# Ideal Ball weight to get the maximum range from a ball launcher?

#### cosmo88

Hello guys,

i am building a ball launcher to proper a line of baits into the sea, the line has 25 baits, each bait weights 30 grams (about 1oz), ideal shooting degree seems to be 45 to get maximum range, What i would like to figure out is the ideal weight of the ball to achieve the greatest possible distance.

Here is an illustration of what I want to do:

#### Woody

The weight of the ball is less important than the force at which you propel it.

#### cosmo88

Hi woody, thank you for your reply, it's true that force is more important, but since the catapult force is limited, i need to get the most out of the available force, every extra distance that I gain is important, i am a newbie when it comes to physics, but it seems to me that there should be an ideal weight, or a way to calculate it, too small and maybe it will be slowed easily by air and the line of bait it is pulling, then if it's too big it won't go far in the first place, so some weight in the middle, how to calculate that weight ?

Many thanks

#### oz93666

This is not easy ... biggest unknown is the pull back on the ball ... how smoothly the line plays out ...

750 gms of bait ..... I would think you need about the same mass in the ball ...

Elastic catapult is not the option I would go for , difficult to get enough energy stored in the elastic ....

An easy way must be to swing the ball around your head to build up momentum , then fling it like a hammer thrower in the Olympics

High tech I would get an electric car tyre inflator and a battery... using plastic water piping of various sizes make a reservoir tank to hold the air at 100psi ...an electric air switch allows the gas to be dumped into a long 2" tube firing the ball . This will go VERY far!
With this method there is the possibility of the line fouling the ball in the barrel and jamming it ...One option is the ball is free , A nylon net bag is placed over the end of the gun , when the ball exits it is captured in the bag , pull strings close the bag which is attached to the line and baits. It need not be a ball , but a slug , a 3" long piece of plastic pipe that tightly slides in the barrel , filled with concrete for weight ... this would be less likely to foul the line
Another way is not to use compressed air , but electrically spark ignited propane air mix or similar , this mix will be put in the reservoir tank , plastic pipe will hold the pressure of the small explosion.

Still better would be the missile is a one foot length of pipe ... the front 4" filled with concrete . the bait and line is jammed into the remaining 8" of the missile . the end of line is tied inside the back end of the barrel

Last edited:
benit13

#### Woody

The catapult will impart a (more or less) fixed amount of energy
You want to use this energy in the most efficient manner.

The important parameter is Momentum which is Mass (Weight) multiplied by Velocity (Speed)
However the higher the mass, the lower the velocity that will be imparted by the catapult.
The two effects will tend to balance each other.

The main consequence of ball size on distance travelled will be the drag of the air.
A denser ball (eg lead verses rubber) will be smaller (for the same weight) and will have less drag.
Perhaps consider using an ovoid "ball" to reduce drag.

Do you want the Ball to float?

#### cosmo88

oz93666 thx, I thought about the pressurized air cannon, some people use it as a one bait launcher, it can send 1 bait 200 yards as demonstrated in many youtube videos, but it would take a big and dangerous air cannon that sends 25 baits and a ball the size of a soccer ball into the sea, as for the missile idea, i also thought about that, was evening checking some of those sugar missiles on youtube, but it's not practical,

Woody, yes i need the ball to float to hold the baits in the desired water depth,

Another question if someone knows the answer, does the shape of the object also matter when trying to achieve maximum distance? for example will a 1lbs arrow achieve a longer distance than a 1lbs ball ?

i will be posting photos when i am done making the device.

thanks.

#### Woody

Aerodynamic drag will have a big influence of how far it will travel.
Streamlining can certainly help.
Which is why I suggested an ovoid (rather than round) ball
(like an American Football, or a Rugby Football)

Another consideration is the lift a non-spherical ball could supply.
You currently require a 45 degree angle to shoot farthest,
this is because the amount of drag in the up/down direction matches the drag in the forward/aft direction.
But that means a lot of energy is going toward pushing the ball up, rather than out.
If you use a shape with less drag in the fore/aft direction than in the up/down direction
then you should start to see the optimum firing angle becoming less steep
and the overall distance fired becoming greater.

#### oz93666

A better solution might be to get a cheap RC drone , it could toe the line out and place it just where you want ...it wouldn't have to lift the full weight of baits they would be floating in the water . The drone would need to be adapted to drop the line on command.