Showing posts from February, 2021

Theoretical power for flight

  I want to look at the potential energy a glider loses in still air as a way to think about the power needed to power level flight.   Imagine we make a glider and add weight so it has our total expected airplane mass.  Then we can measure the speed and glide slope and estimate how much power it will need for powered flight.   The potential energy is m*g*h.   Mass times gravity times height. power = energy/time For a glider the interesting information is:     m = mass of the glider     v = velocity = airspeed     l/d  =  lift divided by drag = glide ratio = forward distance / down distance     GlideRatio = AirSpeed/SinkRate       g = 9.8 meters/second^2     SinkRate  = v / GlideRatio = how fast glider is loosing altitude           TheoreticalPower = m*g *  SinkRate     watt = joule/second = 1 Kg * meter^2 / second^3     Lets do a concrete example with:          m = 1 Kg          v = 7 meters/second        (about 15 mph)         l/d = 10         TheoreticalPower =  1 Kg * 9.8 meters/sec

  I found a site called that has plans you can use on a 3D printer to make airplanes.  It is interesting to see how heavy each of the designs is and the wingloading.  There is a video of someone printing and assembling one of these planes.   Also another print and assemble video where it took 72 hours to print. It seems like more work than our "CNC to cut foam frame and then cover" approach.   The 3D printer makes lots of small parts that then have to be put together.  I hope to build up a collection of plans that people can use on a CNC to cut foam for making an airplane.    I think we can make planes that are lighter and more durable with our approach but we will have to get some flying before we can say for sure.

Watts per lbs

  The 1903 Wright Flyer was 605 lbs without the pilot.  It flew on 12 hp.  If we use 750 watts per hp that is 9000 watts.   If we say 195 lbs for pilot the total weight is 800 lbs.   So 9000 watts/800lbs is  11.25 watts/lb.    The Wright Brothers estimated that a 1 lb crow expended 7.68 watts to fly .   In a comment to that article someone says they made a 2 lbs solar airplane that only needed 18 watts to stay in the air, so 9 watts/lb.   We would like to be able to do that. The guidlines for rc airplanes say: Less than 50W/lb - very lightweight / low wing loading slow flyer. 50 to 80 W/lb - light powered gliders, basic park flyers and trainers, classic biplanes and vintage ('Old Timer') type planes. 80 to 120 W/lb - general sport flying and basic/intermediate aerobatics. Many scale ( eg warbirds) planes suit this power band. 120 to 180W/lb - more serious aerobatics, pattern flying, 3D and scale EDF jets. 180 to 200+W/lb - faster jets and anything that requires cloud-punchin

Development Plan for Production Oriented Solar Airplane

    Introduction  See the previous post for our basic idea of using Maslow CNC to cut foam frames for airplane wings and also to reduce the weight of flexible solar panels.   This type of wing seems light and strong enough and does not take much time to make.   So we can experiment with airplane designs and not be set back too many hours if one crashes or is lost at sea.  The goal is a low cost easy to build solar airplane.  This way we can use them for patrolling.   There is a risk that if cloud cover comes they might not make it back, so we just don't want them to be too costly in terms of time or money.   iNav software We plan to use iNav as the software for the flight controller.   This can work with regular planes, flying wings, differential thrust planes, etc.   It also has conditionals that seem useful to us.   Not sure exactly which flight controller yet and don't think the rest of the design will care too much which is used. DJI Radio Link We will use the DJI FVP syste