Glassing Over Bertram 31' Front Aluminum Window Frames:
02/21/05 - The Completed construction with glass and acrylic glazed
and ready for installation on the boat.
Gerry Santiago wants to have glass in the front windows & initially my thoughts were to clean up the aluminum frames, sand blast, TIG weld all of the corroded out holes, grind, sand, acid wash, alodine, powder coat, and re-install to be painted with the rest of the boat...
After considerable and deliberate thought, I've decided that the best and less expensive way to go is to completely, and heavily, glass over the entire frames, except for the slide joints, top and bottom planes. Yeah, sounds like a lot of work, and it is, but it'll come in less expensive than all of the other labor involved doing the original way. Especially by excluding a welder's fee at $75.00 per hour.
The end result will be to maintain the structural strength of the aluminum and no possibility of aluminum oxide bubbling up under the paint. The glass & Plexi will be set in from inside the cabin rather than from the outside.
Here's the general process, step by step:
1. Grind down all surfaces with a high speed offset grinder using 36 grit disks.
2. Cut out the ledge for the Plexi from the corner sections. I used the high speed offset grinder fitted with thin cut metal cut off disks. Takes about ten or twelve to do the job...
3. Acid wash with phosphoric acid solution, rinse, and alodine.
4. Allow to dry thoroughly
5. The corner windows will need to conform to the new Plexi windows & the shape of PVC needs to match as closely as possible.
First wrap and clamp a piece of laminate, (Formica, Pionite, etc.), to the outside of the corner window, nice and smooth & tight. Mark the inside opening, remove and cut the shape. This will be used to act as a fairing surface when fitted into the PVC revels. Both windows need to be templated individually. They are NOT the same!
6. Use PVC Foam Board strips to act as a core for the revel ledges. (I decided on 1/2" material stripped to 1 1/2")
7. Rough sand the faces of the PVC to remove slick factory finish and give tooth for the glass to grab.
8. Bond in the PVC with polyurethane adhesive, (Sikaflex 292 or 3M 5200).
9. Prime surfaces to be glassed first with resin. I'm using polyester, both standard MEKP catalyzed for mud fills & Ultra Violet Light cure SunRez for fiberglass work.
10. Fill all gaps with a stiff fill. I'm using standard resin mixed with Cabosil & vermiculite.
11. Three of the extrusions on the corner windows are hollow. When cutting off the seats for the Plexi, there are voids that must be filled as above.
12. My layup schedule will be 2 layers of 1208 biaxle fiberglass fabric & 2 layers of 1 1/2 oz mat on both the front and back surfaces. The back side of the PVC revels will get a single layer of 1208 bonded in after fairing to the laminate template. These strips were cut to fit from a sheet laid up on glass and fully cured before hand. The bases of the revel will be laid up with one layer of 1208 & one layer of 1 1/2 oz mat. The edges of the revel will get the same layup schedule as the front and back faces.
13. After total encasement in fiberglass, the surfaces will be sanded to near fair, faired with polyester & micro balloons and will be ready to re-installation on the boat. The whole assembly will be epoxied into place and backed up with screws both top and bottom. A totally permanent install. The joints between the corner windows and the center section will be glassed over and faired, the bottom joint will likewise be glassed over and faired. The top joint will be filleted in with thickened epoxy.
With the windows back in place, the side windows will get revels glassed in. There will be no aluminum showing from both inside and out, and all of the glass & Plexi will be set from the inside with Sikaflex, then trim moldings added around the glazing.
First gelcoat shoot... 
At this point, (02/13/05), all fabrication and fiberglassing are complete, the Plexiglass corner windows are fitted, the tempered glass front panes are ordered, and the fairing is in progress. Estimated completion, (ready for delivery to Cabrera), 02/21/05. For further discussion please contact: Patrick McCrary at 325.248.0809 |
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