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21
Lost And Found / Lost...
« Last post by raven1978 on January 31, 2018, 08:33:36 PM »
Last seen around the first week of December sometime. Last time i saw it i was standing at pilot station 5 looking North. Description....around 1” in length, and green in color. Most of us would know it as grass, some call it “The Field”.

Really missing the warm flying weather right now.
22
This is a copy of the posting I made in another Forum, where the BGL-6G-AP GPS-capable stabilization system is discussed, Wilf and I have these units and have done a lot of experimentation with them.  Don't worry, there really is a video in here, at the end of the discussion.  :D

                                      -------------------------------------------------------------------------------------

This may be of interest to others:

I have had the unit on a flying wing for a couple of months, as a test bed. Yesterday, we were flying in extreme winds - significant wind gradient plus high level of turbulence. (Don't worry, there is a Video link at the end of this).

I set the plane out a somewhat downwind and the selected RTH. It immediately oriented itself and then flew upwind toward the Home point, as expected. I had, let's say, 1/3 throttle to maintain good progress.

Aside: the BGL's Return To Home control strategy is to self-level if necessary, head straight back to its Home coordinate, then circle or sometimes follow a figure-8 pattern centered on Home. It will attempt to maintain a constant altitude, provided it can maintain airspeed; if you chop the throttle, or are a pure sailplane, it will gradually lose altitude and may even stall or perhaps snag a nasty tree or such before you may regain control.

The plane arrived in the vicinity of Home and began its circle. Now, as one would expect, there will be some drifting and the resultant path over the ground would be somewhat elliptical. However, to the airborne pilot, maintaining a constant bank and airspeed will still result in a circle within the air mass. Now, one would expect the RTH function to be trying to maintain a circle with respect to the ground, as it is using the fixed Home coordinates and its GPS to set up a fixed radius circular or figure-8 pattern w.r.t. that ground Home point. Therefore, I expected to see it altering its bank angle accordingly, within limits, to try to retain its circular orbit. Not so much!

With this strong wind, the plane made its first turn and flew WAY downwind before beginning to turn back to Home. For awhile, I could observe it making some control corrections, probably experiencing some turbulence even at its "3 trees" altitude. I really began to wonder if something had gone wrong, but it eventually managed to turn back and beat its way toward Home. I had been just about ready to switch off RTH and take over with full throttle in order to get back. Well, she did make it back without my interference, but I had to use a high throttle and I watched as it sort of zig-zagged along its path back.

I repeated this test, with exactly the same results.

Now, this was a bit disturbing, but it was a good learning experience.

The BGL limits its bank angle to something that would be a shallow to medium turn while in RTH, regardless of its reference to the Home coordinate.

So, if I have this unit installed in, say, a sailplane that may not have terrific penetration and if I were to lose sight of it, I better crank up the motor and hope! As we know, you normally thermal in a circle within the rising air mass which, in turn, is being shifted downwind. Think of a funnel that is tilted and you are keeping inside of it. As you go higher, the migration downwind is likely to increase, as will be the effort to beat back home once you leave said thermal, especially when you encounter the surrounding sinking air.

In considering using the RTH feature under Failsafe, the question is, does one kill the power or set it to something like, say, 1/2 throttle? Not an easy answer, as circumstances vary. Besides, you may have no choice anyway! Not all receivers handle a loss of signal the same way. and ESC's tend to shut off the throttle if no signal is seen for a very few seconds. So, all you can do is hope for the best! Also, you may want to bump up the throttle immediately upon activating RTH, if you cannot see the aircraft or if you suspect that it may have failed safe into that mode. If you in no-power soaring mode and go into RTH, the aircraft may not make it back, especially if it has to do much banking to achieve a straight line flight path and/or if it does a lot of the weaving back and forth that I observed. Of course, you want to know that your airframe, especially a large foam sailplane, can stand high airspeed and gust loading combined, or it may relocate itself in pieces!

I think about this stuff. It's all part of this weird hobby. We have so much terrific technology available, it is fun to learn what it can, and can't, do.


https://youtu.be/NW2R5hyj3nA

Thoughts?
23
General Discussion / Re: RIP Gord
« Last post by General Malarky on January 25, 2018, 10:53:21 AM »
Gord was one of the best and will be missed.


I don't know if it would be in bad taste, but would epoxying some of his ashes in to the little Snoopy Pilot on his Fokker be a nice way to commemorate him? Keep him flying, and such?
24
General Discussion / Re: Puddle Flying
« Last post by Deerslayer on January 24, 2018, 03:24:39 PM »
Glad you enjoyed it! These are fun little machines. I flew mine today out at the field, sunny -8C, light breeze, warm stove in the club house. Perfect! Too bad no oneelse took advantage of it. Tomorrow looks good, too!
25
General Discussion / Re: Puddle Flying
« Last post by Swigert on January 24, 2018, 01:55:01 PM »
That's so awesome. That little plane has personality. Thanks for sharing.
26
General Discussion / Vortex Generators
« Last post by Deerslayer on January 08, 2018, 10:56:41 AM »
Vortex Generators (VGs) have been around for many decades. I first noticed them on airliners I flew on back around 1970. You may notice them on smaller airplanes, especially of the STOL variety such as some bush planes.

