Looking for a N.A. for 85' passagemaker

Discussion in 'Boat Design' started by Tritonsubs, Jun 18, 2011.

  1. Tritonsubs
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    Tritonsubs Submarine design & build

    I'm interviewing experienced naval architects to create a design for a long (81'LWL), thin (<17'), 85' passagemaker with a steel hull, aluminum superstructure and powered by twin engines, single shaft. I'm interested in a very fine bow and lots of structural glass (think Dashew's FPD) and excellent efficiency with a minimum 5000 nm range at a V/L of 1.1. The vessel would be built in China or Turkey and will have to carry, launch and recover a 3 ton deep submersible with a stern platform or U-frame. I'm looking for someone experienced, cost effective and who generally embraces the vessel concept.

    Any recommendations? Any qualified, interested candidates? I have a design brief that can be reviewed.
     
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  2. Brian@BNE
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    Brian@BNE Senior Member

  3. Mark Cat
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    Mark Cat Senior Member

    Tritonsubs,

    Hi, The advances in high strength aluminum probably deserve another look for the size vessel you are proposing. A steel hull, in my opinion, is actually better suited as a design option for vessels over 140 feet.

    There are a lot of advancements in hull/superstructure design/integration that are not really discussed outside of the large mega yacht builders and the military.

    One key area is using large Alustar 5059 plate sheets to cut unbroken frames and other structures such that the as per welded reduction in strength is avoided in an overall structure. Also, more transverse frames of smaller thickness can be used for equivalent weight/strength, which aid in creating smaller and equal areas of deformation for high dynamic hull loads.

    I have discussed with Dashew specific elements of his boat (the original large design) for high latitude operation and considerations for meeting ABS and ISO rules in terms of strength and survivability for vessel icing and navigation in thin ice. That is, meeting early with these groups to explore classification for high strength aluminum hulls which needs to be properly addressed and recognized in validating newer aluminum structures to deal effectively with ice loads.

    One area of interest to me for high latitude in respect to Dashew was in the redesign of his standpipe for raw water access, and the ability to clear the standpipe after a 46CFR/SOLAS dead-ship freezing event. I sent him an email detailing the improvements. His decision to use a standpipe instead of a seachest was valid but there was still room for improvement.

    Also, another breakthrough area for the newer aluminum hulled vessels is to use large shell keel coolers that are welded to the inside of the hull plate. Essentially the shells are large structures that go on the inside of the hull and have an fluid cavity of perhaps an inch for coolant to circulate. These act as the diesel engine(s) raw water coolers, and even though the hull is thick perhaps 5/16 inch and painted, they are still effective in transferring heat.

    With a forced ventilation cooled dry exhaust (a double wall structure, SS316L center + SS spacer (air gap) + aluminum), there is no need to access raw water for engine cooling. The hull frames, longitudinals and shell cooler(s) are designed together to form a strong hull structure. Like a mini double hull

    After all of the aluminum hull elements are welded, the inside of the hull is sprayed with Mascoat 25 mils insulating anti-condensation paint. This helps insulate the shell coolers relative to the engine room and other spaces within the boat.

    If you would like more details on this approach let me know.

    Most who are watching the application of aluminum for large yachts to 120 feet, and aluminum military ships understand the pace of advancement with some of the new alloys for maximizing strength with minimum weight.

    Mark
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    Recommend you spend more time establishing an SOR that is feasible first.

    From you brief a hull of those dim's and shape would displace around 60 tonne.

    The structure weight, in steel, would be around 40 tonne.

    To cruise at roughly 10knots for 5000nm range say at a total of 200kW power from the engines, gives roughly 30 tonne of fuel.

    Just the structure and fuel, nowt else is 70 tonne.... :eek:

    So, just the structure and the weight of the fuel is greater than your brief SOR for the hull dim's.

    More investigations required.
     
  5. Tritonsubs
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    Tritonsubs Submarine design & build

    N.A. for 85' Passagemaker

    Thanks for the responses. While I don't doubt that there would be significant advantages to an Al vessel, we feel more comfortable with steel. Repairability, resistance abrasion, fireproof-nature and lower construction costs are all factors in our decision. And, as submarine guys, it's a material with which we have experience.

