Multihull Structure Thoughts

More about Beowulf:
https://setsail.com/multihull-histo...qHn9XQM_dtQ7mmQDDjQHisLNkaOA4tMLQXxy9JiGvG2C4

 

This is the Dashew article I was thinking of... SetSail FPB » Blog Archive » Steering Clear of Trouble: Our Search for Cruising Perfection http://setsail.com/steering-clear-of-trouble-our-search-for-cruising-perfection/

 

A simple one for those who aspire to have a floating house that can provide a view. The design is done by Naviculus. The NAVCAT CANAL is designed to fit into the French canal system and travel extensively over France or other countries canals, rivers, lakes or sheltered bays. The NAVCAT CANAL is 32.5 x 14.75 foot (or 13.2 foot on the PDF study plan below) and displaces from 7,000 to 10,000 lbs depending on the materials you use and the level of fit out. The hull draft is 1.6 foot. The hull length to beam is 11.2 to 1. The hull shape is relatively simple with a quarter circle shape and a flat side. The propulsion system is 10.8 kWh Propulsion Torqeedo twin cruise with 4 Batteries 4 x 26-104(lithium) which will provide a range 60km@5km/h - 12 hours. The batteries are intended to be topped up with shore power but the roof area can have solar panels on it to provide some limited independence.

The accommodation is vast for this size of cat. Two double berth genuine spacious cabins forward. An independent toilet and shower area followed by a full galley, dinette and entertainment lounge area. There is an aft cockpit, forward deck area and rooftop standing area. The steering position is inside forward but has limited visibility aft.

The construction material (marine plywood/softwood stringers keels, frames etc) and method (stitch & glue fiberglass) is simple allowing low cost & ease of construction. The designs is available with all construction plans, or kits can be ordered with all hull frames and skin plates pre-cut. The plans cost 500 euro negotiable if any modifications are required.

The PDF study plan attached give the layout and concept.

 

Thanks for the Harry information. The boat described was a proof of concept for the build method, rig, beams and boat type generally. This was in the days when all the 'experts' were 100% certain that the harryproa/weight to windward proa concept was flawed and would not sail or shunt. And were not shy about telling me so. As I wasn't sure what would work and what would need changing, it was very rough and ready.
The bendy ply was great but a mould farm if not well coated with epoxy. I did not try compounding it so the joins at the ends were not fair. Looked ordinary, but not a big deal performance wise.
I did not do many miles in it, as once I knew that it worked, I built longer lasting versions. Not sure where it ended up, although I think the lee hull became decks for a catamaran.
It is interesting how much has changed and how much stayed the same. eg the cargo proa has similar concept beams, and it and all the Harryproas still have rockerless hulls, oversize external rudders at ~25 and 75% of the length (now stronger and sleeker), n0 daggerboards and the crew and accommodation in the windward hull. The overall aim is still the lightest, easiest to build, lowest cost boat I can envisage.

The rigs have changed from unstayed ballestrons to unstayed cat schooners and the looks improved once we decided there was more to it than brute simplicity. The build method has definitely changed. Still easy and fast, but we now use low maintenance infused foam and glass rather than high maintenance, expensive and heavy plywood.

It looks like I am delivering a boat to Sydney next week. Are you available for a cup of coffee and a chat?

Rob

 

Rob. Thanks for the offer of a coffee but I am travelling at the moment. We will meet one day as I have relatives in QLD that need a visit.

 

Wayne Barrett is an Australian designer of the M60, M80 tri’s designed the M90. The M90 is 30 x 23 foot with a weight of 4,000 lbs and a displacement of 4,800 lbs. The 42.7 foot aluminium mast supported by Dyneema standing rigging. The fractional rig carries a 406 square top mainsail, a 200 square foot self tacking furling jib and a 516 square foot Gennaker. The draft varies from 1.5 to 5 foot with the main hull daggerboard. The rudders are kickup on the floats. The outboard is 10 HP. The outboard has a good fold up and storage system.

