Building an RC Plane usually means modifying the plans and design a bit to truly make it functional. In this case, I decided to add some plywood access covers for the retractable landing gear in a TopFlite BeechCraft Bonanza balsa kit. The plans did not call for it, but I have built enough rc plane kits to know better than to follow the instructions completely. Sure, you can build the kit and create a beautiful airplane, but that doesn’t mean you cannot modify it and improve the design.
Ok, so the left wing landing gear mounting plate is complete. What about the Right Wing? Glad you asked. This post deals with finding the best location for my Beechcraft Bonanza’s retractable landing gear in the right wing.
Use Left Wing Landing Gear Location As Reference:
I took some measurements from the left wing landing gear location on my rc airplane wing. I would use this to locate the holes for my right wing landing gear location.
Please see Video For Detailed Instructions on how to mount Robart Retracts in your own radio controlled airplane.
How To Determine The Location Of The Retractable Landing Gear Mounting Plate.
In Part 1 we covered how to properly measure the best location for landing gear mounting plate holes in your rc airplanes wing.
In this tutorial, we will cover proper set up for drilling those robart retracts landing gear holes. Many times, I get asked, why does it matter when it comes to drilling holes? Well, the simple answer is, you don't want your piece ripped apart by a drill do you? That is exactly what happens if you do not understand proper drilling techniques.
Level Your Radio Control Airplane Wing Before Drilling Landing Gear Rails
Now that the holes have been marked and laid out on the landing gear rails it was time to level the wing (specifically the landing gear rail surfaces) in preparation for drilling accurate holes. It is important to always take the time to set up your work surface before doing any drilling, you will be rewarded with a great looking scale rc airplane if you take the time to set up first.
I used padded shims to help level the wing. I placed these under the trailing edge and wing tip of my plane. You can simply use rags or any other soft material to shim your wing, just make sure it is soft and won't dent your balsa sheeting that you created with such care.
Watch The Video To Learn More….
Now that the holes have been countersunk and made ready for a clean flush mount in my rc plane's wing, it is time to decide where to place the landing gear on the landing gear rails and drill the holes for the monting plate.
The placement of the landing gear depends greatly on the location of the landing gear rails, which will absorb the energy from hard landings (they happen you know). In this case, the landing gear will be place over a double ply rib that is reiforced with a bass wood block for extra strength.
With this in mind, I know that the landing gear should be placed somewhere in the vicinity of this location, but I found that the plans did not agree with my actual robart retracts, which meant I needed to create a mock up to simulate what the landing gear would look like and help determine if there was enough clearance to place it where it needed to be.
When it comes to installing retracts in your rc airplane wing, you may find that your actual retracts do not measure the same as your plans may call for. This was the case with my BeechCraft Bonanza when it came time to layout the mounting plate location in the left wing.
Instead of trying to make due with what I had, I decided to come up with a simple mock up of the balsa sheeting around the landing gear. This simulation made it very easy to determine where my mounting plate should be located, regardless of what the plans called for.
It is important to respect the overall position that is recommended on your plans, especially when it comes to heavier components that can effect the CG (center of gravity) of your rc aircraft. You will see in the video below that I discuss this point out the importance of keeping the structural integrity of the mounting location in mind when laying out its location.
Now, I would not recommend disregarding the plans completely, but I have found that if you think about where components should go in a rc plane wing, or any other part for that matter, it will become second nature to you to find a better solution or improve what the manufacturer provided.
When you think of the term modify it can make a lot of people cringe, after all, you are changing something that the manufacturer thought was a good enough design to sell it. I believe that this is part of what makes building rc airplanes so much fun. In fact, I purposely modify a lot of components to fit the way that I believe they should be.
There is a lot of times when I have disagreed with the plans and instructions that come with a balsa kit, maybe that is why some guys like to scratch build and have complete control over the whole thing (maybe it's a control issue, probably should get that checked ).
Seriously though, don't think that there is one way to build a rc plane, I believe in questioning the process and seeing if there is a better way to do it, such as countersinking the holes of a mounting plate for retractable landing gear. Look at my picture below (and video) to get a better idea of what I am talking about.