    As far as the brief is concerned, we're advocating an unusual vessel that's almost as much sailboat-like as powerboat. Let's look at an extreme case. In George Buehler's book The Troller Yacht he gives specs for his steel Ellemaid 81. 77' on the waterline with a 14' beam and a 6'6" draft displacing 101,000 lbs. His theoretical calcs give a 5489 mile range on 1000 gallons using just 57 HP to move at V/L of 1.2 at 10.5 knots. It has a canoe stern, but a steel deckhouse and all in all, the numbers are more than a bit suspect. We need a conventional stern and probably 16' of beam in our allowance of 180,000 lbs.

    Dave Gerr's Summer Moon at 81'8" is steel with an aluminum superstructure. 15.5' beam, 7' draft and 123,000 lbs. With 3200 gallons of fuel she has a range of 2400 nm at 14 knots, 4000 at 9.2 knots and 5100 miles at 8.1 knots. The 9.2 knots is about V/L of 1.1. So the question is, could you add 1000 nm range (800 gallons, 5700 lbs) in a slightly larger boat with an additional allowance of over 55,000 lbs (180k lbs - 123k lbs)? I guess the answer is yes.

    Using various displacement speed formulas you get about 195 shp requirement to move 180,000 lb vessel with a D/L of 154 through the water at V/L of 1.1. To make 5000 nm you need 5000 gallons, so 35,500 lbs of fuel. Can you get by with 135,000 lb structural weight. I think it's close. A couple of leading N.A.s agree. If you have to slow down to 9 knots or add some displacement to achieve the goal, that's O.K. That's what goals are for, to see if you can achieve them, and that's why I am looking for an N.A. that agrees that we can get close. This is not a Nordhavn, Krogen or Cape Horn, it's much more like an 83' FPB out of steel. The bow is very fine with absolute minimum reserve buoyancy forward.
     
  6. Mark Cat
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    Mark Cat Senior Member

    Tritonsubs,

    You have made your direction very clear, but consider the following when looking at weight in terms of actual performance.

    ----------

    I did a lot of analysis on a 74ft power aluminum work boat CAT. It was an excellent stable platform for work at sea.

    A lot of the vessel final design decisions included the advice of our consultants, captains, engineers, cooks and feedback and standards from organizations like USCG, ABYC, ABS, and ISO.

    Each hull housed a large V12 diesel propulsion engine and I6 genset. Having the two hulls provided engine redundancy in-case of propulsion or genset failure.

    The propulsion engines selected needed a continuous HP rating to achieve 16 knots cruise with max around 22 knots. This was done to allow one to out pace the weather at sea at high cruise and extra top end to navigate in heavy seas.

    The engines had to be rated continuous at around 1100HP and this required a large and heavy V12 engine from MTU or MAN. The gensets were inline six cylinder 25kVA.

    There were 2 aluminum tanks of 500 Gallon in each hull (total of 4 for the boat), with the provision to add 4 custom made portable auxiliary aluminum 500 Gallon tanks for long cruise or fuel resupply. The boat was set up with all of the special mounting and plumbing to allow managing the aux tanks.

    If you drop down to about 12 knots I think you could go from San Diego to Hawaii, regardless of the occasional bucking seas, run the gensets continually and get there with plenty of reserve.

    When not in use the portable aux tanks where left ashore. This was a good way to carry this extra fuel because of the special nature of setting up for a long cruise, or using the tanks to deliver diesel fuel to an outpost or island for use in diesel vehicles or construction equipment.

    So in this size boat it came down to managing weight and the realization that any weight savings in overall hull/superstructure design could go towards useful weight for engine size and fuel.

    The speed estimates are for a fully fueled, manned and provisioned excursion.

    For this 74ft craft, achieving the required performance required weight to be reduced at every opportunity.

    Mark
     
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  7. Tad
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    Tad Boat Designer

    In reality Ellemaid (as built by ASBoats in Turkey) displaces about 130,000 pounds (with a fuel capacity of 1700 usg) and has 180HP installed. On a good day downhill she will manage just over 9 knots with that power......don't take seriously any statement by G. Buehler about required power or fuel consumption.....

