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Thread: i am making a rudder

  1. #1
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    Default i am making a rudder

    Since no spare J-29/J-30 rudders seem to be forthcoming, I'm going to make my own new wood core rudder.

    The basic idea is to build a core of 2 inch thich, 1 3/4 inch wide doug fir strips. They're cut from straight grain doug fir 2 x 8's. Then you randomize the strips by reversing a few and mixing them up so that the strength in the rudder goes everywhichway, and also, in case any water gets in there, any distortion in one strip isn't carried out through the whole rudder as it would be if it was all one piece of wood.

    Glue the strips together into a 2-inch thick, 16 inch wide, 7 foot long board.

    make a NACA foil jig for a the rudder, and use the router on the jig to form the foil.

    Sand. Fair. Sand

    overlay with epoxy in 8-10 oz cloth...maybe consider putting a layer of kevlar along the leading edge.

    sand, fair sand..paint.

    Make hardware... put on antifouling, mount on boat.

    I will document all this with photographs, etc.

    OK, $208 later, for straight grain doug fir, plus some re-sawing
    $40 for two more bar clamps that are bigger than 1 foot span ( I had two already)
    $50 for a Ryobi 1.75 hp router of of craigslist, and we are on our way.
    Last edited by AlanH; 12-17-2017 at 06:57 PM.
    S-2 7.9: "Wildcat of Loch Awe"
    1968 Selmer Series 9 B-flat and A clarinets
    Piper One Design 24, Hull #35; "Alpha"

  2. #2
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    Live in Phoenix, boat in San Diego
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    Neat project. Looking forward to the pics and reports.
    Lee
    s/v Morning Star
    Valiant 32

  3. #3
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    Lookie what I generated....

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    The inner shape is the foil x-section itself, printed at real size. The outer line is the shape for the top of the router jig. The router bit needs to be set at a depth of 38 mm.

    How did I get that? Look here.

    http://www.duckworksmagazine.com/09/...oils/index.htm

    This is what I'm doing. Read the article, download the foil generator and router-template generator.
    S-2 7.9: "Wildcat of Loch Awe"
    1968 Selmer Series 9 B-flat and A clarinets
    Piper One Design 24, Hull #35; "Alpha"

  4. #4
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    OK this weekend saw me do the rudder blank glue-up.
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    Rudder is 7 feet, 10 inches long, overall. Essentially, 50 inches of that will be submerged. The bit on the left is the trailing edge, which is thinner pieces than most of the rudder. I epoxied that on, tonight (sunday) along with two strips that will be the leading edge. This rudder will be about 12% balanced. The chord is 15.5 inches. That's close enough to 16, which is what I planned.

    My shortest piece was 7 feet long. I cut everything to 7 feet, which was stupid, as I wanted a 7' 6" + rudder. Me=dummy. So I wound up offsetting some joints. The ones you see in the rudder closest to the camera don't worry me even though they line up a bit too closely, as that's the absolute bottom of the blade and the loads are minimal down there.

    I wouldn't make a mast like that, though. Also, there are NO joints anywhere near the point of maximum load, which is right near where the bottom gudgeon will be.
    S-2 7.9: "Wildcat of Loch Awe"
    1968 Selmer Series 9 B-flat and A clarinets
    Piper One Design 24, Hull #35; "Alpha"

  5. #5
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    Here's the final glue up...leading edge and trailing edges are on. I ran out of wide clamps so I'm resorting to taping...yes, taping on a couple of small pieces that are really only there for shaping and fairing. There are a few bit of wood in there to support things while they dry. They're covered with wax paper so I don't glue them to the rudder. The leading edge is to the upper right in this picture, trailing edge to the lower left. There's a little strip in there between the main body of the rudder and the piece that will form most of the leading edge. I needed that to make the 12% balance. Without it, it would have been 10% and I wanted just a scooch more than that, but not 15%. Most of that wood will be removed by the router forming the leading edge of the foil, but if it's not perfect, I'll just fair it. It's going to be close, anyway, and there's a lot of gluing surface holding everything on..

