Title photograph : WABI”’ Calstock boatyard, Tamar UK
An ocean post.
This is the first post in the practical side of the ocean series and in this one i begin to lay out the basic requirements i have for my ocean going , or at least long distance, cruising boat. The great thing about this side of my blog for me is that this is entirely explorative again as i really don’t know where i will end up this time unlike the situation earlier in the year when i was sure that the Pardey’s approach was the right one and that a small ‘steady’ boat would do the job. Right now all i can say is that if the next boat is a genuine offshore/ocean one then it needs ‘longer legs’ so i will maybe just deal with that one idea in this post.
Most of my readers will have seen the film ‘Jaws’ and will have heard the line “we’ll need a bigger boat” although very few will know a sailing mate of mine who also goes under the name of Jaws who uttered that same line in a completely different context….it was at the end of the first attempt by that team to take the Jules Verne challenge. It didn’t work out and Jawsie simply realised that the boat needed to be at least longer. The principle here is that longer boats should sail faster and do more miles in a day due to a fact of physical hydrodynamics, what sailors , designers and boatbuilders call the displacement rule. Essentially the longer the waterline length the theoretically quicker boat. Of course other things do apply such as the relationship between displacement and sail area, the hull shape, hull and foil preparation, the balance of the boat and so on but at base longer boats go faster and that is often useful.
In an older post of mine i explored the concept of small ocean-going boats with a kind of question … how small ocean ? in other words how small can we go and still have a viable ocean going boat. To explore that i looked at some actual examples of successful small boats that had done ocean voyages. To my thinking at the bottom end of that were boats such as Roger Taylor’s first arctic exploration boat which was a modified Newbridge Corribee at 21 feet. Then as now i discount the record attempting freak boats down to ridiculous sizes. Roger Taylor did say that the little Corribee was all that he needed and do remember that he was taking that boat on transatlantic passages and 7 week arctic voyages. Even Roger himself concluded, after several arctic seasons, that he needed ‘longer legs’ so that he could, on average. do more miles per trip.
Roger Taylor photograph.
That was the starting point for thinking again about my own long distance ambitions potentially with my own slightly larger boat, the 22 and a few inches long Hunter Liberty. A modified Liberty has been across the Atlantic via the kinder southern route so i started thinking about and writing about a potential ocean passage with my own boat in the blog. Right now i am resurrecting the unfinished posts and will publish those in this series. Ultimately i don’t think the little Liberty is at all the right boat for an extended ocean voyage mainly because it doesn’t have the ‘legs’ for it , doesn’t have the range of stability i think is needed and would be difficult to live aboard, i think, during a long passage. It’s those things that i want to start off by exploring today. In his own impressive voyaging Roger Taylor did thousands of miles in the tiny Corribee. They really are very small boats and Taylor came to the same kind of conclusion that i have , that his boat needed ‘longer legs’, not necasarily more space inside but rather the ability to do more miles per day and cover more ground in his explorations. I find that i need both ‘longer legs’ and more living space aboard a boat especially with my partner aboard.
There is a second principle at work here and that is the ability of any boat to carry load and not get excessively ‘loggy’ in the water. To some extent carrying capacity is also related to size although displacement might be a better measure than length. My Frances 26 never felt like a ‘leggy’ boat although it did get on with the job steadily but it was a very good load carrier….note to self..stop saying ‘it’…..boats are feminine therefore ‘she’.
Frances 26 ‘La Luz’ about to transit into the Pacific (owners photograph)
I have pushed the envelope a bit with my Hunter Liberty as, strictly speaking by EU classifications, she is only an inshore and protected waters boat although i’m pretty sure you can hear the unspoken comments about that !. Taking her across the channel in a light northerly was no big deal, just a matter of steering for that long, keeping watch and staying awake. Now i would even have the luxury of a tillerpilot and a big battery to run it off. Hand steering for that long was a bit of a pain but it got the job done. I was very tired and a bit fuzzy when i got into Roscoff just after dawn the next day but then again i had been awake for over 30 hours. It was the return trip that showed up the Liberty’s limits though.
Our cruise around the north Brittanny coast was really good in the Liberty because we were able to use that shallow draught effectively, we put into places that keelboats just can’t and often beached the boat. From Paimpol we made the short offshore hop to first Jersey and then Guernsey but then had the problem of the cross channel leg back to either Plymouth or one of the harbours between there and start point. Our problem was that instead of a normal south-westerly or westerly airstream the wind was solidly north of west and that made our course all-but on the wind, on top of that we were going to be sailing across a big spring tide wind against tide for at least 6 hours and then if we missed our tidal gate would have 6 hours of foul tide pushing us back towards start point. Of course the wind headed us…what else could happen and we had a hard time of it also missing our mark at Salcombe and ending up being swept down-tide. Instead of being in Salcombe for last orders we didn’t get in for another 4 hours.
I could bemoan the fact that we had a much harder channel crossing than we expected but that’s not the point i want to make today, that passage would always be tough in the Liberty and that i would always have to drive it like a race boat. Instead what i want to do is dial back a few hours to us just leaving the little Russel channel as early as i could that day and talk about other boats making that passage.
