Multihull Structure Thoughts

Discussion in 'Multihulls' started by oldmulti, May 27, 2019.

  1. oldmulti
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    oldmulti Senior Member

    The guy designed it himself with some assistance from friends who were building a 60 foot steel cat on a farm in Warneet. The 60 footer was never finished. I will have to dig deep to find the original info as it was in a local newspaper. I have personally seen the cat. He rolled the plates himself etc as in this size of boat most curves are gentle and almost a single dimension for the size of plate that you can move with limited equipment. He had some sort of "crane" welded to the back of an old truck thing to move things around. I will try and find more.
     
  2. oldmulti
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    oldmulti Senior Member

    Banjansailor, your request is my demand. Be prepared to be bloody amazed. First look at New Page — Llinase https://llinase.com/the-build

    The look at 3 youtube video’s about LIinase that have old film clips of the actual construction of the cat, the equipment Les used to build the boat and its initial launch. Also there is a great Youtube with the technique Les used to "Walk" the cat onto dry land. Go to Youtube and search for LIinase catamaran.

    And if you want find a copy of his e book “Llinase how the worlds largest how the worlds largest solo designed and built catamaran took shape”

    His name Les Thompson of Inverloch Victoria. The 100 steel cat was started in 1972, launched 1980 fitted out for 2 years after that. Total of over 12,000 hours. Built mainly by himself with home made equipment.
     

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    Last edited: Aug 1, 2020
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  3. bajansailor
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    bajansailor Marine Surveyor

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  4. oldmulti
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    oldmulti Senior Member

    John. Thank you for looking at this thread. You are very welcome. Is it OK if people ask a few questions about the Ocean Swift 44? EG How long did it take to build? Were there any improvements you would like to have made to the design?
     
  5. Johncat44
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    Johncat44 New Member

    Thanks for the interest in Ocean Swift. Just to clarify a few points. It was 9 days from Cape Verde to Barbados. The mast is 16m (54ft), carbon fibre, 420mm x 2oomm. Mainsail is 60 square metres. We actually shortened the mast slightly and lengthened the boom on the build.
     
  6. Johncat44
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    Johncat44 New Member

    Is this Martin, if so thanks for getting in touch with me. The build was done over about 7 years I think. I use to start the building about May and then pack it all in about September. I had to then think about goint to work as well which at the time was Antarctica. I live in the wettest part of England, the English lake district which made it all more challenging trying to work in a dry atmosphere. I think I'd make the sink in the heads 2" lower as an improvement. She's a nice looking boat and part of the reason for that is I haven't been greedy with bridge deck accommadation, so from beam to beam its 16ft, leaving lots of free hull. She's sitting headroom in the bridge cabin, giving lots of free board underneath and also keeping the foot of the mainsail lower. Standing headroom in the hulls. I haven't tried to replicate a house in weight and room heights. Ocean Swift isn't everyones cup of tea but she is a fun boat to sail.
     
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  7. oldmulti
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    oldmulti Senior Member

    An oops! Further detail on the 100 ft steel cat shows its only 79 foot long by 34 foot beam with a displacement of 70 tons (157,000 lbs). Les worked a minimum of 4 hours per day 365 days per year for 10 years. He had 2 miles of welding to crate the steel cat and had to paint 7500 square foot of surface area. The shell was 3 mm steel. A massive job. Les also wrote another book "Fire in my belly" which still may be available from his web address llinasellinase@gmail.com Still a brilliant job done by a very determined man.
     
    Last edited: Jul 31, 2020
  8. oldmulti
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    oldmulti Senior Member

    I have written about Crowther’s Schockwave 37 foot tube racing cats before. They started with a lightweight 37 foot cat for home builders that were built with 330 gsm cloth either side of 12 mm Airex with polyester. The 330 gsm cloth was doubled below the waterline. The 3 cross beams were 208 x 150 mm aluminium tubes. Next came the Super Shockwave again a tube racing cat of 37 x 25 foot weighing between 5000 to 6000 lbs depending on who built the design and what hull layup and crossbeam options were chosen. The 50 foot fractional rig wing mast rig carries 767 square foot in the main and foretriangle. The hull layups on the lightest boats comprised of 165 gsm Kevlar style 285 ether side of 20 mm PVC foam in epoxy. The Kevlar is doubled below the waterline. The super schockwaves had aluminium tube crossarms fore and aft and some had a fabricated aluminium box beam for the mast beam.

