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Saturday, September 30, 2017

Even More Reasons To Fly The Extreme Flight 52" Extra EXP

This year was a tough one on equipment. I lost my beloved blue 52" Extra EXP when I got distracted during preflight and forgot to put in one of the wing bolts. When I have an accident like that, I stay furious at myself until I can build a replacement and forget about it. So, as you can guess, I was in a hurry to get this project on the road.

 In the mean time I had the servos serviced and along with my power system, put them in a new 52" Slick. Now I had to buy absolutely everything for the new Extra, and not that long after a crash I didn't need. I was going to have to find a way to save some jack somewhere on this deal, and once again Hitec saved the day. To help get me back in the air quickly, my friends at Hitec were kind enough to send me some Hitec HS5085MG servos, which are the digital equivalent of the HS85MGs. Since the 85MGs were great, the digital version would seem to be an upgrade, so I thought it was certainly worth a try. It's really nice not to have to buy new servos for every new plane, especially when I don't have the money anyway, so a big thanks to Hitec.

 As we saw in 52" Extra EXP__What To Do With Your Spare HS85MGs you can get away with using servos you already had left over from your 51" Slick. Just about everyone had a 51" Slick that they either crashed or wore out, and a handful of HS85MGs in the spares box. Since scratch was really short for that project, I simply had those serviced and threw them in. They have been really great, but since they served us so well in the 51" Slicks for so many years, that was not really a surprise.

 Certainly Hitec's magnificent HS5087MH are better, and the benchmark for this size plane, but I've found the HS85s have been fine. The plane is not quite as crisp in response, nor should it be considering the HS5087MH is a more expensive servo. Still, so far my HS85MG equipped Extra has been stellar, so I go into this project with a high degree of confidence.

Specs And Stuff
Mostly I have found Hitec servos suit just about everything I have flown in the last ten years, so I don't spend a lot of time pouring over specs and comparing servos trying to find that extra one ounce of torque or tenth of a second in speed. I'm not a spec guy and this isn't a tech blog. I just share what works for me.

 I just fly them hard and they either work or they don't. So far I have been happy with all my Hitec servos, but if I ever found one lacking the plan was always to upgrade to the next best Hitec servo, which so far has never been necessary. The only time I have wanted a better servo was switching from HS65MGs to HS85MGs for the elevators of my 48" EXPs, and even that wasn't strictly necessary. I just felt better with a bigger servo back there.

 However, I know some of you want these details, so here we go.............

HS-5085MG Servo Specifications
Performance Specifications
Operating Voltage Range (Volts DC) 4.8V ~ 6.0V
Speed (Second @ 60°) 0.17 ~ 0.13
Maximum Torque Range oz. / in. 50 ~ 60
Maximum Torque Range kg. / cm. 3.6 ~ 4.3
Current Draw at Idle 3 mA
No Load Operating Current Draw 290 mA
Stall Current Draw 2150 mA
Dead Band Width 2 µs
Physical Specifications
Dimensions (Inches) 1.14 x 0.51 x 1.18
Dimensions (Metric) 29.0 x 13.0 x 30.0
Weight (Ounces) 0.77
Weight (Gram) 21.9
Circuit Type G1 Programable Digital
Motor Type 3 Pole Metal Brush Ferrite
Gear Material Metal
Bearing Type Top Ball Bearing
Output Shaft (type / Ømm) Standard 24
Case Material Plastic
Dust / Water Resistance N / A
Connector Gauge (AWG) / Strand Count 28 / 20 

 Sometimes tiny, little, seemingly insignificant things make a difference. At least visually the gold label on the H5070MG servos really looks good with the black servo and Xcessories titanium anodized servo screws, but we'll have a picture of that in the set up section. This servo certainly looks like a quality piece.

Extra EXP__Testing with Hitec 5085MG Servos 2 from Doc Austin on Vimeo.

 Power System: ESC
One of the most convenient aspects of the HS85MG project was that I did not have to solder up a separate BEC, mount it, and fight with the associated rat's nest of wiring. The simpler I can make the plane, the better I like it. I can just fly instead of checking more stuff. The 5085 is also a 6 volt servo with no BEC necessary.

 Also nice for me is that I have spent ten years flying the Airboss esc with it's safety switch. When you use a separate BEC the switch no longer works, and I just cut them off to avoid confusion. However, using that switch is part of my preflight ritual sequence and I like the security it gives me.
Simplicity is also especially important for newer guys because they simply don't know how to do it, and how to set it up. I've done so many that they don't bother me any more, but I remember the first few took a lot of cursing and head scratching. The simplicity of the Xpwr 3910 motor, Airboss 80ESC and 6 volt servos makes the power system a bolt on, plug in and fly system. About the only thing you can get wrong is the motor polarity, but you won't be going very far with the motor running backwards, except maybe going backwards, that is.

