Skinning the Hatch

The hatch structural design calls for laminated ribs covered by a 3/8" "beadboard", topped by a layer of 1/8" birch plywood.  While the beadboard has been installed (see previous post), we have recently been determining how exactly to install the birch plywood layer.

The issue is that we have a 57+ inch wide piece of plywood bent to the contour of the hatch, layered on top of the beadboard.  We need to assure a good fit and tight bonding, since we can only provide firm attachments at the ribs, and must rely upon glue for the balance of the bond.

Shown below is our solution:  13 band clamps, anchored to the table at both ends, with the hatch itself in the original construction jig.  This arrangement prevents the hatch from spreading under pressure, and allows us to apply adequate forces to the plywood to closely bond it to the rest of the structure.

Only one of the two pieces of 1/8" birch plywood is shown.  The joint will be made in a relatively flat portion of the curve.

The straps are anchored at the bottom end of the hatch by wrapping them under a 2x6, which positions them tight to the curve, and then around an anchoring block.  At the hinge end the straps flow down over the table end and through the ratchets, which are anchored to an angle iron clamped to the bottom of the table.

The strap assembly will be slackened and held off the hatch while glue is applied.  The straps will then be repositioned and tightened to uniformly clamp the plywood to the structure.  Staples will then be nailed along each rib to hold the plywood in place.  After the glue has cured for the main (large) sheet of plywood, the process will be repeated for the smaller piece.

Since our temperatures are near freezing at night, the entire assembly will be covered and warmed by an electric heater to promote proper curing of the glue.
  

The Hatch, Realized

The hatch has been a long time in coming, but has arrived.

Our last post showed the "first fit" of the outer frame to the opening.  Next, we returned the hatch to the table jig and began fitting the inner ribs.

Fitting the inner ribs meant not only cutting them to the proper lengths with the proper end points and angles but getting them profiled to the proper thicknesses in order to maintain the correct profile for the slat application.

Once that was accomplished we began the permanent assembly of the frame and ribs.

Below the full frame, with temporary spreaders, is shown in situ.

Note that the bottom spreader is not parallel/at right angles to the balance of the structure.

With the framing fit to the actual location we added a 1/4" plywood/hardwood spreader jig to the hatch in order to retain the fit.

The theory was that this addition would lock the hatch's orientation to the opening, and it so far appears to performed as expected.

The next step was to return the hatch frame to the table jig and begin installing the "beadboard", inappropriately named since the intervening bead was omitted due to the narrow width of the part.  

Sean devised an ingenious glue pot and gun assembly that permitted dispensing a metered amount of glue into the groove of each piece.  Each slat was then placed on the hatch and air-nailed in place.  

 

Above is a view of the glue gun applying a bead of glue into the groove of a slat.  Without this tool we would have spent countless hours applying the glue and wiping the overspread from the finished product.  As it was, the application was expeditious and with minimal overspread.
 

Above is a view of the inside at the end of day one, with the plywood jig still in place.

By the end of day two the application of 117 slats was complete.  We will still need to apply a layer of 1/8" baltic birch plywood to the exterior for structure, but the inside is revealed.

The view of the inside shown above will be visible when the hatch is open.  I truly love the result, even without urethane to enhance the oak.

In the views shown, the hatch top is to the right and the bottom to the left.

The sad part is that, once the plywood is installed on the outside of the hatch, we will wind down for the season, preparing to store the trailer for the winter season and dismantle the "party tent" for fear that snow load would compromise it.  Add to that fear the fact that temperatures are getting to be too low for glue and finishes, and we have concluded that the best course of action is to put the project away for a few months.

More soon ....

Hatch First Fit

Once we had recovered our workspace from the hurricane interruption, we proceeded to fit up the hatch frame - the two outside ribs plus the top and bottom crossmembers.  Yesterday we completed the fitting and temporary assembly, then put the results in place on the trailer hatch opening.

 

Above is the right side showing how the hatch fits inside the trailer side.

 

The above view shows the bottom edge.  Note the notch at left is to receive one of the interior ribs.
 

The above view is of the hinge edge.  A 1/4" gap is maintained between the hatch and the main part of the trailer to allow for the hinge.  The square piece of plywood attached to the hatch is temporary, maintaining some rigidity while handling and fitting the frame.  The two large notches in the lefttmost crossmember will receive the interior ribs.

In all, we couldn't have been happier with the initial fitting.  Note the alignment of the reference lines in the foreground of the above photo - they are within a small fraction of an inch.  

There was, however, one slight miscalculation by your editor on the bottom edge (see middle photograph.)  The vertical placement of the two bottom edge boards is approximately 3/4" higher than intended.  This is owing to the fact that the tapered (bottom) edge of the notched board must align with the rabbeted edge of the rib; in fact, the placement was made to align with the outer profile of the rib.

The solution is simple - rip down the pair of boards by the required amount, taking it off the square (top) edge, and add the same amount to the board that mates to the back of the trailer.

The bigger issue now, though, is that we are beset by a Nor'easter which was supposed to visit rains and wind upon us, but so far as dumped probably 3" of snow instead.

Post-Sandy Post

The good news is that we all survived Sandy in relatively good condition.  Sean never lost power, but we lost it here on Monday afternoon and got it back Thursday afternoon.

We made a good decision to remove the covering from the "party tent" over the teardrop and wrap the teardrop with a tarp.  Meanwhile, the tent is back up and the tarp removed.

It will take some time getting back into the swing of things.  Today we spent the day repairing a section of my home that had its covering blown away, and rebuilding a gutter that was blown off.  There is a small amount of work remaining tomorrow to rehang the gutter.

Meanwhile, I did manage to capture this image this morning on the Branford River in Branford, CT, USA:

This adult bald eagle has been around for some time, and today a juvenile bald eagle was also in the neighborhood.  This must be the parent, as they were sitting on the same limb at one point.

Not too long ago it was a rarity to have a nesting pair of ospreys on the various nests in the area.  Today, the plentiful ospreys have rebounded quite well, and now are competing with a superior predator for territory.