Plywood loose laminate prod?

Is it safe to use cheap plywood cut into strips and made into a loose laminate prod? I fear it might shatter somehow, or just be very large and heavy. If it is safe, what would be a the best thickness to use and are more or less plys better? 

Very basic testing by clamping two pieces of 1/4 inch plywood scrap into a vice and bending it and letting go few times made me think it would work pretty well, until the forward one snapped forward at the vice.

Hello Bs; If you fear a breakup , wrap the thing with flexible tape or rags , anything that would contain it in the event that it broke. We  do this all the time ,even with steel limbs.Always think safely.

Prods of laminated plywood strips?  Surely you jest.
Personally, I'm holding out for prods made of compressed horse manure... Geezer.

What you'd have is a laminated prod with half of the material being dead weight and very likely to fail since plywood consists of layers of wood with the grain rotated 90 degrees between each layer. If all of the layers in plywood were parallel it would behave more like a wood-backed bow. Why not use bamboo or normal lumber?

Geezer here.  My previous jest aside, Xamilew is right on the money. Assuming you cut your plywood lames so the outside grain runs correctly from end to end, every other layer of the wood will run across the grain and yes, it will add weight without any benefit whatsoever.  There are lots of materials... some of which can be found around the house that will make a decent bow.  Plywood isn't one of them... not even for the stock. As noted bamboo or even red-oak lumber from the local big-box hardware store will make much better bostaves.  This is a place where a little research will pay big dividends in non-wasted time.  Geezer.

Thanks for all the help. The part about half of it being dead weight mostly is what killed it. Almost all of the wood around here that's at all cheep is pine, and after using it to make the whole body of a crossbow i cant stand working with it, as it splits if you look at it funny. How does multiple boards layered into a loose laminate compare to a properly made wooden bow? I'd expect the normal way would be better, but the loose laminate would be far easier to make, seeing as it would be just chopping them to the right length and layering them the right way.

 How do you keep them from sliding out of place without a pin going through them? I'd assume when in a crossbow they'd be held by clamping force, but you couldn't remove it while strung or all of it would come sproinging apart, possibly with the front most one snapping. 

Edit: Dragging and dropping text into this forum doesn't work right, weirdness from that fixed.

If you pin them, they're not a loose laminate.  As I recall, the ancient chinese used loose laminates of bamboo that were wrapped around the prod in several places.  If all you can get is pine, you're in big trouble. It's fine for building houses, but yes, it makes a pretty bad stock.  I actually made a couple of pine and sympathize strongly.  So perhaps you should look into loose fiberglass or plastic laminates.  Just be aware that fiberglass is actual glass and not something you want to inhale.  It's best cut wet.  Some years ago, I knew a guy who made tolerable loose-laminate prods out of sail battens.  A little ingenuity should find something workable.  Whatever, don't give up.  Geezer.

Geezer wrote:If you pin them, they're not a loose laminate.

I meant in the middle, so it all stays together, not anywhere else. Also how does pressure treated wood work for ether bows or stocks? I got some of it for free.

I can't claim to be an expert on loose laminates, but generally speaking you don't want to make any holes Through a prod, not even in the middle.  You could glue them together I suppose, but perhaps one of the best arguments for a loose-laminate is the possibility of removing one or more lames if they break or otherwise misbehave. So you might want to glue them with something like bees wax or paraffin... enough to hold them together while you're securing the prod in place, but not so securely that you can't break the bundle down later and make changes.  Does that make sense?  Geezer.

I agree about not wanting to make holes in it, and i think just taping it together until it's in the crossbow and held together by whatever holds the prod in seems good enough, though doing that would make it impossible to take the prod out of the crossbow without unstringing it, as nothing would hold it together in the middle, maybe even making the forward most one snap.

I think I've made as many, if not more, loose lam prods that the others who post regularly, so I'll weigh in with my tuppence.

1.  If you're trying to make a crossbow 'on the cheap', take up knitting.  You must have proper materials - good woods, metal, fiberglass, plastics, bone, etc.  Cheap materials are doomed to fail.  Not saying you have to spend $1000 bucks, but you have to source the Good Stuff, and pay the price where it matters.

