Drop keel or repair swing?

Discussion in 'Sailboats' started by saltnz, Feb 28, 2010.

  1. saltnz
    Joined: Feb 2010
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    Location: New Zealand

    saltnz Junior Member

    Hello
    I have a 22 foot trailer yacht that is very popular in my country. Over the winter I am planning to give her a bit of a refurbishment. One of my main concerns is her swing keel. I just do not know whether it is worth repairing or replacing with a drop keel.
    She has a steel skeg that is the platform (with studs protruding) for the centercase (an inch wide steel strap lattice claded by ply) is bolted to the studs. The Keel is 150 -190kg (class measurement) and steel wrapped in glass.
    Anyway I suspect all is not well with the pivot she points better to port than starboard so I have to pay attention to my keel this winter(Sth Hemisphere). However looking at the center-case in general is a bit of a concern. She is not a new boat and much of the steel lattice is very corroded and some is warped mostly to the rear of the center case.
    I think the whole center-case needs to come out and be repaired/replaced and that in itself raises lots of concerns for me. That seems like an expensive project and wondering whether is is worth considering switching to a drop keel.
    I was wondering if I could get some advice on where I could start looking at some example designs and just to gain a perspective on what I should do. I am considering consulting a boat builder, but really want to gain a better understanding about what exactly is involved with either project
     
  2. souljour2000
    Joined: Aug 2009
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    souljour2000 Senior Member

    - Any pics of your boat and the keel system in question would be very helpful in the possibility of the forum being of any assistance to you...
     
  3. saltnz
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    saltnz Junior Member

    Sure give me couple of days and I will post them
     
  4. saltnz
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    saltnz Junior Member

    Hi see http://noelex22.org/specs.html for specs. Sorry about these photos it is very hard to see what is going on (It looked okay when I took them). When I was getting these photos I ran into a boatbuilder who had previously owned one of these. He suggested I need the remove the steel structure from within the centercase and that could be sandblasted, hammered back into shape and re galvinised and the rebuild the centercase. His guestamite was quite a bit more than what I paid for the boat, but alot of the cost was time the time involved getting out all the steel which and I could do it for considerably less myself.

    With all that work which includes removing a lot of the structure I am wanting to find out more about a daggerboard and centercase. I have done a bit of research I have found some photos of people who have done these conversions on these boats, but there is no plans or very little text. And I have a lot a questions about the amount of leverage involved (150kg) in the stock and would that not cause compression on a wooden keel with a lead ballast at the tip? Knowing what materials to use is also the start of trying to figure out the cost

    Of course I am just thinking about it for now first step is to drop the existing keel (in a couple of weeks) and get a better look about what exactly is involved in extraction of stuff that has to come out.

    Anyway here are the photos I am not sure if you can even make out the structure round the pivot but the member on the port side is a bit warped as is the member to the rear (very hard to see in photos). The keel is very rusty and I suspect that water has flowed down from the top aft edge of the keel and caused it to swell because it is encased in fiberglass. The last photo shows the centercase from the out side as you can see it is bolted to the sole after having a very close look at it I do not think the skeg is steel afterall (the guy I bought it from told me that he thought it was steel) so those studs just must be set in the fiberglass (I guess I will find out). Although you cannot see it the part of the mast support is integrated into the front of the centercase and pivit support and I can see no way of removing that without cutting it out of the mast support


    IMG_1887.JPG

    IMG_1886.JPG

    IMG_1892.JPG
     
  5. souljour2000
    Joined: Aug 2009
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    souljour2000 Senior Member

    Hmm....that don't look like nothin I ever seen in the world of swing keels...not that I am a long-time traveler of that world...but I look at alot of stuff online...and I don't know what's going on in there or what i'm really looking at from the pics...maybe someone else will come across your thread who knows something of Kiwi boats...What about that association page...anyone on there who can help?
     
  6. fng
    Joined: Feb 2009
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    Location: new zealand

    fng Junior Member

    I have seen a noelex 22 with a virtical dop keel and bulb. I would pay to check with the class association to see if it will be legal if you intend to race it. Cost really depends on on how much you can do yourself. You would be lukcy to get it done for under 8k nz professionally.
     
  7. saltnz
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    saltnz Junior Member

    Thanks I have not made up my mind yet I am trying to gather some information about what is exactly is involved.
    I am not intending to get the work done professionally, I have previously helped build a GOP trailer yacht before and have access to some pretty good resources (people and benchtools). I may well need to enlist professional help, but hoping I could accomplish much myself
    What I am uncomfortable with is trying to guess what would be suitable design would be (If I went down that path)
    I have seen some photos from the association website that look pretty good, but no plans for the centercase. I was hoping there was someone who could direct me towards a plan, information or share experiences of a similar scoped project. I have tried to get some help from the association in the past but have only really got access to photos. I would post them, but I feel I might upset someone without prior permission.

    I do see a benefit on converting to drop keel, I think swing keels are messy , clumsy, not very watertight, subject to swelling early season lowering problems and require a lot of to maintain. Yes it could cost me quite a bit of time and money, but if I have to go to the extent of removing all that rusted steel from my existing centercase that is also going to cost me more time and money than i would like to part with anyway.

