Didn't anyone ever tell you to always hold the model AT THE CG point when you toss it. The force, when applied applied to the tail, will always cause the rear end to try to trade places with the front end. Accelerating Force applied at the CG will be more effective. Think of it like this; You are standing on the middle of a skateboard and someone shoves you with force -you and the board both accellerate at the same speed. Now, have someone violently shove the BACK of the skateboard (and not you) and the board will shoot out from under you. This why your plane goes wonky when you are swatting it with the atlatl.

Attach the atlatl on a bottom of a fuselage forward of cg, maybe even forward of wing leading edge

@smartcatcollarproject5699

6 жыл бұрын

This is clearly the main issue here, best position would be from the CG and forward, but in this case you couldn't hold the atlatl and the plane with one hand, or the atlatl would be too short ! Or you'd need a specially formed atlatl with a good grip on one extremity, and a forked end attached to a small stick protruding on both sides of the fuselage, this way you could keep your plane balanced on the atlatl 1 meter behind your hand before you launch... Edit : yes the kind of system like in the url at the end...

I think others have the right idea of launcher connection close to cg.

the stability is also iffy because the contact and pivot point is at the very end of the plane. If the launching / pivot / connection spot was at the CG, maybe that is more controllable. No?

Really interesting to see the issues and work arounds of this idea! I suppose pushing an aircraft from the rear is like throwing a dart backwards? The 3D printed aerofoil rib just caught my attention as I've literally just finished building a plane using that technique haha

I think your launch point should be at cg or a little forward of cg. Look at launch point on high start gliders.

I've had a similar idea rattling around in my head for a few years. I think you can solve all your problems by having the atlatl attach point ahead of the cg.

Launch from the CG

What a fun project! I remember that spear setup as kid about 175 years ago on National Geographic. As a product development guy, I look at what is it that your actually trying to do. Make it behave like the spear or luanch it like MAD! Take an ugly stick fishing pole, pit a small loop on the end. Place a standard hook on the belly of the glider AT CG. The Super speedy launch would work better with a much narrower wing design therefore wider. Treat the pole as a massive extension of your arm. Stop your rotation at about 1 o'clock. The string will come off the hook by itself. Fly fishing 101.

I like that you are confident enough to put those funny outtakes at the end.

@MarkCastator

6 жыл бұрын

Awesome video. Love it. As an artist, one of my favorite things to do is paint myself into a corner and then see if I can get out of it. If I can figure out then I can do my little "I'm a genius dance." If I get stuck, that's okay as well.. The most important take-away for any creative is "Dare to fail."

This is an awesome idea. I used to try Making how to vids on Atlatls when I was young and am deep into rc planes now!

please make the launcher connection be much closer to the CG instead of at the back of the plane QQ....this idea would have worked perfectly from the start if you make most of the weight be pulled by the atlatl rather than pushed by it. Awesome concept though!

Try launching from nearer the centre of gravity say halfway between wing and tail

What if the atlatl grabbed the plane at the CG point rather than the rear end?? That ought to eliminate the sudden down force at the end of the launch stroke. Using Hi-Starts or winches on our gliders, the attachment point was ALWAYS at or very near the cg.

Your foam build technique is brilliant. Nice to watch such fine craftsmanship. Thanks for sharing the plans !! That is awesome.

Love the experimentation great job.

The key to bungee launches is to move the hook well ahead of the cg, like 2-3 inches... Then when you let go, dont point it up at the sky.. Point it directly ahead.. Dont touch the elevator.. It will climb all by itself.. If you try and pitch up, it will loop or stall hard on the winch.. If the cg is too close to the neutral point, it will drag its nose in the dirt.. Oh and at least 50% expo on the elevator...

I did enjoy this. Congrats on honesty integrity and craftsmanship!

@jimmyhaley727

3 жыл бұрын

and building a very tough plane

Could you launch it just forward of the CG. It looks like the pushing from the rear is flexing the body throwing it in all directions. Most gliders are towed from near the front.

