I am passionate about building and flying scratch built foam park jets and passing on my experiences and lessons learned from more than five years of experience. Blog is purely based on my own opinions and experiences. If you have questions, please e-mail me at scott.parkjet@gmail.com. Park Jet noise...the "other" sound of freedom :) Happy flying! Cheers, Scott
The RC Powers F-18 V3 has been an iconic park jet for a very long time and many folks have got their start in park jets building and flying one. I have built several and modified a couple even before this one.
Here is some flight video of it on 4S😎
Here is a "table talk" video of my modifications, etc.
This plane was not actually on my build list for this year, but after watching video of the USAF F-35A Demo Team at various airshows, I figured I would put one in my hangar😎
Here is my "table talk" video discussing my mods, some of the challenges I had with this plane getting it dialed in (mostly self induced 😳).
As I write this, I have over 100 flights on this plane and I thoroughly enjoy flying it, for all the videos I have done about my modified RC Powers F-35 V5, please go to this playlist on my You Tube channel
I have experimented with moving the motor around on several park jets over the years to help with better balance and performance in my planes. I wrote this article awhile back about some of my thoughts and experiences at that time about motor location in a prop and slot park jet.
In this article, I will cover how I go about moving the motor mount forward in the Mig-35B, I have done this a few times now, primarily to account for the extra weight of keeping the paper on the Dollar Tree foam in the rear part of the plane. The Mig-35B is a bit more tricky than a lot of park jets to move the motor forward, but hopefully you will get the idea if you want to experiment with other planes. Also, I will hopefully demonstrate how I modify the prop slot and other aspects of the plane to accommodate a smaller, shorter quad motor which I use pretty much exclusively in my park jets now with some excellent results.
So some of the modifications that need to be made to this or any other park jet are a function of just moving the motor forward and some are a function of using the shorter quad motor. In this write up I will try to identify which is which depending on what motor you want to put in your park jet. You might want to do it all so that if you want to experiment later with a shorter quad motor, your jet is all ready to go😎
I should also mention at this point that the plans I am using for all these measurements in this article are for a plane that will be built at 95% of scale, so I will end up with a 25.5"/648mm wingspan. Depending on the size you build your Mig-35B or any other park jet, your measurements will more than likely be different.
On most previous Mig-35B builds where I have moved the motor forward, even those not made of DTF, I has moved the motor forward by about 1". For most of the DTF planes, I found this was not quite enough to really tighten things up the way that I like them, so I am going to experiment with moving the motor and servos forward a bit more😉
One of the first things you want to is identify where the trailing edge of your KF airfoil is going to be. Even if you are not going to use them, this area is probably a good limit to set for moving the motor forward. You can move the motor too far forward and then the plane can have almost "gyroscopic torque roll" which can make launching a real challenge. I simply trace a line where the trailing edge of the KF will be so that I know the maximum I can move the prop slot forward which needs to be modified for using a shorter quad motor.
I normally start off making all the measurements and mods to the wing plate so I know where things can go, this has a domino affect on other parts of the plane, so I do everything in pencil. I have marked many of the lines in highlighter simply for this article so that they might be easier to see.
In the picture below I have marked the trailing edge of my KF and also moved the leading edge of the prop slot forward so that it will only be about 5 mm deep to allow best clearance for the quad motor. Now I know how much room I have to play with for moving my motor forward. In this picture, I have currently moved the prop slot leading edge forward about 14 mm which is how far I would move it forward if I was using a quad motor in this park jet.
I find using clear plastic rulers is easiest for this type of work as I can see through it to help measure from existing lines to the new lines. This ruler happens to be metric, so I make all measurements in mm. I have about 35 mm with which to play here after marking the leading edge of the prop slot (this is without moving the motor just yet, but since I will be moving the prop slot forward also, this is key to ensuring I don't move things too far forward).
