Calculating Taper?

[Kevinnator11]

So I keep getting confused by the numbers on taper.  I think I've figured it out but I'd like to make sure.

Thickness at end of fades being 1/2" or .5 and assuming I wanted around 3/8" or .375 at the nocks would be about .005.  Oh yeah I'm assuming about 24" of working limb.  Got that by subtracting thickness at end of fade by thickness at tip and dividing by working limb length.

I'm thinking that may be high for a tri-lam.  At the moment I have one glued up 62 ntn.  1/8 boo back with 3/16 parallel hickory core and a ipe belly.  I also put a 14" power lam in it.

It's too late for this one but in the future I'd like to taper my core and belly so there won't be as much tillering.  This one is crazy stiff at the moment.  I've got a lot of ipe dust to breathe.

Thanks for any assistance.  I'd like to speed up my process.  
 

[Bowjunkie]

Your bamboo should be much thinner. I cant see the rest of it, but it looks really thick on the end. Measure the bamboo at the center/crown.... it shouldn't be much thicker than 1/8" at the handle area, and 1/16" at the tips. That's really all it takes. That's where the strength of that stuff resides, near the outside.

Then the center core can be tapered about 1/16 - 1/8 give or take in the working portion. The belly lam can be parallel to allow for wood removal during weight reduction and tillering.

[robin]

Just built one like that but my centre core and belly lams are all pre-taper prior to glue up.

This make it bending more through out the limbs after glue up....good luck and post more pix along the way....cheers

[Sam Harper]

Here's the dimensions I have on an ipe bow I finished last fall that came out to 52# @ 28".

It's 66" nock to nock with a 12 inch riser.  There's no power lam, but the fade continues into the limb for a little bit.

It starts off at 7/16" at the end of the 12" riser, then tapers to 5/16" at 3 inches out from the riser.  From there, it tapers pretty evenly to 5/32" at the beginning of the tip overlay.

So let's see.  It's 27" from the end of the riser to the beginning of the tip overlay, so that's 24" of fairly even taper.

So, (5/16" - 5/32")/24" = 0.0065 inches per inch.

But my bamboo is tapered, too.  It starts off at 1/8" at the end of the riser and tapers to 1/16" at the beginning of the tip overlay.

You've got to have your bamboo really thin toward the end or it'll overpower the ipe.  Or, you have to make it really narrow so the ipe doesn't get too thin in proportion to the bamboo.

My width starts at 1.25" at the end of the riser and tapers to 15/32" at the beginning of the tip overlay.  It's not a straight taper, though.  It's kind of bowed outward, like a football.  I think if you leave it parallel from the fade to just past mid limb, then taper to the tips, then round the corner where you began the taper, you'll get something close to my limb profile.

It's also a reflex/deflex.

[takefive]

I agree with Sam and Bowjunkie on keeping your bamboo at the thickness and taper they recommended.  On my first bamboo backed osage, I made the mistake of keeping the profile a good 1/4" wider than I needed and didn't taper the bamboo thinner to the tips before glueing it up.  When I narrowed it, the bamboo was so thick that I wound up with very little osage left on the belly after tillering.  
Depending on the type of glue you used, you may be able to get it to release using a heat gun and pry the bamboo off.  Then you could grind it and perhaps your hickory core thinner.  As dense as hickory is, you might consider using a lighter wood like maple, walnut, cherry, or elm for your core lam on the next one. Or skip the core lam altogether.
Either way, good luck to you with your bow.  And wear a respirator when you're working with ipe.  You don't want to breathe in that nasty stuff.

[Kevinnator11]

Thanks guys.  This one is pretty much set up but I have a another piece of bamboo and osage.  Hopefully I can get this one to bend enough to make a bow out of it.  

The advice all makes sense.  I have a bamboo backed Ipe I did that was really stiff.  On this bow the bamboo started getting really narrow when I was thinning it.

But hey, thanks for all the answers.  I'll post some pics as I go along and taper the next one better.

[Bowjunkie]

Here's a tip... if you haven't alteady, try this... flatten the belly side of the bamboo, then layout the front profile of the bow, slightly oversized, on that flattened surface, cut it out and clean up the edges, THEN thin the bamboo.

[Kevinnator11]

Well it blew up. Got really thin with the ipe belly so as usual you guys were right.  
 
But I had some Osage dimension lumber so I'm gonna try again.

[Ice Mike]

I've made quite a few of those myself!! LOL

I have what my kids call a "Wall of Shame".

Pick er up and try again man!! Don't let it get you frustrated..