NikoTheBowHunter
Well-Known Member
Have you tired FOBs? https://fobarchery.com/ Ive been using them for the past 3 years and love em.
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Arrow Build. Vanes?
- Thread starter Weisman125
- Start date
Weisman125
Member
I havent shot them but I want to like them. In theory they are awesome. I can't get past replacing them all the time tho. I know ease of replacement is a selling point but not something want to mess with.
This is showing benefits to point weight for flight stability.....pushing into the wall is showing benefits to point weight at impact and negatives to nock end weight at impact and also shows how increasing general overall arrow weight isn't really doing anything....weight the pointy endFor all you straw shooters. No sand in said straws though
Sent from up in a tree
GTel
Well-Known Member
- Joined
- Nov 9, 2019
- Messages
- 233
Agreed. And it was a cool video with straws!
Ashby's report talks about how the weight at rear of arrow affects it and uses a brick in his example.
"Extreme FOC arrows have at least two design features which reduce shaft flex on impact. These are:
1. Less arrow mass is towards the rear, reducing the force with which the arrow’s rear “pushes” on the shaft.
This is easier to understand if one thinks of super-gluing a brick to one end of a slender shaft. Now place the other end of the shaft on the floor. Unless one keeps the shaft absolutely perpendicular to the floor, the shaft flexes... " The example continues in the report. Good read.
Sent from up in a tree
Here's a link to Ashby at the P&Y meeting. He demonstrates several of the things being discussed in this thread. It's less than 17 minutes long and well worth watching.
Good video to demonstrate the importance of FOC. Going somewhat back in the thread, the OP is shooting a 29" 340 shaft out of a 68# bow. We have unknowns of bow make, draw length and current total front weight and total arrow weight unless I missed those in the thread. Unless his draw length is greater than 29" he could reduce the shaft length by up to a couple of inches depending on rest. Cut below 28" and you are now changing the actual spine of the shaft, deflection is now going to be less than .340. This opens the door to increasing the front weight without as much fear of being underspined because the label on the shaft says 340. So switching to small feathers rather than vanes may be an option without messing up arrow flight. If on the other hand the arrow needs to remain at 29" the amount weight that can be added to the front of the shaft without tuning issues is limited. If the current arrow has vanes the additional weight limit at the front could be further limited by switching to feathers or it could be slightly increased by adding a small amount of additional weight at the rear from say a wrap or a lighted nock, which would increase the dynamic spine of the arrow. The primary point is Dr. Ashby's work is centered around optimal penetration without regard to system tuning. Building out the system requires considering all the factors affecting arrow flight as well as penetration objectives and a primary driver will always be the arrow shaft selected to build around. While the things Kurt and I were pointing out may not be optimal for penetration, they are the proven methods for potentially keeping an arrow in tune when the arrow spine or deflection was not quite stiff enough to support the desired changes to FOC.
Wait, what? You can change static spine (deflection) by cutting an arrow shorter?
Not throwing stones. Literally just trying to understand this.
I disagree. His top 3 of the 12 points to increasing lethality
#1 structural integrity
#2 perfect arrow flight
#3 foc
GTel
Well-Known Member
- Joined
- Nov 9, 2019
- Messages
- 233
I don't know the difference between static and dynamic spine, but yes, shorter arrow = stiffer arrow. And as little as a quarter inch can make the difference between perfectly tuned and too stiff or too week. My 300sp and 340sp arrows are cut at different lengths (with different tip weights) to achieve the same goal of perfect flight.
Sent from up in a tree
If you cut a shaft shorter than 28" you effective change the actual spine of the shaft. A 340 shaft has a deflection of .340 on 28" center. If you cut that shaft shorter that 28" it will have less deflection at center.
Was referring to the video and my recollection of the emphasis of his writings that I read a bunch of years ago. I agree with that top 3 in that order.
Very interesting! I was always under the impression that the static spine was constant no matter the length of the shaft.
