Discussion: Pocket Cruising Power Catamaran Design for Recession Times...

Discussion in 'Powerboats' started by Seagem, Jan 11, 2009.

  1. Manie B
    Joined: Sep 2006
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    Location: Cape Town South Africa

    Manie B Senior Member

    Hi Mas

    just something that is very interesting - even for your "Oram"

    the 50 hp E-tec is such an unbelievable motor that we are dumbfounded - these motors have ONLY cost new sparkplugs in 3 years - nothing else = untouched !!

    i can asure you that 2x 50 E-tec will be excellent for you :D
     
  2. masalai
    Joined: Oct 2007
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    Location: cruising, Australia

    masalai masalai

    Where I will be going - - NO PETROL... and limited diesel but will run on coconut oil nicely :D:D:D or sails/breezes or up some small creek waiting for balmy weather:D:D:D - the hi-thrust 9.9 outboards are usually used by those keen on 4 stroke petrol option for this boat, and up to a centrally mounted 25hp in a pod......

    Any views on the Torqeedo 2000R or 4000R electric drive legs? they look promising, light and fairly robust but engine life is a question.... http://www.torqeedoaustralia.com/Torqeedo_Australia/Home.html

    I like the "Polar Power" dc generator but difficult supply line from USA - Light weight and 5 to 7 kw battery charging capacity into 24 volts would be nice....
     
  3. Seagem
    Joined: Jan 2009
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    Location: Cayman Islands

    Seagem Junior Member

    Thanks for finally focusing on the boat design at hand, rather than the poster or the economy. This is a very nice design and I'd like to know a lot more about it, such as length, beam, bridgedeck clearance, designer, builder and more inside pics of the berth, etc...

    If the vessel can really do 30 knots WOT with only twin 50hp, it would have to be the most efficient cat design ever in its category...

    You still appear not to get the reason why the boat needs the capability of making fast passages of up to 200 miles in open waters: it is designed to cruise the entire Caribbean and suitable weather windows can close quickly, therefore, you don't want to linger out there doing 10 knots while the weather is still nice...

    Another consideration is that if/when the boat goes into production, there will be another version on the same hulls dedicated to the fishermen, amateurs as well as professional, who have to travel 60 miles to productive fishing grounds: I doubt that they'd appreciate a boat that needs 12 hours at 10 knots to do the return trip...

    If in doubt, ask the tuna fishermen off the coast of South Africa who run Butt Cats 50/60 miles out...

    Btw, South Africa is one of the best locations in the world to find well designed cats that are built to take a pounding...
     
  4. sabahcat
    Joined: Dec 2008
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    Location: australia

    sabahcat Senior Member

    :rolleyes: :rolleyes: :rolleyes:

    Manies shown us his, how about showing us yours
     
  5. rasorinc
    Joined: Nov 2007
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    Location: OREGON

    rasorinc Senior Member

    MANIE B I have interest in your friends 30' x 14' cat as I am just starting a ' 30' x 9'-6" cat out of Doug Fir and marine ply. I calculate the finished weight without engines or fuel/water at 3,500 to 3,600 pounds. What is your friend's hull built of. Played around with a speed chart with 2-50 hp 4 cycles and came up with about 22-23 mph top speed. Any info you wish to share on that boat will be greatly appreciated. It will be a live aboard for months at a time so gross weight will be about 4,400 pounds. Thanks, Stan
     
  6. apex1

    apex1 Guest

    We have a term for those "experts" nappy pooper:p

    Regards
    Richard
     
  7. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    I'm with Manie and Masalai on this one :) Although my tastes, for the present, tend somewhat smaller- trailerable beam, light enough to pull with a vehicle that doesn't suck back 20+ L per 100 km, and would spend a lot more time on canals and lakes than on the ocean. I have one on the drawing board now (a competitor to the light planing cruiser some of you have heard me talking about) that's 8 m on the waterline, 2 t nominal full-load displacement, and would max out at 20 knots with 20 kW effective (so about 35 kW engine power, or 2 x 20-25 hp outboards). Probably not as efficient per tonne per knot as what Manie and Mas have been talking about, but different design constraints too.

    Glad to hear the Etec is working out for you Manie. It's starting to like the whole FICHT disaster and subsequent total re-engineering of the entire Evinrude product line has a happy ending....
     
  8. Chris Ostlind

    Chris Ostlind Previous Member

    Hi Matt,

    Is that a North American universal trailering width of 8.5', or a permitted beam of 10' for trailering?

    Your project sounds remarkably similar in scope to a power cat I've been developing based on the 21' Gato Especial sail powered cruiser, shown below, I have shown here before. I'm really excited about your interest in this type of boat. I'm looking at this as a garage sized, homebuildable for the power boat guy who got the pure white light bulb of his fuel bill this last summer. The gas pricing, as most well-read folks understood, was short-lived and we are heading back up the ladder, once again, towards the USD$4 a gallon fuel at the marina.

