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Introduction to RC flight through unplanned landings

#1
Saw what Flite Test was doing with foam board and it finally seemed like RC airplanes were approachable.

Bought a flite test explorer kit, a DX6e transmitter and receiver, and a power pack C and overlooked the fact that the kit required a 9x6 prop and modified the power pod to use the 10 inch prop. I was excited to get it in the air that weekend so I didn't make the sensible decision and switch to the 9 and stick with the plans. While trying to keep the thrust vector still going through the cg, I translated it up as high as I could go. 20191101_191820.jpg 20191101_191831.jpg

I remember feeling like the plane was a little tail heavy compared to the suggested balance, but let the excitement get to me again. It flew but was way too sensitive in pitch, and after the hand launch it immediately started violently pitching up, stalling and smacking the ground, and the tail boom got a big slash from the prop on impact.

So I swapped to the 9 inch prop that a friend helped provide, threw some wood in the nose, and taped over the slash in the tail boom and got it in the air again! It flew well enough but I suddenly lost power and touched down somewhat gently in tall grass. The prop had come loose.

I tightened the prop, checked my C.R.A.P. again, and launched again. I flew half of a pattern trying to gain altitude at full throttle when my patch job on the tail boom must have come undone. It pitched down hard at full throttle and augered in. The nose was obliterated, the core was torn, the tail boom completely broke in half. It was a sad moment but in the end I knew I could just make another. I already bought spare foam board and all the electronics were in great condition.

Even though I didn't get a good flight in, I've learned a lot about what went wrong, how much of a component my impatient decisions played a part in the loss of my first plane, and I'm already on my way to building my own flying wing with cues from the flite test spear and arrow designs. 20191106_015449.jpg
 

FastCrash45

Well-known member
#2
Saw what Flite Test was doing with foam board and it finally seemed like RC airplanes were approachable.

Bought a flite test explorer kit, a DX6e transmitter and receiver, and a power pack C and overlooked the fact that the kit required a 9x6 prop and modified the power pod to use the 10 inch prop. I was excited to get it in the air that weekend so I didn't make the sensible decision and switch to the 9 and stick with the plans. While trying to keep the thrust vector still going through the cg, I translated it up as high as I could go. View attachment 147401 View attachment 147403

I remember feeling like the plane was a little tail heavy compared to the suggested balance, but let the excitement get to me again. It flew but was way too sensitive in pitch, and after the hand launch it immediately started violently pitching up, stalling and smacking the ground, and the tail boom got a big slash from the prop on impact.

So I swapped to the 9 inch prop that a friend helped provide, threw some wood in the nose, and taped over the slash in the tail boom and got it in the air again! It flew well enough but I suddenly lost power and touched down somewhat gently in tall grass. The prop had come loose.

I tightened the prop, checked my C.R.A.P. again, and launched again. I flew half of a pattern trying to gain altitude at full throttle when my patch job on the tail boom must have come undone. It pitched down hard at full throttle and augered in. The nose was obliterated, the core was torn, the tail boom completely broke in half. It was a sad moment but in the end I knew I could just make another. I already bought spare foam board and all the electronics were in great condition.

Even though I didn't get a good flight in, I've learned a lot about what went wrong, how much of a component my impatient decisions played a part in the loss of my first plane, and I'm already on my way to building my own flying wing with cues from the flite test spear and arrow designs. View attachment 147402
This is what the hobby is about, learning and having fun doing it. Every flight will be a new experience and teach you more each time. I started with balsa kits and filled many trashbags with kindling, however each flight was longer and easier. Al5hough it was kind of hard to keep the chin up after demolishing 6 months of work, you'll always improve. Now I wish I'd have known about foam board in the late 70's. 😂😉😂
 
#7
Almost ready to maiden but the cg is still further back than I would like. With one battery in the compartment. I've got space to put two more batteries on either side and into the wings but having clearance issues getting the two side-batteries in there after I built the hatch. OOPS. 20191108_012210.jpg 20191108_012219.jpg 20191108_012236.jpg
 
#9
I’m eager to see how it flies! Good luck!
I was able to get the two batteries in either side and left the middle bay empty and the CG is perfectly where I wanted it, based on the CG calculator I used. just threw it around in the backyard and it seems to be very unstable in yaw. Yaws left, right wing gets more relative wind and lift so it rolls left hard and goes inverted. Might need to add those wingtips like the Arrow or some wing fences along the span.
 

Bricks

Well-known member
#11
Just about every wing needs wing tip plates do not forget to put in some reflex on the elevons.. If it was me trying to get CG right I would of opened up the very front and added some lead weight hot glued in, would not take as much total weight to get correct CG as lighter always flies better.
 
#12
Just about every wing needs wing tip plates do not forget to put in some reflex on the elevons.. If it was me trying to get CG right I would of opened up the very front and added some lead weight hot glued in, would not take as much total weight to get correct CG as lighter always flies better.
Only an hour ahead of you! Tossed it around and flies straight! The cubic wing load is only 2.8 with one 2200mAh battery and 3.4 with two so bringing the total weight up for wind penetration seemed like a good idea.
 

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#13
So I just had my first real flight with an Opterra 1.2m and my own wing.
Took the Opterra out to give my own design the best chance it could get and the SAFE and AS3X modes are incredibly nice for stress free flight. After my first ever run to last more than a 30 seconds, I landed with a 5 minute flight time and a happy uneventful flight.

