Making new style rudder for old style boat

Discussion in 'Sunfish Talk' started by wjejr, Jan 15, 2017.

  1. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    Why did you make a bigger rudder blade? More blade = more drag. You want the rudder as small as possible while still being effective. That is one thing I still remember at my age.

    Thanks you for your advice and for posting the pictures.

    Since I am making the rudder to the new shape, I decided to make it to the new shape's dimensions. No other reason. Practically, it seems a good thing to have the rudder deeper in the water for a couple of reasons, and I would imagine that the rudder with the proper shape will act as a lifting surface and a least partially negate the slight increase in area.

    I have a second set of hardware to put on the new rudder, so it should be easy to compare.
     
  2. Webfoot1

    Webfoot1 Active Member

    Likes Received:
    34
    Trophy Points:
    28
    I always give mine a airfoil shape just because. If you want to go all the way, leave the
    trailing edge squared-off. With a rounded trailing edge there is flow separation about
    two-thirds of the way towards the rear of the rudder on each side. With a square trailing
    edge you get a vortex bubble that delays the separation. Hopefully, you will not get vibration.

    There is one of those old bronze brackets on Ebay. Personally I'd put the money towards a new style bracket.
     
    • Informative Informative x 1
  3. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    On the trailing edge:

    I will squaring off the trailing edge as you suggest. Thank you for that advice.

    I am planning to model the foil shape based on the rudder that I have for my Laser. It won't be perfect, for one thing the chord length varies in the new rudder configuration, but it's supposed to be a fun project for an old (1971) non class legal boat and not for use in the Sunfish World's.

    On the bracket:

    The thing of it is, is that I already have the additional hardware for a second rudder, which I picked up on eBay a couple of years ago, just checked, for $9.95. The original hardware stays with the old rudder and will be used when I sail with my children. That rudder has the original length wood extension connected to the tiller, and I find that the short extension helps on cockpit space. For the new rudder, I plan to add a longer extension and use that configuration when I sail alone.

    Again, I've sailed the boat in a lot of different conditions and have never had a problem with the old rudder hardware. Maybe I am doing something wrong? :)

    It's certainly possible that with the new rudder, something may change, but right now the only advantage I see in the new rudder configuration is that the rudder locks in the upright position. That's certainly a great feature, but it's only been a minor annoyance in the places I sail. When I consider the amount of money it would take to convert both the old and new rudders to to the new configuration, I am guessing I could probably buy another boat.
     
  4. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    Hello fellow Sunfishers. Here are some pictures of gluing and clamping the boards. I'm using MAS epoxy with wood flour as a thickener. Together they will form the blank from which the rudder will be cut.

    1 Gluing 2 D.JPG 2 Gluing 2 before clamp D.JPG 3 Gluing 2 start clamp D.JPG 4 Gluing 2 finished clamp D.JPG 2 Boards Glued D.JPG 3 boards glued D.JPG
     
    • Like Like x 1
  5. Webfoot1

    Webfoot1 Active Member

    Likes Received:
    34
    Trophy Points:
    28
    The old rudder bracket clips into the fitting on the keel. The keel fitting
    has a pocket where the edges wear out. You may have hardware that is
    in good shape. If it works fine no worry's.

    What I did was wait for the cast aluminum version of the new rudder bracket to show
    up on E-Bay. Maybe I got lucky as I don't see them come up all that often. Someone
    on the forum might have one to sell, they are worth about $45. Buying tiller straps/springs
    /transom mount etc. I think had about $100 invested not counting labor to do the
    wood work.

    The new bracket actually locks the rudder in the down position. There is a angled part
    of the tiller strap that fit over a angled part of the rudder mount. Works as long as
    the tiller is not lifted up.
     
  6. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    Well it's been a little while since I last posted, but I have not given up. The finished blank came out remarkably well with a deflection over the length of the board at about 1/16 inch. I sanded the board down and then ran the blank through the table saw to form the leading edge.
     

