catzooks.com

Slooooow

So much for the best laid plans. Things are going pretty slowly. Perhaps it's the fact that I'm in parenting class every Wednesday (and reading the required reading one night a week as well). Going to Toronto for week-long recruiting trips doesn't help any either. Perhaps it's the fact that work is crazy stressful - new boss, trying to keep up with the art. Or perhaps it's the fact that I'm not having too many successes recently. But I'm certainly not on the schedule which is going to let me sail this summer...

Rudder box

I finally built the rudder box (after preparing for so long). I wanted to have the final coat of black on before doing so (since it adds a teeny weeny amount of thickness). With that done, it was time.

I was chatting with Bill about how he built his rudder box. His answer:

I wrapped the rudder in a thin cotton towel to provide the thickness that I thought that I would need to allow installation of the fuzzy Velcro tape as my packing material for the rudder. Over that layer, I wrapped plastic sheeting and taped it closed tightly around the towel. My layup consisted of an absorbent layer, peel ply, s-glass, several hybrid layers, another s-glass layer, peel ply and absorbent cloth. I made a vaccumn press with plastic sheeting over the whole layup and rudder and my shop vac to compress the layers. The top and bottom edges were trimmed to fit between the gudgeons and then they were wrapped in carbon tape to a thickness that would position the nylon spacers away from the leading edge of the cassette. The nylon spacers were held in position for the final tape wrap with a wooden jigs that I made that fit over the leading edge of the rudder and had a hole drilled in each to hold the pintel parallel to the leading edge. There were extra spacers that completely covered the pintel for the entire height of the cassette. I masking taped the jig pieces to the rudder and positioned the breaks in the spacers such that they would be inside the tape wrap. The spacers were then over wrapped with more carbon tape and several top layers of glass tape. Take your pintel to Home Depot and find the nylon spacers that are 1" in length.

Well, that got me going. I just had to try vacuum bagging. I have the Gougeon publication 002-150 Vacuum Bagging Techniques and I spent an hour flipping through that to get ideas.

I had a free afternoon, so I wetsanded the centreboard (with Tristan's assistance). Still a few scratches to get out - I need new 220 grit paper.

Time to get started. I wrapped the rudder in just under 1/16” width of newspaper. I built a bag using 2mil plastic sheeting and 3M mounting tape for the edges. I didn't have quite enough, so I used plain packing tape where I ran out. I screwed a board into the edge of my workbench (nice to have a workbench I'm comfortable doing that to), and then clamped the rudder to it, so it would stay vertical (and with trailing edge up).

Then it was time for the actual layup. I wrapped a piece of mylar around the newspaper, then a piece of muslin (not all the way into the trailing edge, so threads don't get stuck in there), then a piece of peel-ply. The peel ply was held in place by a piece of tape sticky side out and holding the ends on either side of the trailing edge (again so I don't have to dig out the threads). I drew red lines 9” apart on the peel ply so I knew things were going on straight (and these lines helped a lot).

Then lay it up. Two layers of 30”x9” s-glass, one strip of 50”x9” carbon, one strip of 50”x8 3/4” kevlar; one final strip of 30” s-glass. Then peel-ply, pink cotton, and a layer of musquito net as a breather layer. All this layup took about 13 squirts and went really quickly - I used expoy/206, and really I should have used 205. I had the entire thing layed up in 40 minutes.

I then put the entire rudder into my plastic bag, taped the bag shut, cut a hole for the tube, taped the end of the vacuum to the tube, and flipped the switch. My vacuum was clearly struggling - there wasn't so much leakage that this would be ineffectual - and that caused it to heat up. I took the vacuum itself and put it outside the back door, so at least it had some cold air to vent in and out.

At 4am, I decided I'd turn the vacuum off - the epoxy was pretty solid by this point (the brush I used to apply the epoxy was getting pretty hard). Overall the vacuum did suck a lot of excess out of the layup. The bag was pretty pathetic though - without the constant suck of the vacuum, it would never have held the vacuum.

With that all done, it was time to see how it worked. I stripped off the outer layer slowly - getting off a strip from top to bottom was the hardest part. I just pulled off pieces of the cotton with pliers. Another trick is to slip a putty knife between the cotton and the peel ply (not the ply and the part) - and slide it apart. Once a strip comes off, getting the rest off is pretty easy.

After that, I had to pull the box off the rudder. This proved difficult. I figured with some tapping I could slide it right off - but I was so effective at making sure everything was tight, it won't budge. So I started to cut out the newspaper between the box and the rudder. What a hassle.

In hindsight, I would probably do the following differently:

• Use real mastic tape for the bag. It's cheap. It works way better than what I did (I certainly hope). I had lots of leaks around the bag, which mastic would hopefully solve.
• Use a real valve. They're cheap - $16.65 for three (look for "West System Vacuum Cups"), and they would be much better than my taped-together improvisation.
• Figure out some better way to pull the box off the rudder. Removable newspaper? Leave an edge of paper along the top? Put tabs of tape along the top to pull on?

I'll also say that this process worked quite well - the layup seems pretty good from what I can tell so far. Using this method (even this Frankenstein approximation) would have been much better on some of the small parts.

[Update 2007 Mar 12: A few links after the fact. In a conversation with Greg, he mentioned that vac-bagged parts can actually be weaker than non-vac-bagged, because the width of the epoxy layer allows outer layers less flex. (This would be true on a rudder for instance - because layers are further from the core in regular layup than if they were vac-bagged, the rudder is wider and thus when flexing the opposite edge is under tension, and because it's further from the core, won't flex as much.)

I found a few good overview sites describing some vac-bag techniques. Bertram31 has a good overview. Fibre Glast, a supplier, has another overview (as well as products). Building wings (vac-bagging is really popular in the model airplane/rocket underground). Using a FoodSaver as your vacuum source.]

