Riser length and other things that effect performence

"Its not string angle but the string angle shows what the entire bow is doing."
   Steve can you explain in more detail??

"String angle wins that argument in the math, it's very easily demonstrated in T=mg/2sin a. With relatively simple math we can also see that the more working material involved the energy stored goes up. Math always wins, or at least tells us what wins."
  Die, can you also explain in more detail, maybe through some examples?? I am not familiar with that math equation... how does it apply or work??

[die_dunkelheit]

Sure Shredd, I've been meaning to put all of that in one document to share here but I've been pretty busy lately, barely enough time to get my tradgang fix everyday let alone shoot my brand new bow...  :(    
As soon as I get a moment to sit down and organize it all I'll post it.

Cool...  Thanks... Always trying to gather as much info as I can...

[Sixby]

I agree that compounds and recurves have little in common but some things have correlation even if remotely.
For instance, Stored energy is useless if not taken advantage of. efficiency. Limb movement enters into this. Ergo although using high poundage to make up for length of limb and storage as does a recurve, the compound return to brace is exceedingly quick due to very short string travel and angle.
I can and do apply that to the recurve by decreasing string angle and shortening working area but not to the point of limb longevity.
A mimic of the cam or wheel on the compound is the fairly long hook and static tips which can be employed to accomplish some of what the compound accomplishes. We can take the limb movement from brace to full draw to only a couple of inches . This makes for a very quick return from full draw to brace upon release and actually approaches achieving in performance what the early wheelies got.
So we may be looking at different things but I make it work with my bows as did several early bow builders , especially Damon Howatt and Martin. In this design the wedges and riser compose 26 inches and the static tips 14 inches for 50 inches of a 62 inc bow. yet you see no over bend. The limb travel is only a couple of inches and though measuring exactly  62 inches from notch to notch the string length is 61 inches for a brace that is tight and stable. There is only 12 inches of free working limb.
 
God bless and Merry Christmas to all, Steve

[arachnid]

Steve, does low string angle and short working limb apply to a reflex/deflex longbow design or only recurves will benefit from it?

And, is there a benefit to attaching the limbs to the back of the riser?

[Sixby]

It applies to all bow designs including longbows and D and R bows. Low string angle is simply a sign of how much limb movement there is between brace and full draw. But it also has other benefits with less finger pinch, aberration in string to arrow position as the limbs return to sync at the shot. Less vibration ect.
In attaching the limbs to the belly of riser as shown the string is actually closer to the limb at brace but the reflexed riser gives you decent fletch clearance and better control ability.
 I cut all bows 3/16 past center so there is not really much paradox so that is not a consideration when setting brace height. You have to consider wrist clearance and fletch clearance and that is about it except for adjusting all for max stability at brace.
All this said, there are more ways to build bows than you can skin a cat and I am not saying at all that my way is right for everyone or will even work for everyone. But it works for me.
As to top mount and belly mount bows I shoot both equally badly and can build either to be within a couple fps of each other so its a matter more of what a person likes esthetic wise and can shoot best.

God bless and Merry Christmas to you all, Steve

[Tdonns]

mikkekeswick said: Look at tuning forks...

Whoa. You threw me on that one. After reading that line my assumption was that thicker tuning forks would create a lower frequency (Hz) than thinner forks. Soooo off to the internet I go.

f=.162/(L*L)*v

f is the frequency or Hertz
.162 I guess is the common
l = length of limb squared
v = the velocity of the medium

Running the numbers reveals the ahh haaaa moment for me! Shows you what I know about music and tuning forks.

Yep, thicker is faster, or higher frequency.

Thank you mk for throwing out that fact. It'll help me with my adventure into Bowyerism. Is that a word? Sounds kinky.

Tom

[Sixby]

MIK:Also glass 'indestructibility' allows you to almost forget 'tiller logic'. Eg. pyramid - arc of circle tiller, parrallel width limbs only tapering in width near the tips - elliptical tiller. This is very important to having an efficent bow.

I hate being so disagreeable but I do disagree with this if I understand it right. The most efficient and quickest bows I have seen have a full length taper. For instance the Ballistic tips. They are tapered from EOR to tip. Bigfoot b ows which rate in the 90 plus percentile and are super quick have a full length taper. My bows have been built both ways and the most efficient I have built and the fastest all have had a full limb taper.
Also the indestructability of glass has nothing to do with negating basics of good tillering which includes timing the limbs and smoothness, Size and placement of working area.
It certainly does not mean that you can throw anything together and come out with a good bow. Perhaps a bow , But not a good bow. If you build a good bow , and most of us do , we pay as much attention to tiller  as self bowyers do. At least this one does. This is not just for performance sake but also so that the bow will live a long time.

God bless, steve

[Sixby]

MIK:Also glass 'indestructibility' allows you to almost forget 'tiller logic'. Eg. pyramid - arc of circle tiller, parrallel width limbs only tapering in width near the tips - elliptical tiller. This is very important to having an efficent bow.

