When to I Beam?

[Appalachian Hillbilly]

Got my new 3 piece riser roughed in. This is black walnut with a section of bloodwood and maple accents. I know the laminations help and the Bloodwood is exactly twice the Janka of hardmaple at 2900 lb ft at over 3,000,000 elastic modulus.  This bow will see limbs up to 50 lb but normally 45. I have some Carbon fiber at about 40 thou and some G10 on the way. Should this be I beamed?

[kennym]

I’d think that would do at 50 lbs

[Crooked Stic]

First off walnut not the best choice for TD riser. And an Ibeam always stronger than accents. But as long as you have most of that bloodwood still in the throat I think you will be fine in the 50 lb. Range.you can always glue that carbon or even some glass on the front of the riser. You might want to cap your pads anyhow with glass.

[Appalachian Hillbilly]

Plans are to bury an accent of that curly maple under glass on both the back and belly of the riser. I want to keep the maple the same color and it is going to have to be under clear glass to do it. I might do an I beam just to learn since I am still new to all this and experimenting

[Crooked Stic]

If you do the Ibeam on what you got there you might want to drill 1/4 holes in a part that you cut off later then you can Dowell it on glue up and your accents will stay lined up.

[Kirkll]

The shape of your riser often dictates how much reinforcement is needed in a riser regardless of wood species. But using softer hardwoods like black walnut and curly maple you need to be careful.

There are tricks that can be used by tying your limb pads together using a radius shape to the back with wood , phenolic,  or even  G-10 on the limb pads, and use overlays on S shaped risers to cap the end grain.

But.... you need to think about riser flex too in heavier draw weight bows. That is where an I beam design really shines. and... you can use wood as an I-beam with better luck than using composites.

To answer to your question as to this riser needing an I-beam..... No.... but you may want to consider doing overlays on the back of the riser to cap any end grain on that walnut.      Kirk