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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.

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EAP’s – Electro Active Polymers

An EAP is a manufactured muscle fibre. If anyone knows where to buy, or how to make them., please contact me.

Preferably with contraction times measured in milliseconds.

I found some info here:

https://ndeaa.jpl.nasa.gov/nasa-nde/lommas/eap/EAP-material-n-products.htm

parker.com

https://ndeaa.jpl.nasa.gov/nasa-nde/lommas/eap/EAP-web.htm

http://www.hizook.com/blog/2009/12/28/electroactive-polymers-eap-artificial-muscles-epam-robot-applications

www.ct-systems.ch

Making EAP’s

https://ndeaa.jpl.nasa.gov/nasa-nde/lommas/eap/IPMC_PrepProcedure.htm

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The current tip foil for Sentach

Being a bit too fried to do a proper stability analysis for Sentach, but having enough mind to sketch out the dimensions for the tip twist foil, the above shape emerged.

Designed to fit into the 50mm thick EPS sheet at 7degrees. It should kill the lift and thus tip vortex nicely. Same as Gemot, however Gemot is 7degrees and a far slower and more tolerant foil.

After watching all of the tutorial videos on XFLR5 yesterday I might do a stabilty analysis first…. Hmm maybe…. I also just want to test the head tracker and Sentach is a rough wing, not a refined design.

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Where are the EAPs?

Electro Active Polymers. Where are they?

I seem to continuously be looking for linear actuator which are small, light, fast and not a bastardisation of a rotational or solenoid device. The synthetic muscle so to speak. I saw one on the television show ‘Beyond 2000’ about 20 years ago and remember thinking “right, a revoltion of mechanics is here”.

Obviously not.

I found a thesis of something at Woolongong Uni a couple of years ago and have not followed it up yet.

Either way, if someone knows where I can get EAPS which I can chain in series or parallel with the reaction time of a standard RC servo, please contact me (Dion) via SMS on +61 419 486 672.