Boat – Page 2 – rush cruising

Tender Choice

One of the fundamental benefits we see from a cat is the ability to carry a capable, easily launched tender. For us, that means:

Tough rigid hull
Big enough to carry up to 6 people
Reasonably dry ride
Able to plane and cover a few miles quickly

The balancing factor is weight. We’d also like our tender to be:

Light enough to pull up a beach
Light as possible to minimise effect on the mothership when in the davits

Aluminium hulled RIBs tend to be the most popular choice for multihull tenders but a more recent breed of carbon composite boats is gaining popularity, so we had a good look at some options. Here’s a comparison table:

Model	Material	Weight	Payload
3D Tender – Ultralight 330	Aluminium / PVC or Hypalon	41kg	550kg
Highfield – Ultralight 310	Aluminium / PVC or Hypalon	50kg	585kg
Highfield – Ultralight 340	Aluminium / PVC or Hypalon	53kg	663kg
AB – Lammina 10AL 319	Aluminium / Hypalon	53kg

OC 350	GRP – glass or carbon	54 / 44kg	448kg
AST 340	GRP – glass & carbon	39kg	480kg

I didn’t know the 3D Tender range but a mate who has a 3D recommended them. Their Ultralight 330 model gives the size and payload we need, yet it’s almost 20% lighter than the most comparable Highfield (which is admittedly wider but shorter, with a slightly higher payload). In fact, the 3D is only 2kg heavier than the lightest carbon tender and has a higher payload, tough hull (although the inflatable tubes are more vulnerable) and a relatively dry ride. http://www.3dtender.com

It’s also the lowest price of all the above options. I’m still wondering what the catch will be… but we’ve bought one (now called Derek in a nod to his stowage location) and it looks well made to me.

3d tender, CM46, CM52, Current Marine, performance cruising catamaran, catamaran tender — 3D Tender – Ultralight 330

Derek doesn’t have a double, flat floor (maybe we’ll add a light composite floorboard to keep kit above any accumulated bilge water) but he does have a lockable bow locker which will be great for fuel, anchor and any other small stuff left aboard while ashore. We’ll fit fold-down transom wheels to make it easier to pull him up a hard beach.

Our controversial decision is probably the tube material and I’m braced to be told I’ve been daft. We’ve gone for Valmorel PVC rather their Hypalon option because Hypalon seams have to be glued, whereas PVC seams can be welded. Word is that glued seams are often the first thing to fail. Valmorel PVC is reputed to be a big step forward from older PVCs – apparently it doesn’t go sticky and break down in the sun.

We’ve just made a tubes cover (for some reason known as dinghy “chaps” – why?!) and, to be honest, are rather proud.

A few years ago Amanda bought a Sailrite sewing machine, made an all over sun-protection cover for our Pogo, Rush and has recently been working down the size range but up the complexity scale. Chaps are (hopefully) about as curvy and tricky as boat cover making gets! Seems cover making is another unexpected upside to recent travel restrictions, a boat in build and time at home!

Anyway, we’ll also make a full top cover to use when Derek is in the davits so, with that and the chaps, the PVC tubes should see little direct sun and will hopefully prove the right choice…

There isn’t a 3D Tender dealer in South Africa, so we bought Derek from Ocean First Marine in the UK and we’ll ship him, with a load of other gear, out to CM.

Outboard motor

I’ve been mulling over outboard choice. It’s tempting to buy a 15hp 2-stroke in South Africa, where they’re still available. It would be 25% (11kg) lighter than the equivalent 4-stroke and simpler to service. But 2-strokes are a bit louder and less “clean”. That said, I gather modern 2-strokes are better than older designs on both fronts so am hoping the differences will not be meaningful and am leaning that way.

The Suzuki 15hp is the lightest on the market at 33kg, using the same platform as their 9.9hp. We have a larger 4-stroke Suzuki outboard on a 6m RIB at home which has proved extremely reliable so we’re happy to stick with the brand. And they’re black which is, of course, crucial to the decision / colour scheme. The plan is to order the outboard from a dealer close to CM and Julian has offered negotiate a local’s rate deal.

Safety Technology

In addition to the widely adopted electronic safety equipment, we’re planning to fit two less well known “ultimate safety” systems which, like a life raft, will probably never be needed. Each of them adds roughly 1% to the cost of the boat – not insignificant but, on the other hand, surely worth it if they add peace of mind in exceptional circumstances.

Sertec CMCE Lightning Strike Prevention

Yes, I did mean prevention not protection! Read on…!!

