Improving the design of a Hartley TS21

Discussion in 'Sailboats' started by jumbuck, Mar 14, 2011.

  1. jumbuck
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    jumbuck Junior Member

    Hi all,

    We are about to have another stab at building a Hartley TS21. The first ended in ashes - very sad and painful story, won't bore you.

    I am seriously thinking about replacing the 50 year old boilerplate swing keel design with a modern drop down weighted foil shape centreboard - as can be found on almost all recent trailer sailers.

    Do people suggest I simply emulate the exact surface area of the boiler plate but just go deeper, which would mean it would end up slightly thinner?

    We are building the Hartley TS21 to commemorate 50 years of the trailer sailer just in case people think I have rocks in my head wanting to build such an old boat. However, we are considering a variety of minor design modifications to improve her whilst not wanting to venture too far away from the original well proven design.

    Any thoughts or suggestions would be very much appreciated.

    Thank you
     
  2. Doug Lord
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    Doug Lord Flight Ready

    Hartley TS21

    Would the new keel modifications be class legal for racing-and does that matter? If you lower the CG of the keel you are increasing righting moment and you'll need to take a close look at the boat structure and rig design to be sure everything can handle the increased loads. Have others in the class made similar mods?
    Good Luck!
     
  3. jumbuck
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    jumbuck Junior Member

    Hello Doug,

    Thank you for your reply Doug.

    Class legal is not a concern to us. We know we are going to be outside the official measurement anyway and so during the first group of meets we may be able to have her own CBH rating established.

    Due to the age of the design (near 50 years) there have been a wide variety of modifications made by owner/builders over the years as they attempt to incorporate modern building techniques and changes to boost performance. I've studied may of these and some of them are pretty aggressive while others are discrete but highly effective.

    On one the owner built the boat with a slightly flatter under waterline hull shape, and according to the owner it has put his boat in another class as far as performance goes. He describes his boat as having "slightly less of a banana shape underwater". He also has bowsprit and asymmetric spinnaker.

    On another they have built in a weighted foil shape drop down centreboard instead of the swig keel plate, which also is reported to have made a substantial improvement in overall performance.

    At the end of the day she will not be a true Hartley TS21 but the exercise to study what can be done to improve her by design has huge potential to bring performance benefits ... if done very carefully. Are there any areas where you would suggest improvements can be made?

    Cheers
     
    Last edited: Mar 14, 2011
  4. Doug Lord
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    Doug Lord Flight Ready

    ----------
    As long as the structural implications are taken care of properly-possibly with the assistance of an NA or proven work by another owner I'd go with a deeper vertically lifting bulb keel and with rig improvements such as a square top main, if possible and desirable. If the RM is increased it would probably pay to increase the SA to take advantage of the greater power to carry sail.
    It sounds like it could be a fun project as long as the structural requirements of any changes are meticulously dealt with.

    For those not familiar with the boat: http://mytrailersailer.com/hartley-ts21.html
     
  5. Petros
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    Petros Senior Member

    I think that is a great idea, as long as the boat you build give you want you want. It is a lot work to build a boat, so make sure it suits your needs before you get started.

    I see nothing at all wrong with updating the keel or any other part of the design. However, as pointed out, if these are regularly races you would not have a handicap rating for your altered design.

    Make sure you approach the alterations carefully so you do not end up with something difficult or dangerous to operate.
     
  6. jumbuck
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    jumbuck Junior Member

    Thank you Doug and Petros for your replies, much appreciated.

    Can I ask what RM and SA refer to please Doug.

    I like the idea of moulding the lead as part of the actual foil at the bottom of the drop down centreboard, i.e., top 70% wood, bottom 30% lead. That way she can be raised completely.

    These boats must have around 250KG ballast and the plan states this is to be on the floor beside or in front of the centerboard case. Imagine how much more efficient it will be when the bulk of this ballast can be positioned at the bottom of the drop down centreboard.

    Best regards

    Peter
     
  7. Doug Lord
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    Doug Lord Flight Ready

    ==============

    My apologies-wasn't thinking: RM= Righting Moment ; SA= Sail Area

    Peter, could you change the cabin configuration to a flush deck or raised flush deck? advantages: more deck space, more interior "roominess", better aerodynamics.

    pix=raised flush deck-click on image:
     

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  8. jumbuck
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    jumbuck Junior Member

    Hi Doug,

    Thanks for your reply Doug.

    Yep, current plan is to increase freeboard by about 80mm and reduce cabin top height accordingly but we'll stick with having a cabin as this keeps the boat at least along the lines of the original design. I'm hoping she will still clearly be recognisable as a Hartley TS21 - although what goes on under the waterline is a different thing.

