Easy Sarah Catamaran

Discussion in 'Wooden Boat Building and Restoration' started by MCP, Aug 19, 2018.

  1. JamesG123
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    JamesG123 Senior Member

    I have no idea what materials costs are in your neck of the planet. But yeah, its safe to assume that composite foam sheet is going to be significantly more expensive than marine/outdoor plywood.

    Time... it depends. Are you going to be doing the lamination and infusion of the panels yourself or are you going to be able to find a sources of already made sandwich skin? If the former, not only are you going to be building your boat, you are also going to be building the materials to build your boat with!
     
  2. MCP
    Joined: Aug 2018
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    MCP Junior Member

    Thanks

    Let me investigate on the material cost. If it is outside my budget then it is a no go otherwise I might consider it.

    If I do decide to use infused panels, I will most probably manufacture them myself. I'm aware that I will be manufacturing the materials by doing that. But if it gives me peace of mind for the long term, I'm willing to invest the time. Also remember, I'm only considering composite for the hull. The rest will remain ply.
     
  3. sailhand
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    Location: australia

    sailhand Junior Member

    In my experience infusing panels is way faster than hand laminating ply with epoxy and not much more expensive. In australia a nice infusing vinylester can be had for under 10 dollars a litre. Epoxies are more than double that. The end result for all your hard work is where the price difference really shows. Ply boats are sold very cheaply in australia compared to foam, the money spent on a good design will save you a lot of work, frustration and money in the long run. Any boat this size will be at least a 150k boat minimum. An extra few grand for the design and a bit more in materials is the best investment you can make. This money will be returned tenfold, I have seen the cheap alternative a thousand times end in disaster. A good quality marine ply is not cheap, it is worth doing the maths. A nice arrow 12 from schionning would be a 400k boat, if you infuse your own kit it will be a much cheaper and faster build. Let's look at the build process, make frames align and then cover in stringers. Ensure all of these are chamfered at the right bevel and then cover in ply panels that are laminated, I assume inside and out. With the prelaminated infused panels, align in the same jig that you need for a ply build without all the stringers and simply tape together. Now the fairing and fitout, with the ply build you have to fair around all the stingers and cut in all the fitout around the stringers and then paint around all the stringers. With the flat panel it is all a nice smooth surface, much much easier to do, and the finish is infinitely nicer to live in and use. Have a look at the video of schionning arrow series build on his website, nice flat smooth surfaces with nice simple flat smooth panels. Build speed and finish is much much better than old style ply frame and stringer technology. I have built several of both and wouldn't even consider the old method it is definitely more expensive in the long run if you include losses from lower resale value and extra labour involved in initial build then it's no contest.
     
  4. JamesG123
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    JamesG123 Senior Member

    "Sailhand" your posts would be a lot more effective and easier to read if you'd slap the carriage return every once and a while.
     
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  5. MCP
    Joined: Aug 2018
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    Location: South Africa

    MCP Junior Member

    He is a real boat builder: “The lines must be continuous”
     
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  6. Bruce Woods
    Joined: Sep 2007
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    Bruce Woods Senior Member

    Yer, lets.

    Using quality materials and not imported crap. Buying in Bulk.

    15 mm foam, 400g db inside, 800db outside, vinylester resin, hand laminated, works out approximately $100-00 M^2.
    (note: consumables for infusion can add considerably to the cost ) . Add another $20-00 m^2 for taping and beaver vomit temporary frames and moulds. $120-00 total

    9 mm Austral hoop pine marine plywood, hood pine stringers, epoxy resin and quality fastenings , glassed with cloth and epoxy on the outside, epoxy saturated on the inside. $100-00 m^2 ( very little temporary framing required other than the strongback.

    $20 x 300m^2 = $6000 difference for the project.
     
  7. JamesG123
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    JamesG123 Senior Member

    In Oz. He is not in Australia.
     
  8. MCP
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    Location: South Africa

    MCP Junior Member

    I'm in South Africa. We use metric.

    Those figures are definitely doable but I will have to see what it will cost locally or quality import.
     
  9. MCP
    Joined: Aug 2018
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    Location: South Africa

    MCP Junior Member

    @sailhand:

    If you knew me you would know I'm building a Schoinning. But I'm working hard on changing my mindset and lifestyle.

