Have concept for crusing cat - what next?

Discussion in 'Boat Design' started by gardnerpomper, May 19, 2008.

  1. gardnerpomper
    Joined: May 2008
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    gardnerpomper Junior Member

    Hi,

    I have owned and sailed monos, tris and cats for 20+ years. I've sold my latest cat and am looking to have one built in 5-6 years. I have searched for existing designs, and concepts for new ones and have cobbled together a hodgepodge of ideas that I think would be an improvement for my needs, and are considerably different from any production boat. I was hoping that I could post a description in these forums and get some feedback, including some information on how to approach a designer for general feasability info.

    Usage:
    My basic criteria are to cruise from Maine to Venezuala with 2 people and (hopefully) frequent couples/kids visiting. I want to motor as little as possible, but will use the ICW, so I need mast heights under 65'. We want refrigeration and a freezer, and sufficient electrical capacity for lots of electronics (both my wife and I will continue to do computer consulting). We like an open bridgedeck, with a hard roof for sun protection and mounting solar panels. We rarely, if ever, go to a marina except to refuel. I would like to remain under $200K for the basic construction (i.e. constructed to the point that I can sail it back home and do the interior finishing myself).

    Background:
    I have been following the harryproa design discussions for their 60' charter proa version, for which cost is a major factor, and I think they have some excellent ideas, which don't require the proa form factor. The first is that you can just use the hulls for floatation and machinery and save considerable build time by not having to finish the interiors and build complex shapes for accomodations. The second is that by using a freestanding mast, you can concentrate the loads just around the mast and build lighter and cheaper on the rest of the boat. Borrowing heavily from those discussions, and from other designers (notably Brian Eiland for his centerboard idea), I have worked out what I think I would like.

    Concept:
    The idea is that we build all the accomodations on the deck. As I lay it out, that will require about 25' by 25' (approx). Port side aft is a stateroom with a walkaround queen bunk. Forward of that is a head. Inboard of the head is a nav station and forward of the head is a table that converts to a queen bunk. Starboard side is similar, with the galley, instead of the nav station. On the centerline is the dining table, built over a centerboard trunk as Brian Eiland described. Forward of all of these is the saloon area, for the full width of the deck (25') with tables on either side that convert to queen bunks.

    The whole deck is open in the sense that the hard roof is held up with posts, and the sides and stateroom aft sections are plexiglass. The forward portion has rollup clears and screens, as does the aft center, behind the helm.

    We have one freestanding mast in each hull. The rig is uncertain, since most bi-rig catamarans seem to have a mast with just a main, but I am thinking it would be better to have an aerorig style rotating mast with main and jib, or a dynarig, or a small fabric wingsail with a small amount forward of the mast, all to balance the sheet loads.

    By building all the accomodations on deck, my thought is that it is then a simpler matter to build very simple hull shapes, with at least a 16:1 length to beam ratio. I would guess about 45-50 feet, but that has to be calculated.

    I would like shallow draft, 2' or less if possible, using Brian Eiland's centerboard concept for asymetrical centerboards mounted under the deck. The idea of the slotted rudders also appeals to me for controlling the draft.

    I am guessing that the lowest cost propulsion system (after outboards, which I rule out for personal reasons) is a small diesel (with a large alternator) in each hull and folding props, but I would prefer to have some system where the propellers tilt up out of the water, so if someone has ideas on an inexpensive way to do that, I would be interested. Perhaps a single diesel with hydraulic drive to 2 propellers (I want 2 for the maneueverability).

    Cost:
    I know that I can get boats in the 35-40' range with this type of accomodation, but I would like a longer, faster boat without paying more. My reading suggests that I can accomplish this by reducing the complexity of the parts because labor is the most expensive part of boat construction. Therefore, I am looking for what one might call a "home built" type plan, but I will most likely farm out the construction for bids.

    Next step
    This is my main question. I am not ready to commit to a full blown architectural type drawing, but I would like to get professional feedback on whether the concepts actually make sense, and if I can save enough by using very simple construction techniques to overcome the expense of a larger boat. Do I contact a naval architect at this point?

    Thank you all for wading through this lengthy post.

    Gardner Pomper
     
  2. kengrome
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    kengrome Senior Member

    Gardner,

    The first thing you should consider in order to reduce costs is to have the boat built overseas where materials and labor cost far less than in the USA. Next, you should minimize the boat's weight because the more the boat weighs the more it costs to build.

    I cannot see you getting a 45-50 foot hull for the price of a 35-40 footer because the bigger boat will weight more so naturally it will cost more. The 65 foot catamarans I worked on (and lived on for a while) two decades ago cost more than a million dollars each. That was in the early 1980's. They would certainly be worth 2-3 times as much now, if not more.

    The last price I gave a guy for a boat your size was $7 per pound for the completed hull, but I think he thought he could get it for $2 per pound so I never head from him again. I live and work in a third-world country with low materials costs and even lower labor rates, but some people's expectations are still unrealistic -- not a rare occurrence in this industry either if you want to know the truth.

