CM Female mold

For a few decades now I have considered rapid composite hull building construction to be the holy grail of boatbuilding. I published and presented a technical paper on this topic at the 1992 Marine Applications of Composites conference. I built the hulls for my Formula 40 trimaran using the same techniques. A few other catamarans have been built using these techniques. I never have had time to properly write this up as a manual.

I’m still not sure that there is any need for rapid construction any more. I just saw a picture of a race starting line with a row of $3 million to $5 million cats racing. Maybe I really miscalculated the business. Oh well, too late now.

The only other multi designer that I know of working the problem is Kelsall with his flat bagging table KSS process. I see an armload of problems with it.  Besides, with that process, one still has to torture the laminate into shape,  cut darts into it, then add the 0 degree laminate over the darts, still. And fair it.

What if you could instead build a rapid female mold, and bag the exact and final hull in it in one step? Here we go.

Back in the late 80s when I build my trimaran, a couple of the steps were very successful, and two of them, exhausting. Those two I have improved on.

Those are; I coated the inside of the hull with epoxy. Then sanded it smooth. Way too much work. I now recommend using 545 or some other epoxy primer paint instead. The second was that I coved the hull “gutter” with bog, and then sanded it smooth. Even as a 30 something then, it was insanely do. Now I prefer to fit a piece of cardboard sonotube first. Then once it is fit properly, bog under it. It creates a rebate on the part that extra protective biaxial roving can be added to.

The first step is to create two cylinder molded reflected hull panels. These can be done with non waterproof glue to save cost. This mold will never go to windward. The insides of the panels are best filled and sanded smooth at the scarphs while the panel is flat like a table.

The two panels are wired together just like the usual CM hull, and a deck flange is added.

The difference between this and the usual CM is that the bulkheads are added to the outside of the hull instead of the inside. Once the final hull shape is achieved.

Red is the flange, purple, the bulkheads, and green the cardboard sono gutter.

36 Daycharter Transformer

One of my customers and friend was in the Keys and got this picture. He wondered if it was a KHSD design. I thought so but wasn’t sure. Pat cleared it all up. Yes, it was the late Chris Schofield’s daycharter cat. It was actually the bridge design between the original Kamanu 36 and the present BIB charter boat in a box 36 design.  Probably built in ’90, by Olympic Boat.


First day back and totally wasted day.
Apparently the combination of 1300 emails and being 10 days out of Eset AV updates has frozen my system over and over. It slams up to 100% CPU and pretty well stays there. I’m about halfway through the emails. Most of the spam is in French so Multiquoque must be selling me to lists.  Eset has gone on downloading for hours and the cancel update tab,  doesn’t.

Probably the only way out is to use Squirrelmail on the laptop to reduce the wave. Outlook seems to only choke on it.  Will have it sorted by Monday.

Out Next Week

I will be out of the office from M14 through M23. I will have the workstation with me and should be able to catch up on some 3D modeling.  I should have email where there is WiFi.
Anyone have any projects in Iceland or Scotland that I should look at?

Trimaran Ski

One of the fun things about this job is that I get to see all kinds of things.
Someone sent this to me asking if I wanted to invest in this big production run.  I’m always amused that the proponents of these kind of units are so certain of their success, without any water miles.

A Boatbuilder’s Tiny House

Wandering back from the post office after shipping a plan set I saw this interesting 4×4 van.     It was painted Stars and Stripes blue with Stirling 2 part polyurethane paint.
It is also a tiny house for ronin boat builder James Moreland.
Bed across the back. Galley on starboard. Office on port.  Call him if you need help on a boat project.  Hit him at 206 380 7094 if you need help on a project in PNW.
Glad to meet him.

Bowtubes and the USCG

You surely remember the broken lumber A-frame shown recently here on the 42 daycharter cat.  The owner chose to replace and update with a standard alloy tube and wire system.
My worst fears about MSC came true.
I submitted the stock, stamped, original plan sheet to MSC.  I also submitted an 2017 version with the same section properties or better.  Keys Rigging submitted the proposed with extra strength on all items.
It was rejected. They wanted the calculations also.  Done. Those were rejected until I would explain how I did my calculations. They did not have a standard to aim for. In fact I was asked to explain what the relevant factors were.  It has been almost 2 weeks of back and forth now. My fear that nothing that was settled “law” before, is now.
I have probably done a hundred of these, and I bet Keys Rigging has done that many also, or more.
I also get the feeling that they are stressed and angry at MSC. Maybe Trump chaos has hit there also.
This is one part of why no postings last week. Deadlines also. Next week will be better I’m sure.

23′ Trimaran Update

I finally got the first run of modeling the updated 23 daysail trimaran. Version B will have ama rudders and the even hotter version C will have foils. It is a developed plywood/epoxy unit with core vacuum bagged onto the flat surfaces needing that. And carbon fiber where it helps. At around 360 kg lightship weight, it can be built for around $5000 us in construction materials. The connecting beams should be carbon mast sections. The camper version comes next.





Kurt Hughes on Catamarans, Trimarans, and Boat Design