Brewer 12.8 centerboard gone

Discussion in 'Stability' started by geoleo, Dec 31, 2013.

  1. geoleo
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    geoleo Junior Member

    :D I recently bought a 1983 Bewer 12.8 hull 6 of 9 . The previous owner got mad at the centerboard and dropped it in the bay at Luperon D.R. He said it slowed the boat half knot when initially lowered, Made thump thump noises all the time, and worse thing the board had a restraining wire that vibrated at speeds over 6kn! This fixed wire was supposed to prevent the board from moving forward and hitting the keel opening. SO now I have a boat with a large cavity at bottom of keel! I believe the opening is 3.5 inches wide X longX2ft high. He also said it only improved upwind beating by 10 degrees. Im not so concerned with beating upwind. However I am concerned with LEEWAY! Next time in yard I must do something with this cavity. 1 Close it up? smooth close up of course. 2. close it up with lead added to forward part of cavity. The missing board weighed 300#. However when I went sailing it seemed very stable in not heeling a lot. 3. add some sort of appendage like a 8-10 inch FG I beam which would have a end plate effect and surfaces to hinder leeway? This would be relatively easy as the top flange of the Ibeam would be utilized to close off the 3.5 wide opening, however the draft would increase the depth of the I beam chosen and the I BEAM WOULD BE VULNERABLE TO GROUNDINGS. 4. Replace the centerboard with a lighter structural foam/Kevlar/epoxy board with a lead weighted tip-- board to be of same size. New board weighs approx. 120# with 40# lead in tip.. Craft a LARS Keel appendage similar to what catamarans use. HELP!!!!
     
    Last edited: Jan 1, 2014
  2. geoleo
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    geoleo Junior Member

    3.5 inches wide X 6ft longX2ft high.. 120bs -not 1200 lbs LOL
     
  3. PAR
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    PAR Yacht Designer/Builder

    I believe we've seen this set of questions previously in another thread? I'm the one that said 10 degrees was a huge lose, as well as making a new board as the easy fix. A different hoisting arrangement is a good idea, as a wire doesn't have to be exposed and really shouldn't be. Why Ted (who knows better) did this, well who knows.

    [​IMG]

    You have sufficient lateral area and cutaway forefoot to get up wind, but the board was installed on the shoal fin to improve windward ability and shift the CLP aft on beam wind and further aft courses.

    To gain (again, as mentioned in the other thread) windward ability and reduce leeward skid, you need effective lateral area, which can take one of to directions - a bard door or a lift derived approach. A lift derived approach means an effective foil that lifts to weather. Your shoal fin offers a little lift, but is limited by it's aspect ratio. The only way to improve this is to add aspect ratio, which is precisely what the board did. The barn door approach uses a massive lateral plane to resist skidding to leeward. The full keels of older cruising boats are good examples of this.

    Your boat could have the area between the fin and skeg fill in, though your CLP will shift aft a bit, so you'll probably need to rake the rig and add some are to the leading edge of the fin too. This is a lot of work, just to save the bother of making another board, plus your maneuverability will decrease dramatically too.

    In the end (again) making a new board, preferably with a more reliable and unexposed hoist, would seem the logical route. Hell just a simple winched cable, attached to the portion of the board that remains inside the case will work. Of course, a nice fitting board with reasonable bushing are required to keep it from flopping around.
     
  4. geoleo
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    geoleo Junior Member

    centerboard problematics

    Its not the hoist wire that vibrates -- there was a fixed check wire that kept the board from moving forward--as I explained in my post. That and the dumb rigged hoisting geometry wherein it takes a 1000# pull to hoist a 300 pound board. Where this hoisting line exits into the cavity cannot be easily changed. :cool:
     
  5. geoleo
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    geoleo Junior Member

    This is one reason I think a lighter same shape board might work better..Albeit one with a pronounced lead weight at the end.
     
  6. PAR
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    PAR Yacht Designer/Builder

    A lighter board may help, but hoisting arrangements don't have to be complex or difficult to operate. I have a 700 pound board on a 23' ketch. The hoist is a straight up pull to a braked winch. The lanyard attaches just above where the board exits the slot in the full down position, which about 2' aft of the pivot pin. The lanyard exits the top of the case, 'rounds a turning block heading aft to the winch, located inside the bridge deck. Simple, easy to maintain and repair.

    The key to good board operation is a good fit in the slot, a reliable and snug pivot pin arrangement and of course a reasonable hoist arrangement. Adding weight to the board brings up other issues, some not easily solved, such as case reinforcement and increased rigging (sail plan) loads.

    The designer of this yacht has had this very question asked previously and his recommendation, if tossing the board, is to add depth to the keel. I'm not sure how much he recommends, but 8" wouldn't be unreasonable, though a foot would be better. You don't need the weight at the bottom, though tossing 500 pounds down there would help a bit and she's tolerate this small amount of extra ballast. The real advantage of this is the extra lateral area and aspect ratio gained. The slot could be used as a "purchase" for the keel extension, saving some engineering issues. I wouldn't bother with an end plate on this keel. A 1,200 pound board is just way over what you'd want to put in that case, without major revisions to the case and all the standing rigging and related attachments (chain plates, tangs, etc.).