In order to give myself a little "leeway", I decided to go with 30 mm for the motor mount. I know that I have already moved my prop slot forward by 14 mm to accommodate the shorter quad motor, so that will factor in when I look at moving servos and other air frame parts forward. So as you can see in the picture below, I essentially move everything to do with the motor mount forward by 30 mm.
Also, there are two slots which will accept tabs from the bottom part of the fuselage when it is "mated" to the wing plate, so those also need to be moved forward 30 mm as well. These are affected by the new motor mount placement, but not the new prop slot placement.
Since the leading edge of the prop slot will be moving forward 44 mm from original position, I move the rudder servo slot forward that amount also. Moving the servos forward also helps shift some weight forward to keep things tighter around the CG. This will also affect the aileron and elevon servo locations which we will move later when we get to that part.
On the Mig-35B and many other park jets for that matter, when you move the motor mount forward, it will affect a wing spar, so you will want to remeasure this to see what size the new wing spar will be. I like to leave at least 1 cm or maybe a little bit more between the end of the spar in this location and the leading edge of the wing as I will be angling/trimming the wing leading edge back after the KF airfoils are installed.
Now it is time to move on to adjusting the fuselage, this is a bit tricky, but taking your time and ensuring you measure everything correctly will pay off later in the build. In the centre part of the fuselage, I move this forward 30 mm as it is affected by moving the motor forward, but not the leading edge of the prop slot.
I then adjust the slot which will slide onto the wing plate and move that forward by 30 mm also.
This is one area where it gets a little tricky, normally the area where it says "cut out and save" would still be attached as part of the fuselage if built stock, however now it is not after moving some lines for the modification. I cut this out and save it as it is critical to support the bottom of the fuselage after "mating" it to the wing plate.
Next, it is time to adjust the top parts of the fuselage that will be on the top of the wing plate after "mating" the fuselage and wing plate. These are primarily affected by moving the leading edge of the prop slot forward to accept a shorter quad racing motor, so 44 mm is the key measurement here.
This also affects the tab and slot to align the electronics bay door. I measured it to 30 mm, you can measure to whatever size you want. In the picture immediately below, I measured the "slot" on the side piece of the fuselage to accept the tab from the electronics bay door.
Here I moved the back of the electronics bay door forward by 44 mm to accept the new leading edge of the prop slot.
Then I adjusted the tab to 30 mm to fit into the slot on the side of the fuselage.
Since I moved the leading edge of the motor mount forward so much, I also added some to the back plate/trailing edge of the motor mount to maintain some structure. I like to keep my prop slots a little larger to allow for best airflow to and from the prop, so I split the difference between 30 and 44 mm and moved the trailing edge of the prop slot forward by 37 mm.
Next, time to move on to the nacelles which need to be shortened for both the motor mount mod and the quad motor in this situation. First I normally move the servos forward as shown in the pictures below. Since I have already moved the rudder servo slot forward 44 mm in the wing plate, I do the same for the aileron and elevon servos.
You will note below that moving the aileron servo forward interferes with a tab that goes into the wing plate, so I simply measured off 15 mm in this situation, remembering to carry this over to the tab on the wing plate as you can see in the second picture.
In these following pictures, I modified the inside part of the nacelle so that the tab is moved forward to fit into the slot I moved forward by 30 mm when moving the motor mount forward.
Then I moved the trailing edge of the nacelle forward by 44 mm to allow for the fact the leading edge of the prop slot is also moved forward by 44 mm. This is something to check after the motor is installed by turning the motor by hand with the prop installed first to ensure it does not contact anything before giving it power and chopping up your plane😮
One last thing to check is to remove a bit from the top of the motor mount (I start with about 5 mm and then adjust as needed). If the top of the motor mount is left the way it is, the electronics bay door won't lay flush.
Hopefully this has been somewhat helpful. Moving the motor forward on the Mig-35B is a little trickier than with some other park jets, but I have done it on three Mig-35Bs thus far and it has worked out well. I have moved the motor forward on several different park jets, the principles are basically the same, just remember it can create a bit of a "domino affect", so always best to figure things out and double check before cutting out the foam.
