I'm trying to restring my Dipole up in a Pine (the tree has grown
about 10 ft, and the rope needs replacing) so I got out my trusty
Surgical tubing wrist rocket and a 1oz egg weight tied to my 15# test
fishing rod/reel (only using the bottom eye).

No matter how far I pulled back I got about 2/3s of the way up. Im
estimating that is about the 35 ft level.


Shouldn't a wrister go farther ???? need bigger weight ?

Suggestions.

R.Scott wrote:

No matter how far I pulled back I got about 2/3s of the way up. Im
estimating that is about the 35 ft level.


Shouldn't a wrister go farther ???? need bigger weight ?

Suggestions.

Stand on a ladder when you shoot?

New monofilament (more slippery than worn)?

New rubbers?

Skip the bottom eye on the pole and
feed direct from the reel?

Be sure you have a very solid wrist/arm
on the holding arm. If your hand/arm
gives while shooting, some of the
energy will be used in that wasted
hand movement.

I saw a "wrist rifle" that a guy built.
Normal WR attached to a wooden "stock"
with bazooka-like hand holds. The pouch
of the slingshot was held by a steel rod
in the "cocked" position. Just like rubber
band machine guns that kids might build.


Craig 'Lumpy' Lemke

www.n0eq.com

Lumpy wrote:
R.Scott wrote:

No matter how far I pulled back I got about 2/3s of the way up. Im
estimating that is about the 35 ft level.


Shouldn't a wrister go farther ???? need bigger weight ?

Suggestions.

Stand on a ladder when you shoot?

New monofilament (more slippery than worn)?

New rubbers?

Skip the bottom eye on the pole and
feed direct from the reel?

Be sure you have a very solid wrist/arm
on the holding arm. If your hand/arm
gives while shooting, some of the
energy will be used in that wasted
hand movement.

I saw a "wrist rifle" that a guy built.
Normal WR attached to a wooden "stock"
with bazooka-like hand holds. The pouch
of the slingshot was held by a steel rod
in the "cocked" position. Just like rubber
band machine guns that kids might build.


Craig 'Lumpy' Lemke

www.n0eq.com


If legal use a potato gun....

Dave WD9BDZ

On May 15, 11:46 am, "R.Scott" wrote:
I'm trying to restring my Dipole up in a Pine (the tree has grown
about 10 ft, and the rope needs replacing) so I got out my trusty
Surgical tubing wrist rocket and a 1oz egg weight tied to my 15# test
fishing rod/reel (only using the bottom eye).

No matter how far I pulled back I got about 2/3s of the way up. Im
estimating that is about the 35 ft level.

Shouldn't a wrister go farther ???? need bigger weight ?

Suggestions.

Sounds like a bigger weight would help.

wrote in message
...
On May 15, 11:46 am, "R.Scott" wrote:
I'm trying to restring my Dipole up in a Pine (the tree has grown
about 10 ft, and the rope needs replacing) so I got out my trusty
Surgical tubing wrist rocket and a 1oz egg weight tied to my 15# test
fishing rod/reel (only using the bottom eye).

No matter how far I pulled back I got about 2/3s of the way up. Im
estimating that is about the 35 ft level.

Shouldn't a wrister go farther ???? need bigger weight ?

Suggestions.

Sounds like a bigger weight would help.

depends... shoot the weight without the fish line and see how far it goes,
that is the max you can get... if that's not enough try new tubes, those
things do age and lose stretch... or longer tubes. for more height without
the line try less weight and see if that gets where you need.

then add the fishing line and see if that drags it down too much... if it
does you need less drag or lighter line. either take the line out of the
reel and let it spool free or unroll it on a smooth surface so it doesn't
have to spin the roll.

wrote:
On May 15, 11:46 am, "R.Scott" wrote:

I'm trying to restring my Dipole up in a Pine (the tree has grown
about 10 ft, and the rope needs replacing) so I got out my trusty
Surgical tubing wrist rocket and a 1oz egg weight tied to my 15# test
fishing rod/reel (only using the bottom eye).

No matter how far I pulled back I got about 2/3s of the way up. Im
estimating that is about the 35 ft level.

Shouldn't a wrister go farther ???? need bigger weight ?