On my first launch of my own wing, it was incredibly floaty and wanted nothing more than to pitch up despite having two 2200mAh batteries and the CG placed at the 15% mark of the mean aerodynamic chord. I added way too much reflex on the elevons. Its floaty nature allowed even an inexperienced person like myself to land flat and sustain no damage. I remembered the tools needed to whip up some new linkages and removed nearly all of the reflex with my new linkages. Launching again, it took off like a rocket, and surprisinly stable. The 9x6 prop, 2218B motor, and only 912g of weight must have a great thrust to weight ratio. I got a little carried away with the power, doing two barrel roles while climbing, and a vertical loop. Unfortunately, I went into a dive and one elevon stopped responding. It went into a vertical spiral and augered in, splitting the wing in half. All electronics are fine. I believe that a battery shifted in flight and pulled on the servo wire extensions and unplugged the servo. I really wanted to test the stall characteristics and handling at low speed but that will be for the next wing.

Lesson learned. 25 degrees of reflex is too much for this wing, and tack down all the wiring and confine the batteries with more than just a battery sized foam compartment and I think this wing could be really special.
20191110_171328.jpg
 

Bricks

Well-known member
#14
Good job reflex only needs 1/8" -3/16" depending on the wing some may need a little more, that and just how you like to fly it fast or slow and floaty like you experienced. You can change reflex in the air just use your up trim.
 
#15
Good job reflex only needs 1/8" -3/16" depending on the wing some may need a little more, that and just how you like to fly it fast or slow and floaty like you experienced. You can change reflex in the air just use your up trim.
I had consumed my entire trim range trying to make it flyable on that first run. 25 degrees was simply too much.
 

BATTLEAXE

Well-known member
#16
You have great tenacity my friend, your wing looks great and the idea is solid. You are not wrong by saying 25 degrees is to much, at most would be 10 degrees, the rest can be trimmed in the maiden flight given the relative airspeed. You said you have modeled this wing after the Arrow and the Spear, both of which I have built a couple times. I found the Arrow really tight for space with the electronics and the Spear is at the other end of the spectrum for having a whack load of room for everything you need and then some. Try something like the Spear, I actually downsized one to 85% and modified it to fit a 9" prop and runs as a AET set up as opposed to elevons. I even did the same to an Arrow as well but kept it full size. Makes it easier to handle on launch.

This is the Arrow 20191101_223626.jpg

Here is the Spear
20191105_163920.jpg

I do like the elevons on other models but on these I found the stability to be way better as an AET set up. Of coarse you don't have to do this but I will say the Spear will give you way more room to play with the electronics and CG balance, and gives you some crumple space to protect the electronics as well
 

BATTLEAXE

Well-known member
#17
I just noticed you are using 5g servos as well, and the both are pointing in the same direction. 5g servos might be a bit weak given the size of the control surfaces, and it helps to use a mechanical differential drag advantage to the up swing of the elevons, the direction of the horns isn't a huge issue as long as they work in the right direction, just looks odd lol. Differential drag allows for more upswing then down swing helping your yaw authority in a turn when you bank into a turn. More exposure on the inside elevon will create more drag then the outside elevon creating the turn for you, this can also be achieved in your transmitter as well in the differential menu when you select elevons on your Spektrum.
 
#18
I just noticed you are using 5g servos as well, and the both are pointing in the same direction. 5g servos might be a bit weak given the size of the control surfaces, and it helps to use a mechanical differential drag advantage to the up swing of the elevons, the direction of the horns isn't a huge issue as long as they work in the right direction, just looks odd lol. Differential drag allows for more upswing then down swing helping your yaw authority in a turn when you bank into a turn. More exposure on the inside elevon will create more drag then the outside elevon creating the turn for you, this can also be achieved in your transmitter as well in the differential menu when you select elevons on your Spektrum.
These are the 9g ES08AII servos that come in the powerpack C for my ill-fated FT Explorer. They seemed to do the job but given the speed this can get to in a dive and the size of my control surfaces, I'm thinking an upgrade may be in order just to be sure it won't be a problem. And I had the control horns pointing in the same direction because the control horns on the servos seem to have an odd number of splines, and I couldn't get them pointing at exactly 90 degrees when I put them on the other side. I had already glued the servos in the same direction as well.
 
#19
https://www.motionrc.com/collection...-metal-gear-servo-with-300mm-lead-md31172-300 Here are some badass cheap metal gear servos. I will send you refund money if you can get anything c pack or less to power it. They are also super precise and I recommend putting a small zip tie around the push rods and glueing it down to your plane. If you get them make sure to put the push rod on the innermost hole of the control horn. It is just a bigger servo and therefore has more travel.
 

BATTLEAXE

Well-known member
#20
These are the 9g ES08AII servos that come in the powerpack C for my ill-fated FT Explorer. They seemed to do the job but given the speed this can get to in a dive and the size of my control surfaces, I'm thinking an upgrade may be in order just to be sure it won't be a problem. And I had the control horns pointing in the same direction because the control horns on the servos seem to have an odd number of splines, and I couldn't get them pointing at exactly 90 degrees when I put them on the other side. I had already glued the servos in the same direction as well.
Holy Crap what is the wingspan on that thing, almost Kraken size?! They look like 5g given the perspective of the picture. Is it carrying a 9" prop on there? I has to be big. The Spear is a 41" wingspan, the Arrow is like 30" give or take a couple inches. Maybe try to downsize a bit and get it to fly good at a smaller size.

I know exactly what you are sayin about getting the splines to line up in opposite directions, pretty common with all the servos I have dealt with, actually I have never seen them line up. It doesn't really make a difference though. You do have a lot to work with in this wing given the info you have so far. To what lengths are you planning on taking this specific build? Have you built a FT wing stock to spec and flown it yet?