In Clout archery, archers shoot arrows at a distant target known as the clout. Scoring zones are defined by concentric rings on the ground, the largest of which may be 15 meters in diameter. For adults, the range is typically 100 to 185 meters, depending on age, gender and bow type.
Standard bows may be used for clout although the sighting arrangements may require modification with the use of a prism or periscope attachment if the rules allow. This is necessary as the target is most likely to be hidden by the archer's bow arm. The attachment, by deflecting the sight-line, will return the target to view at the launching elevation.
Typically, a heavier (hence slower) arrow would be employed for higher launch elevation so as to present a larger effective target. Such a trajectory exposes the arrow to higher winds and for a longer period, so the arrow should be of the lowest drag to minimize wind drift. The following discusses the trade-offs in deciding on the best solution.
If one assumes an archer's form for target shooting carries into clout shooting, then the resulting group sizes are often much poorer than expected. There are at least four reasons for this discrepancy:
Each of these may be overcome if all the issues are understood and "designed out".
The clout face is laid flat on the ground, so as seen by the archer is wide with little height. Shot with a typical target bow and arrow (especially compounds) the low flight path translates to an elongated group height – by a factor of 1 / tan β where β is the approach angle of the arrow. As an example, for β = 5° the group height will be ~11x larger than for a vertical face.
A related issue is that arrows approaching the clout at acute angles (say less that 15°) are likely to skip on harder ground and register as a miss.
At the other extreme, when the clout range is equal to the flight range, the sensitivity to the launch elevation variation is at a minimum. Changing the elevation ±1° around the flight range elevation has almost no impact - meaning the effective group height is greatly reduced. The down side is the practical difficulty in establishing the flight range and the lack of scope for adjustment for a head wind.
Somewhere between the extremes there must exist an optimal solution. But what is optimal? It turns out that if the arrow mass is increased so that the flight range is reduced to 8% to 9% above the desired clout range, then the group oval returns close to normal. This is a sweet spot where the enlarged group height due to the oblique target effect is compensated by the reducing range sensitivity with high elevation launches. A launch elevation of about 33° is the result. This arbitrarily defined sweet spot is fairly critical on the arrow mass.
The solution suggested above can result in excessive scale expansion with a one meter reticle spacing on the tape of 2 mm or more. For a capable archer this provides excessive sensitivity. Some would argue it is better to reduce this sensitivity by reducing arrow mass. Setting the flight range to 20% more than the desired clout range would seem to be a reasonable compromise.
If a single sight tape covering several clout ranges is preferred, then reducing arrow mass still further may be desirable. This could be done until the group height is say 70% of the target's inner ring diameter. Archers with better form could then use lighter arrows than poorer archers.
It has been shown above that it is important to have a high launch elevation. To achieve this with a powerful bow, it is necessary to have a heavier (typically 2x - 4x) arrow than target shooting would normally demand.
A heavier arrow is a slower arrow and takes longer to reach the clout and flies higher, increasing the opportunity for wind drift. For this reason, the arrow should also be low drag - thin, shorter with small vanes. The low speed may place the arrow in lamina to turbulent flow transition zone, so a turbulence inducing point (certainly not a streamline point) would be preferred for consistency when center fire and mechanical release is used.
Heavy thin arrows are more likely to be damaged on striking hard ground or alternatively become buried in soft soils. Cost and robustness become considerations. Thin arrows such as X10s would be ideal but are expensive. Some of the thin hunting arrows may be the best compromise. Easton's FMJ 6mm shaft come to mind.
Weight can be added via heavy points and metal rod inserts - some practitioners have used tungsten (for its unmatched density) welding rods for the purpose. It remains important to ensure the FoC is between 7% and 20%.
If using finger release, the dynamic spines still need to be matched. This can be difficult if most of the added mass is at the point or supported by the point. Better to distribute the mass along shaft and epoxy it in place so that the acceleration force transfer is also distributed. This minimizes localized high stress points.
A major consideration is arrow integrity during the launch acceleration and deceleration on target impact. Any added mass must be securely anchored in ways that do not create excessive localized stress. This particularly applies to masses added as internal inserts.
The following table gives an idea of the mass contribution that various rod materials and diameters can provide:
| Rod Material | Diameter mm | Grains/inch | Diameter mm | Grains/inch |
| Steel | 1.60 | 9.0 | 2.4 | 20.0 |
| Tungsten | 1.60 | 21.7 | 2.4 | 48.9 |
| Copper |
1.60 | 10.1 | 2.4 | 22.7 |
| Aluminum | 1.60 | 3.1 | 2.4 | 7.0 |
| Carbon Fiber | 3.96 | 7.7 | 5.0 | 12.4 |
| Carbon Fiber | 6.00 | 17.6 | 7.0 | 23.6 |
| CF Tube | 4.0/2.5 | 4.4 |
Addition allowance should be made for adhesives and any spacer materials.
The "standard" internal diameters of shafts include 4.22 mm (0.166"), 5.18 mm (0.204"), 6.25 mm (0.246") and 7.65 mm (0.301").