The accommodation is basically 4 single berths, a small galley, a porta potti under the forward bunk and storage in the cockpit and in the floats.

Now we will talk about the standard M90 versus the build I will feature here. The standard M90 is a plywood chine build with 9 mm plywood skins on the main hull. The floats are chine as well. The cross beams are farrier type folders. There is a foam carbon fibre “chine” version built as well. The tri featured here was built by very experienced Dutch builder who did a strip plank cedar and epoxy round bilge main hull reinforced with glass rovings and where necessary carbon strips and PVC foam stiffeners. The chine Bruynzeel plywood floats have some WRC decks and the tri has fixed crossbeams. The beams have a timber box frame with 16 layers of 300 gsm unidirectional carbon fibre 20 cm wide on the top flange with 14 layers of 300 gsm unidirectional carbon fibre 20 cm wide on the bottom flange. The cross beam leading edges are strip plank cedar and epoxy. The cabin and decks are Bruynzeel plywood with timber framing and deck stringers with some WRC strip plank.

The performance of this tri is very good on all points of sail with good sails and is capable of matching similar sized farrier tri’s. The jpegs give the idea.

 

Further M90 trimaran jpegs mainly of the build.

 

That tri is for sale right now and the listing has a few more pictures of the little details. The page takes a bit to fully load all of the images and also contains a link to a news article with more photos of the construction near the bottom of the page. I think she's a very pretty tri for a home-build, but then both her builder and designer are very experienced so there you go.

 

What a fine piece of work that Learn To Fly is, wonderfully intelligent use of materials.
Art and design.

 

A short one about hydrofoils. The following information will be a lot of reading but will give you the basics of Hydrofoil Sailing evolution and possible design options. The AYRS 074 book is 16 meg and describes a variety of cats and tri using simple technology to fly. The cover shows Willaw, a hydrofoil tri that sailed from USA to New Zealand 50 years ago. The cover shoot below does not lead to the book use this link: https://www.ayrs.org/repository/AYRS074.all_A5.pdf


Tom Speers (involved in several AC wing sail designs) did a concept design similar to Willaw and finally if it loaded down below Hydrofoil Sailing the 1972 book PDF that describes many of the issues that are still relevant today.

Hydrofoil Sailing can also be found by putting “Hydrofoil Sailing ALAN J. ALEXANDER, BSc, MSc, PhD, CEng, AFRAeS, MIMechE JAMES L. GROGONO, MB,FRCS DONALD J. NIGG, BSEE,MBA” into google and an image should come up leading you to the PDF. Have fun.

 

A design for the zero-emissions transport has been done for The Fair Winds Trading Company, based in Scotland who initially plan to use a vessel, called PraoCargo, to transport goods between West Africa and Scotland. Their long-term vision is to assist Small Island Developing States (SIDS) and coastal communities in the least developed countries in acquiring their own ships and establishing their own trade routes.

A 12 metre model of the PraoCargo ship, which has been designed and built by naval architect, Alain Guillard, underwent sea trials off Brittany, France in 2015. The model pacific proa is 40 x 21 foot and weighs 2,000 lbs and displaces 8,000 lbs. The crab claw rig carries 430 square foot of sail. The proa has 2 rudders and no keel foil. The windward hull is 19.7 foot long and pivots independently of the main hull. The proa was a demonstration prototype so only contained 1 berth and not much else. The prototype was built from plywood, timber and epoxy. The shell is covered with glass and epoxy. The prototype reached a maximum speed of 16 knots.

