Hardwood Ply vs Hardwood Question

[Nathan Wittman]

I do not know which forum to post this, but I have a question regarding wood. A friend of mine has asked me to build him a speargun blank which is traditionally built of lamentating 4-5 layers of teak into a blank. I am fine with building it this way, but I had a thought, in looking for options in terms of strength.

If marine ply wood is made of multiple plys lamenated together with waterproof glue, would the final blank be stronger using marine ply as compared to solid hardwood, like teak?

The marine ply would have no voids and is engineered with multiple layers in opposite directions. Just a thought, since I am looking to create a very strong blank to build the gun out of.

I will probably go the teak route because of its beauty but I was looking for the strongest blank I could build, would the marine ply end up stronger?

Thank you in advance for your replies.

[Prashun Patel]

Not sure what you mean by 'strong'.

Plywood is known to be more stable than solid stock for the reason you cited.

Solid stock will likely hold fasteners better than the plies of plywood.

That's about all I know.

[Nathan Wittman]

Thank you for the quick reply. In a speargun, the blank has a tremendous amount of stress placed upon it from the long bands that are used to propel the spear.

So solid, naturally water resistant woods have been used for construction.

I was looking at flooring the other day and the salesman was telling me that engineered floors were "stronger" than solid wood and also more stable. So that's where this whole thought came from.

So really the question is, in general would ply, terms of maintaining a straight solid blank under stress, have less chance to break, splinter, shatter than the blank made from solid teak, which is also 4-5 pieces of solid teak laminated together?

In reality then, with 7ply marine ply, be more stable less apt to snap, because you would now have 35 plys (7ply x 5 pieces) as compared to the solid teak (5 pieces).

Thanks again for the replies.

[Rod Sheridan]

Bows are normally laminated from solid stock, with the grain all running in the same direction.

Plywood isn't built this way.

Another consideration is the adhesive, I sugest that you research which type of adhesive will withstand the tremendous changes in shape and size that occur when you bend and straighten a laminated item.

Regards, Rod.

[Ed Peters]

get your hands on anything that can really be considered hardwood plywood. Hardwood veneered, sure. But not hardwood throughout. So, no, it won't be as strong as solid wood laminated into a blank.

Ed

[Sonny Edmonds]

If you glue up the hardwood yourself, you will know exactly what is in there.
Glue up marine ply, and it's a guess at best.
So I would go with the hard way. But I usually do that anyway.
Besides, gluing up the individuals allows choices like contrasting woods and custom inlaying if desired.

You might want to lookie here and see the parts. (http://www.bluewaterhunter.com/shopsite_sc/store/html/shop_gunaccessories.html)

You'll be fitting these up.
Also, take a gander at the actual guns. Wooden spear guns are coming back strong because of the buoyancy that is inherent in them. Neutral buoyancy makes the gun easy to handle underwater. (neutral buoyancy means the gun, as a unit, is easy to point and doesn't droop or float awkwardly)
If your friend (customer) will fork over the costs, you could build in the hardware as you go. (Not hard that way)
BTW, usually it is kinda hard to make anything by building something for someone. You'll need to compete with these (http://www.bluewaterhunter.com/shopsite_sc/store/html/shop_spearguns_biller.html), as a rule. Out the door, so to speak.
So know what you are up against. ;)
Have fun! :)

[David Romano]

I would not use plywood for this. If you use solid teak, you know it is solid teak. Marine plywood cannot be as dense as solid wood. Also the stress is probably only along one axis, if I'm picturing this right as somewhat like a long bow. The plywood's orthogonally alternating grain direction would actually weaken the gun along the important axis.

David

[Nathan Wittman]

If you glue up the hardwood yourself, you will know exactly what is in there.
Glue up marine ply, and it's a guess at best.
So I would go with the hard way. But I usually do that anyway.
Besides, gluing up the individuals allows choices like contrasting woods and custom inlaying if desired.


I completely understand the process and will be using system 3 epoxy reinforced with glass fibers to laminate the stock. This is not for a customer, this is for a friend and I do everything for my friends for free. So, I am not competing with any production models, we are just having fun building things :). I am familiar with spear guns and their design and construction, I was more interested in the wood characteristics itself, having one of those "ideas" while shopping for flooring.

He just wants the blanks currently, which I know will progress into me helping him cut the track, trigger mechanism, and other components.

I had not thought of the plywood being the hardwood veneer on the outside and not throughout. That would make be shy away from product completely.

Thank you very much for the information and the links sonny, Everything is useful as i move forward on this.