    The simple solution is to make a new 300 pound board, maybe with all the weight concentrated in the tip. Personally, I'd locate the weight along the length of the leading edge. This solves the leeward skidding and 10 degree lose of pointing ability issues. A different hoisting arrangement would solve the twangy wire and heavy hoist issue.
     
  7. geoleo
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    geoleo Junior Member

    Hoisting arrangment sketch by Brewer

    As you can see -it is not a straight pull but one turned 90 degrees thru a curved pipe. No wonder its a huge load to move it! Then there is the stop pennant which did all the vibrating. Im not going to comment on this design -however I am stuck with it. What sketch does not show is how much of the board is left within the keel cavity to brace it. Anybody know? From sketch it looks like there is room to 2 part the hoisting line within the keel cavity. A block would be placed at the C/B attachment point and deadended close to where the turning block is. Any Ideas out there?? HELP
     

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  8. rwatson
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    rwatson Senior Member

    I see what you mean.

    Its a bad way of doing it - its sounds like the friction inside the 1" tube is creating lift problems, that and the angle of lift - which isnt on the plan. Its probably only 20 cm at most, not much of an angle.

    I had a boat that simply lifted the CB from the what is your Stop pennant position. It also vibrated underway, but it could be lifted one hand as it had a lot more leverage at that point.

    You may need to beef up the access path, and the cable size, but that is my first impression.
     
  9. PAR
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    PAR Yacht Designer/Builder

    The tube thing isn't all that uncommon and was seen a lot on early 'glass production boats. It's used here, because the exit and first turn of the hoist lanyard are below the LWL. I've not seen this approach on a yacht of this size, as it's more common with trailer sailers, but it does work.

    I dislike a number of things about this hoist/stop arrangement and I'm surprised Ted did this at this point in his career, but I'll bet it's a hold over from the Whitby molds, so they didn't have to change the liner too much.

    The friction is likely a combination of things - a worn out tube, pivot and lanyard binding at the board, etc. A quick check might be to pump axle grease into the tube, to see if this relieves some of the hoist effort.

    As to solutions, well I think this depends on how much room you have above the board, inside the case. If you have enough room for a turning sheave, you could bring the hoisting lanyard back and under the bridge deck, just to turn again and come straight up. It doesn't look like you have much mechanical advantage over the board, so a 300 pound pull, might only be reduced to 150 - 200 pounds and way too much, without a winch.

    I prefer board stops to be physical, rather than mechanical. Simply put, a raised portion of the board that physically prevents the board from dropping past it's full down position (usually landing on a cushion of some sort, built into the case), instead of a lanyard that acts as a stop. Now in Ted's defense, the sole mounted stop tube acts as a cockpit drain, which is clever, but this can remain, without the lanyard.

    This is one of those deals where a good, in person look at the case, liner and other elements are in order, if you want to make significant changes. This may not be economically feasible, so the easy thing might be a new tube, insuring the pivot and hoist lanyard pins are snug and free to move. Lastly a self breaking winch could solve the heavy hoist issue, maybe cabin top mounted. These winches are available and not very expensive.
     
  10. geoleo
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    geoleo Junior Member

    board is gone

    cant experiment with grease as board is 'gone' into the bay at Luperon D.R. The hoist line is still there as is the dedicated Lewmar ST winch and stop /clutch behind it. The cabin top is starting to distort from the strain of the hoist line. I have emailed TED to see if I can get the exact dimensions of the board in order to make a new one.:!:
     
  11. Tad
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    Tad Boat Designer

    What about looking at using the stop pennant pipe for the hoist? Build a frame in the cockpit to take the top of a 3-4 part tackle and perhaps a winch. With spectra the hoist line can be small and the tackle above waterline....maybe.....attach lower end of the lifting tackle to a thick and heavy single line to the board?
     
  12. geoleo
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    geoleo Junior Member

    DOnt want that

    NO clutter up the cockpit floor?? No NO
     
  13. geoleo
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    geoleo Junior Member

    Then more vibrations

    why have more lines there to vibrate?
     
  14. geoleo
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    geoleo Junior Member

    Ted Brewer

    is sending me the drawings of the centerboard. He says that Ft Myers builders did not follow his design on the hoist arrangement. :cool:
     

  15. ftjones1
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    ftjones1 New Member

    brewer 12.8 centerboard pivot pin cover

    greetings all: 1st posting and new member.
    we are in the final stages of rebuilding our 12.8 brewer centerboard. we rebuilt the entire centerboard raising system. most of the welding points were broken and the entire mechanism of shifting inside the cavity and higher in the upper housing section. real pain..

    i have one remaining question. the pivot pin is stainless through bolted with both end recessed inthe centerboard hull. i am unsure how to cover the recess. there are screw holes suggesting an oval cover plate. one suggestion is to skim it with west or maas epoxy. another is to fill the recess with 4000 or 4200 (so it can be more easily removed) and fabricate bronze plates. I am concerned that any trapped water will accelerate deterioration of the SS pin.

    any suggestions or thoughts is appreciated. thanks in advance
    tom jones
    blue trust
    brewer 12.8
     
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