Electric storms are becoming both more frequent and more intense in susceptible regions which is bad news for all sailors and, in addition, catamarans are statistically more likely to be struck by lightning than monohulls. Amanda and I (OK, especially Amanda!!) really dislike electrical storms, particularly offshore. If we have interweb connection when storms are around Amanda instantly develops a morbid addiction to the BlitzortungLive app, which graphically shows lightning activity strike by strike in real time. Phones, iPads and VHF sets etc are stashed in the Faraday cage oven (one day we’ll forget and cook them after they’ve survived a storm) and any suggestion of going to the (carbon) mast to drop the mainsail can be quite unpopular… for days.

So, I researched lightning protection systems and discovered a company called Sertec, in Paraguay, who have developed a lightning prevention system called CMCE. It has been used on airports, tall buildings and merchant ships for a number of years and, more recently, Sertec have developed smaller units suitable for yachts.

My physics education went no further than A Level so please visit https://sertec.com.py/cmce/Brochure-CMCE-ENG-v5.pdf for proper explanation and watch this video clip https://youtu.be/29WMElhJUqo – but here’s my attempt at a crude summary of how it works:

Powerful charges build up within storm clouds
Below the clouds an opposite charge builds up on the earth’s surface
The cloud sends down “leaders” looking for routes to balance the load
“Streamers” go up from the ground and when a leader finds a streamer, lightning strikes
Streamers can be prevented (through de-ionisation) in the area protected by the CMCE
Preventing streamers prevents 99% of lightning strikes

How cool is that?!!

The CMCE is fitted to the top of the mast and requires a modest sized cable (because it only carries milliamps from the streamer) down to a ground plate. This is in marked contrast to lightning conductors which basically attract lightning and attempt to conduct the massive charge to ground without damage en-route…. Which is a tall order.

I think a CMCE has to be worth it for the peace of mind and, of course, to avoid the risk of extensive logistical problems and major cruise interruption while getting lightning strike damage repaired.

The system is most straightforward to fit during the build process and I believe CM will offer it as an option to all clients. It is also quite possible to retro-fit the system to most boats and, for example, UK based Falmouth Yacht Services now offer installations up to superyacht size.

There should be another benefit to fitting a CMCE system. Lightning strike repairs and logistics must be about the highest value insurance claims, other than total loss. All insurance companies should be encouraged to recognise the lower claim risk of yachts equipped with a CMCE, through a premium reduction. I believe some already do.

UpSideUp Capsize Prevention

Let’s be honest, one of the differences between monohulls and multihulls is that multis are very stable upside down. Their form stability makes them highly unlikely to capsize but it has to be good to minimise any chance of it happening.

With our easily driven boat in cruising mode, we’ll set up with the smallest sail-plan needed to deliver solid average speeds, which will give a high safety margin. Nevertheless, just like the improbability of lightning strike, random events can occur, so we think it’s worth adding a last layer of protection with an UpSideUp system.

UpSideUp is a French brand by Ocean Data System, initially developed for extreme race boats and now, as the multihull cruising market has grown, also offered in simpler formats ideal for cruising boats. http://www.oceandatasystem.com

At its most complex, their “Master” system on race-boats can be equipped to release the sheets if heel or pitch angles exceed set levels – release the sheets if rig loads exceed designated levels (to prevent damage) – record loads on rigs, chainplates etc for structural and performance analysis – stop the boat if member of the crew falls overboard – other high tech functions.

At the other end of UpSideUp’s complexity and cost spectrum, we’ve chosen their simplest “Easy” system which detects heel and pitch angles and automatically releases the sheets if they exceed pre-set levels. It will also have quick release buttons in the saloon and cockpit so one touch will release the sheets – equally valid in a MOB situation.

Fundamentally, the system we have chosen comprises:

Control unit which detects the heel and pitch angles
Pneumatic actuator which triggers the sheet release
Cam cleats by the winches which hold the sheets – automatically released by the actuator
Manual quick release buttons

Perhaps this system is a psychological luxury for our cruising style but, as with the lightning prevention system, for 1% extra cost we think this is a much more worthwhile addition than some of the home comforts chosen by many boat buyers!

Additional Electronic Safety Equipment

Most blue-water cruising boats have some or all of this gear but, for completeness, these are the other key items we’ll carry:

Iridium GO!

Satellite comms “router” that allows phones, tablets and laptops to connect to the Iridium network to make calls, send / receive emails and, crucially, when coupled with Predict Wind weather forecasting, download forecasts and routing information. Weather and routing info, plus Rush’s fast cruising potential should allow us to avoid the worst weather – adding one of the greatest safety (and comfort) factors for offshore passages.

Garmin inReach Mini Tracker

A satellite comms gadget which also uses the Iridium network to ping our current position at frequent intervals so “shore crew” can follow our progress – and spot if we stop… It can also send alerts to rescue services and send / receive text messages, so provides relatively low-cost satellite comms back-up, should the Iridium Go! fail.