@LucasWeakley

7 жыл бұрын

I think that might be something I try. I originally avoided doing that because an actual atlatl is really dependant on utilizing the longest thrower possible and to do that the dart has to be pushed. But since the plane has gotten so small, If I can get it to launch reliable being attached to the nose, then I can use something like an extremely long fishing pole to whip the plane in the air. Check out some of the videos I linked in the description to see something similar to that.

Great video, i hope you get the concept working soon.

Excellent video, cool stuff.

Very interesting, thanks for sharing :)

The leverage from the Atlatl stick should be superior to that of the discus glider launch if the attachment is at or slightly in front of the CG.Very similar to the attachments of a high powered electric winch launch. I miss the competition winch launched flying in our old RC glider Club in Memphis. A little competition works wonders for interest in this sport.

Sick idea!!

Love the engineering there!

In Australia the local aborigines had their own version of the Atlatl, they called it a womera. Basically the same device, it allowed them to throw a spear at a kangaroo faster and further thanjust using their arm.

Sure it cab be done. I remember Mark Mech of Aerofoam UAV Systems atlatl launching R/C gliders in Phoenix over 15 years ago.

This was awesome, the concept, the video production value, the maths - Man! Super job. I get as far as doing a 'rough' build without any maths and leave it at that ;)

I had been thinking of using an atlatl to launch my flying wing gliders. The problem I have was not so much getting a good throw off the slope, but holding the wing steady as I threw. A strong gust of wind would grab the wing out of my hand or worse would cause a barrel roll as I released it. My friends and I made a couple of atlatl's to experiment with out in the desert. Once you got the hang of them it was possible to launch a spear easily 50-60 yards.

have you tried making the wings at an angle instead of compensating with the elevators?

Would it not work better to launch the Atlatl from the CG of the plane?

@Nathaius

6 жыл бұрын

maybe even from in front perhaps.

Setup a launch trim switch. This will help with some of the automation you want. Another is to have where the atatl attaches closer to the CG would also help.

Hey man, the problem is simpel, the anchor point for the launching arm is way back, way behind the CG. All moments of the aiplane go around the CG, so a slight disruption of the force of the arm not pointing straight to the CG will cause a huge moment which will cause your plane to pitch up or nose down regardles of how well you balanced and trimmed the plane. The back of the plane is just a very bad place to launch a glider. A spear resists this moment more easily due to it's high mass and flexibility. An airplane is very light, and has a big wing which makes the moment exponentially larger, this is why your plane either dives down or pitches up and stalls. The simpelest solution would be to put your anchor point as close to the exact location of your CG, that should work like a charm and possibly be way better then DLG when you try different throwing arm lengths

@JoshWeaverRC

6 жыл бұрын

PaperFun. It was a pretty light plane he was using. I think he was getting lift before he released, but his tail was not lifting. For a heavier plane that will get less speed it won't lift as much. My only point is that I can't discuss launch one of my heavy wings, and I want my arms to have an extension. If I were to try to beat a DLG it would not be this technique.

@JoshWeaverRC

6 жыл бұрын

Some stabilization to keep it level while launching would help.

The issue looks to be the vector for force vs the vector for lift. The plane needs to maintain its vector as the spear does. I think a longer and more flexible arm that has a pivot point so as to always maintain force vector in line with CG would help. Build up force, have an electronic stabilization through a canard maintain level and get the snapping of the rod to impart speed.

Lucas, why don't you try to connect the throwing stick at the front of the plane rather than the back. This way you won't mess with the CG when throwing. You can still use the stick to throw depending on how long it is.

@joewoodchuck3824

6 жыл бұрын

George Georgiev. I don't know if my suggestion truly has to do with CG or not , but wouldn't there be better control over launch angle if a forward tow hook was used as is done with a high start? You also can try various hook positions that way instead of only the tail position.

you just discovered why the horse is put in front of the cart, rather than behind.