Now that you have your GCRC F-22 Mini V3 ready to go, please remember to follow the recommended CG and throws per the documentation that is available with the plans. We went through a lot of testing and discussion over these to try and ensure folks had as much success as possible on their maiden flight, so please start with those. After you get your F-22 Mini V3 flying, if you want to adjust the throws and your balance point, be my guest, but we are quite confident that if you follow our recommendations you will have the best chance of success.😃
As it states in the features and specs document that comes with your plans, the recommended starting throws are 18 mm one way in the elevator (pitch) portion of the elevon and 30 mm one way in the aileron (roll) portion of the elevon.
Simply hold a ruler on the edge at the back of the elevon like so to adjust your starting throws correctly.
As for expo, I won't tell you what to set for that, whatever you feel comfortable with, but you might want to add 10% over what you normally use until you get the feel for how agile this plane is.
I shot this video awhile back about how I do my maiden flights, just food for thought, since you are probably not a beginner flying this plane, use what works for you😉
With the recommended power setup, I find about 40-45% throttle is sufficient to get the plane flying. I found this plane a bit of a handful to fly in any wind over 5 mph, so if possible, do your maiden flight with less than about 5 mph of wind.
The GCRC F-22 Mini V3 accelerates and changes direction very quickly even with the recommended throws, so give yourself lots of altitude and airspace on the first few flights until you get used to it's response to power and control inputs.
Best of luck on your maiden flight and I wish you many hours of enjoyment with this very fast, aerobatic park jet😎
Now that the bulk of the "fussy" work has been done, it is time to get this little beauty put together😊
I like to start with the fuselage so that the glue can be setting up and curing while I work on the rest of the plane.
If you are interested in what glues and tapes I use for building my park jets, please watch this video.
First, I like to put some clear packing tape down the center/bottom of the fuselage. This is not absolutely necessary, but will help prevent pulling the paper off the foam during numerous battery installations and removals over the life of the plane.
Then I install the velcro to secure the battery, in this picture I used three 2" lengths and started at the back where the score lines are to curve the back end of the fuselage inwards. This is sufficient for anywhere from a 1000-1300 Mah 3S battery.
To fold up the fuselage, you will make what is called a "B fold" where the side plates are beside the bottom plate as hopefully you can see in this picture. It is important to dry fit this before gluing so that you ensure everything will fit together nicely.
This is one of the few areas in the build where I find using hot glue works the easiest. I simply run a bead along the side of the bottom plate, then fold the sides in as shown above and ensure they dry at 90 degrees to each other. Do one side at a time.
Ensure to bend in the sides at the rear of the fuselage so that they are flush with the bottom and I find it easiest to "roll" the nose along the table to ensure the paper from the middle piece bonds to the side pieces. This picture was taken after my plane was completed, but hopefully you get the picture, I found it easier to form the bend in the foam by pressing/rolling it along the table til the glue took hold.😊
Once you are happy with how the sides of the fuselage have set up, glue on the top nose piece, using the slots in the side of the fuselage and the tabs on the nose piece for alignment. Take your time curving the foam and once you are happy with the dry fit, glue in place. I find it a good idea to use some masking tape to hold things in place while the glue dries.
You can install the battery hatch door at this point or wait until later. I simply hinge mine using a piece of transparent duct tape like I use for my elevon hinges.
While the glue is setting up on the fuselage, I will hinge my elevons using transparent duct tape. If you want to see how I do this, please watch this video.
To ensure I have everything centered and aligned, I like to make a small mark in the very center of the back of the wing plate on top so I can align my elevons.
I then tape the top of the hinge, ensuring everything is lined up correctly. I ensure to cut away any tape that covers slots where other parts will be placed. Also, I cut away some of the tape on either side of the mark you can see where my control horn will go. This way, no tape interferes with the glue joint later on. At this point, if you are planning on painting the plane, I would lightly scuff the surface of the tape with sand paper until it no longer shines. Otherwise, if you paint on the shiny surface, the paint can easily crack and peel off.
