Jim Dory has brought to my attention that my standby sources for thick walled stainless steel pipe or tubing, have vanished.
Both Tubesales and Kilsby/Roberts phones have been disconnected. They once sold thickwall rudder shaft material. Typically a pair of shafts costed as much as a new Pygmy Kayak, but you could still get them.
The problem is neither of them have pipe heavier than Sch 80. Usually I would specify XX thick. Typically my rudders are higher aspect ratio than most, so the loads are higher. I recall seeing a note last year that Kelsall specified an 1/8″ wall thickness in a rudder shaft for a multi of around 40′. I noted that such a shaft would survive for a few minutes on one of my boats. I forget what he replied.
Another choice is to use high strength stainless Aquamet prop shaft cutoffs. They are heavier being solid, but with such high properties the shaft diameter can be smaller. I can run E x I spreadsheets for anyone needing that.
This does make carbon tubes more attractive, though cruisers will still find the less fragile nature of stainless better. And stainless does have almost 3 times the deflection resistance or modulus of carbon. I recall after multihull guru Mark Evans did a 90 degree sudden turn on the Geko, at about 25 knots, we were still fine. I later discovered that the shaft had deflected so much that the glass halves of the rudder skin had sheared against each other, on the trailing edge of the rudder. The carbon shaft had no problems.
On the big boats I got a surprise that I did not expect. A rudder shaft on one of the 65′ daycharter cats was 3-1/2″ diameter with 3/4″ thick walls. It passed all the calculations for years of service. However, when the rudders were turned, a blast from the props being pushed by a pair of 550 hp Cat engines pasted them back. I did not see that coming.
So, in summary, if anyone knows of a source for thick wall stainless tube or pipe, let me know and I will post here.
I have long known that Owen seems to know just about everything that is happening to do with multis. It seems that about half of everything here originates with Owen. And as an aside, he is building one of my Formula 40 trimarans.
I urge everyone who can to follow Owen at the Multihull Appreciation Society over at Facebook. If you want to keep up with everything. Here I lean toward KHSD news and things that might help my guys.
The new 45 cat was designed on the laptop while I was out of town. That has some limitiations, including that none of the later versions of Microstation can do trimming of objects reliably. I have an old SE version on the workstation that can trim anything. Anyway it is good to have all the horsepower to work on it. I hope to get it into study plans over the holidays. The story is in an earlier post.
Thanks to David. Sad end. That looks like starboard side ama. Must be a bulkhead there. It was double diagonal planked.
Recall that Larry always had a large board in the boat.
Funny story about that. I just today see that the CSK cat Imi Loa is for sale. I recall Larry mentioning that back in the old days Imi Loa was going to do Swiftsure. The owner was bragging that he would beat Invictus. Larry asked, “Did I hear you say you don’t have any boards? You won’t even finish on the same day.” And they didn’t.
At lunch with the guys at CSR I learned that Invictius went on the rocks up near Everett. It did make it ashore and is being repaired. I saw a picture of a giant shark bite out of the keel area of one of the amas. Larry was not driving. A Mr. Southerland owns it and gave it a snappy paint job.
Crewing on Invictus was a kind of rite of passage for many in the PNW. Larry designed and built it and has been racing it since the 60s.
I will get more details and pics of the repair.
Below is in happier times.
Its the first KHSD Dragonfly. 60′ in foam/glass. Cruising the Pacific.
A note from yesterday. “Back in SavuSavu after a 500 mile out and back to Futuna to restart our clearance into Fiji. Good sailing both directions and great hospitality in Futuna.
Futuna is a department of France and many of the men were wearing their flowered leis. ”
The local Seattle formula 40 catamaran Dragonfly capsized during the Cow Bay Regatta. Not my design. It was originally from New Zealand and was originally named Simply the Best. It’s owner Pat is one of the best sailors I know. I hope to find out more soon, but I was told that it rolled over on a reach after stuffing into a kelp bed. It was a heavy air day. If it could happen to Pat, it could happen to anyone. I see the boat is on the hard in Everett, sans mast. Pic is on happier days.
Kurt Hughes on Catamarans, Trimarans, and Boat Design