Something to discuss...

[PEARL DRUMS]

Here are some pics of a new project of mine. PLEASE feel free to comment on anything you see that needs changing, or PLEASE feel free to give me suggestions and cautions. This is all new to me and quite different than my usual bow(s). Its just something Ive wanted to attempt. I had the wood around and just needed to order some Unibond 800 and hardware.

Here is where I am so far:

The riser is 14" long tip to tip - the limb beds are 2.5" long

The portion of limb beyond the riser is bout 27" - hope its enough for  50-50 @ 28"

The belly is 10 yr old 1/4 sawn osage, spotless - soon to be backed with flat sawn hickory, spotless. I pre-shaped and tempered the osage.

Im debating adding a short piece of ipe on the belly of each limb where it seats in the bed, just to be sure the bending stops, basically create thicker fades? I also question if the bed needs to be 2.5" long? Seems over kill to me. Are my limbs long enough? I have a good bit of deflex off the handle.

[PEARL DRUMS]

One showing my limb angle, roughly.

[osage outlaw]

Boards?

[Badger]

  The only caution I would have is right at the cut in for the limb pads. I had a very similar hickory riser let go on me at full draw. I was told that is the reason they usually just sit on top of the riser. I would give it a bunch of full draws on the pulley before shooting.

[Pat B]

Pearlie, my only concern would be the one piece riser. An "I" beam through the riser would add just a bit more security and look good too. Looking forward to the end results.

[PEARL DRUMS]

Steve that was my first concern, I though maybe since the grain was swirly and not flat, it may hold? I should just glue up an I -beam style and not worry about it.

[koan]

This has always interested me. Lookin forward to the finished product. What Pat and Steve said makes sense to me. I think i would split the riser section once or more times and put a tuff peice or 2 of hickory or the like in there. Just my 2 cents.... Brian

[PEARL DRUMS]

Brian I already went through my stash of lumber and found some walnut planking. Ill make an I beam style with 5/8" wide osage in the center to anchor the limb bolts, then walnut on the outsides. That should solve that problem. Seems like osage is always stuck doing the tough jobs?

[Pat B]

Just the glue line(s) will add strength.

[KS51]

I would be a little concerned with the length of the limb beds.  You need to be sure that the tension load on the bolts is within allowable loads. Figure it this way, if limb is 27" and distance to bolt center from fulcrum is 1-3/4" then the tension in the bolt is (27/1.75 x 50#) / (0.059) [approximate root area of 5/16" bolt] = 13,500 psi  which is a safety factor of about 2 for Stainless Steel (allowable stress is pretty close to 27,000psi).  Though geometry of the limb needs to be taken into account, I used 50# just to give an idea of what needs to be accounted for.

I've made 3 attempts at a takedown so far.  I use grade 8 1/4" bolts (yield of 120,000 psi) and I try to get a saftey factor of 4.  My limb beds are 3-1/2" and the lever arm is 2-3/4"

[PEARL DRUMS]

Wouldn't the amount of deflex added change the stresses at the fulcrum? By the way I ordered actual T/D hardware from Binghams.

[KS51]

What really matters is the geometry at full draw.  I would recommend looking up "method of sections", this is the technique I would use to evaluate the forces existing just in front (limb side) of the fulcrum point (1" in front to make the math easier).  Then evaluate the the anchor load from there.

I'm pretty sure the Bingham hardaware is 5/16" bolts, but regardless, the forces need to be evaluated to make sure they are within spec.  I have never used their hardware, so I can't comment on its strength, but I would be surprised if they didn't supply some guidelines about the positioning of it to stay within the safe zone.

[Knoll]

Congrats on launch in new direction!

[bow101]

I like what you are doing.  If its your first attempt I would go a little longer for the limbs say 29".  Limb beds are 2.5" long,  I would at least go 3 1/2" that will give you a better transition more security.

This is how I do it. 30" limbs 30X2 = 60"  Riser 14"  Limb pads 3 1/2" X 2 = 7"
total limb length minus pads equals 60-7=53"
Add 53" to total riser length minus the pads you have total length for bow. +7"  = a total of 60"
The other thing is the grain on the riser it should be opposing.

I think I got that right.......have not finished my 1st. cup of coffee yet. 

[PatM]

Marc has made this style with toilet bowl hardware.  It's the anchoring of the threaded  part that is more of an issue than the strength of the actual bolts.
 BTW I'm disappointed in you Pearlie.