Have you considered hooking towards the front of the glider instead of the tail? It would definitely handle launch stress better and likely easier to CG for launch and glide

I had a similar idea when throwing the dogs ball using the throwstick. I wanted to launch a glider using a throwstick but... I would attach the stick on a hook at the cg and not at the tail.

From seeing the photo of it, (as it is a flying wing), you must have a relfexed trailing edge, where the last 1/2 " edge of the elevons needs to be bent/ shaped upward approximatly 15°). Also usually with flying wings the trailing edge control surface is a narrower strip elevon. Enjoy!

It may not ever work with a plank: too pitch sensitive. The demo of the spear launch shows a LOT of flex input...spear is vibrating a lot in flight. The atlatl contact may need to be closer to the CG. That means a shorter atlatl. Trade-offs! Have you posted this on RCGroups?

That launcher is Woomera technology 🤣

Cool video. The soccer field and dorm buildings look familiar lol. Cheers from a fellow Eagle.

awesome video: maybe you mixed it this way already but, if not, mix elevator into the left thumb stick so that when you pull the thumb stick down to the left, the elevator goes to the launch position. When you release it the elevator will return to the glide position.

I understand your challenge and trying but the fact is, DLG works. Very well. Normal launch hights for my balsa (MiMi) DLG are around 48-55 meters and the fullsized are around 65-70 meters. Should be plenty to get decent flying time or catch thermals?

if you moved the point the atlatl hooks into the glider to be just ahead of the CG, likely much easier to put more shoulder into it

Perfect hair, wild untamed beard.. Didn't know your back to RC..

I agree with Paperfun. For what it’s worth I did something similar 20 years ago even before dlg were a thing. I used a zagi wing which was a slope soaring plane and just behind the cg I taped a hook. I attached a small ring to a fishing pole. Think a surf fisherman and you might get an idea what it looked like. Maybe try a FT Arrow wing and the atlatle. I think your on to something. The beauty now is you could 3d print some connection for the throwing stick. My bent coat hanger didn’t do the best. Cool video and great point about learning! Didn’t work is still learning!

very cool idea ! Very good maths skills ;)

Hello 👋, liked your experiment. You might want to double the length of your throwing arm. Put a hinge in the middle of the arm that will stop whin it is strate. Move the ancer point ahead of cg & center of pressure. Just a thought wish you luck.

I was thinking of doing this with my sons glider, but then forgot to try it! Cool video!

I think impacting the ground at high speeds over and over again puts a great deal of stress on the airframe.

you could try making the spear and glider seperate that ould give you nose weight when you launch and glide when they seperate

watching this video and I'm like, hmmmm that field and those buildings look familiar... you go to riddle lol

I wonder if something like a bow or cross-bow could be used?

@johnjriggsarchery2457

6 жыл бұрын

Funny you should ask. I launched a glider from my crossbow this morning. It had some trim issues, but it worked better than I thought it would, being launched from an actual medieval crossbow. Here's the link: kzread.info/dash/bejne/rGZqlbCbj7vWfJc.html

@lw216316

6 жыл бұрын

cool, very cool.... I think the pressure would be too much for my foam glider....anyway, I've moved on to a powered glider....it is so much fun seeking out updrafts, finding them and turning off the throttle.

Why not move the launcher forward ?

What about launching it from the nose I wonder if that would do?

@timsurgison9076

6 жыл бұрын

rc-nut 1 or how about from a normal tow hook position

Very interesting project, great experiments and story. DLG's typically have 3 portions the flaperons can be: launch, thermal and cruise. This works because the flap positions change the centre of lift (for/aftward) along the wing cord (which works like making a small tweet to the C/G portion) This however flaperons require a conventional tail design as doesn't work on a flying wing design.

Looks like an interesting idea... I notice that the end of the launch causes the tail of the glider to move down, diminishing the effectiveness of the launch. What if the contact point of the launcher was farther forward... perhaps the same place as it is for a hand launch? This might make the launch more balanced and controlled. If the launch point is in the Center of the body perhaps a forked launch stick could accomplish this.

