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New Pictures--Range Boost (Read 20470 times)
Matthias
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Re: New Pictures--Range Boost
Reply #15 - Jul 15th, 2004 at 1:06pm
 
I found this through the links when I was first reading this site, and was surprised that I couldn't find any discussion here...

...
Image linked from golfcross.com, copyright 2001 Conclusion Trust.

http://www.golfcross.com/frames/ball.html

Balls are pretty expensive, but combined with a silicone mold, you could make some pretty sweet "magnum" lead.

Matthias
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Re: New Pictures--Range Boost
Reply #16 - Jul 15th, 2004 at 1:22pm
 
has anyone slung these balls yet? I had an idea about golf ball ammo. What if you dilled into the golf ball and hollowed it out. Then filled it with lead or some other metal. You would have a prefectly cermetical ammo with the weight that you need.
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Re: New Pictures--Range Boost
Reply #17 - Jul 15th, 2004 at 2:11pm
 
Ever been hit by a regular golf ball, or seen what one does to a car roof or windshield? Do you need to add lead?
Justin
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Hobb
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Re: New Pictures--Range Boost
Reply #18 - Jul 15th, 2004 at 4:30pm
 
Lead would help -- not so much to increase the damage done as to get a better cast.  Assuming you can sling at the same speed, a heavier missile will go farther.  Golfing is different, since the golf-club's swing (at the same speed as with a lighter ball) would lose more energy to inertia when it hit the ball.  I'm sure there are physics types here who can explain it better than I can.
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mgreenfield
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Re: New Pictures--Range Boost
Reply #19 - Jul 15th, 2004 at 5:27pm
 
Golf ball dimples work because a well-hit ball has fast backspin on it.  With dimples "gripping" the air, backspin creates high pressure under the ball, and low pressure above the ball, so it actually flys like an airplane.

Of course anything BUT pure backspin produces hooks, slices, and other bad results.

nwmanitou says he puts backspin on his overhand shots, so could benefit from dimples on his glandes.  I put rifle-spin on my shots, so couldnt.

Golf balls at just over 1.5oz are a little light even for me. 

mgreenfield
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Matthias
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Re: New Pictures--Range Boost
Reply #20 - Jul 15th, 2004 at 5:44pm
 
Not just spin. Inducing a turbulent boundary layer can do some neat things when it comes to form drag. One of the reasons why "turbulators" are/were illegal in sailboat racing. They show up all over the place, once you get to looking.

This article is decent, and has nice pictures.

http://www.golfjoy.com/golf_physics/dynamics.asp

Even a rifle spin throw (we should all be so lucky) could benefit from dimples (or even better, come to think of it, a simple ridge/ring type turbulator - golf balls don't have a preferred orientation so you have to "waste" dimples... good idea mgreenfield!)

Time to make new glands? Who is going to try this?

Matthias



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David_T
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Re: New Pictures--Range Boost
Reply #21 - Jul 15th, 2004 at 6:19pm
 
Hey All,

A while back we had a long thread on dimple...in regard to Yurek and his atempt for a distance record.

I'm no physics guru but I remember Yurek and some others thinking that the dimple effect on leed glandes would be negated by the weight. They felt that the dimples were only beneficial for light weight projectiles like golf balls. It nay be worth a try anyways.
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Re: New Pictures--Range Boost
Reply #22 - Jul 15th, 2004 at 6:44pm
 
What is in a golf ball? I plan to make a golf ball filled with lead soon. Are they hollow or is there a little rubber ball in them ( this is what i think). Any information would be helpful.
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ZaQ
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Re: New Pictures--Range Boost
Reply #23 - Jul 15th, 2004 at 7:04pm
 
No Gun, they're not hollow inside.  I'm not sure what the center is but it's kinda hard.  I've seen people carve faces and things like that into a golf ball, so I'm sure you could hollow it out.  Might take a bit of work but I'm sure you could do it.
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mgreenfield
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Re: New Pictures--Range Boost
Reply #24 - Jul 15th, 2004 at 7:17pm
 
Great website on golfball flight dynamics posted by Matthias as reply #20!  

