The Cockpit Gets a Coaming

Standoff for coaming

Cockpits need coamings.

What is a coaming? Simply stated a coaming is a vertical surface whose purpose is to prevent or help prevent the egress of water.  Hatches have coamings and so do cockpits.We had this idea that what would look really cool and would be really practical at night is to use LED rope lighting along the underside edge of coaming to provide a glowing courtesy light on the cockpit floor.  So, to do this we started with a 5/8" x 1-3/4" strip of yellow pine that is epoxied in place around the deck edge.  You can see it in the first photo posted. The mahogany coaming itself will overhang this by 1-1/4".  This creates a 5/8" x 1-1/4" slot under the coaming for the LED rope light.  We'll wire it through the pilothouse wall to a rocker switch.
We choose mahogany to add a little elegance to this social area.  The stock was planed to 5/8" to help take the slight curve of the cockpit.  It flexed just fine and was carefully measured for length and using a bevel gauge, we angled the side to rear joint which was 99 degrees. Basically just had to set the saw to 9 degrees and cut carefully.  Make it slightly long and creep up on it.  Once in place, the long sweep from 6" to 3" was sprung from a batten and cut with the circular saw.  The corresponding bottom cut was marked using a compass setting of 3" held along a pencil line marked along the deck's edge.
Again, we buttered it up with epoxy glue mix and used countersunk screws to be bunged over before coating the entire coaming in epoxy.

Notice the shadow on the coaming as it stands proud of the cockpit walls. At night, soft light will flood down from that groove.

The rear coaming board was installed in much the same manner.  Cut to length, 9 degree bevel. Sneak up on the final cut.  Glue and screw.  I also glued the vertical joint and put one screw at the top to pull it tight.  It will disappear when bunged and sanded final.

Now the cap and back to the wood shop to make it...

cutting the miter with a Shark saw
and using a wood block guide to
keep the blade vertical

The miter joint photo shows the cap.  It is almost too heavy to slip over the walls and bend to the curve of the walls, as well as, make the curve horizontally.  I'll go ahead and explain the dimensions.  It was milled 3/4" thick by 1-3/4" wide.  A groove was dado-ed 11/16" wide for a little slop for the epoxy to hide and all edges rounded over with a 1/4" round-over bit.
I will advise that two steps are taken before "horsing" it into place for fitting and please fit all pieces before gluing.  One, slightly round over or bevel the top edges of the coaming walls to help slip the cap over; and two, put a C-clamp across the edge of the coaming.  You can see in the photos of the glue up what I am talking about.  It is really easy to snap off the wood adjacent to the dado as it is twisted sideways.

Fitting the starboard cap, note the C Clamp insurance.

The first miter is determined by marking the inner corner and outer corner of the vertical coaming on the underside of the cap.  One could also use a bevel gauge to mark this.  Either method gets the intersection of this odd angle marked.

The back cap is placed over the top cap and marked and cut.

With everything fitted final, we mixed a bag of glue, loaded the Wilton cake decorator bag and laid a generous bead in the groove as the clamping, pushing, coaxing and cussing finally persuaded the caps into place.  Lots of clean up on the squeeze out and wipe down with denatured alcohol.

Wrapping in Dacron...

Gonna try this method and see how it goes...

Screw holes filled and sanded.  Ready for cloth.

Progress has slowed a little.  We have had a Frozen birthday party for Miss Addy's namesake and farm themed one for her sister a month later here at the house. Along with that went the prerequisite cleaning, painting and general work to make the place presentable.  In the interim my father's kitchen was remodeled by all of us splitting duties and we consumed time tiling, painting and such.  This is not to mention the mandatory tractor rides that we try to squeeze in daily for my grand baby and by the time I make it home from a twelve hour round trip day, there is not much left of it for building.  It's all good stuff and when my daughter and girls head back up to Ohio in December to be with their husband and Daddy (who is stationed there in the CG), we are going to miss them bad and this house will be a little too quiet...

On to the build...

As of this posting date, we have moved a lot quicker and hope to spray the exterior paint before cold weather sets in and we're fighting cold spots in the shop.  Actually the timing may be perfect for the water based LPU as it hates hot and dry, prefers cold and wet for flow out.

Pilot house wrapped and stapled around inside edges of openings.

