Looks like a killer setup David. Structurally that should be a good, tough arrow. With so many variable component parts how hard was it to get the tuning right? It going to be interesting to see how it performs. Have you tried any adverse angle punishment test shots yet?

Ed

Steve,

The IF was developed as a way to strengthen carbon shafts. The
2007 Update, Part 2 will give you a lot of the hows, whys, and what fors about the IF.

I tried out-footings but found 2 problem areas with them. One, they increase the shaft diameter. Not a problem with some broadheads, but with others they reduced the ferrule diameter/shaft diameter ratio enough to affect penetration and, second, on really hard angular impacts they showed a tendency for the shaft to break right at the rear of the out-footing. There’s a reasonable discussion of why this happens in the aforementioned Update.

There are several factors critical to keeping the the insert and IF joined and preventing ‘backset’ on hard, direct impacts. One is the quality of the epoxy and the care in preping component parts for gluing. Next, the ‘glue ring’ back of the forward, parallel section of the IF is a very important factor. Third, and the most costly to determine, is that a MINIMUM of 3″ of shaft wall attachment to insert and IF is required. Less length of attachment and there was backset on direct impacts.

Now this amount of strength MAY be overkill of a hard, heavy bone impact, but that’s not a chance I want to take. Just look at the shaft damage rates that are shown in the Update. In many ways, a bone impact MIGHT be even harder on the structural integrity of the arrow system than the testing I used in the IF development.

During development, the IF durability/strength testing was done with direct and 45 degree angular impacts from 20 yards against a 3/8″ piece of armor plate (the hatch cover from an armored personnel carrier). Most bones have surfaces that are specifically designed to deflect and redirect impact forces. They have surfaces that simultaneously curve in more than one direction. This can cause some really wierd, fast directional change stress patterns on the arrow, pushing its integrity to the limit.

The ability to use the IF as a way of increasing FOC and fine-tuning dynamic arrow spine are just very useful side benefits. Total structural integrity of the arrow system is the BIG reason for using the IF. As you’ll also see in the upcoming 2008 Updates there appeared to be less stess on the arrow’s direct-impact structutal integrity with the Ultra-EFOC arrows; where shaft weight was reduced over the arrows previously tested, in order to get above 30% FOC. Far from conclusive though. Unless further testing shows something unexpected, I’ll keep using IF on my ‘serious’ hunting arrows.

Ed

David,

You have no idea how much I appreciate the feedback I get from your field results. There’s a good number of folks using penetration enhanced arrow setups now, but few really LOOK to see the terminal performance, and fewer yet get the good ‘damage photos’ you do.

I started out the 2008 testing to look at FOC’s effect (or lack there of) on the Heavy Bone Threshold. but it morphed into Ultra-EFOC. I think that’s exactly where we need to be headed. If I can recover from all this medical stuff and get back to doing things more important (LOL) I want to get to at least 35% FOC for some testing.

I totally concur. That scapular ridge hit is the toughest one to deal with. I’t not so much the amount of bone thickness as it is the multiple angles of bone impact on a single impact. Penetration of the BH can get ‘redirected’, deflected on a secondary course, by impact with the scapular flat while it’s still trying to penetrate the first bone impact (the ridge). That tends to bind the broadhead. When testing with some softer 3:1 double-bevel single blades (the early model Tusker Concord – not the currently made version) I got huge BH bends occurring at a point between ridge-impact and scapular flat impact. Had them with some other, lower MA single blade BH’s too. I’m really looking forward to what you find on those shots when you start the pig testing!

Ed

I Love it, Dave! But … EVERYONE KNOWS that narrow single blade broadheads don’t make big holes in the hide, don’t do much damage to the tissues, and they NEVER leave a blood trail! 🙄

Ed

Kingwouldbe wrote: … it also imparts “IMHO” ten times the flight response in the animal.

That’s spot on, and very, very few folks seem to realize it!

You’re right about Fred too. Everyone thinks of him and then the “4-blade Razorhead”. I personally heard Fred say that the bleeder blade was for one thing; to open the skin to reduce arrow drag, increasing penetration. The hard, blue steel in his bleeder blade was specifically chosen to shatter in bone impact and, as Fred said “let the broadhead penetrate like any other good single blade”. The famous “shooting them once with a Razorhead is like shooting them twice with other broadheads” was purely a sales gimick thought up by the advertizing agency.

Ed

All the newer Updates are posted right here. Just go to the ‘Ashby Library” at the page top.

Ed

It’s worth mentioning that the tapered portion of the IF NEEDS TO BE STRAIGHT; that is, aligned with the center axis of the shaft. I start with a dowel rod and turn it down while it’s rotating (lathe, or lathe technique in a drill press or hand drill). The 6mm diameter hardwood dowels I get in Australia are ‘sopt on’ diameter for most of the commonly used carbon shafts, but I haven’t been able to locate them here in the States, so using 1/4″ as a start.

