OK almost two weeks ago. Been busy. Everybody has a deadline.

The Fish Expo was mostly the usual stuff as before.  With the internet, it is not that important to get the literature now; just the links.

I did find some more composite bearings for both rudders and unstayed masts.  Should be much less cost than machining plastic.  And I’m game to try Rob Denny’s idea of using sloppy fit instead of spherical bearings.  Duramax.

This week will be tough on deadlines.
The dome acrylic project on the lunar lander dwelling came up two short. It seems the fabricators misunderstood the number 20.   The VHB tape is all ready in place on the dome.  The missing two panels must be installed as soon as possible.  I have a small weather window for tomorrow and wednesday there. Then Thursday is gone. I will be back in full next week.  This does keep me involved with all aspects of composite building, which benefits you the builders.

I just was given the digi pic of the launch of the first boat I built. Launched Oct. ’78. Hulls then were Piver AA31. The rest I adapted.  it got new CM amas in a couple of years, among many other things.

Not actual boat but boat construction.  On the lunar lander dwelling, my house built like a boat, I had planned to use the 3M VHB tape to stick the acrylic dome panels down.  I had understood that better results come from using an adhesive promoter in this cool time of year.  Uline, my tape supplier would only sell me large quanties of it.  I now now their minimum was enough to do about half a kilometer of tape.  Devon at 3M only had one idea of who in Seattle had some to sell, and they did not actually.  I had given up and went to Fish Expo.  At the Fisheries Supply booth there they had a 3M catalog.  Fisheries carries not the exact same AP111, but close enough, Tape Primer 94.  Fisheries comes through.  http://www.fisheriessupply.com/

This prime example of stuff done wrong was sitting right in front of me for a few days before I grasped the teachable moment in it.  And it is another example of what I have often seen where it is asserted “it must be right because they are famous.”  In today’s chapter, first the boat.  The bow broke off of this 50′ (I assume) trimaran in the Route de Rhum.  I have not seen the actual wreckage nor spoken to anyone who has.  But it seems like a lot can be understood by looking at these pictures.

Two things jump out immediately.  First, that sure looks like Kevlar, and second, the core looks thin.  It could be 19mm but it sure looks more like 12mm.  And the damage is quite clean, not ragged.

First, Kevlar?  Really?  In my opinion Kevlars’ only use is as a yuppie magnet.  Not only does it not actually stick to the resin matrix, but its compression strength is about 1/3 its tensile strength.  And it’s tensile strength is still 20% less than that of lowly E-glass. 

Now notice at the 3 corners of the hull section are tiny carbon fiber stacks.  That is bad practice on at least two counts.  First, the carbon has less than half the stretch to failure of Kevlar, so the carbon must fully fail before the Kevlar’s tepid strength is even at 50%.  Next, if it is a carbon stack as it looks, with the differing stretch, it could pop off the Kevlar with a shear failure. 

The clean break feels more like a tensile failure instead of buckling at first glance.  I see a scenario where there was a partial buckling failure which popped the resin matrix off of the Kevlar in a circumference line.  Later that weakened fabric is hit from the opposite direction and fails cleanly.

Why didn’t they know all this?  I can think of an elderly designer or two who would not know this kind of thing, but it has been out there for a long time.  Next, the Multi 50 rule is just as bad.

Spotted nice pic of Trilogy IV. It was built by Kevin Millet and began as Hula Girl. 48′. Foam/glass. 49 pasengers.  I think I designed it in mid 90s.  On Maui.

Once again it is time for Pacific Marine Expo, (formerly known as Fish Expo) in Seattle.  Again, this is the serious boat show.  Or you could go to METS in Amsterdam.

I came across this long ago pic of my 56′ Aero rigged cruising cat Sarabi when she was visiting Mexico.

One of my new builders just read the 220 page plus construction manual. He once met one of my earlier builders and says “”Now after reading your manual I understand how he (Thomas D) was such a know it all (in a nice way.”

Smiles.