Blackrock 24 (Build)

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

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

    LP Flying Boatman

    I've thought about injection method, but have come up dry with regard to an implementation. Syringes sound like a start, but makes me think of very small volume. I was mixing 6 oz batches and I think that would be a nice quantity to continue to work with. I've found some aircraft quality pneumatic systems, but the initial investment is a bit rich for an experiment. The caulk tube that some marine grade sealants look like they would work nicely and be reusable. By the time I get to the bottom of one of these the sealant has gone hard and removal is questionable. I would certainly be open to input on sourcing caulk gun sized tubes that I could fill and maybe reuse.

    I'm not so sure about taping the back side. I feel that this would limit the epoxy penetration as air bubble could get trapped. The clean up on the inside is quite easy and doesn't take a lot of time.
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Your questions are similar to the ones I had before I tried it. If you angle the gun back and let the goo pile into the gap or groove, if flows in, fills the gap and you just have to monitor the "feed rate" at which you push the tool along. It's surprisingly intuitive once you do it. It'll also change the way you apply caulk too.

    Harbor Freight, Northern Tools and other cheap tool supply outfits sell a pneumatic caulk for less then $30 gun. I have a better one, but my first was a Harbor Freight deal. It accepts a standard 10 ounce cartridge, which I buy in bulk for pennies each and being plastic, you can pop out cured goo and reuse. They are a real hand saver if you have a lot of really stiff goo to apply, like 3M-5200. A few hundred feet of a standard hand cranked caulking gun, with 3M-5200 and you're hands will chew themselves off your arm and bail on you.

    The back side tape thing is something I regularly do. I have a new lapstrake build I'm just starting and the seams will be back taped, before filling with thickened goo. Yep, I'll use the pneumatic caulk gun and I'll be grateful for it. Try it with a regular caulk gun on a test gap and see what you think.
     
  3. LP
    Joined: Jul 2005
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    Location: 26 36.9 N, 82 07.3 W

    LP Flying Boatman

    A picture is worth a thousand words.

    I've stopped planking to take care of a couple of items that are best done before the planking is complete and one because I got out the big wood and it just made sense. First of all, rather than make up a full blown drawing, I dimensioned what I needed in my CAD software and took a picture of it with my smart phone. Did it, done it and we're off like a herd of turtles.

    IMG_2920.JPG IMG_2921.JPG

    The thousand word picture and it's brother.

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    The external rudder support. This is my answer to having a raked transom and a vertically hinged rudder. The bottom ply straddles the rudder post for support and hull planking will have a concave profile, extending out to meet the bottom extension.

    IMG_2924.JPG

    I'm looking at having a metal "angle iron" mounted to onside of the rudder cheeks down low. This and the hull extension and a "flat" on an uppish portion of the rudder assembly will be used for hull re-entry.
     
  4. LP
    Joined: Jul 2005
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    LP Flying Boatman

    Finally got back at it for a couple of days. I'm about 40% planked. This round of planking I used tongue depressors as my gapping device. I started with toothpicks and found them to be fragile and sharp. I switched to a flat head nail that worked well. I left the pointy end hidden in the planks and left the head proud on the inside of the hull. This made for easy retraction, but I felt the gap was too big at 0.085" and the planks were subject to crushing in the vicinity of the nails when pressure was applied during nailing. I have a box of tongue depressors that I use for mixing sticks. These gauge out at 0.060" and their width protects the planks from crushing during nailing. This is a 13% smaller gap so that correlates to a 13% reduction in gap filling material. At the turn of the bilge, I'm looking at going with an even smaller gap as the outboard side of the gap will be even larger. I didn't notice any increase in difficulty in back filling this smaller gap.

    Here is a pano shot. It warps the image, but there isn't enough room to get a good bow to stern shot.

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    A normal image of the progress.

    IMG_2953.JPG

    These appendages have been mostly shaped. The gap between them will be where it kicker motor lives. I'm going to "fine up" the leading edge sections of the rudder post some more.

