Multihull Structure Thoughts

The following Tony Grainger TR 36 trimaran design has been featured before but more build jpegs have become available. The TR36 trimaran is aimed at a more economical performance trimaran than the TR 52 while still offering workable payload and cruising comfort. The tri is 36 x 27 foot with a weight of 6500 lbs for a “standard” build. There are all carbon build options which would be lighter. The 49 foot mast (from fixed aluminium to a rotating cardon fibre) carries a 505 square foot mainsail, a solent of 281 square foot, a code zero of 493 square foot and Gennaker of 1102 square foot. The length to beam at the waterline of the main hull is 10.2 to 1. The length to beam on the float hulls is 16 to 1. The draft is 5.5 foot over the daggerboard. The rudders are kickup on the floats.

The accommodation is a double forward and head. The main cabin contains a good galley, 2 narrow single berths and a small dinette. Aft can have a small double berth cabin and a reduced cockpit or a large cockpit. This tri could be seriously cruised by a couple but any more would be interesting after a week. I have cruised sailed a 36 foot tri with 3 to 4 people for a month and life got interesting.

The “standard” build is a plan and a pre cut duflex kit using e-glass and vinylester resins. Professional builders use from duflex or PVC foam cores and epoxy with e-glass or carbon fibre. The Waarschip Composites build has used duflex on the hulls with e-glass. PVC foam on decks with carbon fibre outside and some Kevlar inside. The cross arms main strength structure is in a carbon fibre box section with a PVC foam glass fairing. All chain plates are glass and/or carbon fibre depending on the rest of the build. Current Marine in South Africa did an all carbon foam build. Again you can build in many materials and Grainger will provide a plan option that suits. Please build in the material you understand as life will be a lot easier.

This tri’s performance is fast in any option but can be made faster with a lighter base build and taller rig. To give you an idea one builder claim is “The hull is also narrow enough to cut through the water before the trimaran starts to ‘fly’. 24 knots is achievable with 17 knots’ wind!” There is a video of Waarschip TR 36 sailing and it is very impressive. I could accept above 20 knots is possible.

This is a very good design that is worth consideration. The jpegs give an idea of the design and build. The first group is about the design and the second about the build.

 

Part 2 of TR 36 tri jpegs.

 

Samwise is a proa Mike Schacht started designing in 2007 Samwise is 24 x 12 foot proa. The lee hull is 24 x 1.7 foot, the windward hull is 20 x 2.6 foot. The weight would be guess 400 lbs with a probable displacement of about 750 lbs. The gunter schooner rig is on lee hull in Samwise version 1 and 2. The masts are 17 foot high above deck. The total sail area is 220 square foot. The length to beam of the windward hull is 12 to 1.

The interior is limited with a 3.5 foot headroom and enough room for a bunk and some storage.

The entire build was intended to be 2 foot wide plywood panels for the hull sides and hull bottoms. The cross beams are aluminium tubes. The proa could be disassembled for transport. This design is in the first 2 Jpegs. A nice simple proa that could be rapidly built out of 6 mm plywood bottoms and decks and 4 mm plywood sides with a minimum of fiberglass at the seams etc. The rig could use ex windsurfurer masts in initial trials.

In 2008 mike decided to upgrade the Samwise design converting it into a full Atlantic proa. Samwise is now 20 x 12 foot compressible to foot with sliding aluminium beams or folding beams. The windward hull is 20 x 2.9 foot. the leeward hull is 20 x 1.2 foot. Again the weight would be guess 400 lbs with a probable displacement of about 750 lbs. The length to beam on the windward hull is 9 to 1. The lee hull length to beam is 16 to 1. The improved gunter rig is now on the windward hull. The masts are 16 foot above deck with a total sail area of 180 square foot. Again, ex windsurfer masts may work.

The logic of this rework design was to place the rig in the windward hull solves several problems:

1. Aligns CE of sail and leeboard for proper balance. The force resultant of the rig now aligns with the leeboard, solving the weather helm, and making sail steering a much more likely proposition.

2. The windward hull is a larger box section, creating a sturdier base and more bury for the free-standing masts. Freeing the leeward hull of the need to carry the rig means it can be built lower and lighter.

3. Sail handling will be far more manageable with the crew within easy reach. Now I can shake the sail and pop a batten simply by grabbing the boom with my hand. Rigging, reefing and furling can all be done while standing in the cockpit.

Another significant change is the use of a moveable foil on the lee hull which will provide some lift and a moveable centre of lateral resistance for rig balance and some limited steering capability.

