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As Yet Unnamed RC Paper Airplane - Build Log

Screwball

Active member
#1
So this thread was spawned by Mayan's excellent "Paper Airplanes to RC the Challenge". You should check it out.

Here I will document my contribution to his challenge. Last year I built a 4:1 scale RC version of John Collins's awesome paper airplane, "Suzanne".

I absolutely love it, and if I had to pick only one from the hangar this would be it. Fortunately I don't have to pick, so I'm gonna build me another one, and there's nothing you can do to stop me. So, there.

This plane will be a bit smaller, at 3:1 scale, which fits nicely on a single sheet of DTFB. I've made TONS of way simplified chuck gliders of this basic shape at this scale. I usually take at least one with me to the park where I fly, and here's why:

I'll show up at the park with my RC airplanes and start setting up. Some not-my-kid gets curious and wanders over. They start asking a bunch of questions, but we both know what they really want is to fly my plane. Hey. I get it. I was just like that when I was a kid. (Oh, who am I kidding? I'm still just like that. Haven't changed a bit...) So, I'm sympathetic. I really do want to let this kid in on all the fun.*

...but then a little voice inside my head pipes up-
Q: Do you know how model airplanes are like underwear?
A: They're very personal, and sharing them with complete strangers is usually just plain dangerous, and dumb.

Good point. Turns out the guy in my head (this time, anyway) is the voice of reason. Fortunately, for the fun and safety of all concerned, I brought along a pretty dang cool, but still totally harmless and semi-disposable chuck glider with me, for just such an eventuality.

So... After a quick check-in and nod of approval from the kid's parental unit**, I hand over the chuckie and say "O.K. kid. I'll start you off with this one. Here's how you throw it ('WOW Mister! That went really far!'). Here's how you can change what it does ('COOL! It did a loop!'). Now, how about you give it a try? Go ahead. Go for it! Have fun!" The kid's thrilled, and my planes are unharmed (that's MY job). Everybody wins. Usually at this point the parental-unit, or another kid, wanders over and they start playing catch. Success! two more humans infected with the flying bug...

When it's time to pack up, I tell the kid s/he can keep the glider, as long as s/he promises to SHARE with the other kids. -No. I don't know why the underwear rule doesn't apply to HER plane, but it just doesn't. okay?- I reassure the parent that it's really no big deal, brought it with me to give away, only cost me a buck, make 'em by the dozen, fla-fla-fla... They walk away thinking I'm a walking-talking-one-man STEM program, and a real swell guy, to boot (which I am, BTW).

But -most importantly- They don't call the fuzz on me when I fly my planes at the park! Genius. Pure Genius. Right guys? Right...? Uhh... guys?



But anyway, I digress...

The point is I know how to build these things; I know how to trim them; I know how they balance; I know how they're supposed to fly. Still, every time I've tried to electrify one of these little guys, it ends up ...squirrelly. I mean really squirrelly.

But not this time. THIS time will be different! (he says every time)

ANYWAY... Here's a short video of the chuck glider version in action:
My daughter (age 7) made and decorated this one. She calls it "The Poop Plane" (then giggles into her hand) What can I say? She IS my daughter...




*If you've never taught a child how they can make stuff fly, you my friend are missing out. Do this:
1. Make a simple chuck-glider of your choice; almost any will do.
2. Find a kid; almost any will do.
3. GET THEIR PARENT'S PERMISSION!
4. Go have a game of catch.
Trust me. You will not regret it. It's really good medicine.

**I never thought to try this while wearing The Joker cosplay rig. I wonder how that would go... (sound cue: approaching sirens)
 
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Screwball

Active member
#2
...and away we go!

Searching for inspiration to springboard this build, I went looking through my son's book bag last night (What!? It's worked before, so why not?) and found this:

Agenda compressed.jpg Folded Agenda compressed.jpg

EUREKA! Serendipity? ...or Kismet? You be the judge. It's time for me to go to work.

Blank Slate.jpg Plans Drawn.jpg

Lofting complete. Now time for some Visual Interest. Start with a blank sheet of paper...

Lines.jpg More Lines.jpg




add a few words...

More Words.jpg

and a bit more...

Words.jpg
Now we're getting somewhere!


...to be continued.
 

