FT-DLG - The $12 Discuss Glider


Pretty straightforward concept: Design and build a super-low-budget DLG

Approximate major material costs (not including electronics or basic hardware): ~$12
2 sheets, DollarTree foam board: $2
40" CF tube spar: $10
CF arrow shaft: Free (used, from scrap bin at archery shop)

I recently put together my first FliteTest design - the FT Racer - and was struck by how simple and STRONG the folded-wing construction method was. I thought "this would be perfect for a budget-DLG wing".

So I drew up a simple tapered wing using the same basic folding and hot-gluing method most of the FliteTest designs use, so it's real simple and easy to throw together. It's only 40" span because I wanted to use a carbon-fiber tube-spar and all I had on hand was a 40" CF tube. I also had the notion that a 40" CF tube is fairly representative of what most people could get from their local hobby shop (I think?), and thought that was in keeping with the FliteTest theme of this project.

The full span spar makes the wing extremely strong and rigid, able to stand up easily to even the most abusive throws. The only carbon in the plane is the 40" CF tube and an arrow shaft from my local archery place for the fuse stick.

I don't expect it to perform exceptionally well as a DLG-proper, because it came out a tad heavy (par for the course), but I'll still throw it for practice. I DO expect it to be a good medium to high wind sloper. And the way I've designed the removable wing, it should be almost trivial to make a larger floater-wing.

At first I built it with rudder, and misjudged the servo-placement in the nose pod. If you look close at the assembled pics there's a little unplanned bump on the bottom of the nose. I had to poke one of the servos out the bottom so I could fit two close enough to fit but not interfere. I've since ditched the rudder altogether, I wasn't really using it anyway, and switched the elevator from steel-pushrod to pull-string-spring. These changes really helped to lighten the tail and get the balance forward.

To make the wing removable, I designed a blade-style sliding fit with two locking pins. I reinforced the pin holes with a 5mm CF tube, and use a smaller CF tube as the lock rods. It took some elbow grease and adjustment on the first assembly, but it holds real nice. After several strong DLG throws, the joint is still holding up nicely. Plus it packs away nice and neat in the trunk. ;)

For a throwing peg, I used a little piece of CF blade on the wingtip, epoxied with CF tow into the wing spar. That way all the loads go straight into the strong spar and not into the foam.

As a follow-up, I plan on building a second wing with a simple foamboard spar instead of a CF tube. This should save considerable weight, and shouldn't sacrifice too much strength. It also would be nice to have a little dihedral, but we'll cross that bridge later. :)

The AUW came in just over 11 ounces, and with a final wing area of 230sq-in the wing loading is around 7oz/sq-ft. Certainly heavy for a real DLG, but not bad overall.

Maiden slope flight at Bluff Park! Wind was a little light, but I was able to get some time in the air, and a few clips as it flew past my camera (didn't have my hat, had to tape it to the railing). ;)

Finally got some good discuss-launching video at Fairview Park:

Not a high-performance DLG, but with a little flaps dialed in for camber it actually flies quite nicely!

She flew great in both scenarios. I was scraping by a bit on the slope, thanks to the heavier wing loading (slope flight was prior to tail-lightening changes); If the wind was a little stronger and consistent I think it would've been awesome!

I honestly was pleasantly surprised at how it performed as a DLG at the park. I wasn't able to stay up for more than 30 seconds at a time, but for an inexperienced DLG-pilot and a relatively heavy plane I think she performed admirably!

Very stable, no serious tip stalls; all in all a pretty nice plane. I'm a happy designer. :)


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EEEK! you used that soggy black foam board! Its supposed to be super soft and weak..

It is, I know from experience.:(

Still, I love the plane!

I haven't noticed a big difference between the black and white DT foamboard, I actually made an entire FT-Racer out of the black and it worked just fine.

I did just nose-in my DLG this morning and it cracked one of the bulkheads, but I think it would've cracked just the same even in white-backed foam. I'm all out of black, so I'll repair it with white, but I don't plan on purposely nose-crash-testing it just to see. ;)

Will you be posting the plans? It looks great!

I certainly can, I just need to actually draw some! :) Actually, I need to take some more pics since improving the vertical tail.

I'm also working on a v.2 wing that has a bit more span, area and dihedral, without a CF tube spar in hopes of getting better floating performance. With the wing-saddle design I have, it should be really easy to have a swappable wing for different conditions.



