FT was a 35 foot long, 28 foot waterline by 26 foot beam. The sail area is 700 foot on a 47 foot mast. FT was sailed by David Palmer to 9th in 1974 OSTAR. The reason for the discussion is its crossbeams which were originally aluminium but were converted to fiberglass beams. The aluminium beams cracked at the intersect of the float. Kelsall had originally designed tube crossbeams but the required section was not available and Kelsall due to time pressures had to resort to aluminium U channels. When the problems arose Kelsall had the time to design and build a very effective set of fiberglass cross beams which solved the structural problems. The attached diagrams give a clear indication of the original and modified beams. A book called “The Atlantic Challenge The story of Trimaran FT” by David Palmer details the crossbeam story and other issues with the trimaran. The tri had a short waterline due to rules but used long floats to gain waterline length in strong winds so it had a pitching problem in light winds but it improved in stronger winds. As they developed the boat over time by strengthening rudders, reducing weight, improving the rig etc increased the performance of the boat but the real problem was the limitation of the OSTAR rules at that time which required the main hull shape to be distorted. The 2 basic learnings from the boat were don’t design to dumb rules and don’t compromise on major structural components. Design for the best available materials and wait for those materials, don’t compromise. The books cover is shown as it was first published in 1977, There are second hand versions of the book on the web.
The Boat Design & Boatbuilding Site
Multihull Structure Thoughts
- Thread starter oldmulti
- Start date
- Featured
kalymnos
New Member
Eric hi!i have been reading your posts. i wanted to ask your opinion if its possible. i want to build a 55 feet motor catamaran that can cruise at 50 knots from custom made composite panels made from either Divinycell H or SAN core foam and layers of carbon and kevlar . i have found the way to do this but wanted to know details of the best composition and correct pressures required to construct them. any advise? can i email you?thank you
Kalymnos. Please direct your questions to a professional naval architect. This is the second question I have had about 50 knot plus power catamarans of 50 plus feet. The design of these structures is not about guess work or maybe's. You are going to spend over $500,000 on a boat like this, $20,000 spent on the design is going to be a cheap investment. EG is the boat going to 50 knots in a river or 50 knots in open sea, If its open sea is it into 3 foot waves or 10 foot waves. Do you want to travel 100 miles or 1000 miles. The answer to each of these questions would alter the design and the structure of the catamaran. I am not a naval architect. I just have a database of mainly yacht structure and have spoken to some interesting people. Good luck.
catsketcher
Senior Member
I have the book on FT. What I never got was why she didn't have a rule cheater waterline like lots of the monos from that period like Laurie Davidsons Waverider and even the Farr 1004. With a canoe underbody leading to flat stern section that sat ABOVE the water at rest and was un measured as LWL. Our mono friends were much better at getting around rules than multi designers. I remember being told a story of the crew of Mooloolaba Fire Truck madly trying to get more weight up from to get the stern further out of the water for IOMR measurement. Again a crease would have reduced that problem. Tennant has canoe underbodies on his power cats so the idea is not slow. A full stern and longer sailing waterline would have markedly reduced pitch problems on FT. She would have been a much faster boat.
The photos show Waverider with her crease. Her stern sections are out of the water when stopped and being measured but are soon in the water when sailing. It seems pretty silly that Kelsall did not pick up what clever Kiwis were doing to make low rating but fast boats down under but maybe multi designers didn't look closely at monohulls. I remember at the time all of these long overhangs stuck out when I was sailing around the moorings. Nowadays we do things differently because we use different rules.
The photos show Waverider with her crease. Her stern sections are out of the water when stopped and being measured but are soon in the water when sailing. It seems pretty silly that Kelsall did not pick up what clever Kiwis were doing to make low rating but fast boats down under but maybe multi designers didn't look closely at monohulls. I remember at the time all of these long overhangs stuck out when I was sailing around the moorings. Nowadays we do things differently because we use different rules.