Suggestions.


Sounds like a bigger weight would help.

An interesting question, and a fairly good answer within limits. I used
to do a lot of this sort of thing in the special effects industry (why
yes, you CAN launch a refrigerator with bungee cords).

Here are the physics things to think about.

The amount of energy you can put into the projectile is determined by:
a) How far you pull back
b) How hard you had to pull (i.e. spring constant of the tubes)

To a first order, Q = 1/2 * Peak Force * distance pulled back

That energy gets transferred to the projectile as kinetic energy.

To a first order, Q = 1/2 * Mass * V^2

Then, the energy gets converted back to potential energy (height) and
lost through air drag and pulling the line out. For slow speeds and
small things, the line drag is probably dominant.

By the way, if the pull is about 10 lbs and you pulled back 18", with no
air or line drag, a one ounce projectile will go to about 36 meters (120 ft)

A little bit of line drag makes a huge difference. a one ounce drag,
essentially doubles the weight of your projectile. For the example,
that would change your max height to about 19m (60ft)

If you had a 2 ounce projectile, on the other hand...with no drag, you
get to 19m, but the 1 ounce drag only brings you back to 12.4 m (40ft)


Air drag is a smaller order effect.

force in lbs = area in square feet * v(mi/hr)^2/391.. Your one ounce
weight is moving about 60 mi/hr at launch (9 lb/sf), but is less than a
square inch, so it's about an ounce of drag, but it drops off as the
square, so as the projectile slows, the drag drops off..

A heavier projectile goes slower, so that helps on the airdrag too.

Going back to 1 oz, no line drag, but counting air drag for 1" diameter,
27m or so height (about 2 seconds after launch, as a cross check)
1 oz, 1 oz line drag, air drag, 15.5 m
2 oz, no line, air drag, 1" diam, 18.8 m
2 oz, 1 oz line, air drag, 11.6 m


So this should give you a feel for the relative effects of line drag and
air drag and projectile mass. I did the calculations with a simple
spreadsheet in Excel that numerically integrates the physics equations
with very short time steps.

On May 15, 12:46*pm, "R.Scott" wrote:
I'm trying to restring my Dipole up in a Pine (the tree has grown
about 10 ft, and the rope needs replacing) so I got out my trusty
Surgical tubing wrist rocket and a 1oz egg weight tied to my 15# test
fishing rod/reel (only using the bottom eye).

No matter how far I pulled back I got about 2/3s of the way up. *Im
estimating that is about the 35 ft level.

Shouldn't a wrister go farther ???? * need bigger weight ?

How high are you trying to go? With everything in my favor (wind,
etc.) I could get over about a 50 foot branch with a wrist-slingshot
and a 1oz weight. And I think I was standing on a 12 foot ladder to do
it, and this was a "best ever" shot.

Having the line catch on anything - grass, leaves, etc., is a major
downer. If there's no brush on the ground you might get a little more
height by spooling some line out in front of you.

Others here regularly claim being able to get 100+ feet with a
slingshot. I never said out loud that they're exaggerating, but I know
I could just barely do half that. To get to 100feet I went straight to
a tennis ball cannon.

Tim.

On Fri, 16 May 2008 08:27:44 -0700 (PDT), Tim Shoppa
wrote:

On May 15, 12:46*pm, "R.Scott" wrote:
SNIP
No matter how far I pulled back I got about 2/3s of the way up. *Im
estimating that is about the 35 ft level.

Shouldn't a wrister go farther ???? * need bigger weight ?

How high are you trying to go? With everything in my favor (wind,
etc.) I could get over about a 50 foot branch with a wrist-slingshot
and a 1oz weight. And I think I was standing on a 12 foot ladder to do
it, and this was a "best ever" shot.

SNIP
Tim.

I couldn't get 50 feet with mine. I figured the line was too old, but
I realized the sling was way overrated. I can do much, much better
with a rod and reel. My favorite tool was a Bear 76er Bow and Arrow
with a short string. It had a 50 lb pull and I could place an arrow
with a screwdriver handle on the tip where ever I wanted it.

