Planning for a Roubo bench

Some years ago, my dad came to visit us and took the opportunity to build a pergola over my backyard deck. To build it, he used some really massive white pine slab cut on demand by a nearby sawmill. To give some proportion, the two main posts are 10"x10", the rafters are 4"x6" and the main rail is 4"x10".

Quite a massive frame.

Since then, I have some leftover that are drying for 4 years in my backyard.

A bucnh of massive slab waiting to find their utility.

These left over are white pine and of the following size:

• One 10" wide, 4" thick, 17' long.
• One 7" wide, 5" thick, 9' long.
• One 5" wide, 4" thick, 17' long.

This one will be cut in two pieces and assembled.

Looking at the size of these pieces, they would be a perfect choice to build the Roubo bench I want for such a long time. By assembling the first two slabs I will get a 27" wide, 8' long, 4" thick top. The central part would be 1" thicker, I may plane it to 4" or leave it as is, not sure yet.

The bench top, made by assembling two 10"x4" with a 7"x5".

 The last slab will be cute to make the legs that will be 4"x5" and 32" in height.

While I like the way Christopher Schwarz built the Roubo bench in his book "The Workbench Design Book", I want to be able to dismantle the bench to make it movable if needed. In other terms, I neither want to glue the stretchers tenons nor to use dowels to lock the legs and the benchtop. Not that I plan to move it here and there but if I build a Roubo bench, I want to keep it and bring it with me in the event I move to another place.

For the assembly of the legs and bench top I don't see it as an issue as the bench top should be heavy enough and the joints strong enough to keep everything in place.

This leaves me with a challenge, how to assemble the stretchers so the bench is stiff enough that it does not rattle and at the same time keep the ability to dismantle it (at least the legs) so I can move it to another location. I know that this can be easily achieved using some nuts and bolts but I do not want any nut nor bolt on my Roubo. One solution to this could be to use tusk keyed through (Thank you Bob) tenons.

For those who don't know (I guess you all know but just in case), a tusk keyed through tenon is a tenon locked by a wedge going through it.

Illustration of a tusk keyed through tenon.

Hopefully the wedge would be tight enough so the bench will remain stiff, and even if the wood dried a bit, I guess that one or two hit on the wedge with a mallet will tighten it enough from time to time.

Before starting to cut everything to length I need to build some strong sawhorses, but that is another story...