2019 Aero Design

[Beavertail]

Here is the link again! Flight Videos are attached!
https://photos.app.goo.gl/kWMVuiXtArLUvYh68

[JohnOSullivan]

Congratulations Gary.
I meant to comment earlier but was having problems putting things into words.

This years model is streets ahead of your previous models.
Proportionally the model was quite good and your wing section was more conservative than before.
I notice that you did not use Flaps. It did not need them and that simplified things a fair bit.
Glad to see that you incorporated polyhedral This can contribute greatly to stability.

The wing spar was a very heavy component and looked well suited to the central part of the wing. However stresses are much reduced spanwise and quite a bit of weight could have been saved by tapering the spars towards the tip as well as reducing the carbon wrapping on the front and back of the spar.

The choice of twin motors was excellent. However 750 Watts maximum for a model of this weight is marginal as with an input of 750 watts running at 75-80% efficiency it is only putting out about 600watts. On your first Video the model looked as if it was struggling badly in the first portion of the climb, but settled down on subsequent flights.

It would help greatly if the model could have been built and flown long before the contest.

Overall a great effort and with a little refining of this design, you should take top honours next year.

[retiredVTT]

Thanks again Gary, for keeping us up to date on this years contest. It's really exciting to follow along when you know one of the competitors..!
Your team has got to be deservingly proud of what was achieved from all those late nights.

cheers..!

[Beavertail]

Congratulations Gary.
I meant to comment earlier but was having problems putting things into words.

This years model is streets ahead of your previous models.
Proportionally the model was quite good and your wing section was more conservative than before.
I notice that you did not use Flaps. It did not need them and that simplified things a fair bit.
Glad to see that you incorporated polyhedral This can contribute greatly to stability.

The wing spar was a very heavy component and looked well suited to the central part of the wing. However stresses are much reduced spanwise and quite a bit of weight could have been saved by tapering the spars towards the tip as well as reducing the carbon wrapping on the front and back of the spar.

The choice of twin motors was excellent. However 750 Watts maximum for a model of this weight is marginal as with an input of 750 watts running at 75-80% efficiency it is only putting out about 600watts. On your first Video the model looked as if it was struggling badly in the first portion of the climb, but settled down on subsequent flights.

It would help greatly if the model could have been built and flown long before the contest.

Overall a great effort and with a little refining of this design, you should take top honours next year.

Thanks so much for the response John! Great hearing from you!

The idea was to have the root chord large enough which basically incorporated the flaps into the airfoil since we will be needing them throughout the entire flight anyways! saving weight and complications like you said and for sure the polyhedral was huge help this year making the plane super stable in the wind! The only issue from that this year was the 20knot crosswind takeoff and landings which consistently rolled the plane over due to the polyhedral and ground effect. This was no issue with a head on takeoffs from the second day however. Since the plane was so stable after takeoff, I believe we can reduce the poly by about 5 degrees from 15 to 10 to help with that? Please let me know if you would have insight on that! Thanks

One of the main goals for next year is indeed to lighten the main wing. I really liked the design they went for this year and would like to keep it. We do plan on lessening the rib numbers and creating lightening holes throughout. I never considered the taper in the spar though which is something i will look into. The initial plan was to have a foam core and three layer of unidirectional on top and bottom, however, due to unaccounted torsional loads, three layers of 45 degree weave was wrapped around the spar which took the weight from 1 to 3lbs. Tapering is something i will for sure try next year for lightening!

We actually recalculated the prop sizing and ended up running an even bigger prop at 16x10. This allowed us to be at 750watts at all times as the battery depletes. But you are correct at the efficiency, we got about 9lbs of thrust which is less than 5-8% than theoretical calculation i believe! amazing how efficient electric motors have become! The first portion of the flight was struggling due to the howling 20 knot winds aha but yes it was terrifying!

Refinement will be key to next year's design i believe! lot of great things to build upon for next year!

[Beavertail]

Thanks again Gary, for keeping us up to date on this years contest. It's really exciting to follow along when you know one of the competitors..!
Your team has got to be deservingly proud of what was achieved from all those late nights.

cheers..!

Thanks Bill! I agree, they did a fantastic job on the design of the plane this year! we really plan on refining the design and hopefully an even better flying aircraft for next year!

[RocketManRC]

That's awesome Gary, great to see it in the air!

[Beavertail]

For anyone who is looking for a nice afternoon read I found the Final Design Report which outlines the entire design and engineering notes of the aircraft!
https://drive.google.com/open?id=19WGRR ... XfVz4ZIMSx

[JohnOSullivan]

Great stuff Gary. I just arrived back from Ireland and had a chance to go through the whole thing on the plane. A very thorough venture and it looks like you have some good ideas for the way forward. I have some suggestions and a bunch of very significant practical links, mostly from Mark Drela which you could use to effectively lighten the structure. Keep up the good work.