Well, that actually went quicker than I expected. :)

Attached are plans for all the foamboard parts. If you've built any of the FT designs, you'll be off and running. For clarification though, on these plans:

Black = Cut
Blue =Crease/Bend
Red = Score & reverse fold-over OR Scored Hingeline
Green = Reference/centerline

NOTE: You do NOT have to make the wing swappable/removable. I did NOT mark the joint-holes on the plans because their location is somewhat dependent on the diameter of your fuse-stick.

If you don't care about removing or swapping the wing, simply make the saddle and blade pieces like normal, and then glue/tape the wing in place.

I also didn't mark any servo locations, since this also depends on what kind of servos you're using. I'm just using the metal-gear version of Hobbyking's HXT900's. They could be lighter, but they do the trick. :)

Beyond these parts you'll need the following (or similar):

Fuselage: 1x 32in carbon fiber arrow shaft or other CF hollow tube
Wing: 1x 40in, 5mm-dia carbon fiber tube spar
Wing Join: Short sections of CF tube for reinforcement and locking (for swappable wing)
Launch Tab: Short section of 1.5mm x 5mm carbon blade or similar

Hopefully this should get y'all going quick enough! Please feel free to ask questions about any blanks I left out. ;)

I realize a dimensioned 3-view would really help to know where all the parts and pieces go, but I haven't gotten to that yet. The 3D-model pics in the original post should help give you an idea of where everything goes. Sorry you might have to do a bit of tinkering on this! :)

Also please share your build progress and results if you do actually attempt this for yourself!


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Driftin' with the wind...
I have also built several foamboard DLGs of my own design. mine last for 1-2 days:) No I don't go gently with them, I fly them hard! My last one went into a small tree at around 50 feet per second right after I threw it, oops. but it was spectacular! it went in one side in one piece and came out the other in several. and I had a good laugh about it.
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This one has held up really well so far, probably thanks to the CF tube spar in the wing, and I covered the wing with a single layer of clear packing tape for strength and sealing.

I DID nose it in pretty hard the other day, but the only damage was a busted bulkhead in the nose-pod. I actually didn't even notice anything was broken right away. Then I saw the nose wiggle more than usual, that's when I knew something was up. :)

It's fixed now, a few grams heavier thanks to some reinforcing. I could lose some weight by re-making the nose pod cleaner.

I also just added a removable winch hook under the wing; I'm going to experiment with a winch launch tomorrow morning. I'll let you know how it goes! :)


Had a little leftover DTFB and another arrow-shaft, so I wanted to try and make another glider with a different wing and balsa tails. Didn't have enough for a folded-up wing like before, but just enough for a single-layer with cut leading and trailing edges. I've used this method before with great success on a micro 24" and 30" span DLG, but this would be 40" span.

I was able to keep it just a little over 5oz, so the wing loading was really nice and light; only about 4 oz/sq-ft.

Hand-toss test flight was a success, it floated very nicely! But the first sidearm/discuss throw kinda kinked the wing near the root, which I honestly kinda expected. I didn't reinforce the wing at all, except for some clear packing tape to keep the moisture out and make it shiny. ;)

So I went back and cut a slot for a CF blade spar, which was just barely the same height as the foamboard was thick, so it fit just right. I also added a small piece across the root to shore-up the root-bending, which is the highest load.

This added about 0.4oz, which I was pretty happy with. It possibly could've been lighter, but it's not bad considering my hot-glue construction methods. :)

With the newly reinforced wing I'm able to discuss launch it with moderate force and the wing is solid. Even with only a medium-force throw though, thanks to the thin wing and tails, it launches to about the same height as the first one with a killer-hard throw, and it floats a lot better.

I still plan on getting some more DTFB and making a larger folded-up wing, but this just shows you what you can do with a single-layer of foamboard. :D

My dad met me at the field this morning before work and got some nice video of the newly-reinforced wing!

I tossed it pretty gingerly at first, just 'cuz I didn't know what the wing could handle. But after a few ramp-up throws it seemed to be holding together really well, so I think I could throw it quite a bit harder. A proper throwing peg would certainly help, reinforcement would be tricky, but I'm looking into it. :)

Forgive his occasional narration, he's good at expository questions. ;)


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