Crash's Guide to FPV Radians

[Crash]

Stock Radian

There are two ways to build up the stock Radian, light for casual/short range flying, and heavy for distance/speed.


Lightweight Build

This is the easiest and fastest way to get your Radian FPV ready.

Pan and Tilt

The Radian is THE perfect candidate for a P&T setup. Its such a slow and stable platform that you can look around without fighting to keep the plane on course. For pan and tilt, it's best to mount the P&T straight to the canopy. Because on this build, we won't be doing any structural mods to the wing saddle joint, its best to not try to mount the P&T onto the fuselage above the canopy. In this photo, I'm using the P&T mount from Low Price RC



ESC, RC Rx, and servo placement

If you purchased the ARF or RTF Radian, then the stock Eflite 30A ESC is plenty adequate for this setup. Use it and you can mount the ESC in its stock location. Same with the servos and RC Rx, continue to mount them in their stock locations. If you purchased the foam only and are building it from "scratch", then any Turnigy 25-40A ESC will be adequate and should fit nicely in the stock location. HXT900s or any other mini servo is plenty for this build and should be mounted in their stock locations.

Battery

For this lightweight build, I recommend using the Zippy Flightmax 2200mah 20C batteries. They're cheap and small! Without any modification, they should slide nicely into the stock battery cutout but will require some tail weight to balance (more on that in a min). If you use any other battery and it doesn't fit, spend a few minutes with a breakway utility knife and carve out the foam needed to keep your battery snug. Also, remove the plastic mount and velcro strap for the battery that's glued inside the fuselage. You won't be needing that.

Motor and Prop

The stock motor is THE most efficient motor I have found so far for the Radian. Believe it or not, Eflite actually got something right. On this build, use the stock prop and the stock prop only. For a lightweight build its super efficient and can cruise at 18mph pulling 3-4A. This plane really needs some down thrust built in, FPV or not, its very pitchy on the throttle. Just toss a washer or two to get some down thrust in and it will fly so much better.

If you haven't read it before, avoid APC folding props (although on this setup its such a low wattage that you would probably be ok) they have been know to break. Also, don't get silly an experiment with other random props at the hobby shop because they were out of stock of a carbon prop in a larger diameter, or this will happen




That's an Eflite 11x7 folding prop I found at the hobby shop and during a full throttle motor run in the house, blade broke at the hub and slung it through the ceiling. Before I could get the throttle closed, the now unbalanced motor did this to the nose




You have been warned...

OSD, wiring, etc

With this lightweight build, the plane isn't heavy enough to punch through winds over 10 mph very efficiently. Accounting for wind and battery capacity, its safe to say this is probably a 2 mile out and back setup MAX. On a calm day or with a tail wind, you can easily go further, *BUT* you don't have the weight to punch through any kind of headwind. The plane will slow down to 5mph and gently fall straight down. *IF* you were lucky enough to get back it would have taken you 20 min to get back from 2 miles in a 10mph headwind if you were just attempting to glide back, assuming you had the altitude to pull it off. All of that brings us to this point, a "full house" OSD is useless on this build and only increases the cost of replacement if something was to go wrong. The HK Simple OSD is all you need.

If you are using a 12V camera and VTx, just run everything straight off the balance plug. The motor/ESC combo does not produce any noise in my video at any throttle setting. At the time that the following picture was taken, I was using the "buck inverter" to keep a constant 12V to the camera and VTx regardless of how low the flight pack got. This really isn't necessary because *most* 12V gear will operate much lower than your flight pack EVER needs to go and much lower than ESC low voltage cutoff will allow.

If you have 5V equipment, use this step down regulator

http://dimensionengineering.com/DE-SWADJ3.htm


I would pretty much say the HK Simple OSD is a must for this airplane. Due to the insane flight times you can get, and due to how easily you will be distracted looking around with P&T, you don't want to find yourself 1 mile out and at low voltage cutoff.

So just run all your wiring to the canopy and tape/velcro it in place




VTx and VTx antenna Placement

Because of the extra weight we added in the nose with the P&T, OSD, and battery, we need some weight in the tail to balance. So, once you have everything in the nose built and assembled, move you VTx around on the back of the fuselage until you get the plane to balance. And while we're on the topic of CG, I think the Radian flys the best and has the flatest glide with the CG about 1/4-1/2" behind the CG finger holes on the wings.

