Footed carbons and dynamic spine

[xtrema312]

I have some arrows that are a little lighter than I would like, and I am cut down as far as I can go.  I would rather load up the point more than play with internal weights.  I was thinking of adding 3” aluminum footing, which will get me 2” onto the shelf.  I did some searches, but didn’t find a real good discussion on how this changes dynamic spine of the arrow.

If you have put a long footing on a tuned shaft, did you need to add point weight you get to bring it back in tune, and if so how much?

[LCH]

I did it to some 5575's, put 1 1/4" of 2216 over the end. It changed the spine of my arrows so much I won't shoot them any more. I will never do it again. LCH

[Tater]

If the footing outside extends past the insert it will make the shaft stiffer. You will need to add point weight to get the spine where it was.

     If you have access to Stu's calculator add the length beyond the insert and the total weight and then adjust point weight to get back in specs.
   Should get you pretty close.

[Huntschool]

Work with your point adaptor and insert man...
Like LCH said...  it will save you some shafts

[xtrema312]

I ran some number in the calculator earlier and found very little affect.  I was surprised, but I guess that the arrow has not changed length and the footing is not really where the arrow bends the most.  I would have thought it would be a big deal.  I used 3” footing so figured 2” past my 1” inserts and estimated about 30 gr. I only got about 25 gr. more point weight.  That does get me maybe 55-60 gr. And that is a start, but I was hoping to get another 50 gr. In point weight.  I may have to work up a test arrow to see.  I figure there could be a little something for the larger dia. shaft on the riser like building out the riser a little.  That may not be taken into account in the calculator.

[xtrema312]

Originally posted by Huntschool:
Work with your point adaptor and insert man...
Like LCH said...  it will save you some shafts

How do I do that and pick up 50 gr. point weight when the arrow is at minimum length and tuned now?  I can get a heavier head to work, but must give up insert weight.  That in turn moved the point weight out farther weakling the arrow, and I actually lose overall weight, which is exactly what I do not want to do.

One option is to build out the side plate, but that just screws up my bow for shooting other arrows that are heavier and tuned to the bow.

[Huntschool]

[Trad Whitetail]

One option is to add weight at the rear of the shaft (longer feathers, arrow wraps, etc.).  That effectively increases the spine of the arrow.  I foot all of my arrows with aluminum shaft on the end (1.5") and have run into the same problem as you with light arrows, but at 29" draw I don't have a lot of options.  I can tell you that I did not like drawing the footing onto the shelf because of the ridge behind the footing.  Your assumptions about the effects of the footing are correct.  Remember, the calculator will get you close but the only way to see if it works is to test it out.

[slivrslingr]

Only one way to find out for sure.

[Doc Nock]

Fellow used to be on here taught me to use the external footing.

I wanted a lighter weight shaft in the .400 spine and found some target shafts, but they're somewhat thinner walled and more prone to break behind the point.

Cut to regular length, 100 gr. brass insert w/ the 3" over-footing (my term). It stiffened the shaft appropriately so I'm now using a full 200 gr. head where 175 spined me out on a 5575 shaft.

With the weight of the over-footing alum shaft and the 25 gr. extra front weight, I jumped from 23% to 28% MEASURED EFOC.

I got impact protection of the lighter weight shaft, was able to keep my desired 615 gr. overall arrow weight with more front weight added, upped my FOC by 5-6%, improved my arrow flight...and well, I'm happy.

The chap who shared that set up did some torture testing and found the footed shafts out-lived impact tests over the 5575's and other forms of strengthening.

[Earl Jeff]

My spine tester indicated no difference with 1.5 inches of Aluminum footing on the shaft. CX 250 with 1.5" of 2216

[xtrema312]

Thanks Doc Nock.  That sounds about like what I found with running some numbers in Stu’s calculator.  

I have found a good amount of spine change between different combo’s of points and weight and material of the inserts.  I used to think it had some to do with the different lengths and footing affect by the insert.  Now I think it most of the change has to do with moving the point/insert weight forward and back causing more of an arrow length change than footing change.

