Sunday, June 19, 2022

Four different Propulsion systems for our catamaran


We are building S/V Lynx from a Schionning Designs kit.  Now, having made the decision to build our catamaran vs. buying new or used, that means we have a whole lot of decisions to make on what goes into the shell of the boat.  Foremost in those decisions is which type of propulsion system.  We considered four different setups which I will now go over, briefly.

#1: The most obvious and common choice is a pair of 55hp diesel engines on shaft drives.  These have a lot of advantages, but the biggest one is price.  These will cost something like $30,000, or more, less than the other three choices.  That is a lot of money!  Diesels also have the advantage of using a very energy dense fuel, diesel.  This means, pound for pound, diesel has more potential energy than what you can put into a battery (which the other three systems all use).  Now for the downsides. 

They require a lot of maintenance since they have a complex system of moving parts.  They stink and make a racket while running.  They do not do well at an idle, so you either have to go somewhere to charge your batteries, or add a generator, which is a third diesel engine, requiring even more maintenance.  They also burn a lot of fuel, since any time you are motoring, you are burning diesel.  They also require warming up, so you cannot get instant power if they were not already running.  Finally, they require a certain amount of RPMs to function, so maneuvering in a marina or any small area is more difficult.

#2: A Hybrid Diesel / Electric system.  This consists of two electric motors (sail drives most likely) and two diesel generators.  Now, you could go with only one generator, but then you would be sorely underpowered for any lengthy motoring situation where you need all their thrust.  Let's start with the good stuff.  Anytime you are doing short passages, it is unlikely you will even need those generators, so you can make such a passage on zero diesel fuel.  The electric motors need no time to warm up, so they

are ready in an instant.  They will give you full torque at any RPM, so maneuvering in tight locations is easy.  While sailing, the props can be put into regeneration mode, which means the water moving past the props turn them backwards, which turns the electric motors backwards, which sends power to your batteries.  With solar on top of the boat, you have two ways of recharging your batteries without using those generators.  While running, they have no smell and are nearly noiseless.  Now, for the negatives.  There are two big ones, the high price to install the system (which includes Oceanvolt SD 15 servoprops) and the woefully reduced horsepower.  These are 15 kw electric motors, which equate to 20 hp.  That means, full out, they only give you 40 hp together... and electric motors should not run at full power for long periods, so for that, you may only have around 32 hp!  For a big cat, which normally requires about 100 hp, that is only 1/3 of the needed thrust!  Finally, the range is very limited on batteries, no more than about 3 hours at typical cruising speed.  That means, on a longer passage, you must turn on the generators.  These are less efficient than diesels due to the number of conversations of energy.  Each conversion takes energy away.  Therefore, while running on diesel fuel, you are burning more diesel per mile than a straight diesel boat.  This kills the efficiency on long passages and makes you carry a full load of diesel fuel.

#3: Parallel Diesel / Electric system.  Here, you have two 45 hp diesel engines with an electric motor attached between the diesel and the shaft drive that leads to the prop.  The system can run on just the diesel or switch to the electric motor.  Now you have the option to be a diesel boat, with all those advantages, or an electric boat, with all those advantages.  But there is more!  If you add a clutch to the

shaft, you may disconnect the diesel and electric motor from turning the prop and that lets the diesel engine turn the electric motor, becoming a generator.  Now you have two generators on board, without the added cost, weight, and maintenance of separate diesel generators.  Now let's talk about the negatives, price and weight.  This system is more expensive than the Diesel, though less than the Hybrid.  It weighs less than the Diesel boat simply because it does not need a separate generator, but weighs more than the Hybrid (because, at times, the Hybrid has to carry more fuel on board).  Still, all said and done, this was our top contender for the propulsion system for S/V Lynx... until we looked at the final option.

