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Thread: Converting rowing tender to sailing tender

  1. #1
    Join Date
    Apr 2005
    Location
    Pennsylvania
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    I have cold molded rowing tender that I would like to add a sailing rig to. I would appreciate any suggestions as to the process to follow to ensure it comes out right.

    Following are the measurements and some photos.

    http://i4.photobucket.com/albums/y11...p/100_2985.jpg

    - 7'6" long
    - 54" wide at the oar locks 49" at the
    center/thwart seat
    - Transom is 49" wide X 24 " tall 1/2" mahogany
    ply
    - Depth of hull below the center thwart seat is
    11" to floor.
    - keel board is 2 1/2" wide
    - Skeg is 1/2" wide, 2" tall, 30" long

    http://i4.photobucket.com/albums/y11...p/100_2987.jpg

    My plan is to build a centerboard trunk of 3/4 " marine ply and place under the center thwart seat. Fasten and fair into place. cut a slot in the thwart seat and the keel board for a 1/2" center board / dagger board.

    http://i4.photobucket.com/albums/y11...p/100_2993.jpg

    On the transon I was going to reinforce with a mahogany knee that extended the height of the transom from the floor. This would be fastened to the transom and allow for hanging a couple of gudgions on the transom to accept a rudder pintels.

    http://i4.photobucket.com/albums/y11...p/100_2991.jpg

    For the mast and sail I thought of putting the mast at the bow of the boat in the existing
    hole in the mahogany fore peak (IF that is the correct name for this area shown above.)

    I have an old Jib from one of my earlier boats that I thought of cutting down to make up a sail but am not sure on how to size this, nor am I sure of how tall to make the mast or long to make the boom.

    All suggestions greatly appreciated

  2. #2
    Join Date
    Dec 2003
    Location
    on-the-cuyahoga
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    13,063

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    http://www.boatplans-online.com/
    The above web site has a free download for a sailing pram called D4. It is an older stitch and glue design, 7'10" x 46", that carries about 35 sq. ft. of sail.
    It's bit different than your boat but the plans have all the dimensions for the sailing accesories like daggerboad and trunk, rudder, mast, sail, scantling sizes ,etc. The whole thing is made from and 3/8ths plywood without any transom reinforcing etc. The current plans for the boat, which are not free, has the daggerboard in the middle of the seat but all else is the same.
    I'm using WIN XP now which can't read the D4 files but when I was using WIN 2000 it came thru loud and clear.
    Give it a look. It should be informative.
    Charlie

  3. #3
    Join Date
    Apr 2005
    Location
    Pennsylvania
    Posts
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    Charlie- thanks for the reference. I couldn't locate the D4 but was able to find the D5 and PK78. My conversion is very doable with the materials I have including a salvaged daggerboard and rudder from an old phantom. Wish I had kept the sail rig from that boat,could have cut it down a bit and had a perfect fit. I wasn't sure where the best place was for the daggerboard but amidship on the thwart seat should work fine. Using a sprit rig will allow placement of the mast at the bow.

    The little lady I am cobbling this up for will have a summer of fun learning how to sail.

    Thanks - Graham

  4. #4
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
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    On Tibbots I went for a single side board rather than centerboard or lee boards.

    If the pivot point is located down from from the top of the board, the strain is the same on either tack and a dink should be sailed pretty much upright anyway, so having the board on just one side simplifies things. I have it on the starboard side as I normally land on the starboard side of Granuaile.

    The advantages: No hole in the dink that must be capped if you're towing; more space in the interior; simplicity of installation; trimability.

    That last, trimability, is nice if you're rowing in a fresh or strong breeze (force 5 or 6, over 15 knots) as the board will allow your rowing course to tack into the wind rather than flog straight to weather - Very much easier.

    On your dink, the right place is a bit ahead of the broadest part of the hull. Given that curve and the hull's flare, you'll need to build up a flat on the hull to land the board, roughly 4" from gunnel down and 4" fore and aft should do it. Land the pivot dead center to that. Really, 2" lever arm is enough for this.

    Best pivot is keyed to the board and comes inboard to a knurled nut fitting and lever arm. That way you can raise and lower it from inside.

    G'luck

  5. #5
    Join Date
    Apr 2005
    Location
    Pennsylvania
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    Ian- that is an interesting option I hadn't considered. It would be much easier to complete w/o drastically altering the boat. I assume the thickness could be a 1/2 - 5/8" with faired edges but what would be the recommended length of the board below waterline.

  6. #6
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
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    True leeboards are often a bit shorter than dagger or centerboards as their lateral plane starts at the water's surface, but this unit gets use on both tacks and you want it to gain some useful bite when only partly immersed as in rowing or sailing off the wind. For those reasons, I'd start with it about as long as a dagger board.

    On mine current dink, I started a bit shorter than I might have because I adapted a leeboard from the previos dink that had been stolen. It works ok because the current dink has a notably lower freeboard.

    The leading and trailing edges of the pad need to be faired in to look nice. The lower edge is about normal to the hull. The top at it's narrowest point is just about the width of the gunnel lip.

    G'luck

  7. #7
    Join Date
    Sep 2003
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    Somewhere in South Central PA
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    I'm no naval architect and I don't play one on TV but....