2.  As noted, plywood is worthless.

3.  Loose wood laminates will work, but if you must work with wood:

  A.  Pine does not work.  You want long fiber hardwoods like Osage, Hickory, Yew, Red Elm, etc. the classic bow woods.  Or wide bamboo slats like the Chinese used.
  B.  Pressure treated wood -- usually Pine -- is not stronger or better at anything except avoiding rot.  The pressure treating chemicals add tons of weight.
  B.  Laminates are loosely bound with twine of some sort at several places equidistant from the center.  NO HOLES  -- EVER! Once strung, tension will keep the lams stacked in place, and the lashings keep them in line.

  4.  The least expensive, most useful material I know of for making loose laminate prods is Fiberglass Chainlink Fence Tension Bar.  It's about 3/4" x 1/4" or 3/8",  and comes in 4 ft to 8 ft lengths.  You can find it at fencing supply companies, or from a number of outfits online.  A 5 ft length is around $4 if I remember correctly.  See the builds that Xamllew and I have posted on the subject. 
     Another, but more expensive alternative, are fiberglass Boat Cover Support Bows, which are about 1-/2" wide and 1/4" thick, but not nearly as stiff as Tension Bars.  They come in 6 ft or 8 ft lengths and cost around $25 each.

You might want to look at backyardbower on YouTube - he discusses PVC pipe.  I don't see much enthusiasm for it here on the Guild but it might be worth a look.  If I had difficulty finding white woods in the local forest I would give it a try.

Godric is also right.  A PVC is pretty cheap (under $10) and can make you a prod in the 80# to 125# range easily.  Nick Tomihama - The Backyard Bowyer - often posts on the G+ community called PVC Archery and Crafting, where several of us have made PVC prod crossbows

PVC pipe is certainly worth experimenting with if you are on a budget. I think the main disadvantage of using it for a crossbow spring versus a hand-drawn vertical bow is how quickly it takes a set- the longer you leave the crossbow drawn, the weaker it becomes. This of course is not such an issue with the typically quick draw and release of a hand-bow.
Gnome

I agree also .I have made several. They will take small game with ease. The life of them is not bad either. Nick tells how to fix a folded bow and it works as good as new.I 've done it on purpose. I've used   inch and a half, inch and a quarter, and one inch . Better eat breakfast when you cock the inch and a half. Mine bottomed my 100 pound scale so I can't say what it pulls.

Plywood will work. I have seen it done.
Veneer on outside layers should be flawless with no run-offs or knotholes, and make at least 40% of total thickness ( = no mote than 5 plies )


Best way is to cut it to split diamod shape strips of same legth. So each strip makes a bow on its own.
Meaning a stacked bundle of bows, rather than Chinese style loose laminate.
The work to do this is about the same as cutting straight strips. It should shoot better. And one of the bows can be tested and broken so you know exactly how much strain your bow can take and how many strips your bow needs to do what you want it to do.

Xamllew wrote:What you'd have is a laminated prod with half of the material being dead weight and very likely to fail since plywood consists of layers of wood with the grain rotated 90 degrees between each layer

Only the outernmost surfaces are really doing any work on a bow limb. So this is not really an issue. In fact there has even been a patented flight record breaking laminated wood bow on the market, that had vertically oriented core layer - technically plywood with all the wrong grain orientation.

kenh wrote:

  A.  Pine does not work.  You want long fiber hardwoods like Osage, Hickory, Yew, Red Elm, etc. the classic bow woods. 

Pine is a classic bow wood. The earliest known bows were made of pine.
In arctic region bows have traditionally been compression pine with backing of birch or willow.
Sinew backed pine bows are also known from North America.

As far as loose laminates go, the type of thin pinewood strips that are often used as spacers in lumber bundles should work adequately.
I have made some some model bows out of them for testing tiller profiles and backing materials. They shot reasonably well.

A pine bow should have edge ringed grain orientation as dense as possible. Backing it with vegetable fibers or more tension strong wood is recommended.


ps.
Nice to see geezer describe the value of his input again.

Geezer wrote: ... horse manure...

Well, that is all you really can offer.
Given that you do not even make your own bows. You are just assembling outsourced components and pimping them with bling.

