Multihull Structure Thoughts

I've got plans for versions with the beams and the wings.

 

I'm too lazy to search, and cant remember - has *Project Interrupt* been mentioned?

He's made it to Bass Straight, so already doing better than many expected...

Project Interrupt - Project Interrupt https://projectinterrupt.com/

 

Project Interrupted is Samuel McLennan passion to tell the world to respect our environment. He spent two years building his 'rubbish raft'. Sam said "This vessel is a demonstration of what's actually happening out there in the marine environment, this is only a small amount of the material that's out there, it’s been incredible to build something out of it. That rubbish comes from commercial practices, but also recreational practices."

McLennan said his vessel includes buoys and pipes from fish farms, oyster bags, and fishing ropes and lines. As he sails north, Sam will stop in communities and wants to use the vessel as "a structure for conversations".

Earlier this month, McLennan was prevented from leaving when Heart was de-registered by maritime authorities. They described the planned ocean journey as "foolhardy" and said they’d need written confirmation from a qualified marine surveyor or naval architect that the raft could handle ocean conditions. On the advice of marine surveyors, it has now been given conditional registration to sail in sheltered waters no more than two nautical miles (about 4km) from the coast of Tasmania. Sam has sailed about400 miles so far to make it part of the way along Bass Strait. His next journey will be to cross Bass Strait (about 200 miles) then sail 500 miles up the Australian coats line to Sydney.

Warning, the structure of this boat (raft) should not be duplicated by anyone if they intend to sail out of sight of land. This vessel depends entirely on ropes plastic piping (water type pipes) and used buoys and or drums. Used plastic oyster bags and sheeting is used for the cabin structure over bent water pipes. The sails are used tarps etc. Good weather and good luck will be required to complete this journey.

There are a few extra jpegs to give the idea of a very flexible raft.

 

Cavalier Mk2. Do you have study plans or full plans? I respect that Newicks designs are still being sold so detailed plans would not be appropriate. Does it have any structural information you would be willing to share? We do not need fine detail but eg Cold moldcd 3 layers of WRC or eg 15 mm foam with 1200 gsm skins etc. could be good.

 

I have the complete plans for several boats in the 3 Cheers series and a few others after talking with Dick and working with the Mariners Museum to digitize them with the understanding that I can't reproduce them. As I understand it Pat Newick is selling the Newick designs now? so inquiries about acquiring them should be directed to her.

At the time we were talking about a fast cruiser based on Three Cheers with more capacity, funnily enough we both preferred the flow of lines from his pre computer designs, the hand drawn ones seem to have more art. This wasn't about the nth degree of modern efficiency but sea keeping, motion and sailing sculpture.

The 3 Cheers hulls were used in quite a few designs, the slightly shorter one came about to work with a potential rules change. What did change were the connective structures, layouts and rigs. I don't have drawings for the Val type beam but do have plans in wood and glass foam for separate beams, more like Moxie, and the full aero wing.
One boat has constant camber amas to a different design. I don't think there is a problem with talking about. a few scantling in general, which ones? Later layups? MK1 polyester? Wood WEST?

 

Nick Keig is a determined man who liked sailing and wanted to race in a boat that he could occasionally cruise. He was drawn to multihulls, so in 1973 went to Derek Kelsall to design him a trimaran that he could build at home and be fast. Result, Three Legs of Mann (version 1). After racing successfully Nick wanted a bigger tri and home built a 53 foot Kelsall design (also named Three Legs of Mann) in 1979. Nick was a fast, effective home builder who keep his builds simple with minimum fitouts.

Three Legs of Mann is 36 x 24.75 foot with a claimed weight of 4,500 lbs. The tri in 1978 had part of the bow cut of to meet the under 35 foot rules for some races and was listed as 34.5 foot long. The 45 foot aluminum mast carries 753 square foot of sail upwind. The length to beam of the main hull is 15 to 1 and the length to beam of the float is 18 to 1. The draft over a centreboard is 5 foot. The rudder is a kickup on a metal frame. The draft over the hull is 1.8 foot.