    But as per usual someone wanted more accommodation but maintain the performance of a Schockwave cat. Enter the Super Schockwave BD (bridgedeck) cat. The BD design uses the same 13 to 1 length to beam hull shape slightly lengthen to 40 foot but it had a limited bridgedeck cabin that had 4.5 headroom over the majority of it. The Super Schockwave BD design was meant to be 40 x 26.25 foot weighing 7800 lbs and carrying a 55 foot carbon fibre wing mast with 645 square foot main 310 square foot jib and a 1740 square foot spinnaker. Now the fun begins. The first Super Schockwave DB was extended to 42 foot and when weighed for racing came in at 9800 lbs minus crew and liquids. The hull layups were still slightly heavier Kevlar in epoxy and 20 mm PVC foam. The main and rea crossbeams were composite foam Kevlar webs with top and bottom carbon fibre flanges. The accommodation is a full width main cabin with a double berth either side of the cockpit. Galley and loo are in the hulls.

    Several other Super Schockwaves DB have been built including a high performance version now called Tik Toc. TiK Toc, according to its builder, shell weighed 5000 lbs minus rig engine etc. How was it lighter? There was less boat eg the double berth cabins beside the cockpit were eliminated and the bridge deck was 6 foot shorter than the “standard” BD design.

    As soon as TikTok was built, it took off on a world cruise. Shortly after the original owner departed, the builder Geoff Cruze received a call asking, “How the heck can I slow the boat down?” TikTok was fast and a real handful, as it was clocking in the high 20’s with ease. Geoff responded, “Reef in the main and put up a small storm jib,” to which the owner replied, “I’ve already done that!” 10 years into the world cruise Tik Toc lost its rig and was shipped back to Australia for a rebuild. The bows were extended 3.25 foot and made reverse to add around 320 litres of frontal buoyancy. This is due to the tendency of the design to sail slightly nose-down. The sterns were also extended 3 foot.

    Now how do these boats perform? Very well indeed. Over 20 knots is normal with peaks of 30 knots. Averages of 15 knot plus over 300 miles has happened on several occasions. There light to moderate air performance was very good. The Super Schockwave DB is an excellent design. The jpegs show the original DB, a sistership and then Tik Tok being modified. The final jpeg is of the 37 foot super schockwave tube cat.
     

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  9. oldmulti
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    oldmulti Senior Member

    BERND KOHLER IS VERY PASSIONATE MULTIHULL DESIGNER ABOUT HIS CHOSEN BUILD materials and defends their properties. Here he explains why he sees ply/epoxy composite as the best choice for the amateur builder. (This is slightly edited) “In the 1950s a lot of boats were made from plywood but when fiberglass arrived plywood boats disappeared in a lot of countries. Plywood boats developed a bad name simply because many were built the wrong way. The plywood got water logged, the veneers separated and that was the end of the boat. With the arrival of epoxy there is no reason any more not to build durable and low maintenance boats from plywood/glass/epoxy composites. Boats built in this way are long lasting, resilient and not prone to material fatigue. But to get rid of a bad reputation is extremely difficult!

    The only country I know where many plywood/epoxy boats are still built is here in France. The French are known to be pragmatic. This is one of their strong points when it comes to designing and building something. At the 2009 Paris boat show there was many plywood wood epoxy boats being built professionally at various wharves. Several production monohulls EG RM Series have plywood hull structures. And that is not counting companies who sell kits for plywood epoxy boats. So there must be something good about it! Let’s look at the merits of plywood step by step.