After the hinges are done on the top, I like to add a little "insurance" to the bottom of the elevon hinges as shown in the pictures below. Again, this is not required, but gives me a little extra piece of mind. I also demonstrate how to do this in the video above. This may cause your elevons to deflect up due to a bit of tension on the tape, but don't worry, the servo will be able to handle this and I would always rather have my elevons want to deflect up than down😉
Next, I install my control horns. I use the same control horns as Flite Test, but you can use whatever you have. Simply ensure the holes in the control horn are directly over the hinge line on both sides and your control horns are the same height, otherwise you can run into issues with your elevons deflecting unevenly.
I start by lining up the control horn, pressing down into the foam to mark the location.
Then using my knife, I carefully remove a small channel of foam where the control horn will go.
Control horn now lined up and in place. I secure these using five minute epoxy, I put a small amount of epoxy in the groove, place the control horn in and then if need be add a little bit more epoxy along the sides of the control horn to ensure they are securely attached and then let them dry fully before handling the plane.
Once the wing plate and fuselage are ready for handling, it is a simple job to slide the fuselage onto the wing plate, ensuring the fuselage lines up with the slot in the wing plate. The wing plate should be flush with the inside of the fuselage on both sides as you can hopefully see in this picture of one side.
I pinned the top fuselage into place while the glue dries to ensure it lines up well with the bottom since the motor mount will be going into this "square" area shaped by the top and bottom parts of the fuselage.
Leave these two pieces to dry completely before handling. In the meantime, you can get your motor mounted on the motor mount using bolts that come with the motor. Please note that the Racerstar BR2406S 2600 kv motor has an older 16x19 mm bolt pattern, so there is only one way it will mount to ensure the wires come out the top of the motor mount and fit through the groove you cut in the motor mount.
It doesn't really matter if you have the prop on or off at this point, if you feel safer, wait until later to install the prop after all the other electronics are installed. It does make it much easier to ensure the motor is aligned vertically and horizontally if you mount it to the wooden motor mount before gluing into the plane. I would recommend waiting til after you have installed your KFs and sanded them before mounting the motor, that way you won't get any sanding dust in the motor during that process.
After the fuselage and wing plate are securely glued together, it is time to mount the landing skids and the nacelles.
Make sure that the landing skids are oriented so that the two slots for the tabs from the nacelles are in the front. Ensure that the landing skids are perpendicular to the wing plate so that nothing gets crooked when you install the nacelle. You can glue the nacelle in place before the glue is dry on the landing skids, just ensure you square everything up and if necessary pin in place while the glue cures.
Next, install the KFs, either KF2 (just on the top) or KF4 (top and bottom). My personal recommendation is to go with KF4 as this is a very fast and agile park jet, so KF4 will give the best stability at speed and best wind penetration. It is also very important to remove the paper from both sides of both your KF airfoils. I shot this video about how I do KF4 airfoils on my park jets, I would recommend you watch it, starting at about 25:55 of the video. The first 25 minutes of the video discusses how I size KF airfoils for planes without them, but all that homework has been done for you with the GCRC F-22 Mini V3😃
As mentioned in the video, a couple of critical things is to ensure you mark the CG on the top/bottom or both of the KF airfoils before gluing them to the plane so that you still know where the CG is after marking it on the wing plate. You probably have already marked the top KF as the CG is marked on that part on the plans. Secondly, it is critical to ensure the trailing edges of your KF4 airfoils are even. Don't worry if the front on the leading edge of the wing is off, you are going to trim and shape that later as I demonstrate in the video. If you have your trailing edges off by even a mm or two, it will cause uneven lift on one or even both wings and your plane will become a bit of a handful to fly😨
I like to leave the KF airfoils to dry overnight so that trimming and sanding the leading edge the next day is much easier. The finished product should look something like this after shaping and sanding.
