CHAPTER II - Air intake tube construction
Because the main BBI - Elite Force kit was very poor on detail and had the air intake tube sealed, I had to first open the air intake by cutting the plastic and then build from scratch the approximately 30cm long tube, leading to the engine's 1st stage blades described in detail into previous Chapter I. Just because the F-16's air intake tube is not just a straight line tube, the idea of scale building with plastic card was rejected from the first moment. If you notice, the F-16's air intake tube is curved in both X and Y axes while heading to the engine's 1st stage blades.
Source: http://www.f-16.net
For this reason, I decide that a "negative image" cast of the air intake tube should be made and build the tube model using this cast, with two available & different methods:
- The first method is based on a solid rock (made by balsa, epoxy filler, plastic etc) "negative image" cast of the air intake tube on which I would try to vacum form some air intake tube "half" parts (left-right or upper-lower). Some very thin (and fragile too) plastic parts could be produced, but with doubtful contact between the two "halfs". For sure, the tube "halfs" would leave visible contact line marks across the construction, that should be filled with putty and carefully sanded on a fragile and extra thin plastic material.
- The second method is based on a deliberately fragile and hollow "negative image" cast made by soft materials (such as plaster and cardboard), that could easily be decomposed and removed after sinking into water. I decide to follow the second method, knowing that I had only one shot to try, with no mistakes allowed, considering that the cast would be destroyed after use, but I could have one-piece tube as a result, without any marks or lines inside the tube and also avoid unneccessary sanding with doubtful results.
By selecting the second way, which was more desired and realistic for me, I finally produced one solid rock one-piece air intake tube, very accurate on scale, following exactly the real air intake tube curves and present to fellow modelers a mighty unconventional way of scale building to keep in their mind for any future projects of their own. That's why, I present the project with step-by-step pictures, to provide any possible help to understand how did it. After all, I believe that scale modeling is not just cutting plastic parts straight from the kit box or maybe use some resin accessories already checked to fit perfect into models, but combining arts, skills, techniques and finally use our brain to invent new methods in order to have a realistic result.
Having the official F-16 Block 52 blueprints copied from the T.O manual, I got the exact dimensions of the air intake tube, print them down on a cutaway image and using scissor and simple cardboard, I create a the "negative image" of the air intake tube, basic spine. As soon as the spine made by cardboard was set on a straight line, it was wrapped around with a cloth net found into the 1st aid kit. Small quantities of plaster, highly thinned with water, applied on the cloth net with a brush, to build the first layer of a hollow plaster cast, which would become the "negative image" of the air intake tube.
Materials like plaster, start as a dry powder that is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after drying, and can be easily manipulated with metal tools or even sandpaper. These characteristics make plaster suitable for a finishing, rather than a load-bearing material and that exactly is what I'm looking for on this air intake tube construction. Keep in mind that adding salt into wet plaster mixture, reduce the plaster's hardening time and adding vinegar into wet plaster mixture, extend the plaster's hardening time. When the first layer of thinned plaster applied on the net was dry and hard enough to hold the basic spine made by cardboard, a second thin layer of plaster was applied to form the curves of the air intake tube, following the lines of the pre-cutting cardboard. The basic idea, is to keep this plaster cast hollow, accurate on scale and as thin as possible trying not to apply extra stuff where is no needed. When the plaster cast was dry and hardened, tiny quantities of modeling putty added to close minor scratches and pores on plaster cast surface, brushed with water based clue, painted in black color, dry sanded and finally sprayed overall with gloss shiny coat.
Johnson's baby oil (thin layers of vaseline based mixtures can be used also) brushed as a segregative material for later purpose and generous quantities of polyester filler applied on the plaster cast. The specific polyester filler I used, is enriched with fiberglass grains to enforce the final construction. The filler should be always used with the proper catalyst which provides a solid rock build and approximately 5 to 10 minutes time window to form it into shape.
When the plaster cast used as a "negative image" of the air intake tube, was fully covered with a 3-4 mm thick layer of polyester filler enriched with fiberglass grains and had enough time to polymerize and get solid rock, it was sunk into water and stayed wet overnight, in order to let the enclosed cast made by cardboard and plaster get moistened and decomposed.
Staying underwater for few hours, waiting for the enclosed cast made by cardboard and plaster to get decomposed and become soft, mixed pieces of cloth net, thinned plaster and moistened cardboard were removed with caution.
By the time all the thinned plaster, dissolved cardboard pieces and cloth net remains were removed, the tube was sanded properly, washed and attached by using cyanoacrylic glue on the F-16 lower fuselage "mouth" housing. Epoxy putty and polyester filler used to close the huge gaps.
