Construction 06 (Final finish work and mold making)

First, the stabilator mold...

The stabilator plug in it's parting board... (The missing paint at the tip isn't a "chip" or whatever. It's the result of a little last-minute wet-sanding, just before waxing.)

Since the stabiliator will have a linkage inserted into it, Idesigned the molds to create a jig, for production. After building the parting board, I simply cut a piece out, the size of a 1/4" carbon rod, and glued it into the slot. It extends into the plug about 1/2" in the root of the stabiliator, insuring that the molded parts will be exactly the same as our plug. (The actual linkage will extend inside quite a bit further, but Ineed to slip the stabiliator off this rod later, so it was kept to the minimum length.) The whole assembly, including the rod, was then waxed and given a coat of PVA.

Next step was to add the alignment pin-producing nylon inserts, and coat the whole assembly with tooling resin. After this had tacked in for one hour, the epoxy/Cabosil mixture was added to all the sharp corners (white areas) so the cloth would conform better to the plug. This was also allowed to tack in for an hour.

Many layers of cloth later, and in a "resin-rich environment"...

When Iremoved the parting board, the plug actually fell right out of the mold... Nice.
You can see the hole left in the root of the mold, for linkage insertion during production.

The other half went just as well, and here you have the completed molds.

Next, the vertical fin/dorsal part

Here's the parting board, ready to go.

Ideally, your parting board will fit your plug perfectly, and you won't have any gaps to fill. That was the case with our stabilator assembly, but there was a small gap at the tip of this vertical fin assembly.. (above)

The traditional way to seal any gaps between your part and the parting board is to use modeling clay. Having done this many times, I see some disadvantages. Clay can be a bit messy, and also, I've had it move, when applying the tooling resin layer. This is sometimes impossible to see from the top, so you don't know if you have a problem until your part has moved in the parting board. This puts your seam off center, and it also may allow tooling resin to leak through to the other side of the mold, which can be messy, and might even lock your part to the parting board. One final thing is that Iintend to make multiple molds from these plugs, and I wouldn't want to keep recreating this hand work with the clay. So, adopting an idea I stole from my friend Darrin Cash, this is what Ido instead.

Wax and PVA the plug, but NOT the parting board. Align it as well as you can. Then, instead of clay, use a mixture of epoxy/microballoons, epoxy/Cabosil, or even tooling resin, and fill any small gaps that exist. These are the white areas at the tip, in the photo above. Let it cure.

When cured, remove the plug, and sand the filler flush with the surface of the parting board. Now, you have a precision fit, with no need for clay, it's repeatable, when making multiple molds. It will last as long as the parting board. Ithink this is a better way to go.

First half done... Getting ready for side two. Here you can see how the nylon inserts work (the yellow circles) to create alignment points around the mold.

Lots of cloth and resin...

The completed vertical fin/dorsal molds.

Test part - The NACA inlet.
This one's a little cloudy, due to some Cabosil in the epoxy. Production versions will have white primer.

The flange gets epoxied or siliconed to the inside of the fuselage. Each inlet provides about 3 square inches of intake area, for a little over 6 inches total. That provides adequate cooling are for engines up to .90 2-cycles, and/or for electric systems. To see how the mold was made, and how Iimproved it, click here.

Fuselage gets it's last coat of primer, to double-check everything. After a final wet sanding, it'll get a coat of gloss black enamel, and then will be buffed, prior to mold making.

Since I already have wings built for prototype testing, I've started on the wing plugs that I'll use for the molds. These will be prepped and finished like the rest of the plugs, but since there are no parts to cut out, it won't take as long. Production models will used skin-hinged flaps and ailerons, so no pre-cutting of these plugs is required.

After the fiberglass had cured and was sanded, a layer of epoxy/microballoons was added, to seal and toughen the surface. After this was sanded, then wet-sanded smooth, the plugs received their first coat of primer.

The fuselage hatch plugs have been given several coats of gloss black, and are being buffed, prior to mold making.

The canopy plug was given several coats of the same black, and I'll make at least one other canopy mold, to aid in production.

The fuselage in it's first coats of black. The surface is ready for molding, except for a few pinholes to fill. (The inside area of the canopy flange won't appear in the final parts, so I am not bothering with making it perfect.)

The fuselage bottom is ready. No pinholes or other problems to fix.

To see how the retracts will work, click the image for a QuickTime movie. (484k)

Click the "Construction 07" link below to continue...