Since my last post on my modified RCP F18 V3, I have been busy with the calculator, ruler, pencil and quite often the eraser :/ drawing the mods I discussed in the first post. All the parts are now cut out and the weight of raw foam weighs 153 gr/5.4 oz (this includes the four pieces needed to make the KF4 airfoils).
I tried to remember to take some pictures as I went along to show the modifications I have made thus far, but when I am all done, I will do a "walk around" video that will describe in detail all the changes I made from stock to permit the testing I want to do. Here are a few pictures that I did remember to take. The picture below shows an overview of what I did to the wing plate thus far to accommodate moving the motor further forward and to adapt to changes I made to the elevons and back plate. To attempt to get the right scale wingspan to length ratio, I extended the wing span by 1/4" on each end.
This picture below hopefully shows how I trimmed about 1/4" off the trailing edge of the wing since I am moving the elevons forward a bit to try and achieve scale proportions between wingspan and overall length. We found in testing on many different platforms (RCP Mig-29 V4, NAMC Mig-35/Mig-FA) that an aileron span of about 60% of the wing span on that side works quite well giving the best control for basic flying and or when we wanted to play with spoilers/flaps for high alpha or other advanced aerobatics. Since the F18 wing has a fairly deep chord, I left the chord of the aileron stock.
In order to allow me to play around with the elevon sizing and to be able to keep a fixed horizontal stabilizer similar to several other park jets, I cut the back plate part of the plans away from the wing before cutting as I couldn't orient the entire big piece on my sheet of Depron with the elevons/horizontal stabs attached. Additionally, this will make it much easier to sand the elevons, trailing edge of the wing and ailerons before assembling the pieces. I will discuss this further in follow on posts. When the time comes, I will reattach the back plate with epoxy or Foam Cure, it will be a very strong joint, in my experience the foam will probably break before the glue joint does.
Hopefully in this picture, you can see where I will be cutting the hinge line for the elevons. It shows up a bit with a thin blue line from marking it with a pen. The elevons are about 88% of stock, I printed the portion of the tiled plans that includes the elevon at 88% and then made some modifications to the "nozzle" location and hinge line so that it would all fit together. Hopefully it shows up in the second picture under this paragraph.
To accommodate moving the motor forward, I had to trim the fuselage somewhat, on the end where the ruler is I trimmed 1" off and moved the tabs as shown by where the pen is 1" forward so that they would fit into their new slot on the wing plate. I also shortened the nose by about 1/2 - 5/8", I just kind of roughly drew on the paper before cutting things out, so hopefully the nose will still look OK. I can always shape and sand it to how I want it to look anyway which is part of my build plan.
On the nacelles, I trimmed 1" off the back where the blue pen is pointing to ensure no interference with the prop with the new motor location. I have always trimmed the fin off the back of the side piece of the nacelle, mostly for looks and weight reduction as you can see where the orange highlighter pen is pointing. This will put the back part of the side piece about even with the front of the elevon hinge line. Also, since I know from hard earned experience how weight sensitive the F18 V3 can be, any weight reduction I can make without sacrificing structural strength is OK with me.
Here are the KF airfoils cut out. I have found with my previous modified F18 and with many other planes that extending the top airfoil all the way forward to cover the LERX helps the stability and smoothness of the plane's handling. It does add a bit more weight, but is worth it in the long run.
I have my components picked out, the receiver has been bound, all the servos have been checked and are ready to go. I will be using a Deal Extreme 2212/6 2700 Kv motor and 6x3 EMP prop with a Turnigy Plush 40A ESC. The servos are 9 gram nylon gear servos from RC Timer. I will most likely be using a 2200 Mah 3S battery. I am hoping to get my finished weight (with battery) around the 21.5 oz range as I have found that is about the best wing loading for my preference, gives good stability and wind penetration without over stressing the wing. All the components I am using are listed on the NAMC Recommended Parts List.
I should mention that my build will be of a "composite" nature WRT types of foam used. The wing plate, back plate, vertical stabs/rudders, all other control surfaces, nacelles and internal structure will be built with 6mm Depron as I prefer the added strength and stiffness in these areas. The fuselage and canopy will be built with Fli-Value XPS foam (similar to MPF or model plane foam) as it is less expensive than Depron and easier to bend and sand. The KF airfoils will be made from paperless dollar store foam.
Well, that is probably enough for now, next steps are to install the carbon reinforcement, bevel and attach all the control surfaces, do some sanding of certain areas of the wing plate (always much easier for me to do before assembling the whole plane). More to follow in the days to come :).
Cheers,
Scott
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