[Update 2007 Jun 19: Bram posted his PDF on how to build the rudder cassette. Of course, it's much easier than what I went through. Sigh. Local copy.]

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Trailers

I was on a recruiting trip to Toronto all week this week - and so nothing was accomplished. But I did enjoy some fine French Canadian cuisine.

I figured I'd put up some links I've had kicking around for a while now: trailers. I've mentioned trailers before, but haven't really searched far and wide. The problem has been determining what qualities to look for - it seems like pretty much everyone builds trailers, and differentiating between good and bad can be tricky. Overall, these seem like good starting points: NMMA Trailer Certification Program and NMMA Certified Trailers. Surely a manufacturer in there has something decent.

A few possible starting points:

• Seitech
• About's comments
• EZLoader
• Zieman
• A thread on catzooks about trailers

Continuing on the rudder

Another coat (the final one, I hope) on the rudder and centreboard this week.

But first, because I've widened the centreboard trunk hole in the boat, the insert block is now a bit too narrow to fit inside. So I wrapped it with a layer of 2” glass tape, a layer of carbon tape, and another layer of glass, to fill up some of the extra space. This wasn't quite enough width, and I added another few layers: 1x 2” glass tape, 2x 2” carbon tape, 1x 2” glass tape. That was sufficient. With the excess epoxy, I sealed the edges of the actual hole (no more shaping - it's done).

Then, another overnight epoxy application — one, two, three. This is the fourth application - one (I can't believe that was in December), two, three (filler). And hopefully the last — I used epoxy/207 this time.

It's been my habit to flip the boards over after each application, so the drips go opposite directions. But the first application was tip down, and the board wanted to roll forward (you'll notice the tubes with weights holding the board in place so it doesn't fall forward). Thus I only flipped them once, and after that kept them tip up. After all, it hardly matters if I started tip down or tip up for three applications...

The following day, I gave them a quick sanding of the exterior to get the high spots down. Next step: wetsanding. I didn't want to sand everything to grey, I'll let the 220 grit do that. (The epoxy at this point isn't rock hard, either - sanding was very quick.) There are small (1mm) "bubble holes" on the upper sides of both boards. I'm not sure where they came from - it's the first time I've seen something like this.

At around 10am, Pascal escaped into the garage and tried to walk by the boards, and put his hand into the not-quite-cured epoxy on the centreboard. He got it all over his left hand. I immediately cleaned his hand (having learnt my lesson the hard way) - two solid scrubs with acetone laden paper towel, then a scrubbing with Orange Goop (which kinda works to remove epoxy, but certainly not as effectively as a thinner like acetone), then a scrubbing with standard soap, then another scrubbing with a scrub brush and standard soap. I'm hoping he doesn't suffer through what I did (and so far, he seems just fine).

Finally, I cut the materials for the rudder box. The distance between the gudgeons is 8 3/4”; I cut everything but the hybrid at 9”. One wrap of the rudder is 21”. I cut enough material for two wraps each of carbon and hybrid, and three of s-glass. The hybrid and carbon is 50” wide, and I just cut off an 8” strip. The s-glass is 30” wide, and I cut three strips, so it will overlap quite a bit. Overall, it's a good thing I bought too much during my order for the rudder and centreboard (despite my thinking I wasn't overbuying too much...)

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Cutting the centreboard trunk hole

Two things this week - rough-cutting the centreboard trunk hole, and filling the tips of the centreboard and rudder.

When I cut the hole, I just sat down and started cutting. I (roughly) measured using the distance from the inner trunk walls to make the width about right. I used the rasp to take down the biggest area, then used the dremel to get into the corners. I also put the routing base onto the dremel and ran it along the edge of the square to get a straight line along the edge. Overall it didn't take long at all - an evening.

I probably overcut on the starboard side, perhaps by as much as 2mm. (You can see this in the picture - one strip of yellow cedar is thinner than the other.) Were I to do this again, I would mark two parallel lines on either side of the line exactly 23mm from the centre line, and then gradually work my way out to that line. Then the insert would be centred on the deck. (Although this may not be entirely desirable. If the trunk isn't dead-on-centred, it means that the board won't be centred in the trunk, and so the extra width is even more necessary to ensure the board fits in the trunk. And I know mine is out by about 1/8”.) I'd probably also move the bevel blocks out from the centre by at least 1/8”, perhaps 3/16”, just to allow more space for the insert.

I also discovered that there is a bit of a gap between the Pro-Set and the deck. I'm freaked out about this - I spent an evening killing things to calm myself down - but there's absolutely nothing I can do. So I syringed a bunch of epoxy into the gap and hoped for the best.

I also cleaned the tips of the boards and melted out the trailing edge of foam with acetone. The acetone dribbled way into the board, and I melted more than I wanted - 5” on the trailing edge of the rudder. (The leading edge of the rudder was about 3” deep, and the centreboard didn't really fall prey to the acetone.) I filled all that up with epoxy/407 and waited for it to get relatively solid.

The second application was a mix of epoxy/graphite/403/cut up carbon (Greg's suggestion). When I first put the carbon in my first three squirts, I put carbon in before graphite/403 - not the right choice. Put in the other fillers in first. I also put in *way* too much carbon - a few cuts is plenty, and work up to the right consistency.

The other thing to keep in mind is that this stuff is hard to move around, it creates long drips that need to be squeezed into the space. Plus there's much more likelihood for voids, so it needs to be pressed in place (especially along the trailing edge). I eventually smoothed it out with my finger. Even with all that, I still had a void in the rudder.

Once that all cured, sand down, coat with a layer of epoxy/graphite (so the kevlar soaks up some epoxy), repeat. One day these things will be done.

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