Jack Erbes is one of the modern day geniuses of foamy construction. Here's his RCG build log of a KFM3 wing for the Blu Baby. My BB32 wings broke in half, so I'm especially interested in this. I'll lightly edit, but the first person voice is Jack's. I'll try this later and do my own writeup if I think it might be useful. Jack writes:
I recently made a KFm2 wing with polyhedral tips for use on my KFoenix Stick and flew it in RET configuration (Rubber, Elevator, & Throttle, no ailerons) and was really impressed with it. It had excellent tracking and control and good rudder authority, which had been a problem with the stock Slow Stick wings. The wing seem to "lean into" the turns nicely as speed increased and as turns were made more aggressively. It was almost as if I were flying a wing with ailerons.
Decalage refers to the angle between a plane's main wings and the elevator, or the two pairs of wings on a biplane. There's a great discussion in the RCG UMX Radian thread. I'm capturing it here coz... well you know how searching on RCG is. Post numbers are 3431, 3434, 3435, and 3442. Big Thanks to Phil Alvarez and turboparker for sleuthing these out of the thread.
My Summary:
Porpoising is caused by bad decalage.
Don't try to solve by changing CG.
Small foamies can incur twists due to their light construction.
Standard decalage test:
Perform a power-off vertical dive from high altitude (neutralize elevator).
A. Model continues straight down: No change needed.
B. Model pulls to canopy: Increase stab incidence with respect to the wing.
C. Model pulls to belly: Reduce stab incidence with respect to the wing.
Here's the Concord Model Engineers Logo! 61 years continuously meeting, and we still have a couple of charter members that show up every month.
The logo had gone missing for a while, so it was decided to send a copy of the logo to every member in the hopes that somebody would have a copy the next time it was needed. DVCS at its finest!
We got to the end of the ArrBot class, and 6 ArrBots showed up for the rally! Sadly, a seventh ArrBot was stuck in a meeting with its driver.
I'm really pleased with how everybody did. We started off with a soldering class, raw plastic for the 3D printer, the literally cheapest parts we could find on the internet, and a partially finished prototype.
We printed the bodies, modified cheap 9 gram servos into continuous rotation units for power, and worked through some pretty tricky electrical problems. Everybody make prints and modified the servos. Most were able to run the tread test program. There's a few that just need some radio work (much easier now that we've had a couple of successful units under our belt!), and that should be ready in the next week or two.
From the class comment forms the students seemed to like everything as well. The hardest parts were the servo modification (honestly, a pretty challenging task with that size of servo) and the radio setup. There was a bit of a time crunch as well. In future classes we may schedule a class alternating with a lab so that there's no expectation of anybody having to work at home. We'll also be better on differentiating between 3.3V and 5V requirements. We needlessly burned some time having to work around that.
We'll continue to work on the ArrBot software. I think it will be a useful contribution to various two-wheel and two-tread robots. Some upcoming features:
gyro stabilized calibration
battle lights
onboard sound
Bluetooth control
ArrLang, the ArrBot robot control language
We'll also continue to study the radio hardware. There's some interference problems with the Bluetooth, and we had to add a capacitor to the nRF units.
But the end resulting units worked well and were a lot of fun to drive around. I definitely think that adding RC capabilities to educational robots is the way to go.
Notes to self for next session:
get all 3.3V pro mini's.
get switchable 3.3V/5V FTDI units instead of the FTDI cables, which were more expensive and not of particularly good quality.
get two FTDI units per student for ease of debugging radio communications. This can be done with the cost savings of eliminating the FTDI cable.
get 20mm header pins, as they held into the breadboards much more tightly.
have students provide two USB "B" cables for the FTDI connector.
get a stock of male and female crimps and covers.
have students provide their own wii nunchucks.
investigate SMD resistors for servo modification use.
Here's some video of the rally: The first item is trailer-style, the rest are are more traditional EastBay RC style videos. If anybody's an expert at embedding playlists on blogspot please give me a call!
Here's a quick overview of both the ArrBot and ArrMote.
Sigh, Youtube can be annoyingly dumb in its automated content matching. The KBS video has been disputed twice, so I'm putting the permissions here for easy reference by the Youtube staff.
BTW the KBS people were excellent to work with, this is no complaint against them. It's actually no complaint against Youtube, they're just having a problem with reflagging items they have already cleared.
Date: Wed, 15 May 2013 15:25:44 -0500
Message-id:
Subject: Electronic Copy of World Today from KBS of South Korea - UAV
From: Shin Sul
Hello, this is Kevin Shin Sul, one of US coordinators working with KBS of South Korea.
The program "World Today" with the portion on drones aired on May 11th, in South Korea.
Here
is the link to download the electronic copy of the aired program. You
are free to use your portion only in non-commercial purposes only.
Please confirm with me if you are not sure if it would be.
The portion regarding UAV will start at 33 minute mark and go on till the end.
Please click "PC" next to the link provided below:
Here's the Phase 1 ArrBot and ArrMote, completed and running.
I put the ArrMote electronics in a box to keep everything tidy. A plastic box There's a small hole for the Nunchuck wire, providing strain relief for the unit. The Nunchuck adapter is likewise twist-tied to the Nunchuck Connector. I think I'll put a switch on the outside... right now you have to open the box and attach the battery to the Pro Mini. The battery could be smaller, as low as 3.3V.
I did some fiddling with getting the nRF chip a bit tidier. I ended up using some short servo wires which were just long enough to raise the radio above the other wires. The 1000uF capacitor is way overkill but I had a bunch sitting around.
Here's the nRF24L01+. It is really neat and provides some pretty amazing capabilities considering its $1 price tag!
I think the Pro Mini 3.3V running at 8MHz is officially my favorite Arduino chip these days. Be sure and get a 3.3V FTDI cable!
The bracelet treads seem to be holding up pretty well. If you have a dud bracelet it will separate almost as soon as you start using it. If that doesn't happen it seems it will keep going for quite a while.
I recently made a KFm2 wing with polyhedral tips for use on my KFoenix Stick and flew it in RET configuration (Rubber, Elevator, & Throttle, no ailerons) and was really impressed with it. It had excellent tracking and control and good rudder authority, which had been a problem with the stock Slow Stick wings. The wing seem to "lean into" the turns nicely as speed increased and as turns were made more aggressively. It was almost as if I were flying a wing with ailerons.