Geezer here, Pimping thrown-together product as always (as long as you don't count the 2000 plus crossbows I've made in my day (I used to make all my aluminum prods, but eventually contracted those out to friends who could do better/cheaper.  I do buy my steel prods from Slobows and Alchem.
You can make a bow out of plywood and you can make bows and stocks out of ordinary pine (it depends to some degree on what sort of pine you've got) but in fact, plywood makes a very unsatisfactory stock and a poor bowstave.  Backing a pine bowstave with sinew, and even better, adding a belly of horn will substantially improve your pine bow.  But in fact there are lots of better woods available for both stocks and prods. (bowstaves or laths) If you want to build your own staves of wood, I recommend looking at the Bowyer's Bible.  If you want to build your own stocks, I recommend looking at the sort of woods that are used for fine furniture.  In my time I have used (for stocks) mahogany, oak, birch, maple, walnut, cherry, jacaranda, purpleheart, cedar, pine, manzanique... that's all I can think of at present.  Of those I would seriously dis-recommend all rosewoods (they're very hard, allergenic, toxic, and high in silicates) Purpleheart is hard and high in silicates, pine (for a stock) is soft, tends to splinter. Manzanique is hard, handsome and I'm allergic to it.
A but what do I know, I'm just an old duffer who simply assembles parts made by other people and pimps them with a few fancy add-ons.  Keep having fun.  Geezer.

Well, that is all you really can offer.
Given that you do not even make your own bows. You are just assembling outsourced components and pimping them with bling

hullutiedemies;

One of the best things about this forum, and one that has set it apart form most other forums, is the welcoming, supportive, and laid back nature of this one, unlike many others that I have subscribed to.
Which, is why the above statement is distressing.
Geezer is a curmudgeon, he'd be the first to admit that, and you are welcome to call him out on that, you are not, however, welcome to personally attack, and write mistruths.

The former, being an unwritten rule on this forum, and the latter, simply incorrect.

To address the former, please, no more personal attacks.  Express your displeasure at what you feel may be unkind statements, yes.
I will address the latter here:
I have worked with Geezer for 8 years. He has forgotten more about crossbows, than I have learned in that time. When I first started, we made the entire bows by hand. All of it, with the exception of steel prods. Now, we outsource for most of our prods. And, now, I outsource my triggers. That is vastly preferable to firing up the forge, making triggers, and being unable to use my sorely used arthritic shoulders for several days after. So, the local blacksmith makes my triggers, and I am thinking of having her make my stirrups as well. And, in that tradition, we are simply following the traditions of guilds of several hundred years ago. And, I am saving my shoulders, so, I can continue to work.

The rest of the bows are made by hand. We use lumber from the lumberyard, that we cut and shape into the various medieval styles that we have chosen. We use spokeshaves, drawknives, planes, rasps, bandsaws, and sanders to do that. We cut metal to shape for our lockplates. We use the lathe to make bone nuts. I use bone plates, that I outsource now, after several years of cutting actual cow bone for inlay. I buy large cow horns, that I cut and heat for inlay.
We do not merely assemble parts. If we did, I would not be doing this. I was a woodworker and artisan before I started this trade with Geezer, and I am still.
I am one of the better bowyers in North America, thanks to him.


As an Admin on this forum, I would have asked you to not personally attack other members, and, as Geezer's Journeyman, I can tell you that you are incorrect.
If you will have a look at that last several photos on this gallery, you can see that I do not "assemble parts." With the exception of the trigger, stirrup, and prod, that bow is entirely handmade by myself, down to the horn bolt clip, for which I made a hardwood mold, in order to heat, clamp, and then finish that bit of horn. 
http://swifthoundbows.com/Lychee/#4
Your being an inventor, and trying new things, does not invalidate the work that I, or Geezer, or other bowyers do, and the fact that we try to be as authentic to the old bows as we can, (and still try to make a living) does not invalidate your trying new things.

So, I would welcome the continuing of this conversation, but, with a mind towards no personal attacks, on any side. 

Lightly
Who has only made 150+ bows yet, and still has a crap-ton  more to learn.