The procedure is pretty easy, especially with the Xynole cloth.  The "Try this method" part of the title referenced the use of staples to stretch and hang the cloth. The procedure is to stretch it out with as few seams as possible in the layout of the cloth, staple with stainless or Monel staples to hold in place and pour copious amounts of epoxy resin as this cloth drinks it.  The cloth actually swells around the staples so it makes it easy to fill the weave and staples. I chose to wrap the inside of window openings for added protection to the plywood edges.
I am unconcerned with the seams or joints between plywood panels. They will be faired with a filler mix and once all of the "flats" are finished, we will fillet the junctions or joints where structures tie together at ninety degree angles.  I have to remind myself that the Xynole is a "covering".  It provides little structural (tensile) strength as wood glass but it is much more flexible in the event of an impact.  Primarily it is there to provide an enhanced waterproof layer of protection and to prevent the surface checking that is common in Marine Fir plywood as it ages.

Wet out cloth cloth with protective paper to limit mess.

One trick that worked well to help with the wet out was to actually jack up one side of the boat so that there is a slight angle to what would have been a plumb, vertical surface and the epoxy resin can be poured down the side and moved around with a plastic squeegee.  Remember to take your time and let the resin do its thing.  Once it has, squeegee with increasing pressure to bond the cloth firmly to the plywood.  One step that isn't necessary with the Xynole as opposed to fiberglass is to squeegee and wipe excess resin from the cloth's surface to prevent pooling and potential floating of the cloth.  The Xynole just simply continues to drink it in and when we make our final hard squeegee pass, the cloth is tight and dry but not starved (white patches).

The pilot house is wet out after a round of filling and sanding.  Note the little pneumatic
T-50 stapler sitting in the engine well... $30 Freeman ordered from Home Depot, works great.
White decks are un-wetted Xynole stretched and stapled.

Next to cover were the decks which are to be left un-glazed for a non-skid surface. These weren't done first because we were trying to limit any epoxy pooling that would fill the weave and mess up the texture from the vertical walls. Glazing is a term I first read in Ruel parker's Sharpie book and it  simply means spreading a thickened layer of filler on the very open Xynole weave to fill and smooth it in one fell swoop.  The decks will all get a glazed border and fillet where needed.  This should create an appealing smooth grid with non skid panel fills.

Half of deck wet out.  Xynole overlaps all edges.

Half of front deck wet out.  Deck was one continuous piece split down the middle on the
front deck and rear deck to limit junctions.

Engine well panels stapled in place and ready for wet out.

The glazing was done using plastic and spring steel squeegees or body filler spreaders.  I have also used steel drywall trowels.  The trick is to put a good deal of pressure and work it back as thin as possible.  The joints will be rough but a belt sander will take this down.  Two rounds of this will be necessary to completely fill the weave.

Engine well glazed. Pilot house wall is partially glazed. 

Rough joint filled on first pass.

One other part of this application process that needs mentioning concerns sanding.  On what you see of this process so far, we did not sand the wetted cloth before glazing.  My fear was that I would be cutting into the cloth.  On the cockpit liner (ceiling) I did sand the cloth to eliminate the extremely rough nibs and fibers. I have to say it made for less final sanding and less glazing filler on application.  It was noticeably smoother to fill and was easier to get a thin weave filling only coat.  Careful though, it is really easy to sand into the weave... a careful balance.  The jury is still out on which method is best.
One other thing to keep in mind is the use of Fumed Silica in the mix.  I used a U S Composite's fairing filler mix that is an obvious mixture of phenolic microballoons and silica.  The problem with FS is that it can be hell to sand.  It gets rock hard, BUT, it is essential if you are going to keep the glaze vertical and not drooping.  I had to add a little more FS to the USC fairing mixture to use its thixotropic properties to keep it in place where corners or edges had to be built up. A good rule of thumb for the filler to start with is 2 parts microballoons and one part silica start.  The resin to filler ratio is two to 1 filler to resin by volume.  If I mix a 12oz batch of resin, I will mix this into a bucket of filler containing 24 oz by volume of the filler mix.  It is a starting point and will seem too dry to start but keep mixing and you may have to add more fumed silica to get it to that peanut butter consistency you want, and, by the way, that's good old fashioned Jiff consistency, not these runny organic versions that you pour on a sandwich instead of spread.

Well, we cannot move any further along until I do a little more construction.  The cockpit coaming is next and then we finish the joints as we push toward paint.