J-dogJuly 11, 2009 at 10:29 pmPost count: 47
OK been thinking (dangerous)
I shoot axis 400s out of a 55# silvertip recurve 28.5″ 100 grain adapters toting 160 grizzlies. They shoot great – fly like darts, they ain’t broke, but want to fix anyway.
idea is to get more FOC and overall grainweight to the arrow but most up front. My thought was to glue 2 100grain brass inserts into the arrow (stacked). One gets the BHd the other is just there for mutual grain support. It would turn out a 650 grain arrow (roughly) most of it up front.
Loss of spine is my only concern> I might have to bump up a spine weight?
I always say you have to try somehting for yourself but it doesn’t hurt to get advice either!! LOL
Steve Sr.July 11, 2009 at 11:16 pmPost count: 344
I guess Im lost. Are you already using a 100 grain brass insert, a 100 grain steel broadhead adapter and the 160 grain Grizz?
That’s 360 right there not counting adhesives. Ive two 400 shafts here one 9 gpi and one 10.2. Times 28.5 plus a bit for fletching and nock should be over 600?..at least.
Ive never tried heavier that that 360 head total….yet LOL
Cant help there.
Ed AshbyMemberJuly 12, 2009 at 1:05 amPost count: 816
J – You can certainly add a weight (be it another brass insert or any other weight that will fit) behind the primary insert, as a way to increase tip weight/FOC. This is one of the methods I’ve used several times. However, if you’ll look at the ‘EFOC & Woodies’ thread; I added a post there about the angular-impact shaft-weakening effect that results from having a ‘longer insert’. I prefer to have as much of the weight as possible in the head/adaptor, then I use the graduated-flex Internal Footing back of the insert. The IF, depending on its length, can also be used to stiffen the dynamic spine, when needed.
The ‘new’ Grizzly’s sound like they will be a few grains heavier, and that’s good. I’m told that the biggest of the single-bevel STOS glue-ons are supposed to be close to 250 grains (when available), and Ed Schlief is working on a ‘machined from a single piece’ glue-on “Ashby Traditional” that will be longer than the screw-in version (with the same overall width) and a weight a bit over 250 grains.
Another option would be a steel adaptor. At the moment you would have to get someone to custom make them, but Jon Hand (email@example.com) is a machinest and bowhunter who has made some prototypes that work perfectly. Jon was looking for a jobber to destribute them for him (he’s not interested in marketing them himself), but I haven’t seen any advertized, so don’t know if they are available. You might contact Jon and respectifully grovel at his feet and be able to get a few steel inserts.:)
J-dogJuly 12, 2009 at 2:17 pmPost count: 47
Clay, I have regular inserts with 100 grain steel adapters + 160 grizzlys. 400s are 9gpi * 28.5 + roughly 260 so the shafts are now 516 gpi minus feathers nock. With the brass they are kickin + 100 (616) if I add 100 more (then 2 brass adapters then 700 something. ll really rough figuring mind you. Know your a math person!
I am worried about them riding point down as well, I tried the 600 grain ( 1 brass insert) this morning and flew great – bare shafted well (only have two right now.) Tried rigging the 2 brass inserts without glueing them into the shaft, I placed a piece of scotch tape around them to bind them in the shaft. That was a one shot deal as I forgot to place a plastic trash can behind my target to catch the inserts if they came out after passing through.
In the end I think if the 600 grain arrow flys good after some more bareshafting then that might be my new arrow.
Also what is the IF?? I was thinking of trying to glue a small section of weight tube behind the insert but that would add minimal weight. Though with about 6 inches I could break 650 gpi – which is my goal.
Long post sorry! – will do more shooting after the grass is cut this evening.
IronCreekArcherJuly 12, 2009 at 3:36 pmPost count: 79
I like the idea of getting more weight up front but never considered the fact that it will weaken the arrow behind the point. I was also wondering why the need to shoot such heavy arrows? I know about the heavy bone threshold but I am wondering if the EFoC percentage is the thing we should be focusing on more? Dr. Ashby your thoughts on this? As a for instance…I am shooting a 550 grain arrow with an EFoC of 24.38%…for what I am hunting (whitetails) I feel that this should get the job done pretty readily. I could be completely wrong on this though, I am just throwing some ideas and thoughts out there.
Ed AshbyMemberJuly 12, 2009 at 3:41 pmPost count: 816
J – First, check out the 2007 Update, Parts 2 & 3. That will give you the background on the Internal Footings. After that, perhaps the following photos will make a bit more sense.
When I’m a bit more up to it I’ll try to do a full explination on the IF design, construction and instillation.
