Fin stabilized smooth bore sabot slug?

[-v-]

Erm, so what about the fins on a APDS of the 120mm variety? It seems to me those help stabilize the projectile so it can consistently hit its target.

Although, I agree, it seems that the shock-wave flowing over the nose of the slug would make the fins darn near useless since they would be getting little/no airflow.

Brings up then the whole question of super-sonic aircraft and how they maintain lift and control at Mach 1+?

Remo-99: DU is pyrophoric. When the DU rod impacts, surface layers are sloughed off into dust, the dust will (because of its outer valience shell and the octet rule) spontaneously react with the O2 in the air to form UO2 (uranium Oxide) and a bit of heat.

A similar thing happens when you machine uranium. The shavings have to immediately go into a mineral oil filled bucket or else they will begin to spontaneously combust from contact with the air. The larger and thicker the sample, the less likely the Uranium will combust. Shavings burn easily, slabs not so much.

Think of Uranium like a more reactive magnesium.

 

[Owen]

the difference with the tank gun is that the fins are larger than the body of the projectile, so the correction is constant. With the sub-caliber fins on that slug, it's gonna wobble quite a bit = bad

 

[rcmodel]

My impression is, the 120mm Sabot is very slim and about two foot long, and a jet fighter is way longer then that with an area-rule fuselage design.

I think there is some laminar flow air flow way back where the fins are on those.

On a short-coupled slug, not so much.

rc

 

[RandKL]

Oblique leading and trailing edges? No. Each fin is tapered on both sides to make them aerodynamic.

Wrong. They're sliced on the fronts on ONE side and on the backs on the opposite side to provide spin as the manufacturer stated when those were hot on the market several years back. If you look a bit, you'll probably find the original ads on the web somewhere. Heck, you can look at the pics above and see that.

rich

 

[mlkAvEAT]

Sorry for bringing an old post back to life but I just found it and I wanted to give my input and correct a few things. My intent isn't to single out rcmodel, just to fix some statements.

Cough all you want to, but the "oblique fins" on a rifled slug do little or nothing to impart spin to the slug.

The super-sonic shock-wave over the nose of the slug leaves them operating in what amounts to an air burble.
There is no laminer air flow over the "rifling" fins to make them do anything much at all.

They are well past 50 yards before they go sub-sonic and even begin to get a little laminar flow over the fins.

The shock wave over the front of this projectile would be an oblique shock wave which would indeed leave the entire projectile in a "bubble", but not a low pressure bubble. In contrast the pressure after the shock wave would be much much higher than the pressure of the air in front of it.

I still contend that there is no laminar air flow over the fins on a super-sonic slug with rifling or fins. The shockwave coming off the nose of the slug leaves a semi-vacuum in its wake until it goes sub-sonic at extended range.

The finned slug may have an airfoil shape, but without laminar air flow over them, they are stalled out, and provide no spin.

You are very correct, there is absolutely no laminar flow over the projectile, or hardly any object traveling past Mach 1. Laminar flow is very hard to accomplish even in subsonic conditions, I would venture to say that even high performance sailplanes struggle to keep the flow of air laminar over the entire chord of a wing. (Little things like a break between pieces of skin on a wing or a bug splat are enough to stop air from being laminar.)

The bit mentioned about the semi vacuum is entirely wrong. Like I stated before, the air pressure increases many times so the air around the projectile would be much thicker. The air does however slow down a lot, so while air pressure around the projectile is much higher the air velocity is much lower.

I can't comment too well on the part about the fins being stalled out, though I really doubt it.

Erm, so what about the fins on a APDS of the 120mm variety? It seems to me those help stabilize the projectile so it can consistently hit its target.

Although, I agree, it seems that the shock-wave flowing over the nose of the slug would make the fins darn near useless since they would be getting little/no airflow.

Brings up then the whole question of super-sonic aircraft and how they maintain lift and control at Mach 1+?

We could have a long talk about that But you should be able to get the gist from the above. At Mach 1+ air around the plane slows down, pressure goes up, just makes a new set of design criteria.

My impression is, the 120mm Sabot is very slim and about two foot long, and a jet fighter is way longer then that with an area-rule fuselage design.

I think there is some laminar flow air flow way back where the fins are on those.

On a short-coupled slug, not so much.

There is probably no laminar flow on the 120 mm projectile, even if the fins are far enough out from the body to escape the shock cone created at the nose the leading edge of the fins would make their own shock waves. I won't say its impossible to have laminar flow past Mach 1.

These fins would indeed do something, but if that something is enough to make the round effective I don't know.