Multihull Structure Thoughts

The 35XR useful load is listed as 2400 , disp at 6500 so abt 0.37 x 6500 , the 36 is 7900 disp , 2800 useful load so 0.36 x 7900 , the 37xr is 7300 disp , 3000 useful load so 0.41 x 7300 . At .37 x 5200 the 31 comes in at 1924 . I think my goal building with foam was 2200 useful load , that should be the bottom range . The 32xr may give you the better bang for your buck if it calculates in at the 0.41 x 4700 = 1927 without weight savings from a foam build .

 

163 sqm, sounds about right. Assuming that includes furniture.

2400 lbs is about 1100kg so about the same as the Waller, less than Scorpio which is 1500kg.

 

Sailing keeps developing as we learn more. In 2022, 52 new Mini 6.50’s racing monohulls have been built. As you can be spending up to €150,000 for a series (production) version and double that for a prototype version to race in the Mini Transat, they are developing fast. After spending this cash you may be on a 2 year waiting list to compete. Why is this so popular? Try this line (yet to be verified) “In early sea trials Boule’s fully foiling #1067 Nicomatic clocked 23 knots of speed in only 8 knots of true wind”.

When you look up results of the Transat you find no full foiler has won yet, the highest place is 4th place but the number of boats foiling is growing and if conditions are correct then a full foiler will win. So what is the current rules. The monohull boat series (production) is 21.33 x 9.9 foot with a weight of 2030 lbs with a maximum air height of 36.1 foot and sail area upwind of 474 square foot and a down wind sail area of 1,130 square foot. The maximum draft for series boats is 5.25 foot. The monohull boat prototype is 21.33 x 9.9 foot with a weight of 1830 lbs with a maximum air height of 39.4 foot and sail area upwind of 527 square foot and a down wind sail area of 1,240 square foot.. The maximum draft for prototype boats is 6.6 foot. The power to weight of these boats is high. The foiling boats have to start the race with a beam of 9.9 foot, after that the foils can be deployed to 17.7 foot wide sailing as long as the can be withdrawn to a maximum beam of 9.9 foot.

The “accommodation” in these boats is a sail bag to sleep on where it will fit, freeze dried food, energy bars and a minimum of water. You only have to accommodate 1 or 2 people. The toilet is a bucket at best, but you have a very good cockpit for sail control.

Now we get to why the above speed statement is plausible and a problem. These foiling minis can fully fly with lifting foils forward and T lifting rudders aft. Good. But according to Erwan Tymen, head of development at Pogo Structures, the numerous controls require a very high level of precision. As with wind angle, 5° of foil angle difference can equal 5 knots difference in boat speed, and this has led to a great deal of development work on the sails. The “numerous controls” means up to 50 lines to the cockpit to control the rig, foil angle, depth and angle of attack for each foil. You are working full time just to keep these boats flying at full efficiency.

The result of all this control is for a Pogo Foiler is an exhilarating ride, with boat speed hovering around 17-18 knots for extended periods in 18-20 knots of true wind. A test reported “With the log showing 16 knots at 130° off a true wind of 18 knots, the foil whistles, sending spray in the helmsman’s face, but that doesn’t dampen the excitement of sensations that are closest to those of a racing catamaran. The performance and reliability, if not the simplicity, originally sought by the yard are clearly in evidence. The Pogo Foiler is undeniably the cheapest prototype Mini 6.50 on the market. With 114m² sail area under gennaker, and a weight of 730kg, the Pogo Foiler has the same power as the Pogo 30, which displaces 2,800kg.” The peak speed of foiling Mini 6.50’s is over 26 knots. These boats are fast but difficult to keep near peak performance.