    Has not been built......
     
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  8. Tritonsubs
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    Tritonsubs Submarine design & build

    Fair enough. The FPD would be a better yardstick, perhaps, with good data for the 83 and the 64. And, no doubt there are some other examples but this is not my area of expertise and one has to start somewhere, and published figures are easy to pull off the shelf. Still, I believe the brief is reasonable and the approximate numbers achievable.
     
  9. Tritonsubs
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    Tritonsubs Submarine design & build

    It looks like we've found a naval architect for the project after weeks of interviews and discussions. He was formerly at Wally Yachts and at Tripp Design and while others have embraced the brief we think he has the experience to do a great job for us.

    I also have a good friend and business associate in Turkey who has recently opened a yard and is building two 20 meter high speed catamarans that will carry and support two of our 8 ton, 3-passenger, 1000 meter capable luxury deep submersibles (tritonsubs.com). The boats will be finished in April of next year. I think we'll have him do the construction. Having a professional you know and trust at a foreign yard is worth a lot.

    So, we're on our way. I'll post images of the design as it progresses. If anyone is interested in seeing and commenting on the brief, I'm happy to send it along, just PM me.
     
  10. Mark Cat
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    Mark Cat Senior Member

    Bruce I am glad we could help in providing a forum for discussion given the launch and retrieval nature of the submarine.

    Take a close look at the high speed Catamaran ferry design from Turkey. I think you will find the operational requirements of a ferry are considerable different than an expedition/launch platform vessel needed to cross the Pacific ocean.

    I like the idea of an Aluminum Catamaran, much in the shape of the ferry, but modify the "garage" to house the two submarines, so they can be serviced and maintained indoors regardless of the weather. You could launch the subs down through the center of the garage, between the cat hulls, through a retractable hatch.

    If the launch cradle was design for below the water retrieval (built in gaurds for the hulls) you could bring the subs up even in heavy weather.

    Mark
     
  11. Tritonsubs
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    Tritonsubs Submarine design & build

    The aluminum cat tenders for Triton are here: http://tritonsubs.com/support.html

    They are 20 meters in length and have a stern platform between the hulls aft of the superstructure that launches and recovers the sub. This is an elegant solution and the interior of the platform uses water ballast to compensate for lack of load when the sub is away and in use. All the support equipment, battery chargers, high pressure air compressor, etc are integrated in the engine room with the exception of the oxygen transfer pump and O2 storage which is secured to a bulkhead on deck. It's a slick system. The subs weigh 8 tons.

    After much time at sea I am not really comfortable in FRP or aluminum for long distance trans-oceanic travel. I've seen an aluminum boats hit a reef in Indonesia and backoff and sink in moments, and an FRP burn to the waterline in a horrific fire in the South Pacific. If I'm taking my family to sea, I'm archaic and want it to be in a steel hull. So, a long thin monohull makes sense for me.

    I've been building civil subs of all types for 25 years, from large luxury subs, tourist subs, research subs, commercial rigs, etc. Launch and recovery from ships is always a problem because subs must always be heavy enough to weigh as much as the water they displace, but we've been solving those issues for an equal period of time. Platform lifts, A-frames, U-frames, ramp lifts, articulated cranes, conventional davits and even moonpools all have their place. For subs over 20 tons we like the water garage approach where you surface the sub, drive it perpendicularly into the side of the ship, close the hatch and pump the water out. We are doing systems like that for a very large yacht (100+m) and again, in conjunction with a major cruise line that will carry an all acrylic 16-passenger tourist sub on around-the-world trips.

    In comparison, a 3 ton sub on the back of an 85 foot steel monohull is not a difficult proposition. What's important is designing the system for effective one-person use. This limits an airborne approach which requires skilled crew using a couple of control lines and capstans to limit roll response.
     
  12. Mark Cat
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    Mark Cat Senior Member

    Bruce you have some really interesting approaches to retrieval.

    I know you are not using a CAT, and I like the dry (wet) dock approach. Very innovative.

