Why exactly does it sink?

[Tam & Di]

That is true - you load motor boats in particular slightly down by the head which gives them much better steerage apart from anything else. I ballasted our 24m Dutch barge we cruise in continental Europe in that way too, but the downside for most people will be that the vessel is a lot less lively.; it will be rather heavier to steer, and will burn more fuel.

 

Another thing for mark_j to think on is a mud hopper will remain afloat even when full of wet dredgings which can be higher than the water it floats in - all because the bow and stern sections are watertight (and also along each side if it is truly hoppered). But people mostly want maximum accommodation - they're looking at the inside rather than the 'boatabilty' of what they have - that's why there are so many ghastly repro barges built for example.

 

Tam

[Tony Brooks]

12 hours ago, mark_j said:

Thanks TheBiscuits. My question is more fundamental but you raise an excellent point.

 

In your comment the subversion of the air vents floods the engine bay... but then what? What from there is causing the whole boat to sink. That's the bit I'm trying to understand.

 

 

You have to have access to the cabin area and that means to allow access to the cabin the effective height of the front and back bulkheads will be reduced by what it requires for a person to get into and out of the boat. In effect the front doors will give an effective front bulkhead height of maybe 2ft for  a self draining cockpit or less for a not self draining one. Similar applies to the rear bulkhead where, depending upon the design the effective bulkhead height could be perhaps 18" to 30" with the latter much more difficult to get in and out of.

 

Once the water in either end of the boat exceeds those measurements its only the doors that are stopping it flooding the accommodation so I suppose you could fit seagoing water tight doors.

 

The water can build up above the well deck floor or aft cockpit floor and leak into the accommodation before the bilge below is anything like full but with modern self draining designs this is a LITTLE less likely. The main way it occurs is shipping a large wave over the bow but from what I can see narrowboats tend to split the wave so most passes either side or from lack of attention in leaking locks where large volumes of water can be poured into the well deck or onto the aft cockpit from gate pedals. Then there is the question about hanging boats up on lock cills and that has the potential to sink  almost any boat in a deep lock if its not noticed and quickly rectified.

 

 

Once water gets above this level all

[WotEver]

2 minutes ago, Tony Brooks said:

Once water gets above this level all

... bets are off?

[Bee]

Many ways to sink a boat, mostly getting the back of the boat sat on the cill whilst the lock empties (I've never done that) getting the front of the boat on the cill whilst going down a lock backwards (I've done that, realised in time though) getting hung up in a lock (twice, realised in time though) Going down in a Thames lock alongside a bigger boat, the lock tapered and we got jammed together (easily cured)  Going up in a lock and a baulk of timber got jammed between the boat and the wall (saw it in time) and with an old wooden joey boat, big piece of ply in lock, edge went through rotten plank, again realised in time, bottom rudder pintle on front of steel joey boat hooked up on something going up in a lock, only just realised and last but not least, somewhere in France tied against a high wall, huge cloudburst and a drain that drained an entire car park discharged huge volume of water into the canal, we were not tied under it but that would have overwhelmed many small boats.  OK, not all of those were going to end badly but you see the possibilities, and that's without frost damage, rust, rivets and the rest. In fact I've frightened myself now.

[mark_j]

54 minutes ago, Tam & Di said:

That is true - you load motor boats in particular slightly down by the head which gives them much better steerage apart from anything else. I ballasted our 24m Dutch barge we cruise in continental Europe in that way too, but the downside for most people will be that the vessel is a lot less lively.; it will be rather heavier to steer, and will burn more fuel.

 

Another thing for mark_j to think on is a mud hopper will remain afloat even when full of wet dredgings which can be higher than the water it floats in - all because the bow and stern sections are watertight (and also along each side if it is truly hoppered). But people mostly want maximum accommodation - they're looking at the inside rather than the 'boatabilty' of what they have - that's why there are so many ghastly repro barges built for example.

 

Tam

A mud hopper? Here I admit my ignorance:)

[matty40s]

Edited August 23, 2020 by matty40s

[Tam & Di]

An unpowered craft designed to carry dredging spoil. In effect you can imagine an enormous skip dropped into a steel hull, with decking welded from the skip to the top of the hull and leaving a watertight space between the hull and the skip. All I was trying to say is that if the accommodation is sealed and you have sufficient space fore and aft to support the weight, the vessel cannot sink. Just a practical demonstration of the Archimedes Principle.

 

Tam

Edited August 23, 2020 by Tam & Di

[Big Bob W]

39 minutes ago, Bee said:

In fact I've frightened myself now.

I'm going to have a quick drive over to the boat just to check its still afloat.

[Tam & Di]

Bee's post is probably the most relevant in this thread, especially in conjunction with Tony's. You can make your boat as unsinkable as you may, but inexperience, inattention to the job in hand at locks, acts of god - they're the major contributing factor to most sinkings.

 

Tam

[Scholar Gypsy]

Is there a record for attaching tags to a post? This one has twenty. (I do admit I never use them).

[LadyG]

22 hours ago, Tracy D'arth said:

Practically every narrowboat is floating bow high all the time.

Look at a loaded working boat and the bow is lower than the stern. But live in and leisure boats are technically near fully loaded too, yet they ballast them bow light.

So the addition of weight or lack of buoyancy at the stern has a dramatic effect on the trim.

A bit off topic, but I was considering blocking the gas drain holes in my f'ard locker next time I am on the Trent, that would prevent water being driven in if things got choppy?

 

Re trim, my boat has no ballast in bow [don't let's go in to that now], trim is level longitudinally, my chain, anchor, gas botles and water tank must be helping.

Edited August 24, 2020 by LadyG

[Scholar Gypsy]

4 minutes ago, LadyG said:

A bit off topic, but I was considering blocking the gas drain holes in my f'ard locker next time I am on the Trent, that would prevent water being driven in if things got choppy?

Would also stop any gas leaks getting out.
It's quite normal for gas lockers to get some water in on rough water, and it drains out again.

You can't see the gas locker drains on this video, but you can see the foredeck drains working hard. 
 

 

[DHutch]

10 hours ago, Scholar Gypsy said:

You can't see the gas locker drains on this video, but you can see the foredeck drains working hard. 

Going some!

On 22/08/2020 at 21:19, Tony Brooks said:

Not all boats have a sealed back bulkhead...

I would go as far as to say most dont?

 

Daniel

[ditchcrawler]

On 23/08/2020 at 12:07, Scholar Gypsy said:

Is there a record for attaching tags to a post? This one has twenty. (I do admit I never use them).

What do attaching Tags achieve on this groupe?

[LadyG]

9 minutes ago, ditchcrawler said:

What do attaching Tags achieve on this groupe?

 

[Jim Riley]

24 minutes ago, LadyG said:

 

In a canal near you? Going in to clear the prop?