37.) Cosette on Shop IR

My small dog who thinks she is a big dog got in a fight with another dog who thinks she is a big dog because she is, in fact, a big dog.  Cosette was the uncontest loser of the scrap and actually lucky to be spared her neck.  Cosette was bruised, both physically and emotionally.  She's been spending extra time at home in recovery time.  I am sure the absence of Cosette's steadying influence on me is what sabotaged the first vacuum bag.  She is a vital member of the team.

36.) Everything is Different, the Second Time Around

Now that's what a proper vacuum bag is supposed to look like. Hooray!

I bravely (or stupidly) attached six planks again this time. But to help slow things down and allow me to be more careful I used West System's extra slow epoxy hardener instead of just the normal slow hardener. The extra slow stuff is made for boatyards in tropical climates, but lately that's just the sort of weather we've been having in New York. It provides a substantially longer "pot life" (when the epoxy is thick in the mixing cup) and takes 24 hours to cure at a constant 72 degrees.

The most important thing I did better this time, basic as it is, was to keep my plank marking system simple so I didn't accidentally apply any epoxy on the wrong side of the planks like last time.  

I also was much more careful with all the materials and about establishing a good seal around the area to be vacuum-bagged. The photos below show the tape and the way it goes on (the fourth side is hidden on the outside of the boat). I still had a few tiny leaks (which is all it takes to mess up a vacuum), but they were fairly easy to plug.

The super slow epoxy also gave ample time to line up the planks properly and staple them down. I still found it impossible to get them absolutely perfect, with no gap at all, but I came pretty close. I am guessing I will have figured out how to do it just right by the time I install the last plank (which of course will tempt me to pull them all out and start all over again—an urge I hope to vigorously resist). Stapling was all that was used to hold the planks together for gluing when the boat was first built.

I am not going to show all of the steps involved with shaping and vacuum bagging in this post because I have to repeat the process four to six more times (depending on how brave I get) to finish the hull. That will give me more opportunity to explain this process in greater detail. I also wanted to focus on avoiding a repeat vacuum bag disaster, so I also left the iPhone on the sidelines for this go around.

The vacuum pump is still running in the shop as I write this. It will need to stay on for at least 24 hours to maintain the seal that is clamping the new planks to the hull. That's much longer than it would usually take using a faster hardener. The risk is that if a leak develops during that time, the vacuum could lose some or all of its pressure and ruin the job.

One thing I am going to do differently in the future is to get a proper suction valve to attach the vacuum hose to the bag. The way I am doing it (with multiple holes cut in the end of the hose that's inside the bag) works okay, but it's hard to get a perfect seal around the place where the hose enters the bag.

35.) How Not to Vacuum Bag

This is not the way a vacuum bagging project is supposed to look. The sandbags are the giveaway; they are a resource to turn to when trying to stave off disaster.

I began this phase of the project excited to finally have begun the process of rebuilding the boat. My shop mates quickly noticed I was up to something unusual, so I also had a curious audience.

Making a vacuum bag is the best method for installing planks on the inside of the boat. Done right, the bag provides a clamping force that distributes pressure evenly. I thought I was being conservative by confining this step to six planks. A professional would try to do the whole hull, or at least half of it, in one shot. As it turned out, though, I should have been even more cautious.

I outlined where each plank would go and I numbered and marked each one. Then I mixed a batch of epoxy and used a two-inch paint roller to spread it first on the hull and then on the underside of the planks. I mixed a second batch of epoxy thickened with a filler and spread that on the hull with a finely notched plastic trowel. (The unthickened first coat seeps into the wood; the thickened mixture provides a paste between the boards and the hull, helping to fill out any hollows and to avoid voids in the laminate.)

Mixing epoxy is a bit like firing a starting pistol. The moment you blend the resin and the hardener, a chemical reaction begins that eventually turns the liquid into a hard-as-steel solid. Heat accelerates the chemical reaction. My shop thermometer showed it was 87 degrees, so I used West System's slow hardener to give myself more time. I figured I had at least an hour, maybe 90 minutes, if I got the mixture out of the pot quickly and spread out on the wood (the curing reaction slows when the epoxy molecules are distributed at greater distances from each other).