I hate being so disagreeable but I do disagree with this if I understand it right. The most efficient and quickest bows I have seen have a full length taper. For instance the Ballistic tips. They are tapered from EOR to tip. Bigfoot b ows which rate in the 90 plus percentile and are super quick have a full length taper. My bows have been built both ways and the most efficient I have built and the fastest all have had a full limb taper.
Also the indestructability of glass has nothing to do with negating basics of good tillering which includes timing the limbs and smoothness, Size and placement of working area.
It certainly does not mean that you can throw anything together and come out with a good bow. Perhaps a bow , But not a good bow. If you build a good bow , and most of us do , we pay as much attention to tiller  as self bowyers do. At least this one does. This is not just for performance sake but also so that the bow will live a long time.

God bless, steve

[die_dunkelheit]

Sorry for my absence here gents, I almost died last week and spent several days in the hospital and am still recovering at home. Nothing that will keep me from archery, and not even really have any lasting affect, just a hill to climb to get better.

Sixby,
I 100% agree with you that potential energy is nothing if not used, and that has been the flaw in my argument so far. However, right before the aforementioned sneak peek at paradise, I started thinking about a different aspect that we haven't discussed.

Just as in a spring, when an elastic material is deformed (your bow limb being bent) the energy stored goes up at a fairly linear rate until a point, depending on the material, when the rate energy is stored at drops substantially until rupture. Just like springs are efficient until over compressed or overstretched, then their efficiency goes to sh*t. So perhaps the best approach is finding to what extent your material can be deformed before the rate of energy storage declines, then use that information to tune riser and limb length to get the best efficiency.

[Archer Dave]

Dang Dunk, glad you are still alive. Hope you are recovering ok.

I hope this conversation continues. I enjoy reading about the design aspect. I also would be interested in the equations when there is time and you feel up to it.

2x Dave... Waiting and curious....  What happened to you??

[die_dunkelheit]

Thanks for the kind words guys.
Here are the details, though maybe a bit too detailed...

I couldn't even hold down water, at one point I puked it back up still cold, even little sips. I'm diabetic btw, and at this point my blood sugar was high, but not crazy high to cause this. At first it seemed like food poisoning. I had chipotle that day for the first time in a year and the meat looked a little funny so it kind of made sense.. Then the puking actually got worse, and it began burning more and more in my throat and down my esophagus. My girlfriend took me to the ER. On the way there I thought a little more clearly about my symptoms and when I sat down to get my vitals checked at admission I just told them I was going into diabetic ketoacidosis ("DKA") and was admitted. In short, DKA is when there are so many keytones in the blood from the body consuming fat stores that the blood pH actually changes.

It wasn't just diabetic ketoacidosis though, between testing at my house and getting tested in the ER my blood sugar went from 300 to 875. A non-diabetic typically runs 80-110 or lower, and you shouldn't be conscious over around 700 depending on the person. They ran more tests and drew more blood than I've ever had done before, even chest x-rays and CT scans trying to find out what else was going on.

Final diagnosis:
I somehow caught what the doctors called "an extremely sever case" of strep throat which caused my blood sugar to skyrocket. In the presence of such high sugars a fungus that naturally occurs in the body exploded and gave me a bad case of fungal pneumonia which also spread into my torn up esophagus. Those 2 things literally almost killed me, diabetic ketoacidosis and a fungal pneumonia.

The troubling thing was, after I wasn't at risk of actually dying anyway, how did I get such a bad case of strep in the first place? It's only transferred through mucus and no one I know has it or has had it in many years. Then last night, right after I got home from my 5 day hospital stay, I remembered something. A few days prior to this ordeal I stopped at AM/PM for some chips or something like that. When I checked out the cashier just kind of tossed it on the counter while simultaneously letting out a single cough, like firmly clearing his throat, and I felt it blow over my whole face. When you think about it, it's pretty gross. I got hit with a wall of mucus droplets from the AM/PM guy's cough and that almost killing me and put me in the hospital for 5 days. Thanks AM/PM guy...

In addition to the actual emergency issues my entire mouth, throat, and lips completely dried out because they wouldn't let me drink water for like 30 hours, well after I quit barfing within the first 2 hours. My lips chapped so bad that they split and bled in probably 10 places. Because my lips were so cracked they thought it looked like herpes and even tested me for it after I insisted I did not. Of course the herpes tests were all negative, but apparently they thought that my throat problems could have been related to a bad oral herpes breakout, after I REPEATEDLY told them "No, it's because YOU won't let me drink any damn water." Though they probably couldn't hear me, my voice was gone because of such extreme dryness. I'm rehydrated of course, but I'm still struggling swallowing food in part from the damage from dryness and also the strep throat. I can basically only eat soup made with chicken broth, noddles, and chopped potatoes and carrots. As long as the carrots and potatoes are VERY soft. Oh, and lots of jello. Lime jello and cool-whip is the best...

[BenBow]

Man I'm glad that's over for you. Prayers for healing

[die_dunkelheit]

Thanks BenBow.
Sorry if that was a bit too detailed lol, it was just fresh in my mind and I was still frustrated.

Shredd, Dave, I'll get to it as soon as I can. It's something that I've wanted to publish for a while now anyway...

Damn Bro...  Glad your still with us...  We need that info...  Lol...
   Seriously... Glad you pulled through that ordeal... Wishing you a quick recovery...