Multihull Structure Thoughts

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

  1. guzzis3
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    guzzis3 Senior Member

    jamez: Agree 100%.
     
  2. oldmulti
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    oldmulti Senior Member

    For the next few days I will be doing some trivial stuff as I have a tax problem to solve. Not that the boats will be trivial just the items will be short and simple. First the Kelsall KSS X-Kat 26. The 26 is 26.2 x 14 foot with a displacement of 3350 lbs. The sail area of the mainsail is 247 or 280 square foot with a jib of or 120 or 140 square foot depending on the mast height chosen. The draft is 2 foot over the low aspect ratio keels.

    The novel beam system is based on simple, sliding beam parts. The rudder and outboard operate in either the narrow or the wide condition. The expansion and the raising of the mast can take place while underway under outboard motor. Derek explained the design of the sliding beam system to me and I came away convinced of 2 things, it needs to be built well and it requires some careful design engineering up front as the beam join overlaps are not large. I have watched an International 23 being pulled apart with its sliding beams and it was difficult to pull each hull out separately in perfect alignment to prevent binding.

    The accommodation in this design is in the hulls with 4 berths and a minimal gally loo etc.

    The build is a typical Kelsall. Composite construction E-Glass, PVC foam and polyester resin. This has worked for Kelsall for decades and if done well will last for decades more.

    The limited jpegs give the idea.
     

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  3. redreuben
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    redreuben redreuben

    XK26 And how much are the plans ?
     
  4. oldmulti
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    oldmulti Senior Member

    Expensive.
     
  5. Hell_Bent
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    Hell_Bent Junior Member

    No doubt.

    There is a "New" version of that cat apparently and it looks positively hideous in comparison. How much resin where they sniffing when they came up with this one: KSS New X Cat 26
     
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  6. peterAustralia
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    peterAustralia Senior Member

    Just a little aside. I have been in recent email contact with Glenn Tieman, Glenn built the Wharram Tama Moana catamaran that has low windage and two crab claw sails in ketch arrangement. Glenn says that upwind performance in jaw dropping. He says he has refined the sails after 15 years of sailing.

    So it may well be that good upwind performance can be had if sails are good, the boat is light, and the hulls have low windage, and in doing so you can possibly eliminate daggerboard and or centerboard
     
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  7. Hell_Bent
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    Hell_Bent Junior Member

    Interesting. Most testimonials from people who have sailed well-designed crab claw sails in real world conditions seem to rave about them, whereas most people who theorize about them on the internet seem to bash them constantly (speaking as someone who theorizes constantly about many things on the internet). I know who I trust more, and you can probably tell from my profile picture. This may also be an unpopular opinion, but when done with purpose they also look better than any other rig IMO.
     
  8. oldmulti
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    oldmulti Senior Member

    PeterAustralia. If you have a relationship with Glenn Tieman please email him about the rig and cat. We are here to share information and understand the advantages disadvantages of multihulls, there structure and rigs. I full agree we have a lot of opinions about crab claw rigs but real world ocean sailing facts really help. There are no "absolutes" is multihulls, just development of solutions to suit individual sailors. Glenn has proven a simple low windage cat can sail well with an "old" rig. His experience would be welcome.
     
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  9. oldmulti
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    oldmulti Senior Member

    This is about a cheap 71 foot catamaran built and designed by Hans Klaar based on Anaan, Tuamotuan canoes as seen by both Commodore Wilkes and Admiral Paris (approx. 1845). The cat has a 71 foot starboard hull and a 57 foot port hull with an overall beam of 22 foot. Each hull is 8 foot wide at the gunnel. The differing hull lengths is conceived to reduce crossbeam loads. The displacement is thought to be 15800 lbs but a second version of the same design was weighed in New Zealand weighed 22,000 lbs. The rig size is unknown but is made from solid wood masts and spars. The sails are made from tarpaulins with a total cost of the entire rig of $2000. I said this boat is cheap. The length to beam of the hulls is about 8 to 1. The power is a 5 hp outboard, yes this cat is a sailor not a power machine.

    The accommodation is basic but there is sufficient space for berths, seating, galley, toilets etc.

    The performance of “Ontong Java” latest version (there have been 3 so far, a Wharram cat and 2 versions of the above) is interesting. The jib is there to improve balance as upwind, but for the long distance passage making the sailing is mainly reaching and running. The crab claw is simple to handle, cheap to build and easy to repair. Theoretical hull speed is 17 knots but Ontong Java rarely travels that fast. Hans says: “180 to 200 miles a day is the normal, and that happens with barely lifting a finger. The boat more or less sails itself. Hans reads a lot and carries a lot of books and a lot of surfboards. Tacks like a dream all one way, no hanging back at the last moment, and takes off once through the eye of wind almost at once, holds a good 50 degrees on the wind and leaves a nice straight wake aft. I can handle her totally on my own, self-steers very well. Something funny goes on with this one mast that seems to make it possible. One example is 400 miles in 40 hours, jib to tiller steering (controlled surfing if one can call it that) with fully reefed main in 28 knots of wind.” This cat is travelling around the Pacific.