EPIRB

This unit, when activated, sends an alert via a satellite system to shore-based emergency services, who then initiate rescue by appropriate means – ship / nearby smaller vessel / lifeboat or helicopter if within range.

PLB

Effectively a small size EPIRB. Amanda and I each have a Kanad PLB attached to our lifejackets, which we wear at night and in bad weather. The PLBs can be activated should we fall overboard to initiate rescue via emergency services, as with the EPIRB.

Personal AIS

We also have an Ocean Safety MOB1 attached to our lifejackets. If one of us falls overboard it automatically activates when the lifejacket inflates, triggers a loud audible MOB alert on Rush’s B&G system and displays its location on the chart plotter – a huge help to being found / recovered by our own boat.

Electrical & Charging Systems

Our goal is to keep the boat as simple as we can while nevertheless wanting full liveaboard comfort and autonomy! So that still creates a fairly long list of systems, but we do want to eliminate the need for:

Air con – through great ventilation, light hull and deck colours and heat reflecting film on windows
Diesel generator – through plenty of solar, a hydrogenator and large lithium battery bank
Propane/butane gas – through all-electric cooking

Our key system choices:

Operational:

Nav electronics: B&G plotter- speed – depth – wind – AIS – Radar
Pilot: B&G software / Raymarine electric linear drive
Comms: VHF – Satellite – Cell phone
Electric winches x 2
Windlass
Nav lights

Domestic:

Induction hob
Combi microwave / convection oven
Fridge 1 – Drawer fridge – easy access to frequently used stuff – Isotherm INOX 130
Fridge/Freezer 2 – Top entry – most efficient for cold air retention – National Luna 110 Legacy Double
Hot & cold pressurised fresh water – 40lt calorifier
Electric toilets x 2
Watermaker – DC / energy recovery system – can be efficiency run direct from the batteries – Schenker Zen 50lt/hr
Heating – Webasto diesel / electric
Washing machine – bulkhead mounted – weighs only 18kg – DaeWoo Mini
LED lighting
12v charging points & 240v sockets
Portable waterproof speakers – JBL – driven by iPhone / iPad – eliminates need for built in sound system

12v DC + 240v AC supply

Most of the CM’s electrical system will be by Victron, to ensure compatibility and facilitate back-up service/info as required.

The CM is well designed with all major electrical equipment fitted close to the middle of the boat near the domestic battery bank, avoiding long cable runs. This makes a single 12v DC system practical. 12v is generally required for nav systems etc but many boats need to add a second, 24v, system as well due to long cable runs to high load equipment.

12v Service Batteries: 4 x Lithium 200Ah LiFePO4

12v Engine Start Batteries: 2 x 85Ah AGM

Inverter/charger: 3000w to supply the AC equipment: Hob and combi microwave – a few smaller galley appliances – AC sockets for misc equipment

We’ll have to balance use of appliances at any one time but the next inverter size up (5000w) would be significantly larger and heavier, so we think a bit of active management will be a worthwhile trade-off… and discipline us to be careful with consumption! Overcook it and the inverter will say No.

Charging

Rush will have four battery charging systems, making good use of renewable options, maximising autonomy and providing a level of redundancy:

Solar – 2000w of panels on the bimini/cabin top – see later Solar System post.

Hydrogenator – The Watt&Sea was one of our favourite bits of kit on the Pogo, ideally suited to fast cruising boats such as the Pogo and the CM because output increases rapidly as speed climbs over 7 knots (20amps@7knots – 44amps@10 knots). Admittedly the Pogo had lower consumption (small fridge etc) but it felt great to leave an anchorage, set the sails, engage the pilot, lower the Watt & Sea and, a short while later, have full batteries and more power than we knew what to do with while the boat sailed itself!

The Watt&Sea will slot into a bracket on one of the transoms and be removable for security in port, washing and servicing. The prop is nylon so it’ll be worth carrying a spare or two in case it gets damaged by impact with flotsam although, touch wood (pun intended…sorry…) that’s yet to happen to us.

CM46, CM52, Current Marine, Watt&Sea, performance catamaran — Watt&Sea generic drawing

Alternators – Both engines will have 140amp alternators for charging when motoring. We expect the solar and hydro systems to cover our electrical power requirements most of the time but it will be possible to run one engine to recharge if (OK, when) the infamous Wadhams weather strikes and it rains for days while at anchor. It’s not perfect to run an engine purely for generation but, at 30hp, they’re pretty small so fuel consumption will only be around 1lt / hr and there are many advantages to not buying / carrying / servicing another stand-alone diesel engine (generator).

