bluebird 22 sailboat swing keel conversion

Discussion in 'Boat Design' started by whitepointer23, May 17, 2013.

  1. whitepointer23

    whitepointer23 Previous Member

    I have a fiberglass bluebird 22 fixed keel yacht. aussies on the forum are very familiar with them. I got the boat cheap and want to convert it to a swing keel for the lakes I sail on. the keel is a bolt on job so I am thinking remove it and get a solid aluminium center case made which will bolt to the keel . I would like to your ideas and experience with this type of thing. google bluebird 22 association to see the boats. I don't plan on racing so am not bothered about class restrictions. there is one on gumtree that has been converted but no photo's of it. can I make a swing keel out of plate steel and round off the edges or will it need to faired to a foil shape.
     
  2. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    You can definately make a swing centreboard from flat plate, many boats have them, she will of course be tender, but still very sailable.
    From the profile of the underwater section of the boat, make a cardboard cutout.
    Balance this cutout piece of cardboard on a rule, so as to determine the balance point of the underwater section of the boat (CLR Centre of Longitudinal resistance), try as much as you can to reproduce this point with the new underwater section that you will create with the centreboard in the fully down position, that way she will sail as the original boat did (subject of course to being far more tender as there is no counterweight anymore). Not hard to do mate. All the best, John
     
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Making the board portion of the setup is the easy part. Making the case, so it doesn't leak, will be the real test. Since you have the 'glass version, you should strongly consider a 'glass case, not a bolt on aluminum sort of thing. If well designed and laminated, you'll have a continuous bond, that can't leak. Also find out what the ballast is, even if it simply means weighing what you cut off. You can still have a plate board, but it would be best to have ballast attached to it's lower leading edge.

    Assuming what would be typical for a boat of the original's arrangement and era, you'll want about 1,000 pounds (453 kg) of plate with ballast attached. Leaving this off wouldn't be a wise thing to do. She'd likely get knocked down pretty easily. This assumes about 30% in ballast ratio, which would be typical of a boat shaped like that and of it's era.

    Simply put, a hunk of plate just will not do. For example, lets say you employ a 6' (1.8 m) long by 18" (.45 m) tall plate (some stays inside the boat) for your centerboard (about right on that size boat). This is about 92 pounds (42 kg) of 1/4" (6 mm) plate (depends on what type of steel). This is less than a 1/10th of what you need. Even if you use 1/2" (13 mm) plate, you'll still need over 800 pounds (370 kg) of additional weight to get her to float on her lines and not flop over with a modest gust.

    Making friends over at the class association and get the actual ballast figures, would be the logical route. Lastly, the board will need to pivot and a ballasted boat will need a really stout pivot. This is easier said than done. You might consider a stub keel, to house a portion of both the board and the ballast. This relieves the pivot pin of some of it's burden and allows you to carry a thinner/lighter board.
     
  4. whitepointer23

    whitepointer23 Previous Member

    thanks john. I thought if I used thick enough plate to keep the weight similar to original and made the keels extended position match the fixed keel . what about lifting and lowering. boat trailer winch I guess, but do sk's have an arm or something that the cable attachs to and what about a locking mechanism to stop the keel coming back in a knockdown.
     
  5. whitepointer23

    whitepointer23 Previous Member

    thanks par, these boats are 1.5 ton disp so I think your figures are pretty close. no internal ballast. I was thinking 1'' plate but I have not looked into weights yet. and 1,1/2'' pivot on Teflon bearings. I have met some association members who are quite happy to share info as well. how do you work out the extra ballast if you had 500kg under the boat and changed to 300 under and the rest in the bilge. can you calculate that or just add lead with the boat in the water till she sits on her old marks.
     
  6. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    I go past a trailer-ed Bluebird without a fixed keel if I drive to work, it's got a for sale sign on it & might be the one.... might be worth ringing the bloke up for a chat.
    Jeff.
     
  7. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    A sub keel would be my choice. This would be positioned around the centerboard slot, faired to the hull and also given a reasonable streamlining. Even a 1" plate still has you coming up 640 pounds light. A 1" plate is a huge piece of steel and the case would need to be massively reinforced. The stub keel could help in this regard, being say 6" below the belly of the boat and probably needing to be at least 8" - 9" wide. This could easily carry the extra weight's volume.

    Post some pictures, so we can have a look at the lateral area and rocker. Have you priced up a hunk of plate this big yet. You might consider another material when you do. 316L stainless in a 1" thick 18" x 7" piece will be in the $4,500 range (retail). 304 will be about $4,000. Even mild steel will be in the $1,500 range.
     
  8. whitepointer23

    whitepointer23 Previous Member

    if it is on a red tandem trailer it is the one I saw advertised. I can't find the ad any more.
     
  9. whitepointer23

    whitepointer23 Previous Member

    tried to post pics off ebay listing but didn't work. the boat is 8 hours away until I bring it home, can post pics then . the stub keel sounds good, also I have found a Hartley ts21 steel centerboard cheap.
     
  10. waikikin
    Joined: Jan 2006
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    Location: Australia

    waikikin Senior Member

    If I drive in I can stop & get the number if still there, on Darley St/rd Leichcardt. It was definitely a Bluebird hull & had a skeg keel back to the transom.
    Jeff.
     
  11. whitepointer23

    whitepointer23 Previous Member

    thanks jeff, that would be excellent. I remember the ad said leichcardt so it must be the one .
     
  12. waikikin
    Joined: Jan 2006
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    Location: Australia

    waikikin Senior Member

    Hi WP23, I stopped by on Fri, no ad up on that boat anymore(sometimes the council don't like goods for sale on the roadside or they decided to keep it) unfortunately it started to pour just as I pulled up, didn't want to lay in the gutter to check the setup. Seem to remember that boat on ebay or gumtree too.... I think they were after a fair bit for it. All the best with yours.
    Jeff.
     
  13. waikikin
    Joined: Jan 2006
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    Location: Australia

    waikikin Senior Member

  14. Petros
    Joined: Oct 2007
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    Petros Senior Member

    That is a nice looking boat.

    I would consider a dagger board rather than a swing keel. The dagger board is more efficient (better performance) and easier to make, and you do not weaken the hull as much since the cut-out is much smaller.

    I like PAR's idea of the weighted stub keel, but with a fiberglass or even wood dagger board to go down though it. You can make the dagger board foil shaped out of lighter weight materials so it will be much easier to handle. when needed it will go deeper into the water and produce much better pointing ability and less drag than a steel slab center board.

    The dagger board is easier to make, lighter, simple with little/no moving parts, not being weighted it will be easier to remove and stow or handle without a winch. And it performs much better, without the large centerboard slot it will be more efficient. making a foil shaped dagger board from fiberglass or wood is a relatively simple matter. the heavy weighted stub keel will be fixed (no moving parts) and offer you no maintenance issues and give you some balance and control of the boat even with the dagger board full up. There will be no change in the height of the CG, unlike a weighted center board. The risk of leaking of a dagger board case is much lower and it is much simpler to build. And if for whatever reason someone wanted to return your boat to the original keel, you can do this without any harm to the hull if you use the same mounting locations for the stub keel as the original fixed keel.

    If it were me I would install a shallow draft weighted stub keel on the same mounting location as the original keel, and add a deep high aspect ratio foil profiled dagger board through the center of it.
     

  15. whitepointer23

    whitepointer23 Previous Member

    You wouldn't believe it but while contemplating what to do with the bluebird i was given an investigator 563 trailer sailer hull. It has a 50 cm stub keel with 320 kg of lead in it plus a dagger board which is housed in the keel.
     
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