    I'm going to build a 10% model of her which will be sort of therapy for me (after the fire) until I can get started on building this second one in earnest.
    Cheers for now

    Peter
     
  9. Gary Baigent
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    Gary Baigent Senior Member

    My friend Jimmy Keogh has a modified Hartley 18; he extended the stern with a small scoop, cut the cabin in half, lengthened cockpit, made a new daggerboard and rudder ... and took all the ballast out. The 18 is a dinghy anyway and as Greg Elliott says, "ballast just dumbs the boat down" - or words pretty close to that effect. Jim thinks he may need a little internal ballast forward to keep the buoyant bow down in a seaway.
    When you disregard, or remove, the ugly dog box, the Hartley hulls are okay ... and provide plenty of fun sailing at little expense. Ho on, be a devil, make your 21 into a true dinghy too.
     
  10. terry hagan
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    terry hagan Junior Member

    Hartly 21 Centerboard Mod's

    i am in the process of researching in prep for my Hartly 21 build, i am considering removing the centerboard and replacing it with 2 LOW ASPECT RATIO keels these would be situated where bilge keels would be, but, would be longer and narrower, ballast would be along line of keel starting at mast support and if needed would be encapsulated in the L.A.R. keels. this would give more free space in cabin and ability to sit on a beach vertical as all the boat weight would be spread over the 2 L.A.R. keels and center keel... IS THIS FEASIBLE.......
     
  11. Petros
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    Petros Senior Member

    Welcome to the forum terry,

    yes, anything is feasible, but your proposed configuration would suffer noticeable performance degradation. Not having the weight as low means it will heel over easier, and two low aspect ratio keels would have more drag and less ability to point. You can likely deal with having less righting moment by depending on crew weight more, and perhaps adding some extra weight in the low aspect center keel (the extra weight will cost some speed but it will also make it more sea worthy in heavy weather). I would suggest using two high aspect ratio dagger boards in the bilges. this will keep the center isle clear of a centerboard trunk or case, but still give you good pointing ability. when you beach or trailer you lift both dagger boards up.

    Another option might be to use a single low fixed aspect ratio wing keel to get the effect of a high aspect ratio keel without the draft. No moving parts and simple configuration. But you better get some competent design assistance for a properly designed winged keel.
     
  12. PAR
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    PAR Yacht Designer/Builder

    Considering the concepts and engineering employed in the Hartley 21, I'd opt to modernize much more than the board. I'd put the boat on a diet, as mentioned, she'll be well served by this and the build could prove easier too. I'd make a full conversion to a taped seam method, ballasted foil sectioned appendages and likely modifications to the underwater volume distribution, so she could take advantage of some of these changes.

    The conversion from plank on frame to taped seam, will eliminate much of the localized framing structure. This saves the bother of buying the stock, fitting and installing it. The goo factor will go up, but if you're comfortable with epoxy and sheathing, not so much a problem.

    A ballasted foil, shaped centerboard would help in a few regards, but the structure would have to be reviewed, for the new and increased load paths. The weight savings from the build method conversion could be used as ballast, keeping the boat on her lines. A better rudder would also be helpful.

    As to the lines of the boat, well much could be done to improve her abilities up wind and reaching. I'd decrease her buttock angles and provide some "power" forward.

    The sail plan will need revision too, so she can take advantage of the stiffer form and heftier RM, without breaking her stick or popping a shroud.

    All in all, a design of this age, has many places modernization can show improvements. Newer materials and techniques will help and modern thinking behind some of the shapes employed too. Naturally, some of these things, would require some professional assistance, but not too costly really.
     
  13. terry hagan
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    terry hagan Junior Member

    Hi Petros
    yes i get the drift of what your saying...what is your thoughts on 2 CB.s but hidden behind the seating unit's, yes it will reduce storage capacity but this boat is not relay designed for long hauls just coastal hops. i helped build may boats in UK and one owner redesigned the cb and put in 2 cb's behind the seating, the cb's were on a small hand crank block sys and skin of the hull had 2 small LAR keels so she could beach with no problems. so maybe this could be what i'm looking for
     
  14. terry hagan
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    terry hagan Junior Member

    Hi Par
    now that is another thing i am thinking of ''stitch an glue'' build....get rid of all the stringers.....i'm also thinking of not using solid lumber for frames but using m/ply the reason for that is all i can buy here in Philippines is mahogany nice wood but so heavy and hard to work with
     

  15. terry hagan
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    terry hagan Junior Member

    Petros
    for the life of me i can't remember the design but in the boat yard there were 8 of the same design and we took out 3 for a sail. the standard design, a bilge keeler and our re-design and 6 men 2 in each boat spent a day testing all 3 boats and to be honest we couldn't find any real significant changes in sailing or handiling properties
     
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