Bow efficiency?
 

What formula is used to determine the efficiency of your bow?
If this is important information why is it not included with the purchase of your bow?
How can I use this information to super tune my bow?
How can you alter or tweek this efficiency?
A big thanks to everyone!

RE: Bow efficiency?
 

If anybody hears from " Len in MD" maybe you can guide him to this post?

RE: Bow efficiency?
 

bump

RE: Bow efficiency?
 

mlaubner, I hope someone in the know stops by and answers this, as it' s something I' ve always wondered about and kept meaning to ask but always forgot...

Board' s been kind of slow lately, hopefully it will pick up soon...

RE: Bow efficiency?
 

I think most folks are getting ready for the big " opener" in a few days.:)

RE: Bow efficiency?
 

I guess I am a little lost by your question. Are you asking how efficient the bow can transfer energy from the bow to the arrow? If so, a lot would depend on the weight of the arrow. A bow would be less efficient on a very light arrow (say 5 grains per pound) as compared to a heavier arrow (say 9 grains per pound). On the lighter arrow, the energy not used still has to be expended through different medians such as shock, noise, vibration, etc.

RE: Bow efficiency?
 

I' m not sure if I comparing apples to oranges, But I' ve wondered how we can get 65-70 ft/lbs of energy out of a 65# draw bow.

RE: Bow efficiency?
 

DaveC, that shouldn' t be too hard. I shoot 70 lbs, a 2514 arrow that weighs 560 grains at around 230 fps and I' m at 65.796 ft/lbs. And that' s with soft cams. Any hard cam bow or single cam bow should be able to get you there pretty easily. Trick is, getting both speed, and arrow weight up there. Are you sure you' re not getting that kind of KE now?

RE: Bow efficiency?
 

mlaubner, I have some info about bow efficiency at the house. When I get home this evening, I' ll look it up and post it if it' s useful.

RE: Bow efficiency?
 

Thanks, I really appreciate it.
In my tinkering I have found a website that requires you to enter your bow efficiency to acquire some other info.
Here is the link http://home.att.net/~sajackson/archery2.html
Also, what is SE/PDF ratio? and how do you determine " virtual mass" ?

HELP!:(

RE: Bow efficiency?
 

Danny45, yes I' m up there now. The last time I shot through my chrony I was at 70ft/lbs k/e with a 426 grain arrow going 272fps. That is with me pulling 65#.

The question I have is 65# the same energy as 65 ft/lbs?
I know I' ve learned this some where along the way and feel kind of silly asking, but I just don' t use this stuff on a daily, yearly basis- so therefore I have forgotten.
I remember from somewhere way back about the " perfect machine" would have 100% efficiency. You' d put in exactly what you got out with no loss.

RE: Bow efficiency?
 

What you really have to do is plot out the force draw curve for your bow to figure out how much energy the bow is storing. Then shoot through the chrony and weigh your arrows to find out how much energy is going into the arrow. Then you divide energy out by energy stored to get efficiency %.

Compounds store a lot more energy than their draw weight. Otherwise, I couldn' t get 62 pounds of energy out of my bow at 60 pounds draw weight.

And, like Bob said, efficiency will vary depending on arrow weight.

RE: Bow efficiency?
 

How is this done???

RE: Bow efficiency?
 

You get a piece of graph paper and set up a graph. Draw weight on the side, one square per pound. Draw length on the base. One square per inch. Start the draw length at your brace height.

Then, using scales and some way to measure, like an arrow marked in inches, start at brace height and check the draw weight at each inch of draw. It is VERY important (and practically impossible to do by hand) to maintain the pull cycle all the way through the letoff and through the valley.

When you get the points plotted and draw out the line on the graph, then you count the squares under the line and that gives you your stored energy, each square is one pound.

While you' ve got the bow on the scales, you can measure the whole thing through the letdown cycle and plot that line as well. That tells you how much friction you have in the system (static hysterisis) which is also an indicator of how efficient your bow is.

If you' ll look at Norb Mullaney' s bow reports in Bowhunting World Magazine, then you can see how to set up the graphs. I' ve got most of his terminology figured out, but I' m still stumped on what the dickens ' virtual mass' is. :)

RE: Bow efficiency?
 