    Maybe the best thing for you to do at this point in time is to get a weight estimate for your design concept, then multiply it out by a realistic per pound estimate and see if you can afford what you want. If you cannot afford it, you're better off scaling down or forgetting about it rather than investing any more time in what might be an impossible dream.

    Michael Kasten seems to have a pretty good handle on the cost of building overseas, and he uses "per pound" figures when building boats in Indonesia whether for himself or for his clients. You may want to contact him for more info. He's got an informative website too:

    http://www.kastenmarine.com/

    Regarding your concept of putting all the weight of the accommodations up high, I think it's a bad idea unless you compensate by ballasting the hulls so much that your efficiency will suffer ... and if you do this you will lose the speed you tried to gain with the longer hulls, right?
     
  3. lukabg3d
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    lukabg3d Junior Member

  4. Bryan 44c
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    Bryan 44c Junior Member

    The advise based on 7$ per pound is pretty sound as a minimun. I am building a modified oram 44c in Australia. 45' by 22' it will weigh around 8000 lb at launch, light ship. The material cost for structure for the shell is about $75000 Australian, around $9 per lb. The structure is almost completly epoxy glass, balsa core.
    Remember that the shell is around 1/3 of the boat launch cost, Then add labour. In my case 4000 hours.
    Check out the Bob Oram Design site, the 44 c meets a lot of your requirements, one is even being built with a bi rig. His boats can be built with pretty much any layout between structural features and his plans are quite economical, after all a slightly customised stock design will always be cheaper to engineer and build and will retain better resale than a one off.
    By the way my boat has a small diesal genset ( 6 kilowatt. 250 lb) and two Re-E-Power system 3000 submersible electric drives on my own costum swing legs.
    Why all the bunks and converibles for just two?

    Cheers Bryan
     
  5. kengrome
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    kengrome Senior Member

    Gardner, please excuse me for a moment while I address "lukabg3d" directly:

    "lukabg3d", I think it would be very respectful to the forum host (and to the rest of us) if you and "Djape" and "amber" would simply STOP promoting your boatcnc website every chance you get in other people's threads -- especially when the boats being discussed are so dramatically different from the boats you're trying to promote ... :(

    Look, if you want to tell Gardner that you'd like him to consider hiring you, or if all you want is to sell him a set of plans, the proper way to approach him is to send him a PRIVATE MESSAGE and make your offer directly. But to post a link to your site when it is as off-topic as it was this time is a blatant abuse of the forum -- in my opinion anyways.

    Sorry for the rant folks, I'm done now. Back to our regularly scheduled program ... :)
     
  6. gardnerpomper
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    gardnerpomper Junior Member

    Hi,

    Thanks for the quick replies. I'll address each by name.

    Kengrome: I am not a designer, so I haven't calculated the weights, not knowing what hull configuration I need, but I will borrow information from the 60' charter proa that Rob Denney is designing. He has a 60' narrow hull and a 40' wide hull. He just posted the calculated weight of his shell as 3.5 tons/tonnes and has a preliminary quote of $US 80,000 to build the shell (in Panama, I think). Mine is derived from that, and should be very close in weight. I will have 2 narrow hulls, about 50' each, 2 unstayed masts. I have a bit more deck space, but I don't expect it to work out very different.

    In terms of too much weight high up, I didn't consider that a problem, because all the heavy stuff will be in the hulls, as low as possible. This would include the engines, tankage and batteries. Pretty much all that is up top is some foam & fiberglass for moulded bunks, and the galley. I would not expect any additional ballast to be required, but it certainly needs to be calculated.

    Bryan 44C: I'll take a look at the orram site. Can you tell me more about your drive system with two Re-E-Power system 3000 submersible electric drives? I am concerned with submerged electric, in terms of things shorting out. What protection does the system have in case that happens? Do you have a website showign what you have done? I always assumed that these drives are cost prohibitive. Can you tell me what sort of pricing you are looking at?

    In terms of the bunks, they are my wife's requirements. She believes that we will get a lot of visitors. I am making as many of them convertable as I can, since I expect they will never get used as bunks :)

    Does anyone have more feedback on the rigs? I have not been able to dig up enough information to feel comfortable. The soft wing sail is probably my leading choice, although the junk rig has its proponents, but I can't find good data to compare upwind sailing capability on a junk rig. This is for cruising, not racing, but I do hate motoring. The more I read about the dynarig, the less it seems like it would suit a low cost boat. I do like to keep it simple.

    - Gardner
     
  7. gardnerpomper
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    gardnerpomper Junior Member

    Bryan 44C: I had not noticed right off the bat, but your $7/lb cost is just for materials? The charter proa, estimated at 7000 lbs, is being touted as using $28,000 for materials, for a total build cost (including materials and labor; shell only) of $80,000. I expect they are using polyester resin instead of epoxy, and I know they are using a some sort of foam (can't find the name of it at the moment) because they are using a build system similar to KSS, which will allow them to lay up each hull as 2 flat panel, then bend (somehow) up to form the hull in one step. Still, I am surprised by a 3:1 price difference for materials. I do know they are sourcing the foam from the US, as it is cheaper here.