These numbers indicate speed was the aim of the design and any accommodation was a secondary consideration. I do not know the accommodation layout but there is sufficient room for a couple of berths, seat and a small galley and toilet.

The construction is Airex foam e-glass and polyester resin. The cross beams are aluminum tubes. Now this design was the forerunner of FT a 35 foot single handed tri that Kelsall design for David Palmer for the OSTAR. FT had serious issues with its aluminum cross beams and had to have fiberglass crossbeams made for FT.

The reason I mention this is, the only significant difference between Three Legs of Mann and FT is the waterline length. FT was designed to meet rules that had a 28 foot waterline length, Three Legs of Mann has a waterline length of about 32 foot. FT shorter water line length and 2 foot higher mast caused additional twisting in the cross arm structure with additional torque loads on the rudder due to the floats having to do more of the pitch and buoyancy control fore aft. Result, stronger cross beams and rudder structure required. Multihull design is about balance of various forces, push to far in one area and problems occur else where.

Back to Three Legs of Mann. This tri raced very well winning many local races outright and in class. EG It came 5 th overall in the 1974 Around Britain Race etc. Its best days run, single handed, was 340 miles in 24 hours at a 14.2 knot average. This was a very good advanced tri design for 1973. It was still racing in 2014 with only 2 replaced masts over its life time. From my knowledge it is still sailing.

The jpegs give the idea of an excellent design that was the fore runner of a lot of modern designs.

 

So to keep this easy I'll give ama scantlings of several versions. For metric guys, get your conversions ready.
For starters most of this stuff was designed to come off strip planked molds with the stringers and bulkheads put in after building the skin.

For early 70s MK2 the male mole had 1x2 battens 6 inches apart with mold frames every 3 feet. Planked with 1/2" Airex foam then covered with 2 layers of Liasil (uni directional fabmat) 45 degrees from center, one layer 8" wide along center line, exterior finished with 3/4 oz mat. Remove from plug then cradle and add 2 45 degree layers of Liasil then the bulkheads etc .. even this early date had plenty of carbon tows is strategic areas. Foam glass beams.

Those constant camber amas from the early 80s were done on a 30' mold and features 3 plies of eastern white cedar 5 or 6mm thick vacuum bagged using epoxy, outer skin 8 oz woven roving or 4 oz polypropylene.

Wood MK 3 amas featured 4 1/8" layers of Western red cedar.

A later foam glass design using epoxy had 3/4" core and double the Liasil layers for a more burdensome cruising version.

Dick used a lot of different methods to suit the use of the boat and builder of these designs.

 

CavMk2. I’d call that rather overbuilt compared to Aus wrc build methods.

 

Could be Red, Im not sure how much Dick kept tabs on Oz builds. For the most part they didn't break and they won a lot of races. Maybe an Atlantic Pacific thing? Different neighborhoods. The wood scantlings aren't at all heavy. Remember the Constant Camber amas didn't have stringers etc.... the idea there was use a thick skin for strength. I think that was early in the method too

 

I guess what I'm reacting to is the 3 and 4 layers of diagonal planking, we never had the luxury of so much timber ! Double diagonal was usually thin ply, I'm sure there are exceptions where cost was no option but varieties of cedar in veneer form, LUXURY !

 

Plant trees and eat koalas? Just kidding. Yes we are decadent over here. Dick used a lot of strip build too. In later years he really preferred foam. Personally 3 lams would be my patience limit. Lots of molds to build a Newick unless you do stringer frame methods like the Gougeons. Those fairings and wings take some thought.

 

After Nick Keig built and raced the 35 foot Three Legs of Mann he went back to Derek Kelsall to design a larger tri he could race and seriously cruise. Derek designed a 53 foot tri which Nick built in 1977. Nick called it Three Legs of Mann 2 and again it was successful racer but also a good cruiser.

