6m low power (10 hp) cat

Discussion in 'Boat Design' started by BrianPearson, Jun 24, 2016.

  1. ElGringo
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    ElGringo Senior Member

    I sure would like to see the drawings for the cross beams and how they are attached. I have talked to a few people and studied all the pictures I can find of cross beams but never really found anything I completely liked
     
  2. Krauthammer
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    Krauthammer Junior Member

    Kurt Kehler obviously prefers beams and netting while Bob Oram went for solid surfaces. Me I'd do a combination of both.
     
  3. rnlock
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    rnlock Senior Member

    El Gringo:
    Why a catamaran? If I've got it right, the "Great American Loop" is almost all sheltered water? If you're trying to keep the budget low, I should think a monohull would conserve your money. Have you checked out some of Phil Bolger's narrow, simple motorboats?:
    http://www.boats.backwater.org/Sneakeasy/ This page includes information about another boat, the Tennessee, which might be fine with the amount of horsepower you're considering.
    A smaller relative, the Sneakeasy might be doable for a more spartan experience. I imagine a bunk and a portable toilet might be accomodated. I have been on a Sneakeasy with several people on board that planed with a 10 hp 4 stroke. It may have been only 8 or 10 knots, but it was planing. There's an alternate version with a modified bow that should handle more chop. Though it's only about 4 feet wide, it feels remarkably stable at rest.

    A slower, lower powered, and more elegant ride might be his Champlain design. However, there's quite a bit of fine carpentry involved, or there was on the example I saw. I was once at a messabout where I saw one or two other monohulls that might be suitable for your mission. But I can't remember any names.

    If you must have a multihull, I wonder if the Bantam would do:
    https://www.flickr.com/photos/hallman/tags/bantam/ planing tri with at least some accomodations

    There are many hundreds of Bolger designs. There are probably some other designs which would also serve. Including, I'm sure, some that can handle rougher water. I think there are some over at instantboats.com

    Bolger passed away, but his widow, Susanne Altenberger, runs the business, or did the last time I checked.
    -------

    If it really has to be a catamaran, because that's what you like, that's as good a reason as any, of course.
     
  4. ElGringo
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    ElGringo Senior Member

    rnlock, I think the Bolger sneakeasy boats are way too narrow, I would want a usable deck for walking around and a motor bike to get me to the grocery stores and for sight seeing. I could lift and carry a motorized bicycle for a short ways, maybe, so I could set it off the boat.

    The Bantam is an interesting looking boat and would work but, an extra hull to build.

    I really do like catamarans for their stability, deck size, and shallow draft. I am positive that if some miracle occurred and my back would let me, I would be on one and gone.

    I'm going to look at Bolger's and instant boats and see what I may have missed.

    Thanks for your input, and anybody else that knows of a boat I may have missed, let me know, and remember that while I will probably have an opinion, I wont have a clue.
     
  5. rnlock
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    rnlock Senior Member

    Actually, the Sneakeasy is the narrowest one. The Tennessee is 6 feet wide instead of 4, and nearly all of that beam can be useable, since the sides are so straight. It's also around 30 feet long, but light. I don't know how much useable deck you need, but the cockpit could be deck instead, If you didn't need the aft storage, the deck could be extended a few feet. There are some similar boats to Tennessee by other people. Check Duckworks magazine (on line). Michael Storer has a couple.

    I can't really argue too much about the deck size, though we should keep in mind that these boats are long for their weight. Which, I'm sure, means they need less power for a given speed.

    Sneakeasy is remarkably stable, more so than other monohulls I've been on. Presumably something like Tennessee or Bolger's Idaho would be even more so. More on Tennessee and variants:
    http://www.ace.net.au/schooner/tenn.htm#start
    I don't know just how much open water is involved in the loop. This sort of boat (and many power catamarans, I'm sure) would require mild weather and caution there.

    As far as draft is concerned, flat bottomed boats without much rocker, like Sneakeasy and Tennessee, have a big advantage over catamarans unless the catamaran is much lighter and also flat bottomed. Unless the catamaran is much longer or has hulls at least half as wide, it's going to draw more water. A hull that's shallower than the lower unit, of course, doesn't help all that much! For that, I understand there's something called a tunnel boat, but I don't know much about them.

    P.S. A catamaran already has 100 percent more hulls to build than a monohull!
     
  6. ElGringo
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    ElGringo Senior Member

    rnlock, I have watched all the video on YouTube of boats following the Loop. Part of it would be going around Florida, several long stretches of open water on the Atlantic side. Parts of the Great Lakes, and the Mississippi River. All kinds of commercial traffic, fishing boats, 30 to 40 foot cabin cruisers with hundreds of horsepower, giant ships, and barges a mile long. Unless you had a pretty big boat, the stability of a 1:2 catamaran would be a better choice by far for a solo trip.

    Lessons learned while touring by motorcycles make me fix, or replace any equipment that gives me any second thoughts.

    I looked at all the bolger boats on the links you provided and there are some nice looking, and some very unusual boats. I'm glad you provided the links because I like to look and think where each boat would be at its best. Back when I had bigger dreams, I needed to dream of bigger boats so I have looked at a bunch of them.
     
  7. bergwerk
    Joined: Jun 2016
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    bergwerk Junior Member

    +1.

    Having negotiated the St.Marys and the Jupiter inlets in a 32ft twin engine I want no repeats in outgoing tide and incoming wave conditions. People have died attempting this in 50+ ft flybridge cruisers. Do a search if you want details.
     