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Screwball

Active member
#3
Super Groundhog Sunday was also my wife's birthday. Granting her Birthday wish, we had a Pajama Day at the house. It was awesome. We played games, watched a movie, she showed the kids the top-secret special move in Super Mario Bros. that nets 100 lives (What!?! Yup. It's there. You've heard of the Pinball Wizard? That's nothing compared to my wife on classic Nintendo. She's scary-good.) I handled all the cooking, housework, kid-bathing, etc. and read everyone to sleep with a bedtime story...
in short: I didn't get much work done on the plane. No complaints here.
But, after everyone else was tucked in and snuggley, I DID tiptoe down to the studio for a bit...

Here's what happened:

First off I should explain the livery so far. It's all just Sharpie. It would be monumentally difficult -if not impossible- to put this scheme on after construction, but at this stage, it's a piece of ... paper.

Time to seal the edges!

Right tool.jpg

Yes, I have a covering iron, but this one works soooo much better.



Next, I marked and cut the servo locations,
work cut out.jpg

Then peeled as much paper as I could. It's strange to think about putting a plane this light on a diet, but as I plan to use an 1108 for power, I figure lighter can only be better...

peeled.jpg

Now, on to prepping the wing panels.

There's more than one way to make a bevel, and they yield different results (DUH...)

I want a smooth radius on the wing's leading edge, and a sharp corner at the wing-to-fuselage fold. So the former gets crushed, and the latter gets a classic double bevel. Like this:
Leading Edge.jpg Fuselage fold.jpg

Now let's introduce some camber to this airfoil:

camber, anyone.jpg shaping the wing skin.jpg

Typically I like to use double-sided carpet tape when joining two pieces of foam on the flat. It's super strong, couldn't be easier to work with, "cures" instantly (it is tape, after all), readily available at any hardware store, and cheap. But since this bird's on a diet, I decided for a fussier and more time-consuming but ultimately (a bit) lighter option:

tape.jpg Glue.jpg

The spar gets glued to the bottom surface of the wing. The top of the spar gets a coat of Foam-Cure, and a bead of hot glue goes into the ditch at the leading edge. Then (and here's the tricky part) the bottom of the wing stays on the table while the rest of the plane folds over it. Hang the fuselage over the side of the table, putting pressure on the fold, to introduce some tension to the top skin of the wing. Do it right, and you'll end up with a flat-bottomed, smoothly cambered airfoil.

Once the hot glue... umm... isn't hot anymore, use a gravity clamp (A.K.A. something heavy) to keep everything in place while the fancy glue dries.

fold the wing.jpg the clamp.jpg

When all that's done, do it again, but this time going round the other way, to complete the other wing assembly. When you're done you might end up with something like this:

Airfoils.jpg

Never mind about the crooked nose. We'll fix that later.

...to be continued.
 

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Screwball

Active member
#4
SO...
You may have been saying to yourself, "Hey... self... you got a minute?"*
and yourself said, "Yeah... okay... whadayawant?"

You: "It's just... He's going on about his airfoil... but..."
Yourself: "I know! Right!?! Airfoil? Schmairfoil! There's a big giant hole in his wing!!!"

Well, to satisfy the curiosities of you both I thought an explanation might be in order.

Hole-y wing Batman.jpg

For obvious aesthetic reasons I wanted to replicate the ubiquitous hole-in-the-notebook-paper. But how to poke a hole in your wing, without POKING A HOLE IN YOUR WING!?!

Time to raid the recycling bin...

plastic.jpg
(packaging for the fancy glue, as it just so happens)

O.K. This might work.
I can see through it, but the wind can't... so to speak. Next:

trace & cut.jpg

Make a disk slightly larger than the hole in the wing.

IMG_1049.jpg

Scuff it up with a bit of extra-fine steel wool, so it's still transparent but you've knocked down a bit of the shine. **

Filler.jpg

Slice a small groove at the center of the foam's thickness - a frame for our window.

slot.jpg

Carefully fill the groove with just a smidge of that fancy glue from before; pop the clear plastic disk into the groove, like the lens on a pair of cheap sunglasses. (That's the move. You either know what I'm talking about or you don't.)

...and voila! ***

Wind-X crop.jpg

Progress continues. I have since finished the basic airframe, and hope to write that up later tonight.

...to be continued.

Notes:
* I call mine "Mr. Homunculus". (1)

** (Hmmm... knockin' down a bit o' the shine. Takes me back to my days in Kentucky...)

*** Please pardon my little visual puns. So many in one image, I just couldn't resist...

(1) https://everything2.com/title/The+homunculus+problem
 

Screwball

Active member
#5
As I'm a bit behind schedule, I'll forgo my customary droll preamble, and get right to it.
(Mr. Homunculus says: "I think you got that wrong. 'Droll' means 'amusing', not 'tedious'."
Ahem... Anyway...
On to CONTROL SURFACES.

At the outset I think it's worth noting (and only fair) that there are LOTS of ways to make a hinge, and each has its own merits; this is just a way I do it. If you already have one you like, please consider skipping this entire post. It's long-winded, wonkish, and nowhere near amusing or informative enough to justify either. YOU HAVE BEEN WARNED!!!

You're still here? Suit yourself...

First I cut the elevons free from the wings,

Elevon.jpg

then set about sealing the edges. Some I'll iron, but when I want to keep them square (and don't ask me why I want that; in this case I just do*) I use a different method:

not fancy glue.jpg glue applied.jpg
Slightly thinned wood glue, a bit runny but not watery is how I like it.
While that dries... back to the ironing board.

back to the ironing board.jpg

The outer and trailing edges were already sealed (back when they were still attached to the wing) but I still need to round over the elevon's inboard edge, and iron a single bevel into the leading edge. Just line 'er up with the edge of the building board, hold the iron at a 45 deg. angle, and... ummm... iron it. (Did I actually take up space and time writing that down? What a waste...) Ironing rather than cutting the bevel makes it stiff and hard and very resistant to warpage, but also brittle and prone to impact damage. However in this location that's an unlikely event, and an easy trade-off to make.

With the edges all done, and the glue dried, it's time to actually (finally!) make the hinge. I like tape hinges. This is how I do them:

The essential bit is some good strong tape of an appropriate width, with a peel-off backing of some sort. I imagine the hobby shop would sell such a thing (if they hadn't closed {Yosemite Sam cursing sounds here}), and I know good old contact paper would do the trick, but I ain't got none. Anyway, this works just great and is actually my preferred method.

DIY hinge tape.jpg

What you're looking at is our old friend packing tape stuck to some wax paper and cut to length and width. Cheap! Easy! Perfect!
(Mr. Homunculus says: "Hey! Leave my private life out of it!")
Align the pieces, allowing about a 1/16th inch gap all 'round, tape them down (temporarily), before taping them together (permanently). Having that wax paper backing and peeling it poco-a-poco is a boon to getting everything lined up just right without sticking the tape to itself... yet (hint, hint).

aligned.jpg tape it.jpg

Squeegee the tape with a squeegee. Looks like an old gift card, I know, but trust me; it's a squeegee. (I just love that word, verb and noun alike, don't you? Squeegee...)

squeegee.jpg

Flip, fold, tape, and tape again. This step's only half-done in the picture below. To finish, take it all the way 'round, wrap it tightly, and (...wait for it...) squeegee.

tape again.jpg

OK, kids. I'm in a giving mood, so...

Here's the top-secret special move in making tape hinges that gives them 100 lives:

Really seal the hinge seam right down in that 1/16th inch gap between the trailing edge of the wing and the leading edge of the elevon, where the two pieces of tape meet sticky-to-sticky. That's it. Done.

But how? you may ask. Here's how: You're gonna need some kind of burnishing tool.
Wherever shall I get one? you may ask. Here's where:

Easy. Just look at the edge of your (here it comes again!) squeegee, say the magic word of your choice, and... (here comes mine)
Mekka-Lekka-Hi, Mekka-Hiney-Ho!**
...POOF! When the smoke clears, your (this is the last time, I promise) squeegee is now a burnisher! So get to burnishing!

locked down.jpg

Done!

full up.jpg full down.jpg



(I lied.) SQUEEGEE!!!

See? I told you you'd be better off skipping it.

...to be continued.



* If I am committing an aerodynamic blunder here, please someone set me straight.

**https://peewee.fandom.com/wiki/Jambi
 

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Wildthing

Well-known member
#6
So this thread was spawned by Mayan's excellent "Paper Airplanes to RC the Challenge". You should check it out.

Here I will document my contribution to his challenge. Last year I built a 4:1 scale RC version of John Collins's awesome paper airplane, "Suzanne". I absolutely love it, and if I had to pick only one from the hangar this would be it. Fortunately I don't have to pick, so I'm gonna build me another one, and there's nothing you can do to stop me. So, there.

This plane will be a bit smaller, at 3:1 scale, which fits nicely on a single sheet of DTFB. I've made TONS of way simplified chuck gliders of this basic shape at this scale. I usually take at least one with me to the park where I fly, and here's why:

I show up at the park with my RC airplanes and start setting up. Some not-my-kid gets curious and wanders over. They start asking questions, but what they really want is to fly (crash) my plane.
Q: Do you know how model airplanes are like underwear?
A: They're very personal, and sharing them with strangers is usually just plain dangerous, and dumb.

So... After a quick check-in and nod of approval from the kid's parental unit*, I hand over the chuckie and say "O.K. kid. Here's how you throw it. Here's how you can change what it does. Now, how about you give it a try. Go ahead. Go for it! Have fun!" The kid's thrilled, and my planes are unharmed (that's MY job). Everybody wins. When it's time to pack up, I tell the kid s/he can keep the glider, as long as s/he promises to SHARE with the other kids. -No. I don't know why the underwear rule doesn't apply to HER plane, but it just doesn't. okay?- I reassure the parent that it's actually no big deal, brought it with me to give away, only cost me a buck, make 'em by the dozen, fla-fla-fla... They walk away thinking I'm a walking-talking-one-man STEM program, and a real swell guy, to boot (which I am, BTW).

But -most importantly- They don't call the fuzz on me when I fly my planes at the park! Genius. Pure Genius. Right guys? Right...? Uhh... guys?

*Never tried this while wearing the Joker make-up. I wonder how that would go...)

But anyway, I digress...

The point is I know how to build these things; I know how to trim them; I know how they balance; I know how they're supposed to fly. Still, every time I've tried to electrify one of these little guys, it ends up ...squirrelly. I mean really squirrelly.

But not this time. THIS time will be different! (he says every time)

ANYWAY... Here's a short video of the chuck glider version in action:
My daughter (age 7) made and decorated this one. She calls it "The Poop Plane" (then giggles into her hand) What can I say? She IS my daughter...


I like your decals :ROFLMAO::ROFLMAO:
 

Screwball

Active member
#7
I like your decals :ROFLMAO::ROFLMAO:
I'll accept any blame, but I can take none of the credit. My daughter -then seven, now eight- made this plane. I cut the kit for her, and helped (supervised) with the hot glue, but otherwise it is completely her creation. From the drawings on the wings down to the selection of the brown modelling clay for the nose weight, all were entirely my daughter's ideas and her work.

I'm just so...proud? of her.
 

Screwball

Active member
#8
It's high time I carry on with this build, but before I do, I want to make one thing absolutely clear:

NONE OF THESE IDEAS ARE MINE, AND I DIDN'T INVENT ANY OF THESE TECHNIQUES.
(Please forgive me for shouting just now; I wanted to be sure that point was heard.)

We are part of -and caretakers of- a folk tradition. We've picked these things up along the way only because someone freely shared them with us, the implicit understanding (and only caveat being) that we pass them along as freely as they were received. That is all I'm trying to do. I Honor my teachers by being as free with what I've learned as they were when I learned it from them. I was born yesterday, but I stayed up all night studying.

Or, to re-phrase Sir Isaac Newton (by way of Bernard of Chartres):
I am a dwarf, and if I have seen anything at all it is by standing on the shoulders of... well... other dwarfs, who collectively far exceed the stature of any giant.

It is only because of the generosity of this community -and a real community it is- that I know anything at all, and I am proud and humbled to be a part of it.

THANK YOU.


There, I said it.
 

Screwball

Active member
#9
I don't know about you, but I've had about enough of this. Could I finish the gol' dang airframe already?

Yes. To borrow the inimitable words of the great Tone-Loc...

Here's the progress so far. All that remains (ex. installing the electronics) is to fold up the keel and form the nose. Simple, straight-forward, goes pretty quickly, but I'll do my best to take way too long over-complicating its description. Here goes...

Ready for Keel.jpg

From the off-cut make a keel-angle gauge (or jig) to hold the desired angle. This one is 4 3/4" at it's widest, which leaves just enough room (plus a smidge of clearance) for a 3" prop to sit where I want it and spin freely. Wider would increase the effective wing area, and let you swing a bigger prop, but too much and it starts to look less like a folded paper airplane and more like a weird gull-winged... somethingorother.

Keel gauge.jpg

A THIN bead of glue down the center seam (It really does take less than you think, and any squeeze-out is really hard to reach -forget scrape off- way down in that tight corner); fold, tape in the gauge, and lay flat to cool. Leave the gauge in place for the next several steps.

Center seam.jpg Chillin'.jpg

On to the wing joints. One at a time, hang a wing over the edge of the building board, run a bead of hot glue in the joint, and lay flat once more. Any squeeze-out ahead of the K-F step will join the spar to the keel (not a bad thing), but behind that any excess glue should be worked into the seam, or scraped off; it's unnecessary, heavy, and just plain ugly. Let the first side dry completely before moving on to the other, or your wings just might end up as crooked as a Louisiana politician (go ahead... ask me how I know.)

Wing Joint.jpg Chillin'.jpg



Moving on to the nose:

Way back when, I flattened the keel steps with the iron -to roughly half their original thickness- before peeling off the paper on the back. This cuts down the visual bulk here, and helps the nose pieces lay flat and meet nicely down the center. Peeling the paper before you iron will end in a big mess, and you running out to buy your wife a new iron (go ahead... ask me how I know.)*

Keel Thingy.jpg Keel Step 1.jpg

Now the nose pieces go on. The trailing and bottom edges were previously ironed shut, and the inside paper removed. The next bit's optional, but it makes alignment super simple. Lay the pieces face-down and run a piece of tape along the inside of the joint. It's just like taping together two tiny little wing panels. How cute.

Nose Piece.jpg

I'm missing a picture or two here, but here's the gist. Dry-fit the nose piece over the keel step, noting where everything touches, flat-to-flat and edge-to-edge. Apply fancy glue (or carpet tape) to those flat spots, and a bead of hot glue on the keel where the edges touch; do both sides at the same time (port & starboard). There will be a gap along the front two inches or so (where the nose piece is straight but the leading edge of the wing is curved) so don't put any hot glue there yet. We'll deal with that in a minute.

(of all the steps to not photograph...)

Just plop the nose on and line it up. Scrape (or -with an impish grin- squeegee) your seams. The hot glue will hold it all in place while the fancy glue sets.

Right at the tip of the nose, where all those triangles are supposed to meet at a single point, they won't. Close, but not quite. Mess with them until they're as close as you can get. Trim any raggedys with scissors. Poke the business end of a BBQ skewer right down the nose, to open up a little pocket.

Nose Reinforcement.jpg

Skewer comes out, glue gun tip goes in, and fill'er up!

Now, push the nozzle of the glue gun into the aforementioned gap, and give it some glue globulation. As the glue-glob cools (giving its heat to the foam, hence softening it) work the last bit of the seam closed, using your asbestos-coated fingers. If your fingertips aren't impervious to heat, the method for this step will be the same, except that... it'll hurt like a b@$t@rd. When done it looks like this:

Nose.jpg

And...

That's it! the airframe is complete!

Top.jpg Bottom.jpg
Side.jpg

Next stop: Propulsion & Controls

...to be continued.



* I would like to apologize for the blatant sexism implicit in this joke. Lots of women and girls -my own included- build model airplanes, and plenty men -myself among them- iron the clothes. Divide up the chores any which way you want. As long as it's a fair split, and the work gets done, who is anybody to judge?
 
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Screwball

Active member
#11
Thanks for the detailed steps.
I'll sure give a try a this one, but I want to finish my MiG 3 first

BTW: I like your writing style.
Aww, shucks. Thanks!
(Mr. Homunculus says, "Please, don't encourage him.")

I'm actually looking forward to giving this one a try, too! With a bit of luck -and a break in this crappy weather (endlessly not-quite-cold-enough to snow, and spitting rain) it'll be up, up, and away! by the week-end. If the little feller is actually capable of controlled flight I'll post a proper set of plans to go along with this ramble, but I don't want to be too hasty...

Good luck with your Mig!
 

Screwball

Active member
#12
Time to make some Control Horns & Push Rods!!! Yay!
Let's dive right in. Shall we?

I'm not going to spend too much time on the control horns, because -frankly- there's not much to tell. I'm using standard FT control horns, made in the usual way. I print the patterns, paste them down with Elmer's washable glue stick (the one that goes on purple and dries clear), cut 'em out, peel the pattern off, sand 'em, paint 'em, and done! (Actually, I do give a quick coating of thin CA before painting. It seems to help prevent splitting.)

Control horns.jpg Done.jpg

From the steps above I did leave out my trick for making perfectly-sized, slop-free pushrod holes in the control horns, but I'll bet -if you're really clever, and pay very close attention to the next bit- you just might figure it out on your own...


PUSH RODS:

If you've spent any time around old guys' planes you've probably already seen some variation of these control rods. Basically they are wooden dowels with wire ends. Those old guys know stuff.

Cut the pointy ends off of a couple of BBQ skewers, leaving two equal sticks about 10" long. These get taped down to the building board to keep them from rolling around (... or away) and top/center gets marked at each end. With a drill bit of the same diameter as your music wire (or paper clip, or marker flags, or whatever else you might care to use for push rods) carefully drill holes -four in all- straight through the rods at each end, about 1/2" back. I think the pictures that follow will make a lot more sense than the preceding paragraph.

Skewers.jpg Drilled.jpg

Perhaps you might be wondering, "But where in Tarnation am I s'posed to find a drill bit exactly the same size as my dang pushrod wire!?! And, you can bet your butt that if I do manage to find one it'll cost a fortune..."

Nope. Wrong, and wrong.

It won't cost you a penny, and chances are you've already got one. Some assembly required, of course.
Allow me to explain...

wire in hand.jpg

There it is. There's your drill bit. Right in the palm of my hand. A scrap piece of your pushrod wire, about two inches long. And you had no idea that all this time you were throwing away perfectly good drill bits, did you... (Nice picture, isn't it?)*

Now, as is, the chuck of your drill won't grab it. so... it ain't really much of a drill bit, now is it? Not yet...

I'll bet you've got some shrink-tube? Or at the very least a roll of heat-shrink tubing's red-headed step-brother, electrical tape. Yes? So all you gotta do is cut a piece of shrink tube about one inch long, slide it over one end of the wire, and... shrink it. It'll hold on to the wire, and the drill's chuck will hold on to it. Those of you without heat-shrink tubing have probably already guessed what to do with the electrical tape. (You guys are smart, yeah.) Now it's a drill bit!

Custom drill bit.jpg Chucked.jpg

Glad we've got THAT mystery solved... Next:

Measure once. Cut four times. Bend the ends.

Measure once.jpg Four bent wires.jpg

For the next steps we're going to need some specialty supplies. Specifically, this situation requires a chain-growth polymerizing ester of cyanoacrylic acid, as well as some 3-ply z-twist extruded poly ethylene terephthalate filament. (Good luck finding... Oh. Hmm. Never mind.)

lashing.jpg

Yup. Kragle and sewing thread. You've got some in a drawer somewhere. Go find it. Now. Moving right along...

Slide one wire through one hole. Line it up so the long bit is pointing the same direction as the stick, then lash both together tightly with the thread.

One.jpg Two.jpg

Add a few drops of Kragle, and spread it a bit to thoroughly wet-out the wrappings. (I use my finger, but there's probably at least one good reason I shouldn't...) Wait a moment for the glue to fully set, then bend the tail of the wire flat. Wrap and glue this bit too, same as before.

Glue.jpg Three.jpg

Four, glue some more.jpg

Trim off the loose string ends, re-Kraggle any bare spots you might find. Repeat the process until... well, until all four ends are treated the same way. You get the idea.

Light as a feather stiff as a board.jpg

Here's a finished composite push rod. Light as a feather, and stiff as a board! (not really, but... not bad, either. Way better than all-metal push rods, anyway.)**

Next I'll install all this stuff, and the servos, but right now I'm hungry.

...To be continued.



Notes:
*Damn! That is one raggedy old meathook hanging of the end of that wrist! Got a fair few scars there too, dontcha? Watcha been up to there, buddy? In some kinda trouble?

I swear I'm not that old, nor that grizzled. I just work with my hands... a lot.

** Did you ever play that game as a kid? I did ONCE. It kinda freaked me out.
 

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Screwball

Active member
#13
Fed, rested, and ready to continue control linkage installation.

Here's the stuff so far:
Stuff.jpg

...BUT before I install the stuff, I need to figure out HOW. I don't mean the physical act (Mr. H- to Mrs. H-:"That comes later...")*; most of us already know (or can -with little difficulty- determine) how to squeeze out some glue and plop a part into it. I'm talking about the Holy Grail of Aeromodelling. Namely:
WHICH DANG HOLE DO I USE ON THE CONTROL HORN AND/OR SERVO ARM!?!?!?!