Attachments
Catsketcher. I spoke to the original owner of Moolahbar Fire Truck when it was called "The Club". He was trying to promote a new housing development in QLD and had minimal interest in the boat beyond it being different and it could win. Lex Nicol who designed the boat and his spar maker brother who built the boat were real racing enthusiasts and did everything to minimize ratings. The boat had a smaller sail plan than normal and yes everyone stood on the bow to try and lift the stern etc when being rated. There was another boat in the same series that had very suspicious water pipes leading into sealed float bow compartments. The boats main hull waterline appeared to change at rating time etc. Games were being played, but people were ignoring them as interstate rivalries were being played out. Bagatelle a 42 foot cat was designed as a rule cheater with exactly what you suggested with waverider. The boat was about 20% overweight when it launched and did not float on its "shorter" waterline. The boat was still fast but had a higher rating. In later boats people realized fast was more fun and designed for the best speed possible with only a passing interest in the rule.
Eric Tabarly’s Pen Duick 4 trimaran was years ahead of time. The tri was 67 x 35 foot displaced 19000 lbs and 1500 of sail area. It was taken over by Alain Colas who sailed it successfully around the world but went missing with the boat in an Atlantic race. Both Tabarly and Colas were national hero’s in France and their loss was mourned by the French nation. They are the reason the French love sponsored yacht racing. Penduick 4 / Manureva was the first big “racing” tri that was driven single handed across the Atlantic. The boats structure was more like an oil refinery than what we see in a modern trimaran. The main hull and floats were 4.5 mm aluminium plate with 5 stringers per side on the main hull that were 100 x 75 X 6 mm C channels. There are frames about every 1500 mm. There were 3 crossbeams of 2 aluminium top tubes and a bottom aluminium tube. The tubes are 125 mm diameter. The tubes are separated by aluminium tubes. The main sail aluminium main sheet traveller tracks are 300 mm deep x 18 mm thick and have an 18 mm thick top T section. The main mast was a 300 mm chord x 225 mm wide “wing of 4.5 mm aluminium pop riveted onto an internal web structure. The mizzen mast 250 x 125 mm. When Alain Colas took over the boat he added an addition forward crossbeam as cracks had developed in the original beams, added additional buoyancy to the main hull and floats and drilled out the traveller tracks with 200 mm holes. The masts were changed to standard mast sections. All this reduced weight but the boat was not really fast, just fast because of its size. Modern ORMA boats are 8000 lbs lighter and carry twice the sail area with beams of 60 foot versus 35 feet. Big modern tris are literally twice as fast in top speed and daily runs as Penduick 4 was.
Attachments
To those who aspire to 50 foot power catamarans that can do 50 knots. I had a guy write to me saying his 50 foot power cat was going to do 100 knots and he had calculated it would take a 2200 shaft horse power gas turbine to drive it, could I advise on the structure required to build it. No I can not help. To drive a 50 foot power cat with any form of accommodation at 50 knots you would require at least EG a MAN V8 of 1000 horsepower. The MAN V8 weighs 1800 KG and consumes over 240 litres hour in fuel. So if you want to go 500 miles you will need 2400 litres of fuel. Think about this, the engine alone cost $100,000 plus, each fuel top up to run 10 hours for a 50 knot boat will cost $4000 plus in Australia. So in fuel and engine alone you have already got 9000 lbs of weight. Any form of structure for a 50 foot power cat will weigh 45,000 lbs with all the running gear. These are big boats. Tennant cats from 50 to 60 feet could only peak at 28 knots and require 2 x 300 HP. The Yellow Cat by Teknicraft could run to 42 knots with 2 x 1050 hp engines and used 280 litres per hour of fuel. If you can afford a $4000 per day fuel bill you can afford an appropriate Naval Architecture to help. Also when it comes to high speed boats you will find that people cannot “live” in boats doing 40 plus knots. People break ankles and other bones as boats get thrown around. Offshore power boat racers in the 70 and 80’s used to stand up as they did 80 knots and broke ankles regularly. Big offshore global sailing racers have their crew sleep with feet forward and their sea boots on to stop breaking their ankles when they drive into a wave etc causing the crew to crash into bulkheads and these boats are only doing 30 and 40 knots. Please understand what you are aiming for. These fast power boats have to be designed very well by someone who really understands the forces involved. They literally can be bone breakers that can split apart when driven hard if not designed correctly.