    1. Good marine plywood is water resistant due to its structural qualities.
    2. Because of its strength to weight ratio, it’s easy to calculate exactly towards light construction.
    3. Easy to cut with normal wood working tools.
    4. Smooth surfaces so not a lot to be done to end up with a very professional looking surface.
    5. Very economical construction when compared to any other sandwich composite.
    6. Besides the strongback, there is no waste of material in a plywood boat. No molds are necessary which, for a one-off boat, can be expensive and time consuming. The building of a sandwich construction 12m catamaran can take a year to make 1 hull with all the sanding and filling you have to do. Our Pelican no 2, a 10.5m catamaran design built in the plywood/glass/epoxy system, was in the water after one year! The builder was an amateur and it was his first boat.
    7. Not necessary to learn new techniques like vacuum bagging or injection molding which is necessary for many sandwich constructions.
    8. The only good thing about polyester is it is cheap. Polyester is already a finished material. To cure it you add the catalyst. Now the material starts curing but never stops! Polyesters exhibit poor performance in the areas of adhesion and elongation, rendering the finished part prone to micro cracking and secondary bond failures. Polyester hulls are still suffering from osmotic blistering when untreated by an epoxy barrier coating against water.
    9. Wood is a non fatigue material. Look at a tree in a storm. It is known that polyester and sandwich boats are ‘weakening’ after some use. This will never happen to a plywood sandwich boat. It is known that wood/glass/epoxy Tornado class catamarans stay competitive over years, but that Tornados built from any other materials remain competitive for only about two years. Material fatigue is the reason. They simply become weak.
    10. . Plywood boats can actually be built in any shape. Look at the A class. Many of these boats are built in the ‘tortured’ plywood system with a U-shape cross section. In my opinion, for amateur boat builders there is no better choice than (ply)wood/glass fibre/epoxy.”

    The jpegs show a few of his diverse range of designs. And for Russell Brown, please have a look at this page NEWcats https://ikarus342000.com/NEWcats.html
     

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  10. oldmulti
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    oldmulti Senior Member

    John Taylor, Old Multi is not Martin. Martin (Banjansailor) is the kind person who had a Linkedin account to contact you.

    Folks, I thought there would be some questions for John Taylor builder of Ocean Swift, but as you appear to be shy, I will ask on your behalf. John you mentioned a book about Ocean Swift build etc. Are any copies available? This thread has a few hundred people who look at this thread regularly of which quite a few have expressed interest in your design and build.

    Did you do your own engineering on the cat eg cross beams etc? Are the cross beams ply and timber with foam inserts? Your boat is impressively light. Did you have plywood bulkheads etc? Is the Western red cedar core on the hulls and decks 12 mm or greater? Is there a study plan that could be uploaded of the EG sail plan for others to look at? Uploads can be done by creating a jpeg and using the upload button. Thanks again for responding as we are all trying to gain an understanding of what makes a good fast design.

    PS if there are any errors in the original write up of Ocean Swift, Please correct them. We like real knowledge.
     
    Last edited: Aug 3, 2020
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  11. jamez
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    jamez Senior Member


    Ocean Swift is a lovely boat. However I would also be interested in pics/details of the 35' version it was based on.
     
  12. rob denney
    Joined: Feb 2005
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    rob denney Senior Member

    My comments after Bernds
    Let’s look at the merits of plywood step by step.
    1. Good marine plywood is water resistant due to its structural qualities.

    It's not. Without epoxy or similar it will become waterlogged then rot when exposed to water. The lighter the timber, the quicker this occurs.
    2. Because of its strength to weight ratio, it’s easy to calculate exactly towards light construction.
    Plywood strength to weight ratio is poor compared to infused foam/fibreglass. There is a lot more variety in plywood weight and properties than there is in foam or 'glass.
    3. Easy to cut with normal wood working tools.
    Obviously. But not as easy as cutting glass with scissors and foam with a utility knife. And carrying foam around is a lot easier than plywood.
    4. Smooth surfaces so not a lot to be done to end up with a very professional looking surface.
    True, but after glassing, it still needs to be faired if there are any overlaps in the glass. An infused foam/glass surface comes off the table, the peel ply is removed and it is ready to paint.
    5. Very economical construction when compared to any other sandwich composite.
    Not in Australia. From a couple of years ago Cost to build - Page 2 - Cruisers & Sailing Forums https://www.cruisersforum.com/forums/f48/cost-to-build-200141-2.html: e
    For a 30-35' cat, 15mm foam (1.2 kgs/sq m) with 400 double bias inside and 600 outside will be more than enough. Infused, this will weigh about 3.2 kgs per sq m, of which 1kg will be epoxy.
    9mm Gaboon ply (4.7 kgs per sq m) with 3 coats of epoxy each side (0.8 kgs, if applied diligently), plus 200gsm of glass weighs 5.7 kgs, plus the stringers, say 6 kgs all up.

