Hickory Backed Ipe Design Help

[deadsilence]

I have a few board bows under my belt now and I have now tried two different hybrids with no luck.  Roy has been helping me along but I am sure that he is getting tiered of me by now.  First hybrid popped three handles off before enough wood tore out to make it useless.  The second one was a BBI trilam that had too thick of a bamboo back and my belly got to thin.  It developed a nasty hinge that i couldn't tiller around to save my life.  

I'm looking for some help in the design department to give me the best chance at success.  Right now i have a ipe lam that is 64" long x 1 5/16" wide.  The ipe is 3/8" thick.  I plan on a 12" centered, stiff handle, but this is up for debate.  The ipe starts to taper in width and thickness 4" from the end of the riser.  The width tapers to 1/2" tips and the thickness tapers from 3/8" to 1/4".  I have pre tillered the belly by clamping the the ipe to a table at the end of the riser and hanging a 10lb weight 2" from the tip and tillered the strong limb till it matched the weaker one (3 3/4" of deflection).  This was done just to get them bending even before glue up.  Seemed like a good idea.  I am planning on a 1/8" hickory backing.

I will be gluing in some reflex and maybe some deflex.  My questions are do this dimensions sound ok?  Do i need a power lam?  If so how thick and how long?  Reflex only? If so how much?  Plus anything else you thing may be helpful at this stage.

Thanks,
Jason

[deadsilence]

Can I do a flat handle and glue in some flipped tips like this?
This is a 2x4 and the curve is 12" from the end of the board.
   

[macbow]

What is your target weight and draw length?
Have never tried to pre-riller like that. Be interesting to see how it comes out of the glue up.

If your draw length is 26 or more inches I would be leary of the 12" handle.
If it was 8 " then that is 4 more inches for the limbs.
If using a 8"  handle then I would suggest a  12" power lam close to 1/4 inch thick in the middle tapered down to 0 thickness at ends.  This will strengthen the fade area and help with the popping of handles.

[deadsilence]

I have a long draw of 28-28.5. And I would accept any hunting weight at this point. So 45lb and above for me . I would really like a sight window cut in so I was trying to keep enough meat in the handle for that. Could we compromise on 10?

[passion for knowledge]

I've made a maple backed ipe and a hickory, maple, ipe tri lam that both came out pretty well, both #47 @ 28"

The attached image shows the handle on the maple backed ipe - the handle is shedua and an overlay of maple. The length of the shedua at the fades is 8" but the fades continue into the ipe for about an inch and a half to, hopefully, eliminate the possibility of popping the handle off.

Just out of the fades in the ipe it is 9/16 thick and tapers out to 7/16" at the tips. An inch and a quarter wide at the widest point - 1in wide handle - tips 7/16" wide.

A bit longer than your design - 69" NTN

Not the best photo I've ever taken!

Hope this is helpful.

 

[deadsilence]

How long is the taper on the ipe from 9 to 7/16

[macbow]

Passion for knolledge has a good point on how the fades going into the IPE.

I guess my question is what do you want a long sight window for.
Are you attaching a sight?  That is the only reason I can think a long sight window would help.

[deadsilence]

No particular reason. I tend to shoot more straight up than most traditional shooters. The 3/8" is what I have currently. would a power lam remedy the no flare belly?

[deadsilence]

Does the curve above look like something that is feasible if I forego the deflex in the handle?

[takefive]

Curve looks fine to me.  You could probably still do a mild deflex at the handle if you wanted to.  I like to have the tips about 2" forward of the handle coming off the form.  I usually lose 1/2" to 1" of that after shooting it in.
I've never used Ipe for that type of bow, always osage.  When I'm done tillering, my thickness at the fades is 1/2"-9/16" for a 45# bow.  Always around 3/8" thick at the tips.  But mine are a bit longer than what you have to work with, 66" tip to tip.

[macbow]

With IPE the thickness can be lower.  The 3/8 " you have will make a 50# bow easily
I make my handles a little,different than most who use a solid block.
I use 1/8" to 1/4" inch slats and glue them on after glueing up the R/D bow.
By using slats I can clamp them to match the slight curve in the handle area. I do the taper after this.
If you go to the longer riser/handle you could make the fades longer and bypass the power lam.

[deadsilence]

Do you have any thickness recommendations for a power lam or a handle with fades built in?  Feather tips, one inch in 1/16" two inches in 1/8"?   How long should a power lam be or a handle with fades built in?

[macbow]

I make my power lams about 2 inches longer than the handle.
All handles need to have the fades built in, some longer than others. My opinion.
My lams I start 1/4"  thick. I glue this to a thicker piece of wood with hot melt glue.

I take it to my belt sander . Sand from the middle out to edge at a gentle slope. Till the end (fade) is paper thin.
Flip and do the same one this end.

Pry it from the sacrificial board. The result is near 1/4" in center fading to 0.

[deadsilence]

Ok so bear with the nerd in me for a second.  if i do a 10" handle that makes the total length of the power lam 14", correct?  If so then doing the math on that, 2" in from either end would be 1/14" thick. A 1/16" = 0.0625 and 1/14" = 0.0714. Is this enough to stop the bending of the fades and keep the handle from popping off?

[macbow]

The power lam adds to the taper on the handle to make it strong enough.
If the fades on the handle are long enough a power lam isn't
Needed.

The idea is the bow limb will bend some through the fade and then the stiff handle will stay put.

Not sure on the math never measured one.

[macbow]

If I can find one I'll post a picture tomorrow.

[macbow]

[macbow]

Hope you can see through the camo etc.
Just below the thin bamboo is the end of the power lamination.
This one is a little longer than needed.
This is a BBI

[deadsilence]

Yes I can see it there.  How much taper is there on the belly of that bow? How long is the power lam and how thick is it at its peak, at the handle and at the end of the belly fade?  I only have a flat 3/8 piece of ipe, there will be little to no taper from the belly to the the handle.  That is why i am looking for information on power lams and how much thickness i need in the fades to stop the handle area from flexing.

[deadsilence]

Ok im about to go full on nerd here.  Besides being a math geek i am also a software engineer.
Why think when computers can think for you?
I am thinking a 16" power lam with a 10" handle block since i have just a flat belly.
Power lam will be 5/16" thick at the max.  Here are the thickness numbers for one side of the lam.
Thickness at -8: 0.0
Thickness at -7: 0.0390625
Thickness at -6: 0.078125
Thickness at -5: 0.1171875 (Handle will begin here)
Thickness at -4: 0.15625
Thickness at -3: 0.1953125
Thickness at -2: 0.234375
Thickness at -1: 0.2734375
Thickness at 0: 0.3125 (center of bow)

How does that look?