Right category?  Hope so.

Need to know the maximum load that can be applied to a wooden plank 2"
x 10" x 10'.  The plank in question is a simple kiln-dried pine,
typical of lumber found at any home improvement store.

The plank will be positioned with one end on the ground, a solid
surface.  The other end will be approximately 24" off the ground. 
There is no other bracing or support along the length of the plank.

I recognize that you may not be able to nail this down to the ounce,
but a well-supported approximation will suffice.  I also know that
support strength may vary withe the actual cut of the wood, but the
same well-supported approximation will serve.

Thanks in advance

---

Clarification of Question by edrox-ga on 19 May 2003 22:29 PDT

Maybe this will help.

I am trying to use two planks of 2x10 for ramps on a car trailer.  Due
to the ridr height of my race car, the ramps need to be a *minimum* of
8' long,  Vehicle weight is approximately 1600-1700 lbs - and will be
winched up, so no driver is necessary inside the car.

I picture this like a diving board 24 inches above the water, which
will likely break when 440 pounds = 200 KG presure is applied when a
heavy person does fancy dives. The diving board would be made of
optimised lumber or composits, so the lumber yard pine will likely
break at about 110 pounds = 50 KG. Even 22 pounds (10 KG) will cause
the free end to sag from 24 inches to 23 inches. Diving boards
typically break close to where they are anchored, and so will the pine
plank. The design of the anchoring assembly can distrubute the stress
over more length adding (or subtracting) perhaps 10% to the failiar
force. If the anchor involves lots of nails and screw holes that is
the point of likely failiar. Also a foot or more of the 10 foot length
is involved in the anchoring process, reducing the effective length
supported to 9 feet or less. This increaces the failiar load by 10% or
more. I think the breaking force increases at least five times if it
is applied in the 10 inch direction, but even a small additional force
breifly in the two inch direction is likely to cause the plank to
twist and fail. It is standard practice to reject any planks with
knots, cracks or blemishes near the anchoring end and figure about
half the breaking strength as a safety factor.  Neil

I am having a hard time swallowing this Neilzero.  You are saying that
a plank 2" x 10" x 10' , supported on both ends, will support only 120
lbs?  I know I have had over 400lb load on this with no signs of
sagging or breaking.

for clarification:  think of this as a ramp from the ground to a
trailer, with the 10" surface bing horizontal.  Think 10' ramp, 10
inches wide by 2 inches tall.

If this board is really 'typical of lumber found at any home
improvement store,' it is probably a 2x10, which has dimensions 1.5
inches thick by 9.25 inches wide.  If this is the case, it is only
about half as strong as it would be if the dimensions were really 2"
by 10".

The answer also depends on where along the board the load will be
applied, and whether it will be concentrated in one point, distributed
evenly along the length of the board, or some other distribution.

According to this OSHA site:
http://www.osha.gov/SLTC/etools/scaffolding/planking.html

The maximum intended load for planking for a 2" x 10" at 10' is 25
lbs/sq. foot.
If I did my math correctly, the square footage of that plank is 8 1/3
sq ft.
Assuming the load is distributed evenly, up to 208 lbs can be safely
supported if it is being used as a plank.

However, since you have the plank at an angle, some of the weight will
be transferred along the length into the ground. It's been a long time
since I took a statics class, but I estimate that approx 20% of the
weight will be transferred along the length of the beam, thereby
increasing the maximum safe load from 208 lbs to only 250.

This is the maximum recommended for safety reasons, you may find that
the actual load it can take is much higher. However, the more stress
you apply, the weaker the wood becomes over time.

Check out this web site.  You might also call them.
http://www.highlandinteractive.com/category_products.asp?id=82&template_id=6
800.234.6992
They make ends for 2X10 ramps.
Good luck!