If I wanted to move up in broahead weight to say 165 grain Tree Shark. Do I have to go down or up in spine ? Heavier point weight will weaken spine correct ?

Shooting #57 TIP 29 1/2, 2020 125 grain head. I'm liking  what I see with the tree sharks :^)

Thanks,
Mike

Generally speaking yes.  Heavier weights require a stiffer spine.  Having said that....there's a couple ways to accomplish that.  40 grains is not really that much.  I'd strap them on my current arrows and see how they tune.  You might be able to make small adjustments to brace height to get them to tune or you might be able to remove some length from the arrow in small increments to get them just right without having to buy different shafts.

Yes, heavier point weight will weaken the effective spine.

Guy

You need a stiffer/heavier spined arrow if you are adding weight.  I've never shot a head over 145 gr so I can't say how much.  It's more critical to match it closely with a longbow vs. a recurve (cut close to center).

I am shooting the same basic set-up with 160 snuffers. I would try the tree sharks as is  first before doing any major changes.

You can also build out the side plate a little.

Thanks Guys  

I shot some 180 grain 3 to 1 heads once, didn't notice any differnce.  I would glue some heads on a woody and shoot into a sand pile.  I used to test all broad heads this way till I remarried and the new wife liked cats.  You can't clean that off a woody.  Take my word for it.

It depends on how close you are in tuning. If you're already slightly on the stiff side, you may not need to change anything. If you're on the weak side, you may have to trim a bit of length or go up in spine.

P.S.- as long as I get good flight at full draw, I'd rather be slightly on the weak side so that I still get good flight if I short-draw a bit in a hunting situation.

just last night i put some 165 gr. on my carbon arrows that i usually have 125 gr. on.  I just wanted to see what whould happen.....  I couldn't tell any difference in arrow flight except it had a good bit more drop when shooting out a like 40 yards.

Don,
THANK YOU