    I also like the twin engine mode you have indicated for weight distribution and redundancy. It's an interesting set of problems to get the best bridgedeck height while keeping the COG to something I would call manageable for the average throttle jockey owner.

    Any comments you may have on the process you have expressed are more than welcome, as I'm still looking at the various solutions before I drop the hammer on the design.

    Chris
     

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  9. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    Hi Chris,

    Your design expertise substantially outstrips mine, and I would love to fire your post right back at you :)

    I use 8'6" or 259 cm for trailerable. Although it's generally not too hard to get permits for up to 10' (305 cm), they need renewing all the time and don't necessarily cross borders, while an Ontario perpetual trailer licence plate for 259 cm or narrower is a one-time fee and is good for the whole continent.

    I have a bit of a competition going between two designs, each of which has spawned a few variants. Basically, it's a lightweight, high-efficiency shallow V planing hull ( http://www.boatdesign.net/forums/pr...ing-around-10-m-trailer-cruiser-17597-10.html )squaring off against a lightweight, high-efficiency cat of similar length (8m LWL, 8.5m LOA) and displacement (2 to 2.5 tonnes loaded) with inland lakes and canals in mind. So 5 knot no-wake cruising on the canals, but able to open up to 16-20 knots for crossing open areas, and seaworthy in the sudden storms that spring up on Georgian Bay, Lake Simcoe, etc. with camping-like (not yacht-like) accommodations for 2 people, 4 on short hops. We'll see where that goes, hoping to have a place to start building (and a job to pay for such) in a year or two.

    The bridgedeck clearance seems to be a nasty issue. My opinion (for now, open to change) is that if you can't get 1'6" to 2' clearance in something meant for lake use, or at least 3' in an ocean going cat, ditch the standing-headroom deckhouse because it just ain't gonna work. Pontoon boats regularly cruise around with less than 1' bridgedeck clearance and every fourth wave hits the deck in a Force 3.
     
  10. Willallison
    Joined: Oct 2001
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    Willallison Senior Member

    Yowzers!.... Some threads just seem to get off on the wrong foot don't they!

    Ok - 25 ft, 30 knots. You're talking about a planing cat hullform to start with. I think I'm correct in thinking that the Prowler is a displacement hullform and not designed to travel that fast, but may be wrong. A displacement cat can be pushed to that speed, but it won't be as efficient as planing hull(s). The flip side is that the planing cat is unlikely to be as miserly as a displacement cat at slower speeds.
    Unlike many of my esteemed colleagues here, I most definitely see the advantage of a cruising boat that is capable of relatively high speeds - though packaging it in a small, efficient package that's also capable of medium term accomodation is quite a challenge.
    I've done quite a bit of coastal touring in a deep-vee monohull that is quite happy cruising at 40 knots, but it's not particularly efficient. Nor is it overly comfortable. But it does allow one to cruise quite broad areas in limited time frames and to escape unpleasant weather.
    The goal then is to create a platform that's capable of reasonably high speed when conditions suit &/or are required, but also the ability cruise comfortably and efficiently at lower speeds when you're not in a hurry or when weather conditions dictate that you can't travel quickly. In generaly, productions fall woefully short on just about everycount.
    The catamaran is one solution - I personally favour the displacement cat as most of one's travelling is likely to be between 10 and 20 knots. The biggest problem with a cat, though, is that they are so expensive to build / buy. For 99.9% of the population this additional expense will never be recouped in the form of lower operating costs.
    My own solution, drawing below is currently under construction, offers most if not all of your stated design goals, but in a monohull. Ultimately, it probably won't offer quite as good fuel economy as a displacement cat with similar levels of accomdation, but the build cost is probably 50 - 100K less.

    There are other solutions too...yours may be one of them. If you want more positive feedback, I suggest that you post some basic sketches of your idea's. I can assure you that whilst critical, the resulting comments will all be valuable.....
     

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    Last edited: Jan 12, 2009
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  11. marshmat
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    Location: Ontario

    marshmat Senior Member

  12. Willallison
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    Willallison Senior Member

    Matt - I agree.... I reckon a minimum of 900mm for bridgedeck clearance, and preferably more than a metre. Few small cats manage this however, for obvious reasons, so slap appalingly when going slow or at rest.

    (fixed the attachment sorry! Though it is an older version of the boat)
     
  13. Seagem
    Joined: Jan 2009
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    Seagem Junior Member

    This one veered off from the second post onwards, as some posters prefer to nitpick or talk about their pet project, rather than contribute some useful comments, as you have just done...

    Btw, if you click the links I provided in my first post, you will see the pics of all the boats under consideration and/or whose features are desirable...

    I looked at monohulls first and the Cape Cruiser 23, now built as the C-Dory Venture was top on my list as a very frugal cruiser that incorporated most of my requirements, except for a self-bailing cockpit:

    [​IMG]

    Additional interior photos can be found here:

    http://www.c-dory.com/boats/venture_23/23 Venture photos.html

    Well equipped recent models can be bought for around $50,000.00 with a 150hp 4-stroke motor that will give 22/25 knots cruising at 4/5 mpg...

