Build a hang glider, slightly larger than standard, with two layers of black solar collective material for the wing. If the volume of heated air contained within the wing is equal to the amount needed to lift you off of the ground by a solar hot air balloon, then vertical take off in a hang glider could be done from ones own back yard, (I've got this phobia about jumping off of cliffs).

Once a reasonable attitude is achieved the pilot can open valves which release as much or as little of the hot air as is necessary to begin soaring.
By giving the pilot control of lift the only thing forcing you to land is sunset.
-- 2 fries shy of a happy meal, Feb 26 2005

Solar hot air balloon. http://perso.wanado...olaire/en-index.htm
DrCurry's link to another idea. [2 fries shy of a happy meal, Feb 26 2005]

reminds me of this one... http://www.bestpric...23IE?source=froogle
[po, Feb 26 2005]

(I've got this phobia about jumping off of cliffs)

No shit,me too +
-- skinflaps, Feb 26 2005


slightly larger than standard... volume needed to lift you off the ground.

This is a biiiiiiiig hang glider. [+]
-- david_scothern, Feb 26 2005


Even with an outsize wing (perhaps 1000 cubic feet of air, which would be a big thick wing, as [david_s] points out), and with good solar heating, you'd only get a few kg of lift - less than the extra weight of the larger wing, I think. Even hot-air balloons need burners to get the air hot enough to give sufficient lift, and their volume/payload ratio must be much much higher.
-- Basepair, Feb 26 2005


Not necessarily true [Basepair], see link.
-- 2 fries shy of a happy meal, Feb 26 2005


Well really, [2-fries] - if you wanted people to follow the link you should have given it an obvious title! ;-)

I am impressed, but it's still clear that a flyable wing wouldn't have sufficient lift, alas.
-- Basepair, Feb 26 2005


I don't think it clear at all.
If the volume of hot air is sufficient for lift, and if the wing is aerodynamically shaped this will work, it will just have a very large wingspan.
-- 2 fries shy of a happy meal, Feb 26 2005


Not necessarily. If you try to make a very long wing (long enough to have the same volume as the man-lifting balloon), you need a lot of framework to keep it tolerably rigid. Admittedly, airships have a rigid frame, but (a) they are not as long and thin as a wing - they're not long cantilever structures; and (b) they need helium to get useful lift (helium has a lower density than manageably hot air, I think). What I'm getting it is that I don't think you can make a lighter-than air hot-air balloon with an aerodynamically stiff wing- shape, however you scale it. ***However***, I'm not trying to pick holes, and I may be wrong. Tell me the dimensions of the wing you had in mind and I'll take it all back :-)

Is there an engineer in the house?
-- Basepair, Feb 26 2005


I think there are a few engineers in the house but I am not one of them so I have no numbers for lift to weight ratios.
It's size would be roughly bigger than a bread box yet smaller than a Cessna.
-- 2 fries shy of a happy meal, Feb 26 2005


A quick calculation. Suppose your glider is the same size as one of the wings of a Boeing 747-300 (one wing is about 90ft long and maybe 18ft front to back and 3ft top-to-bottom, as a rough average). If completely hollow, it will hold about 180 cubic metres of air, give or take. Suppose that you can solar- heat this up to the boiling point of water (100°C), and that the outside temperature is freezing (to give you the best lift). In this case, the wing will give a "hot air" lift of about 62kg. Even a hang-glider weighs ?30kg?, so a wing which is five times longer is going to weigh easily more than 62kg. Hence, even a wing this size is not going to be self-lifting in a balloon kind of way. Sorry, not getting at you - just an interesting idea and I was curious about the numbers.
-- Basepair, Feb 26 2005


Well that sucks, I thought for sure that this would be the one idea that finally made me rich.

[Po] May I please ask you to explain that link? I really don't see any connection.
-- 2 fries shy of a happy meal, Feb 27 2005


:-( sorry. If it's any consolation, the President of Boeing corporation probably *is* rich, but is probably unhappy. Well, maybe.
-- Basepair, Feb 27 2005


So it is basically a solar heated hot air balloon?
-- travbm, Oct 29 2015



random, halfbakery