Shore power – the inverter/charger unit enables plugging in to charge the batteries and heat the water when in a marina.

Propulsion

The choice between twin diesels and hybrid electric (electric motors with diesel generator range extender) was our most difficult decision and it actually gave us one or two sleepless nights.

Fundamentally, the CM46 is light, easily driven and able to sail most of the time, so overall fuel consumption by the standard, twin 30hp diesels will be pretty low.

But hybrid, or even full electric, systems are the talk of the town and of course appealing, in principle. And if they’d work on any boat, surely it would be on a light cat.

We wanted a hybrid system to work for us (all electric would definitely not give the range and battery charging required for our cruising) so built up a spec with one of the well-known electric propulsion brands:

Twin 13kW electric motors
15kVA diesel generator (generator output is the limiting factor to sustained speed under power – but higher output gensets are too large and heavy)

20kWh 48v Lithium propulsion battery bank, feeding a smaller 12v house bank
Run time on batteries: About 2 hours depending on speed – circa 10 to 14 miles
Max speed in short bursts: Approx. 6.5 to 7 knots (max speed with diesel engines: Circa 10 knots)
Cruising speed (using generator to charge batteries): Circa 5 to 5.5 knots (cruising speed with diesel engines: Circa 7 knots)
Diesel consumption at cruising speed using generator: Circa 3lt / hr (consumption by diesel engines: Circa 2lt / hr)
Total system weight (with above battery capacity): Similar to the diesels

This is our summary of the pros and cons of the hybrid system:

Pros:

A “forward looking” solution
Short periods (about 2 hours) with zero diesel consumption and quiet motoring at approx. 5 knots
Large propulsion battery bank which would also feed the house system at anchor
Two props providing regen under sail, meaning we wouldn’t need a separate hydrogenator
Only one diesel engine (the generator) to service

Cons:

Added complexity – 48v motor system – 12v house system – generator – fast chargers etc
Diesel generator required (in our view) for motoring range and for recharging batteries as solar / hydro will not always sufficient
Diesel consumption by the generator at 5.5 knots would (potentially) be higher than diesel engines
Propulsion props are less efficient for hydro regeneration than specific regen props, leading to lower charging rate
Higher cost
Uncertain reliability factor with younger technology

Our hearts said go for the hybrid and we very nearly did.

However… we became concerned that system complexity was rising. DC generators (able to directly charge the batteries) are larger and heavier than AC. Generator output defines the power / speed available for motoring (once the batteries are depleted after two hours) and the 15kVA minimum required meant we’d have to go for an AC unit, to retain the low, centralised weight by mounting it in place of one of the diesels. This would have required several fast chargers to convert the AC output to quick enough DC battery charging… in addition to the need for two battery banks (48v propulsion & 12v house) and voltage conversion between the two.

We just couldn’t settle on the hybrid option because the uncertainties and speed limitations were not significantly offset by reductions in diesel consumption. Motoring periods over two hours would use the same (or more) diesel – even sub two hour motoring would probably need to be followed by generator time to speed up battery recharging and allow electric house systems (inc cooking) to be used.

Decision…

We finally decided to opt for twin diesels and felt pretty disappointed on one level. But, to be honest, we also felt a sense of relief.

We put in the time, researched the technical aspects and the benefits (to the planet and to our practical use) of hybrid versus diesel and we’re now comfortable with our propulsion choice.

I don’t think overall diesel consumption will be meaningfully higher, thanks to the CM’s performance with small engines. It’s a shame we won’t have the huge battery bank that goes with the electric motor system but we’ll increase the house bank capacity which, coupled with a large solar array and a Watt & Sea hydrogenator (one of our favourite bits of kit on the Pogo), should mean the engines are generally only needed for calm passage-making and parking.

Crucially, we always wanted to create a simple, effective boat.

Hybrid v Diesel – Our Summary

A hybrid system on boats like the CMs could be great if the boat was being used for weekending, racing, or even long-term cruising provided the crew were prepared to accept a “wait for the wind” approach or make slow progress against currents. It suits short spells of motoring in and out of harbour / anchorage with long periods of re-charge from solar, shore power (hopefully green sourced) or regen under sail before motoring again.

We may be thinking of our time-limited, cruising past, but passages such as a 36 hour, flat-calm motor out of the Med against the current, with the alternative being over a week’s wait for breeze, are familiar to us. We envisage those situations being part of our cruising life – multiple coastal and inter-island passages between long ocean legs. With weather getting more extreme we see the ability to motor efficiently in calm conditions as a major bonus of the cat.

