Supersonic Darts - The Effects of Inducing SPIN - I learned something! 

Any sufficiently advanced technology is indistinguishable from magic. -Arthur C. Clarke

Exacto knives these days are futuristic. WW3 joke btw

My favorite kind of sorcery

I'm so shocked these gunmen also know warlock magic

to make it spin without bending the fins chop the trailing edge dual bevel to a single as in from this /\ to this |\ or /|

I'm seeing a meme of "straight Finns vs not-so-straight Finns"

Thought they'd use the Beyond the Press couple as an example of straight Finns.

Perkele!!

@@st3v3h4py "Not so straight Finns" are called swedish-speaking Finns.

@@Tunkkis Man I would hate to be Finnish and have someone use my likeness to demonstrate a "Not so straight Finn"

I absolutely agree with you.

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-lXeyEeXS-cg.html check out what happens at the rear 3:35 on 4:00 a F-22. It has a computer controlled actuator for stable flight control. Be kinda hard to shrink for a shotgun projo.

if there is anyone in this comment section that plays Disc Golf, they, as well as myself, know exactly what you mean. any imperfection in the disc, both visible and non-visible, have a HUGE impact on the performance of said disc, whether for better or for worse, lol.

You highlighted what I tried to say in my comment much better, thx

Centerline has to be true or your have an unbalanced journal effect. Roundness also has to be pretty good. One point this video upload didn't touch upon is how the balance of the projectile affects its stability in flight. These points made concerning roundness and centerline regard projectile spin, they will affect it. Lengthwise the projectile balance point also has to be Forward-of-Center (FOC in archery) so the point -or head if you like- leads the tail in flight, and vanes stabilise tail swing so your dart will 'fly true' and strike hard. If you do not make total-dart-mass balance upon a point some percent forward of the mid-length, the projectile will tumble. Which means whether the head strikes the target point first, or does not, is only a gamble. It also means all the kinetic energy will not be transferred into an impact force directly behind the tip.

I think they were left over from the rider that one of his Country/Funk/Disco/Rock-bands from the '80s demanded to appear at a certain venue, along with 20,000 yellow peanut M&Ms and a gallon of Drambuie...

I’m gonna nerd out for a second. I think you need the whole fin to be angled, like how a supersonic fighter jet’s elevators do. possibly due to the shock cone not letting enough air pass over a small angled fin?

Also I wonder if the obturation ring is causing a vortex to extend out over the majority of the fin like a kFm airfoil?

@@mk6315 you're probably right. I mean traditional slugs have straight cut "fins"

Depends on the range also, because if it rips a gut, then what range to be at to make it vicious?

I say try with less of an angle on the fin.... say half of what you have now? Or Maybe try multiple shots & each one with a different amount of tail fin angle? Who knows? Maybe a certain degree of angel will make it work better than all of the rest? Although the straight fins shoot fantastic!

I’d be interested to see the water tank drop comparison if the tanks were 30 feet deep (or whatever). Over that distance the effect might be more obvious one way or the other.

That canting can be caused by the bullet not being dropped as straight when it entered the water, or dude not dropping from the center of the top

Spin reduces effect of poor separation on accuracy

thanks Andrew

I miss Danny... 😢

@@taofledermaus I wasn't surprised at all that the first spin stabilized dart's flight was erratic, if that was the dart shown at 1:13 with the drawn lines on the fins, because the fin angles (imo) were not symmetrical.

thanks Ian

YES! Exactly! Put the fins in front. That's what you meant, right? 🤪

@@dotar9586 what?

Rotating objects are stable but that's when the whole thing is spun, when that force is being imparted on an unbalanced part you get the wobbles.

@@-JohnSmith- In that case you want to get in touch with Fireball Tool and get some 0.3" steel rod with a spiral cut at 1 turn in 1.123 inches for that same 40° angle inside 0.4" steel sleeves with a 0.05" thickness, so instead of fins you have air channels through the full length of the bullet. It might also be interesting to have two sets of them, one solid all the way through inside and one with 0.2" holes drilled centrally up the back of the core to half the length, or multiple sets with multiple tail hole depths, to see how the shift in centre of mass affects behaviour.

That's why somebody gets to test it.

Don't forget to secure the target!

It would also help to get tequila drunk first and then lay down on a bed. You get some major RPM's doing that! Or so I've been told.

don't forget to shoot sitting on a office chair whilst you spin around

They actually need to set up a rig that will allow them to spin the rifle and have a wireless solenoid to be able to pull the trigger. Gotta try all the ways of atabilizing the bullet.

