Richardw's Narrow Boat Project -BILGE AND BALLAST

That's not a narrow boat. Much too wide and too high. Nice looking boat though.

 

Didn't say it was a Narrow boat.

Poster asked about ballast, and what its for; this was one solution on a similar type of boat.

 

A design must fit within it's general perimeters, so one that's too long or too beamy is just frivolous, if not foolish. The same would be true of draft requirements and all the other elements, including reasonable ergonomics and air draft. I don't see where the issue are, given an intelligent look at the SOR perimeters and typical engineering approaches. Are they going to cause some head scratching, of course, but any reasonable designer should be able to overcome these hurtles and develop a reasonable set of plans. I couldn't say the same about a novice designer using FreeShip or similar.

 

I expect "any reasonable designer", after understanding the fundamental constraints on narrow boat design, would come to the conclusion that a narrow boat with standing headroom inside the cabin will need to have a draft significantly deeper than the draft which results without added ballast, considerably oversized scantlings or similar. And I would expect the same reasonable designer, after understanding the fundamental constraints on narrow boat design including those they may not have encountered before, not to dismiss the use of fixed ballast in a narrow boat as an indication of a poor design or a mistake by the designer, but rather as one logical way to meet the SOR in a cost effective manner.

To be fair to the other contributors to this thread I'll note that by simply reading the first post, not realizing the significance of "Narrow Boat" in the thread's title, not having read the original posters previous thread which he refered to which has a first paragraph of

My name is Richard Wilkinson, I am a new member but I have been visiting this site the past few months harvesting information because I am embarking on a project of designing a new 62ft Live Aboard Narrow Boat.​

and not having noted Richard's location of Rugby/London which implies England, the context of Richard's question would be easily missed.

 

Without a bilge your sink, shower and toilet will have to drain uphill.

Without a bilge , the several tons of liquid will have to be stored on your bed.

You would be best advised to choose an existing hull shape...study the shape , study the concept, then begin your concept. The shape that AdHoc posted is ideal.

Study your cruising grounds...air height, dock height, avaible winter berths, available shipyards for haulout...then customize your concept to match with the facilites.

The whole reason for a custom build is the abilty to highly detail the design so that its form and function perfecly matches your needs

 

Internal ballast and steel boats are a bad combination.

To achieve maximum service life with a steel hull you must have perfectly clean, dry bilges and the ability to inspect the steel plates.

Internal ballast is a mess and it steals precious internal volume. External lead ballast is the way to go. This lead shoe also acts as a strike plate to keep the ships keel from being damaged in grounding or at the shipyard during maintenance

 

it would be better to make it a wide boat ,14 ft not 7 ft

 

Why is that ? Berthing?

 

I thought these vessels had to fit within a box formula to deal with passing & locks & tunnels, ?6'10" wide by about 68-70 foot long, I've never been to the area but arn't the canals from the past & figuratively the trucking highways of old England & the narrow boats the semi trailers...

Jeff.

 

David, we probably agree on most points, but my issue is you design to the parameters and if you have a shape that hits all the marks, but is too shallow, you don't add ballast, but you do reduce design volume. Since it's a canal boat, it'll draw more than a more conventional craft of similar length. I still don't see the need for very much ballast on this type of vessel, given it's build material and other considerations.

The general SOR restraints will require a pretty stiff bilged puppy, so stability isn't going to be affected by ballast and the additional weight, other then trim, is detrimental to a limited draft, narrow waterplane design. My point is I think a 9:1 beam/length ratio design can be designed to hit it's marks, with a few inches in either direction, for loading conditions and without ballast (other than trimming). Again assuming what we've learned about this design and it's restraints.

 

There were definitely working barges in the UK in the 1970s' probably into the 80s. I lived in Walton on Thames and there was a corn mill in Addlestone on the Wey Navigation that used barges. Also a small ammount of coal was carried. Used to see them on the Thames, both tidal and non tidal.

Of course property prices saw the mill converted to flats, after all transport to/from it had changed to road. Along with the demise of other local industry including low speed propellors, and now we have no UK owned wind turbine manufacturers. At the time I worked building rowing shells and Planning permission for a new workshop was refused on the grounds it would cause employment and bring people into the area!.

In Europe they are still in major use. An example is that Schipol airport in Holland (Amsterdam) is 'fed' aviation fuel from Rotterdam via large fuel carrier barges. Many are around 1,000 ton carry load. The waterways are much larger than in the UK. If the UK infrastructure supported these large barges it would still be used commercially.

The UK infrastucture restricts the design inside a specific 'box' anything larger will not be able to navigate the full network.

My take on the hull would probably be a bit of both, ballast and playing with the hull volume and scantlings to get enough headroom and accomodation. As it is not a conversion using a traditional long 'box' quite a few things could be done that are beneficial to such a design. At 62' there is a fair bit of 'leeway' in the design without compromising stability or pitching loads yet could result in a far superior craft. Some of the benefits I outline in the other thread on this craft.

Nice one Ad Hoc, would be interesting to see a set of sections or waterlines, looks very commodious and of course has the benefit of being a little larger.

 

Looks good, looks build able

How much rocker does a canal boat carry?

 

I would say there is no rocker in general, but there is stern relief for the prop and the stern hung rudder. In plan the sterns are commonly a full radius ie half circle above waterline. Remember a lot of the older boats were horse drawn not self powered. It was all max load least size, with living
accomodation at stern.

In fact it was a requirement on the tidal Thames to keep tree growth on the banks to nil to allow for horses. Ownership of the banks changed around 1980 and the local councils took over. They let the trees grow as no more horse drawn boats and now the banks are collapsing and they are moaning about the cost of repair...

That is also why you can play with the volume, both ends as this is a new build and not based on cargo maximisation. The main thing for out of trim is probably that in most conversions almost everyone is at the stern when travelling. In good weather they will be outside, mainly to get away from the noise of the near universal diesel engine. Of course a diesel in a tin can is not the quietest combination....

Main requirement is ability to be 'beached' or dry docked. Former could be supported anywhere but most waterways (canals) would be fine so loading not a real problem. Prop guarding or allowance for out of trim grounding should be borne in mind. Above waterline it needs to be sufficiently robust to accomodate being hit by other narrow boats. I believe the general speed limit on the Waterways is 4kn but there are plenty of rivers and other parts where this is higher up to 7-8kn.

Thanks for the sections Ad Hoc, very interesting. Nice curve in bow plates probably to give a straight waterline entry and relief at stern for propulsion stuff. Far superior entry compared to a narrow boat, which might benefit more from a rocker rise towards the stern whilst remaining relatively flat athwartships.

 

waikikin, some clown 200 years ago built a few locks 7 ft wide, so the idea was that all boats must be that wide to pass from london to the north, which few of them did, hence the narrowboat,

but in a survey in waterways world, 93 % of narrowboat owners preferred marmite on toast and 14 ft beam