    - Gardner
     
  8. kengrome
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    kengrome Senior Member

    Gardner,

    I don't know the construction type Rob is using, but here's a 50' catamaran with a dry weight of 16.5 tons:

    http://www.catana.net/frameset.php?page=modele2&lang=us&modele=50&rub=4

    You're suggesting a shell weight of 3.5 tons? Maybe, but it sounds too light to me. A Wharram Pahi 42 weighs 3.5 tons, how do you think yours compares in terms of furniture, fixtures, etc.?

    http://wharram.com/pahi42.html

    Wharrams may be the lightest catamarans available. Maybe yours can match even if you have an additional 15% added length, but I think it would be a real challenge.
     
  9. rob denney
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    rob denney Senior Member

     
  10. kengrome
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    kengrome Senior Member

    Hi Rob, it's great to have you in this thread!

    I wasn't suggesting that your proa weight is incorrect, I was actually suggesting that it would be very difficult if not impossible to build a 50 foot catamaran that weighs only 3.5 tons. Even the barest hull in the lightest materials would likely weight more, wouldn't it?

    If I'm interpreting this correctly it means a 50 foot cat will weight at least twice as much as a 50 foot harryproa. That's a big weight difference ...

    Gardner, would you still want to proceed with your catamaran project if it weighs (and costs) twice as much as you've estimated?
     
  11. gardnerpomper
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    gardnerpomper Junior Member

    Rob, maybe you can finally lay my confusion to rest. I know I had sort of asked you this before, but I guess I didn't understand the answer. I like the proa design, and am still very interested in it, but there seem to be some complications with the rudders and engines because the proa sails in both directions.

    My idea was to basically take 2 of your leeward hulls (from the charter proa or the 50' harry, whichever works), put an unstayed mast in each and plop the bridgedeck down across them. I don't understand the "round bilge rockerless hull" (well, i guess it is "rockerless" that I don't understand). Why won't that work on a cat?

    If I can't use those hulls, then I was thinking about the 45' Skimmer catamaran hulls (www.skimmercatamarans.com)

    I am really not trying to be argumentative, but I am really excited about your design and construction ideas and would like to understand why they are different between a cat and a proa.

    - Gardner
     
  12. Bryan 44c
    Joined: Apr 2008
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    Bryan 44c Junior Member

    Check out the Re-E-power web site, Cat package with two drives and controllers about $8400, fuse protected also link on the site to a forum, you will find some photo's of my swing legs there.
    The 44c weighs about 2.5 ton as a bare shell.

    Cheers Bryan
     
  13. rob denney
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    rob denney Senior Member

    G'day,

    Thanks Kenneth. Very difficult, probably impossible, judging by all the 50' cats out there.

    Gardner
    Rockerless refers to the keel line viewed from the side. The fastest shape is a straight line. Cats need rocker (curving up at the ends) for two reasons. First tacking. Rockerless hull don't turn very quickly. Harrys get round this with two rudders and minimal draft becasue of their light weight. Cats have to turn quickly or they will not carry enough speed to get through the eye of the wind. They also need rocker to lift their transoms clear of the water. They need transoms because they are so heavy on a relatively short waterline.

    Building a rockerless hull is very simple. Glass 2 full length panels from the sheer (join of hull and deck) down to the waterline on both sides. The keel line is straight, the waterline and the sheer line are both curved. Then butt join the keel edges and lift up the sheers, forming a U shape with a straight rocker. Then squeeze the bows together. The rocker will reverse (higher in the middle than at the ends). You can do this much with a sheet of paper to see what I mean. Then push down on the sheer in the middle until the rocker is straight. This forces the unglassed core below the waterline to conform to the shape dictated by the glass to the waterline. Glass the interior to keep this shape, flip it over and glass the exterior. If this is not clear, get some foam and glass and build a little model (or buy a set of hary plans ;-))

    Derek's KSS works on a similar principle, but he cannot butt join the keels as the keel line is curved.

    Two harry hulls will not make a catamaran. Two long hulls add weight, torque to the beams and windage. You very quickly get on the upward spiral of more weight needs more sail, needs more strength, length and beam, means more weight, needs more sail etc. Harry's are on the downwards side of this, which is why they are so light.

    The Skimmer hulls are the same as all the other cat hulls out there (with the exception of the kit panel boats, but even these are basically the same, just with soft chines instead of round bilges. They are all speed compromised because they have to tack and carry transoms. To see a double ended rockerless hull in action (albeit a non optimised one on an overweight boat with ordinary sails on it's maiden voyage, check out http://www.youtube.com/watch?v=8chR6DAFjGA Boat speed equals wind speed from 10-15 knots. There are very few modern cruising cats under a million bucks which will do this.

    Bryan,

    Look forward to hearing how the Re-e power motors work. They are high on our list.

    regards,

    Rob
     
  14. Bruce Woods
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    Bruce Woods Senior Member

    MMMM so simplistic. Better tell the A class guys their boats are so heavy that they need transoms.
     

  15. masalai
    Joined: Oct 2007
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    Location: cruising, Australia

    masalai masalai

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