Watch the video to see an in depth explanation and drilling demonstration in action. This is how I modify landing gear (maybe it is a simple modification, but its the little stuff that makes a big difference in the end when it comes to building rc planes).
Now That I have discussed the basic layout and components of my landing gear retract system. I am going to prepare the wood rails that will hold the landing gear in place. This will consist of several steps that will comprise the proper installation of the landing gear rails.
Landing Gear Rails
The following video will show you how I modified my landing gear rails in preparation for the installation of the retracts. I felt that it needed a clearance slot to accomodate the air ports located on the side of each retract air cylinder, you will see how I modified this as well.
Pay close attention to the ways in which I modified the ribs to make room for the retracts. You will notice that I like to keep my sharp corners to a minimum and use a nice round sander to eliminate the sharp edges. Thanks for watching.
Steps to Prepare Landing Gear Rails for Retracts
If you are installing landing gear that is driven by air, then you will need to install retracts in the wings and nose or tail. This means that there has to be a means to mount the gear to the airplane in a secure fashion. In the case of this model airplane, I am using plywood rails that will be epoxied into the wings of my rc plane and then drilled to accomodate the screws for the mouning plates of the retracts themselves.
The steps to prepare the rails are like any other part of your rc plane, measure the part and cut it to length. The landing gear rails for my scale rc airplane are no different. I am going to show you how I sanded, cut and made changes to the landing gear rails so that they would accomodate the robart retracts.
As you may or may not see in the pictures below, the air ports on the sides of the air cylinders for the retracts are sticking out beyond the cylinder and will need some help. I fixed this problem by marking the rails where the air ports contacted them. I then proceeded to remove the material from the landing gear rails where I had just marked them.
Right and Left Landing Gear Retracts installed in their repsective wings in my rc airplane. I am marking with a pencil the area around the air ports and will remove this material from the landing gear rails.
Next I cut out the marks I made on the landing gear rails and sanded them smooth with a homemade tubular sanding tool. This was a quick and easy step, but an important one when it came to creating the best scenario for installation and removal of the landing gear.
Using an X-Acto knife and tubular sander (basically a plastic pushrod with adhesive sprayed sand paper rolled around it) I finished up the slots that would give the air ports the clearance they need for installation.
Now it was time to re-install the landing gear rails back in the wings and test the clearance slots for the air ports. If you are wondering about where to put your landing gear to make sure you have clearance, you will find that your building plans will show you an approximation of where to locate the landing gear in the wing.
You just need to make a visual check and verify that it is approximately in the right place. We are more concerned with the landing gear even installing without hitting those air ports at this point.
With the air port clearance issue taken care of I wanted to finish up the issue of the clearance within the rib bays that the air cylinder would be going through when the gear is in place. This meant cutting and sanding the lightning holes in the rib to make room for the air cylinder.
As with most rc airplane construction, it is necessary to make adjustments to the parts, this does not mean that you did something wrong, it typically means that maybe a part was warped, or the building plans were off a little bit, or the die cut part was not aligned properly when it was punched out.
Whatever the case may be, be prepared to modify your rc airplane from the get go and you won't be caught off guard. It is part of building rc airplanes.
Ok, back to the modification of the rib to make room for the air cylinder, I placed the gear back in the wing and could see that the cylinder was not going to clear the hole in the rib, no problem though. I marked the rib where it would need to be cut and sanded and removed the retract and began cutting the rib with my x-acto knife. You can see this hacking in the picture below (also check the video for a more thorough explanation)
After completeing the rough cuts of the opening in the rib, I finished up the job with my round sanding tool. This is a useful tool for getting in hard to reach areas and sanding a rough cut smooth.
It is always important to try and remove sharp corners for two reasons. One, you don't want to catch your self on it and get cut or a splinter. Two, you always eliminate stress points by rounding out any jagged or rough edges. No stress, means no failure.
