Scratch build suggestion- FT DLG

[Allen2688]

Ever since the DLG video that you guys have made, I have grown a real interest in DLG but i don't have the money to buy one. I would love to see you guys design a supper cool (As always) DLG that has a 950mm wingspan with supper small airfoils and that is durable.

Post your idea's below guys!

 

[rockets4kids]

I think you might be underestimating the difficulty of designing and building a respectable DLG.

Something like the Alula might be do-able, though.

 

[Allen2688]

Yea your right and the Alula might be perfect actually, its small and portable!

 

[earthsciteach]

I'd love to see David scratch build a DLG. It certainly is doable, but to be efficient, it would require techniques beyond the dollar tree swappables. That being said, it would be awesome to see David unleash his talents on something like this. He is certainly more than capable.

 

[kingbee]

Hi guys

if i get this dlg =glider. if it is tell what so hard in building a glider ??????

 

[rockets4kids]

I was under the impression that OP wanted a design he could build himself, not merely as a challenge to the FT crew. I have seen some scratch-built copies, so it can be done. I cannot recall what they were made from, but if you want a true discus launch, I'm pretty sure you are going to need to use EPP or EPO.

 

[earthsciteach]

kingbee - DLG stands for discuss launched glider. These are hand launched by holding a peg on the wingtip, and launching as if one is throwing a discuss. These are very lightweight and very efficient in terms of aerodynamics and airfoil design.
http://flitetest.com/articles/discus-launch-glider

 

[kingbee]

Hi eathsciteach

I see we are far way from foam board but more in to Composite and Carbon & Graphite Raw Materials thank you .

 

[Allen2688]

I have been thinking of ways myself to design a Dollar tree Foam board DLG and have some ideas like a really efficient airfoil and such that im going to try and ill post them here...some things im still thinking about are how to make the launching peg strong enough for repeated abuse for each launch probably impregnate the foam board with some good resin or something similar, and still wondering what I am going to do as far as the boom to go to the rud. and elev. Please hit me with any idea's!!

 

[Craftydan]

I have a sneeking suspicion David has tackled this, but not to the point he's willing to talk about it.

If you observe from the first minute or two of the glider challange, David is carrying a glider very reminicent of a nice DLG, which appears to be made of foamboard and a CF arrow shaft. When he gets to describing his build he tosses it away . . . and he's been elusive about what that glider was ever since . . .

I think he's cracked it, at least in a less than optimal sense. I expect the techniques he used are difficult to repeat/teach and and the finished product is nice, but not a refined DLG.

That's my guess. The alulla proves, if nothing else, that a foamboard DLG can work. I think it can be done, would be hard to build, and it'll fly okay but never be competitive in anything but price.

 

[rockets4kids]

One technique I have seen is using a strip of carbon fiber tow impregnated with epoxy applied to the top and bottom of foam wing surfaces at the wing's thickest point. That, coupled with tensioned film covering over the foam just *might* be sufficient to survive a discus launch. That would be one, non-agressive launch.

In any case, there is a *reason* why the cheapest DLGs cost close to $300, and you really need to spend upwards of $500 to get a *good* one. A whole bunch of reasons, actually...

 

[earthsciteach]

I was chatting with David on fb a few months ago and asked him about the viability of a scratch built DLG using wings made from hot-wired foam board insulation (XPS) and fiberglass. I don't remember his exact words, but he definitely had his doubts about it.

I wonder how much his expectations of performance come into play. It would definitely possible to build one, but would the performance of it make it not worth the time?

 

[xuzme720]

The launch imposes significant stress on the entire airframe, not just the wings. Watch the flex in the tail of this one on launch. And that's a proper carbon fiber bird.

To keep it light enough and strong enough requires a material beyond what DTFB can provide. I have no doubt that a DLG can be built incorporating DTFB, but nothing but? I really doubt it. If you build it beefy enough to stand up to the launch, it's just not going to be light enough to be an efficient glider. Which is probably a major reason why we haven't seen one. The Alula comes close, but it's basically all wing. No fuse to worry about flexing on launch.

