110 ft High Speed Passenger boat

Discussion in 'Boat Design' started by captaincuda, Aug 4, 2013.

  1. captaincuda
    Joined: Aug 2013
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    Location: Cape May, NJ

    captaincuda New Member


    I am new to the forum, though I have been reading for months.

    I am a tour boat operator with an interest in building an all new tour boat.

    The vessel to be constructed will be built out of aluminum.

    My preliminary plans for power are four Cummins QSK19 800 HP Diesels
    or four John Deere 650 HP Diesels. Four Shafts, Four Props.

    The vessel will most likely be a monohull, though I have considered a catamaran for space issues and stability at rest. It will be a double deck boat with upper pilot house and main deck walk around cabin.

    My ongoing debate is whether to go monohull or catamaran. I know the build will be more costly, two of everything. In initial talks with designers, my plan of using four engines becomes difficult to get good prop clearance. Some other issues I have with catamarans is freeboard height forward and inside the tunnels. We routinely experience 6ft plus wave heights. Low tunnel freeboard can lead to poor ride at slow speed.

    We have great experience with monohull tour boats

    We own a 1970 110ft X23ft Camcraft, all aluminum, certified for 300 passengers, powered by four DD 892N 400HP diesels. Top speed 24 knots
    Also, a 1986 110ft X 28ft Aluminum Boats Inc, certified for 400 passengers, powered by three Cummins KTA19 700HP diesels. Top Speed 22 Knots.

    The boats are like new in many regards, but we are moving towards an all new boat with some new ideas.

    Speed of a large catamaran comes into question with the four propellers vs higher horsepower jet variants. If a catamaran, hull form seems to be key, as semi-displacement vs planing seems to be an interesting idea, but I do not know what it all means. Shallow draft is also important. I also imagine hull width, and physical weight of the boat play into the ability of a high speed catamaran of these dimensions.

    Ideal dimensions for a monohull vessel 125ft X26ft
    Ideal Catamaran Dimensions 110ft X32ft

    This is where I hope some designers on the forum can steer me. This is a big expensive undertaking and I would like to hear some thoughts and analyzing before I start writing checks.

    Thanks in advance for any light you can shed on the subject.
  2. dskira

    dskira Previous Member

    It can be a very interesting thread due to the experience of captaincuda.
    It is not often we have a demand for design assistance coming from a knowledgeable source. It is more often coming from a dreamer with a computer, this time it comes from someone who can also teach us something about the operation of such a vessel.
    Unfortunately I can't contribute since I have not enough knowledge on high speed vessel design.
    But I am sure a lot of members have experience in that field, and will be glad to jump in.
  3. keysdisease
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    keysdisease Senior Member

    Why four engines instead of two higher HP engines? I would think on a 100' prox boat four will be problematic for a variety of reasons, especially a cat. Plus all the extra drag from the 4 x u/w gear. :confused:
  4. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Hi, welcome to the forum :)

    You have several issues to address:
    1) Legislation
    2) Power/speed
    3) Seakeeping
    4) Layout

    1) I know in the US you have the silly subchapter K and T rules which ends up dictating the amount of crew onboard. If that is put to one side for a second. As anywhere else, this would be flagged as a HSC Code boat. As such, stability will be the first main issue. Monohulls experience difficulty passing the current HSC 2000 code rules. They can be made to pass, but on smaller mono’s it is more difficult.

    The damage stability with the raking damage length of 55% from the bow and the 35% anywhere cause serious problems with the amount of trim, it ends up being over the maximum allowed. Coupled to that, in order to make it pass, the hull form has more freeboard. This inevitably raises the VCG, which reduces the intact and damage stability. Thus you make the hull wider, which adds weight and slows the boat down and playing into #3, increases motions.

    If you do build to the HSC code, it also adds to your resale value, since it shall be able to be sold to anyone anywhere in the world. We had a 30m cat built in the US in the late 90s, to the HSC code, which was rare then. It was later sold just a few years ago, easily, to a UK operator owing to its HSC code compliance.