Unless done in a lathe, where one end can be supported by a ‘live center’, you’ll need to go slowly, using very light pressure against the dowel. They’re thin dowels, and too much pressure will just flex the dowel, instead of removing the material that is ‘off-axis’. When it’s ‘trued’ there will be no visible wobble as the dowel rotates. I try to true up the alignment before doing the final tapering of the back 5″ to get the degree of flex I’m looking for in the IF.

The IF’s takes a bit of patience to make correctly, and can be a pain at times, but well worth the effort if you’re after maximum shaft integrity.

Ed

Here we go, Dave, by the numbers:

#1. Initially I did have a problem with weakness at this joint, but only on the hard, direct impacts. The Insert would set-back; pushing up into the shaft. Determining how much support back of the insert was required, and determining the minimum amount of support that would work, was the most costly of all the testing (broke a lot of shafts). With the slow cure epoxy I use (Selley’s Maximum Hold) the MINIMUM combined length of glue attachment between insert/IF and the shaft’s inner wall is 3″. I THINK it will be similar with any of the quality slow-cure epoxies. There was no difference in back-set resistance between a 3″ attachment and the longer attachments. So, as long as the combined length of the insert and the parallel section of the IF is 3″ or longer, you should be fine.

#2. With the 7″ IF the spine change was not very much, but as the IF gets longer (by lengthening the parallel portion) the spin becomes decidedly stiffer. This can be a useful tuning tool at times.

#3. Perleminary information on what the data to date indicates about the relationship between FOC, mass and penetration will be upcoming in (I think) the Part 6 or 7 Update. For a quick answer, I THINK the 650 grain 32% FOC setup will edge-out the 765 grain 28% FOC setup. A SERIES of head to head test (so an average outcome can be determined) between these two setups would be real nice (hint, hint). I’ll be waiting for your results! 😀

When I’m up to it again, I’ll be trying some more work in the Ultra-EFOC range. There will be some initial test data upcoming (Part 3 or 4) with a 655 grain Ultra-EFOC arrow (31.4%) from the 82# longbow, along with how it compared to other arrow setups from the same bow; including the ‘traditional’ super-heavy buffalo arrow setups. It’s pretty eye-popping stuff, and shakes the traditional norms for “heavy game” arrows.

Hope that answered your questions. If not, fire away!

Ed

That’s an unknow for me Dave, I’ve never used Gorilla glue. I suspect it might be a problem if it expands as it cures. I think I’d go with a slow cure epoxy.

On bows with the shelf cut deep I’ve been building the arrow plate out. That lets you tune with a weaker dynamic spine. If you’re going to keep the total weight near 650 grains at 32% FOC you’re going to need as light a shaft weight as you can get to tune. So far, I’ve had my best results with GT Ultra Light shafts.

Ed

David, that’s a “I don’t know”. The tapered portion only matters on angular impacts, to spread the stress force across a longer section of the shaft. A parallel section 9″ long wouldn’t stop the shaft fractures on hard, angular impacts (I’m talking the 45 degree test shots on the armor plate). Never tried parallel sections longer than that on the angular armor plate shots. All the 9″ sections did was was shift the shaft’s weak spot back, and they broke right were to dowel rod ended. At 12 to 15″ inches? It might work; might not. Best to just test one on a few 45 degree impacts on something real heard; a concrete wall should work for the angular impact test. Then we’ll know!

Ed

TTT for partick.

Ed

Someone contacted me to ask why their Internal Footings rattled in flight and when tapped on a hard surface. Here’s my reply, in case anyone else encounters the same problem.

A couple of things will cause this to occur.

(1) If the IFR isn’t concentric and axially straight it will rest against one side of the shaft, rather than having the tapering section centered in the shaft. This causes uneven oscillation, and a rattle in flight, and when tapped on a firm surface.

(2) The other thing that can cause such a rattle is the shape (profile) of the tapered section of the IF. The correct taper is a long, slowly increasing parabolic curve. Along most of the tapering section the clearance between IF and shaft’s inner wall is very slight, and increases only at a very, very gradual rate. As the curve approaches the last (approximately) inch or so of the taper the rate of increase in gap size between the IF and the shaft’s inner wall speeds up a bit. Even with this speeded up rate of curvature at the taper’s trailing section, the clearance between the rearward end of the IF and the shaft’s inner wall (on each side) will only be about 1/4 the shaft’s inside diameter. (Or, you could say the very back end of the IF has a diameter equaling about 1/2 the shaft’s inside diameter.) Of course, since the back end is a curved surface I don’t mean a measurement to the very center of the IF’s curved rear end but, rather, the measurement a millimeter or so in front of that.

Keep the IF as linearly straight and concentric as you can. The IF’s profile is initially parallel, then it begins tapering very, very gradually, then a somewhat faster parabolic taper near the very back end.

I know that’s not an easy to understand explanation but I hope it helps you a bit.

Ed