Building the Cowl for the L-4, J-Kota Biplane, & Flybaby Biplane --
the Complete Step-by-Step Building Instructions
The Cowl assembly for the 1:8 Scale L-4 is also used on the J-Kota Biplane and the soon to be released Flybaby Biplane, so I thought it might be a good time to offer the assembly instructions here. The photos and captions below will walk you through the step-by-step process of trimming, assembling and detailing the cowl and dummy Continental A-65 engine.
Note: Medium Cya will work fine with Styrene Plastic, but don't use Thin Cya as it will crystallize the plastic and it will become extremely brittle and it'll be very easy to break it.
I prefer using Liquid Weld Cement for plastics as it gives a better joint, and won't leave the plastic brittle like Cya. There are several brands available that will work well. Check the plastic model section of your hobby shop and use what they have available.
The Cowl Kit comes on 3 Vac-Formed sheets, and includes the Cowl, dummy Continental A-65 engine cylinders, cylinder mount cavities, valve covers, and cooling baffles (eyebrows).
Begin by cutting the Cowl from the backing sheet 1/16" above the excess plastic. Then open up the indented areas on both sides to accept the cylinder assemblies. Then the prop opening and oil cooler slot can be trimmed open. You can open up the carburetor air box inlet too, but that's up to you.
The dummy cylinder mount cavities are cut out next. Note that they are marked L and R. Align them with the cutouts, on the inside of the cowl, and glue them in place.
Trim the Upper and Lower Cylinder halves from the carrier sheet leaving 1/8" or so of excess material around the perimeter. Then glue the halves together. When the glue has dried, cut the bottom off as shown and fill the concave seams on the inside with either 5 minute epoxy or medium Cya and allow to dry thoroughly.
Once the glue has dried thoroughly, trim and sand the excess plastic from around the cylinders. Fill any remaining gaps with glue and sand.
Cut the Valve Covers and Eyebrows from the carrier sheet and sand the edges nice and smooth. Leave a 3/32" or so wide lip at the top of the eyebrows as shown. Also leave a fair amount of material at the bottom so that the fit can be trimmed in nicely to the cylinders once they're installed into their mount cavities.
Once the Cylinder Assemblies are trimmed and sanded, fit them into the cowl. You might need to trim the openings a bit to slip them in, but work slowly so you get a nice snug fit. Align the Cylinder banks so that they are nice and straight when viewed from the top and front. If they're "cockeyed", they'll ruin the look of the whole model -- plus, you'll have a heck of a time trying to get the Eyebrows aligned during final assembly.
The Cylinders are painted Satin Black, the Eyebrows Gloss Black, and the Valve Covers are done with Aluminum Metalizer. The Cylinders were then dry brushed with Chrome Silver to highlight the details. Then paint the Cowl to match your chosen color scheme and you're ready to put it all together.
Align the Eyebrows to fit the contour of the Cowl and trim the bottom lip to rest on the top of the Cylinder banks. Leave the overhang at the back as it will be glued to the back of the rear Cylinder. Once you like the fit, glue the Eyebrows in place.
The Exhaust Manifolds were made up from 1/8" Aluminum wire and glued into holes drilled into the Cylinders and Cowl. The Exhaust Outlet was then made up from balsa and aluminum tube and glued into a hole drilled into the cowl. Once that was done the manifolds were painted with Rust enamel.
The Spark Plugs were made up from plastic tubes glued into holes drilled into the Cylinders, then the Secondary Leads were made up from insulated wire. The Plugs were painted with Stainless Steel Metalizer and the Leads with Satin Black.
With all the details added, the cowl is now ready to mount on the fuselage.