Bolt Length

I need a bolt length for my crossbow. It has a length of 11 1/2" from prod to nut, want to make sure I get the right length and weight. The crossbow will have 120# draw on it.
Euell

You can buy 31-32 inch cedar arrow shaft, cut it in half for 15-16 inch bolts.  Use with 125 grain heads and 3 inch feathers for a reasonable target bolt. 38-40 cm.
Medieval bolts vary in length, but the average seems to be in this range: 14-16 inches.  I've seen outliers as short as 12 inches (305 mm) and as long as 18 inches.  Some modern shooters go for substantially longer bolts... over 20 inches. Longer bolts will be more stable, but also a bit more fragile, and wil be heavier, with a bit more surface area for air friction to act on, will lose velocity quicker at longer ranges.  In short, there's no definitive answer.  Geezer.

Greetings,
  Its been awhile since I have posted anything on the forum. Geezer is right. No definitive answer on bolt length. I personally like to use bodkin tips on my bolts, therefore I allow the tip just beyond the tiller nose. That way the bolts rest better in the groove ( more less parallel with the groove). That just my opinion though. here is a couple of pics



 jds6

jds6 thanks for the pic. Your bolts look about 1/2" to 3/8 what size are they and what is your grove depth

Euell,
 The bolts pictured are 3/8" and are 15 3/4" long. they have a 220gr bodkin tip with 4" fletching. The bolt groove depends on the diameter of the bolt and the diameter of the string. You want the string to be in the center of the bolt when the bolt is placed in its groove. 
jds6

The bow that I built over 40 years ago,I made the bolts out of hardware store 3/8ths. Ramin dowel(ramin is an African hardwood of the mahogany family I think)with homemade 3ins plastic flights and homemade target type points.I experimented with bolt length and found 10ins. worked well for me.I used homemade aperture sights and could place 3 out of 5 bolts in a 2ins. circle at 50 yds.This is an observation rather than a recommendation.Length doesn't seem to affect accuracy,nowadays everyone seems to use longer bolts than I did.Length is obviously important,but can be adjusted to suit you,your bow,and what you want your bow to do without affecting accuracy. 
                                                           Hermit.

You're right, Hermit, bolt length isn't terribly important.  When I started building crossbows for sale, I made my bolts from 32 inch arrow-shaft and cut them into 10.5 inch (or thereabouts) lengths.  In fact they flew straight and fast, but I discovered short bolts often go so deep into your target that the feathers get damaged, or in the case of hay-bales (I don't recommend them but some folks use them anyway) the bolts can disappear entirely into the bales (@ 15 inches wide) so eventually I started making them out of half-arrow shafts.  That mostly fixed the problem of bolts going so deep that they stripped off the feathers.  So from my point of view, the length I settled on is mostly practical and financial.  Shafts over 16 inch mean I can only make one bolt per arrow-shaft (or I make some real-short ones and an even number of real long ones) In "short" making bolts longer than 16 inches raises the cost of each bolt by a bit over a dollar.  When you make hundreds of bolts a year, that gets expensive in a hurry.  Of course if you're just making bolts for your own use, the economics work out differently
Geezer

PS: concerning shafts made of commercially available dowel rod, I've done that too. You have to do a bit of searching to find really straight, round dowel.  Most of the big-box hardware stores in the US sell crap for dowel, but some of the little 'Ace' hardware stores stock a better item.  Even so, only @ 25 percent of the dowels in the bin are going to be straight enough to make bolts... and of course one must eliminate shafts with the grain running out one side, even if they ARE straight.  So with some searching, you can find good dowel for crossbow bolts from your local hardware store, but as mentioned above, I'm not making a few dozen bolts for my own use, but hundreds to supply to customers all over.  At a certain point, I discovered I couldn't find enough straight dowel in local shops to meet my needs, so I went back to more expensive arrow shaft.  
In fact, the same applies to found lumber for making crossbow stocks. If you look around, you can find lovely timber from crates or old barns that will make a wonderful stock for your new project, but often that timber has hidden nails or weird twists that require a lot of effort to prepare the wood for making a stock. Though I had a couple of dandy sources for 'found' lumber, I ended up spending more time preparing the timber-planing, searching for nails/studs/staples, that it turned out cheaper for production work to simply buy good hardwood timber from my local lumber yard (yeah, we've got a good one here in Austin that stocks lovely hardwoods) Once again, there's a difference between making a few beautiful pieces, and being in the business... though in fact my business is very modest. Geezer.

Thanks guys for the info. For the diameter it will be 3/8, the length 10" or 10 1/2".
Euell

There are dowel suppliers that can supply rather long dowels in a variety of woods to satisfy weight concerns. I've bought from these guys :http://store.cincinnatidowel.com/dowels  Others exist. You can get Hickory dowels from Black Powder gun merchants in various diameters, example : http://www.dixiegunworks.com/product_info.php?products_id=1238 , there are many more. Some suppliers use only split lumber to ensure no grain runout.  The Internet is wonderful for finding odd things.

There are indeed dowel suppliers online, from whom you can buy good quality stuff, but of course the problem is, you get what they send you... by and large round and well made, but not necessarily straight.  That's why i used to buy from local hardware stores. I dropped in every couple of weeks to go through their dowel bins, searching out the good stuff.  Geezer

Thanks Geezer and every body who answered my post. Got a lot of good replies.
Euell

One last comment Euell,nobody has mentioned making your own dowels.Go to you tube,and search 'homemade wooden dowel' there are several pages of Vids. on how to make them using simple tools,the most common being an electric drill.Timewise,by the time you have searched the net,found what you want,sent away for it,waited for it to come by post,you could probably have made a dowel maker,and a lifetime supply of dowels..............just a thought.......
                                                                                            Hermit.

Thanks hermit I'll take look into you tube about the dowel making, and I'm going to go to my local hardware and look for some straight 3/8 dowels.
Euell

Say Hermit I had done some searching and found a tool from Lee Valley & Veritas its called veritas dowel and tenon cutter, take a look at it. for dowel making.
Euell