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People in the model airplane world have been building precisely these kinds of planes for probably at least two decades. In that sense, nothing new. That said

People in the model airplane world have been building precisely these kinds of planes for probably at least two decades. In that sense, nothing new. That said, good to see the idea reaching a different audience. If you want to save some weight you can buy small diameter carbon fiber rods for the pushrods (rather than using steel). You can also stiffen the wing by using a carbon fiber spar (either epoxy or cyanoacrylate to the bottom surface. If you know what you are doing you can even lighten it by cutting holes in the wings (think: punching out a bunch of circles) and then use packing tape to cover top and bottom surfaces. That said, a light plane isn't always better. Some of my best-flying RC planes are not what anyone would characterize as light. For example, an electric-powered glider that weighs eight pounds (3.6 kg), can go straight up like a rocket, glide (power off) at over 120 mph and thermal with the birds with great agility and control. The problem with very light RC planes is that they can be very difficult to fly in windy conditions, this is particularly true of inexperienced pilots. Here are some examples (no affiliation): https://www.wmparkflyers.com/EPP-Foam-Airplanes https://www.wmparkflyers.com/EPP-Foam-Airplanes

kayodelycaon 4y ago
My grandfather built model planes out of balsa wood kits for at least two decades. Some of them had wingspans of 5 feet. :)
- ncmncm 4y ago
  It has become so, so much easier now.
nine_k 4y ago
The point here appears to be very inexpensive and requiring very little skill to build. Basically only the electric equipment and the aileron hooks are not made from common cheap household items or flat TV packaging trash. Certainly you can improve this design in many ways, while making it lighter, sturdier, and higher-performing at the same time. It would take quite a bit of skill, more tools, and a variety of more interesting materials.
- bri3d 4y ago
  "Flite Test" have been designing ridiculously cheap, low-skill DIY flying things for many years now - at the same level of "turning trash to an RC plane." Definitely worth checking out if you're interested in the space.
  - ansible 4y ago
    Agreed about Flite Test. They have kits using water resistant foam board that will perform and look better. Also this delta wing has options like being able to purchase the motor kit needed: https://store.flitetest.com/ft-spear-wing-wr-1041mm/ https://store.flitetest.com/ft-spear-wing-wr-1041mm/ It is a good way to get started.
- paulmd 4y ago
  Sure, that's why people have been doing this design for 20 years. Homebuilding included ;) I agree with the grandparent, it's of course interesting and it's a different audience, a lot of the "drone" crowd nowadays is purely quadrocopters, but like, this was pretty standard stuff back 15 years or so ago, for the electric parkflyer crowd. But much like every piece of software nowadays is an "app"... every model airplane is a "drone" now, and drone people aren't really familiar with the variety of aircraft that are possible because of the dominance of the quadrocopter. Like yeah, welcome to what the rest of the hobby has been doing while the drone community has farted around with quads for 15 years ;)
stuven 4y ago
Thanks for sharing your knowledge!
paulmd 4y ago
> You can also stiffen the wing by using a carbon fiber spar this isn't really optional imo, this is a "should" and it should be at least one continuous spar going across the majority of the wing (don't put two ending in the middle, that's missing the point here). If you want, you can even do two - a shorter one in front and a longer one in back, or do a triangle-shape to strengthen the wingtips. This is because EPP/EPS doesn't have enough structural strength on its own and with brushless motors you can definitely go fast enough to cause the wing to "flap", and that will result in the elevons flexing in the opposite direction (as the servo pushrod is attached to the wing) causing a "vertical fishtailing" effect in midair. https://www.rcgroups.com/forums/showthread.php?1500999-The-dreaded-Zagi-flap https://www.rcgroups.com/forums/showthread.php?1500999-The-d... https://www.youtube.com/watch?v=yYfT0tQm668 https://www.youtube.com/watch?v=yYfT0tQm668 (you can see this design is problematic because of the high sweep of the wings... there is frequently a little bit of wingtip that you can't reinforce, but, most of that wing is just hanging in midair, and those types are VERY prone to flapping.) You can dremel out a spar channel and put the spar in that. The filler material of choice back in the day was Elmers' ProBond Polyurethene glue - mix it with some water and it'll foam up like crazy and you just pour it into the channel and wipe off any excess as it dries. Not to be confused with Elmers' ProBond wood glue though - that won't foam like that. https://www.homedepot.com/p/Elmer-s-ProBond-4-oz-Advanced-Multi-Purpose-Glue-E7502/203619359 https://www.homedepot.com/p/Elmer-s-ProBond-4-oz-Advanced-Mu... Also don't use EPS. EPP is far far more durable. And DO use a shrink-down covering like monokote or ultracote - the shrink-down covering will provide additional rigidity in addition to the spar. I tried using packing tape at one point instead, and it was definitely noticeably less rigid than ultracote and I ending up removing and replacing it. https://www.horizonhobby.com/airplanes/supplies-and-bench-accessories/covering-supplies/ https://www.horizonhobby.com/airplanes/supplies-and-bench-ac... As a practical matter, I highly recommend contrasting color schemes - like red on bottom, blue with a wide reflective stripe on top, or something like that. Because from the ground it's super easy to lose perspective if you can't distinguish which side is up.
- robomartin 4y ago
  I have used carbon fiber tape in place of rods to good effect. I agree that a proper spar is critical for handling the loads. To be more precise, you need to deal with shear and torsional loads. These super-light cheap planes will easily turn into a taco in flight without care given to forces that will crush the foam. Even a layer of packing tape on top and bottom surfaces is better than just foamboard. I've had a couple of these planes over the years. I don't really enjoy them. I'm into high performance gliders (e-powered), ducted fan jets or helicopters.

