Catamaran build with different core materials

Discussion in 'Multihulls' started by saltifinch, Mar 19, 2016.

  1. catsketcher
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    catsketcher Senior Member

    Foam is definitely NOT easier to work with in my estimation. The best thing for you to do is to build a few small projects. Whilst I would probably build in foam if I had to replace my large cat I love using ply for heaps of uses. My smaller cats have lots of ply in them.

    You can build a great boat out of cedar, ply or foam. There is no magic bullet that will make the boat fabulous. My 38ft cedar/ply cat has no rot and is fast and nice to sail. She is 16 years old this year. She does have a foam cabin and Duflex rear deck. As many will say - the hull build is only a small amount of the time required so don't focus on this too much.

    In Australia one of the major cat designers - Peter Snell - loves ply. He can build a boat very quickly and he sells them for good prices. He is a designer who really lives the life - building each one of his designs, getting out there and living in them and then selling them. Nice guy too.

    cheers

    Phil
     
  2. saltifinch
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    saltifinch Junior Member

    If only you knew how much time I've spent obsessing over Peter Snell's designs. I'm quite in love with the Sarah model personally.

    And I have absolutely no issues with ply/glass boats, they will last as long as any boat out there if done right and maintained properly. I probably am obsessing over the hulls too much, I've been pouring over videos for endless hours. I just like understanding technology inside out before I use it.

    And you're quite right, I may build a small catamaran first to learn sailing. And yes, it's retarded to build a sailboat without knowing how to sail. That's what the Google is for ;)
     
  3. rob denney
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    rob denney Senior Member

    It's pretty pointless discussing whether foam or ply is easiest to build with. Both take a long time, the fit out is a big, fiddly and mostly boring job. Both take a lot of physical effort, with lots of dust, mess and toxic materials. Neither has changed much in the last 30 years.
    Little or none of the above applies to Intelligent Infusion.

    Definitely try a sample of conventional building first, but make it realistic. Fibreglass sizable sections of the wall of your shed. First above head height, second below knee height, include some overlaps, then fill and fair them with a torture board. Do another piece on the ceiling.
    Add a fillet and tape to the floor to wall join and the wall to ceiling join. Then fair them in to the rest of it.
    To practice this part of boat building with Intelligent Infusion, pour 4 jugs of water (resin) into a bucket, add another one (hardener), stir vigorously, drop a hose end into it, make a cup of tea or open a beer and stand and watch for 40 minutes.
    Some blogs to read. These are written as the job progresses.
    http://www.fram.nl/ for why infusing foam without a mould is a lot of work,
    proa32.blogspot.com/ for how much work is involved in prepping and coating ply the way it is meant to be done,
    http://buildacat.com/bblog.html for the level of labour required to build a "low labour" premade-panel boat.

    Ply is a pretty good insulator, I would think twice before adding foam to it. Spend the effort on insulating curtains for your windows, eliminating drafts and a decent heater first.

    There are too many variables to make a sweeping statement such as ply is "far stronger" than foam/glass. Both are stronger than necessary in most cases, and in the few examples where strength is important (eg bouncing up and down on sharp rocks, hitting logs at high speed, bouncing off walls without fenders), neither is strong enough. The important property is stiffness, which is very much defined by thickness. Thick foam is much lighter and easier to build from than thick ply.

    If you are interested, email me at harryproa@gmail.com and I will send you enough information to get you started with some Intelligent Infusion samples. Might be able to help with a small catamaran to build as well.
     
  4. rob denney
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    rob denney Senior Member

    Glass will delaminate from foam if it is hit hard enough. Not usually a structural problem on a multi as they do not slam the way monos do. Dropping heavy things on deck is the usual cause. Local delamination does not need fixing unless it is in a critical area, or getting bigger. Fixing is usually pretty easy. Drill a hole at the top of the area and inject epoxy until it is full.
    More common is dents, where the foam gets crushed, but the glass stays stuck. These are even less problematic and are simply filled and painted over.

    The boat building foams are PVC. Corecell, Divinycell and Airex are the main manufacturers. They are all suitable, and have all been used for multis. Unless you are pushing the limits, I would go with the cheapest of these. There are plenty of other foams which can be used for non structural jobs, but most builders don't bother. We use polystyrene in the bows of the boats to absorb any impacts from hitting things.
     
  5. saltifinch
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    saltifinch Junior Member

    Thanks for the info Rob! That was the general consensus I had on foam, just nice to hear it answered by an actual builder as well.

    It's been strange hearing the word "styrene" so much in boat building. I worked at the refinery in Edmonton that is one of the largest producers of that stuff. Its sick how much money they make off that stuff. But now I'm starting to get a better understanding of its many diverse uses.
     
  6. Richard Woods
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    Richard Woods Woods Designs

    I suggest you contact the guys at the BCMS and get out sailing on a catamaran http://bcms.bc.ca/

    Carefully read what Catsketcher says. He is a very experienced multihull sailor/builder but is not in the multihull business so has no particular axe to grind

    To be a fair comparison don't just glass one side of your garage wall, infuse the other wall as well

    I always say a useful exercise is to make a foam sandwich tool box. You do all the jobs, cutting out glass, laminating - especially corners (the hardest thing to glass properly). Then make one in wood. You will have two useful boxes and have done all you need to know to build a foam sandwich or plywood boat.

    Use a pvc foam. Airex can be bent at room temperature, so is useful when making round bilge hulls. The manufacturers claim it is also tougher. Rigid PVC has to be heated to form curves, but won't go soft in hot weather as Airex can.

