Ibeam question

[savage1]

I did my first ibeam with phenolic and didnt mind working with it but I would like to do one of wood only.
So Im asking for wood combos(the whole riser and ibeam) and construction info like number of lams or thickness of beam..I may do a glass stripe through handle but lets talk just wood ibeam riser no flares or arches, those will be optional.
Any pics of wood combos would be nice.
Lou

[LittleBen]

I just glued up a Wenge riser with a curly maple I-beam. Wenge is 11/16", and maple is 7/16" IIRC

Total width of 1 13/16" I think or something close to that.

It's Wenge-Maple-Wenge.

Looks good so far.

I also like the purpleheart I beam. I like a nice contrasting wood to show only in the sight window.

[heartlandbowyer]

Just helped a mooseman1967 do a Padauk/Walnut I beam looked pretty good taking the plunge thread. Also did a walnut with Purple Heart beam for jswekas swap bow and a dark lacewood with Purple Heart beam which looked good also. Can't hardly go wrong with purpleheart, I imagine that's why Bear did it in so many bows.

Cory

[Canadabowyer]

One of my favorites is an osage I-beam with cocobolo sides.For my 1 3/4" wide riser block I use 3/4" osage and 1/2" coco sides.Use a hard, heavy wood for the I-beam and you can get away with a lighter wood for the sides. Bob

[Troy D. Breeding]

I've made afew bows with what is now called the I-beam. Only back then I used three pieces because that's all I had and thick material was hard to get. Most were all the same material so the I-beam wasn't noticeable.

Troy

[savage1]

Thank you  for your responses. I have seen bows with large midsections. I was thinking three thinner pcs. and two outers. My thought was strength in the lamination. So if I went single in the ibeam, how thin do you think will withstand up to mid fifties draw weight? What would be top three or four choices of hardwood for said thinner beam?

Lou

[jsweka]

Yes sir - the purpleheart/walnut combo Cory put in my bow is SWEET!
 

[Troy D. Breeding]

Most Exotics as well as Osage, Black Locust, Hickory and Hard Maple will work. I'm sure there are others, just can't think right now.

Troy

[DavidV]

I like something with figure for an I-beam if it's large. Leaopardwood would look cool.

[Crooked Stic]

The reason for ibeams aside of a different look is strength. So yes the dense heavy woods are best. One not mentioned I like to use is Ipe. It is not a character wood  but very dense and stable. I like mine to be 5/16s to 3/8s

[4runr]

Black and White Ebony I-beam with some pretty Cocobolo.
 

[Troy D. Breeding]

4runr,

I'm normally a fan of the off colored I-beams, but that B&W Ebony is killer with the cocobola. Guess the splotichy look of the ebony is what sets it off.

Troy

[savage1]

4runr, that is an awsome bow! Beautiful combo.
How long is your riser on that bow?

I wold like to see some osage work.

Lou

[4runr]

Lou, the riser is 13 inches.

The bow is my Hill Country Bobcat. Roman Hershberger custom built that bow for me.He wasn't too sure of the combo, when it was finished he liked it.

[heartlandbowyer]

Bocote/Osage and 1/4 phenolic beam.

[LittleBen]

Lou,

My take on it is this:

If you only laminated 2 pieces of wood to make the riser it'd be stronger.

HeartlandBowyer showed the phenolic I-beam above as well. Phenolic is not really particularly strong compared to hardwoods. I think any reasonable hardwood and you're good to go. Hickory, BL, maple, Oak, cherry ... the list goes on. I probably would use poplar but other than that any domestic hardwood should be fine ... Elm, Ash etc.

Obviously any of the very hard exotics as well. ipe, bulletwood, bloodwood, prupleheart, yellowheart, redheart, jatoba, cumaru, santos mahogany etc. etc.


Lastly I'd say this, the riser on a 72" bow has maybe 25% more stress than the riser on a 54" bow at the same draw because of the leverage of the limb tip from the bows center. I think probably any reasonable combo is overkill.

[savage1]

Thats  what I wanted to hear, glass and my bandsaw dont get along so why use it?
 Do you guys lay up the ibeam differently if you are cutting to center? Better yet guys how do you lay yours? Center, offset?

Lou

[LittleBen]

I cut mine to center almost always. I lay up the I-beam so that when I cut the sight window, the line between the Ibeam and the outer wood is in the position I want, near the top of the saight window ... It's a purely asthetic decision. No engineering involved. Just make sure it goes ehnough past center that you dont cut through the I-beam That will be weaker and not look so cool.

[Buemaker]

Think, think, I do not know, but I wonder.  If you glue up a riser, shall we say the conventional way with a center piece of say purpleheart  and back and belly with say walnut. Then another with the purpleheart as an I beam and walnut on the sides. Now that the woods are glued up they act as one piece of solid wood. Is the one with the I beam any stronger and If so why. If the year rings are stacked the same, is it a difference, wood is wood. Are we fooling ourselfes thinking the I beam construction is stronger. Not being an engineer I just wonder.
If the conventional way is made the strongest wood must of course be placed in the riser where it is mostly stressed. Bue--(monkey brain)    

[savage1]

That is a good question. For me I think the ibeam has an advantage in the harder wood is being drilled into where the otherway you might not without changing hole pattern. The look of the ibeam is good with no shaping where on the side
Many prefer radiusing or even flares.
Lou