Finally, I placed the landing gear robart retracts back in the wing of my bonanza rc plane wing and tested the fit. Surprise, everything fit well after the first try. Typically I must say that I usually have to cut, sand and test fit several times before I am satisifed with the fit, so don't think that this is typical of rc airplane builds. Always test fit and then take a little more off, then test again. Better safe than sorry right?
I am satisfied with the fit and can move on to epoxying the landing gear rails in place. This will be the next steps and will be included in my next post, epoxy those rails.
In the previous post I had finished setting up the landing gear rails to prepare them for gluing. In this post I will be epoxying the landing gear rails into the wing of my bonanza rc airplane. Whenever you are going to glue any part in your rc model plane you need to be very sure that you have made everything fit and any parts that need to be installed will go in easily before you permanately glue in your parts.
Video: Using Epoxy To Glue Landing Gear Rails Plus a Bonus Tip on How To Remove Epoxy.
Let's Glue Those Landing Gear Rails Already
As with any rc airplane project, I always clean up my building area before starting on the next component, this removes clutter and helps me think more clearly. You can choose to follow this tip if you like, it's up to you. I know for me if I clean up before the next steps, I can really see the overall picture better too, but that is just me.
When it comes to using epoxy, you want to make sure, really sure that the rc airplane part you are about to glue has been checked and re-checked. Now that my work area is clean, I went and got my epoxy for this job.
Now to get gluing! I use a piece of wax paper and begin pouring out equal amounts of the resin and hardener (if you are not familiar with epoxy, it consists of 2 components, a resin and a hardener, when mixed together it starts a chemical reaction and the glue begins to get warm and the curing process has begun).
In most cases, most newbie's will mix too much epoxy and waste it. Instead, I always mix a smaller amount, and if I need more, it takes no time to mix another batch. This is also a good reason to use 15 or even 30 minute epoxy, you will have more time to figure it all out and not feel rushed.
Now that the glue is mixed, take the forward landing gear rail and only apply glue to the points where it will contact the ribs. Try not to apply too much glue so that is does not drip.
You can use a cheap acid mixing brush to apply epoxy, it works quite well. You can get these at auto parts stores.
After the glue is applied, it is time to place the landing gear rail back in the wing ribs exactly as it was removed. I like to mark my parts so that I know where they went and I don't have to think about it (a simple top or a few marks on one side is all it takes).
I always make sure that the joints of my glued parts look completely covered in glue before I move on to the next gluing job
Satisfied with the first landing gear rail, I apply glue to the next landing gear rail where it too will touch the ribs in the wing, and set it in place. I check it over to make sure all joints are covered with glue. Now is a good time to clean up any excess glue that may have started oozing down the side of the ribs.
I use a piece of wax paper to clean up all the excess glue. Try to remove as much extra glue as you can, it does nothing for strength, it will only add needless weight to your finished model, which we do not want.
Before the glue sets, I clamp all the rails in place. I also add a piece of wax paper between my clamp and the glued part. Nothing worse than gluing your clamps to your parts and trying to pry them apart. Now all that is left to do is wait for the glue to dry.
I like to wait 24 hours before I remove my clamps and start working on the rc airplane parts that I just glued. This is because epoxy does take time to fully cure. Yes, it dries in about 15 to 30 minutes, but the full cure time really is 12 to 24 hours, depending on your humidity level.
Well, the glue has dried and I can remove the clamps from the landing gear rails. It is always a pleasure to see my rc airplane come together and see all the parts work together to create a working model. Thanks to the wax paper that I put between the clamps and the glued parts, they come off nice and easy.
You can see in the pictures below that the wings landing gear rails are now glued in place and all that is left to finish the rails is a little sanding to make them flush with the ribs. I use a homemade sanding block, it was made from a scrap piece of 1/4 inch plywwod and I use spray on adhesive with the sand paper to make it stick (I used 100 grit to sand the rails flush).
In this post I am finally getting around to installing the Robart retracts for my rc airplanes landing gear. You will notice that the Robart retract is highly detailed with many scale features which will add to the scale realism of my beechcraft bonanza. First I thought it might be important to go over all the parts of retractable landing gear, in case some of you needed more specific information to understand how they work.
