Discus Launch Gliding

Hey guys. I though I would start a thread just on discus launch gliding. Feel free to post anything you want on here about DLGs such as scratch building, recommended gliders, thermal techniques, etc. I am new to DLGs so if there are any experianced pilots out there, feel free to give out tips to newbies. I would like to know how to build a nice thin airfoil out of dollar tree foam board as well. If you have any ideas about that, post them here too.:D
 
I did some research and found two discus launch gliders that seem to be very good starter DLGs. These planes are the dream flight libelle and the supermini topsky DLG. they are both in the $100- $200 range. The links for the sights that they are sold on are below

http://www.hyperflight.co.uk/products.asp?code=SUPER-MINI-TOPSKY

http://dream-flight.com/products/libelle-dlg

If you want to go really cheap then get the UMX whipit for about $70. This is a rudder/elevator DLG that will be released in the near future. You can back order it now. The link for it is below

http://www.horizonhobby.com/product.../sailplanes/umx-whipit-dlg-bnf-basic-eflu3150
 
DLG wing build question

Does anyone know of anyway to build a nice thin strong lightweight DLG wing? What materials should be used to do so? How should it be done? Would it be hard to do? Any cheaper methods of making a DLG wing? I know that DLG wings have to be very thin and strong but how thin? What materials can be used to make a thin but strong design?
 

finnen

Senior Member
The materials for a dlg wing don't really need to that expensive. From what I understand, you can wire cut the shape from foam, and then cover in glassfiber, and some carbon spars. What makes it difficult is that you need to have a vacuum bag system to make it as light as possible, and get a smooth surface. I have been thinking of making a wing by just brushing resin onto glass, no vacuum. I have kind of abandoned that idea. Either I'll make a vacuum pump, and try to learn that method, or I'll by a used full size DLG if I can find one. Til then I have a libelle to toss around =)

There are some planes with built up balsa wings, this project seems interesting, he is just about to start making kits:
http://www.rcgroups.com/forums/showthread.php?t=2337864
 

finnen

Senior Member
First of all, it's fun!

No thermalling weather here, so can't say anything about that. Launch height, hard to tell, maybe 25-30 meters? This is my first DLG, and even my first glider, so I have a lot to learn. For that the libelle is great, becuse it's tough. I can't remember how many times I have stalled it when trying to get just a little more flight out of it, and it slammed into the ground =) Cartwheels also happen frequently...I thought I was fairly good at flying, but man, not having a motor makes it difficult :D

Which of course is the fun part, learning something new. I can't compare it to anything else, but I'm happy with it. Build quality is great, easy to put together. I did however reinforce the wing saddle, as many report that it can become soft after use. That was just 10 minutes with some CA and some pieces of gift card, so no problem.
 

DKchris

Member
On building methods/materials: If the glider doesn't have too large of a wingspan, the vacuum setup can be left out. A quite successful example is the DL-50 dlg http://www.mountainmodels.com/product_info.php?products_id=212. Its 50" wing is a hotwire cut foam core with inserted carbon rods and a little bit of CF cloth for increased strength covered with glass using minwax polycrylic waterbased laquer. The linked page contains a complete manual describing the entire process.

And as far as I can tell, smaller planes can be done just with DTF and a bit of ingenuity: http://forum.flitetest.com/showthread.php?16418-Cheap-Mini-DLG-1-2-sheet-DTFB

On that note I'd suggest looking into box/pallet strapping band reinforcements as brought up and used by Davereap:
http://forum.flitetest.com/showthread.php?9016-A-simple-flying-wing-method
and
http://www.rcgroups.com/forums/showthread.php?t=2047264
I believe there is a mountain of opportunities hidden in this material for foam/DTF scratch builders!

This of course doesn't mean a vacuum system isn't a nice thing; It's amazing for gluing stuff together with complex shapes that just have to stick optimally together with an absolute minimum of glue weight .........and I honestly believe you'd probably never get to the level of entry level F3K contest competitive aircraft without it...........but that doesn't mean there isn't a ton of fun to be had with slightly smaller planes!!! Just watch the weight, keep it simple and remember to think out of the box every now and then......
 
Last edited:

finnen

Senior Member
Also, there are some ~100cm balsa planes that are fairly easy to build. Two that come to mind are the MiMi and the Bug. I think the easiest way to get information is to search for those on rcgroups, although I believe there is a nice Bug thread here on the FT forums.
 

ztoon

Gone with the Mistral
I keep doing some "launches only" session (tip from an advanced F3K pilot). 30 minutes of up/down/up/down...
Minimal power, trying to focus on the throw technique only. Even exercise is fun with a DLG :D


Sorry for the "youtube quality", the original file is much better. Maybe I could try dailymotion...
 

ZoomNBoom

Senior Member
I love DLG's! But I do have some bad news; IMO cheap/DIY/balsa DLG's are fine for learning the basics, but if you dont have a proper (and you may unfortunately read that as fairly expensive) 1500mm DLG, you will probably not achieve > ~30 meter launch altitude and your chances of actually finding a thermal are dramatically reduced - and so will your pleasure. You will toss and land, and toss and land, and toss and land. Maybe do a loop and land. And while that is fun in its own way, the novelty will wear off quickly. The real pleasure for me is in throwing a plane, finding a thermal, and getting up and flying longer than most electric powered planes.

