Alubat OVNI 435-6 "Sakura": Refit: Gebo Hatch refurbishment

Oct 23 - Mark spent two full days stripping and renewing each hatch frame and hardware, and installing the new plexiglass. DONE Thanks Mark! We cut up a cheap poly tarp and tied the pieces securely over the "new" hatches to protect from UV damage. (I have since made fitted covers with sunbrella salvaged from an old mainsail cover).

*** the GEBO hardware requires two 6mm blind holes (for anti rotation pins) and a 14mm through hole for the handle. Note that in the photos below a corner radius template is pictured with two radii. These were advised by GEBO and reflect the corners of current production hatches, with the larger radius appropriate for larger hatches. . Unfortunately, this was not accurate as regards the hatches installed by Alubat back in 2003 when the smaller radius was used exclusively. Fortunately, the glazing could still be installed, however the sealant gap is larger in the corners of the two largest hatches than along the sides, so the result is less perfect than it might otherwise be. The plexiglass dimesions were otherwise correct and only some light sanding was required to ensure an adequate perimeter gap for the sealant. Perfect. (Almost)

Update - sept 2023

Shop-made plexiglas panels, Dow 795 sealant, and new hardware ordered direct from GEBO in the Netherlands are all now en route from Miami to curacao!

Update July 15. Sheet acrylic was purchased at plastic world in Toronto, and cut to size on the tablesaw. A template was made for the corner radii per the guidance provided by GEBO, (see note above, this was not quite right) the corners traced with a fine pencil, cut on the bandsaw, and sanded to eliminate the pencil line. The plastic scraper’s V-Notch was used to relieve the sharp edges.

This would have been very difficult to do without the shop tools.

There was sufficient material to make a spare large hatch replacement. 3 larger deck hatches, two cabin top and 4 cabin side resulted in a 35lb bundle to be shipped.

I hope the dimensions are correct…

The Gebo deck hatch glazing and some of the plastic hardware was due for replacement, and I will ship the materials required to the boat, and repair the hatches there.

The portlights used in the aft cabins see much less UV

exposure, and are fine. The oval, forward-facing hatch requires a new knob. The hardware is quite simple, is readily available and easily replaced, with accessories available, including insect screens and exterior covers.

Here is the factory literature:

https://www.gebo.com/wp-content/uploads/2019/08/Standard-Deckhatches-without-flange.pdf

Replacing the Glazing

The acrylic is specified by GEBO as 10mm for all 8 of the deck hatches supplied on the OVNI 435. This thickness is not available as such in North America, where 3/8" is the rough equivalent. According to GEBO and another OVNI owner, this will work fine. GEBO
describes the colour as "Grey tinted" and the colour code for dark grey tint that I've used previously is 2074. 3/8" acrylic, 2074 is stocked here in Toronto and I can buy a half sheet currently (June 2023) for $234. A 4X4' piece is enough to re-glaze all of the GEBO hatches.

I measured the glazing and based on this, I determined that the hatch part numbers might be the off-the-shelf items listed below. I then reached out to GEBO to see if they had dimensioned drawings available. While they were able to provide the glazing dimensions and corner radii (this to be slightly incorrect for the large hatches they supplied to alubat 21 years prior) they did not have a drawing so I must use the original glazing to determine the handle hole placement. Great response by GEBO, excellent communication. See the table below containing my measured dimensions and their dimensions.

The dimensions are consistent with current production hatches, with the exception of the largest hatches where I measured glazing 7mm larger than that specified by the factory. Fortunately, I had taken some photos that enabled some cross-checking, and I am sure this is the case. Alan at GEBO was again helpful, but had no specific reason why the dimensions varied vs the current standard product, though he did confirm the radius was the same. (Not…. Per above) Pics below show the total frame dimensions and the margin to the glazing. I measured but did not photograph the glazing itself to get the dimensions in the table above.