We couldn’t ignore a safety consideration as well. We, particularly Amanda, have been closely involved in a tragic MOB situation (albeit in very different, inshore racing, circumstances). The thought of limited power impacting the task of finding and recovering someone in bad weather offshore is not something we can ignore.

CM diesel engine installation

The CMs are designed with the engines mounted relatively well forward to centralise weight. They are, therefore, dry and won’t get splashed by sea or rain water when underway as can happen if you have aft deck hatches for access. No corrosion issues – easier maintenance. Maybe there will be more noise in the boat but hopefully that’s offset by lower noise in the cockpit, not sleeping directly above an engine and, of course, the boat’s minimal need to motor makes the biggest difference.

We’re happy with Current Marine’s recommendation of Nanni diesels, which are based on Kubota engines – internationally used in all sorts of applications such as agriculture. We replaced the Volvo engine in one of our older cruising boats with a Beta (a British Kubota derivative) and were impressed by its smooth efficiency. Parts should be widely available – and maybe less extortionately priced than some marine brands?!

Helm Positions

Steering positions seem to be one of the most controversial aspects of cruising cats. Inboard, outboard, single, twin, high, low – they all have pros and cons and people have (very) strong views!

Until we sailed the Pogo, with max beam at the transom and wheels out near the sides, I hadn’t realised how good it would feel, on a cruising boat, to have a great view of the rig, waves and traffic (even though I’d taken it for granted on race-boats). Once you’ve experienced it, you wouldn’t want to lose it.

But… there will also be situations when a protected helm position would be a real benefit… so it’s a difficult choice.

After sailing various boats we concluded that outboard helms with visibility were our priority and we’d accept the compromise on shelter, on the basis that the pilot does most of the work, especially offshore. Sheltered helm positions tend to have poor visibility (at least on one tack) and on one or two cats you can’t really see the headsail luff from the helm…

Twin Versa Helms

The standard CM configuration has twin wheels (I think tillers are an option), outboard towards the aft end of the cockpit, so that ticked the visibility box – and it turned out we wouldn’t have to compromise on shelter.

We’re fortunate to have been boat-searching a year or two after the versa style, hinging pedestals, were developed. CM are onto them and offer an upgrade. It gives the best combination of steering positions that we’ve seen on a cat. The pedestals hinge through about 90° and give both:

Outboard high position: Great sailing view + unobstructed visibility when docking, without peering through salty glass
Inboard low position: Sheltered under the bimini – even fully enclosed by canvas cockpit sides

There is an added cost for these pedestals, but steering positions are so fundamental to sailing enjoyment, easier parking and comfort that we think it’s hugely worthwhile.

Helm Seats

We usually like to stand, rather than sit, at the wheel when hand steering but comfortable configuration for both has to be an advantage. Our solution (at the outboard helm positions) are seats with bases that can hinge up against the backrest when not in use: Fold a seat down to sit within comfortable reach of the wheel – or fold it up to create more space for standing behind the wheel, with the frame giving a bum-rest if wanted.

When the wheels are inboard it will be possible to stand by the wheel or sit on the aft cockpit bench, although a back cushion may be needed to shorten the reach for sitting back.

Line handling from the helm

We tend to use the pilot when hoisting, reefing and furling etc, which seems easier and safer than veering around, juggling steering and line handling. Nevertheless, the CM’s deck layout will be set up so that lines and winches are close to the wheels for manoeuvres.

Instruments

Twin versa helms do create challenges with the siting of instruments and throttles but, alongside CM, we have a cunning plan. I’ll describe it later (if it comes good!) along with the electronics system.

Accommodation Layout

Saloon & Cockpit Our boat will be 46 #2. Boat #1, for a New Zealand owner, will mainly be used for racing and weekend cruising, so its saloon and cockpit layout are more open-plan than ideal for us.

That gave us the opportunity to work with CM on a layout that will be the standard design and certainly fits our wish list:

Indoor / outdoor living space through saloon and cockpit
Large galley with all-round visibility and connection to the cockpit conversation
Forward facing nav station for comfortable night watches
Excellent visibility standing or seated
Three cabin, Owner’s layout

The saloon is pretty wide so the layout maximises use of that, which compensates for its length being restricted by the rig aft / long bows design. That pushes the forward saloon bulkhead aft. It’s one of those design compromises we’re happy with – a trade off in volume for better handling and behaviour at sea. The overall saloon and cockpit space is almost 5.5m long, anyway. If that isn’t enough, we’ve lost the sailing plot!

This is the sketch of the layout. CM CAD modelled it to optimally fit the boat.

