High Speed Narrowboat

Discussion in 'Boat Design' started by Nick Ireland, May 21, 2003.

  1. Nick Ireland
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    Nick Ireland New Member

    Does anyone have information on a suitable design for a high speed boat with low wash suitable for carrying passengers on a canal? Maximum dimensions would be 6ft 10" wide by 70ft long.
     
  2. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Nick - define "high speed". Comapred to _other_ narrowboats or do you want to plane?
    Are there not actual speed limits on most of the canals, regardless of wash created?
    Steve
     
  3. badges65
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    badges65 Junior Member

    Hi Nick,
    thats a very long boat for its beam!!!
    a variation of the IVB will give you a hull with no BOW WAVE and reduced wash, I would be looking a a version similar to willinghoff's version but with our chine version .
    don
     
  4. CDBarry
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    CDBarry Senior Member

    Critical speed

    You need to look into the issue of critical and super critical speed.

    Wave celerity is a function of water depth and both resistance and generated wash are very sensitive to the hydraulics of the canal itself. There is a magic speed that is very easy to acheive, a sort of "sound barrier" which is hard to overcome and then another regime of speed which is easier.

    This is a very high tech topic that is the subject of significant work in hydrodynamics texts, and more recently some fast craft symposia (Fast '99, Fast 2001, etc.) and you should research it carefully.
     
  5. Nick Ireland
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    Nick Ireland New Member

    Many thanks for your responses. There is a speed limit on the canals of 4mph. We are exploring the idea of a specially licenced boat which would be capable of 10-12 mph. It would run on a relatively straight section of canal and might be restricted to certain times. Horse drawn passenger boats (called fly-boats) ran in the 19th century reportedly at an average of 10mph.

    The dimensions of the boat are the limits of what can go through a lock. There are routes that a wider boat could undertake.
     
  6. Guest

    Guest Guest

    In fact it is exactly these fly-boats that led Froude to formulatng the mathematics that gave an understanding of the hydrodynamics of waves, both in general, and in channels, in the 1800s.

    They operated at the critical speed for the canal, and since it is bounded on both sides, wave energy could not be radiated away and they travelled with the wave they generated with little losses and very low drag. They essentially surfed on their own wave.

    They do, however, produce a very substantial wave.

    From a viewpoint of channel erosion, you have to examine the components of the wave. It is mainly transverse flow that causes erosion.

    Again there is currently a good bit of research in this matter. Since you are in the UK, it would probably be worth going to the RINA library in London and generally contacting them for recommendations as to experts in this area. It is a few blocks from Victoria station.
     
  7. Peter_T
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    Peter_T Junior Member

    A long but narrow boat configuration resembles to the canal canoes or the dragon boats. But beware that the beam reduction must not be approached to the critical slim form as to hinder stabiltiy. The first approach is to ensure that, there is adequate stabilty so that all persons onboard with gear can stand up on the deck. In the case of the racing canoes, some requires that the operators to be in the sit down position. The next step is to check on freeboard to ensure that the boats can roll over a certain angle with good residual stability. In simple terms, the boat must be able to handle dynamic roll, that doubles that of the static heel caused by wind, steering or offseting passenger. Also account for dynamic stability to resist rolling angles caused by the passing boats or rolling in the unresisted ambient wave condiions. Moderately increasing the beam and depth will solve these problems.

    Your quoted inland navigation speed was so low about 5 mph i.e. like 4 knots. Most cities will limit to about 8 to 10 knots. Wave wash is a critical matter. In Germany wave wash effects and craft design restrictions are under review and some serious research efforts have been made. Their speed limit is in the higher speed range and they are investigating high speed craft limits.

    At this point, it is hard to proposed on a suitable hull form, without knowing what is the canal sectional dimensions: e.g. mean width, mean depth or critical depth. You see the canal effect on a craft may be closely related to model testing in a basin. A large model tested in a small basin will have shallow water effect, generating deep and short waves. Powering boats in shallow waters, spend more energy to run at the desired speed compared with the condition in deep water region, before entering the canal.

    Canals are usually depth restricted, so only multi-displacement hulls will run properly in comparison with the mono hull. A flat bottom boat will restrict the water flow near the river bed, thus creating shallow water waves and vibration.

    If you look at the market of pleasure boats, there is a trend of twin pontoon platform boats. These boats will best suit the operation in the wave wash ban area. However, these boats are usually in round pontoon with conical bow, but are economically blunt ended. They also lack reserve buoyancy one the water wash over the top of the pontoon. If you get both ends of the pontoons in faired ended so that the bow breaks in the water set up some wave, the stream can flow smoothy to the stern with setting another train of large divergent wave due to blunt stern end.

    The simple trick in breaking the wave size is to reduce the beam and provide a small angle of entrance and ensure good stern streamline shape. The modern idea is to subdivide the hull to two or three parts, the wave effects will be lessen, even after adding up the effects from the number of pontoons involved in supporting floatation. Increasing length is a prime improvement in lowering the wave effect.

    From the web, there is a 4 mph limit:
    http://www.murray-river.net/boating/pwc/default.htm

    This limit protect the envirnoment, but limit in boat construction.

    Now look at another fast ferry speed limit:
    http://www.marlborough.govt.nz/harbour/fastferries_main.asp

    Peter
     
  8. philwhittaker
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    philwhittaker Junior Member

    There ia an outfit in san diego that has patented a design called the M hull. It is used in cannals in venice for passanger craft and is designed specificly to reduce the wake while keeping the passanger volume.
     
