Lee on Deck

Here’s one to please our 11-year-old selves, and the folks over at Low-Tech Magazine: we raised the Carpenter’s Shop using a gin pole.  This is a simple and traditional method for raising a timber frame by hand, and straightforward solution to a site with little crane access.  It’s constructed from a long, straight pole with a block and tackle hanging from the top, and two guy lines (in our case, come-alongs) that help to counter the weight of the pole and the timbers, and locate the posts in their mortises.

This is an eave assembled on the deck. A bent assembly isn’t pictured, but looks similar, rotated 90 degrees

After test-fitting the eaves, we assembled the first bent (like a bread slice of the timber frame, parallel with the gable) flat on the deck so that the post tenons were hanging over their corresponding mortises – so that, when rotated to vertical, the tenons would “tip” into their holes.  The pieces of the bent were fit together so that the tie beam was placed towards the center of the deck and all the exterior reference faces were facing up.  The bent was fit, measured, bound, remeasured, and then pinned and wedged.  Each bent has two ascending and two descending braces, creating an especially stable and sturdy frame.  What original wedges couldn’t be reused were cut from seasoned white oak.  It was satisfying to knock the wedges in tight, locking the half dovetail tenon at the end of the tie beam to the sloped shoulder of the post’s complimentary mortise.  Ah, wedged half dovetails.  We screwed stop blocks to the corners of the sill so that the post feet couldn’t slip off the deck as the bent was raised.  We also screwed two 2x8x16′ pieces of KD to the exterior face of posts, at the top of the post, so that they could be used as kickstands once the bent was nearly vertical.  That completed the first bent assembly.

Lee cut a maple sapling that was at least 18′ long, which is half again as tall as our posts (we realized through trial and error that this could have even been a little longer, but you could realize that sooner using a physics textbook). He attached a block and tackle to the top end of the sapling (again, if one was so inclined, we could calculate the exact number of pulleys needed to create the mechanical advantage to pull the bent up using human-power, but we had a tractor, so we used the block and tackle that Lee had).  Directly beneath the block and tackle connection, we attached two 24′ come-alongs.  That completed the gin pole assembly.

Gin Pole in Tension

We screwed a U-shaped block to the deck at the foot of the gin pole, near the center of the frame, to keep the foot from slipping out of place.  The opposite ends of the come-longs were secured to the rear corners of the deck, so that the gin pole come-alongs and block and tackle created a peace sign on the deck (a peace sign without a circle, and with two extra long come-along legs).  Scott and I lifted the gin-pole into a nearly vertical position, while Lee loped back and forth, tightening the come-alongs as we raised the pole.  Working the come-alongs allowed Lee to center the top of the pole precisely over the bent.  When the pole was leaning forward so that the block and tackle hung directly over the center of the tie beam, Scott pulled down tight on the block and tackle, connected the hook at its base to the center of the tie beam, and pulled down on the free end of the rope (pictured above).  This created a stable triangle of opposing forces (block and tackle, come-along and come-along), securing the gin pole in place about 10 degrees from vertical.  This completed the raising of the gin pole.

Scott pulled down on the raising rope, and, nothing happened.  If we had not had the tractor at our disposal, we would have needed a block and tackle with more pulleys, and a rope with less stretch.  As it was, we hooked that sucker up to a tractor, corrupting the purity of a hand-raising.  For shame! Anyways.  We attached the rope to the front of the tractor as high and as close to the top of the gin pole as feasible.  I reversed the tractor and lowered the arm with all the grace of Kevin Bacon in Footloose as Scott monitored the post feet and Lee let out the cable on the come-alongs, incrementally.

First Bent, raised

Once the bent was lifted past 45 degrees, I set the brake, re-tied my shoelaces, and Scott and I used the 16′ pieces of KD attached to the tops of the posts to lift the bent to vertical, and seat the tenons in their mortises.  We screwed the KD kickstands into the eave sills, and stopped to admire our work. With the kickstands in place, we were able to plumb the bent precisely.  When we satisfied with the bent’s location, we moved the gin pole, and prepared to raise the second bent.

Lee in Tee at 10 degrees

The gin pole was not the only low tech technology employed at the Carpenter’s shop.  Lee used an adze to cut the tenons of the first floor joists, allowing him to work in a tee shirt in single digit temperatures.  After the bents were raised, we used a water level to level them.  On sunny sites, it’s sometimes easier to use a water level than a laser.  If you want to know more about either of these methods, please let me know.

New blue water level hung at reference corner

Sometimes the oldest technologies provide the best solution for the job at hand.  From wedges and ramps to pulleys, I am surprised at how right my physics teachers were about the ubiquity of simple machines.  When applied purposefully, with careful consideration, these approaches can be safer, simpler and cheaper.  While I appreciate the romance associated with historic contraptions, ultimately, romance is not the reason we employ them.  These technologies are selected when they are the most functional option for the job at hand.  We were just lucky to have some fun with them up in Poland.

Tradition! – tra-di-tion!

Completed frame