With the prep work quickly progressing toward the day when we apply shiny Awl Craft 2000, I started cutting templates for the windows. I’d settled on a window manufacturer in Washington State that uses powder coated aluminum frames. This manufacturer’s design uses a clamp ring on the inside of the boat, with very precisely cut screws that thread into the back-side of the outside window frame. Since there are no screw holes on the outside, which are a common source of leaks, the clamp ring design is far better than most other window designs.
The one hitch with the aluminum-framed windows is that the tolerances are pretty tight: ± 1/16″. For all intents and purposes, there is no way to install these frames onto a structure that isn’t close to perfectly flat. Last week, I discovered that the welder who built my aft enclosure put twist into three of the six panels that have window openings, which induced an arc in the panels along the width of the window openings. The smallest arc had 1/8″ of deflection and the worst had 1/2″ , but all three were more than the 1/16″ tolerance the aluminum window frames could accommodate. This is in addition to the one panel he welded in the wrong place that was so bad I had to cut it off and relocate it a few months ago. Highly paid, incompetent “craftsmen” have been the bane of this refit since Day One…
After determining the aluminum framed windows wouldn’t work, I considered Eisinglass but decided against it for a couple of reasons. The first was that the enclosure was obviously designed with windows in mind, so it would look cobbled together to use Eisinglass. Also, since the whole structure is bonded and faired to the hard top, the last thing I wanted to do was start cutting bits and pieces off or doing other major modifications to already completed work.
Next I looked into fiberglass window frames, but the quote came back at $1300 each (vs roughly $350 each for aluminum) and I need six of them! The fiberglass window manufacturer did say, though, that his windows using tempered safety glass can be formed to an arc. So that got me thinking about a DIY solution that might be just as good and save a bit of money.
The FRP I-beams measure 2″ x 4″ and are very lightweight and rigid. Step one was to cut the 20′ I-beam into pieces just a bit longer than the window opening dimensions.
The radiused inside corners would not allow the T-beam frames to sit tight to the aluminum aft enclosure window openings, which have tight 90* corners. With a little milling, I knocked the radiused corners off.
With the pultrusions cut into usable T-beams, the next step was to dry fit, mark and cut each piece to make up the horizontal and vertical window frame pieces.
The shot above shows the solution to the worst arc the SMIB* welder put in the aft enclosure panel. The T-beam is tight to the window opening from the front edge to about halfway back, after which the window frame and panel curve in. You can see a 1/2″ gap at the lower right corner of the window opening. The arc begins to the left where the first kerf cut is. The kerf cuts allow the outside FRP panel to match the arc of the aluminum panel while still retaining the two-surface bonding area afforded by the T-channel shape. Tempered safety glass can easily be warped to fit and urethane will hold it all together.
*pejorative slang abbreviation for Southern Maryland InBred.
I used US Composites thin epoxy resin thickened with West System 404 adhesive filler to bond the T-channel frames to the window openings. Wooden scraps helped spread the clamping force over wide areas. Covering the wood with shrink tape first helps ensure that the clamp spreaders will release from the epoxy after it kicks.
I removed the clamps and blocks once the epoxy started to take a set, then quickly applied a small fillet around the exterior perimeter of the frame. The fillets are made of the same home-brew fairing compound we used on the cabin top and elsewhere on the boat. It’s based on the same US Composites epoxy resin and hardener as the adhesive, so the fillets make a perfect chemical bond to the adhesive epoxy that squeezed out of the clamped joint. Instead of West 404 adhesive filler, which is brutal to sand, I use a 2:1 ratio of 3M microballoons and Cabosil in the fairing compound to make for relatively easy sanding. The fillets make for a cleaner, more integrated install, just like they did on the cabin top to deck joint and at the helm station dash pod. Fillets also eliminate the seams where dirt can collect.
Unfortunately, this most recent detour from “the plan” took almost an entire week to identify, brainstorm and resolve, and everything else was on hold until I worked it out. I’ve only got so much vacation time I can take in a given year, and I blew five days of it fixing this latest SMIB-inspired problem. Another down-side is that we wanted slider windows for better ventilation but they’re impossible in twisted frames. On the upside, the total out-of-pocket cost for aft enclosure windows just dropped by a significant margin since my labor is free (of course).
Ah well, it’s a boat…they’re all about the compromises, I guess. It sure would be nice, though, to have competent craftsmen whose work is commensurate with the $$$ they charge. So far, the only workers who consistently perform to a high standard are the boatamalan fairing and paint crew. Speaking of which…