I have a lot of questions about crossbow bolts here...

Question

I made a really good crossbow by myself. It works pretty good, but the bolts I made spin (horizontally) really fast. I want to add fins to make them go straight, but I don't know how. They're made out of really good plastic . They are about 1 cm in diameter.

Q1)How do I add fins, and what should I use for them?How many? 3 or 4?

Q2)As for all crossbows, if the bolt has fins that are at equal distances (like a Y instead of a T), wouldn't that make the bolt pop out of the arrow path (slit where the bolt goes) a little bit? Is that OK if they do?

Q3)The arrow path on my homemade crossbow is 14" long ( with my resources in my home, thats as far as I could pull the string). The bolts I made now are 5 inches, and weigh about as much as 3 pencils.(I don't have a scale, so I just held a bolt in one hand and 3 pencils in the other and they seemed really close). Now, they go about 25-30 feet (again, that's just a guess). With all that info above, how long should the bolts be? Does the length of the bolts make a difference? If so, what difference does it make?(like, do longer ones go straighter or something?)

Thanks ahead of time!

Answer 1

Most crossbows I've seen has a slit under the arrow path to allow for the vane to slip in.  Crossbow bolts usually have 4 vanes on them.  When loaded they look like a cross or a plus sign.  I've also seen 3 vanes where the index/c**k vane points downward like a Y.

Longer bolt won't help with speed, if that's what you're after.  The longer the bolt the weaker the dynamic spine will be.  This will cause problems when the spine flexes too much and springs the bolt away from the path.  In target competitions, the bolts people use are actually about the size of pencils.  I've shot with this gentleman once, he had a field quiver holding his bolts, all 4 of them and a pencil in a separate pouch.  He had the quiver resting on his butt, and as he reached back for his bolt one time, his hand found the pencil instead and loaded the pencil on his bow.  That would've been funny if he had shot it.  He of course realized what he had done a second after he put the thing on the bow.

Oh to put the vanes on,  well most vanes are made of some sort of plastic, some are made of rubber.  You just glue them on the shaft and make sure once done you put a dab of glue to the front and the rear of the vane.