Saturday, September 19, 2009

Fire the Lasaah!

Assembling the 8 staves into something resembling a straight stick would be pretty easy if the mast was untapered.  Since the GIS mast is tapered at both ends it's a bit difficult to eyeball straight, although probably doable with practice.  I tried using string and I think it would be OK but I'm allways in favor of applying maximum technology to solve a problem.  So out came the laser level and why limit yourself to one when your buddy has one too.  We set up two laser levels shining down the mast length at 90 degrees to each other.  This worked well but there was one complication.  The staves are tapered on only one side, opposite the bird's mouth cut so it appears that you can't just mark off a centerline down a stave and use that as a guide because each stave actually twists a bit as it bends to accomodate the taper. At least that's what it looks like to me.  Trying to think through this geometry makes my head hurt.  Anyway the aparent twist is not a lot but may be enough to cause a bend in the mast if a stave centerline is used as a reference.  To get around this we set the two laser beams to cross at 90 degrees in the center of the mast base. The horizontal beam was set parallel to the straight work surface that the untapered section of the mast was lightly clamped to.  The mast was then wiggled around such that the center of the opening at the mast tip coincided with the intersection of the two laser beams.  The actual intersection is not visible but can easily be eyeballed from where each laser line hits the mast tip.  Theoretically this setup aligned the base and tip concentric to each other.  The rest of the mast was eyeballed straight following the laser line.  Tomorrow, after the epoxy is set, I get to find out if all this goofing around with lasers made for a straight mast.  By the way I think just clamping the untapered section to a straight workbench or whatever and then eyeballing the rest of the mast would result in a maximum bend of probably not more than 1/4 inch at the tip.  At least it seems that way because the mast did not have to be moved much to align with the laser lines.

Epoxying the mast is a 2 person job, minimum.  At Michael Storer's suggestion we glued all but two opposing joints.  This will allow the mast to be split open for thorough epoxy coating and installation of  base, partner and tip reinforcing plugs.  The two unglued joints were covered with brown packing tape to prevent any stray epoxy from bonding them.  We turned all the staves bird's mouth up and spread epoxy, slightly thickened with wood flour, on each stave.  It took double the amount of epoxy I thought it would.  We started with 6 oz of epoxy with enough wood flour to increase the volume to maybe 7oz.  And ended up mixing a second batch.  Probably could have used a bit more as there are a few spots where barely any epoxy squeezed out.  Once all the staves were assembled I used brown packing tape to wrap the mast while Dave, my helper, held it together.  The packing tape worked pretty well.  The nicest thing about it is that it's thin enough to not interfere with the mast laying down flat on the staright reference work surface.  We also wrapped the mast with thin line and I liked the way that pulled the staves together.

One thing I would do differently is to cut the staves a bit long, maybe an inch or so.  I cut my staves to the exact length shown in the plans. After all of the tightening and wrestling with the mast it ended up with about 1/8 inch of stagger between stave ends.  The ends started out well aligned but the process of clamping the mast slid a couple of the staves a bit.  No big beal the mast will just end up about 1/4 inch shorter than specified after both ends are sanded flat.  This could be easily avoided by starting out with slightly over length staves.

Dry run aligning mast.  I used my foil shaping jig placed on the table saw as a flat reference surface.

Two laser levels 90 degrees apart used as reference lines to ensure a straight mast (I hope).  And yes, I removed the one clamped to the garage door before opening the door but forgot to remove the bit of ply it was clamped to .......


The laser lines set up to intersect at the center of the mast base.


Lasers are cool.

Even cooler with the lights out.

Total time to date: 90hrs

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