kayodelycaon 4y ago

My grandfather built model planes out of balsa wood kits for at least two decades. Some of them had wingspans of 5 feet. :)

ncmncm 4y ago
It has become so, so much easier now.

nine_k 4y ago

The point here appears to be very inexpensive and requiring very little skill to build. Basically only the electric equipment and the aileron hooks are not made from common cheap household items or flat TV packaging trash. Certainly you can improve this design in many ways, while making it lighter, sturdier, and higher-performing at the same time. It would take quite a bit of skill, more tools, and a variety of more interesting materials.

bri3d 4y ago
"Flite Test" have been designing ridiculously cheap, low-skill DIY flying things for many years now - at the same level of "turning trash to an RC plane." Definitely worth checking out if you're interested in the space.
- ansible 4y ago
  Agreed about Flite Test. They have kits using water resistant foam board that will perform and look better. Also this delta wing has options like being able to purchase the motor kit needed: https://store.flitetest.com/ft-spear-wing-wr-1041mm/ https://store.flitetest.com/ft-spear-wing-wr-1041mm/ It is a good way to get started.
paulmd 4y ago
Sure, that's why people have been doing this design for 20 years. Homebuilding included ;) I agree with the grandparent, it's of course interesting and it's a different audience, a lot of the "drone" crowd nowadays is purely quadrocopters, but like, this was pretty standard stuff back 15 years or so ago, for the electric parkflyer crowd. But much like every piece of software nowadays is an "app"... every model airplane is a "drone" now, and drone people aren't really familiar with the variety of aircraft that are possible because of the dominance of the quadrocopter. Like yeah, welcome to what the rest of the hobby has been doing while the drone community has farted around with quads for 15 years ;)

stuven 4y ago

Thanks for sharing your knowledge!

paulmd 4y ago

> You can also stiffen the wing by using a carbon fiber spar this isn't really optional imo, this is a "should" and it should be at least one continuous spar going across the majority of the wing (don't put two ending in the middle, that's missing the point here). If you want, you can even do two - a shorter one in front and a longer one in back, or do a triangle-shape to strengthen the wingtips. This is because EPP/EPS doesn't have enough structural strength on its own and with brushless motors you can definitely go fast enough to cause the wing to "flap", and that will result in the elevons flexing in the opposite direction (as the servo pushrod is attached to the wing) causing a "vertical fishtailing" effect in midair. https://www.rcgroups.com/forums/showthread.php?1500999-The-dreaded-Zagi-flap https://www.rcgroups.com/forums/showthread.php?1500999-The-d... https://www.youtube.com/watch?v=yYfT0tQm668 https://www.youtube.com/watch?v=yYfT0tQm668 (you can see this design is problematic because of the high sweep of the wings... there is frequently a little bit of wingtip that you can't reinforce, but, most of that wing is just hanging in midair, and those types are VERY prone to flapping.) You can dremel out a spar channel and put the spar in that. The filler material of choice back in the day was Elmers' ProBond Polyurethene glue - mix it with some water and it'll foam up like crazy and you just pour it into the channel and wipe off any excess as it dries. Not to be confused with Elmers' ProBond wood glue though - that won't foam like that. https://www.homedepot.com/p/Elmer-s-ProBond-4-oz-Advanced-Multi-Purpose-Glue-E7502/203619359 https://www.homedepot.com/p/Elmer-s-ProBond-4-oz-Advanced-Mu... Also don't use EPS. EPP is far far more durable. And DO use a shrink-down covering like monokote or ultracote - the shrink-down covering will provide additional rigidity in addition to the spar. I tried using packing tape at one point instead, and it was definitely noticeably less rigid than ultracote and I ending up removing and replacing it. https://www.horizonhobby.com/airplanes/supplies-and-bench-accessories/covering-supplies/ https://www.horizonhobby.com/airplanes/supplies-and-bench-ac... As a practical matter, I highly recommend contrasting color schemes - like red on bottom, blue with a wide reflective stripe on top, or something like that. Because from the ground it's super easy to lose perspective if you can't distinguish which side is up.

robomartin 4y ago
I have used carbon fiber tape in place of rods to good effect. I agree that a proper spar is critical for handling the loads. To be more precise, you need to deal with shear and torsional loads. These super-light cheap planes will easily turn into a taco in flight without care given to forces that will crush the foam. Even a layer of packing tape on top and bottom surfaces is better than just foamboard. I've had a couple of these planes over the years. I don't really enjoy them. I'm into high performance gliders (e-powered), ducted fan jets or helicopters.