This results in some of the latest designs being semi foilers. Sam Manuard, a very good designer, vision and philosophy for a low-riding foiling boat with retractable C-foils that would offer a significant speed boost in medium and strong winds, without being at a disadvantage in light airs. The very full bowed scow has C foils for high speed sailing which can be fully withdrawn in light airs and a conventional daggerboard can be deployed for light air sailing depending on the hull shape for stability. The all-round performance of this style of boat is currently able to maintain higher total average speeds than the “stop start” approach of the fully foiling boats.

Xucia (the Sam Manuard design) therefore has relatively small retractable C-foils that boost righting moment, while producing a bows up attitude. This reduces the propensity for the boat to nose-dive into a wave, giving a smoother ride, while the extreme scow bow shape offers a lot of reserve buoyancy if the boat does splash down. Manera (the skipper) says this means good control of the boat is maintained all the time: “You are not flying, so the autopilot can manage and you can rest, because the boat doesn’t smash into waves, it just passes over them.” Getting the bows well up also reduces wetted surface area by up to 80%, which creates a massive speed boost compared to conventional boats. When the C-foils aren’t needed in light airs they can be retracted clear of the water – a big gain compared to the big foils of flying boats whose drag can never be eliminated.”

Translation. Foils are not always the solution to high average speeds. An all-round boat can achieve very good results by being a more useable boat taking less effort to sail well.

The jpegs give part of the story. The first jpegs are of Pogo Foiler then jpegs of the Sam Manuard design.

 

This is where my reality leaves and is substituted by those who have more cash than style or thought. The design is done by designer Steve Kozloff for someone with real money. The Epiphany is 178 x 127 foot with a displacement of 1,429,100 lbs (638) tons. The 145 foot high masts can be folded to 92 foot to help get under bridges. The 6700 square foot of sail area. Each mast can also rotate a full 360 degrees to maximize wind power. On top of that, the sails can be automatically set or dropped in a snap. The rig is free of pesky yards and shrouds, plus it has integrated load-sensing technology that tells the captain how much to drive it. The draft is 9.25 foot. The motive power is a single 2000 HP diesel electric with a range of 4800 miles.

Now we get to my confusion. Why. This is a moderate sailor, has only moderate power and is a Swiss Army knife when it is moored. This vessel is conceived for endless parties and social events with the occasional moves to the next “trend” location. The crew alone would cost $1 million per year let alone the maintenance and running cost of the vessel. Enough of my commentary.

The build is steel hulls and an aluminum superstructure with a lot of glass. The engineering required in the folding freestanding mast arrangement will be sensational.

There are cabins galore with a lot of open space to take who ever where ever. The 12 guests and 8 crew will lack nothing. The owner has a mere 700 square foot in the owner’s suite. The toy list on this vessel says it all, submarine, plane, scuba, boats, diving platforms, land vehicles etc. You will not be bored. As for its sailing ability or powering ability, yet to be seen.

This is for a rich person who wants others to amuse them, the boats function is to be the center of attention and if it happens to sail or power along its secondary. Good luck to any future owner. By the way Steve Kozloff in his early design phase (decades ago) did one of the fastest D class racing cats that was way ahead of its time. The jpegs give the idea. This as you can tell is just not my personal style.

 

Was it was Alex Kozloff who did the D-class boat? That's just from recollection.
I find most displacement motor yachts from days of old to be attractive and some very beautiful. Modern yachts are mostly offensive non-sensical to me. Is it just me? My hunch is that those people don't enjoy their yachting experience more than in the old days and they have such a high impact on the planet. I think someone paddling a canoe down the shore of a lake could find more joy than anyone "Yachting" today.
Sorry, this doesn't really belong in this thread, but I'll post it anyway...

 

Russell, you are correct it was Alex Kozloff who did C class and D class cats. Steve is son I think. Agree about simple boats providing more fun and satisfaction for the average person. How is the new tri going? Is the main hull started?

 

I’ll be brief.
It’s Vulgar.

 

IMO it looks like an open wound, but when I read the post I thought about all the boatbuilders who will be employed building it.