Wow!!! What a try-er you are, sir. I think that you should first get the plane to fly properly by gentle hand launches. Then program your Tx with some down elevator (switch operated), just enough to hold the climb trim to an acceptable level, then when it levels out operate the switch to put the elevator to glide trim. Best of luck, buddy. Never give up !!!

set it up to launch off of the atlatl from the cg. think winch launch location on a F3J glider.

Nice idea! Look at how this guy did it- I think he attached his in front or right at the CG, like another comment says. His works great but I'd love to see what yours can do when it's really adjusted right!

@sashalofstrom6659

6 жыл бұрын

kzread.info/dash/bejne/gadsxauAocvQkbA.html forgot to link, lol...

Cool video, cool idea, and awesome presentation! I love that foam, cheap electronics, and the maker attitude gives us videos like this! Some suggestions: I fly DLG. You should consider a flight preset for launch on a momentary. For a DLG this preset is pretty held until launch and then released right away. It basically just makes the model rotate. You throw the DLG horizontally, not with any upward motion. Check out the hand launch forum on RCGroups. Also consider your materials. Go back to your calculations and see how much force your placing on the model. It is significant! DLGs are made out of composites. My basic DLG is around 250g. That's for a 1.5m span. I launch to 40m. There's a ton about how DLGs are designed to handle launch loads. For instance, the rudder extends above and below the boom. This is to offset the torque moment that is placed on surface. Keep up the cool videos and ideas!

The reason DLGs are so special is because you're not allowed to use launch aids in the competitive f3k class. The SAL is simply the best way we currently have of tool less hand launching a glider. Using tools a simple launch line is way better than a sling type launcher. Back in the day before rc that was the way to go with gliders. Using launch lines you could actually look for lift and once you felt it just pull on the line and it releases.

That looks cool plane atlatl hand launch throw flights

2 things...common sense.. launch from the front of the plane not the back.. 2ndly use your adle launcher sidearm.. 3... longer adle stick for the original plane.. calculate that next time to equal the hand launch speed..instead of changing planes

I thought about a launcher arm that extends the thrower's radius during a discus launch...

I think this style plank style wing has around 10% CG at the front of the wing. And it must have up elevator or reflex. I think you done it well in first try

As others have commented, I think the attachment point should be closer or at the CG. I think this would make the launch easier and less sensitive to minor variations. But ultimately it seems as though the throwing arc wants the plane to go down, while you want the plane to go up... Fighting the direction with elevator trim seems like wasted energy. Most other activities like this - golf, baseball, dlg, etc - benefit from good follow-through. This seems to work against that.

It looks like there are some stability issues on the launch. Perhaps try connecting the atlatl in front of the CG. You could also use a hinged atlatl (the atlatl is in two pieces with the hinge back near the tail or behind the aircraft and the connection point near the nose) to get the connection point in front of the CG. The connection point and forces would be more similar to a tow arrangement this way. This may also help minimize the effect where the atlatl pulls down near the end of the toss.

@timhyatt9185

6 жыл бұрын

what if the tail boom was somehow detachable, that after launch it falls away, leaving the plane in a more normal configuration??

Somewhere along the line you decided for a flying wing. Wings are always more critical about the CG position (and more sensitive to elevator input), so should't you rather stick to a classic configuration? But, interesting video and impressive perseverance!

Hi. I think if you get the glider launching well using your finger first and then use the stick. From what I can see in your video the glider at its best only ever flys fairly ordinary. Get it flying, then add the variablr.

Enjoyed the video and going through the thought process. As a way to get improved stability in a simple solution I would a canard design, I actually had a canard rocket powered glider about 25 years ago and it worked well and I think the concept would work well for this project. If you Google Estes Astro Blaster you will find info on the old rocket glider.

Dihedral?

I find your presentation thought provoking. Momentum in the long fuselage (in the form of torque along the ventral line) behind the TE will produce initial negative decalage (splat) and then spring to positive decalage (zoom) which I think I saw. The other point is that you could have perhaps gained from more decalage in your design though it would have required more forward CG and wouldn't have fixed the launch issue. Allowing the use of atlatls in baseball would speed up the game.

