efficient 10m displacement powercat (build thread)

Discussion in 'Boatbuilding' started by groper, Apr 15, 2012.

  1. masalai
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    masalai masalai

    Hi Groper,
    I hope to be down on my boat on this Saturday (24th) I have "killed" my mobile phone as it was giving me the s41ts... I check my emails usually early morning and late afternoon if you need to get in touch...
     
  2. groper
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    groper Senior Member

    Drop in, ill be here saturday...
     
  3. groper
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    groper Senior Member

    Ok im ready to start putting the deck together, and i need to plan as much as possible beforehand, so ill have less work later on and in the long run.

    So its best i plan now for;

    hatches and locations, with doublers if nessesary, hatch gutter recesses perhaps?
    deck cleats and high density core inserts, how big do these need to be?
    stanchion bases (if any) or solid glass stanchions,
    bow roller high density inserts, again how big and how much glass???
    windlass inserts and doublers if nessesary???, how much glass for these?
    a method of attaching the trampoline up front (might not have a tramp yet so still unsure),

    What else should i plan for that goes in and on the deck?
    If anyone has any ideas for making the above assembly easier please let me know!

    The plan is to set the whole thing up with all the above considerations, then infuse it so i wont have to secordary laminate all those little things later on... itll be made in 2 halves, joined down the center of the boat...
     
  4. michael pierzga
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    michael pierzga Senior Member

    Composite stanchions sound troublesome. A maintenance issue for the rest of your life.

    Also stay away from stanchions embedded into the deck. very difficult and expensive to repair.

    Bolt down ss bases and ss stanchions are always best . When you abuse them they bend. SS is also resistant to chafe.

    With your Cored lightweight topsides you should investigate strategies to spread the fendering load..no point loading. I see many cored topsides damaged from fender point loading. Your advantage with a cat is that your topsides are flat slabs as opposed to a monohull with hips so you naturally distribute the load.

    Another source of sandwich damage is shipyard handling.


    For anchor gear, make everything in the system massive, with the ability to handle two anchors from the fitting if needed.
     
  5. waikikin
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    waikikin Senior Member

    I agree on the staino hardware, composite stanchions/cleats/chainplates etc are a SL of work when 4 bolts, drilled holes & sika sort the installation, a slight countersink to the external side of the glass leaves a nice little grommet of sealant around the bolt too. Interfacing point loads to foam sandwich needs some attention, closing out the core is nessesary, sometimes a simple "bog" annulus is all thats required or 8-20 layers of 856g quad for at least 2 x the dimension of the base of the fitting thats going on & backing plates, it depends but I'd rather bend or break a fitting before the boat. Another thing worth putting in is dedicated jacking points to the underwing & hull bottoms- in line with your connective bulkheads, one day your going to have to move/slip/transport your boat & not putting a crushable core in line for that is a good idea. Fenders & fender boards are a must to bridge when berthing agaist piles & Balsa topsides deal with smaller "parking" impact better than foam- larger impacts are a little different. Jeff.
     
  6. michael pierzga
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    michael pierzga Senior Member

    Damage I see on multihulls is not always on the dock side. Cats are so beamy that other boats coming in smash into the cats free side,. SMASH usually means tearing up stantions and pulpits as the incoming boat skids along your topsides.

    Another reason to have very robust stantion installations , particularly amidships, is that this is the location of all fenderboards, fenders. Plenty of load on the entire lifeline system

    And make your fenderboard long....equal to the distance between stantions...so that the board correctly nests on the lifelines and so that when hung the load of the board is on the stantions, not the lifelines.

    Fenderboards double as fish cleaning tables, boarding planks , dingy lifts.....
     

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  7. groper
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    groper Senior Member

    hmmm... this boat is built light, theres no hope of resisting damage from abuse... it will be insured and if someone smashes it, well they can pay for it or ill claim on my insurance, i cant weigh it down with heaps of reinforcing everywhere or it wont perform like i want it to.

    im a little weight paranoid on this boat... i have to keep everything light... The composite stanchions ive been reading up on say much stronger than stainless, and they will bend and spring back under heavy loads...???

    [​IMG]

    no rust, no bolts, no backing plates and the like, no leaks... i cant see any maintenance issues at all really? i thought i could just glass the rods to the hull in a similar fashion to a chainplate, by wrapping glass around the tubes and feathering it out into the surrounding hull or deck area? Other methods use a spigot tube or embedded sleeve glassed into the deck...

