I know that compounds are not 100% efficient, I realize that w/ cams that create letoff, energy lost through vibration, heat, et..., no compound will ever see 100% efficiency, So my question is, how efficient are recurves and longbows?, are they closer to 100% than compounds, my mind tells me no because of arrow speed, trajectory etc... but then most arrows shot out of recurves and longbows are much heavier than what it shot out of compounds, I know energy will be lost in some vibraton and I am sure that the limbs have to take away some efficiency. This might be a dumb question but I am housebound all day due to rain kinda getting bored.
What you're looking at is energy into the system vs. energy out of the system. You could compare the three types side by side if you had three bows that took the same amount of draw force to get to the same anchor point. There are a lot of factors involved that make bows even within the same type more or less efficient than each other but in general a compound is more efficient than a recurve and a recurve is more efficient than a longbow.
Ok thats kinda what I was wondering, in my simple mind I honestly would think a 40 lb, recurve would be just as efficient as a 40 lb compound if not more due to all of the moving parts that could take away efficiency from the compound. But I generally do not try to take on these types of ideas as it generally makes my head hurt a little.
I disagree. Compounds are still in the 80-85% efficiency range depending on the arrow weight. The big difference is the draw force curve which the compound excels. Why do you think they need all of the vibration dampeners,silencers, etc.
So are you saying that a 60# compound takes less lb./ft. of energy to draw than a 60# traditional bow? I could see that from the mechanical advantage of the eccentric but if that's the case, in order to compare apples to apples you'd have to compare a higher # compound so that energy (lb./ft.) in = energy in across the board, in which case the compound is going to excel at energy out. Point is that I don't think there's a traditional bow out there that at 60#'s of draw weight can propel a 300 grain arrow at 290 fps but there's a lot of compounds that can. Why, if not because of the increased efficiency due to the mechanical advantage of the compound? I'm about as clear as mud on this myself right now.
Rob. If you take the cams off a 60lb compound and string it up like a recurve or LB there is now way your gonna be able to draw it back as it works out to be around 600lb draw. Which is the reason compounds smoke trad gear for speed, the only way you can draw it back is because of the mechanics of the cams working together with the string and cables, simular to a pully system which is the exact way a compound works. As for efficiency I would say based on the above trad gear is more efficient in terms of power in power out.
Nope, not at all. The compound will have more stored energy and more kinetic energy. The transfer of stored energy is what makes the bow efficient. Efficiency = Kinetic Energy/Stored Energy. Below is a real ugly roughly scetched draw force curve which will show the draw force of a compound, recurve, and straight limbed longbow. As you can see the compound excels in stored energy.
"So are you saying that a 60# compound takes less lb./ft. of energy to draw than a 60# traditional bow? " No, not at all. If fact, just the opposite is true, a person will have to put more energy into drawing a compound then a traditional bow. A compound will clearly have more stored energy and more kinetic enery. But the efficiency of the bow has to do with how well the bow transfers the stored energy to the arrow. Efficiency of the bow = Kinetic Energy/Stored Energy. Like I said in a previous post, the compound will excel in the draw force curve and will produce much more stored energy then the traditional mainly because of how early in the draw cycle the bow reaches and maintains its peak draw weight. Below is one ugly draw force curve that I sketched up.
I know this kind of strays from the original intent of the post but, as compound technology advances....where is there more room to gain energy out? Through the efficiency of the bow, or thru maximizing the draw/force curve?
Pretty good article for those interested: http://www.bowhunting.com/publish/posts/23/understanding-compound-bows.aspx
My fiend has I believe a cam and 1/2 bow (Darton). Syncing that one up is a piece of cake. I remember syncing up the older two cam systems (back when they used actual cables and nuts and bolts), those were a little more difficult. rybo, I think the draw force curve is peaked out now on compounds. Higher efficiency levels will be tough to come by with materials used today. I don't honestly know what is left without further mechanical advances. Maybe some sort of locking/unlocking system that will give the benefit of a pully type system on the draw, unlocking the pully, and giving the full benefit on the shot. For example, pulling back 40 pounds using the pullies, unlocking (maybe rolling over) the pullies at full draw and getting 70 pounds upon release. I wouldn't want to let up on the shot with something like that tough.
