Blackrock 24 (Build)

Discussion in 'Wooden Boat Building and Restoration' started by LP, Mar 12, 2013.

  1. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I too noticed the gap and assume it'll be filled somehow.

    A recent rudder, much smaller than that I did, shows how I like to recess them into the blade or rudderhead, so the pivot line is just forward of the leading edge. This one swung through 60 degrees each side.
     

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  2. LP
    Joined: Jul 2005
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    Location: 26 36.9 N, 82 07.3 W

    LP Flying Boatman

    I suppose I posted a little prematurely. I've only mounted the rudder head with temporary fastenings so I could do a geometry check and make modifications as necessary.

    My rudder is wicked fat. 3/4" cheeks with about 2" of blade width. I've probably build the blade fatter than necessary, but due to the position and size of the mizzen, I wanted a blade that would not stall easy if loaded up. That's my thought process anyways. Long story short, I hadn't foreseen the setback issue with the rudder and hardware so the rudder design is developing as it gets built. I am contemplating a filler block to act as a support for the rudder fittings and to also close up the gap between the rudder and the transom.

    I really debated the below the waterline fittings and opted to go ahead with them to reduce forces on the lower fittings. I was considering a third set of fittings just above the waterline as a backup should the lowers fail, but decided I was being paranoid. I feel that with the rig choice I have, I'll be able to steer with the mizzen sail in a pinch and ultimately, I'll have some steerage with the outboard.

    I installed double gudgeons on the lower fitting as it has the greater load and I wanted to increase the amount of purchase due to the smallish footprint of this particular fitting. Most likely, this will make the failure point at the lower pintle. The lower pintle is the longer of the two so I used that length to advantage and doubled the gudgeon in the hopes they would also reduce any tendency to twist the pintle. I'll drill fastening for the lower gudgeons over size and will pot them with an epoxy mix of CS and milled fibers. I would prefer to through bolt them, but I am loath to add the complication so I will use lags or large screws.

    Oh, Paul. Nice detail on your cheeks. Rudder cheeks that is. :p. What's the stainless piece that wraps over the top?
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The piece that wraps over the top is aluminum. The rudder is plywood, 3 layers of 1/2" and end grain was exposed. The lower portions are tapered and 'glassed, so not an issue, but the upper portions just have eased edges, so I wanted to protect the end grain from impact and not have to also wrap this area of the blade with more fabric. The aluminum is 6160 and started as 2"x 1/8" flat bar. It was cut and polished, to cover this area which will take the brunt of abuse (lines, crew feet, etc.). The taper makes a neat transition from the tapered trailing edge to the relatively squared off upper sections and is a nice visual detail. The cheek profile is one I use pretty regularly. No sense making something without any style. If you're going to do it, it might as well look like you wanted it to be nice. Note the angle of the curves can't hold splashed water, everything drains off.

    This is how it looked as I was setting up the rig and testing the "swing" of everything (including the rudder). The upside down hull shows more of this aluminum stock treatment. It's not polished up fully yet (temporary screws and all), but it's close. This strip runs full length and was a 4" wide flat bar, cut to shape for the centerboard slot, fore and aft taper, etc. The last image is more of this aluminum stock (2") where I'm fitting a couple of turning sheaves, so halyards can be lead aft, below deck. Mounted on a bulkhead, just forward of the mast, the lines drop down through the deck. This image shows the stock unmolested, as I set it up. You can see, it needs lots of finishing to get a reasonable shine. Simple to cut, bend, machine, etc., it wears well, can be refinished, etc. 400, 600, 800 grit then onto cutting compounds (two) and a rough and fine polish pad finish it up.
     

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  4. SukiSolo
    Joined: Dec 2012
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    Location: Hampshire UK

    SukiSolo Senior Member

    Nice job PAR, a real shoal draught beast!.

    I too prefer to recess the side cheeks of the rudder fittings into the wooden part of the stock (if rules permit), just a bit neater and smaller (lighter) fittings with no loss of strength. It seems to me that a lot of slop or potential slop is eliminated and the retaining screws or bolts are much more simply used as a clamp.

    Not convinced with the double gudgeon idea as the strong part of the pintle is at the base, but certainly can't do any harm. However I do prefer the pintle gudgeon set up to a single long plunger pin which should it bend is a true PITA to remove...;) Again a proper stop down must be used and tapered pintle if it will ever need to be shipped in a seaway but these are small in comparison with trying to extract a bent long pin out of a gudgeon ggrrrrrr....
     