It sounds like I need to buy a " Hooter Shooter" or some device like that. I really would like to have one but don' t have the money to invest just to determine my bow effeciency.
Well, maybe I can start my new home business by having folks bring their bow by the house and I can determine their bow effieciency.
I had no idea this would be so difficult. And on top of that your % number would change with every change in your equipment of set-up.
I could have regular customers for that hooter shooter!
Maybe that does justify the purchase. I think I' ll run this one by the wife!

Now where to find that " virtual mass" indicator.....

RE: Bow efficiency?
 

Mark:

Let' s see, you asked me via private message to respond to your question and then state that you want to

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start my new home business

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. Hmmm, I' ve got Bass Pro Shop just 7 miles away, Dick' s and Sports Authority within 2 miles of my shop, several ' Marts' within a few miles, about 6 or 8 archery shops within 15 miles (some of which operate out of their houses), and you want me to help you compete with me??????[:o]

Might I suggest, since you' ve never been by my shop, to stop by to introduce yourself. There are several others here on this forum who have visited from several hundred to several thousand miles away. I' ll buy you a drink and we can discuss how I can best slice my wrists.:D

Really, I' d be glad to discuss this issue in depth. It would, however, take a VERY lengthy thread to explain how and why I compute efficiency MY way. I know Mr. Mullaney personally and know why he computes the way he does. I just have different theories and methods. My way incorporates the variances that have been discussed above.:)

RE: Bow efficiency?
 

Len--

Sounds like they' re (the mega stores) closing in on you! Put the wagons in a big circle my friend! Shoot till you run out of ammo!:D:D[&:];)

AND---

Boycott those manufacturers who sell to the " marts" and other mega-box-stores. I' m doing it aggressively starting in 2004 myself no matter how irritating and costly, and I know many other true " Pro shops" that are also. Strength in numbers to defeat the " beast" that is trying it' s best to destroy our industry. [X(][:@]

Back to the subject----

Art explained it well as to the best way to initially find the figures you are searching for. Bow efficiency has many variables as stated by Len, and I like he and Norb and Emery Loiselle(whom I know personally also) have my own formula for determination while subjectively focusing on these variables. As Len stated, it can get very lengthy, and unfortunately it is now my busiest season and I don' t really have time and/or really the inclination to get that far into it either to be honest. Good shooting, Pinwheel 12

RE: Bow efficiency?
 

Had an interesting conversation with my pro shop owner about this last year. He believes that wal-mart carring bows is a good thing. His reasoning is that if wal-mart can get you into your first bow, he will get you the rest of your bow shooting life. I guess its just a different view.;);)

RE: Bow efficiency?
 

PW: I don' t think anyone can ignore the mass merchants. Learning to deal with them and how to work with and around them might be a better strategy. I did a seminar on this subject last year at the ATA Trade Show. We recognize their strengths and weaknesses and, believe it or not, they recognize ours. They actually send us a decent amount of business. They do this because they realize that they look better in the customers' eyes by directing them to someone who can meet their needs rather than just turning them away.;)

It would be impossible to boycott the manufacturers who sell to them. If you think about it, you could ' cut off your nose to spite your face' . [:o]

Mlaubner/Mark: Thanks for stopping by the store Saturday. It certainly was a pleasure to meet you and share some information/stories. Hope to do it again soon.:D:)

RE: Bow efficiency?
 

Len-

The mass merchants have no " strengths" other than how to make money. They are locusts that feed off of our industry, but have no care in the world for it. Sending people to you is a tease for complacency. Anyone who thinks differently is either a mass merchant themselves or is getting greased by them IMHO.