Nice idea but there's a reason they don't aerotow full size by the tail

The launching arm is called a Woomera in australia, might be easier to say than Atlatl...

A spear is not only flexible but it has also no wings that would gave him lift at the front. The lift of the wings and the downwards kick at the end at release of the atlatl make the glider almost stall. You should try to make a bolt at CG and the atlatl with a kind of fork where the bolt fits into. when at release at almost vertical position the fork must be open to give it free..

to anyone who uses spektrum and wants to build a tiny glider dont use a 2s battery and a bec, get a cheap orange rx and power it with a 1s

I have an idea. Like spear fishing with a bungee cord. If you had a bungee cord attached to the end of atlatl to give tell launch additional energy.

this is similar to an idea i had to launch a glider with a sling so you have a string attached to the nose of the glider with a little hook and swing it over arm and launch it like how a trebuchet would idk if it would work but itd be cool to try it

@lucywucyyy

2 жыл бұрын

i just had another idea, what if you attach a long string to the wingtip of a glider and discus launch it by swinging it from the string, you could make it go really fast

Flying wings are a whole can of worms, even with proper airfoils! They're great though. I suspect your nose-down at high-speed issue was in fact a tail-heavy condition. With gliders in particular we use a 'dive test' to check CG. With the plane trimmed for level flight, you point the nose down at a 45 degree angle and let the controls go neutral. The airplane picks up speed and any force the tail provides at level, stable flight is multiplied. The CG doesn't change, so a tail-heavy plane will tend to pitch down further, and a nose-heavy plane will pitch up sharply. A neutral CG will continue on it's 45' path downward, give or take. Flying wings in particular are super sensitive (as you mentioned), and a very very small change can make a plane go from a flying well to a fluttering leaf. Factors like approximated airfoils and aeroelasticity blur the lines further. You want a plane to fly well over a large speed envelope. I suspect that you would have better luck with a conventional layout or a proven, tested, and tuned flying wing with a good airfoil (an alula perhaps). I also thing it'd be worthwhile to do some testing with the atlatl pushing off the CG instead of the tip of the (extended!) tail. You will impart far less pitching moment. I realize it's not ideal for the throwing geometry but I think it would work better for launching an aircraft. Good luck! Hope this helps. Keep us posted.

I have an idea for making your set up more efficient and more stable in the launch. Since an airplane's fuselage being rigid is somewhat of a requirement for stable flight I would recommend making your airplane rigid and making the attachment point of the atlatl handle attached forward of the airplanes CG. Then keeping in mind that a real atlatl acts as a spring and stores extra energy to be released towards the end of launch simply make your atlatl handle flexible in the same way. Then you can quite easily use a tow launch style system attached a long string set the airplane on the ground and simply use the atlatl as your winch mechanism. This should be able to give you stability in your lunch because you're attached forward of the airplanes CG and still deliver all of the Addle Addle momentum storage capabilities. I look forward to seeing your progress in this project I will be subscribing

@Kcburnit

6 жыл бұрын

Even if you don't use a string modifying your atlatl handle so that you attach to the airplane forward of the CG will drastically improve your launch stability no matter where you place your CG

What about a more forward point of contact for the launcher? I know the point of the atlatl is to have it at the rearward most point, but you're putting the "center of thrust" well behind the centers of mass and lift. When you go to throw it it's pretty unpredictable. If you move the location of the atlatl connection point just ahead of the CoM, it should launch much more consistently.

Australian Aboriginals called it a Woomera.

Try adding a horizontal stabilizer and an elevator, the problem with many tailless aircraft is that the wing wants to naturally nose over. How do you combat this, well, either add a tail, or add reflex. In this case it looks like you added a bit of reflex and got it to launch really well. Personally I would try adding an elevator and that might help. Theres a reason you dont see a lot of tailless DLGs

Just put your atlatl hook in a piece of carbon tube fixed underneath the fuselage just forward of your cg so you arnt putting too much spring in the back but more throw in the front

The problem with re-inventing the wheel is trimming off the square corners......any launch device needs to be added only after you have a finely tuned flyer........C of G, wing loading and drag reduction first then, power loading.....if you must use a flying wing design, remember that the longitudinal dihedral comes from a reflexed air-foil and they are inherently sensitive to variations in airspeed..........basic theory of flight for a free-flighter.....good effort on your idea.....

