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Old 10-24-2003, 08:33 AM
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Default Scale Engine Cooling Fuselage Modification

To accomplish this modificatio, the area inside the fuselage is built up with balsa strips, so that the outside can be sanded and rounded. This of course is easiest to do if the fuselage is not yet completed, but it could be performed on a completed one also if the ambition is there. Ideally, start with the upper half of the fuselage completed (but not the bottom) except for the installation of F1. F2 should be installed, but not F1. Like I said tho, you could also do this mod to a completed Corsair, it will just be more difficult.

Begin by adding 3/16” thick planks to the inside of the fuselage between F2 and F3. You should pre- warp some balsa sheeting first by soaking with water and wrapping around something round and about the right diameter (like the cowl). Then cut pieces to size so that they will fill the gaps between the 3/16” square stingers, and glue them into place with thick CA. These pieces should extend all the between F2 and F3. When finished with the top half, fill any gaps with epoxy/ microballoon mix.

Now that the inside is more or less round (the stringers are even with the planks), you can add another layer of planks, and you can use bigger pieces since they do not have to fit between the stringers. These do not need to go all the way back to F3: they can be shortened to about 2” if desired. Also, thickness is not important. You will need to build it up a total of about 1” (counting the first layer, which is 3/16” thick), but how you get there is up to you. Thinner balsa bends easier, but requires more layers. It needs to be 1” thick up to F2 only: each successive layer can be shorter, and they do not need to go all the way back to F3.

When you have completed the fuselage top, go ahead and complete the fuselage by adding on the lower section, then add planks as described above. It will be more difficult than the top because you have less room to work with now.

When adding the planking is completed, it is time to remove material from the outside. Begin with by using a compass to draw a 5” diameter circle on the outside (engine side) of F2 This circle must be centered, so that the line is equidistant from the fuselage edge ( about 1” ) all the way around.

Next, measure 1 1/4” back from the front of F2, at several places( 4 ~ 8) around the fuselage. Use a thick tape, such as electrical tape, and wrap around the fuselage, lining up one edge with the marks, so that the tape exposes the 1 1/4” area directly behind F2 but covers the area directly behind the marks.

Next, draw a vertical line on F2, which ends exactly on top of F2. Now measure and mark 2 lines, each 1 1/8” from the vertical center line, one on each side. Apply tape to these lines, with the edges on the lines and the covering the area on the side towards the vertical center line. Extend these tape strips over the top of F2 and onto the top of the fuselage, going straight back, and extending beyond the tape which was previously applied around the fuselage.

You are now ready to remove wood. You can start out with a hobby saw to remove some large chunks, but eventually you will need a sanding “T” bar. The object is to remove the wood up to the tape. That means sanding the area flat, so that it appears that the fuselage lines have an edge that bevels in about 45 deg., then bevels again another 45 deg. at F2 (see drawing).

When complete, remove the tape and switch to FINE sandpaper (320 grit max, 400 best) and gently round the edge on the fuselage SLIGHTLY. Look at the scale drawing again: this is a fairly tight radius, so don’t sand too much (like I did).

The fuselage mod is now completed. Cover and/ or paint to your heart’s desire. Add a thin layer of ‘glass if you want (I didn’t). The only thing left to do now is modify F1 so that it will allow cowl attachment AND allow air to exit at the cowl flap area. I just set up F1 for cowl installation, then squared it off by drawing 3/8” diameter circles around the cowl mounting holes, drawing lines to connect these circles at the outermost areas, then sawing off the 4 crescents so that it ending up being nearly square. I use blind nuts for cowl attachment, I suggest that you mount the blind nuts prior to attaching F1 to F2, as it may be difficult once F1 is attached. You may also want to consider adding a layer of ‘glass cloth to the front of F1, especially in the cowl mounting tab areas for additional strength.
If you are building a 'red box' Corsair, F1 needs to be at least double it's original thickness, either by laminating another piece of ply to it OR just making a new one from 1/8" heavy ply or bigger. Also, I did not construct my 'red box' with the maple motor mounts: I replaced the maple with balsa, cut them off even with the firewall, and used a conventional motor mount.

This drawing, like the others, is 1/8 scale/ actual scale size for Top Flight (and Royal) .60 size Corsairs. In order to print it correct size, you may need to download it first, then open it in a program such as Adobe Photo Deluxe, and print it from there. It may require cropping and/ or rotating in order to fit on a 8 1/2" x 11" page.
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