What will happen to our industry over time if the mega merchants drive the mid sized and even smaller REPUTABLE Pro shops out of business with their " buy in bulk" BS? Certainly there are not many if any who can compete with the substantial price breaks mega stores receive. If this continues they will ahve no choice but to bow out... I feel such breaks at retail level are very detrimental to our industry---a retail outlet is a retail outlet, doesn' t matter if they sell one or a hundred items, they should receive the same pricing IMO. IF they want to step up and pay the associated fees/taxes/overhead/etc to become a full-fledged distributor who deals wholesale to other dealers, then fine, price breaks should be there, but I have a sore open wound about these " buying groups" , major chain stores, and " outfitters" , and all of that other nonsense that comes with them and them getting price breaks for buying in bulk. Geographically speaking and according to populace numbers determines alot as to how many items a certain dealership will sell in an area, and if they have been in the industry X amount of years they have more than paid their dues by hanging with it, (let alone the knowledge gained) and should receive the same pricing for their products as the new shiny Wal-Mart that has been next door or within a certain radius for 6 months, irregardless of who buys what or how much.

Further, what will happen when all of the true " Pro-shops" with dedicated technical people who have been in the industry many decades and actually KNOW what they are doing disappear? What, people will get their equipment tuned at Wally World, Dicks or Bass Pro by the resident " tech" college student who is working there for the summer? HAHAHAHA. No, the mega stores are nothing more than a thorn that needs to be removed.....quickly. Along with all of the " buying groups" too IMHO.... Big bunch of BS...." pay up and buy stock to receive best pricing and protection" ? Didn' t the Mafia do that? Wasn' t that illegal? Same thing here... Just another way to line certain companies' and orgs/maufacturers' pockets if you ask me, and I will not have anything to do with that. VERY sore subject here that I' ve watched develop for the past decade and the incentives just reel certain dealers in without giving thought to anything other than the savings...money isn' t everything, the sport itself is what matters most, along with it' s future. It certainly isn' t heading in a good direction if you ask me with this garbage happening.

I already have others who are joining this fight and who will boycott strongly against certain manufacturers who cater only to the mega stores, and soon more will join in also, make no mistake there. The eyes are being opened.. Manufacturers will either cater to true Pro shops who are the backbone of the industry, or they will be gone and that' s the bottom line, along with those who wish to help them destroy our industry. Bow manufacturers know this as well----you cannot go to Wally World or other major box stores/" outfitters" and buy a Hoyt, Mathews, Parker, Bowtech, Merlin, Kodiak, or Diamond, along with many others. You also cannot get Copper John, Kodiak, HTM and many other sights for example, and then we have the other accesories and clothing, broadheads, stands, etc. who do not. We WILL win over the long haul. Might take some time, yes, but it has to start somewhere. Good shooting, Pinwheel 12

RE: Bow efficiency?
 

That sound you hear is me clapping!!!!!!!!!!!!!

RE: Bow efficiency?
 

Ok, everyone...I had the absolute pleasure of meeting Len in his shop on Sat. afternoon. I do not have enough time to type the accolades, but suffice it to say that Macrotech as a shop and Len as the leader of the pack, are without a doubt, the finest pro-shop I have ever seen in my life!
Every tune-up tool and gizmo know to modern man.
The level of professionalism is first class.
If Len and the people at Macrotech can' t fix or tune it, it can' t be done!
If you need to drive an hour+ to get there...go.
I would gladly make the trip. In a word...Unbelieveable!:D

But back to the original question...." What I learned Saturday about bow effeciency"
The short version goes like this: For each pound of bow draw weight, you should get 1 pound of kenetic energy. This would be your end result, in a perfect world, if all your components are perfectly matched, etc.

Using my bow as an example: 386gr arrow @252=54# K.E. off of a 63# bow= 85% efficiency.

So to increase my bow efficiency it appears as though I would have to tweek my arrow weight:speed ratio so as to affect my KE number to get it higher. Right?

RE: Bow efficiency?
 

Ok, now I' m confused... How am I able to get over 70' #s of KE out of a 70# draw bow?

RE: Bow efficiency?
 

This area is where BowTech shines bright:D My Pat Dually and Pro 40 both produce close to 10 foot pounds more of K.E. than the peak weight at 29 inches draw length. Short draw archers can take advantage of better engineering for increased performance and accuracy. You can simply find out for your self what your bow is doing with a chronograph and a scale to weigh your arrows. If you get 60 ft. lbs. of K.E. with a 60 pound peak compound bow, you' re doing ok but you can get more;)

RE: Bow efficiency?
 

