Thread: One for the experts

Yes because any faults in the timber have been removed or at least are limited to a small section.

I thought it had more to do with the structural grade if the timber.

I.e if something is rated at f17, it didn't matter if it was a solid piece or laminated.

Having said that, I am pretty sure I have seen some laminated beams rated higher than that of equal size in solid timber

I'm on a moulder course in Creswick at the moment so I thought I'd ask the experts at the mill and the answer is yes. Every piece of timber will have a weakest point, but when they're all stuck together they compensate for each other. Also, as long as the top and bottom pieces are strong and clear, you can put pretty much anything in between

I think technically the laminations do make crap timber effectively stronger because the one bad veneer can get carried by the other 11 good veneers. I have used plenty of LVL over the years and some of the end checks and massive knots you see on individual veneers would downgrade a solid timber length to non-structural in no time. But since it is just a defect running 3mm deep on a 35-45mm thick beam, there isn't much to worry about. With that said, I think the timber species still needs to be able to make the F17 grade. They make LVL from oregon/fir and iirc oregon is reaching its structural limits at F17ish. Gotta be careful with the laminations though, I have opened many packs, said "what the!!!" and told the boss to send the entire pack back to the muppets due to complete delaminating.

Laminating increases the strength of a given sized beam considerably. Vertical veneer laminatig is the most recent concept. Not only is beam strength increased, stability is also greatly enhanced. These beams are only as good as the bonding performance of the adhesives used. I too have seen serious delamination in LVL material that should never have left the factory. Back in the 70's I was responsible for the marketing of the original horizontal laminated beams in Australia. In my humble opinion, I feel the quality was better then that what I see on the market today. I guess cost is a factor, but structural integrity must be maintained for the product to be acceptable.

OK, I'll come clean. Having seen the high price of Plano wall clamps, I'm thinking about making a set myself and I need the vertical members to be a stiff as possible. So I thought I might rip down some sticks of 100mm timber and epoxy them back together in the hope I would make them less prone to bending under load.

If through the thickness of the beam, the fibres are interrupted by one or more layers of unyielding material, it might reduce the tendency to bend. The same approach might apply for making cauls instead of having to shape them convex.

mick

If you go that route, it'd probably be best to randomise the pieces when you glue them back together, otherwise you'll just be putting weaknesses back where they came from.

Stiffness and strength are two different properties, although related. In a laminated beam, the outer plies provide resistance to bending; the inner plies keep them in position, as well as resisting shear deformations.

All other things being equal, convex beams (thicker at mid-span) will be stronger and stiffer than an equal amount of material distributed uniformly, i.e. thinner at mid-span.

There's no such thing as "unyielding material."

A picture of your concept might clarify.

Cheers,
Joe

if you are just going to make plano clamps. anything straight solid/laminated beam will be good enough for the beams. When you apply clamping pressure, the two beams get put under tension. So think about how "stiff" a tightly pulled piece of string is. even slight bow/spring will be pulled out with the clamping tension.

Personally, I reckon your wasting your time. The system is brilliant and looks simple, but there is a bit more to it than meet the initial eye. I bit the bullet years ago and paid quite large dollars to ship some from the States. Never regretted the decision for one minute. In fact, bought more. There is a forum member who was selling an identical item that he was importing, Aldav I think. A couple of others have bought from him and been happy. Not sure if he still has stock though.

Cheers
Bevan

You can always reduce the deflection of a beam by gluing a sheet of steel on the side that will be stretched. Easy to do and doesn't alter the size significantly but will make a big difference in stiffness, the glue would have to be something like a flexible epoxy. A steel sheet on the opposite side will also help.

In the end why not just use an RHS in heavy gauge.