A DIY & home improvement forum. DIYbanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » DIYbanter forum » Do - it - Yourself » Woodworking
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Woodworking (rec.woodworking) Discussion forum covering all aspects of working with wood. All levels of expertise are encouraged to particiapte.

Fir lumber load ratings?



 
 
LinkBack Thread Tools Display Modes
  #1  
Old May 3rd 06, 06:16 PM posted to rec.woodworking
external usenet poster
 
Posts: n/a
Default Fir lumber load ratings?

How can I determine or lookup the load ratings or the load failure point for
a fir plank that is 2 (1.5)" x 12 (11)" x 40"? The plank is oriented widest
side up and level and the load is against the flat side while being
supported with 1.5" ledges on each side.

thank for any tips


Ads
  #2  
Old May 3rd 06, 08:02 PM posted to rec.woodworking
external usenet poster
 
Posts: n/a
Default Fir lumber load ratings?

Try one of these:

http://www.awc.org/calculators/span/...eversecalc.asp

http://www.awc.org/calculators/span/...rcalcstyle.asp

http://www.woodbin.com/calcs/sagulator.htm

If I read your post correctly you have a 2x12 being used as a shelf.
If this is correct, probably none of thes will give you what you want
to know but may point you in the right direction.

  #3  
Old May 3rd 06, 08:07 PM posted to rec.woodworking
external usenet poster
 
Posts: n/a
Default Fir lumber load ratings?


noxpurt wrote:
How can I determine or lookup the load ratings or the load failure point for
a fir plank that is 2 (1.5)" x 12 (11)" x 40"? The plank is oriented widest
side up and level and the load is against the flat side while being
supported with 1.5" ledges on each side.

thank for any tips


Point load or distributed load?

GIven the ineffective orientation it may be that the deflection of the
beam
will be unacceptable long before it breaks, unless you are intentionlly
using it as a spring. If it is loaded to failure, it will fail in
tension, starting
near the middle of the lower surface, uness a point load crushes
fibers in the upper sruface sufficiently to precipitate compressive
failure.

Regardless, it is a simple rectangular beam. You can look up formulas
online for calculating the maximum tensile stres at the extereme fiber
abd the deflection at the center.

Is it construction lumber? 'Fir' is ambiguous. It can be hem-fir or
Doug Fir.

You can look up the minimum strength in bending for hem-fir online,
as well as the modulus of rigidity (Young's modulus).
Then use the formulas for a rectangular beam to determine how much
it will deflect under the intended load and your factor of safety.

If it is Douglas Fir, then use the minimum values for the species group
Doug Fir or Larch.

If you know the particular species, then use the minimum values for
that species.

It is doubtful you will find useful values in any look-up table as no
one uses beams in that orientation for obvious reasons. One
wonders if you should not reconsider what you are doing--will
this be a ramp?

Now, if you want to know what time is is you start by scribing a circle
on the ground out where it will be indirect sunlight for most of the
day...

--

FF

  #4  
Old May 3rd 06, 10:02 PM posted to rec.woodworking
external usenet poster
 
Posts: n/a
Default Fir lumber load ratings?

The Sagulator I think was a good indication. I plugged in the values for
Douglas Fir, used 600lbs load (3x the expected), load concentrated in
center (vs distributed)......and it came up with a 0.1 inch deflection. The
sag limit of L/360 is 0.11. So that sounds like it should be plenty strong
with margin.

Thanks again for the great input!



"RayV" wrote in message
oups.com...
Try one of these:

http://www.awc.org/calculators/span/...eversecalc.asp

http://www.awc.org/calculators/span/...rcalcstyle.asp

http://www.woodbin.com/calcs/sagulator.htm

If I read your post correctly you have a 2x12 being used as a shelf.
If this is correct, probably none of thes will give you what you want
to know but may point you in the right direction.



  #5  
Old May 4th 06, 06:37 AM posted to rec.woodworking
external usenet poster
 
Posts: n/a
Default Fir lumber load ratings?


wrote in message
oups.com...

noxpurt wrote:
How can I determine or lookup the load ratings or the load failure point
for
a fir plank that is 2 (1.5)" x 12 (11)" x 40"? The plank is oriented
widest
side up and level and the load is against the flat side while being
supported with 1.5" ledges on each side.

thank for any tips


Point load or distributed load?

GIven the ineffective orientation it may be that the deflection of the
beam
will be unacceptable long before it breaks, unless you are intentionlly
using it as a spring. If it is loaded to failure, it will fail in
tension, starting
near the middle of the lower surface, uness a point load crushes
fibers in the upper sruface sufficiently to precipitate compressive
failure.


Fredfighter,

2x12 doug fir is plenty strong. A 40" length of it should be able to hold a
few hundred pounds without breaking.
Compressive strength is high too. It would have to be a particularly nasty
point load to crush it enough to make it fail.
Or are you just trying to scare him?


  #6  
Old May 4th 06, 07:30 AM posted to rec.woodworking
external usenet poster
 
Posts: n/a
Default Fir lumber load ratings?


mogura wrote:
wrote in message
oups.com...

noxpurt wrote:
How can I determine or lookup the load ratings or the load failure point
for
a fir plank that is 2 (1.5)" x 12 (11)" x 40"? The plank is oriented
widest
side up and level and the load is against the flat side while being
supported with 1.5" ledges on each side.

thank for any tips


Point load or distributed load?

GIven the ineffective orientation it may be that the deflection of the
beam
will be unacceptable long before it breaks, unless you are intentionlly
using it as a spring. If it is loaded to failure, it will fail in
tension, starting
near the middle of the lower surface, uness a point load crushes
fibers in the upper sruface sufficiently to precipitate compressive
failure.


Fredfighter,

2x12 doug fir is plenty strong. A 40" length of it should be able to hold a
few hundred pounds without breaking.


Agreed, though it is not clear that this is doug fir. It may be
hem-fir.
Regardless, it will bend a lot before it breaks.

It would be about 70 times stronger and 40 times stiffer used on edge.
(back of an envelope calculation late a night), right?

Compressive strength is high too. It would have to be a particularly nasty
point load to crush it enough to make it fail.


Yes, though we have no idea how it will be loaded or how much.
We don't know the application.

We do know that to determine a factor of safety we compare
the load that will cause failure to the design load, right?
To do that, you need to know how it would fail, right?

Or are you just trying to scare him?


No, what gave you that idea?

--

FF

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
What would be your perfect lumber rack? Fred Woodworking 9 September 28th 05 05:11 AM
Dimensional lumber load carrying ability j walker Woodworking 38 April 21st 05 12:48 AM
Heat banks (again!) Dave UK diy 148 September 6th 04 09:45 PM
Toronto area lumber? Pick Woodworking 4 November 20th 03 03:29 PM
NEW EXOTIC LUMBER STO HOMESHOP HARDWOODS LOWHITENER Woodworking 2 September 11th 03 11:20 PM


All times are GMT +1. The time now is 11:01 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.SEO by vBSEO ©2010, Crawlability, Inc.
Copyright 2004-2014 DIYbanter.
The comments are property of their posters.