String angle

[gfugal]

if I have a 64" straight bow and a 64" recurved bow, the recurve bow doesn't END it's draw longer, it begins the draw as a shorter bow.

So,  say the recurve takes effectively 2" out of the braced bow length.  As a proportion of the total, slightly shorter limb applies LESS leverage at the limb base than before, but the midlimb feels a LOT less.....at first.  Then, when the limb effectively lengthens later in the draw, the BOW is still getting shorter, but less dramatically because of the recurve.  The recurved tip thus continues to apply good leverage to the limb base, and BETTER leverage to the midlimb than early in the draw.  This is where the F/D benefits and lower "stacking" come in to play.  Non-contact recurves and R/D bows share this benefit, just less so and at lower angles.

+1
It's the net length of the lever from the string contact point that counts. Basically, a recurve "stacks" early in the draw: it has a higher draw weight than its length suggests, because early in the draw the recurve doesn't contribute to the effective lever length. (hence the high early draw weight: you're drawing a shorter bow, but it lengthens during the draw).

Basically, you can view the realized lever length (if you keep the bow vertically) as the net vertical projection of the bow arms (including recurves if any). Moment = force times lever length. The shape of the lever (recurved or not) doesn't matter for a particular draw length. Since a recurve opens up during the lever length changes in a different manner than with a straight bow, as explained by Springbuck.

+1 as well,
Would you say that my summary "recurves bend the working limbs farther at similar draw lengths while still maintaining good string angle, thus creating more stored energy." agrees with what you guys are saying?

[gfugal]

I think our confusion Is we don't have a universal reference point. Here are three potential reference points I drew out in a sketch.


PatM and a picture from one of the TBB say it's reference point #1 the average of the limbs or something. To be honest, this reference point makes the least sense to me, but as Badger was saying it might be the most accurate to what leverage the limb feels or something. Pretty sure I butchered that summary since I don't quite understand that yet. It just seems to me the angle change between a recurve and non-recurved limbs isn't that significant with this reference point. The 2nd reference point I just made up and hasn't been discussed here yet. The third is the reference point me Simon, and Geroge seem to be using. Maybe there's another reference point not illustrated.

So I just realized this photo wasn't showing before (dang google photo and it's privacy settings). IT should be visible now. That might explain George's confusion when I was talking about reference points. Sorry about that.

[George Tsoukalas]

Green curved line. Top limb. Last photo.

[George Tsoukalas]

Not shown ...second to last photo.

[PatM]

I don't think Don is going to get his recurve string angle question answered on this thread at this point.

[DC]

I am realising that everyone(except maybe Jawge ) is just as unsure as I am. I'm not even sure how important it is. Sometimes though, an insignificant piece of knowledge can lead to huge gains. I sometimes wish that I could sit down with my old physics teachers and discuss this kind of thing but they're all dead now. They had the ability to put stuff into plain English. I think the difficulty comes with the fact that because the limb is bending things are changing constantly and out drawings are only freezing one moment in time. Maybe if we took a video of a recurve being drawn and then measured these angles in each frame some kind of order might come out of it. 

[George Tsoukalas]

LOL. This will be the third time I've defined how I view string angle, PATM.
Pg 1 Photo 1...
It is the angle represented by the string and the red line which does not quite intersect the string but would if continued. The angle appears to be 90 degrees.
Jawge

[DC]

Do you mean this angle George?

[PatM]

 That would mean recurving increases string angle.    You can determine that from the other diagram.

[Marc St Louis]

Wow

[George Tsoukalas]

Yes, DC. Jawge

[DC]

If I erase the first post will this whole thread go away?

[PatM]

 Try comparing the angles of the straight limbed bow and the recurve the way George thinks it should be measured.  Let me know the numbers.

[gfugal]

If I erase the first post will this whole thread go away?

Hey now I've put a lot of effort and time into this post with all my diagrams. I don't know if anyone understood them haha, but at least they're out there for now for others nonetheless.

[Badger]

  I think DC has an answer but doesn't want to accept it. There is no single string angel. Any point you measure it at will be different. The lower it is overall the better your fdc will be. Recurves do improve string angle greatly at the nock and curve area. Other types of bows like DR for instance may have a lower overall average string angle. The recurve still has a significant advantage because it is effectively shorter early in the draw and gets longer as you draw it further reducing the rate of weight gain. But the string angle is what it is wherever you decide to measure it at and you have to decide where it is most important on the particular design you are working on. If you only had a 2" radius curve right at the tip of your bow the string angle would be very low at that one point but overall not much.