 

[rockets4kids]

So.. it turns out you *can* scratch-build a respectable DLG with foam and packing tape after all:

http://www.flitetest.com/articles/cheap-simple-foam-dlg-with-good-performance

 

[xuzme720]

So.. it turns out you *can* scratch-build a respectable DLG with foam and packing tape after all:

http://www.flitetest.com/articles/cheap-simple-foam-dlg-with-good-performance

That's not Dollar tree foamboard! But it does reinforce the point I was making about how much stress is on the airframe during launch as he is using a 8mm carbon tube for the fuse. The white foam wing is a surprise as that type of foam is pretty weak, so I'd guess that the packing tape on it was put on under a little bit of tension for stiffness and strength. All in all, a pretty cool build and if you have a wire cutting setup, it should be a quick and cheap way to get into DLG.

 

[Craftydan]

That's not Dollar tree foamboard! But it does reinforce the point I was making about how much stress is on the airframe during launch as he is using a 8mm carbon tube for the fuse. The white foam wing is a surprise as that type of foam is pretty weak, so I'd guess that the packing tape on it was put on under a little bit of tension for stiffness and strength. All in all, a pretty cool build and if you have a wire cutting setup, it should be a quick and cheap way to get into DLG.

No, it's not DTFB, and the cabon tube can't be bought at dollartree, but it can be bought at walmart -- or any store that sells bow hunting gear. a CF arrow shaft would be a suitable substitute and can easily be sourced locally for less than $5/shaft.

As for the foam, no it's not the same, but could we strip, laminate sand and tape the wings using DTFB? I say absolutly.

Not everything we use for the airframes can be purchased at dollar tree (music wire, for instance). My understanding is the common FT design goal is maximizing commonly available inexpensive materials, not one stop cheap shopping(thoug occationally, one leads to the other).

Can it be done easily? Repeatably? dunno. I'd like to say yes, but I'm not clever enough to hit on an idea how, yet. With any luck and inginuity someone here can get there, and as the article shows, there have been folks who have gotten darn close with their commonly available inexpensive materials.

 

[xuzme720]

I think I was mixing up threads. I was thinking this was the one for a DTFB DLG. This one was just asking for a cheap, easy DLG, which is a very different matter. The above linked build is a perfect example of cheap, and should be easily modified to DTFB wings using EAL techniques...Might not be as efficient, but still doable.
Sorry, I didn't mean to come across like a DTFB elitist. (How weird does THAT sound?!?) I was trying to answer an OP from what I guess was a different thread...

 

[earthsciteach]

What would be the performance requirements of a DFTB DLG? What time aloft? Just thinking...

 

[rockets4kids]

Anything that would withstand the stresses of discus-style launch would classify it as a DLG. Then you have a *huge* range from there up to competition level.

 

[rcspaceflight]

I was going to butt in and say that the point of a DTFB DLG is for a cheap beginner DLG. Not something that is as good as a $300 DLG, just something that people can practice with so they know if they want to get into DLG enough to be worth the $300 for one. Plus it would be nice to have a decent technique to discuss launching before throwing $300 into the air and hoping for the best.

You guys kind of said that already.

This is something I've been working on, off and on, for a while. I have it all figured out but I'm working on the details. I'm making mine out of DTFB, wire safety flags, bamboo skewers, and packing tape. ... And that is all. No carbon fiber. Nothing expensive. I find making my wings tedious. But it's not hard to make them. It's just tedious. Mostly because I still have to figure out the details of the wings and not knowing if it's right makes it hard to want to build them.

I will be using this other thread to up date my progress. Although I was hoping to build a test plane yesterday... http://forum.flitetest.com/showthread.php?6295-Super-Light-DTFB-Glider We'll see how much I actually work on it. It is hard to motivate yourself to work on a new design because you don't know if it'll work, at all. Even though I did test out a lot of the different methods I'm using.