Steps to Prepare Landing Gear Rails for Retracts
Steps to Prepare Landing Gear Rails for Retracts
Step 1
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.
Step 2
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.
Step 3
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.
Step 4
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.