CSC 30 Catamaran- the coastal passage

Discussion in 'Multihulls' started by peterchech, Nov 29, 2011.

  1. DennisRB
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    DennisRB Senior Member

    I have only met 2 people who have used polycore style products on larger jobs (as opposed to smaller interior panels). One was the builder of the aft mast Lyra, the other was the guy who turned Wired into aft mast Zanataos (wonder if its a coincidence :p).

    Anyway the guy who built Lyra was very honest and seemed to indicate that the stuff had a severe lack of stiffness, so much so that he had to do a lot more work and weight addition to the boat. Even then it was a little too flexy for the rigging to work right. He told me this at a boat show where it was for sale.

    [​IMG]

    The guy who rebuilt Zenataos with extensive polycore sytle structure says the boat was lighter after he removed all the wires and poles. He assumed it would sit low and raised the water line. Now his water line is like 4-500mm out of the water. However he also remarked at the lack of stiffness. Have a look at the sag in the hard bimini! This boat is for sale and would make a great bargain with a lot of space. I think its kind of cool once you fixed the rig, which he has already started doing.

    http://www.boatdesign.net/forums/attachments/sailboats/101439d1436407785-aftmast-rigs-p1050150.jpg

    Not to say polycore is not a viable choice, but its lack of stiffness needs to be carefully be taken into consideration which will likely add even more weight.
     
  2. rob denney
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    rob denney Senior Member

    Swept back spreaders need either lots of prebend, jumper struts out the front or runners to stop them pumping in a seaway. Double diamonds are tricky to set up.

    Wood and carbon tube masts are heavy (the wood does not contribute much), expensive (the wood should be top quality, and there is a fair bit of waste) and challenging (although satisfying) to build well.

    8:1 scarff in ply is plenty and can be cut on a circular saw or stagger stacked and hit with 24 grit on a grinder. Any more angle and you will end up knocking/sanding off the feather edge.

    Almost all rot in ply boats starts at screw/nail holes. I would avoid butt blocks for this and convenience reasons. All screws should be removed and the holes filled with resin/runny bog with a syringe. Wiping bog over them does not fill/seal them. Nor does brushing resin.
     
  3. brian eiland
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    brian eiland Senior Member

    Basically I agree with you Dennis on both scores.

    Nether of these vessels had proper rigging design of their aftmast to facilitate tight forestays, and I believe it was not the intention of their owners/builders to attain that goal. If it had been their goal, more attention should had been paid to both the rig design and the hull design/construction.

    And if I remember correctly Lyra was built very much in the same vain as the early Prouts,...big open spaces that were less then optimum in their bulkheading and internal framing,...making for a loosy-goosy vessel in terms of overall stiffness.

    So I don't know that the polycore itself was the sole contributor to these vessel's stiffness. I don't recall specifically, but I also think there were some questions as to the joining of the polycore panels that was less than optimal?

    Weren't there a significant number of other boats built over in that area of the world out of polycore? I seem to remeber one VERY nice 50 cat I saw built up in Thailand with that material as the owner did not want the potential problems that might arise with the Duflex panels of balsa core??

    http://www.boatdesign.net/forums/multihulls/duflex-panels-atl-worth-21092-3.html


    http://www.boatdesign.net/forums/fiberglass-composite-boat-building/structural-panel-bulkhead-joining-question-45735-2.html


    http://www.cruisersforum.com/forums/f48/are-cats-made-from-duflex-panel-kits-strong-22948.html
     
  4. Gus7119
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    Gus7119 Senior Member

    Second build of model

    Ok heres the start of the second attempt after my sister threw my first attempt out after I left the model there when I was house sitting. After seeing that I had Posted Iso..... model and commented on it on my FB page she felt I didnt need it any more.
    Anyway just started it 2 days ago so a bit to go. I am building it to Leons specks regarding lwl and bulkhead sizes. I am yet to decided if I am going to do bridge deck at 700 or 800 above water line. The rear two bulkheads are not attached yet and I havent added the other bulkheads yet. The rear double bulkhead will take the stern beam that will be glued and bolted between these two bulkheads to provide extra stength and stiffness. They will be spaced the width of the rear beam and themselves made into a female mold to receive the bulkhead.
    This is just the start so that you can see I serious about the build. Looking at Iso.... model Im thinking that 30 to 35 ft may ve fine. I have grabbed many build ideas from many other designs whos build videos and blogs I have fastidiously watched and taken detailed notes and plans from. My wife reckons I should open a library with the amount of note books I have filled with design ideas. But now I am slowly implementing what I feel suits my buid the best and seeing if it works. Its a 1:10 model I am going to bog up and paint so my wife can see what the finished thing will look like.
    Now thats said on the many many blogs and build videos Ive seen of boats made with ply, from 6mm to 10mm hull sheets one thing seems constant to me. That is that for every 1000mm there will be a bulkhead. And in a few some builders have added a couple more. O this includes full and partial bulkheads. Now while I know this adds weight and in some cases a few builders have gone over the top adding say 3extra bulkheads shouldnt be an issue if Ive worked it out right or am I completely wrong? Also this is in boats outa ply not glass planked or balsa.
    Heres the start any input is good in put at this stage
     

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  5. rob denney
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    rob denney Senior Member

    Model looks good. The wobbly bits will come out when the deck goes on.