The full size PraoCargo is intended to be 197 foot long. The beam would be about 80 foot. The displacement (estimate) over 500,000 lbs (223 tons). The 160 foot high wing mast with large roller furling jibs will be powerful enough to move the vessel but it will be very interesting to see how they shunt the proa and move the rig end to end. Also, in one diagram you will see the proa at a dockside. The mast is lying beside the hull to allow the loading and unloading of product, again an interesting concept. The rig size is not specified. If my guesstimate on displacement is realistic the vessel would be able to carry over 100 tons of product. The draft of the vessel would be between 13 and 19 foot depending on the position of the rudders and the load on the proa. The windward float again is on a pivot and is allowed to work over seas independently from the main hull. The vessel is designed with a maximum speed of 25 knots, and an average speed of 13 knots under sail, backed up with an electric motor drive system.

The Fair Winds Trading Company hopes the PraoCargo ship will be used to transport goods from fragile coastal regions, where it is difficult to establish port facilities. The company’s founder, Madadh MacLaine said: “Our aim is, not only to achieve a zero negative impact method of sea transport, but also to demonstrate to commercial shipping and the market that this is not only do-able but desirable.” Shipping may be the most energy-efficient mode of cargo transport, but small ships transporting less than 4% of world cargo contribute 26% of all shipping emissions. Larger ships are making waterborne transport less expensive but at what cost? Most developing countries don’t have the infrastructure to handle these “sea giants” and are thus cut out of the world trade market. Shipping in general is responsible for 3.3 to 4.5% of all CO2, 14 to 15% of global NOx and l6% of global SOx emissions. This boat can handle rough oceanic weather, is extremely rapid and highly manoeuvrable. Its shallow draft and double hulls allow it to navigate shallow river estuaries and to beach close to where goods are produced. This means we can access goods even in places where there are no roads.

It looks like The Fairwinds Trading company did not go ahead with the full size PraoCargo. Pity, it would have been a spectacular vessel. Limited jpegs, sorry.

 

The Largyalo 65' is a development of the Wharram Pahi 63’, it is heavier, more liveable, its cabin roofs are higher, corresponding to the requirements for an expedition boat. The cat is 65 x 32.8 foot with a weight of 34,000 lbs. The wing sail schooner masts are 52.8 foot and carry a total sail area of 1,430 square foot. The draft is between 3 and 6.5 foot with twin centre boards per hull. The engines are electric, 2 x 10kW/220V + 1 x 10kW as a bow thruster. Solar panel area comprises of 16 square metres on the cabin roofs, plus an additional 27 square metres of flexible mounted panels. Two 600w wind generators also feed the batteries which are lithium/polymer, 3800A/h, 3000 cycles (320 kg).

The standard Pahi 63’ is 2 foot shorter, has 4 foot less beam and has a total displacement of 28,000 lbs, 6000 lbs lighter than the Largyalo 65'. The sail area is the same. LARGYALO is slower than the Pahi 63’ from which it is derived. LARGYALO at half loads sails at between 8 and 13 knots but the cat is able to cover 160 to 200 miles a day on ocean crossings.

As LARGYALO is an expedition ship intended to sail the around the world in 1000 days the “accommodation” is interesting. The cat has 16 berths, 4 toilet/showers, a full galley with a 340 litre fridge, a 90 litre freezer and an induction cooker. The water maker tops up the 400 litre water tanks. The deck areas are large with the 4 deck pod cabins holding navigation, double berth cabins and the galley.

The interesting part of LARGYALO is what it took to build it. The basic Pahi 63 is a plywood timber structure done in West resin type systems and is conceived to be “home built” in 5000 hours by Wharram. LARGYALO used includes 208 sheets of 8 x 4 foot plywood, 12 cubic meters (431 cubic feet) of solid wood, 1.5 tons (3360 lbs) of epoxy and 1000 square metres of fiberglass. Also, you have to add 150 litres of paint, 1500 metres (4,950 foot) of rope etc. But the absolute truth is told by the 25,000 hours of work to build LARGYALO. This is 5 times longer than Wharram’s estimate to build a Pahi 63. Please understand that designer build time estimates should be taken with a very big grain of salt.

Just because a design “looks” simple does not mean it is simple, cheap or fast to build. An aluminium or flat panel foam glass cat of the same size would take the same or less time to build. Please investigate all options and cost them out, you may be very surprised as to what is possible and the effort it takes.

