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Posted by corsair2014 | Sep 01, 2019 @ 10:42 PM | 878 Views
So yeah... I'm a bit late to the mini-quad game. Last time I was really building multirotors, the standard size was a 450mm quad...

Anyways, I snagged this little guy to get in some practice before I attempt to destroy my Gopro Hero 7 on a quad that I can't really handle And man, this thing is FUN! People told me these micro 'CineWhoops' were underpowered, so I can't imagine what a proper 3" freestyle setup is going to be like because this thing blew me away! Plenty of power for me right now and my twitchy thumbs. Only problem I have noticed thus far is in dives I do regularly get washout, causing the quad to suddenly yaw-spin when I pull out of the dive. I suppose that is just a limitation of these little beasts, so I will learn to fly around it.

Here is a (mostly) raw clip at the end of my first day flying an FPV quad. I am hooked



End of the Beginning // Beta85x HD CineWhoop (3 min 36 sec)




P.S. Follow me on Instagram to see edited clips and more info on my adventures
www.instagram.com/highlydistracted/

Posted by corsair2014 | Aug 31, 2019 @ 11:12 AM | 858 Views
Disappointed that some hyperstall/microstall tendencies persisted in the B-Wing mk.2, I was about ready to hack off the leading edge of the wing to give it a sharper profile. In fact, I even ran some quick CFD tests of different leading edge designs to see if my extra-round leading edge was causing premature flow separation or other problems.

Quick KFm2 Leading Edge CFD test (0 min 50 sec)


While those simulations were running I decided to go out to my secret test location and run a few other scenarios with the Mk.2 to see if I could reduce the microstalling further.

First Flight: removed the AA battery that was taped on for nose weight (24 grams). Hyperstalling immediately exaggerated and a new 'diving' or 'tucking' tendency arose making it impossible to fly straight and level

Second Flight: added back the AA battery and added a second battery (total 48 grams) for nose weight. Microstalling 99% eliminated! No more tucking and no more bobbing in regular turns (only in very hard, high-g loaded maneuvers which is somewhat expected)


---------Flight Video---------
https://www.instagram.com/p/B1pv_1Ln..._web_copy_link


So for now, I suppose that ends the B-Wing microstalling/hyperstalling mystery... sort of. By changing from a KFm-2 Airfoil to a KFm-4 I saw a large improvement in flight performance. And then by dialing in the CG I was able to eliminate 99% of the remaining issues. The aircraft still doesn't fly perfectly, but that is something that can be tuned in over time (I can live with this considering it has been over 3 years since I built a plane!).

Next Step: Get my FPV pod v2 finished up and go for an FPV maiden
Posted by corsair2014 | Aug 26, 2019 @ 10:51 AM | 597 Views
So yesterday I took the B-Wing mk.2 out for her maiden voyage, and the initial flights went well. Fairly well balanced, and CG seemed to be close. However, the 'hyperstalling' issues seen on the mk.1 continued to plague the mk.2

If you haven't ready the mk.1 blog posts, here is a summary: under high-loading maneuvers, the aircraft will bob its nose in a 'hyperstall' like attitude in which the plane stalls and recovers quickly in somewhat rapid succession. This makes the plane difficult to fly and, ultimately, a very poor low and tight FPV platform like it is supposed to be

The mk.2 doesn't exhibit hyperstall to the extent the mk.1 did (where it was basically unflyable) although it is still present and annoying. Overall however, the mk.2 with the KFm-4 wing flies much better than the KFm-2 on the mk.1. As usual, for more build details check out my 'Stories Collections' on Instagram where I log the builds and such: https://www.instagram.com/highlydistracted/




Quick maiden flight video (courtesy of my lovely wife):https://www.instagram.com/p/B1od11AnTmd/




After some quick research, it seems that hyperstalling is largely caused by a nose-heavy plane, especially on low sweep angle wings (http://www.slopesoarer.com/Plank_Set-Up.html). Before I hack up the leading edge on the B-Wing mk.2, I will do some more flight testing with the battery moved further aft and see how that effects the flight performance. According to the standard wing CG calculator (see attached image)...Continue Reading
Posted by corsair2014 | Aug 23, 2019 @ 09:49 AM | 989 Views
Quick clip showing bobbing:


Quick clip showing bobbing (0 min 55 sec)



Okay, here are some things I tried to remove that bobbing:


1) Change CG. Moved it way forward, way back, not much difference in the 'bobbing' behavior

2) Extend elevons. I thought perhaps the elevons were being blanked out at higher angles of attack as the flow separates/KF airfoil vortex sheds from behind the step. However, this seemed to make the behavior WORSE

3) Stiffen control linkages. This involved moving control horns to top, increasing torque and resolution of servo by adjusting linkage position, firming up the elevon hinge, etc. Didn't make much difference

4) Fly upsdide down.

And #4 is what made the difference. The wing flew a bit better upside down! For some reason, my KFm-2 wing wants to become a KFm-1 wing... and under loading (hard turns etc) this tendency flairs up and causes the bobbing behavior seen in the video.

Why does this happen??

Honestly I'm not sure, and being an aerospace engineer, it is killing me not being able to figure it out Sometimes when I am flying straight and level a gust of wind will come and make the plane take a hard nose dive... which means that in 'level' flight the wing is on the verge of creating 'negative lift', or swapping the high and low pressure regions of the wing... very odd, haven't seen that before.


All in all, it was a great learning experience (although frustrating) and revealed some good and bad points of...Continue Reading
Posted by corsair2014 | Aug 20, 2019 @ 02:25 PM | 672 Views
I present to you, the B-Wing...

This is my 1st design in my "get back into FPV" project series. It's called the "B-Wing" because it's designed to be a [B]asher wing, meaning it is cheap and fast to build so I can focus on hitting various tree gaps and improving my FPV skills. Also, because it's not designed to have the highest performance but rather be quick and cheap to build with adequate performance for it's intended use (i.e. it isn't an "A" level perform but a "B" level). This wing will utilize my 3d printed Caddx Turtle v2 swappable FPV pod so I can move it between various planes as I test different designs. This wing has a KFm-4 airfoil, and I plan to make a version 2 with a KFm-2 airfoil for comparison.

So, turns out I am really distracted and accidentally glued the two wing steps together, making a KFm-2 instead of a KFm-4

Anyways, with the plane built up it was time to go test! To keep this post short and sweet, I will summarize the maiden results

1) It flies... technically. But it doesn't fly well
2) Alot of 'bobbing' and flutter in the wing under loading (i.e. pull-up, turns, etc)
3) Tested various CG positions, found that the plane was close to spot-on or maybe a bit nose heavy for this airfoil

So feeling a bit disappointed but curious as to what was causing this 'bobbing' action, I went home to do some research and change a few things.


Recap video: https://www.instagram.com/p/B1ZgTM_n9iL/

Side note: you can follow my Instagram to see my flight log videos (in my stories collections) for all my designs: https://www.instagram.com/highlydistracted/
Posted by corsair2014 | Nov 01, 2018 @ 09:19 AM | 14,646 Views