    2) Whether you end up with 300 or 400 passenger, the Froude number that your boat shall run at is roughly (depending upon the final dimensions selected) at the lower end of the “ideal” of that for a catamaran. The boat will be a displacement boat; do not be fooled by someone suggesting a semi-planning cat or otherwise. As a displacement catamaran at the circa Fn of 0.8+ will have approximately 50% less power requirements of that of a similar/displacement size monohull. This should not be ignored. A catamaran also is significantly easier to pass the HSC 2000 code damage stability rules too, without any undue influence on the whole vessel.

    Having redundancy i.e. 4 x engs/jets/props is much easier on a cat than on a mono. A monohull would end up being a semi-displacement hull at the speed range, which means you shall have more buoyancy aft as the lines alter to suit the speed range. However this also causes a lot of transom drag and thus you’ll need to check against the power requirements and going over the main hump, can you get over the hump? And if poorly designed subject to large variations in trim in various conditions of loading, if it has a poor layout, subject to that in #1 and #4. If you reduce the transom immersion, it helps in seakeeping and also better resistance. Trouble is, this pushes the engine room fwd and makes the layout more complicated on such a short boat, especially the location of the passengers. As such, it may be a bit more difficult to arrange the shaft lines with 4 engs, especially the outer engines as there shall be a bilge radius squeezing the width available. (Same with a chine boat too). So a mono may need some investigations earlier on in the prelim design phase.

    3) This is a short length hull circa 30m and will displace circa 110-120tonne. This means the length – displacement ratio will be around 6.2-ish, which is a bit low. However, for a monohull to be “superior” it requires a high L/B ratio. This falls foul of #1, HSC code and damage stability. Thus making a monohull ‘pass’ shall reduce the seakeeping superiority of a mono to that close to that of the catamaran as the L/B ratio reduces. Mono’s are in general always better in motions, but there does come the law of diminishing returns. Also what is your area of operation, rough coast line, or smooth rives/lakes etc?

    We have several 200pax vessel of this size all running in coastal waters. Their seakeeping is rather good principally because of the prevailing wind/wave conditions and being catamarans, we were able to manipulate the hulls to provide better seakeeping than a standard cat. Why, because stability isn’t really so much of an issue with 2 hulls separated apart. The only aspect shall be the accelerations. Thus you really need an analysis of the sea of where you plan to operate to ensure it does not cause a concern, for either hull form. There are some very good motion control suppliers out there to improve the motions of a catamaran, if the ‘naked’ hull is poor and/or the prevailing sea states are deleterious.

    4) The above 1-3 ends up dictating your layout. It is possible to have a single deck cat of 300pax, I’ve just designed one, and running at your speed range too. It is not possible to have a single deck (which also helps evacuation and crewing) on a monohull; on such a length of vessel it will inevitably 2 or possibly 3 decks, owing to the damage stability requirements and buoyancy that is required. The hulls are essentially empty voids. Which on a cat isn’t a problem but on a mono, there is the desire to place the passengers down below. But owing to HSC code you can’t, it’ll fail. So more decks on a mono, which of courses raises the VCG again, the usual spiral of events downward. The principal thing to ensure is evacuation and safety of the passengers that is your prime objective. It is much easier to evacuate 300+ passengers on a catamaran than a monohull of the size range you’re quoting.

    Finally, getting the egines out for maintenance. On a mono, you have to remove the passenger saloon decks above. On a cat, if well designed, is is directly through the main deck hatches, as these are located away from the main saloon. Much easier.

    So, just some food for thought.
  5. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Four engines does seem unusual, maybe the OP can explain the reason for specifying that number. It is certainly an "unlucky" number in some Asian countries ! :D
  6. BMcF
    Joined: Mar 2007
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    BMcF Senior Member

    Four engines vice two actually isn't that unusual...ServoGear has been supplying, for quite a number of years, CP drive packages that combine two smaller diesels on one drive unit.


    We were involved in the repower of an older passenger cat a couple of years ago and the original MTU/KAMeWa power ( 2 off) was replaced with four Cummins diesels connected to Hamilton jets.

    I'm pretty sure that the Cummins installation was significantly lower cost than the cost of replacing the original system 1:1, but the operator was also concerned about achieving a higher degree of reliability with increased propulsion redundancy.
  7. captaincuda
    Joined: Aug 2013
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    Location: Cape May, NJ

    captaincuda New Member

    Four engines vs two engines.