The build also has become more sophisticated with a multi panel windward hull bottom. Again plywood 6 and 4 mm would be the main building material. Aluminium cross beams.

The “accommodation” is basically a good cockpit with some storage available. A fun design for experimentation that could be relatively easily built. Well done Mike.

 

The Matera 50 performance cruising catamaran is designed and built by Steve Bull new Matera Yachts. Steve has designed many high performance moderately light monohulls and has a very good understanding of hull shape and forms. The Matera 50 is 51.5 x 25.25 foot with a weight 14,800 lbs and a displacement 19,000 lbs. The 70 foot carbon fibre mast carries a 936 square foot mainsail, 410 square foot jib, 860 square foot code 0 and a 1797 square foot gennaker. The length to beam on the hulls is about 12 to 1 with and underwing clearance of 2.8 to 3 foot depending on load. There are hull based daggerboards. It has two 40 HP engines as standard. With numbers like this this cat will perform very well being capable of 20 knot plus peak speeds and 300 mile days under good conditions.

Configured with three or four double cabins, with en suite options as required, the design offers bi-fold doors open up the galley and saloon to the cockpit for alfresco dining. The main bridge deck cabin has a galley with ample space for appliances and storage to port and starboard. The interior is completely open aft, while remaining protected by a rigid bimini that is enveloping. The cockpit area has a large dinette and 2 day beds. At anchor, with the tender launched, the cockpit aft beam folds down, further enhancing this living area. Blinds can enclose the cockpit, offering shelter or privacy when desired.

The forward cockpit is dedicated to sailing manoeuvres allowing the helmsman full visibility and control. Included here are all sail controls, instruments, auto-helm etc., enabling confident single-handed sailing. I hope the builder offers some windscreen protection as going to windward to fast reaching generally throws a lot of wind and spray into an unprotected helmsman face. Chris Whites Atlantic series has the helm position inside for a reason.

The structure specifies a vacuumed or infused carbon / foam composite producing a high modulus, light, responsive structure. Vertical carbon daggerboards further enhance up and downwind performance. Carbon spars and a stacker boom completes the package. Steve Bull has worked on 5 America’s Cup campaigns and really understands carbon fibre composites. Result is a light stiff cat structure.

This is/will be a real performance cat, The jpegs give the idea. The web address is: https://www.materayachts.com/about

 

The Radikal T26 trimaran was designed by Philippe Roulin in about 2013 and finally launched in early 2015. The trimaran is 26 x 18.7 foot over the hulls and 29.5 foot with prodder and rudder. The trimaran can fold to 8.3 foot for trailering. The weight is 1350 lbs and a displacement of 2420 lbs. The 39.4 foot standard mast is aluminium, but the optional rotating carbon fibre mast carries a 333 square foot mainsail, 226 square foot jib, a 408 square foot gennaker and a 527 square foot asymmetric spinnaker. The flat length is 26 foot. The floats have C curved daggerboards that draw 3 .6 foot when down. The kickup rudder is on the central hull. Main hull length to beam at the waterline is 8.1 to 1. Float length to beam 15.5 to 1. The outboard is 6 HP.

The accommodation is 2 single berths/seats 1.6 foot wide and a “double” berth forward, 3.2 foot wide at the head and 2 foot wide at the base of the berth with space for a small galley and porta potti. The headroom is 4.6 foot. Average accommodation for this type if trimaran.

The construction varies according to your requirements. It can be infused glass/polyester hull and decks with epoxy carbon glass in cross beams, foils and mast. You can also have glass epoxy in the hulls or an all carbon fibre boat as an option. The glass sandwich central shell is infused with carbon epoxy infusion reinforcements, the floats are sandwich epoxy glass with carbon fibre reinforcements all infused. The epoxy carbon sandwich curved foils are prepeg and cooked at 80 degree centigrade. The mast is 2 part epoxy solid carbon fibre cooked at 80 degree centigrade.

The performance? To quote 2 testers “Here we are going along at 12 knots, with a wind on the beam which is 10 at most”. “With a bit more wind and a bit more chop, the spray was starting to come over: there was already 15 to 17 knots of wind. The GPS hit 17.3 knots.” At 18 knots true wind we were wondering about putting a reef in. The big surprise is that we’re not too wet, given the speeds we’ve been doing… Our average speed was close to 12 knots, since we were making 10 knots at 40° to the true wind.” “The record to beat? 22.3 knots peak speed.” This is a very fast trimaran that appears to be well designed and has a very effective set of C foils that assist in stability and control.

