Last evening and today were busy getting the plans taped together, doing some measuring, drawing and even quite a bit of math...brain is tired now!😖 I think I have the vast majority of the work done to satisfy my planned modifications, so it will be much easier to start cutting foam and get building😊
I'll try to keep this organized and explain in detail what I did as well as why and how I did it, so this will be a bit of a lengthy post, but should be lots of pictures for distraction😉 Either way, you might want to grab a snack and a beverage, or read it in small chunks! This is normally the longest part of the build process for me when I am doing several mods on a plane, lots of measuring, figuring, drawing, redrawing, etc, but once I am happy with it, the rest goes along a lot quicker and smoother😊
I'll start with the wing plate since that is the most detailed and required the most measuring and drawing to accommodate my planned modifications.
One of the things common to all the V5s I have built is the wing plate is in two separate identical pieces. I prefer to tape these together first before putting them on the foam and cutting, especially if I am going to make modifications as you can see above in this picture. I have roughly laid out my carbon reinforcement ahead and behind the prop slot and along the elevon hinge line. One main difference between this and the F-22 is that she has a little extra "junk in the trunk" behind the wing as it is much wider than the F-22 V5.
In this current size, while I could lay it down on a 20x30" sheet of Dollar Tree foam (DTF) to get the 27" wingspan in one piece, it is far too long and needs to be cut in a couple of spots. I chose to draw lines here in front where the LERX (leading edge root extension starts to angle back more dramatically. This piece will get glued back to the main wing plate at a later point in the build once other things have been completed with the main wing plate.
In the rear, it made sense to cut off the elevons as I will be making those out of Depron anyway.
This will leave me with a main wing plate piece that is about 19" long, so easy to fit across the 20" width of a full sheet of DTF and have that all one piece.
Motor mount/prop slot mod, etc
As I mentioned in part 1 of this series, one of the mods I will make is to move the motor further forward by 1", primarily to compensate for the weight of the paper on the DTF behind the trailing edge of the KF and also hopefully to help the plane be more balanced and rotate more easily in all three axes.
There is a lot going on in this picture above, so I'll try to make sense of it. Originally, when I drew the sides of the prop slot, I had forgotten to widen it out so that it will be even with the outside parts of the "engines/nacelles" underneath. The black dashed "-" lines indicate where that will be, drawn by lining up the slots fore and aft on the wing plate to see where those will be. The lines that are "squiggled" out in black were my original lines and it made for a very narrow prop slot, maybe 6 and 3/8" which caused me to remember I could widen it out.
Hopefully you can see where I moved the motor mount forward 1" and also trimmed 3/8" off the leading edge of the prop slot to accommodate shorter quad racing motors. I always like the back of my prop slots to be a straight line, so drew that in accordingly. Gives my prop lots of room to "breathe" and perhaps it is not aesthetically pleasing, but hopefully gives me best performance from my prop and motor.
You can see where I put my carbon ahead of the motor mount, I will be using a piece of 3mm carbon tube as shown below. It is recycled out of a previous plane, so I need to remove the foam and glue residue before it goes into this plane. If you look to the right of the motor mount area below the carbon tube, I have drawn a small 1/4" square, this will accept a 1/4" tab from the top of the fuselage. I made this change so that nothing would interfere with the carbon tube, it is primarily for alignment of the top of the fuselage, not for strength, so should be adequate. If you look at the far right, I also modified the slot that will accept one of the tabs on the "engines/nacelles" to accomplish the same thing. I will place the carbon tube so that it runs right through the dead center of the "CG spectrum" that RC Powers puts on their V5s. This way I know that where this tube is will be my starting CG point for the maiden flight.
Reinforcement of the wing plate
As you can see in this group of pictures, I will be using carbon to reinforce the wing plate in three areas, a 13" piece of 3mm carbon tube ahead of the prop slot as shown above. I'm hoping that since this will be "locked in" under the KF4 airfoils it will give sufficient strength without adding the extra weight of 4mm carbon rod. Plus I already had a piece that fit perfectly recycled from another plane😉
For the main wing spar, I am using a 25 and 1/2" piece of 4mm carbon rod for maximum strength across the widest part of the wing, again, this piece was recycled from another plane, glue and foam residue need to be removed.
On the back plate ahead of the elevon hinge line, I am using a 15 and 1/2" piece of 3mm carbon tube. Since the "nacelles/engines" don't extend all the way back due to the unique "under rudders" of the T-50 and it is pretty wide back there, I wanted extra strength to prevent torsional twist caused by the elevons.
Aileron mod
Like I did with the F-22 V5, I wanted to increase the size of the ailerons. Due to the width of the back end of the T-50, the trailing edge of the wing is not that long, only 17.5 cm. I "showed my work" as you can see, 60% of 17.5 is about 10.5 cm which is what I used for the span and I increased the depth/chord to hopefully have enough control surface area for the ailerons to be effective. Of note, I find it easier to use metric when I need to take percentages of things or work out ratios. Just much easier for me when things are all based on 10 or decimals of 10 than percentages of inches😃 Although I'm still a bit "old school" and use inches when it suits me😉
Elevon mod
As I mentioned in Part 1, I wanted to add the "boom" to the center of the elevons not only for scale looks, but to add a bit more surface area to the fairly tiny stock elevon surface.