 

John Harris of Chesapeake Light Craft is often asked to design and build some fun craft at times. Billy and Sierra Swezey are professional bloggers who are developing a new cruising catamaran ad wanted at fun useful craft to act as a tender/fun device for use with the cat. They wanted a boat that could fit into a 12 x 4 foot shape for storage. If it could also enter the Everglades Challenge it would be good. OK, this matches the Philip Bolger request for a tender that could also be used as a tomatoe growing cover during bad weather.

Result for John Harris was the "Tallulah" design. "Tallulah" is 20 x 7 foot (can be folded to 4 foot wide and have its main hull ends removed to get the length down to 12 foot). The main hull width is 1.75 foot. The dry weight is 385 lbs with a displacement of 650 lbs. The float length is 12 foot with a width of 0.75 foot. The crab claw (or oceanic lanteen) rig has 90 square foot of sail area. The motive power is a Mirage Drive (from Hobie) powered by a crew member.

The main hull can sit 2 people with extra stowage space. The whole boat can be packed up into the 12 x 4 foot box shape.

The structure for the main hull is strip plank WRC with carbon fibre on each face. The deck is strip plank with S-glass either side. The gunnels and bulkhead frames are timber as are the bow and stern. The bulkheads and Mirage Drive box are plywood. The floats are Styrofoam covered with carbon fibre and an S-glass twill. The cross arm support structures are carbon fibre. The cross arms are laminated timber. The spars are timber.

This is a very useful tender and fun toy for sailing around. It successfully entered the Everglades Challenge. A good solution well done Mr Harris. The jpegs give the idea.

 

Forgot a very good jpeg of Tallulah. You can see the bow section has a line part of the way back that is the "split" point to shorten the 20 foot boat to 12 foot. There is a matching line at the stern to shorten the tri to 12 foot.

 

A small update on the Wayne Barrett designed M60 trimaran which is designed with the home builder in mind who has limited time but basic experience with small hand tools. The M60 is 19.6 x 15.74 foot which can be folded or disassembled to 8 foot. The weight is 1100 lbs with a displacement of 2000 lbs. The 28 foot mast (Hobie rigs acceptable) carries a 150 square foot mainsail, a 65 self tacking jib and a 161 square foot Code 0. The outboard power is 5 to 10 HP.

This tri is a simple flat panel shape with a chine ull etc. The real reason for this item is the options of reducing the beam. Either a Farrier type folding system (a little simpler) or aluminium tubes that can be disassembled. The tubes in a design this small can be very light and the floats can be handled by 2 people. The Hobie type rig is easy to deploy.

This is basically a day sailor or camp cruiser. The cockpit is large with a small cuddy forward for some protection.

The build is stitch and glue with 6mm plywood to put a set of hulls together. All glass cloth is 300gm2 with the hull bottom having one extra layer for protection from grounding or running up onto the beach. Epoxy work on the structure is predominantly cove and fillet. There are foam glass versions that have been built.

The jpegs give the idea.

 

...so far I have not comprehended the logic behind all those "reverse bows", fashionable these days (aesthetics of the time that an oldtimer cannot comprehend?). For a given pitch-angle a flared/overhanging bow has a much larger reserve bouyancy resisting a further nose dive, than a reverse one. Of course once the bow is really diving the resistance of the larger fordeck of a flared bow will be greater & assist in pitchpoling, but it would take much more to get that far.
Can somebody enlighten me?

 

It’s a race driven thing, slicing through the chop stops pitching rather than bouncing up and down shaking the wind out of the rig, faster but wetter.
Edit; And longer waterline.

 

In the PNW the up and over of conventional bows is a help with the logs and drift.... Very old fashioned I know but I cruise.

 

Cons: You can't get right up front to fend off expensive crunching noises.
Possible hassles with anchor rode. Possible ride under instead of over logs, whales, whatever. And wet. If you're going fast, very wet.
Pros: Slight advantage for racing boats. Looks really cool, hints of Star Wars, stylin' baby!