Speed vs Sustainability

One of the most visible conflicts when aiming for Sustainability in almost any area, is between it and Speed.

The obvious starting place is speed in terms of moving fast, where the sustainability cost is clear and huge. Speed never comes free. All forms of transport require significantly more energy per unit of distance at higher speeds. That is because air resistance increases much faster than the speed (typically by the speed squared). For boats the drag of the water is much greater as it is so much more dense than air.

However, it is even more complicated for boats. When not planing, a boat has a maximum hull speed (approx between 1.34 and 1.51 times the square root of the waterline length in feet – see WikiPedia). For Vida that gives an approximate maximum hull speed of about 7.5 knots.

In practice what that means for Sustainability is that however powerful an engine we put in we will not go any faster than 7.5 knots. As a boat moves through the water it creates a standing wave which is very visible if you look at a boat moving, just behind the front of the boat is a peak, at full hull speed there is just one wave with the trough at the back of the boat. Any extra speed makes that wave steeper and you can never climb up it and so you can’t go faster.

But the real issue is that the amount of energy needed to reach the maximum speed isn’t simply a proportional increase. We can only estimate at the moment because there are so many variables according to hull shape, loading, windage, sea state etc we won’t know exactly without a lot of real world testing. However, we would expect to need twice the energy to do 7.5 knots as say 5.5knots.

The impact on our electric motor will be all about range. At full speed we might expect roughly 7.5 knots for 1.5 hours ie 10.75 Nautical Miles. However, if we drop the speed to 4 knots we might be able to motor for 6 hours or 24 Nautical Miles. Of we drop again to 3 knots (or typical canal speed) then we will add considerably more range.

Even when not directly burning fossil fuels, speed is costly in Sustainability when sailing. To go faster you need a longer and lighter boat (typically built using more “exotic”, less sustainable materials and methods). You will need higher tech sails that perform better but use more exotic materials and typically need replacing more often.

To go really fast you need to get past the hull speed restrictions. You can achieve that either by having a boat than can plane (flat bottom, lots of power and very low weight – typically not going to be affordable or suitable for live aboard cruising with a small crew) or a multi-hull (trimaran or catamaran) where the hulls are so narrow that the hull speed formula no longer applies).

Length is the “easiest” way to get extra hull speed which is one reason why sailing cruisers keep getting bigger but this is also going in the opposite direction to sustainability as then they use more resources at build time and throughout their life (and they increase much faster than the length does).

On the other hand speed increases do have a multiplying effect. Faster boats can more dynamically route to get huge benefits by being in the right place for far more advantageous weather systems. That can make a far bigger difference to ocean crossing times than the simple speed difference. This video shows this at it’s most dramatic (but is pretty much as far from sustainability as you can get in a sailing boat)

However, I want to move beyond thinking speed in terms of movement and extend it to speed of progress.

In every area, progress is not proportional to the resources used. We know this from every area of life. As you add more and more people to a job it doesn’t keep getting done faster at a proportional rate. If you want to have your driveway paved it will not get done 100x faster by 100 people compared to 1 person (most of us can’t fit a 100 people on our driveway, even if we could they would be getting in each others way, getting the materials to them fast enough for them all to work at full speed would be difficult, you would need people set aside to co-ordinate them etc).

So as we seek to be more sustainable I suggest that we will also need to slow down, in our expectations, in our plans, in our work rates and in our spending.

The benefits multiply across all our areas of sustainability (Environmentally; Financially; Mentally; Physically) if we slow down. We can have time to plan better, to find better options/bargains, reduce mental and physical stress, to avoid mistakes.

This is why we decided to start the process of getting to a live aboard cruising retirement life years before we will be living aboard. By doing so we can be more sustainable, achieve more for less.

What works for us in this example scales up in all kinds of ways across society. Faster isn’t better, slower is usually more sustainable. All we need to do is reprogram our expectations (all we need to do!!!! Hollow laugh). Fortunately, once people of tried slowing down they tend to prefer it and become advocates, which is a good reason for hope. It has left us thinking that one of the things we should be looking to offer when Vida is afloat is the chance to experience cruising on a zero fossil fuel yacht in sustainable ways.

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