The glider flies dreadfully. Fix that first.

The problem is the profile of your plane. You have to grind the front bottom of the wing. the wing have to be neutral in the air. like the profile of a deltaplane

@CoernelSkateboarding

6 жыл бұрын

if you corect the profile when you pull the ruder, then you loos a lot of energie

It is too light more force you put on it more it will misbehave . That is why most of the DLG's are made of hard material and not just foam board. When you push hard the foam and the rods bends and it modify the angle of attack and then you just either have to add weight on the nose or go into a loop. When you dlg the force is sideways on the wing. Try with less flexible materials and less force then increase from there onwards. Good luck

Don't know about an Atlatl but the launcher is called a Woomera and is of aboriginal Australian origin if correct.

@abates3747

5 жыл бұрын

I'm an aussie, so not being prejudiced, but pretty sure that the atlatl is older than the aboriginal woomera. pretty sure it's just the boomerang that's the unique tech of the aussie aboriginies

You should try a longer tail moment. It will get more stable as it gets longer. Currently with the flying wing configuration you have an extremely short tail moment :P

Use a DLG preset launch 2% to 8% up Elvavons when launching . Then have Elavons center after launch.

Atlatl. Also known as a 'Woomera' in Aust.

Need to think along the lines of a trebuchet mechanism on your atlatl arm. This would greatly reduce the angular loads and increase the intended velocity. Let's see what you can do with this?

I think you problem is the center pressure and CG are too close together especially with that long boom out the back. If you can afford the weight move the the tail further back and add a horizontal stab to bring the center of pressure back. Plank designs are very sensitive to any changes in the CG and pitch inputs. I fly a plank at my local slope and it literally has 3mm elevator throws. Without out a horizontal stabiliser it will always want to pitch up or down when push it that fast. Think of it like shooting an arrow without fletchings it will always tend to tumble(Plus I'm sure everything is flexing from that rapid acceleration) If you want to stick with that design you will probably need to add some reflex on the trailing edge to prevent nose dives (this is why it started to work with full up elevator trim). Plus you will need to stiffen it up quite a bit. Making it more like a conventional aircraft will make it way less Pitch/Yaw sensitive and your CG placement will matter less.

So many possible ways to achieve higher speed at launch that are inherently better than an atlatl, in that they do not introduce so many extra variables. a few tips keep the airframe of the aircraft rigid. any flexibility should be in the launch device. use a more conventional aircraft layout, to eliminate variables there. make the fulcrum (or attachment point) between the Atlatl and the aircraft further toward the center of gravity, to eliminate the tendency to go unstable during the coupled part of the launch. So, basically launch the glider from the nose, rather than the tail. well, just my 2 cents. good luck!

Why not try it 'properly' and have a flexible atlatl and rigid(ish) plane? why do it different than the thing you're trying to copy ?

I know you've probably moved on faaaar from the project, as you posted the completed five back in 2017. Did you or any of your colleagues/collaborators ever consider going as far as using a catapult-deploy 'Swing -Wing'? There is a modeler who creates catapult & rocket powered gliders....that use tensioned rubber bands & springs to deploy long wings at apogee of launch, form a folded-back position. They flick out & provide the glide at height. I think this approach--preserving the javelin/'spear'-type configuration through the atlatl launch phase...then going 'Wings OUT!' at height...would deliver good results, eh? I know...I know--just another level of complexity creating the swing-wings & coordinated 'deploy'-mechanism, of sufficient rigidity & smooth movement.

Go read up on a reflex airfoil, your plane is short coupled you need to use the wings themselves to stabilize. Look up Charles Fauvel