    The ply is almost double the weight of the foam/glass, plus the edge treatment, wastage, and gluing it requires. The weight saved results in a smaller rig and motor, saving more money.
    In Aus, the foam costs about $50/sqm, the glass $12 and the epoxy $11. Total $63 per sq m.
    The ply costs $77 per sqm, the glass $6 and the epoxy $9. Total $82 per sqm.
    Multiply by 0.7 to get $US and divide by 10.75 to get sq feet

    I am now importing the foam and glass from China to build a 24m/80' cargo proa. The quality is the same as locally bought, the cost is between a half and a third.
    6. Besides the strongback, there is no waste of material in a plywood boat.
    The pile of offcuts from a ply build is significant. With foam, offcuts are hot melt glued together and used.
    6.No molds are necessary which, for a one-off boat, can be expensive and time consuming. The building of a sandwich construction 12m catamaran can take a year to make 1 hull with all the sanding and filling you have to do. Our Pelican no 2, a 10.5m catamaran design built in the plywood/glass/epoxy system, was in the water after one year! The builder was an amateur and it was his first boat.
    Unless the same builder builds an infused boat, this is meaningless. There is little or no "sanding and filling" with modern foam build methods
    7. Not necessary to learn new techniques like vacuum bagging or injection molding which is necessary for many sandwich constructions.
    Vacuum infusion is far easier to learn than scarffing and shaping ply, setting up frames so they are fair, installing stringers and wet laminating.
    8. The only good thing about polyester is it is cheap. Polyester is already a finished material. To cure it you add the catalyst. Now the material starts curing but never stops! Polyesters exhibit poor performance in the areas of adhesion and elongation, rendering the finished part prone to micro cracking and secondary bond failures. Polyester hulls are still suffering from osmotic blistering when untreated by an epoxy barrier coating against water.
    From the same thread as the costs: The oldest foam glass multi is one of the early Kelsall ones (Trifle, I think), built with polyester resin in 1966 (54 years old) and still going strong. Great Britain 2 (mono) was built in 1972, also polyester/foam glass. Raced seven times round the world, 50 plus Atlantic crossings and a very busy sailing career in between. Resins, cores and techniques have improved enormously since then. Ply boats are still built the same way they were in the 60's, which is when I built my first one, a 5m/14' catamaran. By many accounts, plywood quality has significantly deteriorated since then.
    9. Wood is a non fatigue material. Look at a tree in a storm. It is known that polyester and sandwich boats are ‘weakening’ after some use. This will never happen to a plywood sandwich boat. It is known that wood/glass/epoxy Tornado class catamarans stay competitive over years, but that Tornados built from any other materials remain competitive for only about two years. Material fatigue is the reason. They simply become weak.
    Marstrom cored Tornados superseded timber ones over 20 years ago and are still going strong. Trees are not glued together with phenolic glue, which is nowhere near as fatigue resistant as timber.
    10. Plywood boats can actually be built in any shape. Look at the A class. Many of these boats are built in the ‘tortured’ plywood system with a U-shape cross section.
    "Any shape" as long as it is single curvature or slightly compound, which is actually quite limiting for boat design.
    10. In my opinion, for amateur boat builders there is no better choice than (ply)wood/glass fibre/epoxy.”
    To build the ply boat you will/should be in full overalls, gloves and mask for much of the build to protect yourself from resin, dust and fumes. Much of the work requires noisy, dangerous power tools and a fair bit of it will be done in uncomfortable positions (bent over, overhead or on your hands and knees).
    By comparison, Intelligent Infusion has 1 or 2 resin mixes per infusion. Gravity applies this to the job, with optimal resin/fibre ratios, no voids, gaps or filling and no contact with the sticky stuff. We do not need or use gloves or other protective gear while infusing. The completed components are then glued in place. There is almost no cutting, grinding or glassing of infused components, no fitting and alignment of the bulkheads and furniture and little or no fairing.

