort into walking forward, and in the dock it felt very odd  and suddenly we stumbled walking towards the front now it was level.

 

Tam

Edited by Tam & Di
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1 hour ago, Tam & Di said:

 

When we had the 74' x 12' 6" wide boat Progress the floor sloped to the stern to some extent. We didn't really notice it until we were in dry dock for the first time; our bodies were subliminally used to putting a bit more effort into walking forward, and in the dock it felt very odd  and suddenly we stumbled walking towards the front now it was level.

 

Tam

Oh yes, I get this too. It feels very weird.  My boat has a very slight slope down to the stern.  If I put cans in the fridge on their side, they roll towards the stern.

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If boats handle so badly when ballasted flat or bow down why do barges in Europe tend to load bow down? Every boat I have had has handled better the flatter it's ballasted.

 

DSCF1364.JPG

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Our last but one boat carried about a ton of water in its tank. I believe it was designed to go best with a full tank, and definitely looked and handled well just after I spent a looooong time at a water point.

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31 minutes ago, Loddon said:

If boats handle so badly when ballasted flat or bow down why do barges in Europe tend to load bow down? Every boat I have had has handled better the flatter it's ballasted.

 

Love the photo ? 

I've not steered anything like a modern narrowboat to any extent to know their generic handling characteristics, but I'd guess they differ from each other anyway. I've never had any problems with those I have steered though, and my inclination would be to ballast them to an even trim.

Certainly with loaded boats, here as well as continental, you do load slightly bow down as they steer better like that. With narrowboats on typical shallow UK canals it means you hit the bottom and sunken debis with the bow rather than mangling the prop, though in shallow water the stern will tend to pull down quite a bit under power too. Also butties don't have a watertight bulkhead between the hold and cabin so it's better to have any rain water run forward.

 

Tam

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16 minutes ago, Tam & Di said:

Love the photo ? 

 

That was taken on a trip with John Wheatcroft on Final Fling up to Gorinchem in 2006.

As you may guess there are more?

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8 hours ago, Hudds Lad said:

And yet you’ll still see boats with sinks fitted with the draining board facing the stern not the bow, sorry, pet hate.

Yes, we’ve got that. Water collects against the back wall and eventually drips down it. We now put washing up on a plastic tray sitting on the draining board, and have a number of routine procedures to minimise rotting of the wood but so unnecessary! 

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22 hours ago, Loddon said:

If boats handle so badly when ballasted flat or bow down why do barges in Europe tend to load bow down? Every boat I have had has handled better the flatter it's ballasted.

 


Because the engine room is at the back and is of more or less fixed mass. The cargo loading area is middle - front and so an unloaded barge will sit nose up, a loaded barge will sit level and a barge fully loaded to the maximum permitted will sit nose down. On a big river being deeper at the front doesn’t matter much. On our shallow muddy ditches it is better to have the draft at the bow much less than the draft at the stern, amongst other things it makes it easier to wind in shallow waters and easier to steer. Never tried it but I’m confident that a fully loaded narrowboat is fine on a deep canal / river, and a bit of a pig on a shallow canal.

 

That said a very lightly ballasted bow will tend to get blown sideways by the wind, so as with all things the middle path is best.

Edited by nicknorman
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24 minutes ago, nicknorman said:


Because the engine room is at the back and is of more or less fixed mass. The cargo loading area is middle - front and so an unloaded barge will sit nose up, a loaded barge will sit level and a barge fully loaded to the maximum permitted will sit nose down. On a big river being deeper at the front doesn’t matter much. On our shallow muddy ditches it is better to have the draft at the bow much less than the draft at the stern, amongst other things it makes it easier to wind in shallow waters and easier to steer. Never tried it but I’m confident that a fully loaded narrowboat is fine on a deep canal / river, and a bit of a pig on a shallow canal.

 

That said a very lightly ballasted bow will tend to get blown sideways by the wind, so as with all things the middle path is best.

A fully loaded working narrowboat has to trim level, because it'll only have about 6" of freeboard all round (see the coal boat photos!) and draw about 3'6" of water, you don't want any part to be deeper than any other to reduce risk of grounding. So when unloaded they float massively bow high because the load is towards the bow and the engine/cabin towards the stern.

 

A 72' narrowboat that draws 3'6" level when fully loaded (15 ton boat + 25 ton load) will only draw 16" average when unloaded, which probably means about  22"-24" at the stern and 10"-8" at the bows depending on swim/prop size. So this would be trimmed up at the bows by between 12" and 16". When half-loaded (if we take this as typical) it would be trimmed up at the bows by 6" to 8", maybe this is the look that modern boats go for as being "normal"?

 

A typical modern 18 ton 57' narrowboat will draw about 22" if trimmed level, and since this is also the typical swim depth it needs to be ballasted so it's normally at least a couple of inches down at the stern to keep the swim underwater when the bow water tank is full and the stern fuel tank is empty. Being trimmed only a few inches off level like this should be better for both grounding and boat handling than the more bow-high trim that is common, several people have said that their boat handles better when trimmed closer to level.

 

If the boat is heavier and deeper-draught or has a deeper swim/bigger prop (which I think might be the case for nicknorman?) then a more bow-up trim could be better.

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