Derek Kelsall Interview

We spoke with legendary catamaran designer Derek Kelsall. We cover his history and innovations in catamarans design and construction such as the foam coring, KSS. We ask him why his designs and build techniques are so heavily criticized. He talks about what size of a catamaran that a couple or family should purchase and where catamaran design is likely to go in the next decade.

Please find out more about Derek Kelsall on his website. You can email him to ask questions and purchase plans or built kit.

Thanks for joining us, just start by telling us about yourself.

Designing and boat building is my second career. I spent 10 years in survey work and in oil exploration that took me to Kenya, to Libya, and to Texas. It was in Texas that I built my first boat.. When I left school, I wanted to travel. I discovered hitchhiking and went around Europe.

First time I came home with money in my bank, I got a pilot’s license, which didn’t cost that much in that time. 130 pounds I think, but this is going back a long way. I wanted to sail in the Pacific Islands.

I was in the single-handed transatlantic race, which was a spur of the moment decision made in March 1964. It was a very low budget project. I was in the Bahamas at the time, spur of the moment, oh nothing happening here, I’ll go start building a boat and enter the trans-Atlantic race. We had six weeks to build the boat when it started, with three hulls supplied by a company called Cox Marine. Put them together, a standard Fiver, but without this accommodation, and I led the way out of Plymouth Sound.

But a week later, I had run over something at nine knots and broken my transiting weather and the daggerboard. So I was sitting there with no means of steering. I later found out that there was only one man further west than myself and that was Eric Cavalli. He was just five miles ahead of me and Francis Chichester was in second place finishing, and he was on the same longitude as myself, and let’s say it came in seconds. I made up a jury rig, sailed back to Plymouth, did repairs, set out again, and it took me 34 days. Only three men, I think, have done better than that.

Interesting story. So that’s how you got into designing boats?

Yes, that’s the background to it. During the trans-Atlantic Race I’ve met this man, this director of the company in Cornwall. This was a bit of a disaster in some ways. Anyway, they employed me for a few months, or for a few weeks actually, when we found the company was going bankrupt anyway. Eventually I took over the premises and finished some projects which were already in progress. Then I got the chance to build a boat which is my design, to enter the 1966 Round Britain Race.

Toria – Winner of 1966 Round Britain Race with Kelsall as designer, builder, and sailor

It was the first foam sandwich, so we’ll be learning as we go, how to handle the foam. The design was very different to anything from before, but now everybody has followed that style, and we just ran away with a rounded race. It was a lovely race, two thousand miles and four harbor stops on the way, around this round island around the Chatham Islands and back into Plymouth. Anyway, we finished a day ahead of everybody else.

Then we got a contract to build a boat for the next single-handed trans-Atlantic race in 1968, both called Sir Thomas Lipton. Sir Thomas Lipton with Jeffrey Williams won the race. This was followed by several other multiples winning the Round Britain Race.

The next really really big one was, we built a boat for the Whitbread Around-the-World Race. This boat finished first around the world, so that was quite a big good start for my boat building career. I never really wanted to build. I wanted to be a designer. But you can get into the starting company to build a particular project, it’s quite hard to get out again.

There’s a lot of information out there on the internet about the Kelsall Swiftsure Sandwich Construction. Can you describe this method of construction?

The way I work, I keep on looking for better ways to do things. The first boat we did was fairly traditional, and we made the framework covered with the foam, fiberglass on the outside, take off the foam, and fiberglass on the inside. We did quite a lot of boats that way.

Then in the early 70s til the mid 70s, had a contract to build 50-foot catamarans, and I built a table that was 60 feet long and about six or eight feet wide. We put those panels on this table, and it just makes sense to be using resin. It’s better to put the resin on a flat surface, and then we can use our latest technology, which is there’s an infusion, so using vacuum to spread the resin, and it all works.

Eventually, you got to the point where every part of the boat could be built as a kitted panel. So on a whole, this ground build was made putting two panels together, leaving off some of the fiberglass, a few dark cuts, and they go into a perfectly fair shape. We’re still improving, still making some improvements, but they are minor now. We’ve been doing it this way for the last thirty years or so. Heavily criticized, yes. By every other designer, actually.


Particularly two or three others, and an incident which sticks in my mind. I had sold a trimaran to an American who was doing business in Houston, England. And yes, he said he would buy this trimaran and he gave me a check. Next morning, he rang up and said he’s sorry, he had had to cancel the check. He met another designer who told him how bad foam sandwich was, so that was the attitude of the few people at that time. A year later, I had one of his boats. He built a foam sandwich finally himself, and it was in my workshop for repairs. That’s kind of the situation I have dealt with quite a lot in my career. Obviously, it is so far ahead of anything else you can do, with designers who will find something to criticize.

