Contest to build the cheapest DLG

[rcspaceflight]

Would REALLY love plans for your most successful DLG with DTFB - I built one as well using the Axon wing and I'm over 450g - still flies but not for near as long as yours.

450grams?!? I've build planes with a 2200mah 3S battery on it that weighed less than that.

The biggest enemy with a DTFB DLG is the weight. More weight = more force on the DTFB. More force = more likely to break. More likely to break = more bracing/supports = more weight. It's better to just go as light as possible so you don't need any sort of bracing or supports (like packing tape or carbon fiber).

 

[ztoon]

Hi everybody,
This is not really a dlg, but just to let you know that a half scale alula works well with depron. That one was a fat at about 40gr, so without the 2 motors and a little battery, it is really possible to keep it really light.
The servos and receivers cames from a dead wltoys v911 chopper all-in-one-board (10$ on bangood.com or others).
If you have a 9X Tx, it is a direct bind, if not... well it is flysky protocol.

 

[Christopher14]

Oh, cool! My first dlg's setup was v911 board as well.

 

[ztoon]

Oh, cool! My first dlg's setup was v911 board as well.

Hi Christopher,

Is it a flying wing or more conventionnal dlg?
Could you share some pics?
I've a 1 meter composite DLG and now a 1.5m Versus, but I really like to see a cheap one to show beguinners how it is nice to fly.
For 10$, the v911 pcb price is difficult to beat.

 

[Christopher14]

Hi Christopher,

Is it a flying wing or more conventionnal dlg?
Could you share some pics?
I've a 1 meter composite DLG and now a 1.5m Versus, but I really like to see a cheap one to show beguinners how it is nice to fly.
For 10$, the v911 pcb price is difficult to beat.

My DTFB DLG looked like the mini composite DLG from HK.
I don't have any pictures. But I might build one in the future.

The only problem is my DLG does not float like the a normal one, it flies fast and it sinks fast. Although I can launch it to about 70-100ft, the flight time is around 15-20 seconds. Not the best.

 

[ztoon]

The only problem is my DLG does not float like the a normal one, it flies fast and it sinks fast. Although I can launch it to about 70-100ft, the flight time is around 15-20 seconds. Not the best.

I made some morning flights with my one meter dlg.
Average flight time in zero air was less than 40sec. That's how I found out that my afternoon flights were not so bad after all
So I'll be happy with a 20sec / cheap dlg myself.
Lets say I'll will be very happy for 30sec/30$

 

[Christopher14]

Would you like a wing plan? I might be able to draw one up in Sketchup.

 

[MarshallX]

450grams?!? I've build planes with a 2200mah 3S battery on it that weighed less than that.

The biggest enemy with a DTFB DLG is the weight. More weight = more force on the DTFB. More force = more likely to break. More likely to break = more bracing/supports = more weight. It's better to just go as light as possible so you don't need any sort of bracing or supports (like packing tape or carbon fiber).

Funny part is I've now built two more that were around 200g and they barely float

Not sure what to do! Both using the plans in the post I linked.

 

[ztoon]

Would you like a wing plan? I might be able to draw one up in Sketchup.

Yes, I like to have a look, but maybe that's a little too much work for now, as you wish.
What about a hand writing paper plan as attachment?

For those who want to start real cheap :
v911 pcb = 10$ (you be surprised how the 2 servos are strong and precise given their size and price)
JR flysky module = 20$
v911/v939 4ch radio = 15$
Now for 35$ you have the full rtf kit (copter, radio, charger and batteries). Some combat session with a friend and you have what's necessary to start a cheap dlg. (no, I'm not paid by bang00d.c0m )
Cheaper? you can go there, but some electronics skills are required...

 

[Mid7night]

Would REALLY love plans for your most successful DLG with DTFB - I built one as well using the Axon wing and I'm over 450g - still flies but not for near as long as yours.

Specifically your wing

I still need to draw up plans for Version-2; the one with the single-layer wing. It had great performance for what it's made of.

There are plans for the folded-wing version (the first, heavier, one) in THIS POST on RCGroups. You might be able to infer the rest from there, as a starting point.

I've been sidetracked with many other creation projects of late, but I still have the boom/tails sitting on a shelf, just waiting for a new wing. I've even got some more foam, I just need to set aside some time to actually make a new wing. When I do get around to it, I'll try and do a better job of chronicling the process for y'all. Thanks for the kind words!

 

[MarshallX]

Here's my second attempt at a DTFB DLG - throws were a bit wonky due to some crazy wind but hey - it's something to mess with. I'm not really sure how much more "floaty" I can get it - nor do I really understand wing dynamics to figure out how to get less speed and more lift.

