Journey to EFOC w/woodies

[martin guy]

After much research (and a little devolopment) I have finally come up with a way to add a decent amount of weight to the front of a wood arrow. I am using a std. cordless drill, a 9/64" bit, and 2" of 1/8" tungsten rod. The pictures pretty much show the process. With a 2" pc. of tungsten I can add 120 grains.    
The tungsten is extremely hard and rigid so it should act as an internal footing as well.

Andy

 EFOC jig

[flint kemper]

Andy, may I ask where you got the jig? Or do you sell them? Thanks Flint

[Skinny Little Runt]

The jig is steel? Like wise, I'm guessing changing the filler(rod 0r shot)for other wt values.
Very clever.

[martin guy]

I made the jig, it was more time consuming and exacting than I thought!
The tungsten is the heaviest "filler" I have found so far. (thanks O.L.)

Andy

[Oregon Okie]

I did something similar. I also was playing around with the dynamic spine calculator and if I want to match up on that I am going to need to build out my arrow rest or get really heavy spine. Isn't this "fun"    

[martin guy]

I am having fun so far! The jig makes it so much easier, I can have an arrow done in a couple of minutes and I don't have to worry about it(the hole) being centered.

[Dave2old]

Thanks, Martin. O.L. Adcock does the same thing. Can't believe how much that skinny tungsten rod weighs! I doubt that it's cheap, either. In my own experimentation I'm going the other way -- using 3" lengths of aluminum shaft with a screw-in adaptor hot-glued in the front end, fitted down over a wood shaft with blunt/flat (not pointed) end. This allow the use of the heavier screw-in heads plus weights, while strengthening the end of the wood shaft where it normally breaks. No gig, easy and cheap ... but not nearly so clean and invisible as your process. Dave

[Oregon Okie]

Dave... when you "foot" with the aluminums do you get a bump when drawing back. I looked at that method and thought it might just start snagging a little wood off of the shelf or rest when you draw back. Guess you can sand the edge off.. what have you found on this?

[martin guy]

I footed my carbons with aluminum and I left them long for tuning purposes so no "bump". If you cut them short you will get a "bump", I don't think it would affect arrow flight much, especially if you tuned for it.(the extra 16th of an inch diameter, or whatever it is)

[Orion]

Andy:  I've been doing this for a while as well as have a few others.  Those threads are still on here somewhere.  Have been considering producing a commercial jig.  Looking at machining and insurance costs now.  Gets expensive pretty fast.

What's the diameter of your tungsten rod?  I've been using 1/8 and 3/16 steel rod.  One-eighth threaded steel rod is 20 grains per inch.  I expect the solid rod is 5 grains or so heavier per inch.  3/16 solid steel rod is just about exactly 50 grains per inch.  I expect threaded 3/16 rod would be 7-10 grains less per inch.  Will be picking up and weighing some of the sizes/configurations I don't have, and brass, in the next few days.  I'm looking for stuff that is widely available at hardware and building supply stores.

In my experience, the footing strengthens the shaft immediately behind the point and doesn't change the static spine.  Haven't done enough experimenting to reach the upper limit of physical weight that can be added to a wood shaft.  I expect spine weight, particularly in 5/16 and 11/32 shafts will limit how much weight can be added.  It won't be possible to load them as heavily as carbons because wood, cedar anyway, just isn't available in heavy enough spines to handle it.  Even a mid-weight, high performance bow would probably require a 75-80# spine or higher when front loaded, and that's getting pretty hard to find in a 11/32 shaft.

More experimentation is needed.

[martin guy]

The tungsten is 1/8" and weighs 60 grains an inch.2" equals 120 grains.(it is not available in hardware stores and can not be cut with hand tools) I have found I have had to go up in spine at least 10#s, maybe more, I'm still experimenting with my bow set up.
I believe Tim at Braveheart Archery is going to carry these very soon. I think it will be offered with the jig and a 6" 9/64" drill bit, the tungsten will be an available option.
The tungsten is the heaviest, toughest stuff I have found so far.

Andy

[martin guy]

I need to correct that, according to the nifty dynamic spine calculator I just downloaded (thanks Stu!) I need about 25# more spine.

Andy