    I have been operating passenger vessels for 20 years. My father has been operating passenger vessels for 40 years.

    Four engines is our ideal situation for several reasons.
    1. Obviously, redundancy is a huge factor. On a monohull, when you lose one of your two engines, for an inexperienced to moderate experienced captain, docking and controlling the boat becomes almost impossible. Safely returning to dock is difficult for a seasoned and experienced captain. With a four engine boat, the chance of being down to one engine ever is almost impossible, thus, you can always get home, safely, without help from anyone.
    2. Smaller engines depending on the engines chosen are simpler engines. Compare a John Deere 6125 to a MTU 4000 series. You guys who want to keep using these huge horsepower engines think nothing about the maintenance schedules and the amount of labor for overhauls and the limited running time of such complicated beasts. The expense of these performance engines is nothing short of ridiculous. I know boats that run 4000 series MTUs. There is an engine out of the boat, every year for rebuild. The down time is something I am not willing to sacrifice to run my company. It is a burdensome and superfluous expense. Specifying Cat, MTU, or Deutz are recommendations made by designers and not by mechanics or managers. These engines are nightmares when it comes to longevity. Me personally I really like the Cummins KTA19. Bullet Proof Simplicity and I know guys with 40,000 hours with no rebuilds. That is a commercial engine.
    3. Fuel Burns. The first words out of everyones mouth when I say I run a boat with four engines is wow that must burn a lot of fuel. Well. Lets look at my boat, the Cape May Whale Watcher. 98 Feet Registered length. 23 Feet Wide. Four 892N 400 HP Diesels plus a 20 KW Generator Running. Holds 300 Passengers. Typical trip, we have 150-175 passengers aboard. We run slow, at 1450 RPM, around 13 knots for average trip and burn 26 GPH, total. We can hook her up at 1850 RPMS, moving 18 knots and burn 40 GPH Total. Please tell me some other boats with two engines, traveling at 18 knots plus, buring 40 GPH total? Im told that the old 2 cylce detroits are the most inefficient terrible engines ever, even though ours have 16000 hours and when we checked compression recently they 550 psi, which is about 50 better than when they were new. That having been said, if we were running new Tier II tech, the fuel burns would be even lower.
    Yes, this is not nessecarily high speed. Part of my problem is we need to go faster. However, I feel the four engines is still very important to us.
    4. The helper effect. Fuel burns being equal is not a fair assessment of a four engine boat. You fail to take into account the helper effect of a multi-engine boat. What is the helper effect? Lets say we are running two engines at 1200 RPM and the other two in neutral. Put the other two in forward and you will see a slight increase in the engines RPM. Bring the other two up to the 1200 RPM mark and now the other engines that were at 1200 RPM are now operating at 1300 RPM. The additional engines reduce engine load on each other, thus helping the other engines.
    5. Crewboats. Twin engine seems like the way to go, as long as you are not a crewboat designer. Look at companies like Gulf Craft, Breaux Bay Craft, Breaux Brothers, Neuville, etc. These companies have been building all aluminum boats since the 1960s. They started with twin screw boats, and very soon went to building three, four, five, and even six engines boats. These are boats that run round the clock on schedule at speed. It may not be high speed, only 20-25 knots. But if anyone knows something about multi-engine configurations, these companies are the masters.

    That having been said, these are not catamarans. That is why I am here for the advice on catamarans.

    So far as K boats, I own two so I know a thing or two about K boats. T-boats are a cake walk and I have owned them in the past. Do not let these laws affect our design discussion. I have lots of experience with the laws, including the new laws and I work with the Passenger Vessel Association on the new laws for fireloads etc. The USCG would like to work with an individual on the new laws, but everyone is too busy running scared right now to do so.
  8. Ad Hoc
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    Ad Hoc Naval Architect

    Then you shall have to define your SOR in a bit more detail for further advice.