  5. LP
    Joined: Jul 2005
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    Location: 26 36.9 N, 82 07.3 W

    LP Flying Boatman

    Come here my little beasties.

    Just jacking around.

    I was figuring out a way to trim my deck edges without a whole lot of bother. The deck to topsides angle varies from just about square at the bow to about 65 degrees at the transom. I needed a tool to cut a variable angle with minimal hassle and little adjustment.

    This is the little beastie that I came up with.

    image.jpg

    The 25 degree wedge gives me a 65 degree cut and if I rotate the router 90 degree axially, I get a 90 degree cut. Starting at the bow, the router is oriented to lower photo and by the time I get to the stern, it is oriented to the upper photo. It worked slick and the angle of the cut was modified on the fly for a nice, clean deck edge cut.

    Easy, peasy.
     
  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I wouldn't be able to build anything, if I wasn't able to make or modify tools. I have several different wedges I use on my laminate trimmer, for just what you've done Greg.

    That rudder was a compromise. I wanted to install a "slice 'o pie" board, within the rudder, to improve aspect ratio on upwind legs, but the client said no. This made the build a lot easier, but it'll be a "hard mouthed" beast in stiff winds as a result of his choice. Knowing this, I made the cheeks, extension and tiller from oak.
     
  7. LP
    Joined: Jul 2005
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    LP Flying Boatman

    I was a little surprised with the rudder profile. I did something similar on my first built to keep the flow separation low in the water. I didn't light the feel of it and subsequently rounded the trailing edge profile. You have probably told me what hard-mouth is before, but I'm not totally sure what you mean.

    On another note: I don't know which splinters worse, meranti ply or sawn Douglas fir. I've been picking up splinters like crazy with the meranti. Here is the latest, bestest one. I didn't know which way to pull it so I just cut the skin. :eek:

    image.jpeg
     
  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Hard mouthed is easier to feel than describe. Gaff cats are most known for this behavior, but barndoor rudders seem to bring it on as much as anything else. As wind strengths increase and helm pressures rise, the amount of pressure on the tiller seems disproportionately higher, than other rig/helm configurations. For example, I had a old cat boat, with the prerequisite barndoor, but since it wasn't competitive any more, I put on a kickup spade and instantly found the boat much more manageable. I can remember pulling so hard on the 1" diameter aluminum tube, I used to replace the broken mahogany tiller, that I could see enough bend in the tubing that I thought it would break or at least take a permanent set. The replacement spade had a small amount of balance (10%), but much higher aspect and an elliptical tip. It didn't make nearly as much noise underway, was a softer and more responsive helm and seemed to be crisper with input. Pressure in building wind strengths was dramatically reduced, bla, bla, bla.

    Which rudder profile are you surprised with? I'll assume the one I posted and this was a variation, compaired to others in it's class. A lot of folks use a big trailing edge radius (usually bringing up the bottom of the blade), to soften up the helm, but I've found you do soften the helm pressure, but also lose some control, especially heeled. I elected to keep the trailing edge perpendicular to the LWL and a tighter lower corner radius, so it would stay engaged as long as possible, with less bleed off and I used a nearly 5' long, massively thick tiller to handle it, on a 13' LWL boat. Doesn't seem necessary, but it had about 118 sq. ft. of area (all forward) and trust me, in 12 knots of wind, you'll be grateful for a 5' long tiller. Also the blade is much better shaped, compaired to most barndoors, which are often just flat plates of squared off hunks of lumber. I f the boat had been for me, I'd have hung an under belly kickup spade and truly solved the issues, instead of bandaging issues.
     
  9. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    Couldn't agree more about your rudder comments PAR. Though one thing that helps especially on a cat rig is IF you can move the CLR back, angling a c/board or sliding a daggerboard aft. The rudder pressures are a lot more reasonable even with a good vertical leading edge blade. With a highly swept back or very low A/R it is almost imperative, 'less you really enjoy arm workouts...;)

    I think I'd have been tempted to use a hinging wishbone tiller, but I'll bet your client did'nt want that either....;)

    LP, as long as you can see the splinters count yourself lucky, it's the ones you can't see but can feel that are the worst..:)
     
  10. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Yeah, this client was difficult. I would have put a board in the blade, if to keep the profile of the bard door. On shoal draft boats, it's hard to get significant enough of a skeg profile to carry some lateral load. Balance helps, but this can't be used behind a skeg, only below, defeating the shoal nature. It's a dog chasing it's tail.
     
  11. LP
    Joined: Jul 2005
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    LP Flying Boatman

    Toerails.