I like to think of myself as cool under fire, but for some reason, epoxy always stresses me out more than it should. Feeling under the gun, I sometimes work too frantically. And that's how I made my first mistake.

Midway through applying epoxy to the planks, I misread the markings I had written on the boards and coated the wrong side of three planks. That meant that I had to go back, turn them over, and coat the other side, too. Now I had three super slippery planks that would be difficult to wrestle in place and staple down.

Once that was done (after going through three pairs of disposable gloves), I placed a layer of release fabric (a material that doesn't stick to epoxy) over the planks. Next came a layer of a breather cloth that would enable air to flow within the bag. Last was a thick plastic sheet that would serve as the vacuum bag. I had cut all of these materials to size beforehand. I also had already surrounded three sides of the planking area with a clay-like adhesive. The adhesive is what holds the plastic bag on top of the breather cloth, release fabric, and planks. It creates a seal when air is removed from the bag. In the best of worlds, the resulting vacuum gives you the equivalent of one atmosphere of pressure (more than 2,000 pounds per square foot) spread evenly over the bag,

I initially put down only three sides of the adhesive because the fourth side had to run on top of the planks themselves after they were in place. As soon as I started putting the fourth strip down, I recognized the makings of disaster. The clay refused to stick properly to the three planks with epoxy on the wrong side. I quickly wiped as much off as I could and did my best to try to get the adhesive to adhere.

The last step in vacuum bagging is to run a perforated hose under the plastic bag, attach it to a pump, and start removing air from inside the bag. The bag needs to be leak-free to remove all of the air. When I flipped the switch on the pump, I could hear hissing. A lot of hisssssssssssssssssing, in fact. I had a typhoon of leaks. Most were in the area where the fresh epoxy was keeping the adhesive clay from sticking properly. It's not unusual to have a few leaks at first, but this was way worse than usual.

I spent the next 20 or so minutes frantically trying to plug the holes, using more clay, tape, and plastic. But it was a losing battle. When I only had about 10 minutes left before the epoxy started to "go off" or harden, I got desperate and started running around the shop looking for a solution. At the last minute, I found four 50-pound sandbags and set them down in the area where I was getting the most leaks.  At the very least, I surmised, the sandbags would apply uniform pressure on the wood the same way the vacuum bag was supposed to, though at about a tenth of the force.

But .... I also got lucky: the sandbags greatly reduced the amount of leaking. A decent, but not great, vacuum developed inside the bag. As an added measure, I fastened wood clamps on the top of each plank.

Then I collapsed on my shop stool, exhausted, drenched in sweat, and disappointed. And that's when the ribbing started.

"What do you got going on there, Mr. Boatbuilder?", one of my fellow woodworkers asked as he passed by.

"Preparing for a flood?" remarked another.

"Oh, so that's what a vacuum bag isn't supposed to look like", said a third.

Ha. Ha. Joke's on me.

In coming posts I hope to be able to show that I regained my composure, learned from my mistakes, and executed a much better vacuum-bagging operation.

Below is a photo I took the next morning after I removed the bags and adhesive, sanded the epoxy off the top of the three planks, and did a little filling between the seams. They still need a fairly aggressive hand sanding.  But, in the end, the sandbags did their job. It wasn't a complete disaster.

Note: the red Bessey clamps are holding the hull in the mold. The new planks should help the boat regain some of its designed shape.

34.) A Free Lunch!

Do you love sanding?

No?  Are you sure?  Want to think it over at little more carefully before you reply?

Okay. Alright. I don't love it either. But it is and probably always will be a critical part of boat work. So that's why this humble boat restorer decided to invest four hours of his day today attending a free seminar focused exclusively on the topic of sanding. It was sponsored by Stiles, a Michigan-based machinery company, hosted by a cabinet shop in Greenpoint, and attended by a representative from 3M.