Now my problem is some of the advertised weight numbers. A Seacart 26 which is an open cockpit tri of very similar dimensions but has less hull surface area and no accommodation, weighs 1540 lbs. The build is an infused epoxy glass with carbon fibre crossbeams and reinforcements. The rig is very similar. The Seacart numbers are real figures from being weighed for racing. Either the Radikal T26 is built with an ultra light carbon fibre structure or the Radikal T26 built weight was weighed without the rig, deck gear etc. I suspect an on the water weight of about 1700 lbs for a light weight build. The polyester e-glass version of the Radikal T26 with an aluminium mast would probably weigh 200 to 300 lbs more which means an actual boat weight of about 2000 lbs ready to sail.

The Radikal T26 is a seriously fast performance minimal cruiser. The sort of boat that the majority of sailors could really enjoy. A very good design. The jpegs give the idea.

 

I posted some questions about the Radikal 26 on Sailing Anarchy, hoping someone had experience with it. You found lots more info than I had including photos of it folded. Thanks. My main interest is how it folds. It has Farrier-like struts, but no secondary links to control folding. I wanted to know how they folded it in and out. My guess is that it is done with a few people to help hold the hull until the bolts are in. The struts on the Radikal hold the ama's up when the rig isn't up, but the water stays take the sailing loads. I've been sketching a little cruising tri and this folding method intrigues me.
I've been looking through previous pages of this thread looking for inspiration. Thanks again.

 

I wondered about the struts on the Radikal 26 as well Russell Brown. Either they are much wider than they appear, or as you suggested folding and unfolding is a two person task, and probably not something one should try on water. I’m guessing the foils have to be removed and carefully stowed somewhere too.

 

You can contact an owner, Laurent Garnier, he has a blog on his Radikal t26 named Folie 11, where he proposes the contact : lgarnier11@gmail.com
Folie 11 : trimaran habitable Radikal T26 : 2018 https://folie11.blogspot.com/2018/

 

Laurent Garnier put "Not unfolding on water" on his blog.

 

Russell, trimaran folding systems are a difficult topic. I cannot add any real value beyond a general discussion and a request to others to add any thoughts.

Farriers initial patent was very good and when the patent expired a lot of designers just used the approach. But in the patent period many different approaches were used. So, we will go through a few of the choices.

If the tri design is small enough many just used a demountable system. Full length light aluminium tubes as used on EG Sardine Run 18 foot trimaran fixed by bolts and waterstays. If the tri is light enough with very light floats and you only trail occasionally fine. A fancy trailer with sliding beams to support the floats will allow up to a 20 foot beam. The smarts required are about trampoline attachments, mast raising etc to minimise assembly time. The trailing problem is if the floats or main hull move out of alignment while being trailed then a fir bit of person power is required.

Next is the sliding beam approach used by EG Kurt Hughes or the L7 trimarans. This keep the hulls in alignment while trailing and in theory should be easy to expand or contract but the sliding beams bind unless the hulls are pulled apart perfectly parallel. Simpler to set up as all the tramps etc remain attached.

The folding fore or aft beam approach used by EG Dragonfly trimaran works very well if it is WELL engineered. Most people underestimate the loads on the joins when the floats are partially or full folded. I watch a small armature tri launch with aft folding floats and beams that twisted a support bracket on the main hull when the floats hit the water first. If possible, fully set up the tri before the launch with this approach. The cheap simple version of this system is the Brown, Marples 20, 24, DC3 trimaran timber aft folders.

The simplest, cheapest folding system I have seen is the Frank Smoot Slingshot DIY tris (Duckworks plans) aft folding beam approach. It works well on smaller day tris but would need good engineering on ant thing above about 20 foot.

Another folding system is the half beam fold lifting the floats vertically up and fold onto the deck. I have seen this approach work on tris up to about 23 foot. It has 2 problems. The total beam when unfolded is limited to about 16 foot. And the weight of the float has to be light. If the float weight is not light it requires some sort of winching arrangement to lift the floats up into the trailing position. Structurally this system is OK but limited in the size of tri it can be used on. The alternative to this approach is the fold down float system used by EG the Cross 18 foot day tri. This approach is simple structurally sound and easy to do. Downside is limited beam EG 14 would be about maximum.

