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I used 2x4's on my catapult. But I'd like to make it beefier with more throwing power. The body is pressure treated wood, and eventually I'd like to add more garage springs or other counter force measures. But I need a better arm.

What kind of wood should be used in constructing a catapult arm?

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  • Could you add more 2x4's to beef it up? – Jason C Feb 26 '16 at 4:52
  • What's your budget? – Andres Kievsky Feb 26 '16 at 5:55
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    FFR, you should be more careful with your wording, esp. in titles — can be used rather than should. Should is like asking what's best, which will tend to garner opinion-based responses. While there are a few woods commonly used for this sort of thing in reality there are probably a dozen species that might be used, any perhaps a multitude of laminated options as well. – Graphus Feb 26 '16 at 10:56
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    This answer is slightly off target but.... if what you are for is more distance per pound consider a change of design to a trebuchet. I made one with my son back in his school days and those babies can really throw a stone! ![Trebuchet image from sciencebuddies.com](i.stack.imgur.com/bRRmI.png) – Ashlar Feb 26 '16 at 12:14
  • Second trebuchet. They're much, much more common among the SCA families I know, and for good reasons. They're also safer, in that there's no risk of a spring failing unexpectedly and throwing pieces of itself at high velocity. – keshlam Feb 26 '16 at 16:12
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I assume your question is not so much size (you mention 2x4, but not what type you are using).

Try ash or hickory for their spring and flexibility. Either should give you some extra kick beyond what you get with your counterweights or springs. @Graphus points out that it "Might be worth specifying hickory sapwood here, as the heartwood is much less springy. This is why it's specifically avoided in quality axe, pick and sledge handles — they should be uniformly pale, no reddish heartwood."

Clear, straight grain is a must no matter what wood you use.

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  • Might be worth specifying hickory sapwood here, as the heartwood is much less springy. This is why it's specifically avoided in quality axe, pick and sledge handles — they should be uniformly pale, no reddish heartwood. – Graphus Feb 26 '16 at 10:59
  • I wonder if you could find a large enough cut of English Yew...although I can only imagine the difficulties in dealing with that. Maybe something laminated would be even better (I've got bow technology in mind here) – BrownRedHawk Feb 26 '16 at 13:02
  • @graphus I'll incorporate your comment. One of the few times when sapwood is the desired component. – Ast Pace Feb 26 '16 at 17:09
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I've found a few sources mentioning that Douglas Fir is good for trebuchet arms. Presumably it'd be just as good for a catapult.

http://www.shubs.net/howard/scotland/UrquhartCastle.html - There's quite a large trebuchet here which has been built (frame and throwing arm) out of Douglas Fir for example.

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  • Douglas fir would certainly be less expensive and easier to find than would be the case with hardwoods. – Ast Pace Feb 26 '16 at 17:11

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