Sveltri, Whey, it took me a while be here you are.
I tune the fletching to give the smallest fletching that will stabilize the broadhead under all shooting conditions. I prefer the A&A fletching pattern, which utilizes a turbulator forward of the fletching. Here's the process I use to tune the A&A fletching, but the same process works for determining the minimum size for any fletching pattern. Just as when bare shaft tuning, finding the minimum amount fletching is a step by step process.
First, here’s the A&A fleching’s characteristics: The rear edge is a straight, vertical cut, ½” high – regardless of the fletching’s length. From the top of the rear edge the feather tapers in a straight line to the leading edge, making a right angle triangle. The fletching is applied as a straight fletch; no offset and no helical. A turbulator is placed ¼” in front of the fletching’s leading edge. The turbulator is made from a 1/32” wide strip of pinstripe tape; which is used to add pinstripes on model cars and airplanes, and is available from most any hobby store.
Here’s the tuning process:
1. Once you feel that you have the bare shaft tuned correctly, mount a matched-weight broadhead on one of the shafts. First use what you are absolutely certain is ample fletching to stabilize the broadhead and VERIFY that the fletched-shaft/broadhead has identical impact to the field-point tipped bare shaft. You can use any fletching pattern you like for this step.
2. Once your shaft tuning is verified you can begin tuning the fletching. Switch to the A&A fletching pattern on the broadhead tipped shaft. Mount the fletching as far rearward on your shaft as you can possibly use. This gives the fletching as long a rear lever arm as possible. If you use a finger-release start at about 5” length if you are using 3-fletch, or 4” if using 4-fletch. If you are using a broadhead with a high Mechanical Advantage (which also has a low windsheer effect) you can reduce these ‘starting point’ fletching lengths by a full 1”. DO NOT add the turbulator yet. Shoot the arrow several times and check the flight stability. NOTE: I usually use fletching tape during the tuning process, because it makes changing the fletching easier and faster. but prefer glue once I have the finished dimensions for my fletching.
3. If all is well, begin to gradually decrease the length of the A&A fletchings, in ¼” steps, until the point where you FIRST see a slight instability in the arrow’s flight. Be sure to shoot several shots before making a decision on the flight stability, and it helps if you can have another person also watching for flight instability too.
4. Now add the turbulator and check to be sure the flight is again completely stable. If addition of the turbulator does not completely stabilize the arrow’s flight increase the fletching length by 1/8” and move the turbulator forward to maintain the ¼” spacing between it and the fletching’s leading edge, and check again, with the turbulator in place. If there is still instability increase the fletching length and additional 1/8”, again moving the turbulator forward to maintain the ¼” spacing.
Many factors affect what's the minimum A&A fletching that will work FOR YOU. A big factor is quality of your release (mine’s poor). Other major factors are the type of broadhead (how much wind shear it generates) and the amount of FOC on the arrow and the shaft’s length. Your draw length and whatever length shaft you are using are also factors. At a given amount of FOC, the longer the shaft the less fletching required; because of the lengthened rear steering arm. Your draw length vs. shaft length affects the point of maximum shaft flex upon release.
5. Once you feel you have the fletching at the minimum size for stability there’s only two tasks remaining; (1) shoot the arrow a lot to verify that there is sufficient fletching to stabilize the arrow even when you get a bad release and (2) check arrow flight on a windy day. When checking for flight in windy conditions you will want to take shots at as many angles to the wind as possible, but at an absolute minimum check the arrow’s flight in a full cross-wind and both quartering with and quartering into the wind. If there is any problem with stability in either of these tests you should increase the length of the fletching gradually, in 1/8” increments, until the arrow shows stable flight under all conditions of release and wind direction.
I’ve not found any release or wind direction problems when using the high MA single blade broadheads, because of their very low windshear factor, but many of the wide-narrow broadheads require an increase in fletching area to achieve flight stability in quartering wind conditions.
This sounds like a lot of work, and it is, but it is a one time job for a given arrow setup. It’s analogous to a working up the very best handload for a rifle; and cheaper and easier to accomplish than finding the best rifle handload too!
I hope the foregoing is coherent enough to be understood.
Ed
Topic: EFOC arrow video in high winds (Read 567 times)