Tell us about the KSS 46 design.

KSS 46

This is a design which is fairly standard. A few have been built in Peru by Georgio Balota. Still been building my boats now, for the best part of 15 years, if not more than that. We held the KSS workshops in various places, and he came to one in Texas. That’s the tale, and then he went back where he had a small boat that was in business, and he’s been building my designs ever since. He’s built 58-footers, he’s building a 64-footer now, and he stayed busy ever since. Obviously, the labor cost is fairly attractive in Peru.

What is the most popular design that you sell?

I don’t know actually, probably it is the 46. I probably sold more of those.

My competitors say about KSS, “That’s only for professionals.” But in fact is simply not the case. We get some of the best results from people who’ve never built before.

Anyway, there was a doctor and his wife, a very busy couple, they built their own catamaran in about a year of their mostly spare time. This is fairly typical.

Of course, home building has now gone out of fashion when I started. If you wanted to know how, you built it yourself. Now this policy is quite a lot on the market. One of the basic problems is that everybody claims that they have the best build method. But then other potential builders see how long it really takes, using the more traditional methods, and that kind of kills the market. Unless you can show people that method is really efficient, and now they think we see some ridiculous build time claims for some designs, like a 50-footer.

I know a couple of designers have 50-footers, and they take four thousand, five thousand hours. It was one of these built here in New Zealand, and they took fifteen thousand hours for a professional crew building. So now people find this out half, as they bought the plans, unfortunately. Then they look around and they visit other designs being built, and they will see that those claims are way, way out.

So in your opinion, why are some of your designs heavily criticized, as you said?

Well, basically because the path of the build is so good. Where I’ve looked at is over here: we’re using liquid resins to put it down on the top, that you can do 90% of the laminating on a table. It just makes sense rather than do it over a boat shape, or a hull shape, and then have to do the outside and put a finish on it on the inside.

Of course the big, really big, saving is that each panel comes off the table with a smooth gel coat finish. Because they’re full length panels, they will automatically take a fair line, so you’ve got a no compromise. I’ll shape everything else has a smooth finish, including the top sides of the hulls have a smooth gel coat finish.

Literally, most catamaran designs of at least 45-foot or over, the owners will be using traditional methods to spend four to five thousand hours just producing your thing, which is not a pleasant job, anyway.

I don’t know, I guess I’m not the best salesman in the world when it comes to selling my own prowess.

In your opinion what’s the ideal catamaran size for a couple that’s going cruising?

I think around the 40, 45-foot. My Atlantic sailing was on smaller trimarans. My first major Atlantic storm lasted about three days, not very pleasant. Now, we were running under the bare bones, and that was a trimaran which is far less stable than a 40-foot trimaran would be. I think from that point of view, it couldn’t go any worse. Obviously, size makes it much more comfortable, the size of the boat compared to the size of the waves makes a big difference.

How about the ideal size for a family, do you suggest bigger than the 40 to 45?

Not unless you know the expense is going to go up quite highly. But on the other hand, you know you’ve got a lot of space in there, in those boats. If you’ve got the crew, you can handle them, then go bigger. Maybe you’ve got instances of the 58-footers built in Peru, and the owners have done a lot of things, a lot of miles, to our owners in particular. A 70-footer was built here, I spent some time on that, it’s now in California. We’ve been spending time on the online boat and it was built 20 years ago now, and it’s still sailing today. Now normally you’ll have one or two people, which is key.

To wrap up today, looking ahead the next 10 years, where do you see catamaran construction going?

There will be more and more catamarans, and less and less other yachts. Everywhere here’s super yachts, emotional fishing boats, ferries. We’ve done quite a few ferries. We’ve got a 150-passenger, 82-foot catamaran molds that are being made in in the Philippines at the moment. They’re looking to do eight to ten a year of this particular model. We’ve got a lot in the Philippines, a lot of very old, great plywood boats that have been are operating, where you lose a few each year. I think there’s actually been a law they must replace these wooden boats with a composite boat and this friend of mine, a Frenchman, set up to build in the Philippines.

Derek what’s the best way for viewers watching this episode, if they’re interested in your designs, to find out more information and get in touch with you?

Email, by all means. Any questions far and away, I’m happy to answer. We’ve got study plans, we’ve got a lot of these different designs. We actually welcome customer design as well, adding to our range of boats. There are about 500 different designs over the last 50-odd years that we have designed.

That wraps up today’s episode on, thank you for joining us and don’t forget to click subscribe at the end of this episode. Thank you, Derek.

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