    You are right, the hulls are the easy part. A production yard could make a moulded grp 35ft catamaran hull shell in a couple of days. But it will take 2000+ hours to finish it

    So to save time go for tiller steering, not a wheel, outboard engine(s) not inboard, AA powered LED lights. etc etc

    I write a lot more on my website so won't repeat it here

    I mentioned my 35ft ply/epoxy catamarans in my last message. I didn't say that I am currently drawing a production Skoota 32 (the build of the first one started this week) which is built in infused foam/resin/glass

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  7. gonzo
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    gonzo Senior Member

    Injecting epoxy on a delaminated core will make a hard spot and produce concentrated stresses. That may lead to structural damage. Hulls and decks should be repaired to original specifications.
     
  8. rob denney
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    rob denney Senior Member

    This might be good advice if you are infusing using conventional build methods. If you are using Intelligent Infusion, it won't give you any useful experience as both surfaces (ie, outer laminate, inner laminate and core) are infused at the same time, at waist height. 90% of it is horizontal and the vertical bits are low and easily supported.

    This is the type of designer spiel that has resulted in so many unfinished owner builds.
    Building tool boxes does not give you any insight into the hours or physical labour involved in a boat. It gives you a small amount of knowledge on how to set up and glass small surfaces but very little else that is of practical use. It won't help you set up frames, fit furniture to curves, torture board, install fittings, glass large surfaces, scarph ply, bend foam, plane stringers, etc etc.
    Glassing corners is easy enough, fairing them is the problem(can't get the sandpaper in there). The solution is a system that does not require any wet glassing and corners that are all part of matching glue joins so there is nothing to fair.

    Which is why conventional production boats are so expensive and conventional owner built boats take so long. 2,000 hours is the estimated time to build a 60' harryproa using Intelligent Infusion. http://harryproa.com/?portfolio=harryproa-cruiser-60 A 35'ter would not take half as long, but close.

    Cool. Welcome to infusion land. Who is the builder? Specs and prices?

    Gonzo,
    Agree for large delams on lightly built boats. I was referring to hammer or heel size dents, which are more likely on cruising boats.
     
  9. bscatam
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    bscatam Junior Member

    For my design I have desided to use for hulls - 12 mm endgrain balsa with 1,5 mm okume veneer both sides for planks - hand laminated, for decks 19 mm balsa flat laminated on table (vacum baged or infused) same for bulkheads - 25 mm. As I am in furniture business, I have all eqyipment needed incl. hot pressess, vacum pumps, CNC etc.
     
  10. rob denney
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    rob denney Senior Member

    Be careful hot gluing to balsa. The air inside expands and blows big bubbles in the veneer. And with infusing balsa. Make sure the balsa is sealed or else you fill it with resin. Near bulletproof, won't rot, but heavy and expensive.

    Salti,
    Airex won't soften unless you use it on the decks, paint it black and sail in the tropics. If below the w/l is compound curvature, you will be using segmented foam, so it doesn't matter which you choose.
    Put your veneers on the table side, not the bag side, at least until you have some experience. Bagging twice to get veneers each side is more work, but less likely to end in tears. I can't see how veneers will save on fairing.
     
  11. Alik
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    Alik Senior Member

    We have recently developed stock designs of 38 and 44', both in pp honeycomb or foam. We are widely using honeycomb in our designs, we have experience infusion in this materials as well. During modifications, we learned that if properly design the structure in honeycomb works well, though structure is heavier. There are some tricks how to join these pp honeycomb plates...

    The 44'
     
  12. saltifinch
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    saltifinch Junior Member

    I'm strongly considering working with PP Honeycomb. All the reviews of people who've actually used it seem to be positive, while negative seems to be from people who just read the data sheets. Yet, it only seems to have 25% less shear strength than Divinycell, and is at least 1/2 the price. For a home builder, its hard to turn that down.

    But of course, I'm always looking for opinions ....
     
  13. Richard Woods
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    Richard Woods Woods Designs

    I think it would be very unwise for a new builder not to try an experiment with infusion before building a boat. And a tool box seems a sensible thing to make to me.

    Don't ever skimp on the costs of the hull shell. You can never change that. But you can start with no electronics, used sails etc and upgrade when you can afford it

    Building the shell is only half the time, or less. Thats why I say fit an outboard, tiller steering, LED AA battery lights

    Where do you berth/haul a 60ft multihull? I know people on the east coast USA who have to go hundreds of miles to slip their boat. Very few yards on the west coast, even fewer in BC. I have been moored in Hopetown Bahamas and a 50ft charter cat was told to move out as he was too big for the mooring field

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  14. saltifinch
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    saltifinch Junior Member

    Good advice. I decided after much research to use a solid fiberglass bottom up to the waterline, removing all concerns about the honeycomb core. I'm still trying to find numbers on appropriate thickness for core and laminate. I hate asking questions on forums, because it's probably been asked several times already, if only I'd dig.

    The cost is the real reason. 4x7 panels of 12mm Nidacore cost $31 each. Marine plywood is around $155 for same thickness. Foam is around the same also. So.... yeah, not really up for discussion at those prices.

    I like your advice about just focusing on getting it into the water. I am outfitting with 2 outboards, and plan to do a lot of practice on just them before I put us sails and rigging.
     

  15. redreuben
    Joined: Jan 2009
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    redreuben redreuben

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