We Are Not A Mused

I have enjoyed the progress and popularity of Web journals or blogs over the last few years.  This technology and form of communication just exploded onto the scene.  The technology seemed to lead adoption, there are still facets to blogs that very few blog authors have even heard of.  It is indisputable that blogs, along with Wiki publishing and social network publishing, are well established and common in the Web now.  I've enjoyed reading and writing blogs.  It's great that so many people have published so much information.

The prolific invention of new kinds of Web publishing, which continues unabated, contributes to the vibrant, nonstop nature of the Web.  You would think that in a mature technology like the Web, everything has been invented and reinvented a million times over.  But sometimes when you look around, you don't see the sort of things you expect.  In my case, I'm looking for some simple solutions for simple needs.  I created the SimpleBooks system for Web publishing for a very simple and direct need.

I'd just like to publish Web pages, mainly HTML with styling, on my Websites.  I'd like to write the material in HTML files using an HTML editor (and there are lots of those).  I'd like to start up an FTP utility and just copy the material to my Website, which should pick up the new material and publish it without coding, reprogramming, or having to deal with a database.  My first effort at this sort of publishing, the SimplestArticles system, did much of the job with only 14 lines of code.  But it published from only one directory, did not supply title text for the articles, and could not handle much customization or organization of the material.

So the next step was to create SimpleBooks.  If you want the details, click through to the writeup.  That writeup is actually hosted using the SimpleBooks system, and it has a link to a sample Visual Studio 2008 project for SimpleBooks.  SimpleBooks is a proof-of-concept (OK, it's a demo for the ideas), so don't expect fantastic coding or visual styling.

-- Walter Lounsbery, 8-17-2008

I'm trying to log on to the Microsoft Developer Network subscriptions Website this afternoon, and it appears to be down or inaccessible.  My login is rejected.

Could this be due to the release of Visual Studio Service Pack 1 today?  The effect of over 10 million developers trying to get the latest bits at the same time?  I guess we've found the limits of MSDN.

-- Walter Lounsbery, 8-11-2008

As I write this, I'm painfully aware how developers (and I are one) can overthink the "user interface".  When that happens, perhaps it should be called the "hardly usable interface" or HUI for short.  In many cases we can even code things to think for the user, or keep that user from doing something "dangerous."  That is absolutely true for a few "features" of this wonderful tool I am using right now, Windows Live Writer.

In my last blog post, I tried to include some highly relevant and important graphics.  I didn't realize that WLW thoughtfully resizes your graphics according to mysterious settings hidden from operators astute enough to check the menu Tools/Options selection.  It is too bad that the clock was running late so that the crappy graphics produced by this wonderful bit of overthinking actually got published.

So here I make an attempt to publish those graphics in the size and legibility they deserve:

-- Walter Lounsbery, 8-7-2008

About 15 years ago, I started my first homebuilt aircraft.  I ordered the plans for the KR-2S, anxious to start construction on a homebuilt aircraft and just a little upset that I could not find a home for my Piper Cherokee.  I had moved from Fort Worth, Texas to Savannah, Georgia, and there was no space to park my plane anywhere near Savannah (at a price I could afford).  I had to leave the Cherokee in Texas and sell it long-distance.  It seemed to me that, by the time the KR-2S was ready for an airport, that detail could be taken care of.

Sad to say, my new job in Savannah had lots of overtime and travel.  Other events kept me from starting that construction project.  Here I am ready to start building something much later than I planned.  In the meantime, I also find myself flying in the relatively new Light Sport Aircraft/Sport Pilot regulatory arena.  Regulations that exclude aircraft such as the KR-2S.  Well, I always wanted to design my own plane.  Given how long it took to get started, I'd better get busy on this.

Designing an airplane can be like herding cats.  You may know what you'd like, but there are all kinds of factors between a rough sketch of a sexy-looking airplane and the decisions behind a materials list, drafted design drawings, and that first flight.  With United States experimental aircraft (amateur built) there are few limits.  You can design helicopters, jet packs, aircraft with props or jet engines or turboprops that carry one person or a dozen.  An airplane can take off of water or a runway.  There are a world of choices.  If you want to build a landplane Light Sport Aircraft, the boundaries are a bit more restrictive:

• Maximum gross weight of 1320 pounds (600 kilograms)
• Single reciprocating engine (no turbocharging or boost)
• Maximum of two people onboard
• Unpressurized cabin
• Fixed landing gear
• Maximum altitude 10,000 feet above sea level
• Fixed or ground-adjustable propeller
• Maximum speed of 120 knots calibrated airspeed (kcas)
• Stall speed of 45 kcas or lower, no flaps

The last two items are very significant.  In fact, the top speed governs how much engine is legal and practical.  The stall speed governs how much wing is needed.  Unless the wing design is unusual (compared to most light aircraft) the maximum weight and the stall speed should dictate just about the same wing area for all LSA.  This is a reasonable conclusion that actually doesn't work out in reality.  First, let's go through the arithmetic and select a wing area for the LiSA 2 (named after my wife, Lisa).

Lift of a wing depends on only five factors: wing area, wing airfoil, dynamic pressure, angle of attack, and wing geometry.  Dynamic pressure (q) is directly related to the calibrated airspeed, V_e:

In this equation, the velocity is in knots and the dynamic pressure is in pounds per square foot.  If the velocity is doubled, dynamic pressure increases by a factor of four. 

Of the five factors, lift is linear in wing area or angle of attack.  If we use fairly conventional rectangular or tapered wings, the geometry variations don't change lift with angle of attack much and shouldn't have much impact on maximum lift.  So dynamic pressure is a big deal since it varies as the square of velocity.  In fact, due to the LSA stall speed and maximum gross weight requirement, it is the most significant factor in sizing the wing area for the aircraft.

Stall of a wing occurs at its maximum lift coefficient.  While that number can vary dramatically depending on a variety of high lift treatments, when we work with plain wings of fairly conventional aspect ratio and geometry, without flaps, then the maximum lift coefficient is fairly constrained.  Here are examples of production aircraft, based on published data:

The first two aircraft have rectangular wings, which are less efficient at maximum lift.  The Cessna 150 has a tapered wing and airfoil that is better at producing maximum lift.  The Cessna 172 is the oddball of the group, since the wing design is very similar to the Cessna 150.  My opinion is that the stall speeds I was able to find (and many sources didn't agree) are wrong.  From an aerodynamic perspective, the two-dimensional maximum lift of the Cessna wing airfoil is only about 1.5, which must be greater than the lift of the actual wing due to tip losses and other three-dimensional effects.

Now, if you believe anything you read (just think, you are reading this too!) the next table is going to really confuse you.  How can the following 10 LSA aircraft be so different in stall performance?  The Challenger is a bit of a ringer, since it stalls at much less than 45 kcas.

Confused or not, clearly the wing area has to be big enough to lift the aircraft at whatever maximum lift coefficient you think the wing will be good for.  In other words, it's got to lift 1320 pounds at 45 kcas, pick a maximum lift coefficient and you've got your wing area.  That's what gives the following chart:

I'll design the LiSA 2 for a wing stall lift coefficient of 1.45, giving a wing area of 133 square feet.  In my next post I'll try to cover the influence of span loading on induced drag, or why I picked a 33 foot wing span.

If you dabble in aerodynamics, you've realized that I've just sized the wing without even picking an airfoil.  The airfoil choice really comes from a number of other more important factors that I will cover later.  For now, I'll include a spoiler for my initial airfoil choice, as shown in the Airfoil Optimizer program by DaVinci Technologies:

-- Walter Lounsbery, 8-4-2008