The scorching heat and humidity of summer has settled in to the Mid-Atlantic region, and it’s absolutely miserable in the tent. But I’ve got lots of things to cover that have been going on for the last month or two, including some work on the V-berth head. Before we could get started on the fiberglass, fairing, and primer there, I needed to do something about dust and pain overspray control.
When we painted the boat before, my Boatamalan* painter brought a beat up fume extractor fan and filter box from work. Unfortunately, the fume extractor was tired and would trip its overheat protection after about 20 minutes of use. The hose was also tired and didn’t seal well at either end. The filter box wasn’t too bad, but they used a hinged door design for changing the filters and it leaked a lot. When spraying Awlgrip 545 and topcoat, these problems caused at least one overspray incident that had to be polished out in a small spot on the aft deck enclosure. So I bought a new 12″ fume extractor with a 20′ hose and built a filter box that I believe will keep the spray on the inside.
* Boatamalan: Noun. Joking portmanteau referring to the Central American origin of the fairing and paint crew (boat + Guatemalan). In fact, the Boatamalans are from Honduras, but Boatduras doesn’t roll off the tongue like Boatamalan does.
Using scrap 1/4″ luan plywood, I built a duct that just fits inside the rectangular porthole in the V-berth head. I used cleats to secure the top and bottom plywood panels to the upright parts. To ensure no leakage, I clamped leftover shrink wrap between the cleats and plywood before screwing it together, so the entire interior is lined with plastic sheet.
It’s not pretty, but when I hit the switch it moves a lot of air through the head.
Oh, and before putting the assembly together I also took the fan guards off and applied lots of car wax to the inside of the fan. When the sticky primer and paint spray comes through the fan, it will build up on the wax instead of directly to the fan blade and housing. This is a trick the Boatamalan taught me. Without the wax, the primer and paint spray builds up into a solid mass that can’t be removed easily. The weight of the build-up and its tendency to be out of balance is what took out the older fume extractor, and it restricts air flow through the inlet fan grill. When the inside is waxed, the build-up just pops off. Then you re-wax, reassemble, and get back to work.
I taped up the porthole to protect the new (2-year old!) paint, then secured a layer of plastic over the tape for added protection. The shrinkwrap duct liner wraps around the outside of the duct opening, creating a surprisingly good seal to the plastic that’s protecting the paint. The 12″ fume extractor moves so much air that even if there is a leak, it will be sucking air from the outside into the duct.
On the Boatamalan’s filter box, they used a sheet of flexible nylon wrapped into a cylinder to join the hose to the box. It wasn’t leak-proof at all. So I decided to use something cylindrical off-the-shelf and far cheaper than nylon sheet. The diameter of this 5-gallon was just the right size for the 12″ hose, and the ridges they put around the top of buckets will act like the ridges on a hose nipple to keep the high volume, pressurized dust and spray inside the extractor/filter system.
I built two sliding door vents in the tent wall so the end of the hose can be directed outside. One is close to the fume extractor and allows the hose to go all the way to the ground, where the filter box will be. We’ll use that one when spraying primer and paint. In the pic above, you can just see the second plywood sliding door on the lower right side of the pic. This is all the way at the other end of the hose and will be used without the paint filter box when we just want to keep air moving through the space. It’s hot in the tent during the summer! Air movement is good!
The pic above reminds me of the sequence in the movie Apollo 13, where NASA cobbled together all kinds of bits and pieces to make a jury-rigged carbon filter that saved the lives of the astronauts. Maybe I have a future at NASA as a master jury-rigger! 🙂
Seriously though, the sealing strap that came with the hose isn’t bad, but for paint fumes it doesn’t seal well enough. So I used some of the exhaust hose clamps from the twin turbocharged and intercooled Super SeaMaster gas engines that were in the boat when we found it to clamp the hose to the housing. Then I taped the end of the hose to the housing, just in case.
I also wired up a switched plug so the fume extractor can be activated from inside the V-berth. I’ll leave the switch on the unit ON, so all we have to do his hit the switch inside and get to work rather than strolling around the scaffolding to turn it on and off.
That’s a wrap for the dust and fume extractor. All in, that took a day and a half. Then I got to work on the filter box.
Built from 6mm luan plywood screwed together with solid wood cleats where the panels join, the bulk filter material presses against the chicken wire outside. For the sliding door frame, I used a dado to cut a 1/4″ (6.35mm) slot in scrap 2x4s that the plywood slides in. The plywood door inner face comes within 1/32 of the top panel, which makes a pretty good seal, but then I added a full-width handle across the top of the door panel that effectively seals it to the top panel when closed.
Unlike the little hinged door on the other filter box, this one will not leak and it’s big enough for a man to get inside if necessary to easily install new filters.
I secured the bottom of the inner chicken wire so up to three layers of bulk filter media can be used to ensure that absolutely no overspray gets past the filters. The chicken wire is attached at the top to a 1″ x 1″ wooden dowel that latches in place to secure the filter.
After cutting out most of the bottom of the bucket, I cut a matching hole in the plywood filter box then applied Sikaflex and screwed the two together. Scrap 3/4″ plywood strengthens the area and a matching piece of 3/4″ ply on the inside gives the screws plenty of meat to bite into. That hose nipple isn’t going anywhere, and it’s guaranteed leak-proof. We’re ready to make dust and fumes!