From what I understood, the 100% bow in an enigma, only exists in utopia and has never been held by human hands.
The object was to try and get as close to this as possible...I think.
Again, my impression, was that it was an impossibility in reality but a goal to try and attain.
It almost sounds religious.;)

RE: Bow efficiency?
 

I had a HUGE post discussing the topics that Len and PW had mentioned unofrtunately if you don' t put in a subject line , when you hit reply, it goes to a blank screen asking if you want to go back and if you do, all of your post is gone! [:@][:' (][>:][X(]

I just would like to mention quickly (especially to Len) that when I was home in Northern VA I went to a local Mass Merchant named Galyans. Theya re an upscale outdoor sports merchant. In thier archery section were about a dozen brand new PARKER bows! UL' s, the mid price model w/ the camo grip, etc. Surprised the hell out of me. Might wanna give the crew down in Mint Springs a call Len[8D].

Suffice to say, With the Free Market Economy our country is based on, the small business owner is going to HAVE to learn how to deal with and counter the mass merchant (or fade away). I' m sure back in the early days of the 20th century many five and dime store owners had a friggin fit when Woolworths hit the scene.a speople do now w/ Wal-Mart.

Right or wrong, it' s the way of life here in tehse United States. It' s very tough for the little guy, but I sure as hell wouldn' t like the alternative. I' d rather not stand 8 hours in a line freezing my butt off for some Government Issued Toilet Paper, Bread and a pack of Thunderheads :D[:-]

RE: Bow efficiency?
 

I' m not 100% up to speed on this topic, I must admit. BUT, I do know this: the area under the force/draw curve is the stored energy available when you reach full draw. It is measured in FOOT-POUNDS. (Not just pounds.) That means that the FOOT component contributes along with the POUNDS component. (i.e., you can get an energy total higher than the pounds of pull because the energy is a product of pounds over distance.)

How " efficient" your total system is depends not just on the design of the bow, but how well your arrow can absorb the energy that the bow releases during the shot.

I think I remember learning somewhere that the most efficient compound design is a wheel bow. It seems like the wheels provided the best mechanical advantage, storing more energy for less work. This does not mean they' re faster. The area under a " hard cam" curve is greater, and the cams store more energy, BUT you' ve got to pull up a MUCH steeper force/draw curve. This means that they' re less comfortable to draw, etc.

RE: Bow efficiency?
 

Rangeball, because your bow STORES more than 70 pounds of energy as you draw it. You don' t just put 70 pounds of your muscle energy into drawing a 70 pound bow, especially one of the new cam designs that hits peak weight early and holds it until nearly full draw.

The longer the draw length, the more energy it stores. The lower the letoff, the more energy it stores. Someone with a short draw length and high letoff will likely never get 1 ft lb of energy per every pound of draw weight. Someone with a long draw and low letoff would likely get more than 1 ft lb for every pound of draw weight.

Mark, I' m sitting here looking at Norb Mullaney' s bow test report for the Browning Eclipse. At 30" draw, 60 pounds, 75% letoff, it stores 70.55 ft lbs. At 65% letoff, it stores 71.78 ft lbs. At 65% letoff, it shoots a 400 grain arrow at 244 fps for some 53 ft lbs of energy. It shoots a 500 gn arrow 222 fps for just under 55 ft lbs. It shoots a 600 gn arrow 207 fps for just over 57 ft lbs.

This bow, at 30" draw, NEVER hits 1 ft lb for every pound of draw weight. As you can see, increasing the arrow weight does make the bow more efficient, but at the cost of arrow speed. IF your bow showed the same KE gain as the Browning, 2 ft lbs for every 100 grains of arrow weight, then you might get 63 ft lbs of KE into your arrow by jumping weight up to 836 grains. Doubt you' d want to do that though.;)

I believe strongly in heavy arrows and momentum, and think KE is secondary in importance and highly overrated when it comes to penetration, but there is a limit to how much speed I' m willing to give up.

RE: Bow efficiency?
 

Thanks Arthur P, Your example illustrates what an enigma the " efficiency" number can really be.
I guess you have to find a happy middle ground with as high a % as is practical given your particular shooting needs.