The following table lists the density of various useful materials at 20°C.
| Material | Density kg/m3 | |
|---|---|---|
| Air (Standard Atmosphere) Wood (light) Water Steel Tungsten Lead Copper Brass Aluminum Titanium Carbon Fiber Composite Hot Melt Glue |
1.2 700 998 7,870 19,300 11,340 8,940 8,600 2,700 4,540 2,000 1,100 |
When adding internal mass by means of a rod, great care needs to be taken in ensuring mechanical integrity during launch and impact when the G loading may exceed 1000 G. Ideally, internal rods and tubes should run the full length of the shaft and be glued in place, while respecting the FoC requirement. This may require a mix of materials - such as 2.4mm tungsten at the front, and 2.4 mm steel back to the rear.
Fixing the rods in place is important for flight stability and safety.
The rods should be concentric with the arrow shaft to avoid unintended stresses. To achieve this, spacer tube(s) or other constructions may be required.
Glue the rods in place along their entire length. Ensure the rods mate up against the point so that impact shock is transmitted directly to the rods. It is possible some impact conditions will generate a destructive shock-wave in the shaft that may induce fatigue cracking and result in immediate or delayed failure.
Gluing consistently in a long thin tube is not a trivial task. Best to use a low viscosity, slow set epoxy with a vacuum to extract the inevitable bubbles and air pockets. A large disposable medical syringe is reasonably effective vacuum pump. A repeated vacuum, release, vacuum cycle is effective in bring trapped air to the surface.
The reason for a special clout sight is that at the launch elevation, it is very likely the target clout will be hidden by the archer's hand, arm or the bow's riser. The clout sight over comes this by deflecting the sight-line such that the sight pin is able to operate within its normal range. The deflection required is in the order of the launch elevation minus a few degrees.
If the above arrow selection process is followed, then the optical deflection will always be close the 30°.
The question of what is better, prism or periscope types of sights depends on the deflection required. The more deflection you need, the more likely a periscope type is the better solution. The reason is that a "stronger" prism introduces more chromatic aberrations such the target becomes blurred by rainbow effects making it more difficult to identify the precise aiming point. It is possible that this effect can be reduced with the use of Fresnel prisms or color filters, however these are likely to introduce other problems.
This all but rules out simple prisms for the high launch elevation angles (~33°) as required for optimal grouping. However, at sub-optimal launch elevations, prisms are viable.
The sight and its mounting needs to be tolerant to the shock and vibration associated with the launch. It the clout sight attachment clips onto a standard sight, the standard sight has probably not been designed to take much weight on the barrel, so the attachment should be light weight. Shaped surface mirrors are best. Prisms have the advantage of being simple, optically stable, more compact and little to go wrong.
Finally, the periscope types generally have a deflection adjustment whereas the prisms do not. A prism must be purchased with a particular deflection value, so the opportunity for adaption to different launch elevations is limited.
Decide on best arrow mass for your kit as discussed above or using FlyingSticks. Make up a set of arrows to desired mass, ensuring low drag. With the attachment in place, set the sight to mid scale. On a still day at the clout field, range the clout by adjusting the mirror. Once satisfied, semi-permanently lock the adjustable mirror in place with a weak Loctite or nail polish. The scale adjustment is now for head or tail windage.
Discover the prism deflections available, and select the highest below 35°. Select an initial arrow mass as discussed above or using FlyingSticks using the deflection angle of the acquired prism. Be prepared to adjust this mass by having a range of points on hand. With the prism attachment in place, set the sight to mid-scale. On a still day at the clout field, range the clout by adjusting the arrow mass. Once reasonably satisfied, make up a set of clout arrows and fine tune by adjusting the pin's scale position during field testing.
When clout sights are not allowed, an off-target sighting point may be the only option. There are two approached. Identifying a background feature so that a sight-line that intercepts the bow, hand or arm at some reproducible point can be established. This is a trial and error process that may take a few iterations to get right.
A similar but different approach is to placing an aiming point on the ground say 4 m in front of the archer and use a similar process to the previous but moving the aiming point until the elevation and azimuth are right. This method is more sensitive to changes in the archer's standing position and stance.
As discussed above, in ideal conditions the flight range of the arrow could be made equal to the clout range by increasing the arrow weight. Theoretically all launches close to (typically) 42°±1° would then achieve clout range.
The azimuth could be sighted with an off target aiming point as previously covered.
The approach might be useful in very calm conditions with ultra-low drag arrows (perhaps lamina flow), but for normal conditions is likely to be too fickle.
Tune system for the particular clout range by carefully selecting an arrow weight such that the flight range is 8%-9% beyond the clout range. This achieves a launch elevation of about 33° and an arrow mass 2x to 4x the mass of normal target arrows. Of equal importance is the arrow should be low drag - thin, short with small fletches - to minimize wind drift.
Use a mechanically stable and robust periscope sight attachment to a standard sight.