Lock Crowther Kraken 25 Trimaran.

Marc.
The answer is the C class trimaran never caught on.
C class remained as Catamarans only.
Lock had a very successful A class catamaran.
With a wingmast designed by Lock, it was called the Typhoon.
Only three were built to my knowledge. One of them raced in the USA "A" class championships in Florida in 1973. It won all three races on both elapsed and handicap times, sailed by Ian Turner, an Australian sailor.
I'll see if I can find a pic of it.

 

Kracken 25 Plans

Hi, Old Sailor from another Old Sailor PLEASE PUT ME ON THE LIST Kind Regards Ed

 

Here is a pic of the Crowther Typhoon "A" class cat.

 

ED.
What list do you want me to put you on. ??

 

Kraken 25 Plans

Hello, I came across a Post for the availability of Kracken 25 Plans, may have been an old Posting? as seeing Plans for Kracken 25 I probably jumped straight in immediately if so please accept my apology Regards Ed

 

Ed

This is one of the most user friendly sites I have ever seen.

 

Corley,

Thanks for the comments. I'll look for the Crowther biography. Do you have any other pictures? There is only one that shows up when you search for Kraken 25. Any idea what your boat weighs?

Marc

 

When we weighed the original hulls and crossbeams they were about 140 kg assembled and an additional 50 kg in rig, fittings (it has a bronze winch!! weighs a ton) daggerboard and rudders maybe another 20kg in sundries. So about 210 kg original weight pretty good really for a boat from 1962

I've had a carbon wingmast section designed by Chris Tucker Marine Design to substitute for the quite heavy aluminium mast should make quite a difference to the dynamics of the boat as the very fine hull can hobbyhorse a bit in chop and I'm sure the weight of the rig had a role in that characteristic.

The new main hull I'm building should save about 30kg on the original weight I'm going to have a single layer of undirectional running longitudinally to help stiffen the boat but you could do without and save a bit more on the weight budget. And advantage of the rocker the boat carries is it gives a lot of reinforcement to help with rig loads etc the hull is very stiff in the vertical plane.

 

Corley,
What is the section size of the new carbon wingmast?
I have always wondered about building a wing mast like the A class above. Does anyone know any details about the construction? I know they cannot be treated like a rotating beach cat mast, but I still have an itch to see how well one worked.
Another idea I have never seen used for stiffening a tri or cat hull. If you constructed a piece of rigging inside of the hull that looked like half a set of diamond stays, you should be able to preload the hull to put the deck in tension (or less compression). When the rig loads the hull to be bent upward at bow and stern, the internal wire rigging would take a significant portion of the load, meaning less deck strength required.
Probably has a fatal flaw, I would be interested in anyone telling me what it is.
Do you think you need the very long dagger board? My old Tornado seemed to do well with much shorter and smaller area centerboards.
Will you be sharing construction photos?

Marc

 

Yes. that mast was made of Airex foam, glassed inside and out, with Airex internal ribs and no internal spar. Stressed skin construction, designed by Lock Crowther and built by Canadian Multihull Services.

The Airex was laid in a female mold made of 19mmsq wood stringers, on female formers. It was glassed inside with glasscloth and epoxy, moulding one side at a time. The foam ribs were glued in place and the two half shells were epoxied together and glassed on the outside. A wood block was set in the foot to accept the mast pivot. A boltrope track was epoxied into the trailing edge to accept the luffrope of the sail. Another block of wood was epoxied in at the hounds height to accept the swivel for the shrouds. The sail was loose footed and the mast had a small block and tackle control attached to the aft of the foot so that the mast could be accurately rotated to match the plane of the sail luff.
To enable that alignmet to be judged a 300mm long wire stuck out of the front of the mast, half way up. This wire was bent down at the tip and had a tell-tail hanging from it which showed the fairness of the airflow relative to the LE of the wingmast. This is what made the whole setup so fast, particularly to windward. The wingmast was very light, but incredibly strong and had a lot of "flotation". When Dave Boulter capsized it one time he simply walked up the mast to the rescue boat, then pulled and lifted the mast until the cat was on its feet again.

 

I wrote a detailed reply but the internet gremlin caused my connection to drop when posting, anyway it's a relatively conservative wingmast the section is 165mm x 75mm I'm going to fit spreaders as per the original plan for mast section tuning purposes if you would like a copy of the plan contact Chris Tucker at ctmd.com.au it includes the scantlings for the mast and a basic section layout.

The idea you describe has been implemented on some multihulls Lex Nicol used similar stressed aluminium spaceframe components in some of his 10 metre trimarans the benefits dont seem to be there for small boats because you want to have a minimum skin thickness for general operation and getting the boat on and off the beach, better to make the skin stiffer on small boats really.

I'd stick with the existing depth of the daggerboard these boats had great upwind performance due to their low windage and high righting moment the deep daggerboard works well you might look at the section size though and choose a less draggy naca section and also construct the board out of something lighter maybe endgrain balsa with a glass skin.

 

My dad was digging among his old photos and found this photo of Kraken with Hugh Crowther on trapeze and Lock Crowther at the helm on Port Phillip Bay.

 

Great pic Corley.

 

Nice picture, thanks.

I assume the 25 would fly the main hull? I don't really have any idea if Crowther's later philosiphy of having the amas with less than 100% displacement - for safety - was on the Kraken. In my experience, beach cat sailors would gladly trade safety for speed.

!00% - anyone know?

Marc

 

the amas are less than 100% the idea being on this little tri that two sailors on trapeze are enough to keep the boat on her feet if your not prepared to get on the wire then I wouldnt recommend you build the boat.

I can remember reading Lock saying that he had experimented with recovery from 90 degree knockdowns (by towing the boat over) with his small krakens succesfully so there is quite a bit of safety margin there. On a little daysailor boat like this small amas are not a bad approach Chris White uses them succesfully on his discovery 20 as well.