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    I cut off a few bits along the bottom that I epoxied together...these are squares roughly 2 x 2... and I can't tear them apart. So that seems pretty strong.

    The whole thing probably weighs about 45 pounds right now.
    S-2 7.9: "Wildcat of Loch Awe"
    1968 Selmer Series 9 B-flat and A clarinets
    Piper One Design 24, Hull #35; "Alpha"

  6. #6
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    On to the rudder foil templates. They're made out of plywood.

    Look at this image-



    This guy made his template foils out of particle board. I'm using plywood. No big deal. I mucked up the first foil template by not paying attention while running the jigsaw... moron mistake, so started over. The second one came out fine, but that meant a visit to Orchard Supply to get a cheap 2 x 2 piece of plywood for the other template. Since they had no 3/8th ply, I bought a sheet of 1/4 inch, cut two 5-inch widths to size and I'm glu'ing them together with Weldwood to make a 5" by 24" x 1/2" piece.. OK, so one side of the router carrier will be 3/8 and the other side will be 1/2. It's just the router carrier. While I was at OSH I bought a couple of new jigsaw blades, "many teeth" and narrow profile for cutting curves in wood. That worked like a charm and I now have one remarkably accurate foil template. Handholding the jigsaw and going slow was just fine, I didn't need a scrollsaw, which saved a drive up to San Bruno to get a used one off of Craigslist.

    I'm contemplating whether I need to run my whole rudder blank through a planer to take down the high spots. Hmmm. Who's got a 16 inch wide planer, I wonder.

    Progress!
    Last edited by AlanH; 11-11-2017 at 08:16 PM.
    S-2 7.9: "Wildcat of Loch Awe"
    1968 Selmer Series 9 B-flat and A clarinets
    Piper One Design 24, Hull #35; "Alpha"

  7. #7
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    It occurred to me that this would be a great way for someone to knock out a simple emergency rudder for the TransPac for a smaller boat. You could "go simple".... Three dry and straight 5.5 - 6 foot 2 x 4's plus a 2 x 2 would give you a 12 inch chord with a rudder thickness of 1.75 inches. That's very roughly J-24 size, and significantly thicker. If you wanted a bigger chord, just use another 2 x 4 instead of a 2 x 2. Glue all the pieces edge-to-edge with epoxy. Make a foil template like what I'm doing if you're hardcore, or even rough one out with the table saw, a surform plane and a bunch of sanding. Just shape the leading edge to be nice and round, and taper the back half of the blade to about a 1/8 inch wide at the back. It won't be perfect, but it's easy to do, just time consuming. So, in summary, shape the bottom half into some sort of foil, leave the top half un-shaped...just rectangular. Front and back should be straight up and down...parallel.


    Cut the leading edge, in the unshaped top half of the rudder back about 20%. That's right, 20%, which will be about 2.5 inches for a 12 inch chord. That's a lot. Why so much? Read on. Put a layer of 8oz glass in epoxy over the whole thing. Sand, and sand some more. Now you probably have a rudder blade with a 12.25 inch chord and almost 2 inches thick. That's pretty bluidy strong. Epoxy/bolt something to the top so the rudder doesn't slip all the way through the cassette. Paint, and admire.

    Now build a cassette that will accept a rudder that's the thickness of the upper half of your blade, but with an fore-and -aft dimension big enough that you can slide the bottom half down inside. When it's all the way in, it will wobble fore and aft because the top half of the rudder is 2.5 inches smaller in chord than the bottom half. Now, make a 2.5 inch wedge/spacer out of some 2 x 4. Tap that into the cassette behind the rudder so that it pushes the rudder forward in the cassette and jams it into place. No more wobble.