Since I have written so much about this power system in previous articles, I am going to be lazy and refer you to 52" Extra EXP__Synergistic Integration and 52" Slick EXP__ The New Classic report. This installation is so simple that the ESC location is already figured out for you. I use a 1/4" balsa block to lift the ESC up enough to clear the first fuselage former, and I can slide it back a little more.. This gives you a little more slack in the wire and deans plug on the other end where you plug the ESC into the battery. It also shifts the weight back a little so I don't have to jam the battery all the way back.
 Extreme Flight also made little slots in the tray to accommodate the zip tie for securing the ESC. Both the Extra and Slick are loaded with nice features like these. and you really have to build one of these to appreciate how much thought went into these planes.

 Here's the balsa block I glue to the bottom of the motor box. I cut it to fit snugly between the carbon rails and glue it in with Zap medium CA. I seal the top of the block with thin CA and that makes the Velcro really stick down. Notice the bottom front of the motorbox where it is relieved to allow the motor wires to clear. This is just one of hundreds of little details you will find on these planes.

 By mounting the ESC on the bottom of the motorbox you get a super clean installation, the switch wires stay neatly out of the way, the wire to the receiver is just the right length, and the deans connector comes out a little further back to give you a little more wire to work with. The ESC is also in there pretty snugly and not going to go anywhere. That and it just looks right. It's a win all the way around.

Power System: Motor
I'm going to cheat here and copy/paste the information on the Xpwr 3910 motor. If you have already read 52" Extra EXP__Synergistic Integration you can skip the next part and not miss anything.
Motor: The motor of choice for this plane is a product of Extreme Flight's Extreme Power division (Xpwr). When the motor first became available I wanted to become familiar with it, so I tested it in my 48" Extra and MXS. It is smooth running, cool and reliable, just like the Torque motors I love so much.

 The 52" Extra and Xpwr 3910 were designed to work together as an integrated package. This motor delivers absolutely Xtreme sick power, 1068 watts at 72 amps (Xoar 14/8). When I tested this motor in a 48" Extra it was so overpowered that I was hanging on the entire time, so it ought to be perfect for the 52". 

Designed to work with either a Xoar or Falcon 14.8 or 15/7 propeller, the 3910 accelerates so quickly you can almost feel the plane trying to rip the transmitter out of your hands. This is the most righteously powerful thing I have ever flown.

 The sound of the 3910 is a little different to what we are used to. It is quieter and sounds more like (metaphorically speaking) a Mercedes than a Ferrari. I does not quite scream like a 2814, but it's sound is a little more muted and lower pitched. Perhaps this is because it's not working nearly as hard, which leads me to believe it could be even more reliable than what we are used to flying. More reliability was certainly not necessary, but it's always a good thing.

 Aside from being shorter, and bigger in diameter than what we are used to seeing in the 48s, there's really noting different in the way you install and use the 3910 in the 52" Extra. The mount appears to be the same one as used on the Torque 4016/500 MkII motors we fly in the 60" planes, so again I am happy to be working with something so familiar.

 The motor simply bolts straight to the Extra's firewall (using the included X mount) with no additional fitting or cutting. You just install it the same way we have been doing all along with all the other EXPs. This is not really a surprise because the two were designed to work as one integrated unit.

 Xcessories And Stuff
You can order your Extra with absolutely everything you will need, from the beautiful Extreme Flight anodized aluminum servo arms, the correct length Extreme Flight Xcessories Servo Extensions and even the Extreme Flight Xcessories Anodized Titanium Colored Socket Head Screws for installing your servos. As long as you have a receiver, you can order everything you need directly from Extreme Flight, get it all in one package and only pay the postage on one box.


While the Slick 580 came with Xcessories new Socket Head mounting Screws for attaching the cowling, the Extra was an earlier release and still comes with the silver colored Phillips head screws. Fortunately Extreme Flight has recently made these available separately and they are really nice pieces.

 As you can see, the head has a built in washer, It's all cast as one piece, so when working with the screws you can't lose the washer. The allen head is also the same size as Xcessories servo mounting screws, and the cinch bolt on the Xcessories arm. With the exception of the servo arm mounting screw, you can preflight the entire outside of the plane with a single allen tool. All we need now is an Xcessories allen bolt to hold the servo arm on, but I have mentioned this to The Boss and hopefully he is working on that.

 One of my dirty little secrets is that I drill the upper left had cowl screw first, and then install. If everything lines up perfectly I drill the rest, but if not, I am usually close enough that I can simply elongate the hole whatever direction I need to move the cowling. I tighten that down and after that it's really hard to miss getting the others just right. With the large head on this screw, you can cover that first mistake up pretty easily......and that's the secret to how I get my cowl alignment so perfect and my spacing to the spinner so tight.

