BS: Inherent strength of wood!

Subject: BS: Inherent strength of wood!
From: Dave the Gnome
Date: 08 Nov 16 - 08:25 AM

Daft question but I am sure someone here can explain. Or, if not, at least make something up :-)

I have recently had to replace the centre rail of a double bed - One that runs right down the centre from headboard to footboard. It was roughly 2" x 2". Planed, which makes it a bit smaller. What I did notice was the one I replaced was actually 2 pieces of 2x1 glued together and, due to how it had to be inserted, had the join running vertically.

Now, due to the nature of the beast, I have put an extra couple of legs along its length for extra support so it should no longer matter but why would the original be as was rather than a piece of 2x2? Which is stronger? Any ideas? Does it matter?

Never mind Presidential elections and Brexit. These are the things that matter!

Cheers

DtG

Subject: RE: BS: Inherent strength of wood!
From: DMcG
Date: 08 Nov 16 - 08:39 AM

No idea, but here is one fact and one thing made up!

Since the glue joining the parts is vertical, there is no force put upon it im normal circumstances so it is not there to increase strength in the obvious manner.

Now, any piece of wood, being a natural product, has areas of strength and weakness. For example, it may have knots. If the thing was 2×2 that knot runs across the width of the whole thing and forms a point of weakness. By using two separate pieces where there is a knot on the left hand side there is unlikely to a knot on the right hand side. So the piece overall is stronger. And the glue helps distribute the stresses so that a significant area of each side helps to support the other.

Subject: RE: BS: Inherent strength of wood!
From: Steve Shaw
Date: 08 Nov 16 - 09:07 AM

I'm sure I read somewhere once that good wood glue, properly applied, is actually stronger than wood. Good points too, DMcG. We don't half know how to sort stuff out on this forum!

Subject: RE: BS: Inherent strength of wood!
From: Dave the Gnome
Date: 08 Nov 16 - 10:18 AM

Hence the reason I asked on here rather than a woodworking site :-D

Thanks Scottish cousin McG!

Subject: RE: BS: Inherent strength of wood!
From: Rapparee
Date: 08 Nov 16 - 10:28 AM

Get gnu to weigh in on this. He's a real, rootin'-tootin' engineer.

Subject: RE: BS: Inherent strength of wood!
From: bobad
Date: 08 Nov 16 - 10:41 AM

My two cents:

A failure in a piece of wood in this use would most likely occur longitudinally, along the grain which is fairly uniform in a single piece. With two pieces glued together longitudinally their differing grain patterns would, conceivably, reinforce each other.

Subject: RE: BS: Inherent strength of wood!
From: Greg F.
Date: 08 Nov 16 - 10:47 AM

why would the original be as was rather than a piece of 2x2?

- Could be, depending upon how the grain was aligned in the two pieces that gluing it up out of 2 pieces made it stronger/more dimensionally stable.

- Could be a cost-cutting measure as smaller and smaller diameter trees are harvesteed, larger dimension lumber can be more expensive & thus is often pieced up from smaller dimension lumber.

- Could be something entirely different.

Subject: RE: BS: Inherent strength of wood!
From: Greg F.
Date: 08 Nov 16 - 10:48 AM

Ooops - halfway cross-posted with Boo.

Subject: RE: BS: Inherent strength of wood!
From: Stilly River Sage
Date: 08 Nov 16 - 12:04 PM

My Industrial-Arts-college-major ex taught me years ago that in carpentry the glued pieces are stronger together than a single piece the same size. He also suggests using a bar of soap along the edges of drawers so they open and close smoother.

Subject: RE: BS: Inherent strength of wood!
From: keberoxu
Date: 08 Nov 16 - 03:02 PM

Well, until Gnu gets here, I will bore you all with this digression:

in the Chinese system of acupuncture meridians,
there is at least one school of thought
that focuses on The Elements.
And there are more than four elements. There might be as many as six.

Metal, for example, is an element,
along with fire, air, water.