  9. Peter_T
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    Peter_T Junior Member

    Thanks for leading to the M hull. An impressive hull form using two tunnels, carried all the way aft. So it is in fact a trimaran, except that there is no air gap to enable her to ride in rough waters. Unless, it is using activated air cushion.

    http://www.aeromarineresearch.com/history.html

    I don't suppose the Venice authority will allow them to run at automobile speed along side the traditional Gondolas. A low speed, much more power will be needed due nearly doubling the wetted surface.
     
  10. Guest

    Guest Guest

    The canal is approximately 10m wide and 1.2m or more deep. It is brick lined both sides on the main route we are looking at. Generally the channel is deeper in the middle and may be shallower at the edges.

    Is a multi-hull design feasible for a 7ft wide boat of this length? Passenger space may also be an issue. A traditional narrowboat has very little spare headroom and greater height on the boat would restrict areas of use.

    Many thanks for all your comments

    Nick
     
  11. Peter_T
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    Peter_T Junior Member

    For such a shallow chanel of 1.2 m or 4 ft, it will be necessary to limit the boat draft to 0.6m or 2 ft. Shallow water effect will come in. To copy the Venice situation, one can make a catamaran with two gondolas. Their streamline hull is ideal for the channel transit, with the least wave wash effect.

    A similar situation is in the polynesian culture village HI, there are lots of catamaran boats for supporting folk dance shows and for visiting folks. They are great platforms and can be outfitted with outboard motors.

    Peter
     
  12. SailDesign
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    SailDesign Old Phart! Stay upwind..

    If memory serves me, the maximum "air draft" on a canal is about 2m. This would mean that when the boat is _empty_, it can only be 2m tall, and obviously water draft is limited when the boat is full. That would, as the OP says, leave little headroom. In a multihull as Peter_T describes, it would not even leave much more than sitting headroom.
    Steve
     
  13. jimburden
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    jimburden Junior Member

    Air ride or SES bottom hull

    It is possible to reduce the friction of a long narrow boat slightly by making a pocket under the hull to hold compressed air. Dividing into quadrants thith a center sealed keel and flap separation helps with stability. In low waves and lower speeds this might reduce power requirements. A narrow boat I thought in England were minimally eight feet wide. At any rate a boat could have fool out cabin sides and a tent or awning extensions to increase the living width and head room, for comfort in non-size restricted areas.
     
  14. tom28571
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    tom28571 Senior Member

    No matter how it is sliced, this will be a displacement boat. You simply can't push a boat of any significant displacement through the narrow canals of the UK without making waves. This will be the case no matter how it is supported by whatever the hull shape. Any form of multihull makes no sense where the BOA is limited to less than 7' by the locks. Supporting the boat by air or whatever at these speeds does not reduce displacement. HOA is also strictly limited by tunnels and bridges.

    The boat occupies a very large fraction of the canal cross section and most canals I have been on are much less than 30M in width. Therefore there will be a large bow wave and I don't see any way to avoid that. By reducing the displacement to a very low level (extremely low bottom loading), it can be done. But then, you don't have any carrying capacity.

    In many of the canals, including the Warwickshire near Birmingham, running more than the 4mph limit makes for bank overwash that is devastating to the area. Meeting or passing other moored boats requires that speed be reduced to near idle to avoid being screamed at.
     

  15. jimburden
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    jimburden Junior Member

    Making the boat as light as possible is the first step to reduce the wake in a boat of fixed length and cross section. I have probably looked at around 2000 to 3000 canal boats for sale on the internet of all kinds. Not having the common bath tub bow and stern but a truly elongated entry and exit angle is needed to reduce the wash. A inside tapered catamaran can force an immediate bow wake to the inside rising between the two hulls. This center wake rise will push under the hulls over at least half of the length of the hull probably reducing the wave height to a more gentile rise instead of the typical steep wave contour at the proposed higher speed. This combining all of these light weight for small displacement per unit of cross section, longer bow and stern inside tapers and internal possibly a swath catamaran hull with an inside bulge and flat outsides might delay any steep bow waves, making it more a bulge in water level amidships. An inflated lay flat large diamer discharge hose could raise the cabin bottom out of the water to acomodate this centralized wake, then be deflated to lower the cabin into the water to reduce cabin heigth for tunnels. A raising cabin roof and motor home like slide outs can increase the cabin width outside of beam restricted areas. Another possibility I reciently saw is fold over hull extensions that can straddel a tapered cabin section in the bow and stern. This could lengthen the underwater hulls a good ten feet on each end hydraulicly moved or using a high torque electric motor bring both ends over to form a shorter boat in the locks. All of this is irregular but some combination might allow radical low wake speed improvements. I love long narrow boats as they use less energy per ton or unit of cabin volume. This could be an all electric solar boat. I am looking at using 16 inch PVC irrigation pipe to make pontoons in various boats because the material is $20 a foot, flexible, fairly tough and can be foam filled to increase the strength and make the pontoons unsinkable. Two of these 70 foot tube with 10 foot one way tapers on each end foam filled to be unsinkable would weight under about 1,300 pounds with swath attachments and displace about 12,000 pounds. An additional lay-flat 12 inch dia. discharge hose inflated inside each side wouid add about 2500 pounds of displacement. This boat might draw about 2 feet of water raised up and about 40 inches lowered to float the center cabin bottom. Larger diameter tubes could also be use. It is not hard to build a plastic composite foam cabin that has a composting head, a grey water evaporator, an RO water maker and light weight interior components to meet this weight goal.
     
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