I beam question

[ptberger]

I am building a couple of bows and it seems there is no downside to i-beam construction for the handle, but I'm not sure I'm on the right track with the idea. I'd like to use all wood in the handle. For example - if I wanted to make an I-beam handle for a 1-1/2" wide one piece longbow using all hard maple, I could rip two sections 4"x 16"x 3/8" thick and one piece 3/4" thick. Then reverse one of the 3/8" pieces and glue the three together. The glue lines running perpendicular to the back/belly of the bow. The window would be cut out of the 3/4" thick side so as not to cut into the i-beam. Is this the right idea?

Another option would be to rip three pieces all at 1/2", and then reverse the middle piece and glue up. The sight window would take half of the width of the center piece, but leave 1/4" remaining. Would that work?

The basic design is a R/D longbow, 58: long and between 45-50 lbs.

Thanks.

[Crooked Stic]

Three pieces same width. Flop the center. And if you cut to center your good. If you go past center offset the center piece right or left depending on if you are left or right handed.

[ptberger]

Thank you!

[kennym]

Different grain structure on all pieces is the very best.

When I make core lams I often cut from a different blank for each lam for that reason...

On veneers I like all same grain for looks tho but they don't do as much work...

Sorry, got off on a different tangent there...

[Kirkll]

Once you get the hang of it you can play with different thickness on I beam material. A thicker I beam looks different than a thin one does, but requires a bit of thought to offset it in the lay up with risers cut past center.

Then you can experiment with using G-10 for an I beam for strength and hide it completely like these two bows. Both of these risers have 3/16” G-10 I beams which were installed after doing the footings, and the shelves are cut 1/8” past center.

https://photos.app.goo.gl/poeNGopenWsqh32V9

[Tim Finley]

I beams on a take down bow are no stronger than the out side wood .

[Kirkll]

I beams on a take down bow are no stronger than the out side wood .

I think that statement could be debated.... The laminated material is what strengthens that strike area of the riser when you cut the shelf into it. You can cut one riser block into 3 pieces, and flip the center section to change the grain orientation and glue it back together to increase the strength.

[Crooked Stic]

If you don't cut thru it is much stronger. Why would you laminate at all if not for strength.

[Jon Lipovac]

If you don't cut thru it is much stronger. Why would you laminate at all if not for strength.

Most of the time, if I laminate, it's out of necessity. Sometimes the wood I have to work with may only be 1/2"-3/4" thick.

[Crooked Stic]

That would be a good reason Jon.

[Kirkll]

Using thinner material that is wide enough to book match can give you some very cool results…..

https://photos.app.goo.gl/6KrQEzdC7YGaa6du7

You can create  some wild looking veneer stock doing this too.   

[Tim Finley]

You weaken the I beam by drilling holes for the insert . Believe me I have proof of this even using dG10 as the I beam .

[Crooked Stic]

Sure that weakens it. Although where the inserts are should be a static area. I beams meant to strengthen the sight window area

[mmattockx]

So, let me get this straight. OP wants to take a solid block of hard maple, cut it into 3 pieces and then glue them back together, all with the goal of making the re-glued block stronger? Assuming it is decently straight grained there is no reason on earth why the sawed and glued block is any stronger than the original block, no matter how you flip the pieces around before gluing.


Mark

[ptberger]

I understand that but if the grain is not completely straight, then everywhere the grain rings intersect one another between the pieces, gluing those up would increase the strength, no?

[Crooked Stic]

Just Google is laminated stronger then believe what you want. For me I beams work.

[mmattockx]

I understand that but if the grain is not completely straight, then everywhere the grain rings intersect one another between the pieces, gluing those up would increase the strength, no?

If you have funky grain then you should be able to improve things by reorienting the pieces. If the grain is pretty straight you aren't going to gain much, especially when you glue the pieces back together on edge as is normally done with riser wood.

Just Google is laminated stronger then believe what you want. For me I beams work.

I would like to see some testing showing a significant improvement when a solid piece of wood is cut and then reglued. Normally you laminate to get better properties in multiple directions, like plywood. Risers don't need that sort of strength as it is mostly bending with a bit of torsion added in from the sight window offset.

I completely agree that using different materials you can gain strength and add a lot of aesthetic appeal, but I don't see the gains with one piece of wood.


Mark

[Smguinnip]

I believe that LVL’s are laminated for strength, otherwise why go to all of the effort to glue a bunch of wood together.

[Kirkll]

I understand that but if the grain is not completely straight, then everywhere the grain rings intersect one another between the pieces, gluing those up would increase the strength, no?

If you have funky grain then you should be able to improve things by reorienting the pieces. If the grain is pretty straight you aren't going to gain much, especially when you glue the pieces back together on edge as is normally done with riser wood.

Just Google is laminated stronger then believe what you want. For me I beams work.

I would like to see some testing showing a significant improvement when a solid piece of wood is cut and then reglued. Normally you laminate to get better properties in multiple directions, like plywood. Risers don't need that sort of strength as it is mostly bending with a bit of torsion added in from the sight window offset.

I completely agree that using different materials you can gain strength and add a lot of aesthetic appeal, but I don't see the gains with one piece of wood.


Mark

Hey Mark.... You are fighting a loosing battle with this one... You could spend hours reading different test results of the strength increase and stability superiority of laminated wood.

one solid piece of wood is only as strong as its weakest point.  The huge advantage of using an I beam is that you are creating a composite of wood and glue strength rather than just the strength of a piece of wood. The stiffness it creates is much higher than a single piece of wood, and it prevents warping too.... There is a good reason they laminate cabinet doors rather than using one piece of wood...... "Cutting up big ones, to make little ones, to make big ones..."  The mill workers mantra...   Kirk

here are some specs to look at.   

 https://www.ajuronline.org/uploads/Volume_15_3/AJUR_Vol_15_Issue_3_12172018_p35.pdf

[mmattockx]

Kirk,

Thanks for the paper, I will have a read through it.


Mark