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Manchu Arrow Project (part 1)

Silent Thunder Ordnance

 Rough poplar Manchu (1/2") shafting in the background. "Normal" sized rough cedar shafting in front. 

Rough poplar Manchu (1/2") shafting in the background. "Normal" sized rough cedar shafting in front. 

Perhaps this could be more accurately titled "heavy war arrow project," but I digress. This all was inspired by a for sale post from a gentleman I saw a while ago where he said he was selling his beautiful Manchu style bow because he was unable to source sufficiently heavy arrows for it. So this series of blog posts, which will only be on our website (not on our Facebook), we'll go through the trials and tribulations of making super high mass arrows. And before people ask, no, at this time we have no plans on selling complete arrows. We're really not set up to manufacture arrows large scale, so the labor, low volume materials, and thus price would be unreasonable. However, depending on how things go, we may sell raw shafting and/or a few other parts to go with it. 

So where to start? Well, given our science-forward way, lets start with a little research and some math. First off, how large do we need these arrows to actually be? I turned to two sources for this. The first is Peter Dekker's, who is an invaluable resource. THIS ARTICLE gives a fantastic overview. We find they are 92-105cm (36-41 inches) in length and can weigh as much as 100 grams or >1500 grains. These things really are more mini-spears than arrows it seems. 

For confirmation of these numbers, I ended up at Cinnabar Bow and Manchu Bows. In both cases, the Manchu bows allow a 36" draw, and given historical images a fair bit of arrow is expected to remain in front of the bow. Weight-wise Manchu Bows states a minimum grains per pound, henceforth GPP, of 12 while Cinnabar 8% higher at 13. Manchu Bows does however recommend between 13-15GPP. If 50#s were to be considered typical, a 600 grain arrow would be required, but a 750 grain arrow recommended. That said it is often suggested, but never cited, that the Manchu bow design doesn't start to generate significant benefit until one is over 80 pounds draw. That would require 1000 grain arrows, 1200 being optimal. So if we subtract off 150 grains for a point (I am assuming most people shoot targets, so want a target point not a spear head) and divide the remainder by 40 inches, we come out at 26.25 grains per inch. for optimal shooting with an 80 pound Manchu bow. Alright, that is somewhere to start. 

Researching inexpensive arrow woods, I came across poplar. Poplar has the advantage of being straight grained, durable, and comparatively inexpensive. Certainly as compared to cedar which, if purchased in something other than bulk, costs over 1$ per shaft in lumber alone for normal sized shafting. So I acquired a few relatively knot free, straight grained, good looking boards and here we go. 

 Rough sawn 1/2" square poplar arrow blanks

Rough sawn 1/2" square poplar arrow blanks

Step one, align the grain, and then rough saw the boards into straight square blanks. This is the easy part. You make buckets of sawdust, but it is relatively quick and painless. Some setup is required to make sure you got the diameter just so, 1/2" in this case, but no biggie. As an added bonus, one round of this will produce enough paint stirring sticks to last you decades. 

 Off-cuts (scrap) from arrow sawing. These stirring sticks will be put to use for decades to come. 

Off-cuts (scrap) from arrow sawing. These stirring sticks will be put to use for decades to come. 

From here we have to convert the shafting to round. Some people use planes, and I used to as well, but this takes forever. So I now chuck arrows up on the lathe and just spin them down. Quick, easy, glorious. It does produce simply vast amounts of sawdust though. There is another secret advantage to this. Some percentage of arrows contain a fault hidden somewhere. On your bow is not where you want to find this out. Using the lathe applies a fair amount of torque to the arrow shafts, so in general if an arrow is weak it'll die here. Think of it as a convenient early pre-screening, before you've done a ton of work to the shaft. 

 Converting square blanks to round shafting on the lathe. 

Converting square blanks to round shafting on the lathe. 

So now we have a couple rough shafts, how did we do? Well weighing a few and taking an average, it seems we're clocking in right around 25.9 grains per inch. I wish I could chalk it up to skill, years of hard learned lessons apprenticing, but the reality is that it was as much dumb luck as anything else. We'll lose a little weight to sanding, but gain a little weight from a nock, fletching, wrapping, and laquer/finish. So we're right on target. 

 Square arrow blanks next to rough round shafting. Square ends can either be turned into something like bulbous nocks, used to mount points, spun/planed/sanded round, or simply cut off. 

Square arrow blanks next to rough round shafting. Square ends can either be turned into something like bulbous nocks, used to mount points, spun/planed/sanded round, or simply cut off. 

Before I close out this blog post though, I want to do a little more napkin math. After all, what use beyond Manchu bows could such a heavy shaft possibly be? Well if you've followed our bow performance data series (which is about to get an update BTW), you'd know I have a ~110 pound Hwarang which I love dearly. If we return to Cinnabar bow and the Scorpius Turkish "flight bow," you'll see an 8GPP minumum. Extrapolating that to 110 pounds and you're into a 880 grain 31" arrow. Subtract off 100 grains for a point and you're just a hair over 25 grains per inch for the shaft. A 900 grain arrow though still seems impossibly heavy, right? Well, these Korean bows tend to be quite efficient at transferring their energy to arrows, typically over 75% even for the inexpensive ones. So extrapolating given stored kinetic energy, 75% assumed efficiency, and a 900 grain arrow you'd come out with over 204FPS. That is pretty terrifying if you think about it, that is huge power, and I every bit believe the bow could do it as well. I guess time will tell. How about a mere mortal's bow, like an AF Archery Tatar rated 55#s@28"? Assuming 80% efficiency, which is by no means a stretch for these bows given this arrow mass, that'd be a whisker shy of 170fps. Not the speediest arrow that ever hustled down range, but not exactly slow either. Just something to chew on. 

Stay tuned. This project, far from being over, is just beginning. In the coming days/weeks/months we'll post as this project evolves. Thanks everyone for reading.