    The pick of the crop in terms of planning design is the 22' Morrelli/Melvin foiler that banks inwards in turns, thanks to its asymmetrical hulls, has wide chines to keep the spray down and a very efficient looking wake...

    [​IMG]

    These short videos help illustrate the issue...

    http://www.haasmarine.com/Action_Shots.html

    In addition, the new Schionning design 750VT, a semi-displacement hull, brings some interesting new ideas to the concept, such as: "sharp entry at slow or high speeds, load carrying ability aft where the weight is usually concentrated, easy access to hulls from bridgedeck and clever location of the outboard engines, which have a clear water flow while keeping the stern platforms free. This also moves the engine weight and prop further forward, reducing potential aeration in rough seas."

    [​IMG]

    This file shows how the boat is built using CNC cut Duflex panels and the unusual shape of the chines and outboard set up...

    http://www.schionningdesigns.com.au/login/pages/images/VTmanualbuildsequence.pdf

    The drawback of the design is that it has a high wetted area and it won't bank in turns. Also, I suspect that the claimed top speed of 30 knots with twin 140hp outboards and 1.2 liter per nautical mile (better than 3 miles/gallon) at a non-stated cruising speed, mentioned by one of the outfit building the boat are exaggerated...

    What I'm trying to achieve is to amalgamate all the most desirable design features of these boats into one super duper pocket catamaran, as described in my opening post and all comments focused on the subject at hand are welcome...
     
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  14. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    Hi again Seagem,

    Looking through the site for the Spartan 22 you mention, I note that she's designed for up to 280 hp. 24 degrees at the transom is an awfully sharp deadrise for such narrow hulls. I think the reason the wake looks relatively small in the photos is because the boat is going like a bat outta hell, thus she's riding high; it's a hull shape evidently intended to keep a good turn of speed up in bad chop. Although likely a little more efficient than a comparable mono, I suspect she'd still rack up one heck of a gas bill.

    The Schionning boat- Prowler VT950 if I'm not mistaken- is an interesting boat. She's labelled as a semiplaning type, but really it looks more like a sharp V-bottom displacement hull with enormous chine flats grafted on. With the same 2 x 140 hp as the Spartan, they're claiming 17 knot cruise and 28 knot WOT at 4000 kg light / 5500 kg loaded. Significantly faster than a typical mono of comparable weight and power, but you still have the gas bill that comes from feeding 280 horses. Once you get to a boat that size I think you're pushing the limit of what you can reasonably expect an O/B to do with any reasonable efficiency, they just can't swing a wide enough prop for a fast 5-6 tonner.

    If you're looking for a "recession proof cruiser" for the Caribbean, then as Manie, Mas, Sabah, Rasor and I have mentioned, the 25' planing hull originally proposed doesn't seem to fit. Blasting around at 20+ knots is fun in a runabout on a lake, but in 6-footers would get real tiring real fast. I think that for Caribbean cruising, trying to beat weather windows, the boat Manie mentioned in post #14 would be a good starting point. Going to a full planing hull might get you halfway there faster, but it'll leave you wishing for the larger, displacement type when the storm changes direction and hits you anyway.

    We've been tossing all these options out here- plus the smaller versions Chris, Will and I have mentioned- because we're trying to get a feel for what hull forms, what sizes and speeds and powering options, might be involved in a boat like this. It's how we work on this forum- we bring up stuff that's related but not exactly what the original poster wanted, to see where it goes and what ideas we can extract from it. I don't know if you've spent much time around engineers and designers in between your days on the trading floor, Seagem, but this is how the design process begins. If you learn to go with the flow and not take offence when people question your plans and motives (engineers question absolutely EVERYTHING), you'll find that there are a lot of people here who are very interested in the kind of project you're talking about, and have a lot of ideas on how it could be done.
     

  15. Willallison
    Joined: Oct 2001
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    Willallison Senior Member

    A cat with the beam of the Prowler is unlikely to bank into turns, regardless of hullform. I'm a little wary about some of the other aspects of these boats too, as I've seen examples that are VERY lightly built... I'd be sceptical about their longevity or ability to weather any kind of real sea. I've also heard tales about perculiar performance habits, though I've seen no real evidence of this.
    A boat like the Morelli & Melvin that you posted is never going to be able to contain the kind of accomodations that you describe - it's a trailerable fishing boat (or appears to be). Increasing the beam is likely to eliminate the banking into turns that you appear to be so keen on.
    As I said before, and I was merely repeating what others have suggested, the best way for you to get some useful advice would be to post some preliminary sketches of the sort of thing you're talking about. Don't worry about any lack of drawing finesse... they just need to show roughly how you intend to incorporate all the features you've described into the sized boat you're talking about.
     
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