kalymnos
New Member
thank you for the reply. yes i understand.i would get anyway an engineer and the concept is still in my mind and in some sketches. i will do this correctly with all the necessary settings required. i have been doing some reading and saw your comments and the duflex panels and thought to ask, it can perhaps be made from those to save time and even some money with correct engineering. it was as to whether you had any advise to add. thank you
A discussion on trimaran development. John Shuttleworth knows how to design high performance trimarans having designed them for over 30 years. We will look at the Dog Star 40 tri designed in 2001 versus the Shuttle 39 designed in 2018. The boats have similar length but the Dogstar is 36 foot wide, the Shuttle 39 is 32 foot wide. The Dogstar weighs 4500 lbs, the Shuttle 39 weighs 4900 lbs. The Dogstar carries 1240 square foot of basic sail , the Shuttle 39 1150 square foot of basic sail. Similar dimensions so what’s really different. Look at the main hull shape. The Shuttle 39 has a flatter main hull with a fuller stern section that have less rocker in the rear. There is no rudder or daggerboard in the main hull of the Shuttle 39. The Dogstar has more rounded hull sections and has a daggerboard and rudder in the main hull. The floats is where the main changes over the last 17 years have happened. The Dogstar has floats have fine sterns and no daggerboards. The floats of the Shuttle 39 have very full sterns with daggerboards and rudders. The design philosophy has changed over 17 years. The Dogstar was about the float being a stabiliser to the main hull with the main and float working in unison. The Shuttle 39 is about driving hard with the float acting as the control hull in the water and the mainhull coming along for the ride. This is also the reason the Shuttle 39 can have less beam. The boat is designed to sail on a float like a high performance catamaran sails on mainly one hull. Both boats are carbon fibre foam structures. Shuttleworth Design - Shuttle 39 Trimaran http://www.shuttleworthdesign.com/gallery.php?boat=shuttle39tri
Shuttle 39 dimensions. Length Overall 11.95 m, Beam 9.7 m, Displacment LT 2200 Kg Hull and deck Composite (Carbon/Foam), Main Sail 70 m2, Head Sail 35 m2, Mast Height 18.6m.
Shuttle 39 dimensions. Length Overall 11.95 m, Beam 9.7 m, Displacment LT 2200 Kg Hull and deck Composite (Carbon/Foam), Main Sail 70 m2, Head Sail 35 m2, Mast Height 18.6m.
Attachments
catsketcher
Senior Member
A tour of Morpheus, lots of black inside.
catsketcher
Senior Member
One of the things we have to remember when we look at older designs is to remember that there has been a huge improvement in materials and gear design and manufacture. Even though Pen Duick has much smaller sails than an ORMA 60 it could be much harder to sail than an ORMA, with lovely winches, roller bearing blocks, spectra, vectran, batten cars, carbon everything etc.
In fact I think that the materials scientists and gear designers are the unsung heroes of yacht design. I love reading the words of Nigel Irens and Kelsall but they could only develop designs that could be built in materials of the day. Witness even the difference between Dogstar and Morpheus. Some of that is probably due to improvements in carbon manufacture and better rudder/foil and mast and sail manufacture. A lighter rig allows finer forward sections, or you can increase power with the same righting moment and go for shapes with a higher prismatic and get higher top speed with the same heeling moment. Dogstar was built back when tris could catastrophically fail unless they had slightly forgiving hull shapes - witness the 2002 Rhut du Rhum when tris had carbon nomex and carbon skins. No rip stopping in their hull skin.
CNN.com - Fleet struggles in rough Rhum - Nov. 14, 2002 http://edition.cnn.com/2002/WORLD/sailing/11/14/rhum.damage/
In other words, even if Allegre, who designed Pen Duick, was transported forward in time, he couldn't have done a much better job with the materials that he had than Pen Duick. Making the sails much larger would have been too hard even for a superman like Tabarly. She was a great boat for her time, and for the state of material development at the time.
I sometimes like to think about the tri that I could design if I was taken back to 1964. It would be something similar to Toria, but with more rounded decks and cedar boards. Apart from that there is not much you could change with the materials available back then.
cheers
Phil
In fact I think that the materials scientists and gear designers are the unsung heroes of yacht design. I love reading the words of Nigel Irens and Kelsall but they could only develop designs that could be built in materials of the day. Witness even the difference between Dogstar and Morpheus. Some of that is probably due to improvements in carbon manufacture and better rudder/foil and mast and sail manufacture. A lighter rig allows finer forward sections, or you can increase power with the same righting moment and go for shapes with a higher prismatic and get higher top speed with the same heeling moment. Dogstar was built back when tris could catastrophically fail unless they had slightly forgiving hull shapes - witness the 2002 Rhut du Rhum when tris had carbon nomex and carbon skins. No rip stopping in their hull skin.