Note that I also tapered the edge of the top KF/wing plate of the "intake" area. I use 150 grit sandpaper and just a gentle touch. Paperless DTF can be soft and it is very easy to gouge it if you sand too hard.
Next, I installed the motor mount support pieces of foam that go behind the motor mount. I trimmed mine down a little bit to make it easier to fit them in as my fingers are a bit "sausage like"😉
Once those are dry and secure, I install my motor mount, using again 5 minute epoxy. This gives you some time to get it aligned by looking down the back plate behind the prop slot to ensure vertical alignment and then the line you marked on the bottom for horizontal alignment. I know these aren't the best pictures to demonstrate that, but hopefully you know what I mean.😊
Once the motor was dry, you can install your servos, run your servo wires, I use hot glue to install my servos as it makes it easier to remove them if they need to be replaced. Please note that the servo glues flush to the wing plate and is recessed down into the top KF. If your servo does not fit flush to the wing plate, you may need to trim a bit off your KF in this area to make that happen, always important to dry fit first. Do not install your pushrods yet as they will get in the way when setting the angle on your vertical stabilizers.
This is also a good time to place your receiver and ESC in the plane. I would do this before installing the vertical stabs as it is much easier to handle the plane without worrying about banging those into something. I like to place my ESC on the right hand side, since the prop will be spinning clockwise when looking from the rear of the plane, this extra weight on the right helps a bit with torque roll. If you choose to use a pusher prop and it spins the opposite direction, you might consider swapping the ESC and receiver positions, but it isn't overly critical unless you find torque roll is an issue.😊 Note that I placed both components back as far as they will go against the piece of bamboo skewer that is used to secure the hatch. You can install this piece of skewer before or after you install the ESC and receiver. I mount these components using velcro anyway, so it is easy to move them a little bit if need be and they can be removed if they are causing you troubles.
A small rubber band helps to secure the hatch in position for flying.
Next, install the vertical stabilizers, using the angle guide from the plans to ensure you get the correct angle on both sides. If your vertical stabilizers are not equally angled, it could cause stability and tracking issues. Pin into place if necessary to ensure the vertical stabilizer is angled correctly until the glue dries. Note that I cut the corner off the jig so that I didn't glue it to the plane where the glue seam runs between the stabilizer and the wing plate.
Once the vertical stabilizers are dry, it is a good idea to do any painting before installing the pushrods. I shot this video awhile ago about how I paint my planes.
On the prototype plane, I simply used some inexpensive magic markers I got from the dollar store with colors and a pattern that would make it easy for me to see in the air. This just takes a few minutes and adds no weight.😊
For my final plane, I did a simple "camo" pattern using diluted acrylic craft paints that I brushed on by hand.
Two important things to remember when painting your plane. Always test whatever paint you choose on some scrap foam to ensure it is not going to eat the foam. Normal "rattle can" paints from the hardware store are normally not good choices as the propellant can melt the foam. Secondly, also use as thin a coat as you can, the weight of the paint can add up quickly. My paint job on my final build added about 12 gr of weight to my plane. I just make the decals from paper, print them off on my printer and glue them on. I like to have a plane that looks good in the air and that I can see easily, not necessarily one that might win "best in show" sitting on the table at the field😉
Once the paint is dry, time to add your pushrods and ensure that the control surfaces are level. I like to do this with power on to the servos, so unless you have a kill switch on your transmitter to ensure your prop won't start up if you bump your throttle, remove the prop for safety.
I like to hold a ruler on it's side to ensure that my control surface is level with the wing plate. Ensure at this point you have no trim, sub trim or anything else that might effect the surface from being completely neutral.
So there you have it, one GCRC F-22 Mini V3 done and assembled. But, we are not quite done yet, in the next article, I will discuss throws, preparing for your maiden flight and some tips about flying this spirited little steed😎