It prioritises galley space and stowage, which is up-there with heavier, fatter cats of this length. Likewise the nav station. The sofa and table have space to seat 6 comfortably (8 at a pinch) with a few folding director’s chairs. It will lower to create a watch berth. There’s plenty of sofa space around the cockpit for choice of view, several people with their feet up or for rum&coke o’clock gatherings! Here we are locked down again in the UK winter… Can’t wait.

We’ll add a roll-down canvas cockpit enclosure, meaning the full bridge deck living space will be usable in most conditions, including underway with completely sheltered steering options (which I’ll cover separately).

Owner’s port hull There’s a queen size bunk aft, sofa and folding desk amidships and a big dressing / bathroom forward. There’s space inboard of the shower for a wet-locker (draining into the shower sump) and… a washing machine. Amanda has fully won that argument – I, incorrectly, thought we may manage without…

We’d been interested in the transverse bed under the bridge deck configuration of some cats, which add’s bed space. But, the compromise, on this size boat, is that the bridge deck has to extend further forward, increasing weight and slamming. So, we’re happy with an aft bunk layout that also allows us to talk through a hatch if one is off watch in bed and the other in the cockpit. A quick “all OK?” and it’s possible to relax again without getting up.

Guest starboard hull With cabins forward and aft and a shared heads amidships. The forward cabin has a smart design with three set-up options – double bed, twin bunks or workshop and stowage. The flexibility is ideal to suit various combinations of visiting family or friends.

The guest bathroom is probably the greatest internal compromise. Floor area is restricted next to the daggerboard case, but the space widens as the hull flares higher up and should be enough to give sufficient feel of space. It’s long enough for a shower area and is bigger than the heads on our Pogo, so we reckon it’s important to maintain a sense of perspective. Our mates will definitely accept the compromise in favour of performance!

Rig Configuration

Mast Current Marine offer three mast options: Fixed aluminium plus fixed or rotating carbon fibre. They build their carbon masts in-house, which is rare and undoubtedly explains why we detected quiet “encouragement” by Julian to make the right choice!

Nevertheless, we thought long and hard about this decision. The advantages of cleaner wind-flow over the mainsail and reduced pitching from less weight aloft are real… but do they justify the cost of a carbon mast? CM’s upgrade cost is a bit less than some brands, but it’s still significant in our terms.

After much deliberation, we decided we would go for a rotating carbon mast – although maybe not for the reasons you’d expect. We chose this option mainly because it makes downwind reefing possible – and because the more efficient the rig, the smaller and more easily handled the sails can be. Factor in the reduction in pitching and a rotating carbon mast should make a noticeable difference to comfort and safety.

That said, I think this is somewhere you could compromise and, with an alloy mast, this boat would still outperform most.

Shrouds We’ve chosen Dynex Dux textile shrouds because they’re well under half the weight of stainless steel. In fact, if we’d chosen an alloy mast, I’d have opted for these shrouds anyway to gain a chunk of the weight saving without the full carbon spar cost.

Reefing from the cockpit There’s a significant downside to a rotating mast that we’re going to tackle. Halyards and reefing lines have to be locked-off on the spars, which normally means going forward to reef. To overcome this downside, we’re going to use constrictors instead of clutches because they can be mounted on the spars with their tails and release lines led back to the cockpit for remote operation. CM have suggested reef hooks on the leech reefing lines because once the line is pulled down and they’re “set” no other jamming is required – and they can also be remotely released. Reef hooks also largely eliminate the usual problem of line chafe.

CM are keen to work on the remote reefing set-up to get the spar design, lead angles and deck blocks aligned correctly. If successful, we’ll have the best of both worlds – the ease of reefing downwind of a rotating mast and the ability to do it from the cockpit.

Boom Having chosen the carbon mast we decided on CM’s carbon Y boom to match. The boom lends itself to a custom fit-out to make our reefing line system work – and the stack-pack can neatly attach to the outer edges to widen it and collect the mainsail effectively.

Three headsails on furlers We’ve chosen this set-up because we reckon there are big advantages for our style of cruising. We’ll have a code sail, a Solent and a staysail – all able to be furled from the cockpit. They’ll facilitate a comfortable and safe configuration in building breeze (easy to change down) – and also help us maximise progress (easy to change back up).

Staysail I really don’t like partially rolled headsails – their shape gets deeper, just when you want it flatter – they lose pointing ability – the C of E goes forward and unbalances the boat – increased separation from the mainsail loses upwind efficiency… and they look shocking! So, after experiencing just how much better the Pogo was (with a staysail) compared to our previous yachts (without), a staysail was high on our must-have list. On a cat, this means you need a solid longeron to give a tack point aft of the forestay, so this was an important factor in our boat choice.

