I sometimes forget that not everybody knows what I and SM are.  They are the basic language of the strength and stiffness of a beam or tube of any kind.  Any beam should satisfy deflection, bending strength and shear strength.  In a very long span, deflection will govern.  Medium length, bending will govern, and with something short, like a chainplate, shear will govern.

When I specify an extrusion like a bow tube, I typically call out the moment of inertia it must have.  The “I”.  That is a language that any mast builder understands.  I see that Richard Woods has called me lazy for doing that.  I guess in lieu of declaring an actual section size.  I prefer to call out moments instead so people can have some freedom in picking a section.  Many might actually do the job.

With a round tube, this information in an Excel spreadsheet might do the trick.  When I have more time I will post the spreadsheet.  I can only do that from the laptop.

Ok, now for SM paste in =(0.098168*((E3^4)-(E4^4)))/E3

with the sizes in the E column.  Substitute these equations  into the bold above.

For I, paste in, =0.04908*((E3^4)-(E4^4))

For area, for shear, paste, =(6.2832)*(E3/2)*(E5)

I have used these for so many years that I forget where I got them.

In the previous last issue of Popular Science, someone asked if a spaceship could be built of wood. Daniel, the resident expert answered with the boat in mind built of heavy timber and old methods. I sent him the following note. No response at all.

Daniel,

I saw your article about if it is possible to build a spaceship out of wood in the June 14 issue. It didn’t sound very promising.
You were however only looking at old paradigm wood boats.
In my design office, we design catamarans out of plywood, but way different. www.multihulldesigns.com
We use wood as an engineering material. It is always encapsulated with epoxy, and often used in conjunction with carbon fiber. Carbon fiber and plywood have very similar stretch to failure rates so work well together.
All joints are done with both epoxy and fiberglass bonds. Out of plane loads like pressure, are resisted with core materials between the plywood faces.
The epoxy coating goes everywhere so there is no water evaporation. The epoxy is self-extinguishing as we have found in tests for the USCG.
I say that used as an engineering material, plywood could be used to build a credible spaceship. In fact I am building one, albeit it will never move. it is an R-3 permitted dwelling. It is done using entirely modern epoxy boatbuilding methods; like we do on the catamarans.
See http://lunarlanderdwelling.tumblr.com/ and www.themarsoutpost.com

Kurt Hughes

Godspeed to Philip Thiel. He died last month at age 93. He was my professor at architecture school. Originally he got his degree in naval architecture at Web. I got to keep in touch with him through the Small Boat & Yacht Designers Group. Was brilliant professor. I had not realized he also recently combined tiny house with boats. http://tinyhousetalk.com/pedaling-afloat-with-phil-thiels-tiny-houseboats/

Back when I lived on the yellow trimaran, he used to pedal up on his pedal boat and we would talk.

Mika just launched his D-32 trimaran in Finland. It looks beautiful.

I just got word that a bank in Greece decided in favor of my Greek customer, GEORGIOS ANAGNOSTOU.  They decided that he can have his powercat plans for free.  It turns out that anyone can use this method to get things for free.  And I am not allowed to know the name of the bank nor of any contact person there.  I did submit proof that he he got his plans, and Paypal agreed with me. It turns out however that any local bank anywhere can have the final word.   I was curious what their threshold was as I provided proof that he got the plans.  What else would it have taken to have gone my way?  No way to know as the bank is secret.  You would think if you get robbed, they can at least let me know who the accomplice is.

Paypal leaves designers and other merchants completely unprotected. Many of you have given me suggestions about what hard-case methods other designers use. I hoped it would not come to that. Paypal told me the only possible recourse I have is Small Claims Court. I assume he would laugh at the judgement against him.  Again I urge people not to use Paypal on the website for now.

Interesting former stations on this cat build. What are all the holes? Notice nice examples of different foam densities for different loads, and wide planks on the flat parts.

Here is a carbon fiber hinge, built by Russ Brown, that I got to touch. It must weigh a couple of ounces, and be at least 4 times stronger than A36 steel. Of course it makes no sense as carbon is most useful for deflection driven parts. But you can prove that you are one of the cool kids with these. These are like the chocolate chai caramel vanilla hazelnut white mocha caramel sauce classic syrup mocha cookie crumble frappuccino of coffee drinks.  These are the definition of yuppie.  What do you suppose they cost?  $100 each?  $500? I wish I had some.

I got to catch up with old friend and boat building legend Roger Hatfield today.  I had one insight before the meeting.  I often am critical of shoddy designs and/or shoddy engineering.  I have heard it put up to resentment or something else.

Be clear, I have probably lost more jobs to Roger than anybody else.  But he does great work.  I have never seen anything to be critical of. Thats the difference.  He is in town working out the build of a new Bieker 50′ something cat.  The design fee will be at least $100,000.  And I hear so much whinging about my design fees.

OK I have not had chance to update plans prices yet. Its been all week on plans support.
Next week.

I was sent this link for less costly foam core. It is in UK so not local for many people. And the range of sizes and densities is minimal. I have not yet studied the data. Maybe someone has experience with it.
http://www.easycomposites.co.uk/Category/Core-Materials/Closed-Cell-Foam-and-3DCore.aspx