The best was a converted shotgun. I took a shotgun shell and took out
the shot, folded the plastic outer shell over the inner shell and
stuck a wood dowel into it. On the far end of the dowel was a
screwdriver with an eye hook onto which I tied a string. It cleared a
100 foot tree with room to spare, but I was afraid of the possibility
of damaging the gun itself so I only tried this once.

Buck
N4PGW

--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."

On May 16, 12:01*pm, Buck wrote:
The best was a converted shotgun. *I took a shotgun shell and took out
the shot, folded the plastic outer shell over the inner shell and
stuck a wood dowel into it. *On the far end of the dowel was a
screwdriver with an eye hook onto which I tied a string. *It cleared a
100 foot tree with room to spare, but I was afraid of the possibility
of damaging the gun itself so I only tried this once. *

Wow, a shotgun. I wouldn't be so much scared of damaging the gun, but
instead of the gun blowing up in my face!

The tennis ball cannon I use is very very similar to the CSV19 at
http://www.antennalaunchers.com/ and I am very very happy with it.
It's not so much a "point above a crotch in the tree and hope the ball
goes through" but "just shoot the ball and line over the tree".

Tim.

Jim's calculations have confirmed something I've consistently experienced:
my homebrew EZ-Hang has never really lived up to my expectations, or should
I say the expectations that others have set for the performance of the
thing. (For the record, my homebrew device is an exact copy of the famous
EZ-Hang.)

For the past three Field Days, which is when I've used the thing, the
maximum height I've seemed to attain is around 50 feet-- right in the
ballpark for a 1 oz. weight with line and air drags. No matter what I've
tried, that's the limit of height for the parameters of my situation.

Thanks, Jim.

Al W6LX








"Jim Lux" wrote in message
...
wrote:
On May 15, 11:46 am, "R.Scott" wrote:

I'm trying to restring my Dipole up in a Pine (the tree has grown
about 10 ft, and the rope needs replacing) so I got out my trusty
Surgical tubing wrist rocket and a 1oz egg weight tied to my 15# test
fishing rod/reel (only using the bottom eye).

No matter how far I pulled back I got about 2/3s of the way up. Im
estimating that is about the 35 ft level.

Shouldn't a wrister go farther ???? need bigger weight ?

Suggestions.


Sounds like a bigger weight would help.

An interesting question, and a fairly good answer within limits. I used
to do a lot of this sort of thing in the special effects industry (why
yes, you CAN launch a refrigerator with bungee cords).

Here are the physics things to think about.

The amount of energy you can put into the projectile is determined by:
a) How far you pull back
b) How hard you had to pull (i.e. spring constant of the tubes)

To a first order, Q = 1/2 * Peak Force * distance pulled back

That energy gets transferred to the projectile as kinetic energy.

To a first order, Q = 1/2 * Mass * V^2

Then, the energy gets converted back to potential energy (height) and lost
through air drag and pulling the line out. For slow speeds and small
things, the line drag is probably dominant.

By the way, if the pull is about 10 lbs and you pulled back 18", with no
air or line drag, a one ounce projectile will go to about 36 meters (120
ft)

A little bit of line drag makes a huge difference. a one ounce drag,
essentially doubles the weight of your projectile. For the example, that
would change your max height to about 19m (60ft)

If you had a 2 ounce projectile, on the other hand...with no drag, you get
to 19m, but the 1 ounce drag only brings you back to 12.4 m (40ft)


Air drag is a smaller order effect.

force in lbs = area in square feet * v(mi/hr)^2/391.. Your one ounce
weight is moving about 60 mi/hr at launch (9 lb/sf), but is less than a
square inch, so it's about an ounce of drag, but it drops off as the
square, so as the projectile slows, the drag drops off..

A heavier projectile goes slower, so that helps on the airdrag too.

Going back to 1 oz, no line drag, but counting air drag for 1" diameter,
27m or so height (about 2 seconds after launch, as a cross check)
1 oz, 1 oz line drag, air drag, 15.5 m
2 oz, no line, air drag, 1" diam, 18.8 m
2 oz, 1 oz line, air drag, 11.6 m


So this should give you a feel for the relative effects of line drag and
air drag and projectile mass. I did the calculations with a simple
spreadsheet in Excel that numerically integrates the physics equations
with very short time steps.