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Workshop flow

A workshop is weeks of gradually accumulating  materials and participants followed by one day of thoroughly enjoyable construction.  As participants arrive, we organize them into small groups to cut fabric and to build multiples of a single part or subassembly: blades, pulleys, propellers, trays,  gussets, and drums.

As trays become available, participants migrate into assembling their own devices.  Building a complete Gray-B-Gon takes about six hours.  Participants are welcome to leave early and finish at home, but make sure they've checked the parts list at the end of the Construction Steps Outline.

We use "parts kits" to accommodate participants who want Gray-B-Gons, but for whatever reasons can't spend the day building with us.  If the workshop enrollment is full, we can still welcome others to come and help out and learn, and to leave with a parts kit.  The materials fee is the same for a parts kit or a completed device.  If practical during the workshop, build a few extra trays to give parts-kit builders a head start.

In the early workshops, the first step was to varnish all the wood parts.  The varnishing and drying time made it difficult for anyone to complete a device on workshop day.  Recently we've invited volunteers to help varnish in advance, and also learn the construction process, so in the workshop they can guide other builders.

Weeks before the workshop

  • Schedule and announce workshop (via JRS) and start building the participant list.
  • Schedule and announce varnishing date(s) to participants.  Ask them to bring materials to the workshop:  old wheels (we stockpile them but hand out our adjusted wheels), stockings and panty-hose, CDs, 5-gallon plastic buckets, folding work-tables, cordless drills and bar clamps.  You may want to put out a regional request for wheels, panty-hose and buckets.
  • Obtain space; evaluate sunburn potential and shade, and a rain scenario.  Pick locations for varnish day: varnishing, drying and storing wood parts.  Pick locations for workshop day: parts storage, the demo evapotron, and a battery recharging area.
  • Collect bike wheels from bike shops and adjust them.
  • Prepare pulley flanges from CDs, bottle bottoms, and dome lids.  (Some participant-provided CDs may also be prepared during the workshop.)
  • Shop for materials.  Hardware stores may need to order some bulk quantities (boxes of 100 carriage bolts, for instance) so allow for shipping times.
  • Cut and sand wood and PVC parts. 
  • Arrange for food and beverages.  Sometimes participants offer to bring group dishes.  Breaking to go out for lunch would probably be a mistake.
  • Borrow tables (several 6-ft folding tables, or similar). 

Days before the workshop

  • Organize tools and materials.
  • Coordinate wheel delivery.
  • Borrow a chop saw.  (Used to trim pvc pipe.)
  • Review checklist.
  • Varnish wood.
  • Train subassembly-building guides.

Builders will learn the construction process from the Construction Guide ("CG"), from the Construction Steps Outline ("CSO"),  from guides' guidance, and from working with one another.  Looking at the demo Gray-B-Gon unit will answer many questions.

Have two or three copies of the CG available, and one CSO for each device to be built.

To keep track of tools I have a box labeled TOOL HOME in a central location, and ask builders to return tools they're finished with.

Keeping track of drill bits is a bigger challenge.  If you can, gather enough drills to have one for every needed drill bit size, label them, and keep the bit in the drill.

Varnishing and guide training

Make up "damp bags" (plastic bags holding damp paper towels)  .

Stir and shake varnish cans. Place the pouring lid on one can; pour about 1" into each mini-bucket.

Set out dropcloth, mini-buckets, brushes, damp bags, drying racks, and shadecloth (for drying small parts).

  Time is about 1/2 painter-hour per device.

When finished, pour mini-bucket contents back into gallon can, and rinse mini-buckets.  Rinse brushes at least 4 times.

With your guides, demonstrate:

  • liner cutting, using blue-taped table scissors, and box for output.
  • tulle cutting.
  • flashing cutting and blade-making.
  • trapezoid drilling, using templates for 3 patterns; nameplate drilling.
  • pulley-groove taping, using 3M tape, measure, scissors, PVC pulley grooves, alcohol, paper towels, and a clean flat surface. 
  • drum building:  mounting, PVC, twine braces, twine lacing, attaching tulle.
  • wheel balancing.

Workshop day early

Arrive at 8am for a published 10am start. 