    Upshot...semi-balanced emergency rudder in cassette, U-Bild-It-At-Home-4-Cheep

    The major problem with my e-rudder from 2008 was that while it steered the SC27 just fine, the leading edge was a good 3-4 inches behind the rotational axis. It was horribly UN-balanced and loaded up immediately. This system I outline above would make a somewhat balanced rudder, depend on exactly how you fit the cassette to the pintles on the back of the boat.

    For reference, my S-2 7.9 has a kick-up rudder (until I finish this one). That's the stock, 1-D rudder. The rudder is 3 inches thick, about 20 inches chord at the top and 13 inches chord at the bottom. Top to bottom of the submerged part is about 44 inches. The cassette is made up of hardwood, basically 2 x 4's at the front and back, and approx. 1/4 inch aluminum plates for the sides. It's all held together with about 5, 5/16ths through-bolts at the front, and 5 more bolts at the back. The gudgeons are massive custom stuff that wrap around the front 1/3rd of the whole thing. Any metal shop can make them up but they'd cost a mint. I can think of other ways to make gudgeons that would cost a LOT less.

    This is an ENORMOUS rudder. It's bigger than a J-29 rudder, on a 26 foot, 4500 pound boat.
    Last edited by AlanH; 11-10-2017 at 12:59 PM.
    S-2 7.9: "Wildcat of Loch Awe"
    1968 Selmer Series 9 B-flat and A clarinets
    Piper One Design 24, Hull #35; "Alpha"

  8. #8
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    That is neat! I would love to see a seminar on how to make your own.

  9. #9
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    You can buy foam "blanks" from flyingfoam.com

    That's what I did in 2003, to get ready for my disastrous 2004 attempt. I got one of those and then glassed the snot out of it.... like used this stuff that I can't name right now...it's heavy mat and roving stitched together... two layers of that with Unidirectional carbon in between.

    Then I made a cassette out of doorskins, reinforced with carbon. I did all this in my garage.

    It's do-able. ---just a lot of work. Or you can do this, what I'm doing here, which is also a fair bit of work but it's at least half wood-work and not so much epoxy-yucky-work.
    Last edited by AlanH; 11-11-2017 at 08:17 PM.
    S-2 7.9: "Wildcat of Loch Awe"
    1968 Selmer Series 9 B-flat and A clarinets
    Piper One Design 24, Hull #35; "Alpha"

  10. #10
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    Today I made the router carrier/foil template for the project. I cut the foil shape in one piece of plywood the other day with the jigsaw, as explained a couple of posts, above. I then used the printed pattern from the Excel spreadsheet to mark the cutouts where the plywood foil template has to fit over the unsawn board. Then, fortunately before I cut that out, I went and compared it to the rudder. It was a good 3/4 of an inch too big. Not only that, but the offset for the router bit depth was 4-5 mm too big. What the heck?

    Come to find out that apparently the Excel program works great, but just because it generates an accurate foil and router-offset pattern does NOT mean that your printer will print the exact dimensions. BE WARNED....print your pattern and compare it before cutting! I had to go back and enter new numbers in the Excel spreadsheet to generate an exactly-sized paper pattern to work from. This is trial and error, but I guessed well, and the second time I taped the printed pieces of paper together, I hit the right sizes.

    Once I did that, I re-marked the plywood I'd already cut, which was fine as the new template is smaller than the earlier, wrong one. So I cut out two plywood foil templates, and two blocks, exactly half the thickness of the rudder blank for the foil templates to ride on. Add Weldwood glue and clamps and....


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    Here's the router carrier/foil template...the dark wood was cut from a lap tray I made for Joan when she got her hips replaced a couple of years ago. I didn't need the plywood or the tray, so now it's been re-used. The other stuff is junky plywood and scrap, cut-up 2 x 4's. It bugs me that the two templates are different thicknesses, but it totally doesn't matter.

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    Last edited by AlanH; 11-11-2017 at 08:10 PM.
    S-2 7.9: "Wildcat of Loch Awe"
    1968 Selmer Series 9 B-flat and A clarinets
    Piper One Design 24, Hull #35; "Alpha"

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