This picture was submitted to me by a web visitor. He made the Ogre Catapult but increased the size by 1.5 which makes for a nice sized catapult.

Anyhoo, he and his son took this catapult out to the local park and it was a smashing success. Everybody had fun with it. All the other kids had fun firing it off and all the other dads had fun coming up with design improvements! Doesn't that just make for a great day!!!

I have complete plans and a tutorial on how to make a catapult very similar to this one. There are two different models. The first is called the Wyvern Catapult: Make a Tennis Ball Catapult and it uses the torsion of twisted rope. It is the more powerful of the two. The second is called the backyard Ogre and it is faster and easier to build but not as powerful. The Backyard Ogre

Launching Tennis balls with this catapult

Oh and his mechanism for releasing it with a long string is perfect. This is what you should do if you make a catapult like this. It is much safer and a lot more fun!!! Improvise yourself a little cup at the end of the throwing arm and you have the perfect tennis ball launcher. My thanks to Doug and his son for submitting this great picture :).

Here is what he has to say:

We did make it 1.5x original design specs., added a double bungee cord for increased tension power, used a 1x3 sized piece of lumber for the throwing arm, half of a 'wiffle type' ball for the tennis ball holder and also added the trigger pull.  The trigger pull is simply a metal door latch with a string tied to the top of it allowing it to pop off quickly with a quick pull of the string. 

All the impressed Dads that came over to try it out had their own ideas about design improvements.  Larger scale, compound bungee cords, flexing throw arm, etc.  It was lots of fun.

Leonardo DaVinci Catapult Kit

• Comes complete with all pieces pre-cut and ready to assemble
• Glue included
• Suitable for beginner model makers
• Easy to understand instructions