Mini J Class

Discussion in 'Sailboats' started by Tim Judge, May 28, 2010.

  1. presuming ed
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    presuming ed Junior Member

  2. ryanmarr
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    ryanmarr New Member

    The R's are basically small J's but not as small as these boats you've mentioned. It looks like a fun boat to cruise around on single handed.

    We have a fleet of R's at our club.

    Lakeontariorclass.com
     
  3. rcnesneg
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    rcnesneg Senior Member

    I don't know how we didn't find these earlier, they are basically exactly what we're looking for. They come in three sizes too: 12.6 ft, 13.5, and 16.4.
    They have 187 lbs, 264 lbs, and 661 lbs of lead ballast, respectively.
    Sail area is 53.8 sq ft, 53.8 with a 53.8 genny, and 86.1 sq ft with a 107.6 sq ft genny, respectively.

    http://smallclassic.no/


     
  4. Doug Lord
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    Doug Lord Flight Ready

    Wow! Great find!
     
  5. ahg
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    ahg Junior Member

    rustler 18 with straight keel and center board

    good afternoon
    after wondering around the net for a few days looking for information on boats building, I found this thread and decided to register in this great forum
    I have a project to build a wooden sailboat, around 17-18 feet, straight keel to facilitate its transportation, and classic look.

    When reading the thread, I went into the rustler web page and I though had found exactly what I was looking for:
    I would like to build a rustler 18 with straight keel and center board

    I have everything to learn about boat building (probably I said already a few stupidities in the above sentences) but I have the intention to take my time

    I would appreciate some advise to start:
    Is it possible to design your own plans?
    Can a good software help for that?
    How long can it take to build such a boat?
    Is it a question of being motivated and skilful, or that is not enough and I am targeting too high?

    I live in West Sussex not far from some of you guys.
    Are there places in the area worth visiting or people worth talking to

    Thanks in advance for any advise
     
  6. rcnesneg
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    rcnesneg Senior Member

    What do you mean by a "straight keel"? Do you mean just a traditional keel like the Rustler 24 has? What do you mean with the centerboard? These boats are meant to be heavily ballasted, and in order for them to sail properly, you have to have a lot of weight down low, usually a little less to about half the weight of the whole boat, so if the boat weighs 350 kg without ballast, it should probably have around 200 to 400 kg of ballast underneath it. A lifting bulb keel on a winch would probably be a lot better than a centerboard. You could also consider a swing keel, but I think it's a lot easier to screw up really bad on a swing keel.

    I've had reasonable success using Free!ship to design boats, but nothing cutting edge. As for how long to build a boat like that, if you want it in the same quality as the Rustler 24, but only 18 feet long, probably 600 hours or so is a rough guess. Could be more depending on the detail level.

    Skill is nice, but motivation is definitely the most important, along with financing. If you're motivated, you can do anything, it just might take a long time or cost a lot.
     
  7. ahg
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    ahg Junior Member

    Thanks for your answer, rcnesneg
    My terminology comes from a Spanish English nautical dictionary, and is probably not the best. I am Spanish and know the terminology in my language
    By straight keel I mean a keel that does not go deep below the water level. I was hopping it would be possible to build a boat similar to the rustler but with such a keel and a removable rudder plate, and a ballast (that I was calling centerboard) that is as well removable. I will need to bring it in and out of the water quite often, and thought that would make things easier. But that might not be technically possible for a boat of that weight. I thought, probably mistaken, that if my 70Kg Snipe could handle a removable centerboard and rudder plate, a much heavier wooden boat could as well.

    Thanks for the software tip, and for the time estimation. Seems resonable to me 600 hours. It might mean a couple of years, which is fine. I am not in a hurry. What I am looking for is building a boat, not having a boat built!

    Any additional comments/advise on the above would be welcome

    Cheers

    Alejandro
     
  8. rcnesneg
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    rcnesneg Senior Member

    Ahh, That makes sense. I think it would be simpler to design it with the fixed solid keel under the boat, but you will have to have some way to get it deeper in the water to launch, and if you are at all challenged with draft in your area, the lift keel is a must. I would recommend something where you can raise the keel straight up, like this:
    [​IMG]
    or with a bulb on the end that is pulled up right against the hull. When you're trailering though, lower the bulb so that it rests on the trailer and isn't pulling on the boat.
    [​IMG]

    So your design might look something like the F class Firefly (J class yacht with a redesigned belly and fixed deep fin keel and rudder.)

