As I face the prospect of disassembling my trimaran, I am reminded about the most important thing to do with installing any hardware with epoxy. And I hope to find out that I kept this in mind when I built Geko. MOLD RELEASE
Every fastener set into epoxy should have already had mold release was rubbed into it and buffed. Or even green soap. New builders don’t believe it, but much of your hardware will move or be replaced over the years. And I will admit perfidy on this. The evidence is when is forced to use the battery and jumper cables to heat the fastener. Mold release!
Ok I’m still mumbling about the top level house on my 65′ plywood/epoxy passenger ferry being more like would be found on an 85′ cat, but I’m impressed. It sits well on the water and looks to move well. I can start breathing normally again. It should be the first of 10 vessels. Rob is a visionary.
I took a deposit on my boat. Will miss the zen of single-handing at 25 knots. Or passing F boats. When the prime directive becomes “don’t break anything”, the racing becomes less fun. New chapter, if it goes ahead.
I was stumbling around looking for photos for the new composite construction manual. Found this picture from 1980. My first boat. 31′ then. Tim Ryan steering and Dennis Hough on sheet. Hat Island race. Courtesy John Marples.
I always have the notion that I am the only person who ever reads this blog. Matthew tells me however that it is gaining about 20% every month. And it just got a nice write-up in the French Multihulls World magazine! Thanks everybody. I have a list of interesting upcoming topics that I will do.
This new 20/21 foot shuttle cat has begun production at Zuhai, China (near Macao). It is especially intended as a chase boat for rowing teams or as a mini shuttle. Unit #1 has a bit taller cabin than designed.
One of the rules of plastics is that they all degrade in sunlight. The nets on my 40′ x 36′ trimaran seem to be the exception to that rule. My Net Systems knotless black polyethelene nets have been flawless for some 15 years. They do need to be tightened every season.
I give them the leap-off-of-the-hull onto them every so often to impress the crew. I recall the failure point some years ago during the Shaw Island Classic when Mark Evans leaped into the net. The cast padeye holding the net exploded. Many thumbs up on this product. http://www.net-sys.com/catamaran-netting.php
Not all the sets have this yet, but according to people who use this detail, it supposed to be the best way yet to attach a window to a boat house. I have a PDF of it also that will be added when I get a chance. Or I can email it.
Its kind of a mini Sarabi.
We just got the bids in on the new carbon fiber unstayed mast for Alex’s KHSD 45 catamaran being built in Blaine, WA. It is what we call an aeroesque mast. Same general idea as the aerorig, but updated.
I’m sure the safety of these masts will make them the future of USCG certified sailing cats. The Coasties just need to see the FEA study to accept them.
Every couple of years I have someone ask me why my cat designs need to have aft beams. This occured again last month. They seem to have the tone that there must be a structural secret I just have not figured out yet. I did just get this picture. “Why can’t you do a beam like this? Ask them how they did it.”
People. Remember where I always say “with enough carbon and enough money, you can probably do anything you want to.”? There are limits. They probably think a sleek cat beam looks like this.
It actually looks more like this. The boat salesmen hide a beam like this so it will look thin or even gone.
That is compared to a standard beam. Like this…
So why don’t I catch up and do the flat beam? Remember how I always talk about efficient cats? Look at this.
The tools we designers use to compare beams are the moment of inertia “I” and section modulus “SM”. (assuming shear is satisfied) Suppose the regular beam is 12″ x 36″ by 0.1″ thick laminate. That regular beam has a SM of 99 in^3 (inches to third power) and a moment of inertia I of 2104 in^4.
In the horizontal mode beam, it only has a SM of 44 and the I is only 272 in^4. To get more strength and stiffness it must be made thicker and heavier. Even if the horizontal beam laminate is made 7 times thicker and 7 times heavier, it only has the same strength as the regular beam and still only a third of the regular beam’s stiffness. The flat beam boat vendors hope you don’t know or care enough to appreciate the difference. They can’t claim efficiency and still have horizontal beams.
Kurt Hughes on Catamarans, Trimarans, and Boat Design