    Can you explain this further? Since the HSC code is all they should be looking at. Unless they wish to develop their own local rules for some reason?
  9. keysdisease
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    keysdisease Senior Member

    Great answers. My company supplies several systems to some of the crew boat / OSV quad engined monohull manufacturers on the Gulf, I just wasn't sure if the economies held true for a 100' cat as the do for those larger OSV's.

    I get a kick out of one of the leading designers of those monohull OSV's being Crowther, a designer with multihull roots.

  10. april15th
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    april15th Junior Member

    Hey Captaincuda,
    I read your post and wanted to know an answer myself. So I emailed your question to Steve French, founder of Applied Concepts Unleashed. Applied Concepts has over 1500 successful boats on the water so I figured he’d be a good place to start. This was his reply, hope it helps.

    “I think your points on four engines are solid.

    There have been successful four engine cat configurations for decades and several with jet drives. Multi-hulls have presented a great solution for many builders around the world as they have a different culture and tolerance for change than the USA. Boats like the Devil Cat (InCat), Condor (Alum. Shipbuilders) and many in Australia & Asia are powered by four engines. While the scale is different the principals remain the same. A trip to one of these boats for a ride and a talk with the captain would be well worth your time. A monohull is something you know can be done, but I think you’ll find a cat to be a smart business decision if done correctly.

    Bottom line here is that your family has business needs combined with experience that should dictate the type of vessel that you end up with. To assure that your money is spent on something that you will be happy with and operates within budget for your business requires a little research up front. Perhaps begin with a complete wish list of feature and performance goals. You can do it or work with a professional that respects your experience and doesn’t try to steer you towards something they think is best. You will discover that the answer to questions like which hull will be best answer themselves easily through the design process.

    There are many amazing boats that have been built over the last 30 years that are for sight seeing and for the numbers of people that you carry. I suggest spending some time finding examples of what you like and don’t like and compiling a catalog. From there you can steer the design and the build right down the center of what you want. If you would like, give me a call. I would be happy to discuss this further with you.

    Steve French
  11. Ad Hoc
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    Ad Hoc Naval Architect


    Have you come to any initial thoughts/conclusions yet?
  12. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Why are Cummings less complex than 2stroke MTU?

    If they are better, why is anyone using other brands? Are the others "hotter" motors and more hp/weight?

    Is it the engines only that break down? How about 4 engines with two driving 2 props so you can cruise at 1/2 or full power without lugging engines?

    How about the WW2 German E-boat semi-displacement hull?

    I've heard it was the 'sweet spot' in that it was just big enough to approach "50 knot barrier", as well as run economically at a wide range of speed and loadings. Started out with 3x900hp and ended at 3x2500hp with plans for 3x3000hp, with large increases in displacement on basically same hull.

    It was developed from a high speed 'commuter' yacht built for a banker, so I'd assume it has a decent 'ride'.

    How about some underwater view ports(not for whales but other stuff)?

    Sure there would be design and safety 'issues' but with new tech and materials should be doable even on high speed passenger boat.

    Ever consider branching out to commuter ferry biz when the whales ain't cooperating?
  13. El_Guero

    El_Guero Previous Member

    CPT Cuda,

    I know people do not like to mention this, but if you lengthen the forward and rear part of your hulls on a Cat, you can narrow the hulls as well. Returns better fuel economy, performance, and sea keeping ability.

    Caveat, if done correctly.

    Yes, it is more expensive 'per passenger'. But, you can make up for that over time by reducing other operating costs.

  14. gonzo
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    gonzo Senior Member

    The HSC code makes reference to "non-displacement mode". How does this apply to long skinny hulls like on cats which can probably be claimed are always in displacement mode? Is it a waterline length/speed ratio formula?

  15. TANSL
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    TANSL Senior Member

    From HIGH-SPEED CRAFT, 2000 (2000 HSC Code) :

    1.4.30 "High-speed craft" is a craft capable of maximum speed, in metres per second (m/s), equal to or exceeding:
    3.7 D^ 0.1667

    D = volume of displacement corresponding to the design waterline (m3)

    excluding craft the hull of which is supported completely clear above the water surface in non-displacement mode by aerodynamic forces generated by ground effect.

    It's a totally different concept of, it has nothing to do with, ships in displacement or semi-displacement mode.
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