Archive for October, 2009

Over-engineering

Friday, October 30th, 2009

I now host a new section on Airglow at http://airglow.propdesigner.co.uk/ and I am about to add some photos of Abhilasha at http://pictures.propdesigner.co.uk/html/abhilasha.html some time over the weekend if all goes well and it got me thinking about over-engineering. Abhilasha is a marvelous achievement but it turned out heavier than the designer would have liked, Airglow is probably slightly heavier than it needs to be just to fly but it has been around for nearly 20 years.

Abhilasha uses standard components like standard Aluminium alloy tubing, steel bolts and plywood fittings among other components resulting in a relatively cheap and easy to build aircraft but 15 to 20 Kg overweight. Airglow uses Carbon fibre to reduce it’s weight and plastic ribs that has resulted in a robust aircraft (for a HPA) that has not deteriorated much over it’s long lifetime.

I am not sure Airglow was designed to last as long as it has but I believe it was designed with an extended life compared to previous HPAs that have had lives measured in years rather than decades and it has been used in research.

Thankyou

Tuesday, October 27th, 2009

Thankyou for reading this blog and thankyou for visiting this site and making it as popular as it is. There has been over 13,000 hits on the site according to the site’s statistics this month. The number of hits has grown steadily since the site was first created nearly 4 years ago. I get people vititing the site from Argentina to Zimbabwe but mostly from the United States, United Kingdom, Singapore, Australia, Netherlands and Japan.

Are there many people interested in human powered flight? I doubt it, there is information about a wide variety of subjects and I have to say, some people accidentally come to the site expecting to find something entirely different, for example, a person came to the site trying to find the wingspan of a Toucan and was probably rather confused to find it was 139 feet, about 42 metres, a very big bird.  Other people are trying to find information about aerodynamics, engineering and structures in general and do not care that it is related to human powered aircraft.

There are 5 references to this site from Wikipedia, one of which used to go to a non-existent page until I added it and redirect users to the correct page. There should be more as some information in the Czech version of Wikipedia is from the site.

I am pleased with the site but I will try to make the site better by adding more and relevant content.

QFLR5

Tuesday, October 27th, 2009

One of the many things I do is write install routines. I have just modified an existing install routine to intall the latest version of QFLR5. It used to be known as XFLR5 and ran on Windows only but it has been rewritten to run under a number of operating systems. I only write the install routine for Windows. The install routine for version 0.03 can be found at http://xflr5.propdesigner.co.uk/ and you can find the QFLR5 web site at http://sourceforge.net/projects/xflr5/.

QFLR5 being based on XFLR5 4.17 is a stable product and a version number of 0.03 is not as bad as it seems. Read the XFLR5 web site to find out more.

Fédération Aéronautique Internationale

Sunday, October 25th, 2009

You may not know but the FAI have a sporting code that covers human powered aircraft (Part 11) at http://www.fai.org/system/files/sc11_1992.pdf. Section 1.2.3.4 states “In the case of distance records, at some point during the flight the aircraft and crew must exceed a height of 2 m above the ground.” It makes me wonder how many HPA flights would be recognized by the FAI including many flights by SUMPAC and Puffin.

What do I know?

Saturday, October 17th, 2009

For those who don’t know, an ornithoper is an aircraft that uses an animal-like way to fly, usually flapping wings.

The University of Onterio is building a human powered ornithopter to fly the classic figure of eight Kremer prize course to prove the concept. The ornithopter is based on work on a powered ornithopter that flew once and then they had to add a jet engine. The flight lasted 14 seconds and was terminated due to lack of control.

I don’t have high hopes for it ever taking off under it’s own power but… what do I know?

Is the army interested in HPAs ?

Saturday, October 17th, 2009

I noticed the site had a visit from www.army.mil . Does this mean the US. army is interested in human powered flight? I am told that the army has some software that searches the web much like Google but it is looking for terrorist materials and links with Al-Qaeda. I think they will have to work hard to create non-existent links between what I do and any terror organization.

Tweeking the web site

Sunday, October 11th, 2009

I occasionally tweek all or part of the web site to improve them, at least I hope they are improvements. I have added links to news, this blog and the forum to the library part of the site. The gallery needs similar links adding and I will have to ask if Chris Roper would also like the links added to his book at http://humanpoweredflying.propdesigner.co.uk/.

A full redesign of the site would take some time and is not something I feel like doing just yet.

Prop Designer

Sunday, October 11th, 2009

I am thinking of adding features to Prop Designer. A possible improvement that is reasonably easy to add would be a bit on bending moment along the blade. It is up to the user to use this information to work out the strength of the blade.

I was also thinking of adding the option of entering an existing blade design and seeing how good it is. At the moment Prop Designer initially calculates the blade angle based on blade element and momentum theory.

I don’t know what features people want so I normally add the features I want.

Something that puzzed me

Wednesday, October 7th, 2009

One of the most popular searches on my web site is for the NACA 0012 and some coordinates for it. I also have the NACA 0009 section, the NACA 0021 section as well as a number of others on the site.

Pushing my mathematical powers to the limit I noticed that the thickness of these sections were divisible by 3 and I wondered why this was. The answer dates back to the 1940’s and 50’s. Aerofoil section data was hard to get and without computers or access to wind tunnels designing your own was generally not an option so you had to find a source of data. The easiest and most common source was “Theory of wing sections” with a subtitle of ” including a summary of airfoil data” by Ira H. Abbott and Albert E. Von Doenhoff. The appendicies provide a lot of data on NACA aerofoils and they are of various thicknesses all divisible by 3! This was often the source for early HPA designers

With computers it is possible to design your own aerofoil section or even take a NACA section and change it’s thickness to 10, 11 or even 11.5% thickness if you think it is appropriate.

Runways

Tuesday, October 6th, 2009

I was thinking about where the early HPAs flew and I realised while Lasham is doing well, Hatfield, where the Puffins flew is now part of campus of Hertfordshire University and Radlett, where Toucan flew, is now a housing estate.

While HPAs require hard surfaces to take off on they don’t have to be runways desiged for passenger jets but other sutable areas like private roads that have the clearance for a HPAs wingspan are not easy to come by.