CNN.com - Fleet struggles in rough Rhum - Nov. 14, 2002 http://edition.cnn.com/2002/WORLD/sailing/11/14/rhum.damage/
In other words, even if Allegre, who designed Pen Duick, was transported forward in time, he couldn't have done a much better job with the materials that he had than Pen Duick. Making the sails much larger would have been too hard even for a superman like Tabarly. She was a great boat for her time, and for the state of material development at the time.
I sometimes like to think about the tri that I could design if I was taken back to 1964. It would be something similar to Toria, but with more rounded decks and cedar boards. Apart from that there is not much you could change with the materials available back then.
cheers
Phil
Tritium is a trimaran designed in 2002 that is 23.6 x 19.5 foot weighing 1600 lbs and displacing 2600 lbs. The tri carries 390 square foot of sail on a 32.5 foot mast with a single set of diamond spreaders. Tritium is made from 15 mm 80 Kg/m3 PVC foam, , with 2 x 300 g/m2 layers of E Glass bi-directional on either side of vinyl ester or epoxy resin. This layout exceeds the strength requirements from the American Bureau of Shipping. It could have been reduced, but I felt 600g/ m2 for the skin was a minimum for impact protection. The cross-beams are round tubes, mainly unidirectional glass with carbon fiber added in the most heavily loaded areas. The beams can be laminated over aluminium pipes or commercial PVC pipes used as a mould. Both beams are sitting on moulded recesses on the floats, and they are bolted through to the underlying bulkheads. At the main hull, they fit inside a moulded “sleeve” which runs through the whole breadth of the hull. The PDFs give more detail on the boat.
The tri had full stern float hulls with rudders attached. The main hull has no rudder. This boat is a competitor to a Farrier tri without the folding system but it appears to be a good boat.
The tri had full stern float hulls with rudders attached. The main hull has no rudder. This boat is a competitor to a Farrier tri without the folding system but it appears to be a good boat.
Attachments
Glues. Most people use an epoxy but some people try and use cheaper alternatives. John Welsford, a NZ mainly wooden boat designer, did some serious testing of glues using tension and shear measuring equipment on a variety of timbers. The results were interesting. West epoxy resin glue was the benchmark and rated at 100. Other glues depending on strength was either a lower number (weaker) or a higher number (stronger) than West epoxy resin glue. This is a cut down version of his results.
Polysulphides Usually sold in gun cartridge form and used as an adhesive sealant. Black or white sticky stuff for stopping leaks. Very sticky, used for windows, under fittings bolted to the deck, or where a seal needs to be made around a mast or such where it goes through the deck. Best as a sealant with limited adhesive properties. EG Sikaflex 291
Strength, about 45 /100.
Polyurethanes - foaming low density. Use very carefully where surface area to glue is very large in comparison to the force involved. Not recommend even though it’s very easy to apply.
Strength, about 55/10
Polyurethane, reinforced (construction glues used in house building). Similar in some ways to the Polysulphide glues but sold to fasten things together. Some are reinforced with microscopic fibres that act a little like rebar in concrete which makes it stronger. These glues are good for gluing plywood underlayment to house framing, and some will do that with wet wood. Great stuff, but not for structurally important joints in a wooden boat. Check the strength before you consider it.
Strength. 58/100
Polyester resin adhesive fillers Not intended for marine use. The samples tested came apart very easily and soaked up water.
Strength, 34/100
PVA The ordinary woodworkers white glue, not waterproof. It was the strongest glue tested. It does require good surface prep, and high clamping pressure. It is not suitable for boatbuilding, but is included for comparison and is the strongest commonly available glue around.
Strength, 122/100
Aliphatic PVA Very similar to ordinary white PVA but yellow in colour, not quite as strong. Not for boatbuilding.
Strength, 118/100
Cross linked PVA Requires a catalyst to be mixed with it, and is listed as “water resistant”. When mixed it is much like ordinary PVA in use, requiring accurate fits and high clamping pressures. Its very strong when used appropriately. Interior non-structural use only.
Strength, 118/100
Resorcinol Before epoxy glues became readily available Resorcinol (a Phenol formaldehyde variation) was the boatbuilding glue of choice. It is very strong, easy to use, has a reasonable pot life and cleans up with water. Its close sister product is used to make the waterproof plywood. Strong, easy to use but requires good close fits and a high clamping pressure to get the best result.