Three Legs of Mann 2 was 53 x 30.1 foot with a weight of 13,500 lbs. The 67 foot mast carries 1,545 square foot of sail upwind. The length to beam on the main hull is 10 to 1 and the floats length to beam is 14 to 1. The draft varies from 2.3 foot to 7.75 foot over the daggerboard.

But Nick was not finished, in 1979 Nick built an upgraded version of the 53 foot tri called Three Legs of Mann 111. Three Legs of Mann 111 is 53 x 34 foot with a weight of 16,000 lbs. The mast is 70.5 foot with 1,720 square foot upwind with a 2150 square foot spinnaker. The draft is reported to be between 2.5 foot and 6.6 foot over the main hull based daggerboard. The engine is a 50 HP Perkins diesel inboard. Again this tri was a race winner.

So, what are the differences. Three Legs of Mann 111 is basically the same main hull but has a 12% wider beam, a 5% higher mast and 11 % more sail area but is 11% heavier. Three Legs of Mann 111 also appears to have more buoyant floats. Translation, Three Legs of Mann 111 is a faster, more powerful and probably stronger trimaran capable of maintaining slightly higher averages across a wind range.

The race results of Three Legs of Mann II won both the Round the Island Race and the Azores Race in 1978. But in the Route De Rhum Three Legs of Mann II was damaged and needed to seriously repaired. In 1979/80 Three Legs of Mann was reported abandoned after an attempt at the NY-Cap Lizard record while sailing slowly under small sails, a double wave capsized Three Legs of Mann II which was abandoned.

For Three Legs of Mann 111, Nick KEIG entered Transat 80. In the OSTAR it came 2nd in 18 days 6 hours. It won or placed highly in many local races prior to a refurbishment in 1986 when a new mast was installed. Three Legs of Mann 111 was sold to several owners and in the late 1990’s was upgraded to a full cruiser and later had solar panels, batteries and EG a watermaker etc installed.

Each tri was constructed with Airex foam, e-glass and polyester or epoxy resin. Derek continued to improve his structures with better quality glass but still liked polyester for hull structures. Cross arms on some tris had epoxy resins.

These tris were fast and lasted well when sailed correctly. This design was the forerunner of Great Britain 4, a 53 footer sailed by Chay Blythe. The jpegs give the idea of both tris. Three Legs of Mann 11 first.

 

Sailboat magazine boat of the year for 2024 was the Dragonfly 40 designed and built by Jens Quorning family who have been building trimarans in southern Denmark since 1967. The Dragonfly 40 trimaran that has been around since 2020 but comes in many versions using the same basic hulls and swing wings. We will focus on the mid range Ultimate version but you can have the Touring, C Ultimate and C performance version.

The Ultimate version is 40.6 x 27.5 foot that can fold by swing wings to 13.2 foot. This tri is realistically able to fit into standard marina berths. The weight is 13,000 lbs and the maximum displacement is 20,100 lbs. The 62 foot carbon mast carries a 807 square foot mainsail, a 290 square foot self tacking jib, a 408 square foot roller furling genoa, a 860 square foot roller furling Code 0 and a 1,506 square foot gennaker. The length to beam on the floats is 16 to1 with a lot of buoyancy forward and low down. The draft ranges from 2.25 to 7.25 foot over the main hull based centreboard. The rudder is kickup and very high aspect ratio for good control. The engine is a 40 HP inboard.

If you want extra performance you can always order the C Performance version which is carbon foam and is the same basic shell dimensions but the weight is 10,750 lbs and the maximum displacement is 17,900 lbs. The carbon mast on the C Performance version is 73 foot high with a 10 to 11% larger mainsail, jib and genoa.

The Ultimate version can sail faster than windspeed across a wind range and the C Performance version is faster again, no wonder this tri comes with electric winches as standard on the higher end models. As one tester of the Ultimate version said: “With the gennaker up, at about 100 degrees true, we were going faster than the wind, and with winch pods on each side of the steering wheel, everything was as ergonomic as you could possibly imagine. The electric winches made it a cinch to furl and unfurl the headsails through the tacks and jibes, and the sails trimmed in perfectly every time.” The claimed peak speed of the Ultimate version is 24 knots, a number I have no doubts is possible.

The accommodation is based around 6 people with a large double under the cockpit, 2 single berths in the main cabin and a double forward. The galley and toilet are in the main cabin. The internal joinery is very well done. The cockpit is an ergonomic masterpiece showing years of experience in the design.

The build comes in 2 versions. A foam glass version with some carbon fibre (especially in the crossbeams and a full carbon foam epoxy version nused in the higher performance models. All come with carbon fibre masts. The real skill in this design is the swing wing cross beam structures. It is not just understanding the loads but far more importantly how to feed those point loads on the swing wing pins back into the structure without using heavy metal structures. Also, the floats as they fold forward are lowered 50 mm into the water to add additional stability in the folded mode.

A very interesting and fast cruising design that is well executed. Pity it costs over $1 million US on the water. The jpegs give the idea.

 

I see they recently announced a Dragonfly 36 model.

Interestingly the folding system is described as having been completely redesigned.

Curious to see what is different considering how long they have stuck with their current swing design.

 

The new DRAGONFLY 36 is a Performance Cruiser and basically a down sized Dragonfly 40 which has improved construction and design features such as EG wave-piercing main hull and float design. The wave piercing bows significantly boosts its performance by more buoyancy in the bow and also allowing for more smooth, safe and efficient sailing, when sailing in choppy waters or adverse weather conditions.

The DRAGONFLY 36 is 35.75 x 26.6 foot (the swing wings allow the beam to compress to 12.1 foot) with a weight of 10,000 lbs and a maximum displacement of 15,000 lbs. The standard 54 foot carbon mast carries a 655 square foot mainsail, a 215 square foot self tacking jib, a 414 square foot roller furling genoa, a 645 square foot Code 0 and a 1180 square foot gennaker. The draft is between 2.2 and 6.5 foot over the main hull based centreboard.

The DRAGONFLY SWING WING system – introduced 35 years ago – reduces the 8.12 m beam to 3.7 m. The DRAGONFLY 36 introduces for the first time an all-composite high-tech construction, making the DRAGONFLY SWING WING system simpler, lighter, stronger and easier to maintain. Quorning Boats in Denmark composite engineers the structural design using FEA calculations backed up with physical strength tests to ensure a stronger and homogeneous construction by also using more infusion and complex tooling for the composite parts. All this to optimize production, weight, strength, lifetime and maintenance and at the end also for lower costs. The DRAGONFLY 36 has been over 2 years in development.

The DRAGONFLY 36 will be available in two versions, both with carbon masts. The TOURING version with self-tacking jib system and the PERFORMANCE version with a taller rig and larger overlapping furling headsail. The PERFORMANCE version has a 60 foot carbon mast and about 20% more sail area on all sails. This would indicate the PERFORMANCE version would be faster on most points of sail than the standard version (my guess is about a knot faster on average) with the peak speed calculated by the company being 23 knots.

Step aboard the spacious cockpit featuring comfortable seating with all lines and sail-handling-gear lead towards the twin helm wheels. The interior features a fully equipped galley, multifunctional seat/berths in the main saloon along with a cabin area for the double berth under the cockpit. There is a toilet forward and a double berth in the bow.

The construction is foam glass probably in vinylester with strategic use of carbon fibre as required in beams and folding system as required. If Qourning have eliminated a lot of metal from the folding hinge joints etc this would be a significant advance in the folding systems.

The 36 is an advanced version of the 40 footer which has similar accommodation. Yet to be proven but I suspect the 40 footer will be slightly faster on the water due to its bigger rig, longer waterline and only slightly heavier weight in the C Performance version. But the 36 PERFORMANCE version could surprise the stand non carbon 40 footers.

The DRAGONFLY 36 will be release in 2025. The jpegs give the idea.