AND....so is Wood.
The element of Wood, I was told, corresponds to the season of Spring,
with new life springing up and sprouting through the earth.
Sprouting things, though they be not at all woody, demonstrate
the element of Wood in dynamic action.

Subject: RE: BS: Inherent strength of wood!
From: Bill D
Date: 08 Nov 16 - 03:04 PM

As a woodworker, I can say it depends on type of wood plus direction of grain..... and plywood would be more resilient than many types of solid wood. In the circumstances, DtG's solution should be quite adequate.

In a 6 foot+ length, one would have the grain parallel to the floor, thus subject to bending. Simply adding a thin plywood edge to the original piece..(on both sides, preferably)... would likely have served also. I imagine that 2 1X2s were probably cheaper than a 2X2 to manufacture.

Subject: RE: BS: Inherent strength of wood!
From: punkfolkrocker
Date: 08 Nov 16 - 03:15 PM

I need to get a mahogany guitar neck fixed - a good quality les paul copy,
the Headstock is terminally cracked at the nut and separated from the rosewood fingerboard...

All research indicates a well glued repair by a decent guitar tech,
should be as strong as new.

Subject: RE: BS: Inherent strength of wood!
From: Ed T
Date: 08 Nov 16 - 04:58 PM

Properly glued multi- cross grain is generally stronger than a regularcsimilar material piece of wood. However, it depends on the application, as engineered wood is normally produced for a specific application. Add moisture, and all bets are off.

Subject: RE: BS: Inherent strength of wood!
From: Dave the Gnome
Date: 08 Nov 16 - 05:06 PM

All good stuff. Thanks one and all. They said they would deliver a new part but they have not as yet. As the solution I provided cost the whole of £4.26 I am not bothered but I will be interested to see what replacement they send.

I will keep you posted.

DtG

Subject: RE: BS: Inherent strength of wood!
From: Steve Shaw
Date: 08 Nov 16 - 05:16 PM

Bedposted?

Subject: RE: BS: Inherent strength of wood!
From: punkfolkrocker
Date: 08 Nov 16 - 05:20 PM

Very entertaining and informative youtube video from Crimson Guitars repair workshop channel..

My kid broke my guitars headstock, let's test some new Alcolin wood glue!

The comments below this video are a good serious debate on the merits of different wood glues.

Subject: RE: BS: Inherent strength of wood!
From: Dave the Gnome
Date: 08 Nov 16 - 05:31 PM

What's the matter-ess, Steve? I think you have all the jokes covered. Trying to make me look a pillow-k?

:D tG

Subject: RE: BS: Inherent strength of wood!
From: Joe Offer
Date: 08 Nov 16 - 11:21 PM

In recent years, the use of laminated beams has become very commom in construction. I've heard they are much stronger than solid wood beams. I have even seen them used in situations where the beams were once made of steel. The grains are not chris-crossed like in plywood.

Subject: RE: BS: Inherent strength of wood!
From: Steve Shaw
Date: 09 Nov 16 - 05:43 AM

I may have some more bed jokes somewhere, but unfortunately my memory's turned to foam...

Subject: RE: BS: Inherent strength of wood!
From: Ed T
Date: 09 Nov 16 - 01:04 PM

Laminated floor beams (silent floorng) have excellent load capability over long expanses , if used as (engineered) intended. However, moisture is a threat.
Orienated Strand board (OSB) sheathing has good strength for that purpose ( not as good as more expensive plywood) but limited strength in other apllications - and loses strength if exposed to moisture -even if later dried out. Some special application OSB materials have resins and waxes added to give added water tolerance, such as roofing material.

Subject: RE: BS: Inherent strength of wood!
From: Dave the Gnome
Date: 09 Nov 16 - 01:39 PM

Would combining moisture and bed jokes just result in me being a wet blanket?

Subject: RE: BS: Inherent strength of wood!
From: Bill D
Date: 09 Nov 16 - 03:38 PM

More problems...

