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Bonding the mast track

Bonded the mast track to the mast this week, and cleaned up the spreader assembly. The mast track was particularly fun - it involved a new chemical (Plexus).

Bonding the mast track

First, I cut tape to wrap around the mast and track at six inch intervals. Then I prepared my plexus gun. There is supposed to be an actual gun you use to apply this stuff - but Swifties being Swifties, Mark invented a new one. I cut down my dowel and PVC pipe to fit into the holes in the end, then duct taped the tube into the large caulking gun. Open up the valve and dispense.

My plexus container didn't have a mixing nozzle on the end - there's supposed to be one there, mine was missing. So I had to mix the two liquids together (I did this in a spent tuna container), take the mixed goo and put into an empty caulking tube (WEST sells them), and then apply to the mast.

Mixed plexus is nasty. It's like very supple bubble-gum - sticks to bloody everything, extremely stringy if you try and pull it apart, gets on everything within 10 inches of it.

I put a bead down the mast between my two strips of guide tape, bead diameter a bit over 1/4”. I then had my faithful assistant (who said "<cough> this smells *exactly* like what they used to bond my braces in place!" - probably - another comment I heard was it smells like what they used to bond crowns in place with.) hold the far end of the track in the air aligned above the mast, while I worked my way down from the tip and pressed the track into the plexus.

The 1/4” bead was *way, way* too much. While the mast track doesn't have exactly the same diameter as the mast at all points (and thus you have to rely on the gap-filling properties of the plexus), the 1/4” bead was just too much and plenty squeezed out. I used a little more than 3/4 of the tube - and I probably could have gotten away with just half the tube. I wound up trying to scrape some of the excess away along the bottom half of the mast, but it was just too gooey.

After about 45 minutes, the plexus had started to gel. I came out and ripped off the tape on either side, removing (most of) the excess. This was tricky - I slid a square tipped mixer stick (a putty knife would have worked well too) along the track to release the goo, while pulling the tape up and away. In a number of places the goo or the tape escaped and I got some on the track or mast. The stuff is so sticky I went through three pairs of gloves just getting it all off.

Were I to do this again, I would definitely put tape on the mast track as well. I got enough plexus on the track that it doesn't look pretty any more, and getting it off now that it's cured is next to impossible. Sigh.

[Update 2007 Aug 1: Bram did indeed recommend putting tape on both the mast and the track, so the excess plexus could be easily removed.]

[Update 2007 Aug 1: A note about the caulking tube. I mixed up a couple of batches of plexus, and the caulking tube has a plug in the end to press out the contents. Getting that plug out was a chore, but I wound up pushing a rod through the tip and into the plug, and all the way out. That way I could reuse the tube for multiple plexus applications, that day at least.]

Spreaders

I also cleaned up the spreaders a bit. Sanded the fillet. After a chat with Bram, I decided they were a bit too long, and took another 1/2” from either tip. Now 32 1/2” shroud tip to tip.

Once that was complete, I applied a coat of epoxy/graphite/407 and let cure. Most of that dripped off, so repeated, this time with the spreaders on their side.

When I cut off the tips, I discovered that one of the tips wasn't full, and the cut took off all the filler I had put in place - so now there's a hole that needs filling. So this time I used the straw trick - which worked *perfectly*.

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Building spreader assembly

Time to actually build the spreader assembly. The rigging manual (volume 2, page 11) describes what has to be done.

• Draw a long line and another perpendicular line on your work area (the garage floor).
• The spreader tips touch the ground 2 3/8” below (toward the base of the mast) the attachment point. (They bisect the angle made by the shrouds going from the chainplates to the tip of the mast.)
• Sand the wide end of the spreaders to fit on the collar. I did the rough shaping with the belt sander, then tried the dremel tool (not effective). Then I found a sturdy paper tube of about the right diameter, and used that (along with a piece of PVC pipe).
• The spreaders should touch both front and back, and have a slight (7°) negative angle of attack - so that when the mast is bent back, they are level with the ground.
• I marked a few alignment marks so I could position everything correctly: centred, positioned 87 3/4” down from the tip of the mast, centred left-to-right.