🤣

Yeah...lob em out 50-100 yards to see if it helps farther out

Exactly what I was thinking - also if the entire fin was curved/angled rather than straight with a bend as this should prevent shock waves forming where the bend is made? Supersonic aircraft have "all flying" tail surfaces to prevent shock waves forming where the control surface hinges would be otherwise.

@@Eatherbreather I'm guessing that the sharply angled fins might be producing turbulent air flow near the kinks. I wonder how a gradually curved fin, and at reduced angle angle (as suggested by David Jennings above) might improve rotational rate and accuracy.. As a side note, spin stabilization is frequently used in sounding rockets at average out payload trajectories. Of course, the aerodynamics become weirder as your test objects shrink so the comparison isn't 100%

@@Eatherbreather Any deflection in a supersonic flow results in a shock-wave. Even for a "all flying tail surface" will generate a shock-wave at both its leading and trailing edges albeit on opposite sides of the airfoil. The same applies to the continuously curved fin. In this case the leading edge will shock the airflow into subsonic speeds over the concave side of the fin, while the convex side will have gentle expansion waves that actually accelerate the airflow but will generate a shock wave at the trailing edge to shock it to the same speed and direction as the overall airflow. The purpose of having an all flying tail is to provide the pilot greater control authority over the plane.

@@abhijeetsutar5259 you're entirely correct! I completely forgot about the l.e and t.e shock waves 🤦‍♂️

Not all are straight finned. The US is going to slightly canted fins for better stability and accuracy.

@@markfergerson2145 roughly 1/2 a degree, per The Chieftain

Tanks are the exception to the rule. Any rule. Because nothing can tell an American Main Battle Tank what to do. They are the Chuck Norris of vehicles. Carry on.

@@Falconguygaming Yep, and he should know.

Tank APFSDS rounds ALL spin. Their fins are straight but not in line with the projectile, the entire fins are very slightly rotated to one side. Roughly half a degree, generally to give the projectile just enough spin to be more accurate than no spin, while not having any of the disadvantages of high spin.

thank you!

My thoughts exactly

I believe that spin stabilization through angled fins is only realistic if it's machined. Any tiny inconsistencies between the fins would result in asymmetrical spin, which would make it a lot less accurate.

On a fast moving screw stabilized by fins you would get no spin from the screws thread. The airflow would be moving over the thread and not spiraling through it. What the thread would most likely would do is disturp the airflow around the screw. That would make the airflow reaching the fins turbulent and therefore make them less effective.

@@Aircraftmechanical aye, I was thinking more in terms of the threads effects on target. Didn't consider the added turbulence though

@@Cheveyo888 There are some nails that have a square profile and a gentle twist to them (for better grip) that may be more suitable than the close spacing on even a coarse screw thread.

Good thinking

How are duey and reese?

where you gonna find a helical bird though? :p

thanks!

Ya i was thinking that with a sub 300fps(barely) arrow, the difference between 3° and 2° is noticable. 1000fps seems like a half degree should be plenty. Granted the surface area is smaller

Yeah I'm thinking this is just like adjusting the Helicoil or straight vanes when I'm tuning in the mathews monster compound arrows.

Might be something worth experexperimenting with especially with precision at longer ranges. The logic is sound, many fin stabilized projectiles have some degree of spin imparted by the fine (arrows for hunting or competition like ya'll pointed out and I'm fairly certain some munitions do too) I'm sure there's a "sweet spot" for the angle of the fins for a given projectile for a given velocity. But like you said, I believe that the ideal angle is much closer to 0 degrees ( like the 0.5 you mentioned). I'm sure there's some sort of physics/ engineering equation for this that would help narrow your experimental range of angles and velocities.

Spin for arrows is used to negate the archers paradox where the long and thin arrow shaft wobbles through the air

@@joearledge1 there is some tuning involved but I find a well made Helicoil arrow works well and have noticed preformed well outside over straight

But they do You can clearly see that the projectile winds up spinning speed as it moves trough the air. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Hu79sEA5X5I.html

imo i think it actually makes it worse. The fins already make the projectile extremly stable and no finned projectiles use curved fins. Arrows have straight fins, tank apfsds rounds have straight fins, rockets have straight fins. Spinning projectiles without fins are more stable than those who dont spin because of gyroscopic effects, but spinning fins would just ad more drag and therefor worsen the performance. Especially since the fins actually normaly prevent those projectiles from spinning. Thats what i think at least.