Now the variations of vertically folding cross beams. The Farrier design is superb and if you can afford the time and engineering to do the cross beams, metal work and support framing you will get a good result. The problem is it takes time, money, accuracy and very good design. The huge advantage of the Farrier system is it controls the float movement throughout the folding and unfolding process. A very famous Australian non Farrier tri launched with a Farrier folding system. It did not fully fold. The floats went to low in the water in the folding process trying to lift the mainhull out. It required the floats to be winched in to work before the cross arms went through an expensive rework.

Team Scarab trimarans have a variation on the Farrier folding system that is as complete as the Farrier system but a little more home buildable. There plans are cheap at $150 Australian.

Next comes the single control arm folding systems like the Radikal T 26, Marples 26 etc. They work, but their major limitation is the system does have full control of the float during the fold process. It either require person power on land to lift/ push the floats into position. On water the situation becomes a little dance trying not to get a beam suddenly locking down on your toes as it snaps into place or the tri rolling over because the float and beam are hanging free on the end of a free floating beam “waterstay”.

Folks, has anyone an idea of any other trimaran folding systems that have been used. Real world examples and jpegs would help. The above is just what I am aware of, the Farrier is the best but not simple, the Dragonfly works well, the Smoot Slingshot DIY tris is the cheap simple version, but the lightest strongest version is a full length eg carbon fibre tube with waterstay that is used in the assembly of the tri with a suitable folding trailer. Unfortunately, the assembly path limits the tris trialability.

Some jpegs below.

 

Very comprehensive roundup. I would add that Ed Horstman has a swing wing 26' for home builders, and he has another folding trimaran. The Tristar 24 uses the up and over system. This allows him to retain his trademark doubles in the connection structure (2 doubles!), enclosed head forward and good galley/dinette amidships all in a trailerable 24' trimaran!

Ed Horstman Designs http://www.edhorstmanmultihulldesigns.com/triplans/tri24.php

http://www.edhorstmanmultihulldesigns.com/pdf/Trimaran24 6 view specs.pdf

A remarkable package as far as accommodations are concerned.

 

Russell John Patterson had a segmented system on the 21 foot little tri.

Facebook https://www.facebook.com/tomh151/media_set?set=a.1402421996720242.1073741831.100008573640993&type=3

 

As an owner of a 1982 Australian built Haines Hunter Ian Farrier designed Tramp, the first mass production boat to use Farrier’s folding system, I can attest to its excellent design.

Not only does it do what it was designed to do, easily fold and unfold on trailer or water single hand, but many early systems like mine have worked flawlessly without any maintenance for nearly 40 years!

When I first purchased my boat, I figured no one had ever serviced the system and I was concerned as the previous owner had recently painted the beams and hinges causing paint build up at the pivots, so I removed my floats and replaced the top axle mounting bolts, cleaned and greased the bushings and other pivot points, and reassembled. I highly recommend this service to anyone with an older Farrier system to prevent any binding which could potentially cause damage to the hull at mounting points, and to ensure another 40 years of flawless service.

Interestingly Farrier continued to work at refining the design. He was never happy with the windage of the beams when trailering and worked hard to reduce the amount of beam height when closed on trailer. If you compare the height of a Tramp’s beams when folded, which has a beam width of almost 15’, with the height of a new Farrier F-22 which has a beam width of about 18’, you can what he was able to accomplish.

 

Thanks all for the treasure trove of information. I guess I had seen most of what you posted, Oldmulti, but your commentary is quite helpful. Of those, the Cattri system appeals the most. The issue with the Farrier system for me is having to build four pockets that notch well into the hull side to attach the inboard ends of the secondary links. I like the idea of the Radikal system, which uses water stays and has the struts only provide strength for holding the ama's up when the mast is down and a folding axis, but that system for me would require raising the mast first and using a halyard & bridle to the ama and some kind of a pull-down at the inboard ends. I did finally figure out a decent way to model the folding linkages. I don't do CAD, so old school. It was good to be reminded of John Pattison's 21 footer. It's hard to make a high-volume boat look good, but he did. I'm drawing something around 29 feet, but also high-volume as it will be for cruising. Not quite a pregnant guppy, but I have to be able to stand up and cook and have comfortable seating. I will post drawings of the boat here when I get far enough along. I don't really have enough experience in small trimarans to be designing one, so input is good.

 

Sounds interesting Russell, 2c worth
Look at Greg Lyn’s Girlfriend and how he has used the chine lines to create flare and volume, now fatten till useful.
Greg Lynn YACHT https://m.facebook.com/greglynnyacht/photos/a.190062071176729/365230966993171/?type=3&source=54