[xtrema312]

Trad W. - I have been thinking about adding the wraps next time I refletch. I have also been thinking about back weighting to offset the front weight.  I just have not figured how to best get about 50 gr. in the back.

[Mark of WV]

Originally posted by xtrema312:
I just have not figured how to best get about 50 gr. in the back.

You didn't say what type of arrow you are using. I'm tuning with Gold Tips and use the nock adapter (19.6 gr) and added a 50gr weight to it to stiffen my arrows while adding weight though I'm looking to increase FOC and may end of having to cut the shafts (they are still at 30")

The Gold Tips are a great setup for tuning and tinkering almost endless combinations.


Regards,
Mark

[xtrema312]

Originally posted by Huntschool:
Well Todd, if I knew what your point,adaptor, and insert weights were it might help.

Work with your insert and BH..  a fair try.. don't nix it because the calculator says no or because you are currently locked into the set up.

I may be all wrong.  If so tell me and I will shut up...

Thanks for your input.  If only I was a little too stiff.  I am really trying to get two things.  First is more arrow weight.  I am at about 8.8 gpp with this arrow and would like to be closer to 10 gpp.  I also want to get up to a 150 – 175 gr. head to shoot the VPA non vented.  

My current insert is a 100 gr. brass.  My point is 100 gr. This tunes perfect, but my arrow is lighter than I want.  I have tried combinations of 50 gr. brass inserts, standard aluminum inserts with larger head weights.  50 gr. brass insert plus 145 is close, but a hair too weak with no room to cut; maybe going to 4x4 feathers and wraps would get it, but I am still lighter than I want on the arrow.  Standard insert and 175 is really too weak, and I lose arrow weight again.  Getting the footing right could make this work so I get the head I want, but I will gain little in arrow weight.  

I think I will have to look at back weight.  I can get to where I want to be If I could get 50 gr. in the back and 50 gr. on the front.

[xtrema312]

Originally posted by Mark of WV:
 

Originally posted by xtrema312:
I just have not figured how to best get about 50 gr. in the back.

You didn't say what type of arrow you are using. I'm tuning with Gold Tips and use the nock adapter (19.6 gr) and added a 50gr weight to it to stiffen my arrows while adding weight though I'm looking to increase FOC and may end of having to cut the shafts (they are still at 30")

The Gold Tips are a great setup for tuning and tinkering almost endless combinations.


Regards,
Mark [/b]

Beman bow hunters.  I have thought about trying the nock inserts, but I am trying to keep these arrows cheap because that is why I use them in the first place.  I am also not sure I can get the GT inserts in the Beman shafts.  I think the GT is larger.  Maybe I can sand them down a little to fit, but not the cheap way to go.

[Montanawidower]

I use exernal footing for my elk arrows.  If you keep it less than 2" it changes the spine very little in my experience.  I read a big thread by OL and Dr Ed regarding internal footings with hardwood on carbon.  They concluded the problem with external footing is it just moves the weak spot back to the back of the footing.  I have had GTs blow behind the footing while stump shooting, and suspect they are right.  Don't be cheap!  Just experiment and see what works for you. If it costs you some shafts, its money well spent in my mind.

[wv lungbuster]

Originally posted by LCH:
I did it to some 5575's, put 1 1/4" of 2216 over the end. It changed the spine of my arrows so much I won't shoot them any more. I will never do it again. LCH

I don't see how an 1 1/4" footing will change spine. I've footed lots of carbons with the same size footing and never had any problems.

[xtrema312]

I think I will play with a 3" footing to see what it does.  I only blow up arrows most of the time stumping by splitting the end.  I just want to stiffen it some and add some weight.  I think a dab of hot melt at the insert end and some electrical tape on the back side may hold them to shoot in an old bag target and keep them on, but make them easy to get off for cutting and tuning.
   
After this I will stick with the GT trad for a little more shaft weight at least even if I can’t get my point weight up.  I may need to build out all my side plates in the end, but I have some CE250’s for hunting  and don’t want to mess up that arrow set-up.