    But, what if we had a CAT and a single sub was lifted using hydraulics up from the center of the hulls into the garage, but there was no hatch. Meaning the bottom of the sub wedged into and locked into the garage deck using pins. Such that the bottom of the sub formed part of the Cat bridgdeck (under body), when retracted into the garage. This would simplify retrieval. Basically, to combine the design of the sub and the CAT to mesh together with minimum fuss and complication of dead weight and displacement. The hydraulics could retract into the bridgdeck during retrieval.

    ----------

    I would urge you to look at some of the ocean going aluminum hull designs. There are safe guards against sinking that you describe. Like a forward water tight compartment in the bow, and reinforced keel/bow runners (large aluminum extrusions), that will allow a blended Bow/keel/skeg design to sled over just about anything.

    Also a CAT, if designed for it, can be beached to allow work to be done in places without a lift.

    Mark
     
  13. Tad
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    Tad Boat Designer

    I'm not convinced that "absolute minimum reserve buoyancy forward" is the best all around solution. No question a fine waterline (low Cwp) entrance provides the lowest resistance in calm water and at low speed. But at higher speeds and in larger seas the lack of buoyancy forward can allow an increase in pitching and lots of water on deck. Have a look at any VOR footage on youtube for an extreme example. Also see the recent crash of an AC45 cat in San Francisco.......

    Dashew is a canny marketeer and he's done well producing fashionable powerboats that echo current modern sailing yacht designs. A big part of marketing is establishing a definable product, which he has done. I prefer a more moderate approach as seen in my PL74 or in the Briand designed Picchiotti Vitruvius, both with B/L approaching 5 at waterline. Both hulls include some moderate flair in the upper forward sections. One of the added benefits of this shape is additional deck space which is useful for tender storage in smaller boats where space is at a premium.

    For more info on high speed seakeeping see the SNAME paper, The High-Speed Displacement Ship Systematic Series Hull Forms--Seakeeping Characteristics, by Blok and Beukelman, 1984.
     
  14. kc135delta
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    kc135delta Junior Member

    Tad,

    Speaking of your PL Series, I noticed that the larger 80' and 98' models have the sole of the lowest deck above the waterline while the smaller models do not. Is this a necessity of the low displacement and large tankage or just a precaution of some sort? I would think you could gain a lot of internal space if you lowered it, possibly two decks forward on the 98' model?

    Just a observation/thought.
     

  15. Mark Cat
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    Mark Cat Senior Member

    Tad,

    I went to your passage maker web site, very nice.

    The PL 80 looks very interesting, my large Al projects are all CATs.

    Can you discuss your cold-molded / aluminum construction approach?

    ----------

    I have attached the Caterpillar 3306B data sheet. Which does not have nearly the HP you have on your web site.

    Caterpillar 3306B = 215BHP, perhaps I have the wrong engine. You listed for two = 3355 HP?

    For reliability and fuel efficiency far from home, take a look at MAN or Cummins.

    If US flagged I would choose Cummins.

    I like the idea of the twins for redundancy. I had a similar prop challenge in the available draft for a large output engine on the cat. Even with a tunnel, the prop was a challenge because of the limited space.

    Dealing with 4000 US Gal installations for refuel and potential issues with fuel contamination is a challenge.

    For a monohull power boat there can be 2 or 4 wing tanks and a center day tank.

    Transfer pumps move fuel around for trim, and support refuelling from either fill port or stbd. For 4000+ installation on an 80ft may need a ballast tank for proper trim under some conditions.

    In doing the weight estimates for the 74 ft Cat work/supply boat I was surprised by the requirements to support two gensets (weight and added fuel consumption). Depending upon passengers and crew, electrical power consumption can be significant for pacific ocean crossings. This translates into added diesel fuel consumption.

    For me tankage was also a challenge:

    For the Cat in each hull and total (US Gal):

    Diesel fuel 2x500 main, 2x500 aux (mounted near hull CL on deck out of the weather), total = 4000.
    Fresh water 2x250, total 1000. Never have one water tank, in case of contamination, unless there is a backup reverse osmosis system.
    Gray water 200, total 400.
    Dark water 100, total = 200.
    Filtered salt water 100 = 200.
    Diesel engine oil new = 30, total 60.
    Diesel engine oil old = 60, total 120.

    The hulls had holds that were used for added provisions (dry goods), and supplies.

    Mark
     

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