@@Okararu They actually do angle the fins on APFSDS projectiles at about 0.5° (so almost nothing at all) but even this slight angle helps it spin a slight bit and this stabilizes the round that extra little bit.

@@pierre-henrivince4591 have you got a source for this? I can't find anything online.

British Challenger tanks actually have anti-rotation sabots for their APFSDS as the spin reduces the accuracy on modern ammunition which is 1 reason nearly all MBTs have smooth bore cannons now.

It helps to pull the seperated flow closer to the centerline axis of the projectile by creating low pressure cavity flow. This is why the fins have airflow over them. Having a smooth surface would most likely result in flow seperation over the leading edge shoulder and then miss the fins completely.

Its always been a question with Archery to Helicoil or go straight vanes, tuned correctly. Not the same speeds at all but a Helicoil can help the arrow leave the shelf cleaner and recover slightly quicker than straight vanes. Traveling these speeds it is very intresting.

he is the "science".

@No Touchy Same goal, different approach. Simply comes from being a Task Force 69 veteran...

Depending on the length of the vane, the angle increases with the length of the flight vane

@@lukebaker1167 know but just keeping it simple bro

@@mikemitchell9157 2 ezy Mike!!!

Not that I'm exactly an expert on this by any means but as far as I'm aware the angles on fast moving projectiles when it comes to fins tend to be very small, having heavily angled fins, even like the ones in the video would come as a detriment more than anything else. Plus when it comes to spin stabilised projectiles that are actually in use they are considerably more well designed over all. (I'd also guess the design of the projectile its self has a lot to do with whether spin stabilisation is a requirement or whether it would even be of use.)

@@supercjs6044 I'm not an "expert" per say, either, but at 46yo I've had a tire or 2 balanced in my life. So I would have to agree that by putting spin on a fin stabilized projectile you're doing more harm than good.

@@Stacy_Smith As far as im aware a large part of whether its even worth it to begin with is the design of the round you're firing. Imparting spin on a round designed to go without for instance won't do much to help, among a million other factors.

thanks Desmond

I thought that looked like JR.

Not just the aerodynamics of the bend, but also the way the bullet is seated in the casing. I have the feeling that these sorts of bends are just asking for defect related inconsistancy in flight.

@@Keldor314 Yeah, in all fairness, the bend itself isn't representative of what proper spin stablizing fins usually are. Generally the fin as a whole is angled rather than the bottom portion of it being bent, In my uneducated opinion, having the drag coefficient spread out over a longer distance would create a more stable flight than what was done to these rounds. If you picture drag as a force being applied to a nose heavy object travelling at speed, the benefit to having a nose heavy object would be detrimented by the bend due to it being isolated at the far opposite side of the object. In effect, I think it would act more as a lever in a way, which would be amplified by any discrepancy in the bend itself. This could be as simple as the composition of the material (i.e. the crystalline structure of metal) creating a different curve in each bend, even if the bend itself was created in the same location, and at the same angle. Whether or not having the fins angled as a whole wouldn't create similar effects is beyond my ability to picture these things in my head though. I'm willing to bet that these rounds would be far more stable, but I have some doubts over whether or not they would be even better off than they were before modification.

I was thinking the same. 3-5° is all that's needed but I noticed something else as well. Our fletches are angled the entire length but for these they only bend the ends. They basically created two opposing forces and that's not good. It also would have been better to have the angle match the rotation of the rifling of the barrel because that induced a third opposing force that had to be overcome. Most archers know to match heliocoil with arrows rotation based on how the string is twisted, same would apply using rifling as the start point for determining angle.

It'll rip the target at alil closer range, depends on the range

That right, I'm just wondering if ~5 degree angle will be enough considering that is traveling at a supersonic speed and the fletching is probably behind the supersonic shockwave

@@JamesSmullins they werent shooting them out of a rifled barrel. He specifically mentions that at least once and in a on screen text he mentions that he meant for them to spin backward so no one could say he just used a rifled barrel.

@@metamorphicorder he said he bent them in the opposite direction of the rifling so people couldn't say they were cheating.

fins put drag at the rear of a projectile and cause the Center of Pressure (CoP) due to drag to be behind the Center of Gravity (CoG). This gives stability to the flight. The high angle of the bend on the fins MAY force the CoP slightly forward but not the CoG. This would mean less distance between the CoG and the CoP thus the projectile would be less stable. Another, more likely, cause would be a slight difference between the bend angle on the four fins. This would move the CoP away from the centerline of the projectile and give a wobble to the tail.

