go to Firehouse magazine Online for published instruction on “lashing a Cribbing Stack”.

https://www.firehouse.com/rescue/vehicle-extrication/article/21284825/lashing-a-cribbing-stack

Shown as 3 Cribbing supports extending the useful range of these tools.

RescueBlox will be distributed small load profile to the entire crib stack.

wood cribbing

light, strong, natural

Compression load is calculated in psi. 4x4’s are a nominal thickness of 3.5”. ( 3.5” x 3.5” =12.25”). This creates a 12.25” square inch column to the ground. 12.25” x 500 psi= 6125 of each column times the number of columns created and loaded by your assembly.

If the load isn’t close to your crib stack load rating. This conventional geometry may be more dangerous to 1st Responders.

If the load we are going to support is under the rating of the crib stack will the overhang be an issue? If we are not close to potential failure, excessive overhang may be more of a liability and less useful to support the load.

Alternating courses 2 members by 3 members creates 6 columns if evenly loaded rated at 36,000 lbs.

If you are carrying 24” cribbing and very large platform can be assembled.

Hybrid Assemblies

Making a Case for 4x6’ cribbing and other alternatives

If you decide to carry 4x6’s for the top and possibly bottom courses of your crib stack they will require less units to assemble a solid deck. Having larger cribbing pieces interface with the load offers more strength per unit than a 4x4. They will resist flipping having a larger midline load area especially when lashed.

This particular piece of Douglas Fir showing its strength with a point load of 16,000 lbs. Not all trees have equal strength but using larger cribbing to interface with the load has many advantages.

This picture shows that the larger the cribbing the more damage it can absorb and remain strong.

During Rescues bigger is better if you don’t have full surface contact

Ok I know I presented in the Firehouse article that the top and bottom courses had to be exactly the same. Well I’m recanting that statement. A slight taper towards the top will not have a noticeable impact on the stability of the stack. The larger lumber makes for a safer interface with the load.

adding RescueBlox

Adding RescueBlox to an assembly will give you an graduated height tool that can be point loaded and distributed more evenly to the crib stack. As a cribbing saver Toe’s Up replaces 12 pieces of cribbing, Step Up and Wedge Up positions replaces 6 pieces of cribbing in relative crib stack members.

The Fulcrum

A 24,000 lbs. assembly If we have 4) 4x4 columns to the ground. The extra cribbing creates a large footprint and secured fulcrum.

This fulcrum or High Center Crib Stack will hold 19,250 lbs. [(5.5 x 3.5)2]500psi

Header assembly

If you need a now support waiting for the specialized equipment a horizontal crib stack with an airbag can be assembled and lowered into the vertical void.