About four years ago, my son started flying a Cessna 206 floatplane for his client. He installed a VG kit on it. The kit was a properly engineered and certified modification, cost $2500, which he installed over the course of a day or so. There was some huge number of these things, epoxied onto the top of the wings and onto the underside of the horizontal stabilizer. Their effect was to improve airflow separation over these surfaces. This resulted in approximately 5 knots lower stall speed or could allow a higher payload capacity. Floatplanes often have to squeak into, or hop out of, very confined areas with nasty trees, etc., in close proximity. The VGs were the one thing that could be done to improve things.

At that time, I became interested in finding out the science of VGs and how their effects are investigated and quantified. The information is out there, and there is fluid dynamics math, but some of it left me a bit bewildered.  I like pictures and videos! (Be patient, there is one coming up shortly...)

More recently, VGs started showing up on RC models. The Visionaire, Carbon Z Cub, Scimitar, all of which I have owned, are just a few that come to mind. Do they work at this small scale and low Reynolds Numbers? Hard to quantify, but experienced pilots report that they do make a difference, at least on some airfoil and airframe configurations.

I found this video to be enlightening. The fellow is admittedly not an aeronautical engineer or fluid dynamicist but he has done a terrific job of explaining things and documenting his experiments. The RC plane test near the end is a particularly compelling argument to accept the value of VGs and not just grab the Exacto knife and slice them off (as some amongst us may have done in the past!).

So, please sit back and check out this:

https://www.youtube.com/watch?v=eP-YUDe9HF0&feature=youtu.be
27
Buy, Sell, Trade or Give Away / F-16 Ducted Fan Kits for Sale
« Last post by Deerslayer on January 07, 2018, 07:35:53 AM »
I have two of these for sale. Dan and I had one a few years ago and can vouch for what a great plane these are. Hand-launched, easy to fly, they are a perfect way to try out electric ducted fan aircraft at a rock bottom cost. To my knowledge, these are no longer available, much to the dismay of the very large group of enthusiasts for the product.

Here is the primary RCGROUPS forum:


https://www.rcgroups.com/forums/showthread.php?725426-Hobby-People-Phase-3-EF-16-EDF-Review

Many owners customize their F-16's in appearance and also with other than the original EDF gear - a lot has changed over the past decade. Some of these planes have been built with truly wicked performance packages!  The fan is readily available form Hobby King or elsewhere.

I am asking $45 each, and I would consider something slightly less if sold as a pair.
28
General Discussion / JR files bankruptcy
« Last post by Dwayne on January 01, 2018, 09:17:29 AM »
JR has filed for bankruptcy and will close it's Japan factory, another one bites the dust?  :'(
29
Plans, Projects, Building and Flying Tips / Re: Fokker DVIII Build (update)
« Last post by Dwayne on December 31, 2017, 04:13:01 PM »
Taking advantage of the cold weather to do some work on the DVIII, Tail coming along nicely  8) ;D
30
Plans, Projects, Building and Flying Tips / Re: Balancing Stuff
« Last post by Deerslayer on December 26, 2017, 06:22:35 AM »
 Speaking of balancing stuff:

 As with a number of other aircraft I have designed and/or built, I often think up some different situations w.r.t. C of G concerns - before carving out material. For my new Penguin FPV plane, I decided to move the Elevator servo way back to the tail, rather than keeping it up front and having the long control rod. This is a common mod for the plane.

 Prior to the Penguin, I created a spreadsheet (available to anyone who asks) to investigate many configurations for a flying wing of my own design. I had flown it with a stabilizer for protection and determined where the C of G had to be in order for it to fly nicely, non-stabliized. In that case, I was about to add some FPV stuff onto the wing and needed to shift the LiPo sideways and rearward a bit to accomodate the camera, thus moving the C of G rearward unless I either added some nose weight (detestable!) or using, say, dual 1000 or 1300 mah batteries, or one 1800 mah battery rather than the single 2200 mah battery. There were a number of other possibilities.

 I ran the spreadsheet against about a dozen options and chose one of the best results. The plane flew as well as before the changes, with no parasitic weight addition. I have done this kind of paper work on balsa planes, where I wanted to achieve certain performance improvements (usually snappier!) without cutting into wood or stooping to adding weights somewhere.

 I may remove those atrocious nose weights from my Optera and compensate with larger or more LiPo, applying the same approach - measure twice, calculate, then cut once.


Now, for the Penguin example:

Given:
Required C of G location is the datum (everything measured from there)
Servo Weight = 20 grams
Standard Location = 10 cm aft of C of G, approximately (distance from datum to middle of servo)

Scenario:
Rear Servo Location = 65 cm aft of C of G (conservative estimate, could be slightly less)

Required Counterweight Location = 35 cm forward (conservative estimate, could be slightly more, your choice)

a) Initial Servo Moment Arm = 20*10 = 200 g-cm

b) Rear Servo Moment arm = 20*65 = 1300 g-cm

Moving of Servo from Standard to Rear Location: 200 - 1300 ~ -1100 g-cm required to compensate
Therefore, required Counterweight at 35 cm forward: 1100/35 ~ 32 grams

For the Penguin, this much compensation is not a big deal, probably well within what I will instead do by battery selection and location. I have a large number of 2200 mah batteries, this being my personal upper limit for my electrikery inventory. I plan to parallel a couple - or possibly even 3 - of these for this plane. To fit the servo in its standard location, I would have to hog out the lasered hole a bit anyway. I hot glue servos into foam aircraft, so rear mounting is simple and I can still install a couple of CF strips if I am really concerned about strength. Of course, my landings are always as soft as settling onto a pillow anyway
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