I was lucky enough to be able to talk with Bryan Allen the other day about his experiences flying the White Dwarf and also the Gossamer aircraft. He lends a large dose of reality to those wishing and wanting to float over the trees in nearly silent, propelled, lighter-than-air vehicles.

Bryan mentions “Apparent mass” which I had to look up: Apparent Mass=Force/Acceleration. This term was used in reference to the fixed-wing Gossamer aircraft, which had large aerodynamic surfaces and low mass. Just because those airplanes weighed around 30 kg each, lifting or moving them by hand would have been hard because the force required to accelerate them (overcoming drag on their large lifting and control surfaces) would have been higher than simply “mass times gravity”. Apparent mass!

It is also quite illuminating to do as Bryan recommends, to compare cost-to-performance ratios of small powered flyers, from 0.25 up to 20 HP. At the lowest-power end of the spectrum, around that of human-power, a blimp is actually pretty competitive. Slightly increasing the size and the power, from the human’s 0.25 HP up to 1-2 HP, then fixed-winged aircraft start to get better. Afixing a 20HP to a fixed-wing aircraft can make you go 120mph (see Rutan’s Quickie), so having a blimp at that power-range is not really sensible to go from a to b.

(UNLESS you need the advertising space, need to crawl along the rainforest canopy, need to break the FAI world record for that class of airship, need to build the first “microlift airship”)

Filmed on March 21, 2010. Thanks to Aerovironment for permitting use of the image of Gossamer Albatross in the film.
Thanks most of all to Bryan Allen for the inspiring doses of reality!

I want to find a low-cost lifting-gas barrier for use in our flycycle. I obtained some 3-mil polyethylene painter’s tarp material which i then folded in half and whose edges i welded together with a clothing iron. i covered the edges with 3″ masking tape to protect the iron from molten polyethylene. For the nozzle I cut a plastic funnel (and my middle finger) and attached it to an open corner using hot-glue from a crafter’s hot-glue gun. Then I test-inflated the bag at Gemeinschaftszentrum Bachwiesen. What follows are a series of photos from that successful air-inflation test. No perceptible leaks were observed. The 4×5m painter’s tarp material worked out to give 16m3 of volume (idealizing the shape to a right-angled cylinder), and thus approximately 16kg of lift if filled with lifting gas.

The air compressor from GZ Bachwiesen was a custom built number consisting of a motor and piston pump.  The rubber tube fit perfectly into the funnel-nozzle of the gas-bag.

Mu ha ha ha ha it’s alive!

It gets more air….

Fully Inflated. Ready to rock and roll.

Getting the kind assistance and motivation from 8hourcustom, we proceeded to start a fabric 1/50th mock-up of the piloted craft in order to plot our our envelope-attachment points, et, cet, tera. A four-gore, canvas model of the same aspect-ratio (or close) of the end-design has been started (marked, partially cut, sewn). Next week it will be ready to assist us with the fine-planning.

Marking the gores with #2 pencil on canvas (or similar – bedsheet material).

Sewing gores.

Stay tuned. Wait till we unfurl our self-correcting ballast system for free-flights over water.