Strength, 112/100
UF EG Weldwood, Aerolite etc. is a water-resistant glue. Aerolite requires a powder to be mixed with water to make a jelly like paste, then an acid catalyst can be either mixed or applied to one piece with the resin on the other. Good fitting joints and a high clamping pressure is required. Clear glue line, easy to use and long pot life.
Strength, 106/100
EPOXY The most common glue in use for boatbuilding today. Gap filling needing only very low clamping pressures, and with the use of appropriate hardeners fairly tolerant of temperature and humidity. Most suppliers can supply resin, with measuring devices and additives that make epoxy a boatbuilding “system” that can provide high and low density fillers, coatings to preserve and densify the surface, and of course glues in various viscosities and configurations. Epoxy is the most versatile of all adhesives for wooden or plywood boatbuilding. It varies a lot from one manufacturer to another. Use product from a “name” company with a reputation to preserve.
Strength, 100/100
Polysulphides Usually sold in gun cartridge form and used as an adhesive sealant. Black or white sticky stuff for stopping leaks. Very sticky, used for windows, under fittings bolted to the deck, or where a seal needs to be made around a mast or such where it goes through the deck. Best as a sealant with limited adhesive properties. EG Sikaflex 291
Strength, about 45 /100.
Polyurethanes - foaming low density. Use very carefully where surface area to glue is very large in comparison to the force involved. Not recommend even though it’s very easy to apply.
Strength, about 55/10
Polyurethane, reinforced (construction glues used in house building). Similar in some ways to the Polysulphide glues but sold to fasten things together. Some are reinforced with microscopic fibres that act a little like rebar in concrete which makes it stronger. These glues are good for gluing plywood underlayment to house framing, and some will do that with wet wood. Great stuff, but not for structurally important joints in a wooden boat. Check the strength before you consider it.
Strength. 58/100
Polyester resin adhesive fillers Not intended for marine use. The samples tested came apart very easily and soaked up water.
Strength, 34/100
PVA The ordinary woodworkers white glue, not waterproof. It was the strongest glue tested. It does require good surface prep, and high clamping pressure. It is not suitable for boatbuilding, but is included for comparison and is the strongest commonly available glue around.
Strength, 122/100
Aliphatic PVA Very similar to ordinary white PVA but yellow in colour, not quite as strong. Not for boatbuilding.
Strength, 118/100
Cross linked PVA Requires a catalyst to be mixed with it, and is listed as “water resistant”. When mixed it is much like ordinary PVA in use, requiring accurate fits and high clamping pressures. Its very strong when used appropriately. Interior non-structural use only.
Strength, 118/100
Resorcinol Before epoxy glues became readily available Resorcinol (a Phenol formaldehyde variation) was the boatbuilding glue of choice. It is very strong, easy to use, has a reasonable pot life and cleans up with water. Its close sister product is used to make the waterproof plywood. Strong, easy to use but requires good close fits and a high clamping pressure to get the best result.
Strength, 112/100
UF EG Weldwood, Aerolite etc. is a water-resistant glue. Aerolite requires a powder to be mixed with water to make a jelly like paste, then an acid catalyst can be either mixed or applied to one piece with the resin on the other. Good fitting joints and a high clamping pressure is required. Clear glue line, easy to use and long pot life.
Strength, 106/100
EPOXY The most common glue in use for boatbuilding today. Gap filling needing only very low clamping pressures, and with the use of appropriate hardeners fairly tolerant of temperature and humidity. Most suppliers can supply resin, with measuring devices and additives that make epoxy a boatbuilding “system” that can provide high and low density fillers, coatings to preserve and densify the surface, and of course glues in various viscosities and configurations. Epoxy is the most versatile of all adhesives for wooden or plywood boatbuilding. It varies a lot from one manufacturer to another. Use product from a “name” company with a reputation to preserve.
Strength, 100/100
catsketcher
Senior Member
The killer is that you need close fits for all the strong glues apart from epoxy. What would I do without fillets, epoxy beds under bulkheads, and judicious gap filling where required?
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making any potentially dangerous or financial decision, always employ and consult appropriate professionals. Your circumstances or experience may be different.
When making any potentially dangerous or financial decision, always employ and consult appropriate professionals. Your circumstances or experience may be different.
Advertisement:
