Scales for a flying glider fleet

[Yeti]

Hi Reynolds,

I've previously built and flown, with varying degrees of success, an F-102, F6F, P-40,
F-14(in my avatar), SB2U, P-51, and SB2C. Here are a couple of things I've learned
that might interest you.

* You can avoid extra weight by using super glue to join segmented parts, and thus build
rigidity into the model without internal spars.

*Things like antennas, pitot tubes, gunsights, and other details tend to snag on plants,
even grass. Thus you may want to either not include those details, or to make them
detachable, so that they are there for static display and then removed for flight.

*Consider making some of your control surfaces, especially elevators/elevons,
bendable/trimmable.

*You can make detachable nose cones and cowlings and thereby adjust your CG by
adding, removing, or shifting internal ballast.

*Wind can help you out with heavier models. Mbauer used to, or possibly still has,
a video of a huge F-104 he built gliding down a hillside due the uplift of the wind hitting
the hill.

*In my opinion, a hook or notch for rubber band catapult launching is quite useful as
some designs might not be ergonomic for hand launching. Having said that, some people
such as in the videos below, seem to have no problem hand launching.

Finally, here are a few channels of guys who I would consider to be some of the
best at paper scale flying models.

Peters Aircraft Factory - YouTube

イデユウキ - YouTube

masterpaperaircrafts - YouTube

ZDE Designs - YouTube

Anyway, I look forward to following your thread!

[ReynoldsSlumber]

Thanks for the pointers, Yeti! Some inspirational video channels there. Also really well done on your models! I might follow your lead on the F-14.

Planes I've made in the run-up to this project, with some pics attached:

• PaperAircrafts.com 1/80 JAS39: Faceted; reliably excellent glides.
• PaperAircrafts.com 1/72 F-117: The perfect faceted model subject! Awkward to hold for tossing, but glides great on a lucky one.
• Ojimak 1/80 F7F: Neat design, though the partially faceted fuselage doesn't capture that svelte oval F7F look. Seems that the nacelles are pretty draggy, since in the middle of the glide the glideslope steepens. I don't think it's stalling, because elevator changes don't help. It's a good lesson for future engine nacelles to try to reduce flow separation, maybe by curling over the leading edge of the paper, certainly by making the seams between sections less sharp. My model needed extra nose weight, so I took the opportunity to add pieces of a paperclip as machine guns.
• Ojimak 1/230 Concorde: A nice glider, especially after I had some fun shaping the wings to be like the real wing's contours (which were made that way for low-speed handling, after all!). Got a lesson in the need for nose reinforcement when, on too good of a glide that hit the far wall, the nose collapsed telescopically. Will be nice to build a little bigger, likely using other plans, and add details like engine nozzles.
• Scissors & Planes 737-300 (static): Hopefully will upscale OK, with mods: nacelle pylons that go over the wing leading edge, hollow engines, and no-thickness wings that carry through the fuselage. Getting the wing root fairing right will be tricky. Will look to bigger papercraft 737 plans for guidance.
• ZDE Designs Pterosaur X: An excellent park flier when you get the elevation and bank just right on launch. The designer isn't afraid to build sturdy and fly faster. It's a neat trick that he added a canard wing for pitch stability. I have in mind next making a fully scale pterosaur with some forward wing sweep (without a canard) to get the balance right.

Good point on building hollow. It turns out I'm strictly sticking to healthy materials; even glue sticks are out. So I've been using PVA glue like Aleene's Tacky Glue. It's still a bit too watery though. Between that and inkjet printing on 25 lb. bond paper to keep the model thin and light, you can see how on the F-117 the spars and formers show, the paper warps, and there are a few smudge marks. Might have to switch to laser printing, thicker paper, and/or a thicker glue. Or go even thinner for the surface paper and add more internal structure? Like regressing to 1910s-1920s aircraft tech, haha. Probably too much work compared to building to available plans. While I've got CAD experience, I don't know that I've got the kind of time to learn how to do my own papercraft designs yet.

Good point also on the detachable nose. On the F7F I tried to cut through the nosewheel door area when adding the paperclip pieces for nose weight, and still the underside ended up rumpled by the time I closed it back up.

Yes, definitely not going to include pitot tubes etc. My interest is more in getting the major shapes right and including the bigger, more distinctive details like flap fairings etc.

Funny extra thing: I got a net to hang in front of the far wall when I'm flying. Helps avoid the irony of even a good flight ending in a crash!

[Yeti]

Ah, you've got some experience with this. Nice little collection of flying models you have there! You mentioned curling over the leading edge of the paper. I noticed on some of PaperAircrafts' birds that he does that and it's like a leading edge slat. Combined with a little down flaps, like on his Mirage 2000, and it's like a cambered wing.

I like your idea about flying them into a net. Good stuff!

[ReynoldsSlumber]

Thanks Yeti! The first time I ran across a leading edge treatment like that was in an old Peter Vollheim paper airplane book. His book The Paper Ace includes the best development of a traditional paper airplane that I've found (see photo)—it flies slow, straight, and flat.

For the F7F I used Whitewings-style airfoil shaping: the top and bottom layers of paper stuck together and bent into a simple shallow arc. Another option could be a thin cambered airfoil with a tight leading edge radius and then the top and bottom layers coming together midway through the chord. I saw that recommended somewhere online and now can't find it... If I can control an almost-crease to be round on the leading edge, it would be nice for how it looks from above (as opposed to just a cut two-layer edge), and it could reduce the chance of stall as well as increase wing strength.

[mbauer]

Originally Posted by papermate

Thanks for sharing this very interesting subject, Mike.
A dumb question- how to read your cg locator diagram? Is there just one wing there?

Yes, just one side is all that is needed. That is why I put a CG mark on the fuselage instead of the wings. Easier to hang from a center point, string taped to a door opening for instance to allow the model to swing freely.

Instead of an Airfoil shape wing, are you are using a Flat Plate design wing? the thickness will be the same: measure 1/3 the chord (width of the wing) from the leading edge and use this for the wing root and wing tip locations to find the CG of your model.

For instance your wing is 24" long and the width is 9". You would measure 3" from the leading edge of the wing, as the place to mark the wingtip and wing root. Now you can use the drawing to finish finding the CG location.

Does this help?

Mike

[mbauer]

Originally Posted by ReynoldsSlumber

Thanks for the pointers, Yeti! Some inspirational video channels there. Also really well done on your models! I might follow your lead on the F-14.

Planes I've made in the run-up to this project, with some pics attached:

• PaperAircrafts.com 1/80 JAS39: Faceted; reliably excellent glides.
• PaperAircrafts.com 1/72 F-117: The perfect faceted model subject! Awkward to hold for tossing, but glides great on a lucky one.
• Ojimak 1/80 F7F: Neat design, though the partially faceted fuselage doesn't capture that svelte oval F7F look. Seems that the nacelles are pretty draggy, since in the middle of the glide the glideslope steepens. I don't think it's stalling, because elevator changes don't help. It's a good lesson for future engine nacelles to try to reduce flow separation, maybe by curling over the leading edge of the paper, certainly by making the seams between sections less sharp. My model needed extra nose weight, so I took the opportunity to add pieces of a paperclip as machine guns.
• Ojimak 1/230 Concorde: A nice glider, especially after I had some fun shaping the wings to be like the real wing's contours (which were made that way for low-speed handling, after all!). Got a lesson in the need for nose reinforcement when, on too good of a glide that hit the far wall, the nose collapsed telescopically. Will be nice to build a little bigger, likely using other plans, and add details like engine nozzles.
• Scissors & Planes 737-300 (static): Hopefully will upscale OK, with mods: nacelle pylons that go over the wing leading edge, hollow engines, and no-thickness wings that carry through the fuselage. Getting the wing root fairing right will be tricky. Will look to bigger papercraft 737 plans for guidance.
• ZDE Designs Pterosaur X: An excellent park flier when you get the elevation and bank just right on launch. The designer isn't afraid to build sturdy and fly faster. It's a neat trick that he added a canard wing for pitch stability. I have in mind next making a fully scale pterosaur with some forward wing sweep (without a canard) to get the balance right.

Good point on building hollow. It turns out I'm strictly sticking to healthy materials; even glue sticks are out. So I've been using PVA glue like Aleene's Tacky Glue. It's still a bit too watery though. Between that and inkjet printing on 25 lb. bond paper to keep the model thin and light, you can see how on the F-117 the spars and formers show, the paper warps, and there are a few smudge marks. Might have to switch to laser printing, thicker paper, and/or a thicker glue. Or go even thinner for the surface paper and add more internal structure? Like regressing to 1910s-1920s aircraft tech, haha. Probably too much work compared to building to available plans. While I've got CAD experience, I don't know that I've got the kind of time to learn how to do my own papercraft designs yet.

Good point also on the detachable nose. On the F7F I tried to cut through the nosewheel door area when adding the paperclip pieces for nose weight, and still the underside ended up rumpled by the time I closed it back up.

Yes, definitely not going to include pitot tubes etc. My interest is more in getting the major shapes right and including the bigger, more distinctive details like flap fairings etc.

Funny extra thing: I got a net to hang in front of the far wall when I'm flying. Helps avoid the irony of even a good flight ending in a crash!

Very beautiful builds!

Mike

[papermate]

Thanks, Mike, for your explanation. Para 3 helps especially.

[ReynoldsSlumber]

First up in this series: A-4E Skyhawk, since it's not too-too complicated of a shape, and since its small size will test my choice of scale for fighters/general aviation planes. It's a Scissors and Planes plan of my favorite A-4 version aesthetically: one with the smaller engine, boundary layer splitters on the intakes, and the "dromedary" avionics hump.

I started off seeing if I could make it in 1/87 but didn't like the small size nor the Titebond Quick & Thick glue I was trying. So I tossed that and started over using 1/72 and Aleene's Super Thick Tacky Glue. The glue, same as regular Tacky Glue but with less water, is perfect for the fuselage joints, but it still causes warping when I put wing layers together, even when I use an artist's silicone spatula to squeegee the glue thickness down to a minimum. This is super frustrating. :( On a future model I think I'll try methyl cellulose adhesive, a recommendation by ricleite. Has anyone tried the new Klucel G glue from Lineco, using alcohol as the solvent rather than water? And, think inkjet printing would hold up to that?

Speaking of printing, the plans are inkjet printed on:

• 65# cover (medium weight) for the fuselage, wing bottom, and one surface of the tail pieces, for a compromise between stiffness and lightness
• 65#/96g sketch (lighter weight) for the other halves of the flying surfaces and for the detail pieces, a compromise between lightness and withstanding glue
• 100#/270g Bristol (heavy weight) for the added internal spine, for structure and to contribute to nose weight

Modifications so far:

• Added the aforementioned spine to prevent the conical nose from caving in in inevitable crashes. Bruno's bonus side plan view worked nicely for this. I used blue tape (stuck to a shirt first to reduce tack and avoid surface damage) to hold the nose in place while gluing the spine into the main body, to get the fit right. I'll glue the nose on at the end, after initial test flights for adjusting how much nose weight to add.
  
• Omitted the internal tailpipe and flat bulkhead piece, since it would be tail weight... and to perhaps reduce drag: I might make passage holes through which the air going in the intakes can reach the tail exit. I darkened the inside surface of the nozzle with pencil.
• Looking ahead to trying to make the rear portion of the wing undercambered, since a thick-ish wing with a flat bottom ain't the greatest airfoil for an indoor glider. This is going to be tricky due to the low-mounted wing as well as pylon attachment. (I'll be adding pylons "for character," but not any stores on them). At least I don't have to carry the wing through a root fairing on this one. Think I'll stick the top and bottom layers of the wing together for the flaps/ailerons portion while leaving some wing thickness volume open in the front portion of the wing. Ideally the top would be a continuous arc while the bottom would be an S-shaped profile, but we'll see.
• Added a 0.0035" thick clear plastic finger hold to the wing underside, with tabs scored for folding and scuffed and perforated for gluing. Rather pleased with this bit. Later the root portion of the finger hold will be further disguised by paper representing the center pylon.
  
• Cut out the individual rudder ribs, since they're such a distinctive part of the A-4, and colored them. The ink bled in from the edges, so I just colored the ribs entirely. They're glued to an added solid rudder central piece.
• Cut the horizontal stabilizer roots straight for a flat rather than airfoiled vertical stab, plus carried a tab from one side of the horizontal stab through a slit in the vertical stab and sandwiched the tab in the layers of the other side. I guessed the incidence at a couple degrees more than the plan. Then I added little glue fillets to the undersides of the roots. (I didn't quite manage to make the trailing edge of the horizontal stab straight, so it goes!)
  

[Yeti]

Thanks for sharing your progress report with us. She's looking real good!

[ReynoldsSlumber]

Thanks Yeti!

Continued modifications:

• Made the external tailpipe into a slightly larger arc and colored in the excess. The plans have the tailpipe undersized, but on the early A-4s the tailpipe circumference was flush to the fuselage surface, so I made it closer to that.
• On the engine air intakes, tried an origami trick: leave a few mm of extra paper in front of the lip, score along the lip (on the inside surface), then form the intake main shape, then turn the extra paper inside out along the score. It worked, but the paper was too thin for the crease to give any visual indication of a rounded intake leading edge. Maybe one of y'all working on a static model using cover paper or thin cardstock would want to give it a try.
  
• On the intake air splitters, it would've been nice to add tabs to the ends of them, so that they'd be less fiddly to attach to the air intake edges, ah well. I did add bits of paper to space the splitters off the fuselage (not shown), as on the real thing.
• Cut a circular hole on each side of the center body for intake air to pass through to the tailpipe, for a little less drag hopefully. I shaped each hole into a scoop.