Sunday, April 13, 2014

Temporary Fixation

I’m making some hollow form branch legs for a table in collaboration with another artist.  The top is a large redwood slab 3” thick and cut into two pieces.  The two sections will be joined by three round bars which span a 2” gap.  In order to get an accurate fit I prefer to have the bars securely in place during the construction but I don’t want to burn any bridges in case the design needs modification later.

The original plan was that the other artist would finish the wood top, including epoxy fixation or the bars, and add a lower shelf.  The epoxy fixation would make any future modification very difficult if not impossible.  I felt like I could achieve the temporary fixation I needed but still reversible if I used Great Stuff foam.  It fills spaces well, has some adhesive property, good rigidity but could be broken up and removed and replaced by epoxy later.

To be more certain about the feasibility of my plan I designed a simple experiment.  I got four clear plastic bottles out of our recycling bin and cut them approximately in half.  I cut four pieces of 5/8” round which is size of the actual joining bars and L welded a 60d nail transversely across one end so I could hang and center the rods.

One rod was left naturally bare.  One rod was lightly coated with linoleic acid grease.  One rod was wrapped in one layer of paper taped to itself and not to the rod.  The last rod was sprayed with WD-40.  I placed all four in holes in the acorn table and sprayed in the Great Stuff space filling foam.

The next day I used a zip disc to cut into the outer plastic so the foam could cure more and later removed the plastic completely.  The rod wrapped paper and the greased rod were held rigidly but slipped out easily.  The other two rods were tightly bonded to the foam.  It was possible to remove them by wiggling them around to break up the foam a bit.

In actual practice any of these treatments probably would work but my plan is to lightly grease the rods and wrap them with one layer of paper taped to itself.  

Rods in plastic bottle sections hung in acorn table pockets and filled with foam.

After the rods were worked loose and the plastic removed.

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