 I also love the new Xcessories twisted servo extensions. Most importantly they work, but also important is that they look great, and the plane's order page specifies the ones you need to give you the perfect length to get a clean radio system install.

 Making the whole project a one stop affair, you can order absolutely everything you need for the plane (except the receiver, but Extreme Flight is working on that) directly from Extreme Flight, get it all in one box and avoid paying multiple shipping costs. Xcessories are also competitively priced, so by skipping those extra shipping charges, you actually get a better product for less money.

Batteries Extreme Flight recommends a 4s 3000-3300 mah capacity pack, so the perfect match for me is the new Thunder Power 4s 3300 70C Rampage packs. I've been perfectly pleased with my 55C Lightning packs, but I have not been able to kill any of them even through two years of blistering Florida summers. As such, I haven't had the opportunity to try Thunder Power's latest offerings, but we're going to correct that now with these Rampage packs. Being a high discharge rating means I can run them a little harder and maybe expect a little longer lifespan. Having more power is never a bad thing either.

I like the 12C charge rate because I can safely charge them at up to 39.6 amps. My Thunder Power
TP820CD charger puts out 20 amps per side, which means the bvest I can do is charge them at roughly half the maximum rate. While these packs are designed to charge at the full 12C rating, it never hurts to take it easy on your equipment.  I am guessing I can charge one of these in 10-12 minutes. If you have a 40 amp charger it would be frightening how quickly you could top one of these off!

 At 353 grams, they are not that much heavier than the 2700 packs I am using in my 48s, and light weight is always a plus. They are also not much bigger in physical size either, so you can move them around quite a bit to get your CG where you want it.

The specs below were copy/paste from Thunder Power's website. I kind of doubt I will be spiking the battery at 462 amps, so it's nice to have that much more safety margin than you really need. Under stressed equipment is more reliable and lives longer, and with money being tight, I've got to get through next year on just two packs. It makes sense to get the mega battery to start with instead of replacing cheaper packs more often,

Mounting Pilot X
This seems to be an area that gives the new guys a lot of trouble. It's not because this procedure is hard .... it's not .... you just have to know how to do it. There are a lot of different ways to do this, but I learned a lot of my building tricks on 3DHS planes, and I still use the method that was in those manuals at the time.

 On the Slick, Pilot X fits beautifully, but it's a little bit tighter on the Extra because the canopy sits a little lower, especially at the rear where we want to put him. Of course, we are trying to put a 1/5th scale pilot into what is essentially a 1/8th scale plane, so a little improvisation was going to be necessary.

 You could easily glue the pilot straight to the canopy rails because it fits fine there. Problem is, that looks kind of cheesy and makes the pilot look like an afterthought. I prefer to mount it on a balsa sheet. For this I used something out of my scrap box and I don't even know what thickness it is. I'm guessing it's something like 3/16 or so. Whatever it is, it had to be thin because we couldn't afford to raise the pilot up much.

 I use the canopy itself as a pattern and draw the lines on the wood with a sharpie, then cut to shape. Here it's hard to get it exactly right, so you may have to trim the wood. It's handy to have a nice straight ruler and sharp Xacto for this.

 I learned building model cars that black is a poor color because it looks fake. Of course, we are putting a fake pilot into a fake scale plane, but you don't want it to look like that. I found that dark greys or gunmetal colors looked more real, and for this pilot I used Model Master Titanium colored paint. Here it looks black, but it's just a trick of the camera. It's really more like a really dark gun metal.

I drilled a hole in the base and screwed the Pilot X to it., then secured it with a self tapping screw. Once I trial fit the assembly into the canopy and was satisfied with the fit and placement, I ran some CA under the pilot and let it wick in.

 Finally, I slipped the assembly back in and carefully ran a bead of thin CA where the base meets canopy rails. Be careful to use a drop at a time. A spill here would make an awful mess out of things. The Pilot ended up a little forward of where I wanted him, but the slope of the canopy makes that a little too tight. Where he is still looks pretty good, so I am happy enough with it.

As you can see, the build is going quite well. Usually I like to do a gonzo build session and do it all in seven or eight straight hours. I'll get all but a few things done, and then knock it off when I start to feel like I'm getting tired and not doing my best work. Then come back fresh, and finish up with plenty of time and energy to exhaustively check everything.

 This time my shop is trashed from getting ready for the hurricane, so I don't have a suitable building area. I've just got the kitchen bar, and limited time, so I am just picking away at the small jobs and only working 20 or 30 minutes at a time. I am always fresh when I start working. As a result, all of it so far is my best work and I am really pleased with it. This just reinforces my belief that you have to slow down, be patient, and not really care how long it takes. The result is more important that the time it takes to achieve it.

Set Up
There is not much different here from my other 52" planes. Since the pushrods are all the same length, and the servos bays are cut out and predrilled, it would be hard to get wrong even if you tried.