  8. Manfred.pech
    Joined: Apr 2010
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    Manfred.pech Senior Member

    SIX m low power CAT

    Newest development:

    [​IMG]
     
  9. Sailcy
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    Sailcy Junior Member

    Very interesting project. Please keep posting. Eager to see how this hull shape will perform
     
  10. FAST FRED
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    "Part of it would be going around Florida, several long stretches of open water on the Atlantic side. Parts of the Great Lakes, and the Mississippi River. All kinds of commercial traffic, fishing boats, 30 to 40 foot cabin cruisers with hundreds of horsepower, giant ships, and barges a mile long. Unless you had a pretty big boat, the stability of a 1:2 catamaran would be a better choice by far for a solo trip."

    I live in FL , must have missed the "several long stretches of open water on the Atlantic side.". AICW covers almost everywhere except along 40 miles of NJ coast Manasquan to NYC.

    Most of the loop is a snooze , bring an oversized anchor , much is soft mud bottom.

    The loop has been done in the 1950's with small outboards and with Jet Skis and tents.

    If the loop trip is your dream the lowest cost would be a 23ft or so Bayliner IO.

    Car parts fix the motor , the fuel burn at idle is minor (much is speed restricted to 10Klicks , about 6 mph.

    The boat with a trailer should cost $3,000 to perhaps $7,000 , and if you clean and paint on your voyage you will easily have a ZERO ROUND TRIP.

    What you paid for the boat should be less than you sell it for , if its neat clean and pretty.

    Bon Voyage!
     
  11. ElGringo
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    ElGringo Senior Member

    I think the danger of any trip is probably relative to your experience. I have lived in the desert of the Texas Panhandle most of my life and what you guys call crossing the bay is open water in a hurricane to me. Some of the video I watched had rough water, rain, fog, and poor visibility that kept the people tied to a dock for several days on the east coast.

    Doing the loop with small outboards and jet skis works when you're 20 but very few in their 70's would try it.
     
  12. bergwerk
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    bergwerk Junior Member

    I'm with you ElGringo. People row across the Atlantic too but I'd prefer a fully crewed maxi.
     
  13. rnlock
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    rnlock Senior Member

    I think if you want a safe boat in a hurricane, you will need a heavy steel boat that barely floats, brought ashore and sheltered in a cave! ;-) (Cave to be well above sea level.)

    My intuition says that if you have a solid deck between the hulls of a catamaran, things will get exciting, or at least uncomfortable, as soon as solid water starts hitting the deck, whether from above or below. I think that means you'd need a relatively large catamaran for rough seas, though I could be wrong. A Hobie 14 is pretty good in rough seas with a normal load, but that wouldn't be much good for you on your trip! That hull shape might be good if you were going large enough. I noticed that, at least in small chop, the ride was surprisingly smooth even when going moderately fast, perhaps due to the relatively small waterplane area, or whatever you call it. However, on a heavier cat, with wider, flatter hulls, I suspect the ride wouldn't be as smooth. Also, if you have a lot of initial stability, in large waves, I've heard the boat will move more quickly, possibly throwing you around. Some people really prefer the relatively level attitude compared to a monohull sailboat, but that doesn't seem relevant under power.

    The following is predicated on Fast Fred's comment about speed restrictions.

    If I really wanted to do a trip like this on a low budget, I'd probably look for a used twenty or 25 foot centerboard sailboat with reasonably shallow draft. If it's a popular model, the rig and sails might be sold to recoup some of the cost*. Around here, old sailboats that need some cleaning up sometimes go for ridiculously low prices. Like this one:
    http://boston.craigslist.org/bmw/boa/5716009031.html
    The centerboard is for shallow draft. Sailboats have displacement hulls, so at slow speeds they're likely to have a smaller wake and use little power. My impression is that they'll deal with larger seas than a typical motorboat. I remember being in a 30 foot sailboat on a very rough day on Lake Champlain. We were just fine, although steering took a bit of work. The boat wasn't rolling much because of the sails. We even stayed dry. The only other boat we saw on the water at the time was a houseboat of about the same length, which was slamming into the waves and covering itself with spray. BTW, in the summer, Lake Champlain is really nice most of the time. Great views of the Adirondacks, too.

    If I was going to build something inexpensive for a trip like this, and I was worried about rough weather, I might choose a big plywood dory. Perhaps a St. Pierre dory. But I think that's overkill. Caveat: the only one I've ever seen in person was being built by a neighbor when I was 4. I saw it on the water, too, but never had a ride. In real life, I probably wouldn't build anything this big, and if I did it would have to be a decent sailboat too.

    If I really had to have a catamaran, and I was concerned about rough weather, I might start with one of the Wharram designs, and leave off the rig. Some of them are like two anorexic dories fastened together, which I'd guess makes them relatively simple to build. However, I think you'd find the accommodations a bit spartan, and the deck smaller than you'd like unless you like walking on a net. If you made a solid deck and bigger accommodations, I think the seakeeping ability would be reduced. But again, I think a standard Wharram cat of reasonable size might be overkill. Caveat: the only Wharram cat I've seen in person was one on Lake Champlain that I caught up with using a Windsurfer.

    Absent the speed restrictions and the desire to sail, I'd probably go with something similar to a Sneakeasy or a Tennessee.

    *A reefed sail might be good for steadying the boat in rough water, but probably a shorter mast and smaller sail would do.
     
  14. Manfred.pech
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    Manfred.pech Senior Member

    Progress for low power catamaran:

    [​IMG]

    [​IMG]
     

  15. ElGringo
    Joined: Mar 2014
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    ElGringo Senior Member

    How critical is the alignment of the hulls? and what would happen if they were off say !/2 inch in or out at the front.
     
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