    Now we get to the build. Find yourself 2 bare tree trunks 4 foot diameter and 27 feet long, cut a supply of 45 mm thick planks. The planks in the hull are overlapped and bolted together using stainless steel bolts, washers and nuts. The hulls are strongly V shaped. Between the planks are strips of rubber taken off an abandoned conveyor belt. There is also a sealant made of melted car tyres and plant oils, and some other strange things. The hull decks are plywood. The bridge deck between the hulls is covered with wide planks secured by fishing line. There are 7 solid timber cross beams that are tied to the hulls as per Wharram. The rudders are large and tiller controlled. The cat was mainly built on a beach.

    As you can see from the Jpegs it is an original conception that suits Hans. We all learn that you can built a cheap big boat if you want at 20% of the cost of a production catamaran. The cat is relatively easy to sail and control. Interesting.
     

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  10. oldmulti
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    oldmulti Senior Member

    This tri is an interesting design done by a guy who wanted to do the Race to Alaska. He had completed in several RAK’s in mainly light mono’s before this design. The SRC Tri 19 is 19 x 14 foot (tri can be folded to 6 foot for trailing etc) and is expected to weigh 400 lbs. The maximum displacement is expected to be 1000 lbs. The 20 foot single mast rig has a sail area upwind is 260 square foot. There are drawings of 2 mast rigs but the write up only mentions the single mast rig. The main hull length to beam is 11 to 1. The floats length to beam is 15 to 1. The draft is 4.75 foot with the board down. Beside sail the other method of powering is oars for the RAK. Akas fold to bring floats in close to the main hull for rowing, docking, transport, etc.

    The design hull shapes look good but please understand the real design issue with tri’s is the interaction of the floats and the main hull. The centre of buoyancy of each have to be positioned correctly to achieve good all-round sailing performance with minimal pitching. Early tris had the centre of buoyancy in the same fore aft position, but modern tris have the float centre buoyancy slightly forward of the main hulls to reduce pitching. Also the shape of the float moves the centre of buoyancy according to load on the floathull. You need to understand all these buoyancy shifts to get a well controlled tri.

    The centre cockpit arrangement is mainly for sailing. The aft and fore cabin can squeeze a single berth inside and some storage. This is a racer more than a cruiser. Waterline beam of the vaka is under 1.9 foot. Cabins are 2.9 foot wide at shoulder height (sitting on the bottom of the hull) and have shelves and mesh pockets for storage.

    She’s stitch and glue construction with 3 mm Okoume plywood with 200 gsm (6 oz) fiberglass/epoxy on the outside of the hulls (plus a layer of 132 gsm (4 oz) from high chine to high chine on the vaka), 132 gsm (4 oz) fiberglass inside the hulls and 132 gsm (4 oz) outside the topsides.

    The builder expected to have her on the water sometime in April 2020– in time for sea trials, modifications, experimentation and cruising for at least a month before the race to Alaska. Covid then hit and there has been no further indication if the build was completed or raced. The jpegs show the drawings of an interesting design.
     

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    Last edited: Feb 1, 2022
  11. oldmulti
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    oldmulti Senior Member

    This was to be an update on the Simpson-Wilde 26 called THREE FINGERED JACK but it took a few deviations. The Simpson-Wilde 26 is 26.5 x 18 foot of unknown displacement (read light) carrying a 31 foot mast with 174 square foot main and 196 square foot genoa, a 105 square foot jib and a 38 square foot no. 3. The length to beam on the main hull is about 7 to 1. The rudder is hung on a skeg and centre boards are in the floats. The floats have 100% buoyancy. THREE FINGERED JACK did the Round Britain Race in 1970 finishing 10th in 17 days. Andy Simpson, designer of THREE FINGERED JACK built with his brother and is cold moulded plywood on stringers, frames and bulkheads, the hulls were 2 layers of 3 mm. The cross arms are timber and ply. A “production version” of the 26 in the USA was called the Slipstream 26 and was done in foam glass. Several were built, but it was too early in the US market for a commercial success. (first set of jpegs)

    Prior to Simpson-Wilde 26 Andy Simpson designed “Shangaan” built in 1969. The 24 x 16 foot Shangaan’s has a 25 foot mast carrying 180 square foot of sail. The main hull is 7:1 and the construction is plywood over stringers and frames covered with glass again. (yellow tri jpegs).