 

[JohnRambozo]

Marshall,

I can't believe none of us ever replied to this. Great job making a foam dlg. Have you done any more with the design?

 

[rcspaceflight]

I can't believe I still haven't re-attempted a cheap DLG.

 

[rcspaceflight]

I want to try to compile some pointers and lessons I've learned so far.

- Using wire safety flags does work for a solid peg. By keeping it's full length and bending a small peg at the end, you have a lot of contact area to glue the wire to the foam. Over 10" of contact area of wire onto foam makes it very difficult to pull the wire off of the foam with a force from the side. Hot glue doesn't work the best, but Gorilla Glue works very well.

- I haven't tried it, but I'm pretty sure that adding small struts/braces to the wing/fuselage joint will be all that's needed to ensure the wings don't pull off. The struts can be foam board as well as the fuselage and as well as the wings. The wing struts only need to be a couple/few inches long. (I actually did try it, but not on a DLG. I built a plane with small wing struts and I tried to pull off the wings, which didn't happen.)

- Three 2"-3" tall strips of foam board glued/laminated together is all you need for a fuselage. Removing the paper between the glue joints is preferred and Gorilla Glue will result in a stronger fuselage. (But keeping the paper and using hot glue is fine.)

- I believe a 40" wingspan is best. Any longer and it becomes much more difficult to keep the plane strong enough to withstand discuss launching. Any shorter and it becomes much more difficult to keep the wing cube loading small enough to work as a glider.

- As with any good glider, polyhedral or dihedral is mandatory. I probably don't need to point that out, but the reasoning is because a self righting plane will be much more efficient at staying level than human control. To keep a glider in the air as long as possible you need to use as few movements as possible. Control surface inputs equals drag which equals speed loss which equals less time in the air.

- I could be wrong, but I think the best airfoil to use is a KF Step. This results in a very thin wing that penetrates the air the best. Not the most lift, but I believe speed and an absence of drag is more important than lift. A good glider needs a lot of lift, but a DLG needs to keep it's speed up and drag down.

 

[rcspaceflight]

My internet and/or the FT forums are acting weird and double posting.

 

[o0Jack0o]

Does this count?
http://flitetest.com/articles/cheap-simple-foam-dlg-with-good-performance

 

[MarshallX]

Marshall,

I can't believe none of us ever replied to this. Great job making a foam dlg. Have you done any more with the design?

I forgot all about this thread too - I tried a few more designs and got some decent flight times, but nothing that would float on a thermal and nothing that would last too long. The wing to fuselage joint takes a ton of stress in DLG and I can't figure out a way to strengthen it.

I would love to try again, or Josh to try again, DLG is extremely satisfying but the cost of getting into it is astronomical.

 

[AkimboGlueGuns]

Has anyone tried an alula clone yet? If not, I will attempt this winter.

 

[Mid7night]

In reply to the "best airfoil" note; I've had good success with the RM "RustyMustard" section. It's just a short top-bevel on the LE, and a longer under-bevel on the TE, giving you a sort of skewed trapezoid. You can do it with just a single layer of foamboard, which results in a VERY low drag and decent performing wing. Insert a carbon fiber blade-spar and iron on some laminating film if you really want reinforcement, and you've got a darn strong wing, given the materials. I've done this with a 48" span and it worked great.

The really nice thing about the RM section is it's simple and fast to throw ideas together and test with, and it's perfect for cutting out of DTFB.

 

[rcspaceflight]

In reply to the "best airfoil" note; I've had good success with the RM "RustyMustard" section. It's just a short top-bevel on the LE, and a longer under-bevel on the TE, giving you a sort of skewed trapezoid. You can do it with just a single layer of foamboard, which results in a VERY low drag and decent performing wing. Insert a carbon fiber blade-spar and iron on some laminating film if you really want reinforcement, and you've got a darn strong wing, given the materials. I've done this with a 48" span and it worked great.

The really nice thing about the RM section is it's simple and fast to throw ideas together and test with, and it's perfect for cutting out of DTFB.

I've heard of that airfoil, but I've never tried it. It is supposed to be great for a fast slope soarer. It should be perfect for a cheap DLG too.

Another reason why I like the KF step is because it adds some thickness which adds more strength. Hopefully one KF step glued on top of a single layer of foam board will be just enough strength added to the wings. But maybe that's wishful thinking. Plus you could glue the wire for the peg between those two layers. Making the wire for the peg also a wing spar. Not the best wing spar because it's steel, but steel wire is a lot cheaper than carbon fiber.

I don't know why I haven't tried it yet.