Disc Shape and Physics

[AdamCaudle]

I have a few questions regarding disc shape and it's affects on the physics of the flight.

What things contribute to HSS and LSS?
Why do concave wings, and beads add overstability to a disc's flight?

 

[Oregon_Nole]

Just from the disc selection that I have, it seems that:

For HSS:

Flatter <=========> Domey = Overstable <=======> Understable

 

[Jacob]

Just from the disc selection that I have, it seems that:

For HSS:

Flatter <=========> Domey = Overstable <=======> Understable

I don't know about this comparison. I'm looking at a Whippet and a Kite and they are both pretty domey.

 

[BrotherDave]

Rameka's thesis
My unanswered question

colodiscgolfer is pretty knowledgeable about this stuff too but he doesn't get on here much

There's no correlation b/w domey and stability. If a disc is too flat it won't glide for damn though.

 

[toothyfish]

https://www.dgcoursereview.com/dgr/resources/articles/discqualities.shtml

 

[Marmoset]

Just from the disc selection that I have, it seems that:

For HSS:

Flatter <=========> Domey = Overstable <=======> Understable

I agree with this statement for discs ranging from putters to the slower high speed drivers. But in the highest speed drivers the opposite seems to be true... domey= overstable, flatter= less overstable.

 

[Marmoset]

I don't know about this comparison. I'm looking at a Whippet and a Kite and they are both pretty domey.

You can't compare between different molds. There are too many variables involved. But within the same mold this usually holds up. A domey Firebird is not as overstable as a flat Firebird.

There are exceptions, though. Like I said in my previous post, alot of the faster drivers are more overstable if they are domier. Flat Destroyers are less overstable than domies. There are some other discs like this and not all are fast drivers.

There are too many variables involved to make statements like "all flat discs are overstable".

 

[Marmoset]

Off the top of my head, here are a couple generalities I've found:
♠ The more weight in the rim, the harder the disc will torque-off (fade) at the end of its flight.
♠ The wider the diameter, the more it glides.
♠ Within the same mold, higher PLH= more overstable
♠ Within the same mold, softer discs= more sensitive
♠ To a certain extent, blunter noses= more overstable

 

[NothinButChing]

physics is cool

 

[AdamCaudle]

I've seen the term PLH a lot, and I'm sure it's pretty obvious, but what does it mean?

 

[Marmoset]

PLH= parting line height
Basically, its the thin incidental line of flashing where the lower peice of the mold (the wing section) meets the upper peice of the mold (the flight plate section).

 

[toothyfish]

I've seen the term PLH a lot, and I'm sure it's pretty obvious, but what does it mean?

Parting Line Height - where the two halves of the mold meet, it leaves a fine little edge.

 

[AdamCaudle]

Parting Line Height - where the two halves of the mold meet, it leaves a fine little edge.

Ahh thanks.

 

[bikinjack]

Parting Line Height - where the two halves of the mold meet, it leaves a fine little edge.

Actually, and I may be wrong about this, but I thought parting line height was actually the line where air diverged around the disc. Air above the PL goes over the top, and air below goes under the disc. This is going to be really close to and in some cases may be the same as the flashing where the two halves of the mold meet, but it is not necessarily the same thing.

 

[Malaclypse]

Actually, and I may be wrong about this, but I thought parting line height was actually the line where air diverged around the disc. Air above the PL goes over the top, and air below goes under the disc. This is going to be really close to and in some cases may be the same as the flashing where the two halves of the mold meet, but it is not necessarily the same thing.

I think parting line is terminology used to describe where the molds meet. But I also think it would be the same place where the air diverges since it is at the edge where the plastic changes direction. If the parting line wasn't at the very edge, I don't think the plastic would come out of the mold properly.

However, I could just be talking out my butt.

 

[milow369]

I think it has to do with the surface area of the disc that makes contact with air when flying, especially the dome or lack of dome and the rim of the disc. Beads can also be added to give additional surface area of the disc to catch the air/fight against the air. The sharpness or bluntness of the disc edge is also something that can be used in the design that can affect stabillity.

A firebird has a fairly concave lip, and a pretty blunt edge. It's extremely stable - lots of plastic to grab the air. A TL on the other hand has a pretty smooth lip, is pretty flat, and has a sharp edge. This allows the disc to fly further in the air before it is affected and fades out.

A firebird has to really be snapped hard to keep it straight or to turn it over. The high rpms and high forward speed of the disc flying through the air fight the tendency for the disc to fade out. The harder the snap/faster the throw the longer the disc will fly straight before fading out.

I wonder out loud if a TL or a beat Teebird can be made more stable by sanding down the lead edge of the disc so it is more blunt, like that of a Firebird. That might be one way to increase the stability of a disc that is worn. Probably easy to test. Not sure it falls under the category of "light sanding" but would be interested to know if it would work. As far as I know there's no legal way to make a disc more stable than the day you pull it off the shelf.

Other things that affect flight/stability are diameter of disc, weight (although I think weight is more of something that slows down the thrower's arm speed) Thickness of rim, width of rim, any that I am missing.

 

[ChainMan]

I think parting line is terminology used to describe where the molds meet. But I also think it would be the same place where the air diverges since it is at the edge where the plastic changes direction. If the parting line wasn't at the very edge, I don't think the plastic would come out of the mold properly.

However, I could just be talking out my butt.

I believe you are correct, "parting line" is a term used by mold makers. In a disc it is usually the point at which you would measure the discs diameter. Because otherwise, as you mentioned, the plastic would not release properly from the mold. (I do have a wee bit of professional experience with molds and there are exceptions such as when silicone rubber molds are used that can be pealed away from the part. )

 

[Marmoset]

I wonder out loud if a [random disc] can be made more stable by sanding down the lead edge of the disc so it is more blunt...

That is my next experiment.
The catch is that you are removing material from the perimeter only and therefore affecting the weight distribution. The more weight you have in the middle of the disc the less overstable it is, which, to some extent, negates the blunting. How much does it negate? IDK, but I am planning on finding out.

 

[Marmoset]

A more effective method for overstabilizing would be to blunt the nose by adding material but I'm not sur ehow I would do that. My plastic welding skills aren't that great.

 

[nitegolfer]

Boundary Layer

What happens when you throw a disc upside down? No lift. So the idea behind an edge design is to create more air passing under the disc compared to the amount of air passing over the disc.

http://discgolfer.ning.com/forum/topics/1809917:Topic:412