QuoteOriginally posted by Zradix:
I didn't realize adding wt to the tip of a carbon or alum shaft didn't change the spine much.

Seems it would no matter what the material.
Interesting.

You're correct; it does. You cannot take a well tuned arrow, add a bunch of weight to the front end, and still have a well tuned arrow. Physics is physics.

...back into the realm of confusion...  

Zradix,

Don't be confused by whatever number a manufacturer uses for their spine rating (i.e. 55/75). That doesn't mean they shoot the same over a 20# range. It's just a label the maker uses, which in the case of Gold Tips, means they spine at .400.

Carbon arrows have a lot of good attibutes, but they don't defy the laws of physics. As you add weight to the tip of an arrow, it will make it act weaker. The opposite is true is you use a lighter tip -- it will act stiffer.

Sambar, I think you may have thrown yourself a curve ball.  You stated you have a 30" draw but you're quoting a 33" length...don't include the point in your length measurement.  Measure to the back of the point.  If you're including the point that is likely why your FOC calculation is coming out so low.

yea thanks mate i got onto the foc calculator and now measured it from the back of the point and got a foc of 9.67% and a gpp of 11.57 so that sould be fine to work with i think.

I have observed by experience that my Carbons with 200 grains up front penetrate the target better than my woodies which bounce off alot more.  48# longbow.  After reading Dr. Ashby's reports it seems that EFOC is good for penetration.  So for wood hunting arrows I am thinking about adding weight to the point (using a screw in adapter) rather than going for heavy shafts.  But this increases the spine of wood shaft needed.  So I need to go from Doug fir 60-65 spine to a 80-85 spine using 240 grains on the point with a total arrow weight of 600 grains.

Has anyone else tried this?

Jason....I think what Rob means is that Carbons are more 'forgiving' or 'tolerant' of head weight differences.  Least that's what I have found with carbon....being able to shoot 100 grain differences with the same arrow....and not so much with the same wood arrow.

I also think that 33 inch wood arrow is not a worry if its flying good out of the bow.  Unless its made of balsa    :D

Just a suggestion but may be far off the mark for what you are looking for.

I shoot techno-hunt periodically and since the mushroom pts only go up to 145 grains and I shoot 300 grains I needed to come up with something. Took 300 grain pts, machined and threaded them to accept 100 gn mushroom pts. All 6 modified pt adaptors came out 202 to 204 grains.

Just a thought.

Note: Have extremely limited experience working with woodies. Haven't shot woodies since early 70's.