Typically you'll get information like: "18% throws at high-rates" or "use the middle hole..." or "use the outer-most hole".
What if I'm using different servo arms? or control horns? or -EEK!- scratchbuilding a new design? None of this stuff is standardized, and trial-and-error (while fine for picking a mate) sometimes just won't cut it. So what's a person to do?

The answer to that question, my friend, is: Math.**

CONTROL THROWS
I want 36 deg. total elevon travel (18 deg. aileron, 18 deg. elevator), max servo throw is 45 deg. (some are 60 deg. Mine are cheap). Control horns are 1/2" tall. How long should my servo arm be?

The Quick-and-Dirty approach (which works quite well, in most cases): Divide control throw by servo throw, then multiply by control horn height.
In this case: (36 deg. ÷ 45 deg.) x .5 inches = .4 inches, or about 13/32"

But if you really want to do it right, bust out the trigonometry (I can almost hear that much younger me saying, "Come on! when am I ever going to need to know this?), and proceed as shown in my little scribble, below:

Control throws math.jpg

I know, I know. It looks complicated, but I promise it isn't. As long as your linkage geometry isn't... exotic (mechanical differential, hinge-line linkage offsets, and the like) this method just plain works. No more guesswork!

Anyway... nerd-fit over. Moving right along...

linkage stoppers.jpg Scuff 'em Dano!.jpg

Prepare servo arms by installing linkage stoppers in the appropriate holes, and secure nuts with threadlocker. Remove any stickers, sand, and degrease servo cases.
Create a path for the servo connection leads, as shown below.

Wire chase.jpg Slot.jpg

Pull the servo leads through, add just a dollop of the hot stuff, and press into place.

little dab'll do ya.jpg Servos installed.jpg

Measure from the keel/wing fold to the linkage stopper hole. Transfer measurement to elevon.

Measure.jpg Transfer measurements.jpg

I know. It's a bit confusing because I burned three inches on the first measurement, but look closer, they're both 1 5/8". Sheesh.

Lay the control horn along the reference marks just made, aligning the pushrod hole with the hinge line. Mark the front and back of the tab; between these marks cut a slot. Dry-fit the control horn, and allow yourself a satisfied smile.

Mark the slot.jpg open the slot.jpg

Test fit.jpg

I'm not sure why, but I've never had much luck hot-gluing in control horns. They always come loose, with rather dramatic consequences. So, I switched to using Titebond for this bit, and never looked back.

dip.jpg Horn installed.jpg

While that's drying go find something to do.
Then come back and install your pushrods. Modified Z-bends (one end); slide into the linkage stoppers (other end); push the wires through the holes and roll into place. Tighten the set screws, and admire your handiwork.

Bend.jpg This end first.jpg

No slop here.jpg Ugly servos.jpg

Let's cover up those ugly servos, shall we? Time to make some stickers!

If you look closely at the last photo, you'll see I saved the servo cut-outs from the wing panel. I want to use their skins to hide these eye-sores. I'm going with my old pal carpet tape for this job because I know the adhesive is plenty strong but won't bleed through or mess with the Sharpie decorations -as glue might. Peel the paper; stick it face up to a piece of carpet tape; trim off the excess, and you've just made a custom sticker! Dry-fit and trim as needed to clear the servo arm. When you like what you see, just peel the backing and stick 'em where they go. Pretty neat, hunh?

Peel N' Stick.jpg Clip N' Trim.jpg

Peel N' Stick again.jpg

Control linkage complete.jpg

So that's that. Not the most riveting installment, to be sure, but I think not entirely devoid of useful information (even if only to help me remember what I did right -or where I went wrong- for next time).

We're getting down to the homestretch now kiddies! build a motor mount, plug some stuff in, and away we go...

...to be continued.



Notes:
* Is this joke too blue for a family show like FliteTest? No. Really. I'm asking.

My litmus test has always been "The Bugs Bunny/Road Runner Show". My reasoning being thus:
If the gag/joke/bit/innuendo was clean enough for seven-year-old me to watch on broadcast network television (the only kind there was back then) on Saturday mornings, it's probably clean enough to play in any room I'm working... but these days it's hard to tell. It seems as though actual racism and actual sex and actual violence are everywhere, but any joke at all- about any of that -made anywhere- is now generally considered to be in very poor taste.
Is this what they call "progress"?

** Remember when Josh B- would say to Josh S- something like, "Blah blah blah...nominally 3.7 volts per cell. So what kind of power can we expect out of a three cell battery?' and Josh S- would reply, "Well... three times three-point-seven is..." and then look up into his eyebrows for a second before saying, "...is math."

