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.

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.

Viscous effects

This video explains how XFLR5 approximates viscosity using the polar outputs from 2D analysis.

Techwinder says on the above video that it does not do the full complex analysis for viscosity. However at this point it looks like it does a pretty good job. I was satisfied yesterday with the outputs I made. Especially considering I’d not read the manual and was just fumbling around. It did a great job of confirming my approximate estimations for Sentach. Looking at the video manual and other text today, it looks like it could do more than accurate enough estimations for my current projects.

As Techwinder states in the forums, it’s not made to just bring in solid geometry from another package and do CFD on it. However it’s focus is foils and it seems to be very fast at assembling foils and doing to calcs. A massive step up from roughing the calcs out by hand. It should be far faster to design future RC wings like Gemot. Gemot was an estimation based on what I new from hands on experience windsurfing and surfing. I actually didn’t really expect it to fly as well as it did on that first proto which crashed into my van.

Although it took several CNC models before I hit Gemot V3. There was only 2D analysis of the 2 Gemot foils using the Dresler software, where I just looked for the best lift : drag ratio for a specific AOA. That became the tip twist for Gemot. It’s still not perfect, but with XFLR5 I may be able to do more accurate mental prototyping with the software.

Still, I wonder if the Autodesk CFD design handles importing the current .stl files for Gemot V3.

Testing the weight shifter.

Just tested the weight shifter at skenners. Flew perfectly … in a straight line. Flight weight 836g. Too much lift on these wings. Also the lift goes all the way to the tips rather than being laterally centralised. Thus the weight shift makes bugger all difference in this wing.Using 50mm thick foam sheets as wings is great as you don’t have to laminate them, but then they’re heavy, cause way more lift and require more power, torque, mass movement to drive rhem.

Mass shifter attempt 3

Attempt 2 was quickly cannobalised by attempt 3. Rather than trying to figure out a complete answrr to the universe by thinking about it, just start building.And by just building this the possibility of fore and aft mass shift becomea more apparent.This time the weight shift is only port and starboard. AOA set by a trailing wing.

Back to it.

It’s been a while without flying, but a recent revival of enthusiasm has put Gemot back in the sky. 30knots or so at Lennox about a week ago. Awesone flying. Then of course a throng of overconfidence about low passes caused a meeting with the ground cracking the top laminate on the starboard wing and a snapped servo horn on the flap.

Some repairs this morning and we’ll be back in the air in the coming days.

Gemot Yellow
Repairs for a snspped wing.

Nano Talon weight test

Have been testing the ZOHD Nano Talon slope soaring without the prop. We did a weight test yesterday. At a flight weight of 590 grams it flew just fine slope soaring in about 25knots of wind. This was 70 grams heavier than the flight weight with the 1500mAh 4S and the FPV gear. (Runcam eagle rpo 2, BEC, eachine ATX03) which clocked in at 520grams.

Wing, fin, sail – same basic concepts.

Whether it’s a wing, fin or sail, they all have the same basic features except they are just perpendicular to each other.  Actually, include hydrofoils into that. Yes there is a compression thing to think about in gasses, but we can half ignore compression until the basics are right.

Here’s a swept forward surfboard fin designed under similar concepts to the wings.