#4 Combo Parallel Engine and 20 kw Electric motor.  In this configuration, we have a parallel engine in one hull (see above) and an electric motor in the other hull.  Both use shaft drives. Because there is only one diesel, we increase the size of the engine to get 110 hp.  That makes it equal to the diesel boat and more than the parallel boat.  In the other hull, we put a single 20 kw electric motor that produces up to 28 hp, full out, or 22 hp for long periods.  if you add that to the diesel, your total horsepower is 138, more than any of the other options!  Better yet, you are getting rid of one diesel engine, meaning you

only have one diesel on the boat to service and maintain.  That also gets rid of a lot of weight!  This system is anywhere from  147 to 568 pounds less than the other three options!  Both electric motors can regenerator power.  The Parallel engine can act as a 10 kw generator.  Then there is the price, this Combo system is less expensive to add than either the Hybrid or Parallel.  As for the Diesel, over time on our double circumnavigation of planet Earth, the Combo system will save on fuel and maintenance to nearly match the Diesel boat price.  The Combo system also has greater range, weighs less, has more horsepower, has redundant propulsion systems (diesel or electric), requires less maintenance, and saves more fuel.  Sweet!

In the end, we will burn 2,600 gallons less fuel, smell and hear a diesel engine running 6,000 hours less, do shorter passages without burning a single gallon of fuel, have extended range on long passages, including endless electric power from solar and regeneration.  And all that, while shedding well over 500 pounds of weight compared to a Diesel boat!

That is why we are going with a Combo propulsion system on S/V Lynx.  Right now, we are considering which parallel engine and which electric motor to purchase, though we have some front runners.  We want both to have 20 kw electric motors that run at 48v.  That limits our choices as many  20 kw motors run at a higher voltages.  However, there are some choices available, we just have to decide on which one!

If you would like to see a more detailed comparison of these systems, including a bunch of example passages comparing fuel usage, follow this link to the pertinent page on the S/V Lynx website

Or, just go to later.

Tuesday, March 1, 2022

The Perfect Catamaran for S/V Lynx

For years I have been looking for the perfect catamaran... she did not exist.  People will tell you that every boat is a compromise.  However, for years I dreamed of a catamaran with good performance, at a decent price, that was also a comfortable boat, something of a hybrid between a spartan fast performance boat with poor LCC and a fat slow condomaran with all the comforts and no performance.  As you can imagine, it was like looking for a unicorn.


The issue is simple, catamaran builders cater to two different groups.  The first is the charter industry, where comfort and a cheap entry price are all that matters since these boats are cruising around a limited location, like the BVIs or the Society Islands.  The second are boats for the performance blue water sailors.  These are for sailors who want speed at any price, so the boat companies build hulls out of carbon fiber and nix any un-needed comforts to keep the hulls thin and the boat light, and the price to buy them is very high.

Now, I could get both comfort and speed if I were willing to spend 2-6 million dollars to get a large
enough performance boat (see pic above).  The sheer length lets the thin hulls achieve enough LCC (Load Carrying Capacity) to allow for some comforts, but at the cost of too much money to afford for the average Joe.

Salina 48 from Fountaine Pajot

For what I have to spend, somewhere in the realm of a half-million dollars, the best compromise seemed to be a comfort oriented, production cat (see pic right).  I decided to sacrificed performance to gain comfort at an acceptable price.  

Yet, I dreamed of a few small things that I could not have.  For one, comfort deigned cats use mini keels, and though they have their advantages, the loss of pointing ability and shallower draft were things I knew I would sorely miss.  They also come with sail drives as these are easier for the builders to plunk into a hull for swift build schedules.  Now, both of these things do work, and even have some advantages, yet for a blue water circumnavigator, I would prefer the pointing ability of daggerboards and the shallow draft they give you when up, as well as shaft drives (for when I run over a log, container, or bommie so that I don't tear out a massive hole in my boat when that destructive object hits the sail drive.

Sports Top helm

On another note, there is the helm position.  This is a personal choice, as different locations offer different advantages.  It just so happens, I like a sports top helm position (higher than bulkhead, lower than flybridge).  Performance cats rarely offered this configuration, and when they do, they cost too much money for my wallet (like the HH55).

And there were other things on my wish list, like the performance to sail in light winds.

I kept asking, "Why doesn't some company make a comfortable cruising catamaran with daggerboards, a sports top helm, a large salon and cockpit, and shaft drives?"  But there just wasn't one available at a price point I could afford.

So, I gave up my dream and settled on buying a used, comfort oriented, production catamaran. I planned to do a major refit to put her in shape for a circumnavigation of the planet.  Basically, I compromised.  Next, I spent a decade saving up the money to make that half-million dollar purchase.  During that period I watched the used boat market and there was a consistent trend.  New boats dropped in price and then slowed their depreciation after about eight years.  I could predict what a boat would cost based on its original selling price and the number of years since it sold.