I planned that passage as tightly as i could so that we could just about depart and arrive in daylight. About an hour after we cleared Guernsey a line of larger cruising boats came out of the same channel behind us and all apparently on the same or similar course. All of those boats came past us quite easily on the hull speed close reach. I think i remember that most of those other boats were in the 30 foot range and i am pretty sure that i recognised a French half-ton cruiser-racer, the First 30 as one of them. For today’s exercise in theoretical passage speed i am going to use the Liberty and the First 30 as my 2 main examples of passage making speed. The main thing i am going to work with today is the idea of theoretical maximum hull speed , so displacement speed and ‘normal’ passages where sail area or conditions don’t become a limiting factor. For some reason i can’t express the mathematical formula here properly but for reference i am taking the square root of the waterline length in feet and multiplying by 1.35 as being the theoretical hull speed.
If we go to the boatdata site we get that the Liberty has a load waterline length (LWL) of 19.03 feet and if we crunch the numbers we will get a theoretical hull speed of 5.6 knots. The same thing with the 30 footer gives us a LWL of 26.97 feet and a hull speed of 6.75 knots. Lets say that i was losing some performance because the wind was far forward and making 5 knots average and that the larger boat is also doing similarly less well…lets say that he is still making 6 knots say for my 5…..that’s a 20% difference in my book. I’m pretty sure that he was also heading for Salcombe, in fact i think i saw the boat the next morning. If we play around with some passage planning here we get a distance between St Peter Port and Salcombe as around 90 nautical miles so we can now calculate our time on passage for each boat. Given the average speed and not allowing for tides that passage should take about 18 hours in the liberty and 15 in the larger boat. What tends to happen though is that a faster boat can often beat a tidal gate…..what happened to us is that i missed our tidal slot into Salcombe by about 2 hours and then spent about 4 hours motor sailing hard upwind and up-tide to make port…..and those last 4 hours were really cold and uncomfortable. Just for fun a little while ago i did a lot of number crunching using different boats and their theoretical hull speeds to work out what size of boat would have just done the job on the day, the answer was that i wouldn’t have needed much more average speed….just half a knot extra would have done the trick.
It’s quite an easy and satisfying exercise to get the numbers on some potential boats that i have taken an interest in before and see how they stack up. Now, don’t think i have gone all sailing nerd and started doing spreadsheets, i don’t think i would recognise a spreadsheet even if somebody smacked me with one ! Lets instead pull up some photographs and stick numbers on them. Don’t worry about the maths either, even for someone like me who hates it, its pretty basic.
LWL 19.03 ft. Hull speed 5.06 knots
LWL 19.5 ft. Hull speed 5.9 knots
LWL 21.25 ft. Hull speed 6.2 knots
LWL 19.17 ft. Hull speed 5.9 knots
Bilge keel and deep fin keel options.
Ecume de Mer
LWL 19.5…….hull speed same as Achilles 24
I am looking at some longer boats in the new series too so here are a couple of examples from the early and mid IOR period half-ton class.
LWL 22 feet, hull speed 6.3 knots (possibly actually higher due to the overhangs)
Westerly GK 29.
LWL 27.58 ft. Hull speed 7.02 knots
We had a look at the GK 29 when we did our boat tour last year, the one we saw stank of wet sails and manky bilge , Jax didn’t like it at all so that was a no-go. The other boats are all ones that featured in the basic boat/starter boat series. Of those boats a modified Achilles is doing the job for Roger Taylor, the Ecume de Mer has popped up here with the ‘Sailing Frenchman’ and i know of at least one Sadler 25 that has gone transatlantic. The Javelin is an older 30 footer with long overhangs which i suspect would be faster in some conditions than the numbers suggest. We might go and take a look at that one.
The raw numbers don’t tell the whole story, for example they don’t give any indication of the way that a boat feels at speed. I know that the Frances 26 has a kind motion and gets on and does the distance without rattling its crew around like a tin can. The Achilles 24 and the Sadler 25 i know are quicker boats than the Liberty because i have sailed boat for boat up against one of each. I think that on the day either of those slightly longer legged boats might just have got us into port before the tidal gate closed. Both of those boats also have more living space than the Liberty, the Sadler coming out best in that regard due to its beam.
While passage making speed is now my first priority for a longer distance boat i still want to be able to slip into shallow water at the end of the passage and then have the option of beaching the boat. Both the Sadler 25 and the Achilles 24 have keel variants that would allow that so both boats stay on the radar. Its a shame that this one (below) doesn’t have the triple keel option as its got a nice rig and sails. In this series i will also start to look beyond the current range of small boats and see what i can find in the 30 foot range, or old IOR half-ton size, because they are so much better living spaces and load carriers than the 25 foot boats that i have featured so far. That size probably represents the affordable ceiling as gear starts to become a lot more expensive.
This one might be good value.
In this first post i have taken just one small but significant aspect of potential sailing performance ie theoretical hull speed and put some actual meat on the bones of some potential small boats. I deliberately didn’t include the Deben in the mix because although it has a theoretical hull speed i never achieved it even in ideal reaching conditions and certainly never when beating in a chop. When i return to this subject i want to continue the theme with the next measurable values for example displacement and sail area , the former because i think it affects load carrying ability and sail area because that ultimately determines actual sailing speed. I don’t quite know then how to approach the soft science of boat performance which i might describe as sailing ‘quality’ or how the boats actually behave at sea. For now lets just stick with the one simple idea that a bit more length and actual speed would be beneficial, it wouldn’t take much extra ‘legs’ to make cross channel and longer distance passages a bit more viable. That is the first indication for me that we should be thinking about slightly longer boats and benefiting from more hull speed and secondarily more space inside the boat.