The "Sib-Lim" Challenge

  • 27 Jan 2015 03:47
    Reply # 3210962 on 3144241

    I've been working away on this design, and I've made a personal photo album of images taken from the .dxf construction drawing and the .fbm Freeship 3D model here. If anyone would like the original .dxf and .fbm files, please email me.

  • 12 Jan 2015 21:06
    Reply # 3195353 on 3144241

    How would you suggest bonding the plate to the lightning protection system? Through-hull bolts doesn't sound very attractive to me. 

  • 12 Jan 2015 18:25
    Reply # 3191191 on 3144241

    An excellent piece of writing, Dave! Thanks.

    Considering how, in VOASI, Annie stresses how important it is to invest in good equipment Now, so that you don't have to pay again, and more, Later ... well, using this on Sib-Lim would appear to be a copper-bottomed investment.

  • 12 Jan 2015 17:07
    Reply # 3191103 on 3144241

    Dave,

    Thanks so much for writing that up! Between the conversation here, and that new blog post, so many blanks are filled in. One question that comes to mind – but maybe I missed this – is about expansion and contraction. Do you oversize the holes for the screws, the way one does for Lexan? If so, by how much? And have you had any issues with warping, if the temperature goes up from one source or another?

    Thanks again,
    Shemaya

  • 12 Jan 2015 09:04
    Reply # 3189485 on 3144241

    I just posted a reprise of all this on copper plate, somewhat better organized, and a couple illustrations here:

    http://triloboats.blogspot.com/2015/01/copper-plating-plywood-hull.html

    Thanks for the stimulus... I've been putting this off for years!  8)

    Dave Z

  • 11 Jan 2015 21:22
    Reply # 3188524 on 3188436
    David Tyler wrote: Very interesting, and it's good to hear it like it is, from a man who knows from first hand experience. So I went to www.triloboats.com to learn more:

    What was all that about plate copper sheathing?

    Plate copper provides great mechanical protection for grounding, and non-toxic anti-fouling.

    Note: I've read that elemental copper is non-toxic (repelling growth via electrical field, which goes with nobility). So called 'copper' bottom paints use Cu2O (cuprous oxide) which is toxic. It is red, in this form, and does form along the waterline under patina... I try not to scrub hard enough to expose it (which suits my lazy nature).

    One more factoid: I've read that CuNi (copper nickle alloy) is preferred for marine use as having better mechanical properties,  less prone to electrolytic degredation, and stronger anti-fouling. Internet searches pop up hulls built of the stuff. More expensive, but something to consider.

    It is initially expensive (at this writing, it's running about $5.25/lb), but pays for itself quickly in haul-out avoidance (haul-out, yard fees, paint, brushes and such, treats = $$). It dissipates a lightning strike when bonded to your protection system. It's high on the galvanic scale, so you need fear no "hot" neighbor. If your motor lifts out, you are mono-galvanic (copper and bronze) below the waterline, so no zincs. It's heavy, so you'll make up some of the cost on ballast savings. Nail, screw or glue it on (be sure to test your glue on copper, first) and cover the chines with bronze angle.

    Could you expand on the "nail, screw or glue it on", please? I would guess at silicon bronze gripfast nails, but what kind of glue, or at least, sealant to keep the water out of the nail holes? Do you use hard, or half-hard copper sheet?

    Hi David,

    Thanks for the reminder that I could, once upon a time, get to the point!  8)

    Copper plate has been half-hard (rolled).

    It ranged in cost from $2/lb (LUNA 1997) to $5.25/lb (SLACKTIDE 2008 and present project). Cheaper than good cuts of meat, in our area, and about equivalent to a gallon of diesel. The spread between commodity and manufactured prices has ten-folded since '97.

    We've been happiest with #6 x 1+in  silicon bronze wood-screws, countersunk flush into the plate. Longer wouldn't hurt, but I doubt there's advantage as they seem to work mostly in sheer. We've used no pilot holes into the wood, but start with an awl punch. Tar (asphalt based, wet surface roof patch) and Irish Felt are favorite underlayments.

    Unfortunately, Irish Felt is getting rare and very expensive to obtain. We're trying a rubberized asphalt sheet adhesive roofing underlayment (GRACE brand... used in marine for gaskets in deadwood, and the like), this time. Haven't launched, yet, so no feedback. Some adhesion difficulties keep me from recommending this, yet (may work out, but not as positive as hoped, especially in cool weather application).

    Chances are, tar and about any solvent resistant fabric (preferably synthetic?) would do to replace Irish Felt. Tar alone has been used by others with apparent success. Some paint before tar, others tar the bare wood. I've heard that tar paper turns to mush, eventually. Most of the articles I've found the subject were from WoodenBoat Magazine.

    My second choice, as of now, is a thick 'gasket' of poly-urethane construction adhesive applied to the wood (can be relatively cheap in tubs, as it doesn't have to be highly elastomeric).