THing is, thermals dont often reach the ground, they tend to form higher and most of the instability is also up there, and thats why its so important to be able to throw your plane above that. And thats why, after you got the basics down, a good DLG is a very different experience as most cheap ones. So if you are serious about DLGs, by all means start with something cheap, as it really sucks to pay $500+ and have a wing tip hit the ground on launch , but prepare to pay at some point. Doesnt mean you have to pay €750 for the latest best thing, for some perspective, I recently bought a second hand Twister I that needed some work for just €150 and its still an awesome DLG. But typically expect to pay at least 2-300 for a decent used carbon model.

Another thing I will say; I recently got a variometer for my DLG (frsky, in combination with my taranis). And its superb, but a double edged sword. On the upside, it really helps perfectioning your launch technique, because it will tell me the altitude after each throw, and on a day where I would catch thermals maybe once every 5 or 10 throws, I will now catch one every 2 or 3 throws. The downside: you become reliant on it, and you may stop learning "seeing" and feeling thermals. And if you ever fancy doing competition, telemetry is not allowed, so its not good practice. But if you just want to make it easier to catch one, or stay in one once you are >100m high and it becomes nearly impossible for my eyes to see if Im still climbing or not, a high precision vario makes all the difference.
 

ZoomNBoom

Senior Member
@ztoon, just a tip: you will get higher if you launch it steeper. Add some up elevator trim for your launch setting, and if you are not doing so yet, consider a launch switch that you only hold until right after release, that adds more up elevator (and some down flaps) that will make it rotate nearly vertical. I only recently started doing that, had to change the switches on my taranis so the momentary is on the left now, and still learning it, but it does seem to help. Either way, you want at least a ~60 degree climb angle. 80+ is better, but it becomes more difficult to see.

And since we're posting vids, here is one to proof I do think launch and catch is fun, I was doing it at nearly freezing temps at 8:30am. No chance of catching a thermal (especially not while carrying a mobius, which costs me 10-15m launch altitude and severely degrades gliding):


The second part has some rearward looking footage, nothing too spectacular.

Here is another one where my brother fights with a weak thermal, that shows the vario in action:

 

ztoon

Gone with the Mistral
@ztoon, just a tip: you will get higher if you launch it steeper. Add some up elevator trim for your launch setting, and if you are not doing so yet, consider a launch switch that you only hold until right after release, that adds more up elevator (and some down flaps) that will make it rotate nearly vertical. I only recently started doing that, had to change the switches on my taranis so the momentary is on the left now, and still learning it, but it does seem to help. Either way, you want at least a ~60 degree climb angle. 80+ is better, but it becomes more difficult to see.
Report (late) after testing:
My launches are better now with a setting on the momentary right switch of my Taranis (handy as I'm throwing with my left arm).
It was bit 'trials and errors' to find the sweet spot but definitly better now.
I started with my HK composite dlg and now my used FW4.2 settings has been updated too.
But I discovered last weekend that the leading edge of the FW4.2 is cracked open for 20cm on both wings...:( No bad landing or crash... maybe just an old glider.
Must be fixed before flying again.
At the same time, I had the opportunity to buy a used 'home made but incredibly well done' F3K from a french fellow pilot. My 3rd F3K since I started with dlg last year... addicted?
 

ZoomNBoom

Senior Member
I just bought my third as well :).

First one was a superb Twister II, which regretfully after a year or so, I destroyed by being utterly stupid: wanted to test failsafe settings in the air, turned off my radio, and well, I wasnt high enough and the settings where not good.. at ALL, it nose dived and it took too me too long to turn back on my radio. My friend, whom I had bought it from, nearly killed me, because he had won the national F3K championship with that very plane a long time ago. Sad way for it to go :(

Second was a slightly worse and much older twister 1 that still looked brand new, and that I managed to buy for next to nothing, considering what these things usually cost. But I couldnt get it high, like at all, (~30m max) and if I tossed it too hard, it would flutter due to crappy servo's. My far more experienced friend fared not much better than me. She was also heavy, weighing in at 335gr, although thats a good weight for that plane, it does limit you on calm days.

So now I bought a tantalus. Ive yet to fly it myself, but bought it from the same friend (who still has at least half a dozen high end F3Ks) who demonstrated it quite convincingly. in strong winds, stronger than I would dare fly it, he tossed it 60+ meter! That means I should have at least a chance of achieving 40+m on a calmer day :).
 

ztoon

Gone with the Mistral
I added a 4th dlg to my fleet.
This one is a pcm fireworks 6 (version light). It's a 1 season used F3K glider in perfect condition.
Already achieve interesting heights with low power + performance in dead air is excellent.
My 3rd dlg is actually waiting for a spare fuselage, as something bad happened to the original one.:p

 

ZoomNBoom

Senior Member
You're left handed? Must be hard to find used DLGs with the pin in the right place!
And if I may say, I think you need to try to launch faster. Its not about force, its about rotating as quickly as you can. Your throws seem very leisurely, but maybe thats also the fish eye of the camera. Plane looks very nice! Enjoy your new addiction.
 

FBMinis

Junior Member
I will keep an eye on this thread, as I would really like to develop some skill and build under-60cm hand launch gliders (foam, balsa, etc). I have seen some beautiful and efficient japanese-built balsa gliders on youtube and other sites, but so far I've only experimented with foam KFm airfoils.