Overall, the session was kind of disappointing. I learned much more about sanding technique several years ago by spending half an hour with Carl at McMichael's Yacht Yard in Mamaroneck. Carl is a real treasure. He transforms sanding into something approaching an art form. He doesn't use machines or sanding blocks, but instead folds a piece of sandpaper carefully in his palm and goes to work, letting his trained hands feel the highs and lows he needs to even out with the paper. He also feels the resistance of the paper as it scratches the surface, information that tells him how close he is to being able to move to a higher grade. He focuses on one small area at a time and doesn't move on to the next until he has the object of his current focus finished. He does amazing work that I can't duplicate in either speed or quality no matter how hard I try. His level of patience and discipline are superhero qualities to me. I'm patient, too, but if sanding were a sport I'd be on the junior farm team and Carl would be on the starting lineup on a pro team. 

I did learn something at the event that I had never heard before that I think is worth passing on. It's this: As soon as it is freshly sanded, wood that's newly exposed to air begins to oxidize. Within 24 to 48 hours, it's composition is affected and starts to change. This matters because it affects the ability of a finish to penetrate the wood fibers, impacting the appearance of a finish (especially a stain, varnish, sealer—or anything transparent) as well as the adhesion of the coating.

The bottom line: don't let 24 hours elapse between the time you finish sanding something (whether it's a mahogany tiller or a hardwood floor) and the first coat of finish. The 3M guy said that cabinet makers who complain about the results they get in the finishing room often end up revealing that they typically complete construction on Friday and begin the finishing process on Monday. Big mistake.

If in doubt, MMM suggest you try the drip test. Put droplets of water on your sanded wood and see if the droplets disperse and penetrate the wood or if they tend to sit intact on the surface. If the latter happens, the oxidation has become a problem and will lead to things like stain blotches on a beautiful piece of hard maple.

A piece of sandpaper rated 36 is not exactly interchangeable with one rated P36.

Another thing I suspected but didn't know for sure is that a regular 220 grit sandpaper is different from P220 paper. The ratings with the P follow the European numbering system, which has been gaining in popularity. They are not radically different, but they are different. (I don't know if that's because Europeans measure the grain count metrically rather than Imperially. I do know that the ratings for U.S.-made sandpaper relates to the number of tiny pieces of crushed rock glued to the paper per square inch. A 220 paper has 380 fewer pieces of rock on it per square inch than a 600 paper.)  There's also some new measurement system I didn't pay much attention to in which the finest paper is rated 1 and everything courser has a correspondingly higher number.   If you want to see how this confusion plays out, click on this link: http://www.mibnet.se/home-improvement/sandpaper-grit-size-comparison-between-european-and-us-standards.html  It might help you get your ps straight, if not your qs.

The final thing I learned is that 3M has developed a new sandpaper that is somewhat revolutionary (in the sanding world at least). It contains a new abrasive made of a ceramic mineral that has two advantages: first, unlike the particles on regular sandpaper, the abrasive is identically sized and shaped; second, the tiny bits of stuff that scratch gradually break down in a controlled manner forming sharp new peaks that keeps the sandpaper working.

From 3M literature: "The secret lies in the revolutionary precision-shaped ceramic grain technology pioneered by 3M. As the triangular shaped grain 

wears, it continuously fractures to form sharp points and edges that 

slice through metal, wear evenly and provide super-long life and 

consistency at any grinding pressure."

The new sandpaper is made of a ceramic mineral and the new brand is something 3M is calling "Cubritron II."  (I have no idea what happened to the first Cubitron).

"This is already a game changer in the metalworking world," the 3M guy declared—and I think that's probably at least mostly true, mind-blowing as it may be. At the moment, the new paper is available only in very rough grits for wood: 36, 60 and 80. But I plan to try to get my hands on some, try it out, and report on the results. There were no free samples at the sanding seminar (I am still shaking my head that I voluntarily went to such an event). But I did get a free roast beef sandwich.