    Attached Files:

  7. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    The next step was to start shaping the rudder into a foil. One challenge with the sunfish rudder is that the chord length varies. Being a bear of little brain, I never though much about it before, but I now know why blades tend to have a constant chord. There seemed two options. Option 1 was that if I wanted to use the same foil shape across the rudder top to bottom then I would need to taper the thickness: thicker at the top and thinner at the bottom. Or option 2 was to vary the foil shape. With a thinner foil at the top and a fatter one at the bottom. I chose option 2. I decided to use an NACA 0008 foil at the top, transitioning to a NACA 0010 foil at the bottom. I chose the 0008 foil as it worked with the general dimensions of the rudder where it is widest and the 0010 foil that worked best with the bottom of the rudder.

    Once I decided on the shape, the next challenge was to start shaping the board. I decided the best/easiest way was to use my table saw with s dado stack. I tilted the stack 3-4 degrees and used a cutout profile so I would know how deep the cup should be. That's the picture of the paper foil glued to the stick.

    Running the blank through the table saw proved a challenge since the foil shape is only starts below the head. I first made a full size model out of piece of pine and then made marks on both the blank and the saw fence so I would know just how far to go. That whole process worked remarkably well, but you may be able to notice that the trailine edge at the bottom is too fat. That's because of the changing chord. Where the chord is widest at the top, the trailing edge is thinner.

    Next step is to start refining the foil shape top to bottom.

    I have to admit, I did think about just putting bevels as the plans show, but where's the fun in that? Besides there's 14 inches of snow on the ground. :)
     

    Attached Files:

  8. Light and Variable Winds

    Light and Variable Winds Well-Known Member

    Likes Received:
    131
    Trophy Points:
    63
    If you had started with a larger blank, wouldn't a "pie cut" solve that problem?

    Fullscreen capture 2152017 34235 AM.bmp.jpg
     
  9. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    Thatnk you for the suggestion.

    The blank is large enough to do that, but I think it is easier to just run it through the table saw against the trailing edge. Because the 0010 foil is fatter, so in theory at least, it should not interfere with the 0008 foil further up the rudder.
     
  10. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    As I am making this up as I go along, I decided to cut the blanks trailing edge leaving a little extra for the final trim. I ran my test blank through to see if I had the angle correct which I did. I thought I needed a little more width, so I just moved the fence over 1/4 inch. I then ran the good rudder blank through which left 1/2" Now I have just about 1/2 extra on the trailing edge.

    The line on the yellow tape running lengthwise is where the maximum thickness of the foil will be.
     

    Attached Files:

  11. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    I am further ahead on the rudder than on posting, but the next step was to start shaping the the foil/rudder from the bottom where the cord is smaller.

    1. I will be using a dado stack on my table saw tilted at about ~ 4 degrees. Because the chord is fatter at the trailing edge, the theory is that when I start the cut, the dado will cut less and less as I move up the rudder and eventually not cut at all.
    2. The Foil Stick picture shows the NACA 0010 foil cutout that is glued to a scrap piece of wood using spray adhesive. I use a backer block when I run it through the stack so the paper cuts neatly
    3. Shows the same stick with the dado cuts. I lower the blade a little each 3/4" that I move the table saw fence to the right.
    4. The tricky part is knowing how far to cut. To do that I put reference marks on the fence and on the rudder blank. Feeding the rudder bottom first was easy. Cutting the other side was a bear as the board wanted to feed back be. S
    5. Shows the dado stack and rudder blank.
     

    Attached Files:

  12. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    Now comes the task of final shaping. Running through the table saw with the dado head attached roughed out the shape, but a lot of work remains to get to the final shape. Not being sure of what the best tool to use, I tried them all. I used a #2 hand plane and a flat spoke shave to take out most of the dado blade marks. The problem was that where the rudder transitions into the rudder head it's hard to use smoothing planes. Here I used a round spoke shave, a low angle block plane and a shoulder plane. I also used a rasp, chisels and an old Stanley #20 gouge. Each of these tools had its advantages, but none were perfect. The result of fussing about with all of these tools is in Picture #9.