J-dogJuly 12, 2009 at 10:45 pmPost count: 47
OK I see I will re-read the update – I have heard of internal footing.
Ironcreek – I think 550 will punch holes both sides of anywhitetail walking! I have read about the bone threshhold and am looking to find a way to get to it. Went back and tried 2 brass inserts and got some really funky flight charachteristics out of the arrow!!! Maybe I should go check with a boeing engineer friend of mine. Tried all three my arrow setups this evening and still the originals are the best but they are roundabout 500 grain arrows. I am looking to add another 150 and get good flight but am unsure if it is attainable with a 400 axis.
Going back out to shoot more and to dig in my garage for some hardwood dowels!
Anymore ideas keep em coming.
Iron what arrows are you shooting? Setup?
IronCreekArcherJuly 13, 2009 at 3:54 amPost count: 79
Copied from my thread on this very topic. You should check it out Dr. Ashby has posted some great pictures there!
Stories, Experience and your Dr. Ashby Inspired Set-Up
Posted Sunday, July 5, 2009 at 5:54 PM
…I am shooting a Black Widow PMA III pulling 49 lbs at my 28 inch draw. My arrows are Easton Axis N-Fused 500 carbons with 100 grain brass inserts tipped with 217 grain (w/ adapter) Abowyer Brown Bear broadheads. I used the FOC calculation chart in the Ashby Library and my arrows are 24.38% EFoC…
MontanaFordJuly 13, 2009 at 11:01 pmPost count: 450
I’m shooting 60# @ 29 1/2″ out of a Bear Grizzly, and currently, I shoot Easton Gamegetter 2117’s cut at 31 1/2″, with a standard aluminum insert and 145 gr. field tip (150 gr. Wensel Woodsman). My FOC calculated out to 13.49%. Over the weekend, I got ahold of some carbon shafting that fits snugly inside my aluminum shaft. I’m planning to put between 6 and 8″ of carbon shafting inside my aluminum behind the insert (possibly with a 15 gr. insert in the carbon shafting). How much is this likely to affect my arrow spine? Is it likely that I’ll have to cut my aluminum shaft shorter to compensate for the extra weight up front? Any advice or other suggestions would be appreciated. Thanks.
Mark TurtonJuly 14, 2009 at 11:37 amPost count: 759
I hope that Steve Sr has no objection to me posting this but he’s been speaking to me about using Tungsten Carbide for adding additional weight, one suggestion was to use ‘horseshoe pins’ these are small tapering cylinders of TC (maximum diameter 4.3 mm.) that weigh in at about 25.4 grains if memory serves.
I haven’t tried these but if anyone would like to give them a go drop me a line and I’ll put some in the post.
Best regards, Mark.
Jason WesbrockMemberJuly 14, 2009 at 3:45 pmPost count: 762
If I’m not mistaken, the rule of thumb is that every 35 grains added to the tip weight decreases dynamic spine by 5#. Coincidentally, one inch of change in shaft length will have the same effect. This was for wood or aluminum arrows, but with carbon arrows you have a little more leeway than 35 grains of tip weight before you change dynamic spine by 5#. Notice I said a little—carbons may be nice, but they don’t defy the laws of physics.
Since we’re both shooting Easton/Beman carbons, I went down to my shop and ran some numbers for you. On my spine tester (brand new Ace Spin-Spine), here’s what I found for an average of several shafts in each spine class:
400’s = 82#
340’s = 95#
300’s = 110#
Basically, every spine class moves you 15# of stiffness one way or the other.
For me: a 340 with 150 grains of total tip weight will bareshaft the same as a 300 with 300 grains up front, with respect to weak/stiff spine. So if I had to put a raw number on how many grains up front it takes to shift dynamic spine by 5#, I’d have to ballpark it at 50.
According to your posts, you are currently shooting 400’s with about 260 grains up front (160-grain head, 100-grain adapter). Adding 100 grains more to the front will weaken the dynamic spine of your shafts approximately 10#. 200 grains will weaken them by 20#. That’s why you’re seeing increasingly worse arrow flight as you add more tip/insert weight. If you want to add 100 grains up front and achieve the same excellent flight as your current arrows, you’ll have to go to a 340 shaft and leave them a little long.
Remember, heavy arrows an EFOC are not substitutes for poor arrow flight, which is probably why Ashby ranks perfect arrow flight above EFOC and arrow mass with respect to his findings of their effects on penetration. But before you can worry about penetration, you have to first hit where you’re aiming. When you put a broadhead on the front of a poor-flying arrow, you can pretty much throw consistent shooting out the door.
