Enough theory, let’s talk about practicalities. I’m working on the basis that you have your bow and are selecting a new set of arrows. To do this you will need to go through a process called bareshaft tuning. I suggest reading the whole of this post before starting.
You will need a selection of arrows of varying spines. Some shops will do a set of shafts of varying spines for you to try bareshaft tuning your bow. If you can find such a deal then great. If not then your best bet may well be to use wooden arrows for tuning, since they are likely to be cheaper than modern materials. If you are using wood then I recommend screw-fit points. This is because you will be removing the point and shortening the arrow, which with regular points means cutting the point off and sticking a new one on. You might get through a lot of points!
Your starting point is a spine selection chart. There are loads of them online (just google “arrow spine chart”), some for woods and some for carbon/aluminium. They are fairly self-explanatory: you cross-reference your bow’s draw weight and your arrow length to get a spine value for your arrows. This is a starting point only. If offered a choice of bow types, I suggest using “longbow”, but perhaps selecting a draw weight that is slightly higher than your actual draw (5lbs or so). This will depend on your bow’s performance. A really fast Saluki will need stiffer arrows than a budget bow from eBay of the same draw weight.
As I explained last time, arrows of the wrong spine will not fly straight. This is why we use fletching. Fletchings are great. They stabilise your arrows and can iron out a lot of problems with spine and arrow flight. They do this by imparting drag to the back of the arrow. The bigger the fletchings, the quicker and more effectively they will straighten the arrow. The downside is that by imparting drag they slow the arrow down, with all the problems that I discussed when dealing with arrow speed in an earlier post. The less well spined the arrows are, the more time the fletchings will spend side-on to the air, which means the more they will slow the arrow down. Perfectly spined arrows do not need such big fletchings and such fletchings as they do have will not slow the arrow as much as the same fletchings on badly spined arrows. Bareshaft tuning involves shooting unfletched arrows to see how well the arrow is matched to the bow.
Standing about 20ft (7m) from the target (ideally a soft “bag” style target), shoot an overlength bareshaft into the target. It is best to do this with two or three arrows to ensure that any results are not the result of poor technique on a particular shot (if you have poor technique on all your shots then that’s a quite different problem!). Now examine the arrows in the target. In particular, look at the alignment of nock and point, as seen along the line from where you shot.
The interpretation of the arrows depends on how you are shooting. I am going to set it out for a right handed archer using a thumb release, i.e. with the arrow on the right of the bow from the archer’s point of view. The same conclusions will apply to a left handed archer using a Mediterranean release. For a right handed Mediterranean release or a left handed thumb release you need to reverse whatever I write here.
If the arrow hits the target “nock left”, which means that the nock is significantly to the left of the point, then the spine is too strong – the arrow is not bendy enough. Bearing in mind that the bareshaft is too long, you will not be able to get it to shoot properly from your bow. You should discard it and try weaker arrows.
If the arrow hits “nock right” then it is too weak. This is what we are hoping for because it is too long and, as discussed last time, the dynamic spine will get stronger as the arrow is shortened.
Assuming that you are getting a nock right impact, you should now remove the point and shorten the shaft by ½” or so. Reattach the point and shoot it again. The arrow should now be slightly less nock right. Remove the point and shorten it again. Then shoot again and so on. BE CAREFUL NOT TO SHORTEN THE ARROW BEYOND YOUR DRAW LENGTH!
Your arrow spine is right when the bare shaft is hitting dead straight. If it gets there too soon (i.e. your arrow is still far too long) then the arrow is too stiff. If it is still nock right when you reach your minimum length then the arrow is too weak. In either case you either need to get new shafts or you can try to make adjustments to your point weight or brace height.
Brace Height and Point Mass
Ideally you should not make significant changes to these factors, since they will both have other effects. Relatively minor changes can be useful for fine tuning.
For reasons discussed in previous articles, a lower brace height will put more energy into the shot. This means that the arrow will bend more. In other words, a lower brace height effectively weakens the dynamic spine of the arrow. Now, you probably don’t want to make more than a minor adjustment to the brace height (1/2” is plenty). This is a matter of fine tuning.
In addition, brace height changes affect other things about the bow. I once had a student shooting a Grozer biocomposite static recurve. It twanged loudly and felt like it was shaking your fillings out when you shot it. I changed the brace height by ¾” and suddenly the bow shot almost silently and with very little handshock. If you change your brace height as part of bareshaft tuning, therefore, you must remain aware of these possible side effects. It may be better to change the arrows rather than the brace height.
The other piece of fine tuning that you can do is changing the point mass. A heavier point effectively weakens dynamic spine. A lighter point strengthens it. Again, however, changing the arrow mass affects flight. In particular, raising arrow mass decreases arrow speed, so don’t go overboard. For normal bows in the range of 30-50lbs you will probably want to shoot 100-150gn points. Lighter is better than heavier, generally speaking.
Bareshaft and Feathered Together
If you already have some fletched arrows that fly tolerably well then you should include these in your bareshafting. Just mix them in with the bareshafts and shoot them all the same way at the same point on the target. The fletched arrows can be taken as a control group: the bareshafts should hit to the left of the fletched arrows if the bareshafts are too weakly spined and to the right if too stiff (again, assuming a right handed thumb shooter or left handed Mediterranean shooter). If you find that this method is giving you different results from the bareshaft angle (e.g. the bareshafts are hitting left of the fletched arrows but are doing so with a “nock left” impact) then the problem is your shooting form and you should be wary of making and adjustments until you are getting consistent results. If your existing arrows are not spined to the bow then this method is of much less use.
Nocking Point Height
If you nock too high or too low on the string then you will get poor arrow flight and quite possibly cut your hand on the quill of the feather. Bareshafting can be used to get your nocking point height right. To set nocking point height properly, you should start with it obviously too high and shoot at the target. It will impact “nock high”. Now lower the nocking point by 1/4” or so and repeat the shot. The arrow should be slightly less nock high. Repeat this process until the arrow flies straight.
The reason for starting too high is so that you know whether you are high or low. If you start about where you think it should go then you will not know whether to adjust it up or down. Contrary to popular theory, a nocking point that is too low will generally give you a nock high impact because the nock end of the arrow is pushed up as it passes over your hand. If you start too high then all adjustments will be downwards, so long as you only move it a little each time.
If you have read this and my other posts on bow mechanics and arrow dynamics then you will now know all you need to know to set your equipment up properly for maximum efficiency. Please do take the time to select, tune and care for your equipment. Even if horsemanship is more important, the archery side of this sport should not be ignored.
As ever, please do post any comments, questions or observations. I’ve finished with technical stuff for a while. Now for something completely different…