    I think you may want the centerboard trunk to be a bit forward of the center thwart and the mast to be probably closer to the aft edge of the forward seat. You should probably draw up a sail plan and figure out the geometric center of the sail and put the centerboard just under it, if not just a wee bit ahead of it, so the boat will round up if you let go of the tiller. You can probably use the forward seat as a mast partner and then mount a mast step in the bottom of the boat for a small free standing rig with no shrouds. A sprit rig, standing lug sail, or triangular sail with two-piece mast would allow you to stow the rig in the boat. 35 or 40 square feet of sail sounds about right. The transom is probably strong enough for a rudder without an additional knee, given how small this boat is.

    My $.02, FWIW,

    Have fun,

    Brian

  8. #8
    Join Date
    Apr 2005
    Location
    Pennsylvania
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    Thanks to all for your suggestions. I knew I would find some answers here, you all seem to be a good group of people..

    I have been lurking around here for a while now looking at various posts fondly remebering my days of restoring a GP14 then later a very old lightning. Must admit though I have avoided the wooden boat bug for the past 15 years. This conversion will be fun.

    thanks

  9. #9
    Join Date
    Apr 2005
    Location
    Pennsylvania
    Posts
    9

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    The Hull modifications and related rigging are complete it floats and doesn't leak photos to come when the sail is complete.

    It is now time to sew up the sail.

    I have decided on a spritsail design. I will be using a Mertens D4 Dinghy design, 33 sq',Loose footed sail with grommets on the luff. I am cutting the sail from an old dacron Jib I have from one of my old boats and have two questions for you all:

    1- Should I use a loose footed sail plan or use a boom? I had planned on a loose footed sail but could change to a boom set up if there are significant advantages.

    2. The sail will be lashed to he mast using a 3/16 line through grommets in the sail from the throat to the tack and wrapped around the mast. Should the luff have a bolt rope sewn along the luff between the tack and the throat for reinforcement?

    Sail dimensions are: foot 5'8, Luff 6'3", Head 3'6", Leech 8'6"

    recommendations are appreciated

  10. #10
    Join Date
    Jun 2000
    Location
    Madison Wisconsin
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    Fold a 2"-3" wide strip of dacron in half and over the raw luff edge. Run one line of stitches along the inside edges of the piece, another close to the sail's forward edge. Install the lacing grommets through all three layers of fabric and between the two lines of stitches. Spur grommets (with teeth) hold much better than hardware store washer grommets, but washer grommets will do for a while. If you buy them, take a magnet to the store and check to be sure they are real brass, not plated steel.

    You do need to build up reinforced areas at the peak, clew, tack and throat corners with stacks of Dacron patches (about 4 layers total and covering a minimum of about 10% of the sail edges' lengths to spread the loads from the corner grommets). It is the grommets in those corners that take most of the strain, not the luff's lacing grommets. 1/8" line is plenty for lacing. Halyards, snotters, etc should be 3/16"-1/4" and non-stretch if possible.

    A sprit boom could be added to improve off-the-wind performance, but most kids will probably do better and have more fun with no boom and I certainly would not complicate the issue with a conventional boom. I would add a brail to quickly furl the sail. It's so easy to use and rig that it's a crime not to have one.

    The most important thing in cutting the sail, especially if you're cutting it from an old sail, is fabric weave and getting it pointed in the proper direction. Failure to do so will result in a stretchy sail that won't work well. The weave and panel-to-panel seams need to be either parallel to, or perpendicular to, the sail's leech edge. Both will work and you can measure to see which is easiest to get out of the jib you're cutting up. If given a choice, fabric from the more aft and/or higher areas of the old sail (away from the luff and foot edges) usually has less built-in shape. You'll put your own shape in, you don't need their's confusing the issue.

    Cut the head edge dead straight. It will sag a bit in use, creating draft up high. Add about 1" of round to the luff edge, with it's maximum about 45% of the luff length up from the tack corner. Hollow the leech edge about 1.5" with maximum hollow half-way up. The foot should also be slightly round with the maximum added about 45% aft of the tack corner. If you add more than about 1" of foot round, the edge will flap badly unless you want to pick up a sailmaking text and learn how to broadseam (create a slightly cup-shaped foot by adjusting panel-to-panel seam overlaps). It's not all that hard, but would take some studying. Broadseaming in the tack area would also allow you to get more shape and draft in the lower part of the sail, as well as use a bigger, somewhat better looking (2"-3") foot round. For a kid's sail, the amount of round and draft down there probably isn't terribly critical to having plenty of fun, so you may just want to go with a small amount of round and not worry about trying to create a lot of lower shape by messing with panel seams.

  11. #11
    Join Date
    Apr 2005
    Location
    Pennsylvania
    Posts
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    Todd - Thanks for the information. You have confirmed my initial plans. I will be keeping the sail loose footed w/o a rope in the luff line.

    I have cut the sail and done the folds. After pressing the folds crisp I used dacron rip stop tape to seal the edges and reinforcing patches in place for sewing. I felt it would make for sewing the seams easier although it wont look quite as clean with the tape in place.

    Now I am keeping my fingers crossed that I got the geometery right and the little boat sails properly.

    Thanks Again, your comments were most helpful!

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