Catamaran build/maintenance question...

Discussion in 'Multihulls' started by NZjoe, Apr 18, 2010.

  1. NZjoe
    Joined: Apr 2010
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    NZjoe Junior Member

    GREETINGS to all...

    Hi - from a New Member. I have a few questions that i haven't seen asked in the forums - or haven't surfed deep enough more likely!

    Q1/ Within the boat-building/shipwright industry, which boat building material is considered the easiest to work with in the event of damage repair, transom extension / modifications etc?

    Q2/ Which would take the hardest knocks, aside from metal?

    Q3/ Which is the most durable and easiest to maintain?

    I'm looking to buy a semi-budget secondhand cruising cat around 32' - 36' to live a board and cruise indefinitely, mostly tropical regions of Australia with short hops offshore. With virtually no fiberglass or wood working experience (yet) Im trying to narrow down my options to make the process a little simpler.

    There are many good homebuilt cats in Australia built in plywood, and more recently, duflex panels with foam or balsa cores, plus older semi-production/production Fiberglass cats. Any help, advice and feedback would be very much appreciated, cheers.
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    Greetings NZjoe

    Q1…well, this is highly subjective. Since if you ask a GRP shipyard, they will say GRP, if you ask an Ally shipyard they’ll say ally and so on. Therefore, you need to remove the subjectivity out of their replies. However, that is nay impossible. Since whether it is the yard or the person actually doing the job, is all subjective. This is not to say ignore such advice, but, each material can be easy or hard, it depends upon the skill of the person doing the job. How qualified are they, for doing repair work, and look for examples of work done too, and/or ask around from ex-customers...

    I design with all 3 materials. I don’t choose, unless the client has a preference. The ‘solution’ is driven by the SOR of the client.

    Q2…again, not so easy to answer. A knock, can range from a slight bang against the jetty, to a knock against a rock whilst going a full chat. The internal structural arrangements will dictate how well the structure and hence the material will survive.

    Having a GRP boat with a frame spacing of say 300mm, will behave differently from one with a spacing of 1000mm (how many strigners?), where both vessels hit the same immovable obstacle. Additionally, if the frame was just 50mm in depth, or whether 300mm in depth seriously affects the modulus, and hence the overall stiffness. Coupled with this, what load paths, if any, are available, and how is the load shed to surrounding structural members.

    Q3…again, you can ask 10 people and get 10 different answers. For the same above reasons.

    Ease of maintenance is also governed by the design, not just material. How easy is it to clean under the engine beds i.e. access, can you remove all the excess oily bilge easily, are the fixings so close together you can't remove them, can you wash eqpt down easily, or are bolt heads a source of continual corrosion, are there too many sources of dissimilar metals present causing an over reliance on continual maintenance which should not be necessary, do the bolts/fastenings have proper structural fixings or will they pull through under high loads or allow ingress of water into the core etc etc

    I think the question should be which is best for you. That shall be dictated by what yards are local to you, for repair. No point having a GRP boat if the nearest yard for repair work is some 500km away, where as a steel yard is your neighbour. Then if two yards appear to be close by, which has the better quality and better reputation? Finally, on your proposed “general” journeys sailing/motor-boating, what types of repairs yards are available, should damage occur? Again, not point going for GRP is all the repair yards only do steel or ally.

    This is a perennial question with no simple quick one line answer. Since it is subject but more importantly subjective to you and your requests when/should a repair be required. What is availably locally to you is far more important than what is my preference or available locally to me.

    So, do some research….see how many yards are local to you and on the routes you intend to sail. Then see what type of repair yards they are their reputation and their rates! The answer shall then pop out.
     
  3. NZjoe
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    NZjoe Junior Member

    Thanks a lot Ad Hoc, some good advice there and food for thought.

    Q1/ I did intend taking into account the 'bias factor' and form my own conclusions subject to my personal circumstances and dependent on others opinions and their reasoning. I guess i was hoping there was a general-consensus througout the industry itself. But your right, subjectivity would make that difficult.