Let's go over how the Robart retracts work and what the parts of a retractable landing gear system entail – followed by the first steps to preparing the landing gear rails for installation.
In the following video you will see how an introduction to the Robart retracts and how to prepare the plywood landing gear rails for installation by cutting them to length and sand them and the ribs to fit properly.
Robart Retracts – These are the biggest component to the landing gear system. For this rc aircraft, I need three. Each Retract consists of a mounting plate to secure to the wing and nose of the plane. Each retract is made up of an air cylinder and piston that are actuated by air pressure. The landing gear uses a cam pin and cam follower to guide the retract and lock it in place when extended and retracted. These are very scale landing gear and even have spring shocks for the strut and and an oleo strut for the axle.
Look at the photo below to get an idea of how the retract looks and what each component of the gear look like as well. You can see the mounting plate, strut, wheel and air cylinder.
Air Tank Reservoir – An important part of the whole system. It will store the compressed air which will power the cylinders, which in turn will drive the piston to actuate the landing gear itself.
Air Line – This is flexible plastic tubing that is color coded for routing your air lines. It comes in 2 colors, red and purple. I will be using the red tubing for routing to the air port on the landing gear air port that extends the gear. The purple air line will be used for routing the air line for the landing gear retract air port.
Air Pressure Gauge – This is a handy device which shows you the level of air pressure in the air tank reservoir. If you will be utilizing a pneumatic landing gear system you might want to consider purchasing this device as it will provide a bit of insurance as to how much air pressure is in your tank. Not a bad idea when you can make a quick visual check and know whether or not you need to add air to your tank. This device will be hooked up between the air tank and your landing gear cylinders.
Speed Control Valve - An important part of the overall system. This will control the level of air that goes to the landing gear and how quickly or slowly the gear will retract and extend from the rc plane. Typically this consists of two valves to control the rate of air, also as part of the system it contains 3 air ports that the air lines will hook up to. These will be controlled by a plunger or spool that will be cycled by a servo and initiate the actuation of the landing gear cylinders.
Fill Valve and Fill Chuck – The fill valve is a one way valve that will be a part of the over all air line system. It is going to be connected through a tee. Later it will be mounted on the fuselage and the fill chuck will attach to it and fill up the air cylinder. The Fill Chuck is going to be part of the air pump and will attach to the fill valve when the air tank needs filling.
Retaining Rings and Tee Fittings – These components are what will be used to route the air lines cleanly and logically from the fuselage to the wings and landing gear air ports for the nose landing gear and wing landing gear respectively. The retaining nuts are the aluminum knurled parts shown below. The tee fittings are the red and black plastic parts shown below.
This is all the components that will be used to hook up the air system for the landing gear. I am going to be starting with installing the retracts in the wings of my radio controlled airplane. I will continue to create a series of step by step videos that details the installation of all these components. I have looked all over and there is no real books or videos on any of these parts, so that is why I decided to put this together.
The Next Steps
In my next post I will be completing the installation of the landing gear rails by gluing them into the wing. I am going to include some useful tips when it comes to gluing, so stay tuned for the video too.
Let me know what you think of all of these videos and detailed tips. Thanks for reading and watching.
At this point I am ready to build the center section and add the balsa sheeting to the wing of my radio control plane, making balsa sheeting is easy when you follow a few simple rules. You can see the steps for this in the balsa sheeting post. Creating proper balsa sheets is one of the most important steps when it comes to a professional looking sheeting job.
Completing Center Section
As you can see here, I begin with an important step with any rc model plane…setting up the structure and aligning the parts perfectly to the plans. As always, I use a magnetic building board to build all my rc airplanes from scratch. If you get the alignment and layout right for your wing center section, then you will be buildnig like a pro too. Using a square and magnetic vises, I hold the center section to my sheet metal board.
After confirming the alignment of the ribs, I can continue to add more magnets to hold the rest of the wing center section in place.