    [​IMG]
    [​IMG]
     
  9. ahg
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    ahg Junior Member

    Thanks rcnesneg. All that is very helpful indeed
    Beautiful the F Class Firefly. I just need to shrink it to 1:6!
    I guess I have to make some research on technical solutions for a lift or removable rudder plate for that shape of poop.
    I was wondering if there is some rule for the ratio between the LOA and the LWL. I imagine that the shorter the boat the smaller should be the LOA/LWL ratio?
    Even from an aesthetic point of view I think I prefer when the poop comes out of the water with a slightly bigger angle
     
  10. rcnesneg
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    rcnesneg Senior Member

    I don't think it really matters at all. More overhang means more weight you gotta carry around, but I personally prefer the overhangs from an aesthetic point. A lot of the point of these boats now is to look pretty, and I think most of that comes from the overhangs, wood trim, sleek beautiful lines, etc. If you take away the overhangs, you might get a bit of performance in some way or another, but you lose the appeal of the boat.
    These smaller yachts are good examples of what I'm talking about.
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    The original purpose for the overhangs is to basically cheat the racing rules. They limited the LWL but did not limit the LOA, so the clever boat builders would build boats that hung way out over each end. These boats are designed to sail to windward heeled over a lot- anywhere between 10 and 25 degrees, a lot more than most boats. When they would heel over in strong wind they would dip the long sides of the overhangs into the water, making them effectively longer, and therefore were faster. Also note that the sail plan tends to be a bit farther forward than you'd expect, to compensate for the extra weather helm from the boat heeling over, and to make it more controllable upwind.

    Look into the Scandinavian Cruiser 20. It seems like a fairly decent boat design, although it relies on crew weight for a major portion of the righting moment of the boat, and I've heard bad things about the build quality. It has the lifting bulb keel and some sort of retractable rudder.
    [​IMG]
     
  11. ahg
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    ahg Junior Member

    Thanks for the pictures. It is good to see examples. Much easier to progress towards the idea of what one wants to build.
    Agree that the overhang is what makes these boats beautiful. It is just that I guess the smaller the boat, the more overhang has to be sacrificed?

    As it stands now, I like the lines of the Dragon or the Rustler 24, but like the ideas of the Scandinavian Cruiser 20 for everything below the water level.

    Although the 29 foot of the Dragon are tempting, even the 24 of the Rustler seems unreasonable for me: I have not that much space in my backyard to afford blocking it for at least two years (....well, that is not me talking, but the outcome is the same!), and the weight probably will end up being an issue to handle the beast, so 20 foot should be an absolute maximum for me, with 18 foot being a more reasonable choice!

    Any rough guess of the weight of a wooden hull 20 foot long and 6 foot wide, before adding the ballast?

    How do these boats solve the issue of the water coming into the cockpit? My Snipe (Fiberglass) has the floor of the cockpit above water level and a hole in the middle. Can a wooden boat be built with the same idea?

    Another question I ask myself is about the relation between beam and stability. For hanging like a monkey on the sides of the boat I already have the Snipe, and by the time I finish this one, I will be in my fifties, so I want something that can be sailed in a relaxed way, and I will certainly not be in a hurry, so speed should not a mayor driver for my design (I guess this is the kind of comment that one might regret in the future?!)

    So, if I make her (beautiful Anglo-Saxon habit of talking about boats as if they were women!) fatter (I just ruined it!!), will she be more stable? Or this is achieved mainly by the weight of the ballast?

    Too many questions. I just downloaded “Elements of Yacht Design” by Norman Skene (not under copyright anymore) and bought a couple more books, so hope to be better instructed in a few months.
     
  12. Jammer Six

    Jammer Six Previous Member

    Avoid appendages on the keel. They kill the ability to point.
     
  13. rcnesneg
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    rcnesneg Senior Member

    Something I've noticed quite a bit as these keelboats scale down, is that they get wider relative to the length as you get smaller. If you made a scale model of the J class that was 18 feet long, it would be somewhere about 2.5 feet wide. Instead, the small boats around that size are running more along the lines of 3.5 to 4.5 feet wide. On the smaller boats, more of the stability comes from moving the crew, and the wideness of the boat itself instead of the weight of the keel. I don't think you should have too much trouble with a bit of a larger boat. There's a fellow that lives near me that has a SeaCrown 25, it's a beautiful boat with a big drop keel, long and narrow, with generous overhangs. He always does everything solo with just a dog to keep him company. That boat probably weighs 1500 lbs easily, maybe more like 2000. An 18 footer will probably end up around 900 lbs, with probably 400 of that lead keel.

    The solution is simple for the bigger boats, make it so the cockpit floor is above the water line, then just have a drain pipe from the bottom of the cockpit out the bottom, so water runs out. Make sure the cabin hatches are closed if you are burying the rail. You've got to put the thing all the way over to 60 to 70 degrees before water starts coming in the cockpit, so I don't think it's that much to worry about unless you're sailing in 10 foot breaking waves and 50 knot winds.
     
  14. The Q
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    The Q Senior Member

    I am involved with several classes with a lifting rudder. If you don't need to steer when the rudder is lifted then is just a box which is a little wider than the rudder , dropping into a slot in the hull. the slot being built like a dagger board case.
    However if you need to steer with the rudder partly lifted then you need to build the box in a triangle shape so that when partially lifted the rudder can still turn 45 degrees each way. and of course the hull opening has to be a similar triangle shape.
     

  15. ahg
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    ahg Junior Member

    That is what I had in mind, but I am afraid I might regret if I don`t foresee the rudder to work while partially lifted. The area where I will sail is subject to 4m water depth changes due to tides, the minimum water depth being sometimes less than half a meter.
    I was thinking on a pivoting rudder plate, but I don't know how reliable that can be. Can it stand the forces involved? I know light small sailboats like the 4,70 use them but in a boat of the size and weight what I have in mind might be a nonsense?
     
    Last edited: Jul 11, 2015
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