    Regarding Fall Guy's boat. If he had infused the panels instead of wet laminating and vacuum bagging them, he would have had far higher quality, much less waste and the finished boat would be appreciably lighter. His problems were nothing to do with peel ply, his epoxy usage was off the charts and his material choices (csm backed glass and foam in impact areas and heavy laminates over foam in non impact areas) were dubious. Several people with experience answered his request on how to proceed, Traditional Build with Corecell https://www.boatdesign.net/threads/traditional-build-with-corecell.57580/page-5 and were ignored. In another thread which I can't find he explains all his problems and again ignores advice on doing the job correctly. Entirely his prerogative, but the results were predictable and should not in any way be used to compare build methods.

    Re Ice Kite. Hopefully 1,700 sq'/160 sqm is a typo. We flew a 420 sqm kite on a lightweight 60' race boat and it was barely sufficient.

    Re daggerboards.
    If a boat is capable of 19 knots and the case and board are strong enough to resist impacts with logs and whales, what happens when you collide with one? More importantly, what happens to anyone on the boat who is not strapped in or holding on very tight when the boat decelerates from 19 knots/22 mph to zero almost instantaneously? This might help envisage the result at 21 knots/25mph
    Dagger boards are appropriately named. It is safer, lower cost, less maintenance and arguably better performance to have a centrally mounted kick up board under the bridgedeck.

    Re FAO boats.
    These were way ahead of their time and apparently there are a lot of them still around. Part of my boat building teaching in the Marshall Islands was to repair a 26' FAO cat. The hulls were polyester, csm and woven glass with ply bulkheads and deck. The ply has been replaced twice as far as they knew. We got it after it had been sitting on the beach for a couple of years. The hull was like new (after we removed all the crud), but all that was left of the ply bulkheads was the glue lines and compost at the bottom of the sheathing. Epoxy coating of ply is wonderful, but the smallest bit of damage or even an unsealed screw hole in a humid environment will rapidly destroy it.

    Old Multi, this thread is still a ripper, but could you please separate your thoughts, which I value, from the the press releases, etc the designers, owners and builders send out, some of which should be taken with a grain of salt.
     
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  13. Ralph J
    Joined: Mar 2019
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    Location: Durban South Africa

    Ralph J New Member

    Hi Im New Here.
    I would be interested to know what your thoughts on Bernds Designs are?
    I am about to order my Plans For his Pelican. The immage says 10.5 but the study plans etc say 11.5
    I want to Bi Rig it with either Junk rig's or a rotating soft wing sails.
    I have an interesting masts idea. but we will get into that later
    Ralph
     
  14. oldmulti
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    oldmulti Senior Member

    Bernard is a competent designer who has a history of producing good and often original designs. I ave only seen 2 of designs in the flesh a KD 860 and a small day cat. Both boats were structurally sound and were according to the owners relatively fast and simple to build from his plans. If his boats are well built using good west type systems they should last. His Pelican 10.5 was his first "home" build that is 20 plus years old. I think he may have modified and improved the design since then. I have written about bi plane junks on this thread before but the most interesting is Pete Hills extended KD 860 Oryx. The Junk Rig Association can provide further detail. Pete Hill also built and sailed half way around the world the 38 foot China Moon junk biplane cat.
     

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  15. YoungGrumpy
    Joined: May 2012
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    YoungGrumpy Junior Member

    There are some interesting (to me at least) ideas in Bernd' work. (I've got two study plans of his). However, the way it is put on the site is ... convoluted... to say. Added to that his peculiar way to communicate makes me hesitant to commit to a build. But obviously, it worked well for plenty of other folks.
    Maybe, my kind of crazy (no sane person would want to attempt to build a boat in his garage!) does not work with his (making a living from designing boats for home-building most certainly puts a person outside of the "normal" range:)).
     
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