Maybe I get some of those elliptical golf balls, use them as mold patterns, then find a material that will net out at about 2.5oz instead of the golfball 1.56oz.   Between the dimples and a point-first pitch, I bet they'd fly a mile.

Yurek, how abt your 120-gram lead glandes with dimples?

mgreenfield
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Shaun09
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Re: New Pictures--Range Boost
Reply #25 - Jul 15th, 2004 at 7:23pm
 
Quote:
What is in a golf ball? I plan to make a golf ball filled with lead soon. Are they hollow or is there a little rubber ball in them ( this is what i think). Any information would be helpful.


All the ballsi've opened (drilled a couple of them to make a bola) had green rubber string type stuff over an inside layer of rubber, but those were really cheap balls. I have heard of newer ones with gas cores though.
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longwinger
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Re: New Pictures--Range Boost
Reply #26 - Jul 15th, 2004 at 7:28pm
 
Golf ball dimples work because a well-hit ball has fast backspin on it.  With dimples "gripping" the air, backspin creates high pressure under the ball, and low pressure above the ball, so it actually flys like an airplane.

Of course anything BUT pure backspin produces hooks, slices, and other bad results.

Hi MGreenfield,
I thought that a well hit golf ball did not spin, and the dimples on it helped form a boundry layer of air around it, giving it a more streamlined shape than just a round  smooth ball, a spinning ball will have more lift on one side, doesn't matter which, and not fly as true a line as one without spin and may not develope and benefit from a well formed boundry layer, as a non spinning ball.
So it seems to me the dimiples on a golf ball do not benefit the sling projectiles. Apparently the best approach to added distance would be the football shaped glandes, spinning on their axis and it that same direction. Although the ones you speak of with backspin may develope lift, makes sense.
But, I may be way off base here too!
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Matthias
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Re: New Pictures--Range Boost
Reply #27 - Jul 15th, 2004 at 7:51pm
 
Lead will certainly decrease the effect of boundary layer manipulation, but won't negate the benefits entirely.

Ok, pulled out the trusty spreadsheet and the thinking cap (no guarantee that I don't have it on inside-out, but you get what you pay for) No spin-lift (Magnus effect) included. These calculations are for spheres - an elliptical shape will show less effect still.

Using a 40 degree launch angle and 60m/s throw I get:

Max range (size / density irrelevant) ~367m

Smooth golf ball = 117m
Dimpled = 168m

so dimpling adds 45%, and air resistance knocks more than half off the total range.

Lead "golf ball" size smooth sphere = 296m
Lead dimpled sphere = 327m

In this case, dimpling only adds 10% and we are close to max range

A half diameter lead sphere gets 254m and 296m respectively

A double size lead sphere (if you could throw it) would take you to 350m and 356m

It should be noted that the scale of surface deformity needed to trip the boundary layer is pretty small, and a cast glans is probably half way there already. I still vote for a raised lip at the shoulder of the leading edge. That 5-10% could be pretty useful for something that doesn't cost anything.

Matthias

(Oh and new golf balls are pretty much all solid resin core - the "titanium" that people pay extra for is in the form of the worlds most common white pigment... drives me nuts...)
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longwinger
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Re: New Pictures--Range Boost
Reply #28 - Jul 16th, 2004 at 4:27am
 
I did a little research, and looks like a well hit golf ball does have alot of back spin to it, open mouth, insert foot.
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mgreenfield
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Re: New Pictures--Range Boost
Reply #29 - Jul 16th, 2004 at 8:37am
 
Matthias, ....as a given smooth-surfaced mass moves from spherical shape to eliptical, air drag is reduced.   This is good!

If that mass gets too elongated, it will be tough to handle in the sling pocket.    This is bad!

So, as you move the mass shape from spherical (with diameter/length ratio = 1.0), to eliptical with diameter/length ratio = 0.5, and further, where do diminishing returns in reduced drag start to show up??

Anything in your magic spread sheet let you tell us about this?    It would be very interesting to me who pitches eliptical glandes point first.

mgreenfield
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