J-dogJuly 14, 2009 at 7:15 pmPost count: 47
Great info, My 500 grainers are getting it done just about as good as a finger shot bow is gonna get at this point. Agree about arrow flight as well and I am trying to keep the flight and get the weight up – Was kinda figuring to get what I want I will need to get to a 340 shaft. Wish I could find just a couple to mess with before dropping the money on a dozen 340s. Have to call the archery shop!
Thanks for the info yall, keep any and all ideas flowing!
MontanaFordJuly 15, 2009 at 4:05 amPost count: 450
Well, I managed to get 20+ FOC today on a 30 1/2″ aluminum arrow, but lemme tell ya, that was a trick. On my insert for my 145 field tip, I opened up the back end of the insert, screwed in a smaller field tip (i think about 100 gr.), slid in two 8″ pieces of 2 different size carbon arrows (one inside the other), stuck in my “double field tipped” insert, and tried to bare-shaft it…well, i shoulda glued the carbon shafting in, at the very least….part way to the target, i heard the carbon shafting hit the nock-end of the shaft with a solid “TINK”, and out of the sky my arrow fell….the field tip end was toast, the insert having split out the side at about a 30 degree angle to the shaft…lol…all in all, a learning experience. however, before the carbon shafting slid to the back of the arrow, it looked like it was gonna fly pretty nice….hafta try again tomorrow.
p.s. i don’t know what my overall weight was, but i’m quite certain it was well over 650 grains.
J-dogJuly 15, 2009 at 3:43 pmPost count: 47
Montana, just saw the TBM “tip” on my email and it spoke of weedeater string but to keep in place gue an insert behind (nock side) of the string???? worth a shot. Gonna calland see of I can get some 340s from an archery shop close by then weight down the front end to spine em right to my bow. If not I will keep the 400s I have worked up now.
MontanaFordJuly 16, 2009 at 4:22 amPost count: 450
I’m thinking next time I may forego the extra field tip in the back of my insert, as I don’t think it was particularly stable and may have attributed to the insert/145 gr. tip blowing out the side of the shaft. Will have to figure something else out, perhaps. May even give the weedeater string a shot inside my inner carbon shaft. Anyway, lots to ponder and think about.
Steve Sr.July 16, 2009 at 11:00 amPost count: 344
Probably premature as I’ve not put grain scale to finished arrow yet but in putting together an old M.J. Log fiberglass (ah TOLD ya I was different!)for testing I found my taped together combo of insert, interior footing, shaft and head was a bit shy of 20 percent FOC.
Not having the yet convinced myself to buy any tungsten putty on the web and half wondering what gyrations I’d need to get it to stay where I wanted, I went in search of local options.
At the local hardware store while picking up a tube of Barge to slap on a home made strike plate I happened to see a package of waterproof epoxy putty. I slipped the cardboard off the hanger and discovered that stuff is HEAVY!
At first I had several misgivings after reading the “WARNING” paragraph but common sense told me that if I had rock hardened putty in my meat I was also going to have a crapload of fiberglass, carbon and epoxy, none of which are edible, safe, or fun (or wanted), in said meat. I ended up taking it home as well.
Not being one to fear admitting I can be idiotic trying things, I whacked off a hunk (its a roll you cut off what you want and mix the two colors in your fingers till all the same color)and mixed it while guessing how much to use since the previously mentioned grain scale was at a friend’s house.
I fully suspect the name “big ugly” is going to be appropriate for this arrow. That small piece, rolled into a LESS THAN 1/4 inch diameter, 2 inch long insertion that I tamped in place inside the inner shaft with a wet allen wrench, took the FOC from about 19 to just under 21%.
I fully expect this total arrow weight to be a “bit much” but will find out today. I’m testing the combined composites on an arrow one at a time, not knowing exactly how spine will be effected, en masse, but am not worried because between the two of us here, we’ve a somewhat wide range in bow weights to try it from.
A couple of words of advise here…..read the warning!! and a head’s up..THIS STUFF SETS UP QUICKLY!
Long story short (ain’t THAT A LAUGH! Sorry!) if you have some laying around or 4 bucks to spare, the epoxy putty may be helpful to some for interior weight. While it wont have the density of tungsten putty, my brain kept saying “a grain” is 1/7000 of a pound and there is a roughly calculated 850 plus grains in this tube of putty epoxy”.
I’ll give a more precise description of the end result today but my SWAG is this arrow is OVER 700 grains. I think I MAY have over did it, LOL!
yours in the home-made lab-or-a-tory!
PS……..740 grains or a bit over. YEP…..OVER did it a bit …BUT IT FLYS GREAT! Oughta work. Hope the putty epoxy was a help to someone.
- You must be logged in to reply to this topic.