Alternative core woods

[EwokArcher]

I have maple boards I have cut up for core lams. But I am about to start a 60in kennym and am thinking about experimenting a little. I was thinking about trying 2x4 lumber sliced up for lams or even some cedar fence. Why not? It's kiln dried but the stuff I have has been sitting in my shop equalizing for over a year. I have good grain orientatioon on my pine boards it's very light weight. Any success or failure with this you would like to talk about? What about recommended lam thickness? Multiple thin vs a couple thick ones. Let me know what you think, thanks guys.
Ty

[KenH]

Something like 88% of the strength of a wood-glass composite bow comes from the glass.  The core really only serves to keep the two pieces of glass a specified distance from each other.

I make my Prototype bows -- the first one off of a new jig using plain Big Box pine.  I use a couple of thin lams.  The Prototype gets finished out just enough to be able to string and test draw on a tillering tree -- so I can get a measured draw weight at my draw length.  Plugging those numbers into my Stack Calculator allows me to get real close to desired weights with successive bows.

[Crooked Stic]

Let us know how the pine works out for you.

[styksnstryngs]

Eastern cedar has been used for limb cores, and is fast because of it's light limbs, but also more prone to damage of course.

[jess stuart]

I would be cautious of using pine seems very soft, don't know about the cedar, maybe as veneers.  I guess I am not of the adventurous spirit.  Let us know.

[JamesV]

I have used dozens of different core woods for glass bows. Yellow pine works good, red oak, white oak, hickory, red cedar, hackbery, Locus, douglas fur. The only wood I had fail was cypress, nine times.  

James

[kennym]

Don't know about the pine, I would worry about adhesion with it, plus it will gum your sander's paper . If it is Western Cedar, the brown stuff I wouldn't use it, it is not very strong at all.

But if you're gonna put the time ,effort, and money in for a riser, glass and glue, why risk it on lams?  JMO

[fujimo]

x2 wot kenny sez- the pine will clog your sander.
James what cypress did you have fail.
 i have some beautiful Alaskan cypress( yellow cedar) that i wanted to use.

[Roy from Pa]

X's3 on Kenny.

X4 Kenny... Maple has a very proven track record... That's why everybody uses it...  I am not sure what type of bow you plan on building... If you are building a R/D bow and want to get adventurous scarf some douglas fir onto maple lams 2/3 the way out on the limb and taper your glass in the same area...  That should get you a 15 to 20% lighter limb out near the tips... No guarantees the fir will hold up but it won't be as stressed as the mid limb area...  But it will have to deal with the shock of the string...

Originally posted by Crooked Stic:
Let us know how the pine works out for you.

hey Mike...  Were you being facetious??    

[mikkekeswick]

Although the glass is doing the compression/tension work the core still has to be able to resist sheer forces. Pine will fail due to its non uniformity.
A great wood for lighter core lams is black walnut.

[JamesV]

I built 9 kid's bows using Bald Cypress from the Mississippi Delta and over time they all came back with the core broken at the fades. I rebuilt all of them using the same risers with several different core woods and they are still shooting today.

I have built a dozen or more hunting weight bows using yellow pine and none have failed. I did cure the epoxy at room temp and I cut the tapers with my planer so no paper to clog up.

James

[bamboo]

i recently had black walnut lam pop right up the middle--it was the center lam of three--i would assume neutral plane--it popped down the middle approx .030 on each side of the split--not a delam--no glue failure at all !!--no more flat sawn lams for me!--funny thing is unstrung the recurve held its shape--it looked perfect!

 the shear forces are strong!! even in the neutral area

of the limb--this lam could not take it--i think it was a fluke!but a learning experience!

[Roy from Pa]

1/4 sawn is all I use. Rift if I have too.

[EwokArcher]

I have some basically free walnut riser material I'll only be out the cost of my glass. I think I'll try pine lam core 2 pieces quarter sawn and be a little thin strip of maple in between.  I'll be shooting for 45 pounds at 27 inches on a 60 inch Kennym r/d. I'm feeling pretty good about it not a crazy stressful design.  I'll be able to get a really close cut on my bandsaw so I shouldn't need to do a crazy amount of sanding.
I'll post up progress for y'all.

[mikkekeswick]

Wood doesn't know what orientation it is being bent in....one day a tree will bend against a north wind, one day against a southerly.....
Roy what matters is straightness of grain for a lams 'strength' not grain orientation....
Ever looked at all that earlywood on a quarter sawn lam and realized there is less on a flatsawn belly lam? Which can resist comnpression better?
How about selfbows do their bellies fail because they are 'flat sawn'.....?????
Ewok - honestly forget the pine    Heartache follows!

[Bvas]

Originally posted by mikkekeswick:
Wood doesn't know what orientation it is being bent in....one day a tree will bend against a north wind, one day against a southerly.....

Ever looked at all that earlywood on a quarter sawn lam and realized there is less on a flatsawn belly lam? Which can resist comnpression better?

I find your comparisons confusing.
A tree is supported by every grain orientation imaginable from any given direction. So who knows which is providing the strength?

Early wood vs late wood is dependent on the trees growth, not on how a board is cut.

[Roy from Pa]

Mike, I didn't say anything about grain. All I said was I always use 1/4 sawn or rift sawn as a second choice. Yes all selfbows are flat sawn, so to speak. And 1/4 sawn or rift sawn has nothing to do with grain, it's just the orientation of the growth rings.

However, why are all wooden baseball bats made to hit the ball against the growth grow rings and not on the flat sawn surface? It's because 1/4 sawn wood is stronger.