Sunday, July 6, 2014

A Cautionary Tale of Ultralightweight Production Dinghies

I have been keeping up with Tillerman's excellent posts about the new RS Aero singlehander. RS intends to build the Aero hull to a 30 kg. (66 lbs.) hull weight. This is a very, very ambitious target for a production dinghy. When I read of such super-lightweight numbers for the hull, especially for a dinghy designed for mass-market appeal, it reminds me of a cautionary tale from my days as a young blood, not quite 40 years ago.

In the 1970's Ian Bruce followed up the Laser with the two man Tasar, a very early, ambitious attempt to reset dinghy technology. The Tasar, designed by Frank Bethwaite, was a larger version of the Northbridge Senior, a 14' two person hiking development class in Australia. The NS 14 was built at that time, in plywood to 100 lbs hull weight. Ian and Frank figured they could build the larger Tasar to 140 lbs. hull weight in foam/glass, a good 50 lbs. lighter than the Windmill class, which, here in the United States, we considered lightweight. The prototype Tasar, which I got to sail, was beautifully built in Montreal using Kevlar skins over foam core and polyester resin. Testing of the prototype showed no problems.

However, when Performance Sailcraft switched the Tasar to the production phase, economics dictated that the Kevlar skins be jettisoned and very thin glass skins substituted to keep the hull weight at 140 lbs.. When the first production boats came out, it quickly became obvious that the thin glass skins had nowhere near the dent resistance of the prototype's Kevlar skins. Treating early production Tasars over the space of several months with, what we considered normal Laser-type usage in the seventies, (dollies were mostly non-existent) quarter size dents appeared over the bottom of the production Tasar hull, giving the hull an appearance of surviving a hailstorm. Occasionally a stray protruding nail head on a dock would actually puncture the outer skin. This fragility would doom the Tasar in North America. It would not be another best-seller for Performance Sailcraft. In his next attempt at the market, Ian Bruce stepped back and did a more Laser-like two-hander, the Laser II.

Granted, in forty years, today's material technologies for building production dinghies have improved and RS is using all the modern wrinkles to create the Aero. Epoxy resin is better than polyester. There are better fabrics. Still, thin outer skins over foam construction are more damage prone. Two or three years ago I was on the lawn at West River Sailing Club at the end of a day of racing. The A-Cat catamarans (which use similar thin skin construction to keep weight to a minimum - though they use carbon skins throughout) had been racing and I watched a fellow maneuver his A around the various boats strewn on the lawn to reach the water hose at the side of the club. In the process of turning, he smacked one of his hulls against the corner of the club house, leaving a nice dent about 6 inches from the transom. To an A-Cat skipper, this type of damage is part and parcel of owning a very lightweight, very high-performance sailboat. I'm not sure, given the intended market RS has envisioned for the Aero, that this constant danger of small contact becoming a visual blemish, lump, dent, or hollow on the hull is what an RS Aero skipper is buying into. It will be interesting to see how the introduction of the RS Aero plays out. And, I will be the first to admit, many times my predictions have been wrong.

Click here for some previous Earwigoagin posts that have featured the Tasar.

Click here for some previous Earwigoagin posts that have featured the RS Aero.

2 comments:

Tillerman said...

Good point. I must admit I am a little concerned that I might find the RS Aero a little less sturdy than my Laser. My 1995 Laser has stood up to all kinds of abuse on and off the water and is still going strong.

Talking of A-cats I did see an A-cat last year that had two obvious repairs on the side of one hull. They were exactly the same distance apart as the bows of an A-Cat are. I guess it gives a whole new dimension to T-boning?

I have seen one or two incidents where a Laser bow has put a hole in the side of another Laser hull, but that's very rare. Usually a Laser port starboard crash is bow hitting gunwale, or bow riding over gunwale and on to deck, in both cases with very little damage.

Tweezerman said...

When we were racing at CORK in Kingston, one of the International 14's took 4' of bow off of one of the Tornado catamarans. The I-14 was reaching on starboard, under spinnaker, with limited visibility. In a blink of an eye the Tornado appeared on port tack, going upwind, just at the stem. No reaction time, collision, the Tornado, obviously, got towed home, the I-14 was relatively unharmed. Mind you, this was back in the days when the I-14's were significantly beefier - what we now call Classic I-14's.