    For the other stuff, i have some coosa board off cuts that ill set into the foam core as a high density insert for bolt down hardware... but how much bigger than the hardware base do they need to be and how much extra glass???
     
  8. michael pierzga
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    michael pierzga Senior Member

    The stainless stanchion deformed and released its loading. The composite stanchion remained stiff and it just tore a hole in the side of your boat !!!!!!!!!!!!! When a fittting is overloaded something has to give.

    For me its better if the stanchion fails or deforms before structural damage to the deck or shear clamp occurs.

    Embedded stanchion bases are trouble over the long term.

    Maintenance means paint...or varnish, used over the composite stachion. It chafes or burns in the sun.

    Naked carbon covered by poly varnish is a nightmare to maintain. Im refinishing poly varnished carbon components this week. time consuming. The previous finish lasted 3 years.
     
  9. Charly
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    Charly Senior Member

    Groper, a guy in Holland is building a Richard Woods design with glass rod stubs embedded in the hull for the stanchion bases. The stainless stanchions then fit over the rod, which stick up a few inches. He uses a glass backer and a glass doubler the same size up on the deck, with a hole drilled through them for the rod, which is inserted and bogged in, with yet another glass backer then glassed over the first one down underneath. He did a test and the stainless tube bent under load with the glass stub ubharmed. Seems like the best of both worlds,

    http://www.albonham.demon.nl/

    go to the 2012 section and click on "railings"
     
  10. Steve W
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    Steve W Senior Member

    That would certainly be a strong and leakproof method, if you stick with nice tapered ss stanchion tubes they will be the weak link as noted but they are not too expensive to replace, at least here in the US from Garhauer.

    Steve.
     
  11. waikikin
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    waikikin Senior Member

    I love a test like you've pictured, what kind of weight hit is there on the staino? It's up to you to do the analysis on time/weight etc, main thing is to keep the humans on board;) Jeff
     
  12. masalai
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    masalai masalai

    Groper,
    My stanchions are composite and one took the load of an anchor that refused to release, and bent to near 90 degrees and returned to normal and I defy you to tell me which one (of the two aft stanchions)... On a lightweight 'duflex' type construction, (end-grain-balsa or 'green-foam'), the only way to go is embedded and taped inside - - - as ss pads will require substantial plates and stiffening to hold the bolts... 3 and more times the weight penalty and not very robust...

    The load I put on my stanchion was severe as I was trying to "unbury" the anchor by 'running back over it' - it stopped me dead... - Next pass it came up...
     
  13. michael pierzga
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    michael pierzga Senior Member

    In the end its always up to the builder.

    If lightweight is paramount then why not. For me its always educational to observe a first class yacht age thru its natural cycle.

    Check out Berg Viking...1980, Round the world racer, next to the modern technolgy.

    Will we get to observe the modern yacht thru its life cycle ?
     

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  14. groper
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    groper Senior Member

    Ok ive decided to build my own hatches... so all i need is a 3mm rebate in the deck around the hatch lid to accept the gutter molding... the gutter molding will be made as shown in the following detail drawing on a male mold. Envisaged method is to cut out the hatch lid from the deck, along the rebated line, and re-use the cutout peice as the hatch lid. A drop in gutter molding is then epoxied into the rebate. For plexiglass hatches, a peice of 10 or 12mm plexiglass is cut to size, then directly hinged to the deck, with seals of rubber or foam tape etc on the gutter molding. Gutters will be plumbed to nearest egress...

    [​IMG]


    The deck was layed out and everything marked out on the table this afternoon, need to cut out all the high density inserts and rout the rebates next before i can infuse anything... ill post some more pics when i have something more to show...
     

  15. michael pierzga
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    michael pierzga Senior Member

    Something to consider with hatch frame gaskets is UV light. My experience is that when UV can penetrate the perspex, the rubber gasket rapidly deteriorates.

    Any strategy to keep UV off the gasket is worthwhile.

    Silicone gaskets seem to be the most durable.

    Flush hatches are high maintenance. Stand proud hatches give a good toe hold when working in deck and are easier to keep watertight.

    Avoid using contact cement to adhere gaskets.

    Hatch frame waterways on flush hatches e prone to clogging. Use many drains and make it easy to maintain these drains.
     
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