    So I want to make the right choice, not the romantic over-ambitious project choice, nor waste a lot of effort repairing existing system if for not much more i could get a better system
    I see these 5 major pieces to the puzzle

    1 A lifting mechanism (Straight forward enough)

    2 A center case/ support structure for lifting mechanism. Looks pretty tricky but do-able fabricate out of steel or maybe someone has some other ideas.

    3 Fill up the rest slot that was used for swing keel (timber and glass)

    4 & 5 are the ones that I am most concerned about

    4 Someway to deal with the leverage force from a ballasted keel
    In the photos i have seen there appears to be some kind of block/stock about the width and height of a shoe-box fiberglassed to the bilge through which the centerboard passes. I am guessing that helps spread the leverage and keep it nice and snug. Wouldn't you need some way of dealing with lateral forces here? In those photos there is a ply floor secured from the top of this block to the lockers, that does not look ideal. This piece is something I really need help with.
    First considering the stresses exterted here what kind of material can you make this out of? I am prepared to get this prototyped by a pro if reasonable.
    Second how do I work out the optimum dimensions of the block?
    Third how much reinforcing is required?

    5. A new ballasted keel. Looks like a lot of work but I have seen details and have template for a lead ballasted tipped timber keel encased in glass one. Looks straight forward enough but I am concerned that the timber would compress from the forces of leverage.
     
  8. saltnz
    Joined: Feb 2010
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    saltnz Junior Member

    Help still needed

    Hello
    Hoping someone will be able to offer some further advice or stop me if I am going down the path. An outing in heavy weather has forced an early retirement for the season and early commencement of my winter restoration project. I think that I have made up my mind to convert to a dagger-board but that is another story.
    In my searches I stumbled across another guy who is trying to do the same thing so there are two of us struggling to find more information
    I managed to make contact through another local club and took a look at someone who has done this conversion. This visit has made me think I was over thinking everything a bit and that it was not as hard as I was thinking. But I am still really concerned about the pressures put on the trunk by the leverage forces applied with a 150kg+ ballast when heeling over. The guy I meet was a fitter and turner by trade and said he did everything by eye and did not work off any plans, but I do not feel that confident. I am OK about the design and work of the keel itself, but would really love it if someone could provide further guidance or plans from similar project. I still have real questions about where the top of the center-board seats into the centercase/trunk. I have seen a few photos and examples where the top of the centerboard seems to be nicely squared out to fit snuggly, but then I have also read that there needs to be about 3mm clearance and would that not cause the keel to wobble?
    Anyway enough of my moaning here is what I managed to glean off this guy.
    He made his keel out of stainless steel sheets welded together, but he would not recommend doing that, but build it out of wood with lead at the bottom.
    You might be able to make out that he has a steel attachment to the front of the centerboard that acts as a guide and helps prevent movement (What I am really worried about), but he would not recommend tapering it as he has and I really wan tot get that aspect right
    He has positioned it on a very slight angle, but he recommends not doing that and I agree with him not to make things too complicated
    As you can see in the photos he has a single stainless track to guide the keel up with, I was thinking about having one at the back to help with stability/ locking in the keel.
    He has also used a single piece of hardwood to fill the gap left by the slot and included in the trunk, he recommends this piece of timber going all the way through the bilge and hull and scarfing it from the bottom.

    His workmanship was excellent it was a very tidy job and beautiful in it's simplicity. His experiences helped me make up my mind and ease it as well. However I am am still worried about making sure the keel is fixed and will not wobble and really love some help with this aspect

    Thanks
     

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  9. tspeer
    Joined: Feb 2002
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    tspeer Senior Member

    When you design your case, be sure the top of the case is high enough to be above the waterline (plus margin for waves) when the boat is fully loaded and crewed, sitting in fresh water.

    Don't ask how I know this is important...
     
  10. jumbuck
    Joined: Apr 2010
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    jumbuck Junior Member

    I am a great believer in swing keels after seeing the damage caused to two trailer sailers with lift keel systems (slide straight up and down) after going aground.

    In both instances major hull and structural damage was the result. I won't go into details but thankfully nobody lost their life.

    If they had swing keels the keels would have simply swung up under impact.

    I don't want to start a debate on swing vs lift but from a safety stand point I know which one I feel more comfortable with. No question.

    Cheers for now.
     
  11. jwboatdesigns
    Joined: Apr 2010
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    Location: Hamilton New Zealand

    jwboatdesigns John Welsford

    Noelex 22 keels,

    Where do you sail ?