    The deck is completely installed. I'm waiting to cut the forward hatch until I'm done up in the eyes of the boat; some minor structure up in the chain locker and possible guides for stepping the mast. I'm really chomping at the bit to get the cabin sides on, so I'm trying to keep my haste in check to complete other tasks now that would be hard and messier later on.

    One of those tasks is the toe rails. I'm using two pieces per side to get the shape I want. A trapezoidal piece that is 1 1/2" tall by 1 1/4" on the bottom and about 7/8" on top. The sides taper in at about 15 degrees and match the deck to topsides angle nicely in most places. I used spruce to keep it light. The upper cap piece is about 3/4" thick by 1 1/2" tall. I put a 15 degree cut on the bottom edge so it matches the lower piece on the outboard side. It's fully radiused on top so I'm hoping to be able to wrap the entire thing in glass easily. The inside corners to inboard are also filleted to help in this regard.

    I'm also prepping the cabin sides. Where the cabin sides mount to the deck carlins, I've managed to create a tapered gap So I'm adding tapered fillers to the area to reduce the amount of glop that I will have to use when attaching the cabin. I will also laminate 6 oz. glass to the cabin sides before install.

    A view of the port toe rail and the tapered shim being glued in place.

    GOPR0214.JPG
     
  12. LP
    Joined: Jul 2005
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    LP Flying Boatman

    A couple more pics.

    Laminated and fill coated the cabin sides. Laminated the side decks and toe rails with 6 ox.

    My draping plan worked and I only had to do a couple of small slices to get the cloth to lay down on the steps in the toe rails. The aft ones any ways. I still have to laminate the after and fore decks.

    Nope, the cabin sides aren't on. A little dry fitting before the big day.


    GOPR0224.jpg GOPR0218.jpg
     
  13. LP
    Joined: Jul 2005
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    LP Flying Boatman

    I put on the starboard cabin side today. No pics, yet. It went in surprisingly well considering is an unwieldy 20' long piece of substance. I buttered up the forward 2/3's of the deck carlin with some nice thick stuff, expecting to scoop up the excess and run it on the last 1/3. As it worked out, most of the squeeze out was gathered up and worked into the more gappy areas forward before those areas were screwed down. The aft portions of the cabin sides become the cockpit coamings and have no structure to keep them from being pulled away from the carlins for easy goop smearing. This done, the coaming is let go to settle into place. Once screwed down, the excess goop was gathered up and used for finger fillets on the deck perimeter. I always like to have a plan for the excess. Especially, for operations like today. You just have to lay on the goop if you want to get good squeeze out everywhere. My second back up for excess goop today would have been an initial weave fill on the deck sheathing.
     
  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    By now, you should be able to mix up a batch, guesstimating how much goo you'll need and when you do actually lay it down, you have nearly exactly what you needed for the particular task. I've been able to do this for some time and still am amazed at how accurate I can be, simply making a guess at how much stickum, including thickening agents I need for a specific task, so you shouldn't be too surprised, just experienced enough.

    Those rails look very nice and I usually employ a trapezoidal section too. It's one of those areas where you can truly affect the look, without a lot of effort and conversely, can really screw the pooch, if you get the shapes wrong. They look fine, good job.
     

  15. LP
    Joined: Jul 2005
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    LP Flying Boatman

    After dry fitting a half a dozen times, I had my strategy pretty well laid out for these beasties. They were to drop in behind structure in a couple of places forward and were free to flop around freely aft. I made sure the clearance cuts were adequate so I didn't scrape out the wet epoxy as the cabin sides were slid into place. While the structure added a level of complexity in putting the the sides in, it was also a great set of extra hands once the piece started to drop in. Flexing the forward sections in, I was able drop the sides in with out disturbing the applied epoxy. I left the aft sections dry so that area could drop in, flop around and do what ever without creating an unholy mess. It also served as initial indexing in getting the unit aligned for attachment. I will probably smear stuff a little farther aft on the second one as it was a little tight where I left off yesterday.

    I can certainly do the second side in two batch mixes instead of three. It helps that I can keep the shop cool and keep my batch usable longer. I'm still leary of bigger batches, especially if left sitting around in the pot. I do the tricks to keep them from kicking off. I warmed it up to 58 degrees yesterday for comfort, but then reset it to 50 so the shop would be cooling through the process to keep the batches cooler.

    Thanks for the comments on the toe rails. I was 50/50 on whether to put on the second piece. It's a nice piece of straight grained Douglas fir that i may finish bright for some accent.
     
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