    IMG_2947.JPG

    I feel that the planking is going at a good pace. When I get time to work on the boat, I feel that the plank is going on relatively smoothly and I can see the progress at the end of the day. The next few planks will take a little more time as I need to taper the ends. I'm getting some edge set in the forward sections and there is a lot of twist in the aft sections going around the turn of the bilge. The next half dozen planks should get me through technicalities.
     
  5. PAR
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    PAR Yacht Designer/Builder

    Glad to see you back at it. The tongue depressor seems a real good idea. I've just started a new lapstrake build and will be planking soon.
     
  6. LP
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    LP Flying Boatman

    Sounds great. Is it your own design? I hope to do one sometime.
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I've modified a Chapelle rendition of a MellonSeed. It's been enlarged about 20%, had some volume removed and also moved a bit aft. I've raised the freeboard a little, also changed the rocker a touch and flattened the deadrise forward a wee bit, to improve upwind handling. So, technically, it's an enlarged MellonSeed, though with enough changes I've given it a design number and I'll add it to my drawer of stock plans.

    This shot shows the initial lineoff, which isn't finalized yet. I've since "let" the battens into the molds and am picking up plank templates now. I do new lap builds a little differently then most. I use battens to support the thin (1/4") planking, but they don't stay in the boat, like they do on other builds. The just keep the planking from sagging in the flatter sections, between molds (24" centers). She has a single "plank" keel arrangement, which saves the bother of a rabbit on a keel. I have a few designs that employ this. It makes beaching easier too.
     

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

    LP Flying Boatman

    At some point it definitely has to become your own design. I'm sure that Howard doesn't mind. ;)

    I took a different tack the other day. Fairing has been on my mind and I've been waiting until I had a "fair" amount of plank on the boat to do something with it. Instead of fairing the whole boat all at once (DAUNTING), I plan to do it piecemeal (thirds maybe) as the planking progresses to break up the process a little bit. I don't expect to get a final fair at this stage, but I can even things up a bit before moving on the next section of plank. I messed with my low angle for a while, but made little progress. I eventually took out my two handed plane and finally fell into a something of a rhythm that took me down the side of the boat. I ended up setting an aggressive cut, made stokes at about 45 deg to the grain and held the plane between 45 and 30 degrees to the grain. I felt this took off the high points rapidly and took hull shape into account in both the lateral and longitudinal directions. Once I had rough fair, I moved on not wanting to invest too heavily in the fairing process right now. I may end up masking the faired sections to keep epoxy drips off. Part of the work in fairing the hull is removing the hard layer of cured epoxy that is left from the gap filling stage.

    image01.jpeg

    I've also changed my plank joint method. I've dropped the doweling process all together. I've made some clamping devices that I slip on the plank ends as I lay the planks up. It's two pieces of wood wrapped with packing tape and held together with a single screw that penetrates at the joint. I've improved the device to where I believe the results are highly acceptable. The first improvement was to grind off the screw threads in the vicinity of the joint to allow for a smaller gap. This was followed with 5 deg undercuts on the planks to make a joint that flairs open on the back side. With the planks clamped together and positioned, I hit the end of the loose plank to crush it around the screw to where the remainder of the plank ends are butting together. These clamps have to stay in place until gap filling is done and cured. I have to work around the clamps during the gap filling, but I think this is less of a hassle than doweling the planks to align them. This photo was taken before I starting undercutting the joints.

    IMG_2948.JPG
     
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Previously in this thread, we discussed taping the back of seams, so goo doesn't run through. Contemplating this new glued lap build, I've come up with a different solution. As the plank laps land on each other, invariably some gaps exist. You fiddle around with clamps and alignment, but eventually you just tape the back of the laps to control ooze out. The laps on this boat will be 3/4", I'll mark a thin putty knife 3/4" from the end of the blade and this will be the installation tool for the "lap seal". I'll align the planking as usual, then wet them out as usual, but as soon as I wet the laps, I'll place cotton kite string in the bottom of the lap, pushing it in with the marked putty knife, so I don't shove it through the lap. This will be a feel thing, as once I note some resistance to pushing the string into the bottom of the lap, I'll stop. Lastly, I'll further wetout the string, which will cause it to swell slightly, sealing the lap from further ooze out. Letting this kickoff, I can without bother back fill the laps with thickened goo, knowing it'll remain in the lap and not run down the inside of the boat. Food for thought . . .
     