    Q2/ The 'hard knock' question was probably not necessary as i'm more interested in the general ease of repair by my self (nicks, scratches, dents, cracks and painting) or professionals. Having said that, i did view a yacht made of duflex panels which had been totaled on the rocks in a storm here. The broken panels looked weak and felt brittle to the touch. In its defense nothing would have stood up to the pounding it received but still, what i saw and touched did leave an impression perceived or otherwise. There are many DIY Duflex cats here which i like the look of, but not if the drawbacks are too great. Reality - as opposed to perceptions, is what i'm after to make the best choice for me.

    Q3/ Ease of maintenance - Once again, probably not necessary. I should be asking about peoples experiences and the Pros & cons of their favoured material to help form my own conclusions...
     
  4. catsketcher
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    catsketcher Senior Member

    Good build is good build

    Gday Joe

    I have a 38 foot cat that has a foam cabin top, Duflex in the aft deck, Nomex honeycomb in parts, plywood decks, strip cedar hulls. One of my little cats is ply/kiri, the other ply, dulfex /foam.

    My own personal belief is that there is a good deal of marketing in materials. A good builder can make a good boat out of any of the above materials but no material is immune from problems.

    Take foam for example. Some people love to bash balsa and say it will rot and you should use foam. Foam is fine but it does not have the shear strength of balsa and even balsa can make some very good boats. Some of them are even decades old. There are many foam builds I would be wary of as foam needs good adhesion to the core and some builders are not as careful as they should be. Some foam cats are way too light and are well into fatigue problems.

    Look over any prospective boat and check that it is carefully built. Any modern cat can be well built in any of the normal materials - it is about build rather than material.

    cheers

    Phil
     
  5. catsketcher
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    catsketcher Senior Member

    Hard knocks

    I just reread your second post

    As to hard knocks - it again is up for argument

    All light multihulls are stiff bit light so their material in its virgin or half demolished state will look flimsy. A piece of ply unsupported will be flexy but with a cupboard behind it and coved and taped will be solid. Foam pieces look fine but if you destroy a piece you can tear off the laminate near the damage.

    The Coastal Passage did a bit of a nasty piece on Duflex. I don't think the builder knew about materials. He was looking for a watertight material straight out of the box and wrote a diatribe about it when he found water could enter the laminate. Any builder would have told the guy that you get the structure done and then you lay on huge amounts of filler and epoxy sealer so that the Duflex is watertight. I would not like to buy shiny sealed Duflex as I would have to sand it to get the filler to stick so ATL sell it with voids in it. Some builders (only first timers I recall) have problems with getting the filler to cover the voids - I don't know why and then get cross and start flinging insults. The problem in the above instance was not with the material but with the building.

    Peter Snell likes ply. He is a very experienced builder and designer and likes ply because a designer can surely know the engineering properties of the ply as you do with steel and ally. Foam sandwich is very subject to resin choice, operator error, temp, humidity, vac pressure etc. Ply is made to a standard such as BS 1088 so it is far more useful to use as an engineering material.

    I have put holes in ply, cedar, foam and all were easy enough to repair. Again make sure the boat is well built before you worry about the material. If someone tells you bad things about a material ask how many boats they have built with other materials first before you believe them.
     
  6. NZjoe
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    NZjoe Junior Member

    Thanks Catsketcher...

    Quote - "Again make sure the boat is well built before you worry about the material." - I absolutely agree with you, which also poses a slight dilemma.

    In '08 I was shown a home built 32' ply cat advertised as launched in '06. The boat looked immaculate which made the heart flutter at first even though it was priced accordingly. Faired inside and out with smooth rounded edges everywhere resembling a GRP production job (to me). I couldn't fault the workmanship but I always wonder what sins are covered. Indication was that the owner seemed a perfectionist which is about all you have to go by aside from questions and surface inspections.

