RCP F18 V3M Ready to fly :)

Hi everyone -

With a couple days of bad weather keeping me indoors, I have been very busy the last two days and finished up my modified RCP F18 V3.

I will eventually do a more detailed walkaround video after I maiden the plane and start the dialing in process.  I have a paint job in mind, but since this is a test bed and I will probably be trimming some bits off the trailing edge of the KF airfoils, I decided to go with just some magic marker on the canopy and "nozzles" and some painter's tape on the wing tips to help with tracking and orientation.  Although very simple, I have found with testing the NAMC Mig-35 and Mig-FA that this is a very effective scheme to help me keep track of the plane in just about any sky condition.

So after all the hacking and slashing, I ended up with these dimensions

• I shortened the plane by 2.1", my plane is 42.25" long, the stock build is 44.35" long.  I am hoping this will make the plane more responsive overall, but especially in the pitch axis as it is now more "compact";
• My AUW with a 2200 3S battery is 599 gr/21.1 oz which is a good weight for this plane.  I didn't change the wing area, so wing loading should still be fine.

With moving the motor 1" forward, I have moved the stock CG back by 1" just as a starting point, here is a picture of what my electronics bay looks like with the battery placed to balance on this new CG.  Obviously I will only find the true CG once I have had a chance to fly and adjust it for balance and KF dimensions.  In this picture if you look on the right hand side, the black "+" indicates the new CG I will start with.  I made several little plus signs aft of that in 1/4" increments to give me an idea of how much I am moving it as I dial in the plane.  I am assuming it will only be going back as from my previous V3 experience, the plane balanced nose heavy on stock CG.

I placed my rudder servos a bit farther back that I normally would like, but since I will more than likely be trimming some foam off the back of the KF airfoils as I dial in the plane, I figured it would be easier with them out of the way.  I still need to trim off the extra pushrod that is sticking so far forward.

When I measure from the front of the battery to the tip of the bullet nut on the motor mount which in previous testing I referred to as the PMI (polar moment of inertia), I get 12.5" which is a huge improvement in tightening this up and hopefully making the plane even more responsive, precise and maneuverable.  With the old setup, my battery was all the way up against the bulkhead which gave me a stock built PMI of 18".  Big difference.

Here is a side shot, it does look like a much different plane than the stock, I can notice the 2" less in length.  I shortened the nose by about 5/8", but I think it still looks pretty good, not as "pointy", but that is a purely aesthetic thing for my preference.  

If using the length of the plane as a percentage, with the new length and motor location, the motor is located at 61% from the nose which is almost identical to where it is on the NAMC Mig-35.  Again, I'm hoping getting the CG, CT and CM closer together I will be getting better balance and overall performance.  

Above and below you can see that I mounted my servos and ran my pushrods externally as I like to do on all my planes, I find it makes for much easier, more secure installation and adjustment and keeps the prop wash area clean of as few obstructions as possible.

So I am very excited not only to have an F18 in my "hangar" again, but to start some testing and comparison side by side with the NAMC Mig-35 to see if some of the principles built into the Mig-35 carry over to the F18 which is a very different airframe style with a more straight wing.  Let the field testing begin!

Cheers,

Scott

RCP F18 V3M Update #2

Hi everyone -

I have been plugging away slowly on my modified RCP F18V3 and have reached the stage where I am ready for the main assembly.  In this first picture I wanted to point out a different wing reinforcement setup I am going to experiment with.  On our NAMC Mig-35 and Mig-FA, we have had great success with a "Pi" shaped setup, named as such because it resembles the mathematical symbol "Pi".  On the F18 because of the different wing shape and the fact that I moved the motor mount forward by 1", I was not going to be able to run as long a main wing spar as if I built stock.  So I am going to experiment with this "A" shaped plan.  The main spar is 4mm carbon rod, very stiff, a piece about 16.5" long.  The two pieces of carbon fibre that angle along the leading edge of the wing out to the wing tip are 3mm carbon tube, each piece 12.5" long.  I didn't come up with these lengths using any kind of scientific formula, I just had them laying around and they seemed to fit my plan just fine.  Already I can tell it will be a very stiff, strong wing, even stronger once I install the KF4 airfoils.