The jpegs give an idea of a Pahi 63 and LARGYALO sailing etc.

 

That outboard deployment and stowage system on the M90 is pretty slick. Slightly offset it looks to be to allow stepping up into the cockpit. And having that motor head tilt and slide up closer to the rear crossbeam means it won’t get beat up too bad or add unnecessary weight like it would if hanging off the back.

The motor on my Tri uses two verticals rails off the side of the transom scoop to lower the outboard into the water, and uses a 4:1 purchase and a winch for raising, but I’m thinking about modifying it with an acme screw and using an electric drill instead.

 

A story about a pacific proa initially named P52 that was renamed “Swordfish”. The proa was initially designed, built and sailed by Skip Johnson then sold onto a second owner. Swordfish is 22 x 10.7 foot but can be compressed to 8 foot wide for trailering. The displacement is unknown, the initial mast, a wooden lightweight cedar hollow birdmouth spar that weighed 16 lbs, was about 21 foot long but broke the top 6 foot off during one event leaving a 15 foot mast which worked just as well for the crabclaw sail. The sail area varied according to what was available and what was temporarily made available. The sails ranged from 160 square foot very rarely used, 116 square foot the most used and a 48 square foot polytarp sail used in high winds. The steering system varied over time. Initially it was a long oar mounted in a yoke. The first oar broke as the blade area was to large. A second smaller bladed oar worked much better but was still difficult to use and then finally a kickup daggerboard steering rudder were mounted on pintles at either end was constructed.

We will deal with the proa’s performance. In very light winds it could travel at 4 knots with no one steering tracking straight. Under its 116 square foot rig it could achieve 15 knots in reaching and running conditions. When the proa broke its mast and was forced to use its 48 square foot polytarp sail it achieved 20 knots in 6 foot seas reaching. Hmm. The owner then found that the proa could achieve very good speeds across a range of winds under small sail areas. The proa could go upwind well but the cut and condition of the sails dictated how well it went. When the rig was properly set up. The first owner quote was “Hitting 12-14 mph regularly with 48 S.F. of polytarp sail is still hard to believe, never mind the 20+ mph on less area on a shorter mast” The surprise to the owner was how little sail area was needed to drive the proa in all conditions.

The proa has 2 single berths with a central cockpit. The cockpit can be covered with a 6 x 5 foot dome tent to provide a sheltered spot to do cooking or use a portapotti.

Now we get to the original name of P52 which I thought related to length. The reality it may be more related to the thickness of the 5.2 mm underlay plywood used in its construction. The original owner said it is probably not the best choice for building. The main hull is a box dory flat bottom shape with minimal internal bulkheads and framing. The deck needed reinforcement after launching. The float again is a V bottom 5.2 mm plywood structure that had to be reinforced after initial sailing. The retractable cross arms were stiff enough for sailing but “the folding system worked well enough when extended and also when supported on the trailer (4500 miles worth) but was fragile in torsion while folded”. Again, a modification was required.

This is an interesting design for the education it provided to its original owner as he developed the proa. His main conclusion was the need to understand how to balance the rig position, steering requirements and float design. If it all came together well the proa sailed very well on minimal sail area. If these forces could not be balanced things became difficult and occasionally broke. Also there are some interesting ideas in this design like the sliding system for rope controls on the outer side of the main hull which may have assisted shunting.

The jpegs give some idea. The first 2 are of the original tall mast and steering oar version of P52.

 

I believe that the sliding track with all the lines is a clever, inexpensive adaptation of the "tack-track" used on some proa designs such as the Deltro Beachsailor proa (see the image below). I've always throught that the idea was quite clever and I've worked it in to my own 32ft proa design (inspired Sidecar over on SA) which also uses a track to guide the tack of it's sizable crab claw sail (somewhat visible along the leeward gunwale of the vaka)