    Seawater intruding behind the plate itself seems to present no problems whatsoever.

    The theory of these underlayments is to seal the fasteners and prevent water intrusion into the wood. My guess is that water slowly does intrude, with the methods we've tried, but aside from extra weight, doesn't seem to be a problem. One reason to go lighter Cu is in anticipation of acquired 'water-ballast' from bottom saturation. Could be only settle over the years for the usual reasons of middle-age-spread, and that water intrusion is minimal.

    We had a glue fiasco (quoted here from correspondence with a fellow considering epoxy);

    RE epoxied copper, I'd be apprehensive about expansion differentials stressing the bond. Not so much while immersed, but once dried out, especially in hot weather. But then, I've grown paranoid.

    I don't know if you heard about our fiasco gluing copper w/ polyurethane (on theory that elastomeric bond would be preferable)? Did great, both on tests and while dry. But once launched, virtually every plate failed. Lots of oxide intrusion patterns from the edges on those that were still partially adhered.

    Almost lost one, but mechanical fasteners along the chines saved the day. Ended up nailing (bleah!) over the PU 'gasket' (original glue, which remained firmly adhered to the ply).

    My hypothesis is that minute intrusion at the edges oxidized the copper, which voided the bond and advanced the leading edge for another round. All in all, it went quickly. Possibly some ionic interaction with copper and PU ingredients?

    We did not, however, acid wash our plate. It came protected with a 'mill oil' film, and was 'new penny' bright, We washed with acetone before gluing (best guess at the time, no precedents I could find). We'd certainly acid wash if trying again. While dry adhesion was excellent, it's possible an oxide film allowed the initial edge-failures.

    One advantage of screws (our present choice) is that plates are relatively easy to remove for inspection or maintenance.

    Bronze ring-shank nails are traditional with copper foil, and they work well. Problems, to my mind, is that they're harder to sink flush (overcoming their ease of driving). If not sunk, they're like a field of small barnacles, and their heads could be prone to grinding off when grounding. Still, so far so good on SLACKTIDE's fix at six years despite rough living (we countersunk the nailheads, slightly, with a flat-ground bit).

    *****

    We first started thinking along these lines when a 125 yr old schooner hauled out next to our project (1st boat). It had been coppered with 1/16in nailed over Irish Felt (no extra tar), and was just now starting to 'perish' (holes showing). Never recaulked in all that time, and the owners were apprehensive about what they might find.

    As it was pulled away, a like new, DRY bottom was revealed!  Local caulkers (pronounced 'corkers' out here) pulled some cotton (and oakum?) and said it didn't need reworking! 

    No one could tell if it had been initially oiled (no paint), so they went for it this time round (don't remember the oil), new felt and copper, and away they sailed.

    Leaving us VERY impressed greenhorns in their wake.

    Now, so far as I know, we're the only ones who've tried it with either plate or foil on plywood - would love to hear of other experiences!

    *****

    If you're interested, for another project I worked out a scheme for plating a 5 panel (flat bottom) hull, with the grounding plate protected by 90deg bronze angle. Come to think of it, I'll do a post on copper plating, soon, at triloboats.blogspot.com.

    Hope this helps!

    Dave Z


    Last modified: 11 Jan 2015 21:29 | Anonymous member
  • 11 Jan 2015 18:36
    Reply # 3188436 on 3188027
    Dave Zeiger wrote:
    David Tyler wrote:
    Shemaya Laurel wrote:

    Copper on the bottom is not in the running? Expensive initially, but then no more buying bottom paint… And the five panel hull would make copper sheathing so easy!

    Shemaya

    Wouldn't that be nice, Shemaya? I would choose that option, on a high budget, but a quick look at prices indicates that enough 1/4" hard copper plate to make a grounding protection plate alone would cost $1500 USD.

    As shoe-string sailors, thought I'd put in our two cents for copper plate.

    We're on our third Cu-plated boat, now, and are down to 3/32in bottom, 1/16in side plate, which cuts the price to less than half. We ground our barge hulls in some mighty rough conditions, and it's stood up well. So long as it's solidly backed by wood (or what-have-you), it's very tough stuff.

    If we had our druthers, I suppose, we'd probably go for 1/8in, but that's 25% more cost for little extra protection. The increase is weight and ultimate longevity.

    Our first Cu boat is now 17 years old, and the thinner side plate looks great (bottom looks practically new). It was a rockered AS hull, and we used 1/4in plate at the low point of the curve, and 1/8in, uphill from there.

    Anti-fouling has been very effective... we scrub light slime two or three times a year or hang out in fresh water for a few days and kill it (sloughs off when we get under way).


    Very interesting, and it's good to hear it like it is, from a man who knows from first hand experience. So I went to www.triloboats.com to learn more:

    What was all that about plate copper sheathing?