One reason I didn't learn more at the session was that it covered a lot of stuff I already know.  If you have questions about sandpaper, drop me a line and I'll be happy to help.

33.) Multi-tasking

I've got a lot of things going on at once at the moment and this photo shows most of them. On the port side of the boat (right side of the photo), I'm still applying and sanding epoxy fairing compound to prepare for planking. You can tell it hasn't been sanded yet because it turns from dark red-brown to white with sanding. (The color change has the added advantage of helping you to see low spots that aren't scraped by the sandpaper.*) On the starboard side, the fairing is finished and I'm starting to shape mahogany planks to fit into the hull.

The planks don't go in straight, but curve along their sides. That means each has to be individually shaped by hand on one side to fit snugly against its neighbor.

The planks go in at an angle to the layer of planks below. This makes the boat stronger by aligning the grain of the wood in a crisscross pattern.** It also means the planks don't need to bend as much to fit the shape of the hull. That's not a huge deal except for near the bow, where the planks need to bend in multiple directions.

The first plank can have straight edges on two sides. I made the other two using different techniques as an experiment. For one, I used a compass to scribe a line along the edge of the plank and then cut and sanded it to fit. For the other, I used a small brass violin maker's plane (barely visible in the photo) and did most of the work by eye, taking shavings here and there until I got a good fit.

Both methods took about the same amount of time, but I had more fun using the plane. It's good to know both ways of doing it work well because some of the shapes may be more difficult when I get closer to the bow.  I have one more method I may try out on the next plank.

You probably noticed all the popsicle sticks stuck to the planks. I could say that it was a really hot day and I ate a lot of popsicles to stay cool.  But actually they're tongue depressors and I am using them with a pin gun (an air-driven tool that shoots super-skinny headless nails) to temporarily hold the planks down as I shape each one. I'll need to take the planks off again before I can epoxy them in place. My as yet untested theory is that I will be able to break off the tongue depressors and easily remove the pins with a pair of pliers. (This is another technique I made up on my own, but doubt I am the first to think of it.)

Bostitch Pin Nailer

I can't finish the job of patching the big hole in the mast step area until I install the planks. That's because the patch needs to go in on top of the new layer of planking.

The patch is almost complete. Below are a couple of photos of what it looks like. The first shows it from above with it temporarily in position. The second shows the underside of one end of the patch. Note how it is both layered and stepped. The dark lines are epoxy between each layer.  I watched those lines carefully as I sanded the bottom of the patch into a triangular shape, trying to keep them relatively straight fore and aft. The final sanding to fit should remove those lines almost completely.

The patch is also curved fore and aft to match the shape of the hull. To get that arc, I cut out a piece of plywood in the shape of the boat's bottom (working off the original plans) and then laminated the patch together with epoxy and clamped it to the plywood mold. Here's a photo of what that looked like (and also happens to be a good illustration of why woodworkers often say that there is no such thing as having too many clamps):

Finally, when I cut out the piece of plywood for the laminating mold, the matching curve in the leftover piece was perfect for making center supports for the frame that the boat sits in. If you look again at the picture at the top of this post, you can see them peeking through the big hole. They are covered in plastic so they won't stick to the hull when I epoxy everything together.

*Even though you can see one of my Festool sanders in the photo, I did 95% of the fairing on the inside of the boat by hand with 60 grit sandpaper backed with a piece of wood. It's too easy (for me at least) to add new highs and lows into a fairing job with a power sander.

**This crisscross pattern was especially important in the past when the planks were glued together and varnished. The orientation helped keep the wood from expanding and contracting as it gained and lost moisture. Because wood doesn't move much along the direction of the grain, each plank would help hold the boards above and below it in place. This is less of an issue now with epoxy, which prevents moisture from getting into the wood at all. This is a topic I'll be coming back to in more detail and will discuss why epoxy can, under certain circumstances, make the problem worse.