    Next came a guy who found a wreck of a “Simpson 26” foot tri that actually turned out to be Sloopy or Paradigm, a 28ft 6in (8.7m) long design was the first Simpson-Wilde to be built by us in foam sandwich. The final set of jpegs.

    All these tris looked good, THREE FINGERED JACK and Shangaan could really sail well across a range of conditions including going upwind in force 7 winds. 7 to 9 knot averages with peaks of over 18 knots. The ply tris are strong and have lasted decades. The 28.5 foot version in foam glass looks moderately OK even though its been sunk for a while. Good boats.
     

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  12. oldmulti
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    oldmulti Senior Member

    A new material with potential for boat building. It’s a “2D polymer” that is as light as plastic but stronger than steel.

    Chemical engineers from the Massachusetts Institute of Technology (MIT) in the US have just forged a new material that is as light as plastic and stronger than steel. It’s the result of a feat thought to be impossible: creating a two-dimensional polymer. All other polymers form long, one-dimensional chains, but this new substance comprises of a polymer that self-assembles into 2D sheets. According to MIT’s Michael Strano, senior author of the new study in Nature, potential applications include coating car parts or cell phones, or as building material for bridges. “We don’t usually think of plastics as being something that you could use to support a building, but with this material, you can enable new things,” he says. “It has very unusual properties and we’re very excited about that.”

    Plastics are all made up of polymers, shaped into 3D objects like food containers or water bottles during manufacturing, by injecting heated polymers into a mould.

    The new material, dubbed 2DPA-1, has several useful properties: it’s twice as hard to break as steel despite being one-sixth less dense, and it’s 4-6 times harder to deform than bulletproof glass. 2DPA-1 is also impermeable to gases, as it’s made up of monomers locked together like Lego bricks, so gas molecules cannot seep between them like they can in polymer chains. “This could allow us to create ultrathin coatings that can completely prevent water or gases from getting through,” Strano says. “This kind of barrier coating could be used to protect metal in cars and other vehicles, or steel structures.”

    However, in the new study, Strano and his colleagues came up with a new polymerization process that allows them to generate a two-dimensional sheet called a polyaramide. For the monomer building blocks, they use a compound called melamine, which contains a ring of carbon and nitrogen atoms. Under the right conditions, these monomers can grow in two dimensions, forming disks. These disks stack on top of each other, held together by hydrogen bonds between the layers, which make the structure very stable and strong.

    https://news.mit.edu/2022/polymer-lightweight-material-2d-0202

    The jpeg below gives some clues as to strength. Graphene can be a “stronger” version of carbon fibre. 2DPA-1 is about 25% “stronger” than Graphene in thin coatings. This product needs to be followed as it develops as it appears to be waterproof, strong and able to be formed like plastic kayaks in moulds etc. From this sort of research came carbon fibre. Sanity will prevail tomorrow.
     

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  13. SolGato
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    SolGato Senior Member

    I really like the look of those Simpson-Wilde, especially the one that was recently salvaged and posted about. Your feature included a photo from a different vantage point which shows that the deck at the bow is sort of duck billed, perhaps to keep spray down or maybe just a continuation of the winged beams. Some interesting design features for the time. I hope the salvaged example finds a good home and is able to be sailed and enjoyed again.

    Speaking of building materials, I don’t believe this thread has featured the PlasTiki catamaran build. One take away from studying and following that build and sailing adventure was the development of a PETE woven sheet that they created a process for to bond it to ridged foam using pressure and heat that they then used for things like the cabin structure. When I looked into the company that was manufacturing the woven plastic material (sort of like fiberglass mat), I remember it being extremely expensive at the time. It was an interesting process because they basically heated the woven material and foam core up to the temperature that plastic welds together and ran it through a roller to laminate it.
     
    Last edited: Feb 3, 2022
  14. guzzis3
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    guzzis3 Senior Member

    2DPA-1 It will be interesting to see how stable it is and it's resistance to things like UV.

    There are already high spec materials. The 2 things that prevent extensive deployment are cost to manufacture and work and specific difficulties with the material.

    The reason bridges were once built out of stone was labour was cheap and stone readily available. No one builds bridges out of stone anymore. Engineers have a range of materials to choose from. They tend to choose the same ones over and over as they meet performance requirements at good cost. If this new material presents a real overall advantage it will be taken up.
     

  15. rberrey
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    rberrey Senior Member

    guzzis3 is right , it will be like carbon fiber or fiberglass rebar , it has never caught on even with the many advantages it offers . A State Engineer here in the U.S. won't hardly approve a new concrete mix unless there is no other choice , so you won't see it in a bridge . If it is cheaper and better than steel it will find it,s way into the private sector , but I doubt it will be used on any major structures anytime in the near future .
     
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