The plane flies fine with the recommended Xcessories custom G10 extension, but my style of flying has evolved to where I can actually use the additional surface movement. For most people I recommend using the G10 arm and I am sure you'll be happy with that. I flew my first one like that for awhile and loved it, but went for more throw just to see if it worked better. Pitch authority is not much different, but with more throw you do get a harder braking action when you rotate the plane. I find this useful for killing speed instantly so I can set up my slow speed maneuvers without the need to bleed the speed bleed off with a longer glide path. I can fly it right up to me and park it right in front of the camera, which makes good video.

Here you can see I use the log arm from the Hitec PN557090 servo arm set. Right now I am getting about 85 degrees, but I can still trim a little bit off the rear of the fuse to allow the connecting arm between the elevator halves to move more. At this time, I've got my end points set at 135%, so we are almost there.

 I was really careful with my hinging on this plane. I made sure I could get a full 90 degrees of elevator throw. I had to drop the servo down about 1/16" because the Xcessories 1.25 servo arm was just barely rubbing on the bottom of the stab a little, but then again, it wasn't designed to use that much arm anyway. Fixing this was no big deal and really not even a minor annoyance. I used an emery board to sand off just a little of the bottom edge of the servo opening, plugged the mounting holes with thin CA and toothpicks, and drilled new mounting holes. I've done all three of my Extras this way and it works beautifully.

 Again, I used the Hitec PN5570 arm, this tine the outer holes on the longest one. The Extra is so pitch stable that the additional throw doesn't make the plane any more difficult to fly smoothly, but it does make it a bit more agile. It also makes a jolly good speed brake, but you had better know what you are doing before you try that down low.
Here we deviate just a little from the manual. I have used the Xcessories 1.25 arms on previous 52" Extras, but that was so much throw I had a little trouble being smooth with it. Since my radio only has a high and low rate, there is no mid rate for me to use. I either have high or low, and I set up my high rate so I can fly it for everything but precision work. I turned my end points back to 100% and that made the plane more to my liking, but I hated giving up the extra servo resolution of maxxing out my set up.
I finally fell back to the reliable Hitec PN55709 short 7/8" arms, and maxed my travel adjustment (end points). This gives me about 35 degrees of aileron, which is fine for me. I can fly this smoothly, so this was a good adjustment. However, I love all of the Xcessories and love using the Xcessories servo arms. Since we don't currently have a 7/8" arm, I was going to have to improvise.

If you have triple rates on your radio, I suggest you use the high and low rate from the manual, and on the mid rate dial the aileron back to 33-35 degrees or so.

I found the PN55809 to be perfect for the rudder on both my 52" Extras and Slicks, so I used one here as well. For some reason I can't seem to explain, on this plane I had to use the second hole from the outside instead of the outside hole. Doesn't make any sense, but it works.


Extra EXP__Testing with Hitec 5085MG Servos 3 from Doc Austin on Vimeo.
Extra EXP__Testing with Hitec 5085MG Servos 3 from Doc Austin on Vimeo.

Having had such good results from the HS85MG equipped Extra, I knew this would be a solid project. There's not much to say about how well these servos work, because they just work, and do what they are supposed to do. That's about all you can ask from any product and more than a lot of other ones deliver. Personally I don't want my servos to sing and I don't want them to dance. I just want them to do the job with a high degree of reliability, and basically stay invisible. Like all my Hitec servos, the HS5085MG fits the bill rather well here, and I am always delighted with a product that just gets it done with no fuss or drama.

This is why I never even consider a servo other than Hitec. I trust the company, I trust the brand, and I certainly trust the product to protect the rest of my investment in the plane. What possible other reason could you have for choosing a servo?

 Speed is a little better than the 85mg, and not quite as good as the 5087mh . Centering seems to fit in the mold too, being better than the 85s and not quite as locked in as the 5087mh. We knew this going in, from reading the specs, but in the air it's a little hard to tell much difference. All these servos work so well that you can't tell them apart until you start really hammering the crap out of them in full throttle blenders, walls and parachutes. Then the higher voltage and more expensive HS5087MH servos deliver a little more speed, grunt and holding power, but most people just don't fly that hard. You can tell the difference, but then again, it's only at the outer limits where even the most daring pilots don't spend a lot of time.

 Since I am not a servo expert, it's hard to make a definitive decision on what servo is best for different types of flying, but I do know a little about piloting, and I am much more than reasonably happy with all three versions of the 85 size servo. The longevity, performance and reliability of the 85 class servos is industry standard.

So far I'm about a dozen flights in with this plane and I have to admit I am really pleased with these servos. They are especially impressive in how they stay trimmed and center so well. I have not touched the trims since the initial test flight and the p[lane has stayed locked in solid. Smaller servos can center poorly or drift off trim, but these have been exceptionally solid.


1 comment:

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