    What is the waterline beam and draft of the hulls (ie, no keels)?

    Single chine, flat bottom is easier, roomier and has more payload. Looks ordinary while it is being built, but once launched, only you will know.

    Bulkhead spacing depends on location, ply thickness/stiffness, panel height, furniture, compound curvature and number and thickness of stringers. Some ply boats have 3m between bulkheads, others half a metre.

    Not sure if you are going to build it like the model with fillets to join the panels, but if you are, think long and hard about the order of set up. At worst, you have 2 x 4 x 35' = 280' of filleting and taping, on your knees, working backwards, just for the chines.
    If you use stringers, it's easier, but they need planing, then a fastening every 150mm or so. Half of them can be clamped, but that still leaves 280 screws or boat nails (aka rot starters).
     
  6. brian eiland
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    brian eiland Senior Member

  7. Gus7119
    Joined: Dec 2015
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    Gus7119 Senior Member

    Cheers for that mate Interesting read. But as expkained Im going for ply glass as resale not a factor getting exactly what Id like is. Plus The fact is once the cabin an hulls are attached stiffened but som furniture I can the take my time on the final fit out making some compromises now and change when Im more financial.
    Have really enjoyed the process so far.

    Cheers
     
  8. Gus7119
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    Gus7119 Senior Member

    Mate Will get back to you re this. Anyone have any experience with the hulls program?

    Cheers
     
  9. Gus7119
    Joined: Dec 2015
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    Gus7119 Senior Member

    Anyone have a lead on these guys Gougeon brothers plans for Wood masts or anyone know how to get hold of their plans?
    As it stands I have almost finished model for internal design ideas as haven't settled on them yet. Andd will be running the final design through DELFTship to check out water line and other parts of tweaks. If I do make some. But been fairly happy with the layout Im homing in on. So if anyone has any hints about that program Im listening.
    Rob Denny so far I haven't changed anything much from the other guys model so am assuming my lwl and other calculations will cone out the same. After an initial run through on the Hulls program it seemed to sit luke the one from original pictures of build launch. But Im not 100% sure I get how that app works so hope this new app is a little better.
    Reall keen to find a plan from those brothers but it seems no one knows where to get them. And they have been heavily trialed on cats and seem to have a gokd record. Others Its off to strip an old mono.

    Cheers
    Gus
     
    Last edited: Feb 12, 2016
  10. Steve W
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    Steve W Senior Member

    The Gougeon bros have not offered those mast plans for sale for many years, liability issues I think. Meade Gougeon did replace the original wing mast on Adagio, his old stressed plywood Tri which he said was marginal with a new wood/carbon mast he built and described well in an issue of Their Epoxyworks magazine which you may be able to find online.

    Steve.
     
  11. UpOnStands
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    UpOnStands Senior Member

  12. redreuben
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    redreuben redreuben

    Gary Baigent is our resident plywood wing mast expert, I'm sure he has something that would work for you.
     
  13. Gus7119
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    Gus7119 Senior Member

    Thanls for the info Steve UpOnStands redreuben.
     
  14. Gus7119
    Joined: Dec 2015
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    Gus7119 Senior Member

    Decided on a few things input needed

    ok so kick up rudder on transom, is this so hard I thought easier then through hull Im avoiding as much through hull as possable. No daggerboard internally a kickup board on outside of hull between bridge deck with snap pin if hits anything. Flat bottom with small keels for handling but still run up on beach. This gives me an extra 200mm at the floor as well as no need for bilge.

    Still at this stage using ply but after long discussions with many here and a shout out to Rob Denney or his help behind the scene that may or may not change. But Rob has given me the confidence to build a mast carbon glass should be cool.

    Heres a Pic of the internal layout B$ I to cabin top on model. The starboard hull got a little wet so is wonky but Ill fix that before I finish it. Starboard will be owners cab with floor and step to bed with cockpit seat offset for extra space. the port will be just double bed port seat closer to hull center. Port birth just a bit of baord sitting so not cut to size yet. the forward compartments in either hull, Port will be a birth starboard dunny and shower, I am not having lockers forward of the mast beam that area will be a deck with lockers on it at hull top just under beam. Havent worked out windless yet will do so soon. With there will of course be a fore beam. But thats where its at.
    As for saloon u can see where kitchen goes and approx orientation of the area still playing with it.:)

    By the way I havent added the half Bulkheads to the model as yet my bad>>>
     

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    Last edited: Feb 16, 2016

  15. isladelobos
    Joined: Jun 2014
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    isladelobos Junior Member

    Gus.

    What is the engine place i suspect under these two rear seats?

    I can add more pictures.

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