  10. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    Nice work. Certainly looks like good work in progress. Must admit I've always scarfed stringers/strips to get the length but a stepped butt joint would be OK.

    Interesting beast PAR, reminiscent of some of our Edwardian sailing skiffs still occasionally seen on the upper Thames. I've got in the habit of covering anything I don't want goo to stick to with masking tape. If its a glue edge that I don't want to exceed spillage over it doesn't matter, I just peel off when half set. It stays on the tops of the temporary frames! If you are not sheathing later it allows neat end lines or limits for internal fillets, at the risk of eggs and grandmothers but might be useful for LP.
     
  11. LP
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    LP Flying Boatman

    Packing a joint with a line of cotton. Some things never change.

    The goo running sown the inside of the hull doesn't bother me too much. I've got easy access and it cleans up readily and is reused elsewhere on the hull. The problem I see is when I turn the corner on the bilge and the excess falls on the floor instead of staying on the hull. Your string idea has possibilities. Maybe something a little thicker like yarn in my instance.

    I've got one more task to complete before continuing with the planking. I was going to build the mast step directly to the structure, but I see it as a high wear area due to the constant stepping that will be required with each launch. I'm going to make a step plate from some white oak to take the stepping abuse. It will fit into a sort of cradle and be attached with a single simple screw to hold it in position while the mast is unstepped. I'm also going to have to whittle down the lowest portions of my forwardmost bulkhead. I've been test bending planks in this area and they are not happy right now. :mad:
     
  12. LP
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    LP Flying Boatman

    Thanks for the comments. Interestingly, the long scarfs are much more noticeable than the butt joints. I was doing 8 to 1's on my first build until my radial arm saw died. I switched to 45 deg cuts afterwards and to this day I still think the 45's look nicer than the scarfs. Of course scarfs are about strength not looks. I'm probably not as careful about staggering my joints as I should be. I try to have several planks between joints that are close and at least a 12 to 1 distance between adjacent planks, preferably more.

    Eggs and grandmothers. That's a new term to me. Something about runs and sags I'm sure. :eek:
     
  13. PAR
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    PAR Yacht Designer/Builder

    Line you mast step with HDPE or other high modulus plastic. It'll take the beating and can be replaced when it get worn out.

    From a technical stand point, you don't need to scarf the strips, though I've found cutting them at 45 degrees does help with alignment to some degree.
     
  14. SukiSolo
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    SukiSolo Senior Member

    Acetal is good too PAR. One brand name commonly used is 'Delrin'. It routs and saws up very well, a bit less woolly than HDPE. Only if you drill long holes will you discover how it manages to 'recover' and leave a tapered hole!.
    It is pretty good as a mast step material on small dinghies if of sufficient section. Good Polymer merchants should stock it in sheet and round bar, and a small offcut is often all that is needed.

    If I'm building new, I go for for the 1:7 scarf, but on a lot of plank repairs, that is an impossible ratio. Mostly I can get around 4+:1 and I've not had a single one come loose in 30+ years... That is using urea formaldehyde or epoxy adhesives, on clinker (lap strake), multi chine, strip plank in a variety of timbers and plys. Main thing with stuff like WR Cedar is to get good penetration into the end grain with the adhesive, as it is pretty sponge like on end grain. Like the 'soft' bits in Doug Fir!.

    It is not hard to build a 'scarfing jig' for a table saw, used to use one a lot when building racing sculls. But on those the strength was needed.

    The 45s' are fine for your purpose, still a significant increase in glue area and shear strength anyway. Plus a cohesive adhesive. Keep up the goodwork.
     

  15. latestarter
    Joined: Jul 2010
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    latestarter Senior Member

    This is a cryptic reference to a phrase "Don't try to teach your Grandmother to suck eggs".

    It has the meaning; Don't offer advice to someone who has more experience than yourself.
     
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