It has been quite a learning experience along the way.

Now, how do I put the lid back on this can of worms?

RE: Bow efficiency?
 

You' ll probably have to encase it in lead and bury it under 30' of concrete. :D

RE: Bow efficiency?
 

Shouldn' t be any worms here, it' s something you can compute with hard numbers and measurements. Now for the Walmart thing, they are here to stay and it would be best to learn to educate the new shooters and hunters that the true pro shop can offer more advantages. Trouble is that the true pro shop is very scarce and the not so pro shop usually scares away those who know better.

RE: Bow efficiency?
 

Ok wwag, Which numbers do you use and what do you measure?

RE: Bow efficiency?
 

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Sending people to you is a tease for complacency. Anyone who thinks differently is either a mass merchant themselves or is getting greased by them IMHO.

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PW: When they first opened, yes there was a " tease for complacency" . They called in all the local shops and told them the same thing. Trust me, I saw through that ploy immediately. I don' t, however, get " greased" by them and really hope that that comment wasn' t directed at me. Knowing me as well as you do should, I think not.;)

Mark:

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I guess you have to find a happy middle ground with as high a % as is practical given your particular shooting needs.

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That' s about how I related it to you, but with a slight twist. What I was trying to relate was a happy medium between speed and KE. While you might be able to get more KE with a heavier arrow, you have to consider how much speed you' re willing to give up. It is our opinion that 6 grains per pound usually gives you a happy medium. With an established arrow weight, you can then proceed, using the relative numbers of KE to poundage, to raise your % through tuning. With my bow' s efficiency, it is not difficult to achieve 1.1 or 1.2::1. I' ve seen similar set-ups that would only get .9 or less::1. I' ve also seen some set-ups get higher than 1.2::1; but, the draw cycle that you have to accept is NOT to my liking.[&o]:(:D Remember what I said, I' m a HUNTER and I want a smooth draw cycle when I have to draw on Mr. Big while he may be looking.:D:D

Jeff: The people at Mint Spring know exactly how I feel. Their sales are way down in my store since the local mass merchant started carrying their line. This is in part by design and is also by default. They sell the bows at about 12% less than us; but, more customers are finding out that they' re getting about 50% less service. You should see the expressions when I have to charge those customers to straighten out the ' messes' that have been created. The charges usually override the savings by a substantial amount. What should be bothering the manufacturers is the bad taste that archers get when set up incorrectly. Think about how many either enter the woods ill-prepared or give up the sport because of frustration. Who gains and who looses?[:' (]

RE: Bow efficiency?
 

mlaubner, I simply shoot my chosen arrow through the chrono and then weigh the arrow. My present deer stomper does 254 fps with a measured 540 grain 2315 XX78 tipped with a Muzzy 115 grain head. 254x254x540 divided by 450240=77.38 foot pounds of K.E. from a 29 inch draw and 66 pound bow. I really like the way these heavier arrows perform with this set up compaired to my 457 grain carbons. The bow is quieter and has less vibration, just what I' ve found to shoot with extreme accuracy:D

RE: Bow efficiency?
 

Len-

No, that reply was not directed at you in particular, just a general blanket statement.;) We can certainly discuss this more at the ATA, I' m sure some of the buying groups/backing manufacturers will be looking to hang me there anyway, so I won' t be hard to find! hehe :D As you already know, that is a VERY sore subject with me, and I' ve been round the block with it on more than one occasion lately with many people. Good to see others' opinions here as well, and surprising how many do actually agree with me on this issue if they stop to think about it for a minute. There is plenty of support... No need for us reputable dealers to be sheep lead to the slaughter for anyone or anything, we' ve already paid or dues well in advance.... Like I said they try for complacency, and that is nothing more than a tactic of preying on the weak. People are either leaders or followers, I for one prefer to lead. Especially when it comes to beating something that is directly affecting my livlihood.... significantly.

So if I got the subject off track guys, sorry-- hit a nerve, that' s all. Vacation in another month! Whoooohooo![&:]:D;) Good shooting, Pinwheel 12