Vane size, does it matter?

[dwilley]

I was reading past posts, trying to find discussion about the choice of the correct size fletching for crossbow arrows.
I read about FOC, but nothing much about the how fletching size effects stability. It's not just a question of having the arrow spin. For rockets, stability is achieved by having the "center of pressure" behind the "center of gravity". The postion of the center of pressure is found by finding the center of gravity of a silouhette of the rocket, cut from a uniform thickness sheet of cardboard or similar. The center of pressure would be where you would need to support the rocket, if the airflow was at 90 degrees to its usual direction, i.e. across the rocket rather than along it, yet not have the rocket rotate. Making the fins bigger increases the area at the back of the rocket and hence moves the center of pressure backward. This makes the rocket more stable. The other way to make it more stable, other than spinning it, is to move the center of gravity forward by putting more weight up front. I'm assuming the same type of analysis can be applied to arrows.
The FOC seems to only take the position of the center of gravity and the physical length of the shaft into account. It does explain why brass inserts can aid stability. What I don't see is anything that takes into account the area of the vanes.
When I got my Ibex a couple of month's ago, it came with 5 inch plastic vanes on the Firebolt shafts. I ordered 3 arrows from Dan Miller, Firebolts with lumenoks, they came with 4 inch vanes. I recently got some Laser IIs, they arrived with 4 inch vanes, but unlike the Firebolts, they have brass inserts, rather than aluminum.
How much difference does any of this make? I'm planning on using 100 grain shockwaves for hunting.
And yes, I am of course going to try each of the arrow types with field points, I have done already to a small extent and so far the 4 inch vs 5 inch vanes do not seem to make much difference. I'd be interested on other's experience, especially those who can shoot better than I, which I'd bet is quite a few of you
cheers,
David

[masboy]

don,t know much about rockets,but from all my testing it,s hard too beat 2 inch blazers with 3 degree helix for acurracy from all arrows i,ve shot. there the best iv,e shot in the wind too.

[Boo]

The 2" Blazer vanes work well because of the texturing of the surface and the abrupt leading edge creates drag. If you look at Rayzrs or just plain feathers they work by way of drag.

[Dash]

When using feild tips, I saw no measurable difference with beman lightning bolts, using 2"blazers or the standard 4"vanes they come with. But I suspect there may be somedifference when I try out broadheads on them or in the wind. Haven't tried it yet, work keeps getting in the way of my private life

[wheelie]

maybe I am wrong, but seems to me that dragging a five inch fletch would cause an arrow to leave the rail slower than dragging a 2 inch fletch along the rail. I started using 2 inch blazers because of shooting whisper biscuit on my vertical hunting bow. The longer fletchs would slow the arrow. Liked them better, bought the bonning fletching jig for them, so I redid them with 3 degree helix. Thats how I evolved to shooting blazers on everything but recurves and longbow. Personal preferance as well.

[bob1961]

the vanes really never touch the rail or shouldn't i should say.......bob

....

[Pydpiper]

Not even sure why I use fletching on my crossbow arrows anymore.
The only difference I have found between the 2" and 5" is that the 2" were less prone to being drifted over by a crosswind, makes good sense to me considering the amount of surface area available for the wind to make contact.
A lot of guys cross over from vertical archery to crossbows and bring some misconceived notions with them. First and most important, the fletching on crossbow arrows plays a different role than they do on the longer, thinner shafts used in vertical archery.
I figured out some stuff when I lost a single vane off one of my hunting arrows, against my better judgement I shot it just to see what would happen. When I found that the missing vane had no affect on the arrows flight I took off another one, and still had a great shooting arrow. Looked kinda odd in flight, but it was absolutely as accurate as a well tuned arrow sporting all three vanes.
I would guess the difference between a vertical bows arrow and a crossbow arrow would be tied in somehow with archers paradox, but I really don't know.

[Limbs and Sticks]

You can shoot a raw shaft out of any bow and it will be close to dead on, the prob starts when you add BH's that sure changes things quick, 2" 5" plastic or feathers can be tuned to the same POI, I like 3" OR 4" feathers they're more forgiving than plastic

Wes

[Muskyhunter1]

Thanks for the physics lesson David.