    I'm not building a boat to own a boat, for weekend sails or holidays or just because I like boats (and I do love sailboats). The boat for me is just a vessel that should get me safely, and within a reasonable amount of time, and without too much hassle, from A to B. And off course it should not look and operate like a peace of junk.

    If I can get get 10 to 20 years out of the boat and did everything I wanted to do with it, the result will be priceless. And if I achieved this, selling at a loss would not bother me.
     
  10. rob denney
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    rob denney Senior Member

    In Aus, foam, glass, resin at $82 per sq m from ATL/Allnex plus gst. Ply, hoop pine, epoxy and glass from Boatcraft, $90 plus gst. Both would be less if you bought in bulk. Both will ship to Sth Africa.

    Infusion costs depend how you infuse. We don't use anywhere near $20 per sq m INTELLIGENT INFUSION – Harryproa http://harryproa.com/?p=1845 Doubt if it costs $5 per sq m, could be as little as $1 for a bit more effort. The cheap mould is about the same cost as the strongback, minus all the fiddly aligning and setting up.

    Ply and hand applied resin waste will be considerably more than foam and infused resin waste.

    The difference in the cost of the materials is not the big deal. The saving in weight and labour is. The ply weighs 5 kgs per sqm, resin 0.6 kg, glass 0.2 and stringer 0.2 = 6 kgs per sq m. The foam is 1.2 kgs per sq m, glass 1 kg, resin 1 kg = 3.2 kgs. 300 sq m is 840 kgs difference. On a 4,800 kg boat like the Sarah, that is significant.

    The labour difference is equally large. The hours will be a half to two thirds, the energy expended about one tenth. Half the ply boat labour will require a dust mask, gloves and overalls. The other half will be sweat inducing. The infused boat builder wears gloves for ~10 minutes each infusion. There is almost no sweaty labour required.

    Building in ply was a great idea 50 years ago. It makes no sense at all now. Infusing panels and taping them together is an improvement, but not much of one as there is still a lot of unpleasant labour. A 12m/40' double chine hull will have 6 joins to tape, 4 of them on your hands and knees, 2 of them overhead. Crawl 100m (2 x 12 x 4) to get a feeling for what is involved. Then another 6 on the other side, all of which need to be faired.

    As R Watson pointed out, you can build an Intelligently Infused 60' harryproa at less weight and not much more cost than a 40' ply cat.

    Boat length is important if you are considering seaworthiness. A small boat is more affected by the waves, will be slower and is more likely to fall over. More importantly, the big boat feels safer.
     
  11. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    MCP,
    I am so sorry for your loss.
    I'm also sorry you're not getting the answer to your question, it happens often here.
    I'm not familiar with the Sarah.
    Perhaps there is a Sarah forum out there that would be more helpful.
    Best of luck.
     
  12. JamesG123
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    JamesG123 Senior Member

    That would make sense and be the best choice if the OP were going to go into serial boat production. But he is not. You ignored the not inconsequential cost of the vaccum pumps, the lines, valves, etc which would be one time use items and then he would have to dispose of them. You hand waive away the cost, time, and effort of creating the moulds, at least 4 of them that would be built and then discarded when the project is complete, where as building in ply only needs a minimal strongback to hold the actual boat's bulkheads, ribs, and stringers in position for putting the skin panels on and then glassing them directly.

    You complain about the effort required to fair the ply of the hull, well, you do the same for the moulds, and then you have to do the same thing again with the finished infused core because they rarely come out perfect, and it almost assuredly would not for someone doing so the first and only time. Which is another thing, the learning curve of doing infusion correctly is pretty steep. Its easy to mess up until you learn how to do it, and I am pretty sure the OP is more interested in building a boat and going sailing with his kid and not learning a new trade.

    Foam core composite is higher performance, allows more complex shapes, and is better suited to mass production, but for a one off build, you still can't beat glass on ply for minimal investment of cost and time to produce a boat.
     
  13. rwatson
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    rwatson Senior Member

    James, you ought to actually read the method before you make the criticism.

    The moulds are amazingly efficient, and their design and reusability is very developed. You only build two moulds as an example, and very little fairing is involved.

