Help with dimensions for Yellowheart board bow

504state · February 16, 2019, 11:59:37 PM

Hey guys, I have a 72" by 1 1/2 by 3/8" piece of yellowheart for my next bow. I don't know much about it and have only used it in risers. I read it has some similarities to ipe. I plan on backing it with bamboo and do have ipe to use as a lam if I need to. Can I get a hunting weight bow at 27" on a piece that thin? Any suggestions on layout?

Crooked Stic · February 17, 2019, 08:43:07 AM

Yellowheart is dense and stinks when you cut it. Other than that I dont know.

Pat B · February 17, 2019, 11:55:45 AM

If you have ipe, use the yellowheart as a core lam and the ipe for the belly. I've never used yellowheart so I can't talk about it durability or it's properties.

504state · February 17, 2019, 03:11:28 PM

Gotcha. Any suggestions on thickness?

Pat B · February 17, 2019, 05:38:56 PM

The few lam bows I've made the center and belly lams were about 1/8" and parallel. Someone else might have a more engineered recipe.

504state · February 17, 2019, 11:06:05 PM

Cool. I will go that route if I have to go trilam. 1/8" for the bamboo sound ok?
Appreciate the info!

BMorv · February 18, 2019, 09:57:45 AM

Yellow heart is nice to work and can make a good bow, but it isn't ipe. Ipe is a better bow wood and can withstand almost any design when used as a belly. Not so much with yellow heart. It will fret if pushed too hard...Meaning you can't put too much reflex/deflex and you should have a decent amount of working limb for the draw length. If you follow those suggestions, it can make a nice bow.
If you are set on using yellow heart for the belly of a tri lam, this is what I would start with:
65" ntn, 1.4" wide fades for 6" then straight taper to .5" tips, start with about .45" stack of YH and ipe (not including bamboo), so something like 1/8" thick ipe with .325" YH. 12" handle. I would pre-taper the YH.
This should be a little heavy but will give you room to tiller. I always go thicker than I need on a new design.
Try for 1/8" thickness of the bamboo at it's thickest. Mine usually come out a little thicker.

-Ben

504state · February 18, 2019, 03:06:54 PM

Quote from: BMorv on February 18, 2019, 09:57:45 AM
Yellow heart is nice to work and can make a good bow, but it isn't ipe. Ipe is a better bow wood and can withstand almost any design when used as a belly. Not so much with yellow heart. It will fret if pushed too hard...Meaning you can't put too much reflex/deflex and you should have a decent amount of working limb for the draw length. If you follow those suggestions, it can make a nice bow.
If you are set on using yellow heart for the belly of a tri lam, this is what I would start with:
65" ntn, 1.4" wide fades for 6" then straight taper to .5" tips, start with about .45" stack of YH and ipe (not including bamboo), so something like 1/8" thick ipe with .325" YH. 12" handle. I would pre-taper the YH.
This should be a little heavy but will give you room to tiller. I always go thicker than I need on a new design.
Try for 1/8" thickness of the bamboo at it's thickest. Mine usually come out a little thicker.

-Ben

Awesome man thanks! I was trying to stay away from a trilam but I am comfortable making them. I'm actually not dead set on YH as the belly but I do think it would look cool.
Question, when making a tri lam can you taper the belly to the point where it fades into the core at some point short of the tips?
For instance if I didn't make the belly thick enough and had to scrape past the belly wood to tiller.

BMorv · February 19, 2019, 11:22:06 AM

"Question, when making a tri lam can you taper the belly to the point where it fades into the core at some point short of the tips?"

I wouldn't do that. I've heard of the belly crushing or collapsing if it gets too thin. I wouldn't feel comfortable with anything less than 1/8" thick continuous belly. Maybe a little less with something like ipe.

Pat B · February 19, 2019, 11:45:42 AM

Yes you can taper the belly lam first leaving it short of the tips. The only place you actually need the belly lam is at the working portions of the limbs. I wouldn't do it unless I knew exactly how thick it should be to be close to tiller. Even if you add a 1/8" belly lam you will be tapering it as you tiller the bow.

504state · February 19, 2019, 06:01:48 PM

Quote from: Pat B on February 19, 2019, 11:45:42 AM
Yes you can taper the belly lam first leaving it short of the tips. The only place you actually need the belly lam is at the working portions of the limbs. I wouldn't do it unless I knew exactly how thick it should be to be close to tiller. Even if you add a 1/8" belly lam you will be tapering it as you tiller the bow.

Awesome thanks. That does explain a lot. I think i need to ease up on my taper before tillering in general.

BMorv · February 19, 2019, 06:30:44 PM

How much are you pre-tapering?

504state · February 19, 2019, 09:24:11 PM

Quote from: BMorv on February 19, 2019, 06:30:44 PM
How much are you pre-tapering?

With ipe I usually go 5/8 at fades to 1/4 tips. I can't remember what I did with the few tri lams I have done. I haven't done this in a few years. I did one a couple weeks back that came out under weight but I didn't take notes.

BMorv · February 20, 2019, 09:36:37 AM

Yeah a 3/8" taper is a lot. I would try for about 3/16" total taper on your next one. It should get you close with most designs where you width taper in a semi-pyramid shape.

504state · February 20, 2019, 10:56:35 AM

Quote from: BMorv on February 20, 2019, 09:36:37 AM
Yeah a 3/8" taper is a lot. I would try for about 3/16" total taper on your next one. It should get you close with most designs where you width taper in a semi-pyramid shape.

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