You were obviously the guy in class who was wide awake during that lecture. Awesome.

Thanks again this time it makes sense.

Dave

[Pydpiper]

It's worth noting that when I was shooting with missing vanes, it was with Slick Tricks, standard size.

[sumner4991]

The difference is so small, it is impossible to detect. I use the 2" Blazers to create a little spin and they are lite. Anywhere I can take a little weight off the rear end, then I do . . .same reason I use the plastic nocks.

[ComfyBear]

It's worth noting that when I was shooting with missing vanes, it was with Slick Tricks, standard size.

What Pyd is saying, even when using broadheads, is correct for short distances. Coming off a rail, the flight of the arrow is initially quite stable. It is further down the flight path that other variables come into play and affect the stability of the arrow. Variables such as FOC, the size and design of the broadhead, as well as that of the vanes all contribute to the behaviour and flight of the arrow. I've been told, and subsequently have discovered on my own that an arrow with higher FOC will work best when using a crossbow. The reasoning behind this theory is that a high FOC will make an arrow fly like a dart. At close range it will shoot fairly flat. As the range increases, although it will drop quicker than an arrow with a lower FOC, it will be more stable, and less affected by wind. With the proper scope adjustment, one can consistently hit a stationary target up to 50 yards.

The arrows I use have 2" Blazers offset at 4 degrees and have a high FOC.

To illustrate what is possible when using an arrow with a high FOC, I'd like to recount three shots I've made over the years. Using a 20" GT Laser II, with brass insert and 100gr. Slicktrick, I cut the heads off two ruffled grouse, the first at 15 yards (no mean feat), and the second at 32 yards. Using a 20" Easton XX75 2216 with a 125gr. G5 Montec, I hit a squirrel at an unbelieveable distance of 55 yards.

All three shots were taken while deer hunting from a tree stand. The 32 yard shot on the grouse was taken resting my Exomag on the treestand rail. Even though I aimed for, and hit its neck, and was a bit surprised at my pinpoint accuracy, I knew that with the accuracy my Exomag was capable of, the odds of scoring a hit on the grouse was high.

The shot on the squirrel was another matter. Before anyone thinks that I'm just a pompous egotist trying to showoff, let me explain. I took the shot after sitting in the treestand for quite a while and not seeing any deer. I don't know why, but upon seeing that squirrel, a thought entered my mind. Just out of curiosity, after aiming at and deliberating for a few seconds, I decided to take the shot and see how close I could come. I never dreamt of making the hit, especially since I shot offhand. I guess on that shot, the stars aligned and the arrow had eyes.

As a disclaimer, even though I consider myself an above average marksman, I would never attempt a shot with a crossbow at a live deer at that distance.

[sumner4991]

I found that knowing the exact yardage is the key. No doubt the bows are accurate. The other critical part is keeping the target motionless until the arrow gets there.

ComfyBear . . .I've done the same thing with the squirrels and after I shoot, I think, "Are squirrels in season?" Never hit one from 55 yards. As a young teenager, I was walking along with my BB gun when a squirrel ran across the limb in front of me and I threw up the gun and fired. Hit the squirrel, against all odds . . .my brother did the same thing to a crow flying overhead once. I call these freak events in my life. I'd trade them all in for one winning lottery ticket.

[dwilley]

As kids, back in England, we made arrows for our homemade long bows by fastening a lump of modeling clay (we called it plasticene) to the front of a straight stick. Worked well enough for a picky seven year old and they didn't need vanes, although they would have helped too.
Start putting those sharp vanes (broadheads) up front and the "steer back on path" that the ones at the back accomplish is fought by the "steer off path" that the ones up front cause. In a lot of ways our arrows are like weather vanes for a very short time. If they are stable they will turn into the wind, if unstable, out of it, and continue to get worse. The cost of the extra stability that large vanes give is the extra drag they cause, but it's that very drag that keeps them pointing forward, we just don't want to overdo it. Which makes me realize, I've never seen anyone using flu-flus with a crossbow
cheers,
David