For unfathomable reasons, Covid changed all that.  In the last year or so, the prices of used boats have
skyrocketed.  Not only that, but even at these new exorbitant prices, boats sold like hotcakes.  For ten years, there were always boats I could have purchased, had I the money, but now, right when I have just about saved the amount I need, used boats that I was interested in buying have jumped in price by $100,000 or more over what they should cost for their age.  Even at those ridiculous prices, there are none available of the models I used to want, even if I could afford one.  Sadly, if I could find one, I have enough to buy the boat, but then I would not have the money I need to refit it for a circumnavigation.  I could keep working and save more money, but that would delay my trip for several more years and I am not getting any younger.

I went seeking a way to save my dream. I took a second look at an option that I had researched years ago,  building a kit boat myself.  I knew that it used to be less expensive than buying a new boat if you don't count all the labor you will spend building the kit.  However, I never found a design I liked.  They tended to be performance cats without much in the way of comfort.

Then, wonder of wonders, I found a fairly new catamaran kit boat from Schionning Designs.  The first one is nearing completion in Thailand.  This is a performance catamaran, yet she is built in the style of a comfort catamaran. 

Solitaire 1490 render

 This boat is 50' 4" long, 25' 10" wide, which means she is long enough to have some LCC.  She has daggerboards and shaft drives, and kick-up rudders, so she will point well and have a better chance of surviving a collision with a destructive object.  She has a shallow draft, with good bridge deck clearance.  She has a sports top style helm, a large cockpit, and salon.  She is built strong and light, and designed to be beached.  

(My customized layout of the helm, cockpit, and salon.)

This means this boat hits nearly every option I have been looking for in a boat all these years, a melding of performance and comfort in a catamaran.  Not only that, but since I will be building her myself, I can modify the layout and get almost exactly what I want!  Not only that, but in talking to the wonderful people at Schionning Designs, I have found that they are willing to modify the kit to fit my goals!  How great is that!  Even all my changes will be precut for me and arrive in the kit, ready to assemble! 

But what about the price?

We can build this Solitaire 1500, which means we get a new boat.  Even fully kitted out and ready to sail around the world she can be built for about half a million US dollars.  That is right in my budget!  Still, as everyone will tell you, every boat is a compromise.  However, in this case, it is not the boat or what she offers that is the compromise.  The compromise we have to make is doing all the labor it takes to build this catamaran.

'Escapade' currently under construction

It will take a minimum of 6,000 hours of labor to build this performance cat, so not everything is rosy.  Still, I will end up with a new boat that is everything I have been seeking rather than a 10 to 15-year-old boat that is smaller, without the features I want, and costs more.  I can speed up the build time by adding more people to help.  With three, full time workers, the construction of the shell can be done in one year.  Adding all the systems can be done in a another nine months. However, even though I plan to work with two other people on the construction, we are figuring two full years because we know there will be various delays along the way since we are amateur first time catamaran builders.

Solitaire 1490
The boat is from Schionning Designs and this hybrid performance/cruiser is called the Solitare 1490.  I was planning on starting my search for a used boat later this year and, after, finding, buying, and refitting, have her ready to sail in about a year after purchase.  At this point, I am looking into starting the build of our customized Solitaire 1500 at the end of 2022, so that may put me about one year longer than a used, refitted boat (it depends on how long it took me to find the used boat).  I hate the idea of all the construction work and, possibly, one additional year delay but love what I will achieve in the end, the boat I have always dreamed of owning at a price I can stomach.

'Escapade' nearing completion of the shell
So I have a possible plan, one that I will have to decide on soon.  If I go with the kit boat, S/V Lynx will be a Solitaire 1490, extended to just over 50', so now a Solitaire 1500.  She will have daggerboards, kick-up rudders, and a hybrid diesel/electric propulsion system.  She will have decent LCC yet sail close to wind speed.  

If I choose to build this catamaran, I will video document the entire construction process on Youtube, so you may follow along and see how we built her and all the cool systems we add.  And, you may see if this is something you might wish to do in the future!  I will be asking Schionning to make my design available to anyone as the Solitaire 1500.   I'll keep you informed if they agree.

Stay tuned and subscribe to my SVLynx channel on Youtube so that you do not miss the start of the weekly videos.  That way, you may follow along from the beginning of this adventure (See link below).

                                                               Youtube Saling S/V Lynx