    Plate copper provides great mechanical protection for grounding, and non-toxic anti-fouling. It is initially expensive (at this writing, it's running about $5.25/lb), but pays for itself quickly in haul-out avoidance (haul-out, yard fees, paint, brushes and such, treats = $$). It dissipates a lightning strike when bonded to your protection system. It's high on the galvanic scale, so you need fear no "hot" neighbor. If your motor lifts out, you are mono-galvanic (copper and bronze) below the waterline, so no zincs. It's heavy, so you'll make up some of the cost on ballast savings. Nail, screw or glue it on (be sure to test your glue on copper, first) and cover the chines with bronze angle.

    Could you expand on the "nail, screw or glue it on", please? I would guess at silicon bronze gripfast nails, but what kind of glue, or at least, sealant to keep the water out of the nail holes? Do you use hard, or half-hard copper sheet?

  • 11 Jan 2015 08:32
    Reply # 3188027 on 3179803
    David Tyler wrote:
    Shemaya Laurel wrote:

    Copper on the bottom is not in the running? Expensive initially, but then no more buying bottom paint… And the five panel hull would make copper sheathing so easy!

    Shemaya

    Wouldn't that be nice, Shemaya? I would choose that option, on a high budget, but a quick look at prices indicates that enough 1/4" hard copper plate to make a grounding protection plate alone would cost $1500 USD.

    As shoe-string sailors, thought I'd put in our two cents for copper plate.

    We're on our third Cu-plated boat, now, and are down to 3/32in bottom, 1/16in side plate, which cuts the price to less than half. We ground our barge hulls in some mighty rough conditions, and it's stood up well. So long as it's solidly backed by wood (or what-have-you), it's very tough stuff.

    If we had our druthers, I suppose, we'd probably go for 1/8in, but that's 25% more cost for little extra protection. The increase is weight and ultimate longevity.

    Our first Cu boat is now 17 years old, and the thinner side plate looks great (bottom looks practically new). It was a rockered AS hull, and we used 1/4in plate at the low point of the curve, and 1/8in, uphill from there.

    Anti-fouling has been very effective... we scrub light slime two or three times a year or hang out in fresh water for a few days and kill it (sloughs off when we get under way).

    Plate fares much better than the copper powder / epoxy systems we and others have used in our neighborhood, whether DIY or commercial. Growth is much healthier and better attached for them. They require sanding every so often (nasty job) to expose fresh copper. Between sandings, they go from not-as-good to barely effective as the exposed copper perishes.

    Importantly, we've had zero growth inboard of the chines (this still surprises me). This saves all need to access the bottom, short of damage, which takes some doing. Ours have been 'square boats', though, so let much less light below than dead-rise hulls. My guess is the low light starves already stressed growth. I don't know how a narrow, flat panel would fare, in this regard.

    Cost-wise, the initial outlay is considerable, but it pro-rates well. Especially if haul-outs are either mandatory or preferable for other reasons. Costs for haul-out, materials, yard time, and -if you're like us - pizza, beer and other lubberly salves to the trauma of being ashore... it all adds up. A few years of that, and the copper is paid for.

    Also, the mechanical protection that Cu plate affords a wood hull ranges from a good return to priceless. It's fantastic, on-board insurance! Costs of repair in a hard grinding... er, grounding (plus, again, all the associated yard expenses) can easily exceed the initial outlay for copper.

    And another, often overlooked feature is that it's a durable investment in negotiable metal! At resale time, if any, you can count at least the scrap value of Cu into the price, and recoup a considerable portion of your investment. If you're fortunate (as we were with LUNA), it's worth more than you paid!

    Don't forget to subtract from Cu costs those of (matching) ballast, epoxy, and Cu powder, not to mention epoxy related tools and safety gear.

    While we admittedly cringe when we pay for the plate, we are completely sold on the return. In savings in labor, peace of mind, and freedom from yards/legal alone, it pays for itself before it hits the water.

    And copper prices are currently crashed/crashing... a buyer's market!

    Dave Z

    PS. Our current boat, still under construction, is a T32x8, meaning a lot of plate for the size of boat. It's copper came to $9K, but we bought at a price peak (our usual luck), so it's already lost 'value'. That amounts to about half the price of the boat, all found. In up front cost (in our area) it will pay for itself in about 5 years. Worth every penny.

  • 09 Jan 2015 19:39
    Reply # 3186911 on 3185542
    Annie Hill wrote:And I confess that I rather like short fat boats
    That made me think of Quidnon, which doesn't meet your aesthetic requirements and is too large, but there might be interesting ideas there that could be plundered.

    Yann Quenet has developed a liking for scows, too.  Skrowl is too small, though, and Skrowl 900 too big.  A 7.6 metre version scales to the desired displacement.

    Last modified: 09 Jan 2015 20:23 | Anonymous member
  • 09 Jan 2015 12:01
    Reply # 3186533 on 3183945
    David Tyler wrote:

     

    Now that I have Freeship to work with, I've been able to model the hull and deck,


    It looks very good to me!  "A picture worth a thousand words"! 

     

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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