    After using the planes, I started sanding with a large autobody sanding block. I started with 100 grit and for now finished with 120. I don't want to go any further since there is still work to do forming the leading edge.

    If I ever make another rudder, I will be more careful in the rough shaping so that I do not have to remove as much wood, and that the transition to the rudder head is perfectly lined up.
     

    Attached Files:

  13. Light and Variable Winds

    Light and Variable Winds Well-Known Member

    Likes Received:
    131
    Trophy Points:
    63
    Would two passes by a stationary router make the leading edge you want?
     
    • Like Like x 1
  14. tag

    tag my2fish

    Likes Received:
    90
    Trophy Points:
    28
    Did you try talking to John at J.O. Woodworks? I think he randomly posts on this forum...
    He has been making wooden Sunfish parts for years - might be able to give you some tips and tricks.
    J.O. Woodworks

    (Might be too late at this point...)
    Oh, and I'm jealous of some of your woodworking hand tools!
     
    • Like Like x 1
  15. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    Thank you. Yes, and that is exactly what I am planning. I bought a panel raising bit when I first got the boat and used that when I rebuilt the daggerboard. I will use that same bit for this project. Remarkably it is almost a perfect match for the foil shapes.

    The router table is already set to go. I just need to find the time and the courage to proceed. :)
     
  16. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    Thank you for your suggestion. You are right though in that I am getting towards the end of the project. The rudder shape looks good and feels right when you run your hand across it. I have found it challenging to have the back of the foil gently curve. I used the #2 plane for this reason as the blade is fairly narrow. When I got to the block sanding, I used the larger size and purposefully tried to have the block curve rather than lie flat. The block sanding really helped, although I am sure it is not perfect.

    On the hand tools, thank you. I just wish I had more time to use them. :)
     
    • Like Like x 1
  17. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    I worked on the leading edge yesterday using a panel cutter to make the shape. I practiced first on piece of scrap, then the full size pine model and finally the mahogany blank. I took 3 passes on each side so as to minimize tear-out and create the smoothest cut. Next will be back to the sanding block and blend the leadin edge into rudder.

    In case you were wondering about the router table setup, it is mounted in the extension table of my table saw, and that helps save space The red router plate allow you to raise the router up and down easily with the dial handle bottom right. Having this adjustment mechanism made staging the 3 passes simple. The fence connects to a vacuum hose and keeps the dust/chips manageable. The router is variable speed, so that I can run the router bits at the different speeds.
     

    Attached Files:

  18. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    I've got a couple of questions for all of you Sunfish experts out there, the first of which is, "Why is the rudder bottom angled in such a way that the trailing edge is higher than the leading edge?" Have a look at the attached picture. The blue line in the picture shows how the trailing edge is shorter than what I would have thought. A couple of possibilities as to why the designers did this have crossed my mind:

    1. It lessens the possibility of damage when hitting/scraping/beaching the bottom as the trailing edge is thinner and weaker than the leading edge.
    2. When the boat is moving through the water the bow lifts such that the rudder bottom is parallel to the surface of the water.

    My guess is that it's the first, but I am interested in what others think and if any knows for sure (i.e. in literature or builder told them directly).

    The next question is whether it makes any sense to deviate from the design and have the trailing edge longer?

    As always, thank you in advance for your thoughts.
     

    Attached Files:

  19. Light and Variable Winds

    Light and Variable Winds Well-Known Member

    Likes Received:
    131
    Trophy Points:
    63
    Sunfish don't always sail in a forwards direction: backing in shallow water would increase the risk of rudder (and board) splitting.

    [​IMG]
     
  20. wjejr

    wjejr Member

    Likes Received:
    21
    Trophy Points:
    18
    I've been away, first on vacation and now on business, but I was able to make some progress on the rudder.

    The next step was to start to create the final shape from the blank. I made the cut by first tracing the line onto the blank and then making the cut using a radial saw. I taped the back of the cut to minimized tearout. I also clamped the rudder so it would not move. Murphy's law kicked in and the angle of the cut caused the blade to cross over a screw that holds the table to the saw. I removed that and made the cut.
     

    Attached Files:

Share This Page