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Long range flying and what this dB stuff means.

The first thing to do is watch Kahn Academies video on calculating decibels

The video also points out how sensitive the human ear is.

P = power in Watts (W) = Work / time

Work is an energy measurement. What is energy? That’s a question which will stump pretty much everyone. The answer is probably another question. Why? Don’t hurt your brain with this one too much…. moving on.

J = Joules = an energy measurement.

Work(J) = Force * Distance

Force = measured in Newtons (N)

1N =  about 102grams * gravity

The actual formula being

F = m * a

Force = mass * acceleration

So 1 Newton of force is about half the mass of your house / car keys just sitting in your hand.

Lift your car keys 1 metre in one second. That is 1 Watt of energy.

You car keys have a footprint that fills the palm of your hand. You can feel it.

Spread that weight over 3 times the size of Germany, or for the Aussies reading this, a bit less than the size of the Northern Territory.  You couldn’t feel that with your hand, but your ears could hear it.

OK, It have to come back to this article to explain how it relates to long range flying.

 

 

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Urban Aeronautics

A very interesting video from the Vertical Flight Society.

So I was initially thinking about 2 rotors like this for Sentach except running port / starboard rather than fore and aft. The thing is that the application is different. I’d like to take Sentach out to 300ish knots for small payloads and get 1000km range. Smaller payloads require a smaller vehicle. Thus we can stay with the wing model and use VTOL not for hovering so much as just punching off the ground and not needing a runway.

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Slope test – Sentach

Took the headtracker out as I wasn’t expecting much lift today. At best 25kts (12.8m/s) at Pat Moreton. Flew perfectly, but the glide slope was not enough to keep altitude. 763g. Still waiting on props to arrive. ‘Tas heaps of drag points which could be eliminated. Could make a larger wingspan for these wind speeds.

Would be interesting to see what CFD says and how it compares to reality.

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Time to have a crack at flight stabilization

Would like to get flight stabilization happening so it’s easier to fly FPV with the head tracker initially. At least if I balls it up I can throttle off, let go of the sticks and it will have some chance of landing flat. Would also be able to see compass headings, altitude and battery on screen through the OSD.

Think I’ll start here first and see if it works with that F3 board.

Some others to look at:

http://www.librepilot.org/site/index.html

Ardupilot

Betaflight

MWPTools for navigation to mix with the flight controller. That or the INAV software.

 

 

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Sentach powered up

Put the motor in and re-balanced it. Flew at around 14:00ish under power with about a 30kt NNE (15.43m/s) for backup glideability. Flew so well. Only hit about half throttle with a 4s. Had heaps of lift, so I’d say I could max out at about 1kg payload with more throttle. Now onto a flight controller before sticking the head tracker in.

Flight weight – 1414g

New COG –  280mm from the L.E.

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Sentach glider version

The Sentach glider worked well today at the Pat Moreton park in about 15-20kts NNE. Videos to be posted shortly.

Flight weight 680g.

COG 310mm from the L.E.

Beautifully smooth flat landings. Some wobbles as expected. The’s alot of drag points. Especially with the flat sides of the nose. Don’t think anhedral would totally fix it because of the nose as it’s obvioualy turbulating when a crosswind happens.

Crashes it once and the wing popped off nicely dispursing the impact force. Plugged it back together and went again.

The angled wingtips wouldn’t stop the tip vortex as XFLR5 shows in the sim.s. would be better to round into them like Gemot. The difference they made to Gemot was nothing short of impressive. Holding Gemots wing in one hand whilst spinning around, with and without wingtips gives a tactile feeling of the drag differnce involved.

More to come soon.