It might be hard to see the line in the picture, so I put a pen to point where the line is so I could ensure that the inside tip of the 3mm carbon tube pieces will get locked under the nacelles/intakes when those are glued on.  As we learned from the NAMC Mig-35/FA, this really helps lock in the carbon fibre tube to make as solid a wing reinforcement as possible.

I attached the back plate/horizontal stab/elevon piece back on to the main wing plate and I have also installed my elevon control horns.  I find it so much easier to do this when it is still a flat piece of foam to work with.  On this wing plate, I have also sanded the trailing edge of the wing/aileron so that it is symmetrically tapered to allow for smooth airflow.  I also did the same to the leading edge of the horizontal stab/elevon and the trailing edge of the elevon, the leading and trailing edges of the prop slot, all to allow for smoothest airflow possible.

I have also installed a short piece of 3mm carbon fibre tube in each vertical stab, these pieces are 5.5" long, again nothing scientific, just what I had laying around.  The side shown of the vert stab/rudder assembly will actually be on the outside of the plane with the smooth side of the hinge on the inside.  This hopefully keeps the prop wash area between the stabs/rudders as smooth as possible by having the bevelled part of the hinge on the outside.  You can see a blue line I drew so that when the stab/rudder is installed on the plane, a portion of the carbon tube will extend below the wing plate to lock it in nice and tight and hopefully keep the vertical stabs from fluttering in the wind and high alpha.

I also assembled the fuselage and installed the canopy.  I tapered the canopy front and back by narrowing the centre piece by 1/4" on both sides giving a more oval shape to not only make it look good, but hopefully more sleek through the air.  The front part of the fuselage has been shaved down with a knife to remove the square edges of the score lines, then filled with a very lightweight finishing spackle, then that has all been sanded as smooth and sleek as I can get it to present the least amount of drag.

Next up is to put the plane together short of installing the vert stabs/rudders, I will do that last after final sanding as I find it easier to handle the plane without the vert stabs/rudders in the way when I am constantly flipping the plane on it's back to adjust elevon and aileron control setups.

More to follow very soon, I'm getting more excited at each stage of the build to see how this modified F18 is going to turn out and perform :)

Cheers,

Scott

RCP F18 V3M - First update

Hi everyone -

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 shows in a bit more detail what I did to move the motor mount forward.  You will also notice I moved the back part of the centre gap further forward by 1".  This area accepts the back part of the fuselage and I needed to maintain some foam between the motor mount and this area for strength and carbon rod installation.  I prefer a straight trailing edge to my prop slots, so I just drew back to where the original trailing edge would be, this will give the prop plenty of room to "breathe".

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

Modified RCP F18 V3 - initial thoughts

Hi everyone -

Having grown up with the CF18 as a fighter controller in the Canadian Air Force for almost 30 yrs, I have always had a soft spot in my heart for the F18 Hornet.  From a standpoint of RC modelling, the RC Powers F18 V3 is probably in the top five of my all time favorite park jets.  The F18 V3 helped me take my flying skill and confidence to an entirely new level and for that I will always be thankful.

I will caveat this and follow on posts about my modified F18 V3 by saying that if you are a beginner or new to the hobby, the F18 V3 built stock is by far one of the best planes you can build and fly to help you get started.  Also, RCP offers the plans for free now, so no requirement to buy anything other than components and build materials.  As my RC parkjet career approaches it's 3rd anniversary however, I am constantly looking for ways to push the envelope with my planes to get them to look and fly the way that I like them, hence why the modifications I and my NAMC partner Stephan have made to almost every plane we have ever built.  To me this is no comment on the designer, but rather the beauty of scratch building foam park jets as it allows a person to have the freedom to experiment.  As we found with developing the NAMC Mig-35 and Mig-FA, you just never know what you might find out with some thorough research and testing.