  • Set out tables, trash can, tools, materials,and demo evapotron (don't set it up yet.)
  • Mark one table with blue tape for cutting liner sheets at 42" and at 55".  Place pairs of tapes, one just before and one just beyond each distance, so there's no question which edge to measure to.
  • Pick one organizer to welcome participants, ask for parts cost payments, update the roster, and give out CSOs and matched sets of wheels. 
  • Any participant whose propeller wheel has a threaded hub should start by building a pulley.  (Gluing is required, and a couple of hours for the glue to set.)  Details are in the CSO and CG, at Step 19.
INTRODUCTION Erect the demo evapotron. Demonstrate the templates, jigs, and wheel clamps.   Show how to open a ball of twine.  Evapotrons may look similar, but all are slightly different.  It's important for participants to use a marking pen to label their trays, wheels, drum axles,  masts, and buckets with their own or their camp's name.

Assure participants that (except when cutting PVC pipe) neatness and precision aren't all-important.  A liner that's wrinkled still holds water.
  • Recruit tray builders (several).  Use the first tray or 2 for clamping wheels upright for propeller assembly.
  • Recruit trapezoid drillers (2).
  • Recruit liner-cutters (2).  Give them scissors, the blue-taped table,  and a container for the cut sheets.  Details are in the CSO at "Cut two liners".
  • Recruit tulle-cutters (2) to cut 2-1/2 yd tulle in half lengthwise.  (Very likely the same crew as the liner-cutters.)
  • Recruit pulley-groove-tapers (2).  Give them anti-slip tape, measure, scissors, alcohol, paper towel, and 1-in. PVC grooves.


Most demos actually build a piece of someone's evapotron.   Present a demo whenever the time is right:  trays are appearing, so demo how to mount masts; a builder asks a question, so give a shout to nearby builders and demonstrate the answer or process.  No one demo will reach everyone, so expect to repeat as needed.

Have materials ready to go; have a bell, horn, or town crier to gather an audience (without stopping everyone's work, somehow.)  Rely on your guides to gather tools and materials and set up a demo, and, as they learn, to present the demo.  Keep the demo moving; rather than stall, be ready to defer questions or switch to a different wheel, etc.

DEMO cover wood with varnish.  Fill the brush,  unload the varnish widely, then spread it thin.  If your brush is too full,  dry it out by unloading drips onto the next area you're going to cover.  Cover end grain and plywood edges by patting the brush face against the wood.  If an area is drippy or too wet, paint over it with a dryer brush.

DEMO build and mount a pulley on a freehub-style propeller wheel (CG Steps 18 & 20).
Materials: taped grooves,  inner and outer flanges, 16ga Cu wires, wire cutters, needlenose pliers; a borrowed propeller wheel with a freehub, clamped on a table, and CG.

DEMO cut flashing; trace and cut blades (CG Step 21).
Materials: flashing roll and cutting jig, box knife, blade template, marking pen, scissors, emery paper, file

Because different wheels have different blade requirements (in size and number), the blade activity marks the end of assembly-line construction and the start of building a personal device.

Set out zipties in a shallow, heavy bowl.

mount propeller blades (CG Steps 22, 23).
Materials: propeller wheel clamped on a table, 8 or 9 blades, marking pen, 1/8" drill, C clamp, zipties.

  • Mount a pulley on your propeller wheel (17, 18, 19, 20).
  • Cut blade shapes (21).
  • Mount blades on propeller (22, 23).
  • Make the drive belt (25).
  • Label and drill the bucket (26).
Recruit tray builders (3,  one with woodworking/carpentering experience).  Details are in the CSO at "Make the Tray" and in CG Steps 8-10.

DEMO  build masts and mount them on a tray. 
Materials: tray, gusset-tray gauge, long and short mast, drilled gussets, bolts, nuts & washers, hammer, carpenter's square, clamp, CG

DEMO mount propeller and balance it.
Materials:  windless location, fully-bladed propeller mounted  on mast, coils of 12ga copper wire calibrated to wheel size, cutters, pliers, blue tape, measuring tape, CG

DEMO mount drum wheels and axle, and rig twine for diagonal bracing.
Materials: tray with masts, 1/4" floor spacers, wheels, A34's, 2 mini vise-grips, axle pieces, PVC clamping jig, blue tape, saw, twine ball, scissors, measuring tape, CG. Ask builders to pause for a guide check before zip-tying the bracing.

DEMO lace drum with twine.  Ask builders to pause for a guide check when they've started lacing.
Materials: tray with drum wheels mounted and braced, twine ball, scissors.

DEMO make drive belt from stocking legs.
Materials: three stocking legs.

DEMO mount liner and bucket.
Materials: Borrowed tray and masts, plastic sheet, 4 cans of beer, screw gun, staples and screws, drilled bucket, panty-hose, twine, scissors, CG

When builders prepare to leave, be sure they check the end of the CSO, "Be sure you take home:"