The Pogo had a removable Dyneema stay with a hanked on staysail. It was simple and reliable, but it did mean going forward to get the sail ready to hoist and I wasn’t happy when the sail flogged while hoisting. So, for the new boat we’ve specified a staysail with a torsion cable and continuous line furler, allowing it to be stored and hoisted furled, ready for use. Luff tension will be applied by a 3:1 purchase at the tack and it will sheet to a self-tacking track on the cabin top. In light wind, short tacking situations we’ll be able to drop the furled staysail onto the tramp to open up the foretriangle and make it easy to tack the Solent.

Sail Choice See separate later post.

Construction

The construction system was an aspect that drew us to CM. It uses top end materials, not generally available from production brands.

Epoxy resin, carbon and e-glass, PVC cored laminate is infused and post cured. The resin is the glue that bonds all the hull materials together so it has to be best to use the strongest glue. Epoxy resins have up to four times the bond strength of polyesters (used by most builders) and vinylester (a modified polyester) falls between the two.

From my experience, epoxy is essential if you want to build a light and strong boat. Race-boats wouldn’t use anything else (unless restricted by class rules, to limit cost).

Carbon fibre adds stiffness for a given weight but also adds cost. CM offer a couple of options regarding the amount of carbon used and we’ve opted for bulkheads, bridge deck and cabin top. They create a carbon “box” in the middle of the boat where the hulls are joined, the rig sits and shrouds attach, which should contribute max stiffness per precious £.

The forward cross-beam and longeron will also be carbon wrapped.

As a yacht engineer pointed out, stiffness is important in cats because their structure is fundamentally flawed! The mast sits on a bridge – the forestay is attached to another bridge – and the shrouds are attached to separate hulls, which could be on different waves. Monohulls and trimarans do have upsides…

Stiffness maintains headstay tension (upwind rig efficiency), translates drive from the rig into boatspeed and reduces fatigue from flexing, to make the boat last longer.

The hull and cabin top shapes are designed to keep the weight down, with simple curves in most areas allowing the use of un-scored foam. Complex curves require scored foam to bend to shape and these scores open up, fill with resin and add hundreds of kilos for no structural benefit.

CM46, CM52, performance cruising catamaran, current marine — The hull shell of our boat at fairing stage

Furniture The furniture in the CM is foam cored and laminated to the hull shell so it’s light, it contributes to the overall structure and it can’t creak.

Finish Like Gunboat and HH cats, the CM’s hull is finished by fairing and spraying. Awlgrip paint saves several hundred kilos over gelcoat. There are many colours to choose from and, after five years in the sun, painted epoxy boats tend to look much smarter than polyester gelcoated boats. AND… polishing is not needed! Now we’re talking!!

Construction summary

Coming from a composite boat production background, I’m impressed by the build system. Race-boat level lightness, stiffness and strength, with added benefits.

Our Boat Choice

After almost a year of research (I admitted we’re boat nargs) we had a solid favourite boat, but to check our hearts weren’t over-ruling our heads we produced a detailed evaluation matrix spreadsheet with twelve criteria, each weighted relative to its importance to us – ie the most important were scored out of 20 – less important out of 10. Then we evaluated a shortlist of boats from the lightest and mid weight sectors.

The matrix really highlighted what mattered to us and put each boat’s pros and cons into an overall perspective. A couple of boats offered amazing accommodation, but their performance would have frustrated us. One was a bit too skinny and just didn’t give the step up in space we’re after… although it was stunning to sail! I don’t think it would be helpful to post our matrix. The criteria and scores reflect our personal priorities and preferences – but if you’re choosing a boat and an analyser like me, I reckon it’s a great exercise to create your own.

Also, I don’t want to suggest that one boat is better than another – most have been well designed and built to suit the market they target. It’s just important to cut through the blurb, understand the compromises associated with each aspect of boat design, work out the features you’d like and how important they’ll be to you in the real world.

Anyway, getting to the point, the boat we chose was the least well known – a CM46.

The new CM brand has been developed by South African boatbuilder Julian Kneale of Current Marine, in conjunction with Schionning Designs who are well respected in the southern hemisphere although less well known in the north. The CM46 is built from higher spec materials than any of the other boats on our shortlist and that allows weight and performance-potential towards the fastest, but with more space. Crucially for us, competitive production costs in SA allow it to fit our budget. http://www.currentmarine.co.za

There will be pros and cons to working with what is a relatively small company. To be honest, having built the RS sailboat brand from scratch, I can’t help but identify with Julian and Current Marine’s aspirations and challenges. I think I prefer being part of that, over being smoothly processed within a bigger business. Hope that won’t prove too naive! CM only plan to build a few boats each year, so they won’t challenge the mainstream brand’s volumes and, right now, we’re happy to be getting our hands on one before lead times extend.

performance cruising catamaran current marine — CM46 #1 (which is full carbon) – ours will be #2
Looks the definition of easily driven!