    After some questioning he revealed the boat was a do up of a '95 version that was apparently used as a floating batch minus rig by the original builder (shows how keen he wasn't) When I heard that i was pissed off i travelled 600 kms to view the boat (through a well known brokerage) It was clear to me why so much effort was made to cover/seal and fare the whole boat. For all i knew the original builder probably did a shocking job minus the vital maintenance - who knows? Pics of boat below for your interest.

    SOLUTION?? Build My Own! Which i can't, due to the fact i'm too SANE and don't have the skills. Do you know of any good honest craftsman with a giant shed on his property looking for full time work?? I could be the apprentice helper. Anyway, my current favoured material has become ply wood for all the good reasons - I think...
     

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  7. downunder
    Joined: May 2009
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    downunder Junior Member

    NZjoe

    Here is a link to somebody building an Oram 39C employing an experienced
    composite craftsman in a rented shed in SE Old.

    http://boats-n-stuff.com.au/forum/index.php/topic,2.msg1999.html#msg1999

    Suggest you make contact and visit the shed sometime. Owner is doing exactly as you suggest. I would not necessarily rule out foam or balsa composite to early if you can find a builder.

    The hull is Duflex balsa and hardtop foam.
     
  8. aussiebushman
    Joined: Oct 2009
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    aussiebushman Innovator

    I agree that the material selection is very much a reflection of the mindset and skills of the builder. I have worked with many different materials and for all round value, strength and ease of build, my vote would unquestionably be for epoxy/glass sheathed epoxy strip timber. Although WRC is the traditional choice, Paulownia now offers many advantages, in lower density (weight) as well as rot resistance and not the least, the price.

    While ply might appeal because it is relatively cheap and one sheet covers a large area, there are too many many problems even with so-called marine-grade ply coated with multiple layers of epoxy and glassed, because the potential for rot is truly worrying. Any hole, even when bogged and redrilled is a potential water ingress site and while repair is pretty simple, it seems smart to restrict the use of Ply to a minimum.

    In terms of maintenance and resistance to knocks, I would rate strip/epoxy better than steel. You will agree if you have ever seen a steel vessel on the hard having plates epoxy-bogged or replaced due to the metal being eaten away from various causes, poor maintenance being the most common. With strip/epoxy, minor dings present little problem - just grind out the damage, fill, re-glass, fair and paint. Even for a worst case scenario, the damage is fairly easy to repair.

    I can't comment on fibreglass with polyester or vinylester building because I do not have the experience. Anyway, while others will argue differently, for me, no contest.
     
  9. fng
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    fng Junior Member

    Being a boat builder I would suggest that you do a workshop ( eg, I think that one of the shionnings do them over there ). All things built marine now days has fibreglass. You need to be un-afraid of fiberglass and resin. Then it will all come down to price. Any composite structure can be modified at a later date, and all mods start with an idea, and than a grinder.
    When I think about how we cut a tucked the AC boats, the worst part was the cutting and grinding.
    Even if you decide to go with ply you will still be using epoxy, and you should stil be glassing the out side of the boat.
     
  10. fng
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    fng Junior Member

    After re reading everthing you probibly need to narrow down the design wish list which will help with usable materails. What things cost in Auusie compared to NZ or anywhere else in the world will allways differ.
    To narrow down your desin will give you a displacement which then in turn will maybe eliminate some construction methods. You could always fly to NZ for a week and I could give you a crash course. Or you could fly me up there.
    I feel that you need to narrow down the picture to get a real answer. And with what ever choice you go with, hands on experince is worth more than any fourm.
     
  11. rob denney
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    rob denney Senior Member

    Phil,
    I am pretty sure that ATL don't leave deliberate voids in their panels. They apply the prewet glass to the balsa, then peel ply it and consolidate it in a heated press. This is not far off the way composite panels are prepared for aerospace and makes a very light panel with no voids. Remove the peel ply and you have a surface ready for epoxy. With 600 gsm glass (the minimum they use), this should be watertight and air tight. It certainly would be on any other core.

