Explain the I beam

[buckeyebowhunter]

Gentlemen,  I've been reading up on the I beam risers in the older posts on here,  and I've noticed many bowyers incorporate this into their riser. But I'm having trouble understanding why and when it's necessary. So far all of my risers have been built with actionwood from Bingham's so I haven't done any back to belly I beam but I have ripped the risers and added vertical accents with phenolic without any problems.  Is the ibeam supposed to be a precautionary step for risers made from lighter woods or heavy drawing bows? 
I guess I'm just having trouble seeing what the fuss is about. From what I can tell none of my bows(that I haven't built) have an ibeam but just vertical accents through the riser.  Thanks in advance. I hope this question doesn't seem silly I just love learning and hearing new things from you guys.

[kennym]

Is the ibeam supposed to be a precautionary step for risers made from lighter woods or heavy drawing bows?

Yep, mostly.  Even if you ripped the riser in half and flipped one piece and glued back it will make it stronger. But also looks cool sometimes.

Some of the old bows had them also, but I figure that was to use all the lumber up.

[OkKeith]

Anyone have some good photos? Maybe some build photos?

I have read a lot about the I-beam in bow building but have no clear mental picture of how it works or how to build it.

OkKeith

[buckeyebowhunter]

Thanks Kenny. Keith when I first started I was under the impression that an ibeam was just a vertical accent like in my first picture. However my research has led me to understand that it is a lateral lamination running from back to belly if looking at the riser from the side. 

I understand it adds strength but I was just wondering if it was extra work that wasn't necessary.  Probably not from a liability standpoint if you're building bows for strangers as a living. 

[kennym]

Not all I beams are hidden , but that’s a cool one!!

[kennym]

Here is one I put in my wife’s bow, wanted lams and riser to match but only had a thinner board to get riser from ..

[kennym]

Oops




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[Buemaker]

Bubinga I beam with thin maple veneers in Rosewood handle blank.

[Buemaker]

Offset I beam.

[OkKeith]

So to test my understanding...

The I-beam is less of an "I" and more of an "l"; Either with it's narrow width running from side-to-side in the riser or running back to belly in the riser. It generally comprises one quarter to one half of the riser mass. In a take down it can run from the tip of the limb pocket to the tip of the limb pocket or be mostly in the "handle". In a one piece bow it doesn't run into the fades and certainly not into the limbs.

Materials can be most any solid natural or composite and are integral to the glue-up. They can be decorative or just functional.

Am I on track? My question is... is any portion of a laminated riser that runs through the middle an "I-beam"?

OkKeith

[Crooked Stic]

Anytime you cut the wood apart laminate it it will be stronger. The front to back beam with a stronger wood for the beam or same wood if strong enough. Off center for selves cut past center and two piece TDs. I have not seen what Stalker puts in that routed groove. Must be multiple pieces of G10 so they bend to fit. I know there used to be a bowyer that put a steel rod in his one piece riser. GameMaster Jet I think.

[hunting badger]

I use I beams a lot. I live in Alaska a Exotic woods are hard to come by especially ones in riser dimentions, so I but 3/4' or 1" stock and laminate an I beam in the riser, then I plane to width. I Peek a boo most of my sight windows so you need to off set the I beam so you get the sight window into the I beam. It opened a whole new world for me as far as riser material goes! the last bow I built I used tiger wood from a stair tread as the outside of the riser and a 1/4' Purple Heart I Beam. It turned out pretty sharp and the riser cost practically nothing.

[Bow Bender]

This is what I have always considered to be an "I Beam". Bear Kodiak Magnum, 66#, center is rosewood the outsides look like bubinga but I may be wrong.