For the lightweight build, glue a piece of velcro to the back of the fuselage and just velcro the VTx in place. Don't go removing foam and trying to mount the VTx "clean" into the fuselage to keep it more streamlined. Remember, not only are we trying to make this a fast build, the speeds this lightweight version will see, having the VTx hanging out in the wind wont affect a thing and all you would be doing is weakening the tail. Disregard the VTx antenna placement in the following picture. You want to mount the VTx antenna as far away from the RC Rx antenna. The only downside to mounting the VTx on the back of the fuselage is when you turn back home and fly straight at yourself, the video would drop out occasionaly. I never noticed it when I was flying this specific build, but on the heavier builds, the big battery and everything in the nose was blocking the video signal from getting out clean. I noticed it more of a problem on 2.4 than when I was on 910. So, just for good practice, get your Vtx antenna mounted high in the air, because I would notice whenever I turned home and lost video, if I pointed the nose down the video would come back. So would flying at an angle back home, but we can eliminate that problem or make it easier to deal with by getting the antenna 4-5 inches up.

EDIT: I can confirm after a couple test flights, the antenna 4" higher fixes my problems with video drop when turning home and flying directly back at me. Will do some distance flights this week and see if it still works at range.




Linear Polarization

Since using the stock whip antenna, regardless of your video frequency, doesn't get it high enough up. Not to mention, they usually aren't tuned well to your exact frequency. Build yourself an IBCrazy Inverted-Vee antenna. SUPER SUPER SUPER easy to build and will kick your stock antenna's butt.

If on 910mhz, you would need to make a support frame for the antenna because of the long 1/4 wavelength wire lengths. Popsicle sticks, balsa sticks, etc, it all works. Use the vertical stablizer as you mount and use the balsa sticks, etc, as needed to support the wire that will hang off thefront of the vertical stab.

All ofther frequencies, the vertical stabilizer should have enough surface area to tape the Vee antenna to without neededing any suport structure to keep the wire lengths straight. Again, mount it as high up on the vertical stab as possible

Circular Polarization

Build/Buy you an IBCrazy cloverleaf and build/buy it with a 4-5" coax extension from the antenna to the SMA connector. This should get it high enough to elimitate that problem or at least make it better. You will need something to keep the antenna to stick straight up. If you build it yourself, before you solder up the SMA connector, slide on a 4-5" piece of heatshrink over the coax. Once you solder up the SMA connector, put a 1/8" diameter wooden dowel, pushrod tube, anything thats somewhat rigid and shrink the heatshrink. Now you have a rigid coax length to keep the antenna straight. If you buy one and don't have this option, glue a wooden dowel, or fiberglass rod in the back of the fuselage to run the VTx antenna coax up and use tape or something to attach it to the rod.

Again, like I said, I never really experienced this problem on my simple/lightweight build, but just preparing you for what is a possibility. The best thing to do is go fly with what you got and if you experience this problem, go back and try to get the antenna higher.

[Crash]

Speed/Distance stock Radian build

Note: I'm only going to address changes in the following builds that differ from the build above
I've not seen many people use the Radian to its full potential. It's probably hands down one the the most versatile airframes for FPV. So, I set out determined to change the way people built and viewed the Radian. As demonstrated above, it can be built up simple, lightweight, and all in just a few hours to have a plane thats just down right fun to fly that can stay airborne for 25-30min on a 2200mah pack. Now, we're going to double that capacity and show you how to take it 8 miles

Battery

The first step to going distance is a bigger battery. I didn't think it could work, but Sentry kept pushing me to shove a bigger battery in the plane and its the best decision I made in the Radian builds.

The best ratio for weight vs capacity is a Zippy Flightmax 3S 5000mah 15C (or the 20C if the 15s aren't in stock). The 5000 is about 20 grams lighter than 2x 2200s (not factoring in the weight of the parallel plug, etc) and 800 more mah.

Time to get out the breakway utility knife and get to carving to make room for this monster.








Notice the foam the width of the battery cut out from in front of the battery. You need this cutout to insert the battery as well as moving it around to get final CG placement.

Motor/Prop/ESC

I still stand by the fact that the stock motor is the best/most efficient motor I have found for the Radian. As long as you don't over prop it or run at WOT for the entire flight, the motor should survive just fine.

