how much to pike HELP!!! (pictures added).

[Russell S.]

ok so i got the new bow on the scale.  68" NTN  came in at 36#  so time to pike.  i center cut it and the window is a bit tall, i don't what to put too much pressure on the riser. so i am trying to wrap my big brain around the physics of piking.  I see it like this the fades stay the same strength, the "lever" (limb) gets shorter there for the draw weight goes up.  force on the riser should be really close to the same, maybe off a little because of the change in tiller and limb angle.  
(1) so piking will increase draw weight by shorting the lever..  but how much...  if i go to 64" I think from reading i should get about 45#   then i can further pike down to 62" to get my desired 50#  i think doing it in steps is the right way..  however i will loss quite a bit of reflex...  how is that going to affect the bow?

(2)I also naturally draw between 29 and 30"  not stacking now at 30"  however once piked stacking might be a problem...  

(3)my draw now is VERY smooth (this is my fist BOO bow),  I don't know if its the shape or boo but its smooth. i assume that the draw will not be as smooth on a short bow  what do you think?  i will got take a picture at brace and with the template on it so you can see the loss of reflex.

(4)It also seems the limb will become lighter, and have less mass where it is moving the most by my figures that should make the bow more efficient. so from the technical bowyer a bow should be a short as it can be to draw to the shooters draw length with out stacking...  is this a key to building fast bows?  

sorry this carried on so long..

[kennym]

Hey Russ,

1.. piking my 64" mild r/d 2" makes 6#

2.. how long is your riser? Mine is 18" on a 64" and no stack to 31". The same bow at 62" stacks after 29"

3...ummm  longer bows are usually smoother,if you go too short,it will become harsher,but I just don't know where too short will be.

4..yes,one of the keys.......

[Russell S.]

riser is 17 inchs

is that from 68" to 64" kenny?

here are the promised pics.

 

 

 

[jess stuart]

You might want to consider adding another strip of glass to the back or belly.  I gained about 20# by adding a .040 strip to a 62" t/d longbow I built.  It shoot good in fact it is probably the fastest longbow I have built so far.

[kennym]

No it started at 64,piked to 62

Looks like you have a lot of reflex left. Guess you can do a force draw curve on it and draw it an inch past where your draw length is so you don't make it stack at your length? Mine went from about 2.75# for every inch longer draw to about 4 #

Just looked at my test paper and it started stacking at 30" instead of 29"  My memory is short!! LOL

[Russell S.]

Thanks kenny i am going to have to find a decent scale i am using digital bathroom scale now...  force draw curve sounds like a challenge on that thing!  might go to walmart get a fish scale need peanut oil for tomorrow anyways! working up a quick tillering tree from scrap forms should not be a problem... Again speed is not nearly as big a concern as shootablity, and killing power (gotta be safely over 40#@28 here to hunt.  (think i want 50-55) for elk next year.  I have killed a few pigs with 22's the key is not power but good shoot placement.  

think i will take it to 64 or 65 and go from there.

[Apex Predator]

Russ, I'm thinking you will probaly need to take her down to 62" nock-nock to get that weight. You many end up with a longbow!  Like Kenny, I gain about 6# for every two inches OAL I hack off.  Taking her down in two inch increments will let you get more data for your little bog book, which will become a treasure for future builds.  I like to record everything I can.  At 62" she should be smooth to 30".