I forget who gave me this now. It was a few years ago but looks still relevant. I put it in exactly square…..
Monthly Archives: March 2012
All I do anymore is email. Am going to try to hide out next week and do design work. Understand if I keep the email replies brief. And please just tell me what you want and how you want me to accomplish whatever it is.
Estonian Powercat
Nice write-up about the Estonian KHSD 44/46 powercat in Multihulls world. http://issuu.com/multihulls-world/docs/mhw123/search?q=p32 Enter the search word “arteran”
And at http://www.artcat46.com/en/
I have mixed feeling about this. It looks beautiful still. They have added so many goodies downstream that the payload is now close to zero. It began as an efficient green power cat for ocean voyaging. The mission gradually crept to being a party barge and filling as much of the space between the bow and and transom as possible. I often see this in people new to catamarans. Instead of declaring a cabin size and letting me put the right size of sled under it, they pick hulls first and then expand to fill up the “wasted space”. Up high are the worst seats on the boat in waves. It has now become a flat water vessel. And will surely trim aft. Discouraging. Maybe I know nothing about the market and it will sell like crazy.
Alii Nui Construction and Launch (2)
Alii Nui Construction and Launch
When I sailed on the 65' Alii Nui they had this great brochure on board. I finally scanned it and got permission. A kind of big pair of scans, but worth it.
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Why Boards instead of Keels
I am a big advocate of boards instead of keels on multihulls. I understand the preponderance of production multihulls have keels. And boards can mess up the interior. The big deal, I think, is the greater lift that a board generates. When I got new computer a while ago, I had not gotten around to downloading Dave Vacanti’s Loft 97 foil creating program again. He has a free demo of it. I urge you to compare keels to boards on your own.
Keep in mind that nothing else will push you windward except lift.
See http://vacantisw.com/ Go to the free downloads.
For example lets compare 16 square foot foils. Same foil family, NACA 00. For simplicity, no sweep.
Assume a board with 2′ chord and 8′ draft. At 5 knots the board generates 800 lbs of lift. At 20 knots, 12,000 lbs of lift.
Next, a keel of 2′ draft and 8′ chord creates 120 lbs of lift at 5 knots, and 2,400 lbs at 20 knots.
Now look at a common 1′ deep keel. At 5 knots, 35 lbs of lift. At 20 knots, a mere 550 lbs of lift. People. Again, nothing else will push you to windward except lift.
And as I tell my catamaran customers with keels, take a cell phone with a marine towing service on the speed-dial. If they run aground, a mono can kedge off of the mast and get free. A trimaran can chase everybody onto the ama and get free. If the tide is going out, a cat with keels will spend the next several hours there. Period.
Finally, if you stuff it up on a rock, with a keel you must haulout to fix. With a board you can keep sailing as you repair the board.
Sierra Cloud (again I think)
Doing the Sierra Cloud USCG upgrade today. It's been carrying passenger
s on Lake Tahoe for 24 years now. Still a beautiful boat on a beautiful lake. And it is the boat that changed the way that the USCG certifies cats. It makes me tired to read all the structural calculations I had to do to convince the coasties that plywood/epoxy was not bogus.
See http://www.awsincline.com/sierra-cloud-catamaran
Missing the MACMs
Usually this week of an even year I would fly to the Marine Applications of Composite Materials conference in Melbourne, FL. All the best and latest in marine composites was there. Just about any question you could think of to do with composites was examined there. Things like comparing cores, resins, and various fabrics. Things like impact comparisons, of all the previous list. Comparing the various composite joins. Even my paper on comparing w
ing masts, one with a center spline to one with only bulkheads. Reichard was big on composites testing. Despite what Kelsall says, I say testing is the best way to sort out complex composite issues, with the number of variables controlled, so the issue can be isolated for study. I met great people there. I only ever saw one other present multihull designer there (my friend Roger Hatfield). I'm sorry to see these valuable conferences stop.
Spherical Bearing Source
I understand these are the leading choice now up in Anacortes.
assignment help
r.com/ULTRACOMP”>http://www.tstar.com/ULTRACOMP
Anyone have any others, add here.