This old gal had just over 350 flights on her when I decided to retire her

About a year and a half ago, I did play around with some significant modifications to the F18 V3 which I discuss in this video

Around that time, RCP released the V4 series of their planes and Stephan and I started doing some serious work modifying and testing the Mig-29 V4 which led to our NAMC Mig-35 and as they say the rest is history.  However, playing around some more with the F18 V3 has always been on a "slow simmer" at the back of my old brain, so time to bring it forward and have some fun.  Plus I had an old set of plans collecting dust in my closet that needed to get used up. :)

Through the development and testing that has gone one with the Mig-35 and Mig-FA for almost the last year, my learning curve has been very steep but incredibly rewarding.  Stephan's scientific approach to design and our shared desire to squeeze the maximum performance from our planes while still having them look amazing has led us to a very unique place in park jet design and testing.  Or at least I like to think so :) 

So armed with this knowledge I have learned from Stephan and the experience I have gained through 940 + flights testing the Mig-35 and Mig-FA, I see great potential for many of these principles to cross over to another airframe, the F18.  Plus, depending on how the testing turns out, it will be continued proof that the science behind why the Mig-35 and Mig-FA perform so well is universal to any park jet platform.

So here are just a few things I think can be improved on the F18 V3 to make it a more tight, precise, high performance park jet.  Many of these principles I discuss in more detail in this video below.  Additionally, I would encourage you to go to our NAMC video page to watch Stephan's excellent educational videos on PMI/centre of gravity and centre of mass as it relates to aircraft design and performance.

• shorten the polar moment of inertia (PMI).  As most of us who have flown this plane discovered, we needed our battery all the way against the bulkhead to balance it, meaning the weight was spread over a very large area of the longitudinal axis making pitch manoeuvres and turning more challenging than it needs to be;
• find the correct CG (centre of gravity) in all three axes.  First is the longitudinal or pitch axis.  Before Stephan opened my eyes to other possibilities, I always strived to balance my plane on the stock (or by the plans) CG.  This is fine, but by their own admission, most RCP planes are balanced nose heavy to help beginners and looking back on it, I'm sure I was flying my F18 far too nose heavy;
• work to concentrate the CG, CM (centre of mass) and CT (centre of thrust or motor location) in as tight an area as possible.  As we found with the Mig-35 and Mig-FA, this is critical to making manoeuvring tight, precise and effortless from a standpoint of control surface deflection.  Meaning having science working with me instead of against me;
• fine tune the size of the control surfaces.  I had started to do this somewhat with the plane in the first video above, but I still need to fine tune the ailerons and rudders; 
• dial in the size and location of the KF airfoils, especially how the trailing edge of the airfoil relates to what I find as the optimum CG; and
• set up the airplane and transmitter using the principles described in the second video above to maximize feel and precision.

So, how do I plan on doing this?

• First off, I will shorten the overall length of the plane by about 1.5" and increase the wingspan by about 1/2".  This will bring the dimensions into scale proportion not only to help the plane move more quickly and easily but hopefully make it look a little better too.  I have always felt the nose was a bit too "pointy" for my taste, but again, personal preference does enter into things occasionally;
• I will move the motor forward 1".  This should help shorten the PMI and move the CG back bringing the CG, CM and CT closer together;
• Once I have a flying prototype, I will spend several flights dialing in the correct CG using methods described in the second video above.  I will also assess the "vertical" CG to determine if the plane is top or bottom heavy WRT to battery location;
• I will start off with the stock KF airfoils and then once I start the final dialing in on the optimum CG will modify them until the trailing edge of the KF is coincident with the CG for maximum performance; and
• servo location will be planned to try and concentrate the weight around or very close to the CG and to allow for best setup for precision flying.

So although this blog has been inactive for awhile, I think it is the best place to discuss my mods to what I will call from now on the F18 V3M (M for modified).  

I will continue to update as I move along in the build and testing process.  Time to get cutting some foam! :)

Cheers,

Scott