    Everything Rob says about the plywood epoxy weight and cost is spot on, and the amount of work fairing up glass on ply is huge. I have been there on smaller projects, and it makes the reportedly "simple" methodology a major headache.

    Have a read of Sam Devlin, a big proponent of stitched ply under glass. He at least has a realistic assessment of finishing and fairing plywood. Being able to create an instantly fair and finished outside hull is a huge benefit.
     
  14. JamesG123
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    JamesG123 Senior Member

    I have done both and I am agnostic of either method. Rob was presenting a very biased case and I called him on it.

    You aren't creating an "instantly fair and finished hull", that is the biggest myth of infusion. You can do the exact same thing with hand layup. Its all in the moulds. There is a ton of up front work that has to be done with infusion and does not contribute anything to the finished structure. Recall that the OP does not want to build a proa. He already has a design in mind. So about half your supposed benefit is thrown out the window.
     

  15. rob denney
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    rob denney Senior Member

    Blue Bell,
    No one answered because it is not possible to do so. The Sarah, built properly, is as safe and seaworthy as any other similar boat. Peter Snell knows what he is doing and has built and sailed a lot of boats. To make it safer, you could make it longer and/or wider, use a rig that could be completely depowered on any point of sail in any wind strength, reduce the crew stress by removing the need for foredeck work and flogging sails, remove the fixed keels and rudders so there was less for the boat to trip over when sliding down a big wave and so it could be beached above the wave impact zone and make tacking and gybing in big seas less arduous.

    You need to distinguish between infusion and Intelligent Infusion.

    The OP asked about the seaworthiness of a Sarah. The thread then drifted to othe boats and build methods, so I responded by pointing out that a C60 proa would be considerably safer as well as being the same weight and faster to build and sail than the Sarah.
    My comments on infusion were based on my reference to INTELLIGENT INFUSION – Harryproa http://harryproa.com/?p=1845 which does indeed produce a fair hull, ready to paint with no polishing or mould fairing required.

    There is also no trimming, grinding or sanding of the finished laminate required and no secondary laminating. You will not get any of this with a hand layup or a ply boat.

    If butt joining mdf sheets together to make the table or mould, cutting materials, laying them in the mould, and bagging them to prepare for infusion conbstitutes 'a ton of work, then there are 'several tons of work' required before you apply the ply to a ply boat. Set up strongback, cut, install align and fair bulkheads and temporary frames, scarph and trim ply, install and plane keel, stem and stringers. Plus another couple of tons glassing and fairing it, ready for paint.

    And several more 'tons' on the interior, where the infused boat has no bare edges to cap, no ply or stringers requiring 3 coats of epoxy (plus sanding), no fitting and edging doors and hatches (they are included in the infusion with the space they occupy so fit exactly), no window holes to cut, rebate and edge seal and no need to fit solids under fittings or mess with epoxy in every screw and bolt hole.

    A vacuum pump can be bought for less than the cost of the hand tools required to build a ply boat, and will have value at the end.
    With Intelligent Infusion, there are no " valves" and the "lines" are cheap hardware products. The "etc" is the tacky tape ($1 per metre, not required if you want to spend a bit more time with brown tape), the bag (few cents per sq m and often reusable) and a length of cheap 6mm polyprop 3 strand rope.

    There is far less waste thrown away than there is with a hand laid boat, far less dust and fumes inhaled, far fewer heavy sheets to manhandle and no resin near your skin.

    All the moulds and the table for the bulkheads, etc for the 18m C60 can be built from 2 dozen sheets of mdf or similar. There is no need for a strongback, cradles or all the framing required to set up the bridge deck on the cat.

    Infusion requires far less skill than ply (the moulds are self aligning and easily levelled) and can be learnt in small steps, set out in the plans. It is very difficult to mess up, and rarely terminal if you do. Once you can infuse, you can also build your carbon mast, boom and rudder shafts, saving considerable weight and money over bought aluminium spars and stainless shafts.

    "for a one off build, you still can't beat glass on ply for minimal investment of cost and time to produce a boat" is incorrect for anything biger than a dinghy. The materials cost more, the boat weighs more (see my previous post) so needs a bigger, stronger rig and more powerful engine, the build takes longer and the resulting boat requires far more maintenance.
     
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