CHOOSING ARROWS FOR YOUR NEW LONGBOW Joe Vardon WHAT LONGBOW? I am confining the following remarks to “American flatbows”, (referred to in Australia as “longbows”). This is a composite timber/fibreglass bow whose limbs are wider than they are thick and which is widest at the riser. They have an arrow shelf cut into the riser which must not exceed 3/8” deep. This means that the arrow needs to curve around the riser on release and therefore the spine (stiffness) of the arrow is important in getting sufficient clearance and a good flight. ARROW MATERIALS Aluminium or wooden arrows are first choice for longbows. Carbon and carbon/aluminium are generally too stiff and are designed for bows cut to centre-shot or very close to it, as well as being rather expensive for the mortality rate of arrows shot from a longbow! Archery Australia rules currently allow aluminium arrows for all events (target, field, clout and indoor), however FITA or ABA (Australian Bowhunting Association) rules require wooden arrows. Wooden arrows need to match in weight and spine (stiffness) and, although you only need three arrows, keeping a matched set with some reliable spares can be difficult. Some purists insist on shooting wooden arrows from a longbow at all times. Good luck to them, I can see their point of view but I find life is a bit short. Aluminium arrows are branded with a 4-digit code and an alloy identification • Size: 4 digit code – the first two are the outside diameter (OD) in sixty-fourths of an inch. The second two are the wall thickness in thousandths of an inch. For example 1916 = 19/64” OD x 0.016” wall thickness. Thin walled arrows (0.013” up to about 0.016”, often designated “Super Lite”) are easily crushed and special care is needed in straightening. • Alloy: three codes are used. They give the ultimate tensile (stretching) strength in pounds per square inch) of the aluminium alloy from which the arrow is made. X7 (105 000psi, brittle), XX75 (96 000psi, more ductile), Jazz (85 000psi, soft). Brittle alloys are difficult to bend and may shatter if bent too much. Ductile and soft alloys bend relatively easily but are easily straightened. Manufacturers arrow charts are fine for making an initial selection but be sure you are using as input the correct bow type (American Flatbow or Modern Longbow), the correct pile weight (eg 60 grain), the arrow length (eg 28½”) and chosen alloy. It might pay to buy only two, make them up and shoot them before buying a dozen. Your archery club may have beginners sets made up in a range of spine weights but they will all probably be too long. Remember that they will stiffen up if you need a shorter arrow length. Wooden arrows are available in diameters of 5/16”, 11/32”, 23/64” and possibly 3/8”. They are generally sold in spine groups according to the weight of bow they are expected to suit, ie 35-40lb, 40-45lb, 45 – 50lb, etc. Be careful as these spine groups are usually based on the use of heavy piles (field or hunting) and will be stiffer with a light weight target pile. Generally 5/16” would suit target bows to about 40lb @ 28” while 11/32” suit from 40lb to 55lb SPINE Spine, or stiffness, is a measure of how much force is required to bend an arrow. “Low spine weight” refers to an arrow which is easily bent by a sideways force, a “high” spine is the opposite. Why is this important? When the nock of an arrow leaves the fingers of a right-handed archer it is moving to the left (see figure 1) Figure 1 1 This combined with the large compressive force in the arrow tends to buckle the arrow, bending it towards the bow (1) as shown in Fig 2 A few milliseconds later, the arrow straightens and begins to bend the other way and, if the spine of the arrow is correctly matched to the bow, bends around the bow ensuring the fletches and nock clear the bow. The arrow continues to oscillate and this is where the fletches begin to dampen the vibrations and settle the arrow into a steady, straight flight. If the spine is incorrect, the fletches and nock will not clear the bow but hit the riser and cause noise and wild, uncontrolled arrow flight. If the spine is approximately correct, the arrow will clear the bow but may not end up going where it was aimed. If the spine is a little too Figure 2 stiff, the arrow will hit the target to the left of where it was aimed, too soft and it will strike to the right. This phenomenon, where the arrow makes its way around the bow and ends up flying as if it had passed right through the centre of the bow is called the “Archer’s Paradox”. It has been argued about ever since humans first bent a stick and was not completely explained (along with the galloping horse) until the advent of high speed photography. The closer the bow is cut to centre shot, the less critical the arrow spine is (2) . The ideal spine for a longbow shooter is one where the arrow clears the bow by an adequate margin, gives good, stable arrow flight (not flitting or porpoising) and where the arrow is released aiming directly at the target (not aiming off to either side). FLETCHES The function of fletches are to dampen the oscillations of the arrow and bring it to steady, straight flight in a reasonable time. They also impart a spin to the arrow which helps to even out irregularities in spine and straightness. Fletches which are too big or too heavily spiralled on the arrow will certainly get it spinning and stabilise the arrow quickly but at the expense of arrow speed (3) . If fletches are too small, they have insufficient stabilising effect on the arrow which may continue to oscillate all the way to the target. Small fletches are also less forgiving of a poor release. Longbow archers usually use feather fletches. Plastic vanes could, in theory, be used if the spine of the arrow is correct and the release beyond reproach, however feathers are more forgiving of the occasional(?) poor release and can even brush past the bow without dire consequences. Three 4” feather fletches are widely used by longbow shooters on larger arrows and heavier bows; 2½” or 3” feathers on smaller arrows and lighter bows. Note that three 4” feathers are probably rather too large for target archers - our Victorian forebears used 2” or 2½” and this was with “shoot-around” (no cut out arrow shelf) risers. PILES The cast of an arrow is affected by weight; the lighter the better. Conventional wisdom suggests that the finished arrow should balance a bit forward of half its length, indeed some piles are described this way (7% FOC means that the arrow should balance 7% [or about 2” for a 28” shaft] Forward Of Centre). Heavy piles add to the inertia of the front of the arrow on release (make it harder to accelerate) which has the effect of making the arrow bend more or weakening its spine. This can be used 2 to make an arrow shootable which is slightly too stiff for your bow but you pay the price in decreased velocity. For target and field shooting light weight “Nibb” points are most common for aluminium shafts and heavier “Field” piles for wooden arrows. When you demolish the first 20mm or so of your aluminium arrow against a brick wall or concrete butt, all is not lost. Nibb or chisel piles have a 40 – 50mm long insert which is glued into the arrow and this can be used to repair your arrow. Cut off the damaged bit and, provided it doesn’t exceed about 25mm, you can cut a corresponding length off the original arrow offcut (you did save them, didn’t you?), thread it onto the pile insert and glue the lot back into your arrow. See figure 3. This wheeze can also be used to increase the length of Figure 3 arrows which have become too short due to changes in shooting technique. Heavier piles (up to 125 grain) can be used to advantage in clout shooting. Because the flight time is so long (more than 3 seconds compared with about 1 second for 50m target range), the arrow loses momentum at the height of its trajectory and “flutters” down to the clout. Heavier piles cost a little distance but “lead the way” and help keep the arrow stable in the second part of its flight. LENGTH If you are new to longbow shooting it would probably be a good idea to cut your arrows about 1” longer than you need them. As your shooting technique develops your draw length may increase and when it stabilises recut your arrows to the correct length. The correct length? The pile of the arrow should be level with the back of the bow (the side towards the target). You may then care to follow Roger Ascham’s advice in “Toxophilus” (1545), about checking your draw length by feeling the pile of your arrow on your index finger at full draw. ADJUSTMENTS Once you have your bow and acquired your arrows, what can you tune? (for tune, read “fiddle with” – are you sure you wouldn’t be happier shooting a compound?). There are only two adjustments, nocking point position and brace height.