Key Features Required

Light Weight

Designers and technically informed sailors all seem to agree that light weight is the fundamental driver of catamaran cruising efficiency.

There is a virtuous circle. A lighter boat:

Is more easily driven and intrinsically faster
Needs a smaller rig to power it
Smaller sails are easier to handle with lower loads
Engines can be smaller and lighter (and anyway you’ll motor less and sail more)
Smaller equipment means the boat is lighter… and so the virtuous circle goes round

And there are some great added win-wins:

Improved motion Light cats with centralised weight pitch less, sail more smoothly and this increases their speed as well as comfort
Safety Speed adds a major safety factor through the potential to outrun bad weather
Simplicity A simple spec keeps the weight down and also reduces maintenance stress

We discovered it’s important to understand what “light” really means. In marketing driven times with so much material circulated by sponsored sailors, the terms “light” and “performance” seem to be applied to all sorts…

We’re looking at boats of around 45 ft, so let’s compare the displacements of a few mainstream models and where they sit in the spectrum:

Over 14,000kg	Circa 11,000kg	Under 8,500kg
Lagoon 450	Seawind 1370	Outremer 45 & 4X
Fountaine Pajot Elba 45	Nautitech 46	CM46
Leopard 45	Balance 442	Marsaudon TS42

To put it in perspective, if you parked two VW Polos on an Outremer 45 it would still weigh less than the 11,000kg boats. Imagine that effect on performance!

I’m not suggesting that boats in one of these bands are better than the others. We all have our own priorities. Everyone understands that the heavier boats have correspondingly more voluminous accommodation and that’s absolutely fine if space is your main priority.

What’s less clear through some of the hype is that we found, by sailing various boats, you really have to look at the lightest sector if you want that feeling of effortless speed, or gliding along under sail when others are motoring.

The light boat compromise

Light boats, of course, compromise on volume and payload. Nevertheless, the step-up from the monohull space we’re accustomed to, to the space in a well-designed light cat, is huge. More than enough for our needs. We’re happy to forego the widest cabins for better handling, quick passages and weather routing safety. And… to be honest, pride of ownership of a real sailing boat is a big thing for us.

2000+kg payload is typically possible in the light boats and, after creating another spreadsheet, we estimate this will be plenty for us. Toys such as SUPs, bikes and a kite-board (on the have-a-go list) will be no problem in addition to spares and essentials. As Pogo said about the first Rush “We built the boat light enough so you can carry what you want”. That seemed a great philosophy and it worked.

For us, the advantages of a boat that will sail in around 4 knots of breeze and be capable of good daily mileages using small sails, in comfort and safety mode, easily outweigh the compromises. An easily driven boat sailing at 10 knots, under lower loads from smaller sails, just feels better to us than a hard-pressed, heavier boat at the same speed.

Additional Key Features

Additional design elements that we conclude are important for us:

High bridge deck You can play around with shapes underneath, but fundamentally a high bridge deck, set well back from the bow, will reduce slamming and drag and improve comfort in waves. Less bridge deck area also reduces weight.

Daggerboards They add cost and some complexity, but without them a boat points around 10 degrees lower and sails more slowly due to the drag from inefficient, long chord, short depth keel sections. VMG may be halved … upwind passages take twice as long. A respected designer of cats both with and without boards (for different brands / market sectors) pointed out the best way to get a cat without daggerboards upwind in adverse conditions is to run an engine…

The ability to lift daggerboards and allow the boat to slide (rather than trip over a fixed keel) in big waves is another safety feature.

Rig set well aft This evolution has been handed down from race-boat development for:

A large foretriangle giving space for different size headsails to be set-up on furlers, ready for use
Efficient separation of downwind sails from the mainsail
Centralised weight and less “pressure” on the bows allowing them to glide more smoothly.

Low windage / low centre-of-effort High topsides and square cabin tops increase windage, with disadvantages at sea and when mooring. Keeping the superstructure low keeps the rig low, with stability and efficiency benefits.

High spec construction If you want to build a boat that is both light and strong, you have to use the best materials and build systems. I’ll talk through construction later so let’s just say that I believe construction is a hidden, but key factor. You can’t see what resin or fibre a boat is made from by looking at it… but it’s fundamentally important. Of course, cost is generally a downside to a higher tech boat…

Boat Size

Feedback indicates that 45 to 50 feet long is a sweet spot – big enough to achieve decent motion and space – small enough to be easily sailed by a couple. For budget, handling and complexity reasons we’re keen to keep the size down so we settled on the low end of that range.

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