David Merriman's Flying Sub project part 6 page 1

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David Merriman's Flying Sub project

part 6 page 1


	Before laying down the first coat of primer over the upper and lower hull halves, all surfaces were given a thorough scrubbing with #240 sandpaper used wet. The sandpaper was backed with a three-quarter-inch thick foam block. The foam block distorts enough to permit the sandpaper to negotiate compound curves, inside and outside fillet radius' without scaring those areas. All sanding sludge was wiped off with a damp cloth and the model left to thoroughly dry. I use the Dupont Lucite brand automotive acrylic primer, Fill 'n Sand 131S. This gray, air-dry primer has high fill and is quick drying. It can be cut with the recommended thinner to either a mud or water thin consistency. This primer must be applied with the recommended Dupont thinner. Oh … you wonder where Mr. Surfacer comes from? This is it, uncut Fill 'n Sand (or its equivalent)!

		Using an old plastic pallet I'm mixing up small amounts of Evercoat filler (polyester glazing putty) to touch up spots on the hull halves revealed by the primer to have either file/sanding scratches or depressions indigenous to the kit (Damn you, Rick Teskey!). The neutral gray color, seen by an angled light source, will reveal such surface flaws as shadows. Scratches less than a thirty-second-of-an-inch deep are best filled with the air-dry Nitro-Stan lacquer based putty. Deeper faults are best filled with the exothermic curing Evercoat filler.

WORK BEGINS!

Hemispherical Hull Dome Holes Though fabrication of the hemispherical hull dome master would come later, now was the time, with the two hull halves still easily worked as two separate pieces, to punch out the big holes in each and to dress both their circumferences and inside surfaces to accept the cast resin parts at a later stage of construction.

Using a small drill bit I cut out an array of holes about a sixteenth-of-an-inch within the scribed circle inlayed on each hull half. I could have use a jigsaw here, but I was worried that the severe vibration from the tool would knock gel-coat loose from the fiberglass substrate. My experience with the DeBoer Hull SEAVIEW gel-coat failures has made me weary of trusting the lay-up work of others. But, as it turned out, Rick's glass guy (I assume Rick farms out his lay-up work) did it right and at no time during this project did I experience any significant gel-coat failure.

Anyway … once the circular array of holes was cut and the ragged central disc punched out from each hull half, I went in with a Moto-tool disc sander and cleaned up the holes, finishing the job with a special sanding block (cut to a radius just a tad less than the holes) to who's face was glued #100 sandpaper. #240 was substituted for the #100 and the circumference of the holes given a smooth finish.


	Note that large semi-circle block with a portion of sandpaper glued to its perimeter – this was used to true up the rough circles cut into the top and bottom of the hull. Most of the FS-1 hull is a compound curve. The majority of the sanding was done with the soft foam block you see to the left – small enough and flexible enough to distort and conform to the shape of the hull. Most sanding strokes are of a small circle or figure-of-eight form, applied with light pressure. The pre priming sanding performed on the kits raw gel-coat was with #240 grit, this preparatory sanding abrades off any mold release on the hull remaining after the initial water and soap scrubbing with '0000' steel wool. Also, the sanding scratches the surface sufficiently to produce the 'tooth' needed to assure good mechanical attachment of the primer to the models surface, be that surface (soon to be substrate) it polyester gel-coat or cast polyurethane resin.

Later, within the hull, would mount the gusset foundations of the two hemispherical dome casting. But first I had to come up with a sure-fire means of machining those bonding areas, a means of achieving a flat surface within the hull halves, adjacent to each hole.

The glass lay-up process on the hull halves produced an uneven interior surface. However, the array of gussets that held the hemispherical dome a fixed distance from the open hole had to seat on an even plane. My solution was to mount my Moto-Tool in a fixture that held its rotating high-speed cutting bit (for this job I selected a carbide burr wheel), a specific height off the worktable.

The hull was firmly held down so that the flat face of the hulls exterior (defined by the hole) sat flat on the table. I set the height of the cutting wheel to give me a wall thickness, at the machined seating surface, of three-thirty-second-of-an-inch. Careful use of the mounted Moto-Tool (working much like a free-hand router) insured a quick and true machining of the two hulls interior surfaces adjacent the big holes. Nothing to it!


	Because the inside surface of the two hull halves was of rough texture and uneven of thickness I had to come up with a means of producing a level, uniform surface upon which would be bonded the many gussets of a hemispherical dome piece. Here I've mounted a Moto-Tool onto a holding fixture that will assure that the cutting burr remains at a fixed height over the workbench. Also, the distance the tool can cut inboard of the opening is dictated by the base of the holding fixture as it makes contact with the holes edge, assuring a uniform, concentric flat plane cut into the inside of an FS-1 hull half.

FIXING THE BOW AND STERN BULKHEADS AND OTHER CHORES Before I could start with the layout of the detail masters that fit to the bow and stern bulkheads those surfaces needed fixing. The bulkheads had to be restored to flat planes. Unfortunately, Rick denoted position and shape of the fittings that attach to these bulkheads as positive and negative relief shapes. His work there was both unsymmetrical and of poor form: the circular searchlight guard rings were oblong, the trapezoidal window wells were of uneven depth and off centerline, and the transitional radius between bulkhead and lower lip of the hull was uneven. At the stern, the depressed locator for the door was misshapen and off center, and its bordering fillet (lower and sides) was uneven.

An otherwise fine hull kit, Rick's FS-1 suffers from an apparent last minute rush to provide these locators which are intended to show the end-user where to put the detail fittings (fittings the end-user either makes for himself or acquires from me (hint, hint … wink, wink!). Rick would have served his customers better had he not bothered with the locators and just left the forward and after vertical bulkheads simple flats.

So, I filled and ground off the landmarks from my copy of the kit. Only after that was done could I loft the correct locations for the detail items from my plans and photos, to the two bulkheads; once things were laid out onto the model in pen I could then set about making the masters of the fittings kit, checking each in position as work progressed.

First, with a Moto-Tool equipped with a big ball carbide burr, I ground down the two raised searchlight guard rings. Before mixing up some Evercoat and filling the intake, window, and door depressions I gave the entire surface, including all faces of the wells, a good rubbing with #100 sandpaper – this insuring tooth to the surfaces which in turn would assure excellent bonding of the filler.

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