Once everything was shaped, it was time to fill in the ends. I drilled out the blue foam as far in as my drill would drill - 2 1/2” (although Bram indicated only 3/4” was necessary). Once both spreaders were hollowed, fill with epoxy. Bram had a good trick to get into the deep void and avoid bubbles: use a straw - put straw deep in the void, put syringe in the end of straw, fill up void. Unfortunately, I didn't have the right diameter straw handy. I just kept poking at them with a paperclip to free any bubbles.

With the wide end complete, it was time to trim the narrow end to length. Slowly, to avoid my last mistake. I cut them to 20”, an inch longer than the rigging manual's suggestion (19” along the longest part of the leading edge). At 19”, the spreaders are way too wide - shroud point to shroud point is about 38”. Another cut and we're down to 19”. No further. Shape the ends, drill them out, fill them up. With this, the shrouds will be 34” apart - a bit wide according to Bill's recommendation, but in the ballpark. I'll have a slightly soft mast (probably the right way to lean).

While I was at it, I also lowered the mast jig by 1”; according to the rigging manual, it should be 5” from the surface to the mast track (and the mast track is about 3/8” tall). I ultimately changed my mind and raised it slightly - 5 3/4” to the mast track.

Now it's time to bond things together. I mixed up some epoxy/silica, put a bunch into the wide end, and mushed them onto the collar. Then I found the biggest washer I could and shaped fillets around the spreaders. Put blocks at the tips of the spreaders, ensure everything is aligned, and wait until it's tack free.

At that point, I added on the additional carbon. I used a 8” long piece of 3” uni-carbon, then two pieces of 14” long 1 1/2” wide uni-carbon. It's supposed to be two pieces of 2” - so I overlap a bit and things will be fine. I pus some additional epoxy/silica on the fillets, then applied the tape. Next I placed three pieces of peel-ply over everything, to hold it all tight and probably more importantly to give a surface I could work later. Weight it down, and it's ready to go.

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Varnish

My objective this week was to have something curing in the garage every night of the week. I didn't do too badly either: first application of varnish, and more work on the rudder cassette.

Monday was all about sanding the rudder box, rough-sanding the spreaders, and sanding the ends of the boom. But once that was done, I coated the rudder in layer three of epoxy/graphite, and filled the handle with some of the excess.

Tuesday morning, I put another fill in the handle (but didn't work in the evening).

Wednesday, I did my first bit of varnishing. Of course, before that, I sanded off Monday's epoxy. That complete, it was time to varnish. I'm using Interlux Perfection two-part linear polyurethane, and the first problem was how to accurately measure out the 3:1 ratio required between the two parts. I tinkered with a couple different ways, but Bram had the best idea: use syringes. I cut the tips off two and wrapped tape around the ends - both to differentiate them and to mark a max-amount point.

I sanded down the spars, then wiped them down with acetone. I mixed up a three full syringe/one full syringe mix, and used a 1” foam brush to paint the boom, the spinnaker pole, and the mast base. I did this in the (closed) garage. I think it was Bram who said "when you get to this step, send your family out for the weekend - varnish stinks. It will take a day or so for the smell to filter out." Man o man, does varnish stink. The vapours can cause flash fires. It's ridiculously stinky. I took a shower. I washed my clothes. I (had to) open the garage. I turned off the furnace. I slept on the couch to ensure that the fumes went down, and wouldn't have to open the garage up again at midnight to let another blast of fresh air in. (No, it seems that the fumes are worst right when painting and at initial curing; after that they go down pretty quickly.)

Just to ensure the garage was really stinky, I also applied layer four of black to the rudder box. For this one, I only mixed two squirts of epoxy/207, then painted the tiller handle, and mixed in half the regular amount of fillers (on the assumption that painting the handle would take 1/2 squirt of epoxy). Seemed to work out ok.

Thursday, I put layer five of black on the rudder box, on both sides - I suspended the cassette and coated both sides. This turned out pretty well - the underside began to form drips, but nothing that a bit of sanding won't cure.

Then it was nothing until Sunday. First, I cleaned up the rudder box, which is finally looking presentable (although I did sand through on the trailing edge - another layer required). Then, I did another layer of varnish. First, I sanded the previous layer of varnish to allow the new layer sometime to grip. (I did this with 120; apparently varnish is happy with 220 or even higher). I rested the tip of the mast on a clamp on my workbench, so the other end wouldn't be sticking out of the garage. I mixed up one batch for the boom/spin pole/mast base (again), and a second batch for the mast itself. And this time, I did the entire thing with the garage door open (which made a giant difference).

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