Now its time to step up our game on the prop choice. With the extra weight on this build, the stock prop is not enough. At full throttle, you're always flying on the edge of a stall with the stock prop. I'm currently using the Aeronaut 11x8 Cam carbon folding prop. This prop works and has lots of power, but is a little much. The 11x6 works best, but the 11x8 was all the hobby shop had after I destroyed my 11x6 (more on that later lol). With the stock motor, the 11x6 pulls 21-22A at WOT on a fresh charge. The 11x8 pulls closer to 26-27A at WOT on a fresh charge. Going to a nice carbon prop, totally wakes this plane up. It goes from a gentle little glider, to a rocket with its course set on the moon! It climbs at 750 ft/min at 35+ MPH, full throttle level flight with no wind is 50+ MPH. Had I not throttled back, I would have done 1.5 miles in 2 minutes flat

Here's proof:


View this video on Vimeo


Now that we are pulling more constant amps we need a bigger ESC. Another thing to factor in is now that we are going distance we need to think about the quality of gear we use. I just like to be on the safe side, so I'm using a Castle Thunderbird 54A ESC. Whatever you use, give yourself plenty of amp overhead. With the bigger battery in the nose and due to more heat being generated by the motor and ESC, its time to find a new place for the ESC. I decided to move it outside the fuselage.

ESC Placement

Put some heatshrink around the motor wires and run the wires out one of the cowl holes. The heatshrink is to protect the wires from the sharp edges of the cowl. Plug in your esc to the motor and lay it on the side of your fuselage and trace the outline. Use a heat gun to heat up the tip of a flat head screwdriver and start carving. I'm not a big fan of using a soldering iron to melt foam because its too easy to melt too much, not to mention all the heat coming off the rest of the iron (not just the tip) and if you're not paying attention, its easy to melt more than you wanted to.

Behind the ESC, punch a hole through the fuse for the ESC battery and rx leads to go through. I hot glued some velcro straps to the outside of the fuselage to secure the ESC and motor wires. You don't have to worry about the prop hitting the wires. I know if you fold the blades back and spin it around, the prop blades will make contact with the motor wires, but the MOMENT that motor spins and the blades are folded, the flip open. Spin it by hand and try it if you don't believe me. Several flights later I don't have any cuts on my wires.



Servo Placement

Due to the additional weight from the 5000 pack, we need more weight in the tail than just the VTx, so I decided to move the servos back to the tail. Their specific placement depends on the weight of your gear in the nose and how far back they need to go to balance. Its best to tape everything in place where you want it and move the servos and VTx accordingly to balance. Just keep in mind, there is a fiberglass strip that runs the length of the fuselage to the tail and extends vertically into the fuselage about 1/2" or so. And of course you will need to extend the servo wires. I soldered on longer wire to minimize the number of plug connections, one less failure point.



RC Rx Placement

Because the 5000mah battery occupies the place that the Rx was intended for, it needs a new home. Since the servos are no longer in the foward fuselage, we can place the Rx there.

[Crash]

Speed/Distance Stock Radian Build (continued)

Structural Wing mods

With the increased weight of this build, the stock wing support just isn't going to cut it. The foam on the fuselage above the wing is thin and a failure point. To fix that, I cut 7" off the end of each wing to epoxy to the fuselage. The stock main spar is probably ok, but too thin for my taste. I went to the local hobby shop to find something of equal diameter but with a much thicker sidewall. Because the wings no longer "plug" into the fuselage, they can freely spin around the main spar, so they need some support near the trailing edge. We need to melt a new spar hole through the wings for this support spar. This spar doesn't have to be thick, it doesn't see any significant load, and is just there for wing alignment. Here's how I accomplish that:

Build a jig out of balsa and aluminum angle to use as guide for making spar holes.




I use 1/4" diameter stainless steel rod. Any smaller diameter and the rod is too flexible to accurately push a straight line with. Heat up the tip of the rod with a heat gun and get it EXTREMELY hot. The hotter it is, the better results you will have. Don't force the rod through the foam, if its hot enough it will go through on its own. You will probably only get 2" per heat cycle before it gets too cool to keep pushing. When you have to apply significant pressure on the rod to melt through is when the rod can flex and not end up with a straight line. But at the same time don't sit in one spot too long because it can make the hole wider than you want.

Since the 1/4" rod makes a big hole, bigger diameter than neccessary for a carbon spar, because of weight and cost, I used some plastic tubes from HobbyTown to "shrink" the hole. This also makes the rods easier to insert





The end result is to end up with something like this



All you have to do now is slide each wing half on, and secure them with a small piece of tape/velcro/whatever method you prefer

Pan and Tilt

On this build you will want to move the P&T to the top of the fuselage since we are going to run out of room in the canopy, not to mention a little weight toward the back won't hurt to help compensate for the 5000mah.