@@thomasburleson9575 yes, we are essentially saying the same thing. The high angle of the fins cause the wobble, and the varying fin angle will affect the overall accuracy. I didn't figure the CoP would effect much since all of the directional force is applied while the projectile is still saboted and in the barrel. I suppose that's why it's easier to leave the fins straight for minimum CoP instead of adding more weight to the front to move the CoG away from the CoP. Also if the fins were straight, but with a low angle, axial tilt along the whole fin as opposed to a sharp bend on the outer edge of the fin, the CoP would be more symmetrical and stable.

Awesome! Thank you!

I was going to mention that, but in other tests that wasn't the case.

For radiation protection

@@taofledermaus no science?

I was wrong and you were wrong Have a nice day

@@leifvejby8023 yeah it's not the first time and damn sure won't be the last hahaha

@@alexduke5402 Same here

If a diabolo is drag stabilized, then why do pretty much all airguns have rifling? Isnt that hollow skirt there for the same reason a miniball has a hollow skirt, to expand into the rifling? If you look at a used diabolo, you can see that the skirt has the most, sometimes the only rifling imprint.

Windbag. And also wrong in most of your comment.

That isn't quite true because we can and have shot SOLID diabolo slugs without a hollow cavity and have achieved stability- many times. The hollow is actually there to act like a Minie ball and cause the pellet to obturate and seal the gases.

@@taofledermaus I just tracked down and watched the video... that was interesting :) I would assume that it's because the rear cone moves the centre of pressure rearward as well. In your video it looked like a couple of the shots were oscilating a little as well as the one that wasn't stable, but the rearward shot definitely inverted, so the centre of drag was definitely in front of the centre of mass. On an airgun the skirt definitely obturates as well, but a good design as one that does as much as possible with the same features :) It's also worth noting that, in your other video, the slugs were fired out of a smoothbore, same as this one and they don't have fins, so the flight has to be drag stabilised in this case ;)

Helicoil or straight vanes that is the question.. _Personally i prefer a Helicoil 2 degree left hand twist with the Bow_

@@ifv2089 straight vains is better given the inconsistency in the projectile. A small imbalance will be more aparent with spin and can affect the projectile tragectory.

Yea its possible bud..With archery I find a LH twist good no idea shooting an Helicoil from a shotgun what makes this channel so awsome

Hm. There is going to be some variation between lathe-turned projectiles but likely not very much assuming a competent lathe operator, good tools and setup and so on. Cast bullets even less so- there may well be imperfections due to imperfections in the mold but they will be consistent from one to the next. The only other possible source of imbalance would be voids or inclusions inside the material. (That leaves out random dings and scratches due to mishandling because that's common to all projectiles. It also ignores fundamental aerodynamic instability due to the profile of the projectile- I doubt the bullets used here underwent any CAD modeling the way supersonic tank projectiles do in order to optimize their aerodynamics. What matters here is "does imparting spin improve the accuracy of these bullets *as they are*?) We know spin stabilization works with inhomogenous and not-necessarily perfectly balanced arrows *but* arrows have a greater length/diameter ratio and of course don't travel supersonic. A closer real-world analog would be supersonic saboted tank projectiles (fired from smoothbore cannon) which do have slightly canted fins; for the same reason, averaging out aerodynamic imbalances thus improving accuracy. In any case group size should be pretty consistent over a large number of projectiles, different for spun and unspun bullets of course but consistent for each. As we saw from this tiny sample size there is some small improvement but as Jeff said there should be way more testing to see how much improvement on average there can be. I have the general feeling there will be improvement- the question is, will there be enough to justify the extra effort of bending the fins? I suspect not, but you don't know unless you actually try it.

@@ifv2089 its defferent when you make things supersonic an arrow will behave diffren when you make it supersonic

I thought that weathercocking only happens because of the rocket's thrust.

@@666Blaine Technically yes, but an unpowered projectile can do it too depending on it's overall stability, damping, and profile. It eats a lot of energy though.

Interestingly, I have seen quite a few lawn darts that do spin when thrown, and they generally seem to fly pretty well. Not saying you are wrong, only that the spinning variant also works well.

until it isn't ... all must be tested to prove spin/stability

@@mikkohernborg5291 I came to say the same. My set also had spinning fins. They were not angled in anyway, but definitely free spinning.

Ship them over and we’ll try it out! She won’t miss them. 🤷‍♂️

Ha! I'd feel bad shooting them.

thanks!

thank you very much TATV