    John Welsford
     
  12. yipster
    Joined: Oct 2002
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    yipster designer

    funny story's

    but be warned, every time you draw a leakproof 3d design in virtual water its getting water in :D
    making a hull bolean in the water gets the hull dry inside inside but keeping it dry
    while the virtual boat moves through the also virtual water the bolean has to follow the same path, hmm..

    bolean = cutout in 3d design
     
  13. saltnz
    Joined: Feb 2010
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    saltnz Junior Member

    Drop keel or repair swing/Still need lots of help

    Hello everybody
    Thanks for all your responses. Very impressed to see John Welsford reading this, I am in Wellington JW, love to hear any of your suggestions.
    Not quite sure what virtual water is guessing it is a CAD program might need to have a further look. Centercase waterline, I hear you, but a bit too far in the future, but will need to worry about it later, and finally I have read plenty of discussion about swing vs drop and lets not start a debate if I could have easily fix my swing I would have, but I would need to basically do everything again almost from scratch and feel in my case daggerboard is the way to go if only I could get the design sorted

    Here is another long post I hope this does not put anyone off reading it

    I have been busy removing old keel (what a job). Hired a hoist Thursday before Easter, but could not get pin out of keel. I cut a sample out of the trailing edge of the keel and water was obviously flowing down the 3/8ths steel plate core corroding the steel leaving 1-2mm of corrosion between the steel and laminated ply and lead and causing the whole thing to expand. Long story short came to the conclusion the keel was toast and ended out cutting it out with a sabre-saw and grinder (trust me it was totally stuffed)
    To further cut another long story short, I was not impressed but the accuracy of how the existing centercase and integrated mast support were built either. The geometry is way off, which has further discouraged me from trying to repairing and leant me further in favour of a daggerboard. I am well aware of the damage that can be caused by running aground, BUT I intend to be steaming in shallow waters and I can always buy a depth sounder.
    I have been discussing my problem with one of my crew, who is a joiner (and has a Welsford) and we have come up with a rough plan I would like to bounce off everyone. This plan has not even considered how we are going to deal with sealing water through the center-case and making a mock up of the keel and lifting structure before I commit to anything.

    Keel
    Intended dimensions of keel Height 1350mm, width at widest part of NACA 74mm, length (I think this is called cord) 600mm
    Currently making mockup out of 100mm*50mm pine
    Make a lamented keel out of Kauri (JW would this be a suitable wood to use in NZ?) use router profiling to shape get the ballast (170kg) cast, use 2 threaded stainless 3/8th thought the entire height, to bolt the 2 parts together then glass all up. Keep the 200mm -300mm of the leading edge square and some of the trailing edge square (still to figure out dimensions of space needed for lifting block and tackle, but that is what mock up is for) maybe use a low friction material here. I am pretty comfortable with this at the moment plenty of information about how to shape and cast, not so much on reinforcing with so much ballast hints appreciated

    Centercase/Trunk
    Intend to make mock up out of 3mm ply
    Considering getting 80mm Stainless (316) square tube by 3mm thickness. I need to speak to the suppliers about whether that 80mm is measurement inside or outside, because my plans rely on the 80mm being measured on the inside. Cut in half length-wise so I get 2 U shaped tracks 80mm*40mm bilge to cabin ceiling and have the square part of the top of the center-board slide up and down these tracks. Because the top square part of the board fits so nice and snugly this how I intend to deal with the board wobbling and with lateral reinforcing deal with the forces of leverage when healing over (at- least on the leading edge track). Weld to 2 tracks together with (316) angle iron and use existing bolts on bilge to fasten to bilge, weld fastenings for lateral re-inforcing to deal with leverage when healing.
    So in a nutshell I have a 2 tracks joined together by angle iron at the bottom and top. The square edge of the centreboard is a snug fit and all stresses are dealt with in these tracks. IE the square edge of the board and square shape of the track prevent wobbling of the board. Leverage forces are dealt with because it is bolted to the bilge and there is lateral reinforcing where the very top of the board is when fully down. Please give me some feed-back here.
    The big problem I see with this is it could be very leaky, I have not even considered how I am going to clad it for form the case part or whether to use sealant or epoxy where the structure is bolted to the bilge
    I would love to see plans of another ballasted daggerboard case, but google has not helped me at all there

    So I have some new photos now the centreboard is out. The first one shows the existing structure. If you used your imagination you could get an idea of what I am proposing for new centercase. You can see an existing track welded to angle irons bolted to the bilge, just imagine it is made out of stainless the tracks extend to the cabin ceiling and the angle iron only extends to the aft track around 600mm. The second photo show the same structure but the is included to draw your attention to the ridge of fibre glass ridge that forms the base to the existing structure I was thinking about maybe filling in some of this void to give strength. And finally the is a lump on the other side of the hull that appears to be made out of glass reinforced ply wood, which needs some attention because the keel has been rubbing on it and the plywood is exposed, you might be able to make out the damage in the first photo. The distance between the bottom of the hull and the top of the fibreglass ridge is about 90mm if my memory serves me correctly
     

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  14. Cheesy
    Joined: Aug 2008
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    Cheesy Senior Member

    The 80mm RHS is an outside dimension, instead of buying a length of that it may be cheaper going to a sheet metal place and having them cut a piece of sheet and fold it into a channel section for you
     

  15. saltnz
    Joined: Feb 2010
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    saltnz Junior Member

    Thanks Cheezy. I guess that is my only option I was think 80mm is not enough and was basing the width of my keel based on that dimension means I have more scope

    Ta Muchly
     
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