I used those same plastic tubes that I used in the wing spar construction (larger diameter obviously) to route my servo and cameras through the fuselage. Used the same metal rod/heat gun technique to make the hole



So you can end up with something like this

[Crash]

Speed/Distance Stock Radian Build (continued)

Fuselage/Tail Structural mods

Since this plane will be seeing higher speeds and more load from the weight, the tail needed beefed up a little bit. Since the servos got moved to the tail, we no longer need the pushrod tubes. Pull those off and remove the glue/silicon residue that held them on. Continue the cutout from the pushrod tubes all the way to the back of the vertical stabilizer. CA carbon fiber/fiberglass (glass is preferred) tubes to create an I-beam structure. This will give you a rock solid tail structure with no flex.

On the horizontal stabilizer I created the same I-beam structure by placing another CF strip directly on top of the stock CF spar to make the horizontal stab more rigid. Draw a line on top of the stabilizer where stock spar lies. Use a hobby knife and ruler to score the "film" and remove it where the new spar will lay. Use the edge of your new flat CF spar to compress the foam underneath so the spar will sit flush with the top of the skin. You don't want to disrupt the airflow going over the elevator because you will feel it at slow speeds, like flaring to land, and will render the elevator useless.

Both mods should end up looking like this



VTx Placement

Nothing really changes about the way the VTx is placed compared to the lightweight build. The same rules apply to getting the VTx antenna higher. It was in this build configuration that I noticed issues with video loss on the return trip home.

The only thing different I did different is embedd the VTx into the fuselage. Because the fuselage/tail is stronger, some foam can be removed without affecting anything. I also made a channel for the VTx wire harness extension to sit in so that its flush in the fuselage.



GPS sensor placement and wire routing

Since we are going places with this build, an OSD is very useful. I placed the GPS sensor on one of the "inboard" wing panels. I used the same method for creating spar holes to make an additional hole to run the GPS wires through the wing and back into the fuselage. I did it on the inboard "wings" so that I don't have to route the GPS wires and plug them in every time I went fly. I also inserted a plastic tube into this hole so that the GPS sensor wires/connector would be easier to feed through. Look at the picture in the fuselage/tail structural mods section for reference.

OSD placement and video system wiring

A picture is worth a thousand words




-Current sensor is attached to ESC battery leads that is routed from outside of the fuselage.
-Skylark Tiny OSD
-Dimension Engineering step down regulator referenced earlier in the thread
-microphone
-power and ground distribution blocks. Don't ask where to get them, we had them leftover from a project at work. If I find where to get them, I will link them. It just makes it cleaned than having 6 wires twisted together and a giant blob of solder, but both are equally effective
-all of this plugs in from the balance port connector off the battery

[Crash]

Speed/Distance Radian Pro build

Very few things change between the Speed/Distance Stock build and the Pro build.

Wing mod

With the Pro, you won't be doing the wing structure mod as seen above. All I did was ditch the stock spar for the same beefier spar discussed in the previous build. If the spar doesn't fit through the hole in the molded plastic piece on the fuselage, use the metal rod/heatgun technique to melt away some of that plastic.

I soldered on extensions for the aileron servos much like I did the tail servos in the previous build. Once less connection, one less failure point. I have to use servo extensions to go from the RC Rx, through the fuselage, to the wings but thats the only connection I have. I chose to do that instead of soldering wire extensions to go all the way from the servos to the RC Rx so that I don't have to route them through the fuselage every time I fly. Its just two connections per wing at the wing root. Luckily, my car has enough interior room that I never have to pull the wings to get the plane in.

Pan and Tilt

I use the same technique as the above build for P&T and routing wires through the plastic tube. I just wanted to make a note that you will have to offset the pan servo and the platic tube for wire routing just a little off center. There is a plastic beam that runs centered down the fuselage to strengthen the wing saddle area.

Conclusion

Now that it's all said and done, if I was building a Radian to fly under 2 miles and just for casual flying, I would do the lightweight stock build. Its a fast, simple, inexpensive build. Because it is so lightweight and not as stiff/rigid as the other builds, it can take rough landings and ditching the plane over a mile away with minimal damage. Setup your failsafes for a wide, flat turn and there is a good chance your plane will be undamaged sitting off the side of the road. I've had a lot of good times on that build and its a blast to let go of the controls and watch the plane keep tracking straight. Its really a hands off plane.

If I wanted to go distance and get there a lot faster and more efficiently, I would build the Radian Pro vs the stock model. I provided the information for each in case you already have a stock Radian, or don't wont the complexity of airleron/s flaps, but if I had to do it all over again, Pro all the way. The build is so much faster than the stock version because you don't have to do the wing mods. I think the Pro flys smoother and just as slow as the stock version. In fact, I think it floats better. The polyhedral/elliptical wing tips on the stock Radian provide stability and are neccessary for the rudder to work properly. The downside to those curved up wingtips is loss of lift. That's pretty much wing area you can write off when doing wing loading calculations. With the flat wings of the Pro, you're getting all that wing area back in useful lift. Of course the pro isn't as self recovering as the stock version, with the amount of weight you carry on these heavy builds, you don't really get those self recovering charatceristics anyways.