I borrowed from the NAMC Mig-FA a concept stealth plane my NAMC partner Stephan designed and I helped with the test and validation phase. Plans are free at the link or you can e-mail me at scott.parkjet@gmail.com and I can send you the PDF files. It is a concept plane based on the T-50 with a 27" wingspan, so these worked out pretty well I think and will hopefully add more authority to the elevons and a bit more "cool factor" to my plane😎
Mods to the nacelles/engines
Since I moved the motor ahead by 1" and will be using a shorter quad racing motor, I needed to trim the back of the nacelles so that they wouldn't interfere with the prop.
Also, I modified the tab where it will go into the slot I already modified on the wing plate.
I will not be putting my servos in the indicated locations. I will have to put my rudder servos behind the prop slot due to the "under rudders", my aileron and elevon servos will go as far forward as I can get them to shift more weight forward of the CG.
Fuselage modifications
Again, due to the movement of the motor and mod of the prop slot, the fuselage also needed to be adjusted. Back of the hatch to the electronics bay shorted 1 and 3/8" inches to avoid interference with the prop slot.
On the fuselage, I moved the center where the motor mount supports go forward 1" and the top piece of the fuselage 1 and 3/8" so as not to interfere with the prop slot. You can also see where the pencil is pointing I modified the tabs to fit into the slots I modified on the wing plate.
KF airfoil modification
Normally if I am going to modify a KF airfoil, I will cut one from the plans out of scrap foam. I always like to start with the top as once I get that sorted, I can easily make another of proper size and then size the bottoms ones later on (I will show how I do this later in the build process).
I will then trace it out on the wing plate plans so that I have some reference to work with to start measuring and calculating, shown highlighted in yellow below. This actually shows the final size of my KF after all my math, but hopefully you get the idea😉
So this next part might be a little difficult to follow, I'm kind of "winging it" (pardon the horrible pun 😏), but I think it should work. The T-50 has a very unique wing shape so I had to make some compromises.
I started off measuring the rough chord of the wing where it would be meeting the fuselage. You will note in the picture above, I don't factor in the extra bit that goes forward over the LERX (leading edge root extension)/intakes.
I also didn't factor this little bit into the wing chord, the triangular area roughly marked in blue
Where you see the metal straight edge in this picture is essentially where I marked the trailing edge of the wing.
So measuring from the top point of the KF to where my "trailing edge" is (indicated by the blue arrow), this measures 40 cm. Since I like to have 40% of chord at the wing root on my KFs, 40 x .4 = 16cm, hence why in the picture of the KF above I have marked to add 1 cm when I cut out my own.
The RCP ones were very close and fortunately the trailing edge of the KF is right on my modified prop slot leading edge.
At the wing tip, I also had to do a bit of compromising. The very tip of the wing is actually quite narrow on the T-50, so if I took 35% of that, I feared my KF might be too narrow at the wing tip to function the way I want. So I measured the very wing tip at 4.5 cm, then drew the blue line where the tip of the wing area is a bit wider (10 cm), took the average of those at 7.5 x 0.35 = approx 2.5 cm which luckily enough is what the stock measurement is on the RCP plans, so I'll go with that.😊
As mentioned earlier, once I get the wing plate cut out of foam, I will demonstrate how I draw out the rest of the top KF and then size the bottom KF so that they will be proportional on the wing.
Vertical stab modification
Again, I hope my math and methodology make sense here on how I modified my vertical stab, I used a little bit of math and some "artistic licence", but I think/hope the final product will look good and be functional. Looking at the current vertical stabs, they looked too much like those on the F-22 and not like those on the T-50 for my liking. I wanted mine to have the more unique angle and proportional size that I see in this diagram.
Having the plans to the RC Powers T-50 V1 from a long way back (unfortunately no longer available), I printed off one from those plans as a starting point. I like the more scale size and shape of this stab.
So I started playing around with a few numbers knowing to match a 27" wingspan, the V1 stab would have to be about 13% bigger. Then looking at the current size of the stock V5 stabs, I took an average of that, mixed in a little "artistic licence" on what I thought looked good and came up with the dimensions below using the same angles as on the V1 stab. I estimate I have reduced the overall size by maybe 10-15% and made it look what I hope I will be a bit more scale, we will see. I will cut out an extra one when I build the plane to have as a template for later builds in the event this works😊
Motor shims
This last part really has nothing to do with the mods, more of a big lesson learned or word of caution. In the V5 series of planes, RC Powers came up with the idea of using foam motor shims to adjust the motor location to make it easier to balance the plane (I "think" that is what the logic is anyway😐), if you watch this video at about 0:50, you will hopefully see what I mean.
I tried this when I built my first V5, the Su-27 and I found these foam shims to be a significant point of failure. When I would epoxy my wooden motor mount to the flat face of the shim, over time, they would rip apart, the epoxy actually pulling a thin layer of foam off with it as this is not a strong bonding method for the epoxy.
I brought this to RC Powers' attention via e-mail, however it was not really addressed, fair enough, their designs. However, from my personal experience, I would steer clear of using these foam shims on any of your V5 planes lest you risk your motor coming off in the air or you could end up having to continually glue it back on over time creating hassle for you and more weight to your plane😒
Well, hopefully you are still with me, follow on installments of this build log should be much shorter and less detailed...fingers crossed!
Park Jet noise...the "other" sound of freedom😎
Cheers,
Scott
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