Multihull Structure Thoughts

Due to a small issue, I have had to put in another item for today. This is about serious money dreams. For a German entrepreneur, that means commissioning a futuristic yacht with a unique approach to efficiency – a gargantuan kite that helps pull it along. Ice Kite, which is still in the design phase, was conceived collaboratively by Red Yacht Design, Dijkstra Naval Architects in collaboration. Ice Kite is 210 x 35.5 foot monohull that displaces 450 tons is powered by two 1000 hp engines and carries a 1700 square foot kite rig. Ah what! A 1700 square foot kite rig that soars 600 feet in the air (think kitesurfing, but a lot bigger, fancier, and more expensive) to improve its fuel efficiency. Ice Kites maximum speed is approximately 17 knots.

Ice Kite hull is designed to be efficient over the entire speed range and not only in a restricted speed interval around the maximum speed. This is accomplished by waterline entries, a high slenderness ratio and low wetted surface area due to a round hull shape. Other significant features include increased comfort on-board with better sea keeping and wave reduction. A well proportioned daggerboard is applied to enable the yacht to make full use of the Kite propulsion system at closer wind angles. Ice Kite has an aluminium hull with a carbon fibre superstructure and light weight strong glass panels as windows etc.

The buyer is also commissioning an 86 foot support vessel that will sail with Ice Kite, called ICE Ghost which can carry an Icon A5 airplane, a U Boatworx Superyacht Sub 3, a 12 metre custom-made performance RIB with a top-end speed of 60 knots, also designed by Red Yacht Design, and a pair of Seadoo jet skis on her main deck. There is a further garage space for holding diving equipment, SeaBobs, and an on-site maintenance area. The main deck of ICE Ghost can alternatively be used as a party space and two twin cabins below deck can host guests or staff. With a steel hull and carbon fibre exterior, ICE Ghost can reach a top speed of 16 knots.

The jpegs are of the initial design(s) and gives a glimpse into future technology that may be applicable to multis.

 

And here we are being worried about a guy fairing chines on 18' 'scarab... Most likely, he was dreaming as well.

 

John Taylor decided he wanted to build a catamaran for himself. He had a friend who designed and built a 35 foot cat that performed well. John said that was a good 35 foot design, I will just extend it to 44 foot by spacing the frames further apart. After doing the appropriate calculations to verify the hydrostatics of a 44 foot version he started to build the complete and I mean complete boat with his father.

The cat is 44 x 25 foot that weighed in at 8000 lbs without its rig and displaces about 15,000 lbs. Ocean Swift has 13 to 1 length to beam hulls. The sail area is unknown but judging by the 58 foot wing mast and the size of the fully battened mainsail it would be relatively large. The cat’s performance is very good having crossed the Atlantic from England to Barbados in 9 days. Ocean Swift achieve speeds of up to 25 knots with John saying it gets interesting when you are sailing above 18 knots.

The Ocean Swift 44 was completed in 2015. It used WEST Epoxy throughout the build, including for the Israeli Gaboon plywood beams and the strip-plank hulls and decks. The builder said. “But we know we can make our boat as lightweight with Western Red cedar and WEST epoxy as we could by using a foam.” Epoxy was also used for glassing the boat. The outside of each hull was treated with epoxy and then 600g/m2 biaxial glass cloth applied at 45 degrees to the planks.

The planking is made from a job lot of Western Red cedar and Douglas fir (100 x 50 mm) lengths, which John and his father cut into strip planks themselves and kiln-dried; with an estimated six miles of planking needed, this was a labour-intensive process. All the stainless steel fittings are also made by hand. John machined and built all the metal fittings such as turnbuckles, terminals etc. He is a skilled and determined man. He also built the mast. John has even built an ingenious dual outboard motor system which extends and retracts through doors in the undercarriage near the stern; this gives the boat excellent maneuverability.

The combination of wood, ply and epoxy also delivers excellent strength. “There’s a lot of downward mast thrust, so the beams must be strong,” says one of the builders. “By positioning the ply grain at 45 degrees to the beam and using epoxy, we get maximum strength. There are no mechanical fastenings; it’s purely epoxy holding everything together.”


The jpegs give the idea. John Taylor also wrote a limited release small book about the boat and build.

 

That's what I like, none of those multi million super yachts that only serve to remind you how our scene is now driven by the obscene (wealth that is) but a boat hewn from effort and talent. I must find that little book.

 

That Ocean Swift is something. What country was it built in?

 

Catsketcher and Russell. Ocean Swift was built in Britain. If you put "Ocean Swift" catamaran (with the exclamation marks) in a google search you will probably come up with 2 or 3 video's. One of the builder being interviewed at a boat show about 8 minutes and at one point shows the cover of the "book" that was written. The second video is a sailing trip to Saint Kilda at the top of UK and a final video of sailing in the Caribbean (click on images to show this video start). Each sailing video is short. I am trying to find more detail. John Taylor is on Linkin for direct contact but the web site https://ocean-swift.net/ is still under construction.

 

The Triptyque 24 A is for amateur boat builders. The performance cruising tri is 23 x 18 foot that able to be folded to 7.9 foot for trailing. The weight is 2,000 lbs with a displacement of 3,350 lbs. The 29 foot mast carries a 220 square foot main, 115 square foot jib, 255 square foot gennaker and 460 square foot spinnaker. A big Hobie rig could be substituted but your reaching the upper limits of what a Hobie rig can handle considering the stability the 24 A can generate. The boat should perform very well judging by the sail area and displacement.