The flaps on the Pro are awesome! Great for bleeding off speed for precision landings. These heavy builds like to glide forever and hard to get down in a small area, flaps make this easy!

Another advantage to the Pro is the quality of the foam. Its the same foam as the stock Radian, but at a higher density which makes it more dent resistant and stronger. Here is some pics of the 4 Radian build I have done




Radian #1
-Stock Radian airframe, lightweight build. It can still carry some weight in this configuration, pic was taken carrying a Kodak Zi8 under the wing and test flying Beladog's GVS camera out on the wing
-It later got reconfigured into a night flyer





Radian #2
-Speed/Distance Stock Radian Build
-Several pictures of it's build was used in this thread but I never did get a fully assembled photo. But this is the most important picture of this build for this thread. It proves that my wing/fuselage/tail structural mods work! Full throttle spiraling crash at 60+MPH. It was a VERY violent crash, destroyed my GVS cam from Beladog, broke a Aeronaut 11x6 carbon blade at the hub (like broke the blade itself, not the plastic spinner/hub), left a motor impression in the 3s 5000, and the rest of the carnage above. I'll share those stories another time...



Radian #3
-Speed/Distance Stock Radian Build
-It had a short life. Had been out of FPV for 2 months, so with a little motivation from Sentry being pissed he couldn't come fly with me, I knocked out the build over a weekend. He came up to fly with me the next weekend. While pushing some range in a noisy environment, lost video link 3.4 miles out at 2,000ft. Again, proves my wing mod works lol



Radian #4
-Speed/Distance Radian Pro build
-After crashing #3 we made a quick trip to the hobby shop to get a new airframe. They were all out of the stock Radian, so I picked up the Pro and I couldn't be happier. Sentry stayed the night after promising him I would have a plane ready by the morning. He didn't think I could pull it off, but I was determined. Got started about 9pm and finished at 6am, just enough time to get a few hours and spend the day flying with him.
-This one helped me get my personal best range record of 4 miles. It can do MUCH more than that. Flew 4 miles out, 4 miles back to me, 2.5 miles out to another spot, and 2.5 back to land. 13 miles round trip in 22 min on 3200mah. That was powered flight the whole time, very little gliding, wasn't trying to be efficient at all

[Wildman]

Hey Crash,
That's some solid, creative, investigative work that you've done for the Radian community!
I've only flown one of our club member's Radian for about 5 minutes, from launch to landing.
I want to fly my Radian Pro BNF as is, and get used to the way it handles.
I'll post a review too, once I have some flight time on her.
Any modifications would happen next year.

Thanks, Wildman

[Crash]

Alright guys, I FINALLY got everything typed up and all the pictures uploaded. I'll work on real soon editing some of the videos I have to show off the flying characteristics of the Radian and what kind of performance it has!

[Pen]

Great write-ups crash!!! I'll have to say a low watt pencil iron does work great for melting foam though. You need to be very carfull with loctite on the motor mount screws too. If you get any loctite on the plastic firewall, it will deteriorate the plastic and your motor can self-eject.

I have test flown my radian with 5700 mahs of battery and it flies pretty good in 10+ mph wind. Looking forward to doing a tandem long range radian flight with you.

-darren

[Crash]

Thanks for the loctite info, removed it from the build data. We definitely need to together and fly tandem soon!

[turdsurfer]

Thanks for the guide. I built a light FPV Radian too last spring, but used a 1300mah battery and had thermal flights of up to an hour with it: http://www.rcgroups.com/forums/showthread.php?t=1458620
Using an OSD with current sensor is important if you fly thermals a lot because then it's the VTX that is the main power consumer and not the motor (so tapping power from the balance connector is no good). I also noticed how much trouble the light Radian has penetrating head winds, but of course I only navigate away into head winds (and try to keep low = less wind) and fly back with a tail wind. In my next Radian (Pro) FPV build, I'm going to use a RVOSD v5 and hopefully I can pack a heavier battery into it too. Oh yes, about the Pro version, the flaps and aileron cut outs give the wings less torsional stiffness which gave me problems when flying fast (until I applied strapping tape diagonally to the wings). All-in-all I think the standard Radian is best for FPV, unless it's close-in slope soaring you're doing.