    Start a thread about the easiest ways to build boats and one of the first answers will be about how little filler you need on the kit boats built from Duflex. Try telling the builders or designers that "huge amounts of filler are required", just to seal the surface and you will get shot down in flames.

    There are many parts of a boat where filling the surface is a waste of time, money and weight (most of the interior) and painting areas that are never seen is a waste as well. The Coastal Passage guy is over the top with some of his criticism, but look at his samples and you will end up doing a lot more work on your balsa panel boat than you thought you would have to when you first read the brochure.

    rob
     
  12. catsketcher
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    catsketcher Senior Member

    Agree

    Hello Rob

    You are right that I used the wrong word in voids - what I meant is that there are little spaces between the 0 and 90 degree fibres on a very small scale. The resin has been sucked out leaving a good bonding surface but maybe a way for water to get in to the core. BUT everyone would fill the surface anyway when fairing.

    A friend of mine built a Duflex 13.2 metre Schionning - great boat. He put a bit of Duflex in the water with core exposed at the start of the build. After 5 years he pulled it out. The water had run all of 1 or 2mm into the core sides. It went dry every tide and he has a waterfront so he could make sure it stayed there for the whole time. He also drilled a hole in Duflex and left a test sample in a dye with a hole drilled in it. After a couple of months the same result - about 2 mm maximum into the core. Not too bad really.

    I like Duflex but would probably do something more akin to the Kelsall thing (foam on a long table) to make hull sides up myself. On a cruising boat it is very nice to have all the interior cut out which is one of the reasons you go to ATL. Racers have far less interior.

    cheers

    Phil
     
  13. NZjoe
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    NZjoe Junior Member

    Thanks All...

    Thanks for everyones contribution, much appreciated. Do i know what I'm doing yet? Well not really. I plan to be living a board and cruise for a very long time so, without the experience, it's important i make the best choices for me to save heart ache - Hindsight is a wonderful thing!
     
  14. NZjoe
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    NZjoe Junior Member

    Design Wish...


    I agree with 'hands on experience and the more the better. I need to do some cosmetic repairs/painting and maintenance to my trimaran to help sell it first - ideally) No experience or have even had a boat hauled before... Wanna spend time in the Whitsundays???

    As for my design choice...if i were ever to have a boat built i'd possibly favour Peter Snells 'Jessica 9.9' which superseded his 'Easy32' design, (photos above) with just a few innovations of my own. I like ply/glass probably only because of my perceptions. Otherwise i'll continue defining my short list of all sorts of second hand boats to view, and see what happens to my thinking...
     

  15. rob denney
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    rob denney Senior Member

    Still doesn't really explain it. The resin is not sucked out, it is pushed in and the excess flows out. The peel ply affects maybe 0,1 mm of the surface, probably less. The 600mm glass and resin is 0.6mm thick, plus whatever soaks into the face of the balsa, so how do the holes form? Would they still be there if they used plastic instead of peel ply? Be a hell of a lot easier to abrade a shiny surface for painting and filling where necessary, rather than heaps of bog and a paint system for all the areas that don't.

    Salt water tests are useless as as salt preserves timber. Immersion tests are not much better. Try placing the balsa in a dark, fresh water damp environment with large variations in temperature like a boat bilge and see what happens. Or a wet deck with a badly seated fitting during a rainy summer. For best/worst results, expose the end grain rather than the cross grain. Balsa is designed to rot, and it does it very successfuly. It is scary in a boat unless the boat is built and maintained very carefully.

    Agree cnc cut panels are great timesavers for the internals of complicated boat shapes, albeit expensive. However, you can do them just as well with foam panels, ply, or strip planked boats. I suspect the foam panels will be cheaper than balsa if you don't have to apply all that filler and paint to the internal surfaces.

    rob
     
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