Ahhh. Good times. Those were the days, my friend...
 

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#14
Friends,
My apologies for the extended interval between updates. It took longer than I had hoped to gnaw my way through the leather straps and then tunnel under the wall. It's actually quite a funny story, but a long one. Perhaps another time...*

MOTOR MOUNT

Now this next bit may seem intimidating to some, because it involves working with sheet metal (aluminum** in this case). Measure. Mark. Cut. Shape and finish. It's all the same, no matter the material. If you can work with foamboard, you can work with any sheet-good. Trust me.

"But they just aren't the same. They're different!"


I found the piece I'm working with in a scrap bin, but it looks to be about 16 ga. (1.5mm thick). It'll bend back-and-forth a fair few times before snapping in two, so it's probably 6000 series, but I would expect any piece of aluminum you can lay a hand on that you think would work for this, probably would. Start in a square corner and mark your cuts, bends, and holes.

Scrap.jpg


Scribe.jpg

Take some pointy-ended thing and make a little dent in the center of each hole location ( a smarty-pants might mumble something about a center-punch right about now). I've used a nail, a drywall screw, even a center-punch, but here I'm using a mechanic's pick I've re purposed as a scribe.

Punch.jpg

Drill out these holes. 5/32 drill bit is probably the right size, but eyeball the bit against the screw, and you can't go wrong. Oh, and fight the temptation to cut the piece out before drilling. Trust me. Your clamps will thank you.

Drill.jpg
(BTW: If you run the drill through the holes from both sides of the sheet it automatically de-burrs the hole.)

With the holes all drilled, make your cut. Tin-snips would work great for this, but any saw that will cut wood can cut aluminum. Just go slow, and put on some glasses.

Cut.jpg

From there, finish the edges with a file, emery cloth, sandpaper, whatever you got. (Used all three on this one.)

Shaped.jpg

That goes into a vise (or a c-clamp, or a pair of vise-grips...) and whackity-wack! gets coaxed into an L- bend.

In vise.jpg


Get bent.jpg

Firewall.jpg

...and what you get is what you see. What? Ohh... Popsicle sticks!

popsicle sticks.jpg

Glue two together; mark center, and the mounting holes. I have tons of those little wood screws that come with servos laying around, so I'll be using those. (As my lawyer would say) In an over-abundance of caution and due diligence, I'm also going to glue these parts together as well. I don't know if the epoxy is really necessary but I use it just the same, out of respect for my old friend, Justin.***

This is glue strong stuff.jpg

Glue up.jpg

Come together.jpg

Let that kick. When it's cured enough to keep working, I reach for my not-an-actual Dremel tool, and cut the pointy-ends of the screws flush with the popsicle sticks.

pointless.jpg

Knock. Knock.
Who's there?
Broken pencil.
Broken pencil-who?
Ohh... Forget it. It's pointless...

I'll be running a three inch prop. I want the weight of the motor as far forward as I can manage and still allow room for the prop to... swing. I worked out where that would be, and marked the motor mount location. Score-cut and gouge that out with a skewer, and we're ready to glue in our motor mount.

layout.jpg pockets.jpg

As it happens, the screws that come with this particular motor (i-Flight Bee Motor 1108 5000kv) are way too long to use without some kind of spacer. I've heard enough squawk from the multi-rotor community about the benefits of soft-mounting your motors to be reasonably confident that it doesn't hurt anything, so I say, "Why not?"

I had some rubber door-gasket material laying around from my feeble and futile attempts to keep Old Man Winter out of my house, so I again say, "Why not?"

Foam.jpg Gasket.jpg

I put a little bubble-gum on that, to keep it from going anywhere until the motor clamps it down.

Gasket installed.jpg

Screw the motor to the mount, and glue the whole dingus into the airframe. Here I do use hot-glue. It's plenty strong for any normal flight stresses on this joint, but compared to the epoxy it's the weakest link in the chain, and for good reason. If I do come down hard enough for something to break, this is where I want things to come loose. Let the whole motor mount part ways with the airframe, taking all its kinetic energy with it, I say.

pockets full.jpg

Not much left now. Receiver, ESC, battery, BOOM!

...to be continued.



Notes:
* Only joking. I've just been catching up on Honey-Do's, but isn't the first version soooo much more fun?

** Or aluminium, if you prefer your english in English.

*** Justin Case. You've probably met him before.
 

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