The reason I'm drilling down on this is because I just purchased the remaining Mossy Oak .350 arrows from my local Wallyworld (couldn't resist as they were $2ea). I bought some at 29in and some at 31in. They all had the exact same labelling except for the length (29" and 31" respectively). Are we saying that a given manufacturer has a different building process when constructing the same arrow at different lengths?
No what I am saying is if you put those 2 shafts both labeled 350's on a spine tester, they should both deflect .350 or real dang close even though they are different lengths. What matters is they are both longer than 28". Cut them shorter than 28" and the deflection will decrease. For example if you cut that 350 shaft to say 27" the deflection may be more in the neighborhood of .300.
YotaboyPatrick
Member
Am running an Easton axis 340 as well with a 75 grain brass insert and 100 grain g5 strickers, with the 2.5 inch heat vanes. They seem to shoot like practice points up to 40yrds haven't shot a whole lot past that as far FOC there like 16.5%. You may have a hard time destroying them there a pretty tuff arrow in my opinion.
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Hilarious... I've been wanting to test with a .300 for awhile now to see if I can eek out any more precision from my system but I can't bring myself to purchase more arrows. Well, last night I just cut four of those 31in .350s down to 27.5in. Praise God, He delivered!
EDIT: My system doesn't really need more tuning. The 29in arrows are shooting AWESOME out to 30yds. I'm just the ever-tinkerer that has it in his head that stiffer arrow = more manly.
For my edification, spine is measured by using a spine tester with a 28" shaft? Sorry. I'm not trying to be dense, just trying to understand what my actions (in this case, cutting an arrow below 28") are actually doing to the spine.
To measure spine you would place an arrow on pegs or supports 28" apart. Either force is applied to the shaft or a weight is hung from the shaft at the center of the 28" span. The weight is just a frog hair under 2#. Then the amount of deflection is measured and that is your spine rating for that shaft. Cutting the shaft to a length less than 28 is going to make that shaft stiffer than its measured deflection. Not saying your 350 cut to 27.5 will turn out to be 300 but it will be less deflection than 350. Thats why understanding spine and dynamic spine is important when building out a system.
Boom. Schooled! Thank you!
If it really works out for you then those arrows will show stiff or overspined. Then you can slap some feather on there to weaken the dynamic spine and you also gain FOC, best of both worlds like Mr. Price was talking about. If they show weak with vanes, I would check to see whhere the FOC is and then maybe try adding a wrap or a lighted nock or maybe both as long as you can keep the FOC at a decent point. I prefer to stay above 12% and typically fall somewhere in the 14-15 range. Higher certainly has its benefits but may not be attainable with a given shaft spine and system setup and it still tune properly for perfect arrow flight. Any time I am playing with an arrow setup change I generally will do 2 or 3 arrows as test runs and try to always start on the long side with the arrow so I can shorten to find the sweet spot. Cut too short out of the gate and you have to get another arrow.
Kurt
Well-Known Member
Yes you can
Yes you can. Static spine is taken from the deflection of a shaft supported on both ends at 28". Cut that shaft shorter than 28" and that shaft will be stiffer.As you move the supports closer together the same weight will bend the shaft less. The lower the deflection number the stiffer the static spine.
DUDE! Had another cup of coffee and thought about this again. This is why I was having so much trouble tuning my bow!
A bit of history: Frustrated with the marginal performance I've had for the past year out of my proshop "tuned" bow, I began tuning my own bow a month or two ago with @Gamover06 's help. He urged me to go to a lower deflection but I wanted to stick with my current Carbon Express Maxima BLU RZ 250 arrows (yes, actually a .400 spine) because I had so many of them and they seem to be within spine spec for DL/DW (based on Carbon Express' spec calculations). I added 300gr to the front of them and was COMPLETELY BAFFLED as to why they were showing symptoms of being over-spined according to Easton's guide (thanks @Weldabeast). I eventually gave up on the Carbon Express' altogether and began testing with the .350s I mentioned above and had great results with that same 300gr up front. It was really confusing that the .350s tuned when the .400s showed over-spined.
…… the RZ 250s cut at 26 1/8" weren't really a .400 spine!
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