The 24 A has more space, more volume, more load carrying capability than the Triptyque 20. The 24 A has been designed to be simple with a reduced number of parts required for the of hulls decks. EG the roof requires only 6 pieces of plywood. The main hull shape is a simple shallow V bottom shape. The majority of the tri is in epoxy plywood with timber stringers and frame reinforcement.

The Triptych's hull retraction system has no articulation between the arms and the side hulls. The cross arm halves are one unit and can withstand significant shocks without deformation. The cross arm halves slide in slots beside each other in structural units in the main hull. The guides and rollers used during the retraction of the side hulls are not subjected to any load once the safety pins are in place. The rigging forces are taken up through the side hulls by retaining sea stay cables taken from structural bulkheads of the central hull to the floats. Once the sea stays are stretched, the arms only work in compression. However, the cross arms have been calculated to resist the bending generated by the boat's maximum righting torque to provide maximum reliability of the system. The rollers are interchangeable without disassembly other than removing the retaining cable and releasing the arm from the slide: just remove them and put the new ones back in place. A visual verification operation must be carried out every year (without dismantling), and the change of the rollers is no longer necessary since the use of a plastic resistant to heavy loads. The curving of the 160 mm cross beam half tubes will require a specialist to make it consistent over the 4 tube halves. The reason for the curving is to push the floats down for more stability in the folded mode. The same could be achieved by slightly angled straight beams but it will require some designing to maintain the cross beam length and not to interfere with the other float when folded.

The headroom 5.8 foot with a double and 2 single berths in the basic configuration. There is a small galley and table. A porta potti can be stored under the cockpit. A 15 HP outboard provides the power. The plans are very complete and detailed including all the cutout sketches of the plywood panels. The construction cost is relatively low, (from 8000 € to 15000 € depending on your resourcefulness) and if you’re a good handyman that can practically make everything eg cross arms, mast etc.

These boats are being built in production as well as a plywood amateur plan version. The jpegs give the idea.

 

Back in 2007 I started a subject thread,
New Age Trawler/Motorsailer; Kite assisted PowerYacht
New Age Trawler/Motorsailer; Kite assisted PowerYacht https://www.boatdesign.net/threads/new-age-trawler-motorsailer-kite-assisted-poweryacht.20319/

It turned into quite a long subject thread.

Humphreys edition was a big inspiration,..


Then I suggested a kite assisted Powercat

 

A bit hard for me to get my head around those curved beams on the Triptyche. Really like the Ocean Swift, Super clean and simple lines and all wood/epoxy. They even have a super light rowing dinghy.

 

Russell I agree with you. The reason for the beam design I am presuming is to provide more stability from the floats when the tri is folded. I did some drawings with straight beams slightly angled down (float side higher, main hull entry lower) and you can achieve a maximum beam of about 18 foot using the same folding principle with straight beams. The assumption used by this model of folding is the when the floats are fully out the pin holding the cross arm in position at the main hull is purely in compression and the waterstays are taking the tension load to resist the overturning moment. The problem of this model is as you push the floats out the waterstays are not taking any of the tension load putting a potential twisting load on the beam sockets in the main hull. So its either fully out or very close to fully in to handle the loads. Yes the Ocean Swift is a really good design/build. We need more detail on the Ocean Swift 44.

 

Here is a nice article in the Epoxycraft journal about Ocean Swift -
Ocean Swift: a self-build like no other - Epoxycraft https://epoxycraft.com/westsystem/ocean-swift-a-self-build-like-no-other/

At the end of the article they mention John Taylor's email address.
Oldmulti, maybe you could send John an email and invite him to join in on this discussion?

 

Bajansailor. The web address for John Taylor mentioned in the Epoxycraft article no longer works. I am not a member of Linkedin but this may be a path to contact him. Could a member who has access to Linkedin approach him please. Could you please advise the group if you are going to contact him as I would not like him to get multiple contacts.

John Taylor is at https://uk.linkedin.com/in/john-taylor-060a0b65 A possible message is below.

John. I have been requested to make contact with you to ask if you would like to make a contribution to an internet group about the “Multihull Structure Thought” thread on “Boat Design” net. The thread focus is on the design and structures of various multihulls. It covers all types of multihulls cats, tris, proa’s and very occasionally mono’s.

The web address of the first page is Multihull Structure Thoughts https://www.boatdesign.net/threads/multihull-structure-thoughts.62361/ and the page relevant to your boat is Multihull Structure Thoughts https://www.boatdesign.net/threads/multihull-structure-thoughts.62361/page-80

There was great interest in your Ocean Swift 44 design and build by the group. The group who are interested and make occasional contributions are from multihull owners and home builders to some naval architects.

 

Staying to the theme of home built multihulls, not millionaire boats, I present a boat I have mentioned before but have just found jpegs of. The following 100 foot long home built steel cat was built by a guy at his home in Bairnsdale Victoria. He was a school teacher who had up to 10 weeks a year “holidays” and only had to work 6 hour days 5 days a week. This allowed him to put up to 4000 hours a year into the boat. He did the majority of the boat himself over the 10 year build process. The boat was initially used privately before going into charter in Melbourne then charter in Queensland. Last time I will complain about a 22 foot cat build. The jpegs say it all.

 

I have just sent John a brief message on Linked In - it was limited to 300 characters, as I do not have the premium version of Linked In.
But I mentioned your link to this page, and I invited John to 'join in' if he would like to.

 

That 100' steel cat is very impressive! A real labour of love over 10 years - that requires serious 'staying power' to keep up intense momentum and enthusiasm over such a long period of time.
Do you have any further details about her? Did the builder also design her as well?
I 'tip my lid' to him (and also to John with Ocean Swift) - I see that the 100' cat appears to be round bilge construction, which would be a lot more difficult (re rolling plates etc) than multi-chine construction.