I'VE GOT TEARS IN MY EARS (FROM LYIN' ON MY BACK IN MY BED WHILE I CRY OVER YOU) (Harold Barlow)

I've got tears in my ears from lyin' on my back
in my bed while I cry over you.
And the tears in my ears, they're off the beaten track
Since you said "It's goodbye, we are through"
So if I should get water on the brain
You will know you're the one who is to blame.
I've got tears in my ears from lyin' on my back
In my bed while I cry over you.

I've got tears in my ears from lyin'on my back
In my bed while I cry over you.
I've been cryin' these tears and soakin' in my sack
Since the day I found you were untrue
And if I don't get up pretty soon
I'll turn into a sleepy lagoon.
I've got tears in my ears from lyin' on my back In my bed while I cry over you.


I've got tears in my ears from lyin' on my back
in my bed while I cry over you.
It's been so many years, my sacroiliac feels
as though it's been soaked through and through
Oh, you lied when you said we'd take the plunge,
Now I know how it feels to be a sponge!
I've got tears in my ears from lyin' on my back
In my bed while I cry over you.

Subject: RE: BS: Inherent strength of wood!
From: Rusty Dobro
Date: 10 Nov 16 - 11:38 AM

My wood's not as strong as it used to be.....

Subject: RE: BS: Inherent strength of wood!
From: Steve Shaw
Date: 10 Nov 16 - 11:42 AM

These bed jokes don't always go down well, duvet?

Subject: RE: BS: Inherent strength of wood!
From: Dave the Gnome
Date: 10 Nov 16 - 01:29 PM

That's the lot I think, Steve. Time to retire...

Subject: RE: BS: Inherent strength of wood!
From: Dave the Gnome
Date: 10 Nov 16 - 01:29 PM

Unless of course you can think of one for eiderdown there?

Subject: RE: BS: Inherent strength of wood!
From: Steve Shaw
Date: 10 Nov 16 - 01:57 PM

Put it to bed now, Dave, and I hope that last joke I pulled out of my pocket sprung a surprise on you...

Subject: RE: BS: Inherent strength of wood!
From: Raedwulf
Date: 11 Nov 16 - 06:07 AM

Will you sheet up with the bed puns (I will not dignify them by calling them jokes! :p ).

As for laminates, why laminated bows, for example? I'm no expert on wood, but I am a longbowman... A bow needs two opposing properties - elasticity (the ability to bend without breaking) and rigidity (the desire to remain in shape). These aren't quite the actual technical terms, but you will immediately spot that:

* A bow that merely bends will probably drop the arrow at your feet when you release the string.
* A bow that won't bend... Will break if you can manage to bend it at all.

My "Old Faithful" is a 50lb draw one piece ash longbow. But it comprises both heartwood & sapwood. One (the sapwood, I think) provides the elasticity that stops it from breaking; the other the rigidity that provides the power when it springs back into shape. Modern longbows (AKA Victorian longbows) are invariably laminated. Because it's a lot easier to find a piece of wood with one of the qualities than with both. So you glue them together & the sum is greater than its parts.

Incidentally, as eny fule knoe, yew is the best bow wood (ash comes second), but the famous English Longbow... was almost invariably made from Mediterranean yew. Back in the day, if you exported X amount of wool, I think it was, you were required (as a tax, sort of thing) to import a certain number of bow staves. English yew, with a shorter growing season, has thinner rings & more knots. These days, if you can lay your hands on a yew bow (expensive!) it will almost certainly be jointed in the handle i.e. made from two billets, as finding one piece good enough is nigh on impossible. Which reinforces (fnarr!) the point about laminates & a join not necessarily being the weaker part of proceedings!

Subject: RE: BS: Inherent strength of wood!
From: gnu
Date: 11 Nov 16 - 08:43 AM

DMcG + bobad = A+

I have a pic of a hunting camp with chipboard gusset plates in the roof trusses. I took the pic in March. Nice wood stove... the stove was about all that could be easily seen sticking up through the roof. The front wall was still standing, a bit crooked, and the door was "ajar".

BTW, such pieces are visual inspected and randomly selected pieces are stress tested. Alas, some will fail, ergo, this thread.