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Scratch Build-Off - FPRC F6F Hellcat

Snarls

Gravity Tester
Mentor
#1
Most of my RC interests these days stem from multirotors, but my early days in the hobby involved planes. I have built and flown numerous foam board planes. Never have I done a detailed scale build. I have wanted to fly an F6F Hellcat for a while now as it is the plane my grandfather flew in WW2. I am fairly busy so I did not want to go full scratch build with this one. Instead I am going to use plans from Flying Penguin RC, and then spend some time adding extra details where I want it.


Hellcats_F6F-3,_May_1943.jpg

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(Photo from FPRC article)

I am hoping to have a lot of fun with this build.

[HR][/HR]

Build Progress Photos:

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Please Tolerate My Poor Knowledge of Scratch Building Terms and Part Names
 
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wilmracer

I build things that fly (sometimes)
Mentor
#2
Love it. The F6F is one of my favorite warbirds. Simple lines, but an absolute beast. Good luck with the build!
 

nerdnic

nerdnic.com
Mentor
#3
I've had these plans printed since the day they were posted. Haven't ever gotten around to building it though, so I'll be watching!
 

Snarls

Gravity Tester
Mentor
#4
Thanks guys! Hopefully you can build vicariously through my pictures. I will be painting it like the first picture, not how FPRC has his. I also have some retracts sitting around so I might get fancy if I'm feeling it.
 

Snarls

Gravity Tester
Mentor
#6
Update: I have printed out a fat stack of plans, the most pages of plans I have ever printed. I decided to go with 80% scale to save some paper and hopefully allow me to use one the motors I already own.

I am thinking about using Peter's minwax and craft paper technique to reinforce things and possibly add some more curvature. FPRC does say the f6f is a heavier build so I am concerned slightly about weight.
 

willsonman

Builder Extraordinare
Mentor
#7
Use tissue instead of brown paper. Same effect... stiffens things up and provides ding protection. Its not as durable as brown paper so you will have to be less careless but it works wonders. If the wrinkling is too bad, you can use OBPU instead of WBPU. You can also try nicer tissue paper, it tends not to wrinkle as bad.
 

Snarls

Gravity Tester
Mentor
#9
Use tissue instead of brown paper. Same effect... stiffens things up and provides ding protection.
Thanks I will try that.

So... what is the span here? I'm not familiar with the Penguin designs but it looks nice!
I actually do not know. It's not in the article or on the plans. From the pictures I could tell it was larger than I wanted so that's why I scaled it down to 80%.
 

Snarls

Gravity Tester
Mentor
#10
Progress is being made! I taped up all the tiled sheets into large plans to roll up. I ended up with five rolls and several separate sheets for additional poster board pieces. Using a window and the markers that the printer makes when you tile plans really helped line things up.

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Next I took the rolls and used some locktite spray adhesive to temporarily bond the plans to the foam board. This was actually easier than I had anticipated. With five rolls I thought I would need five pieces of foamboard, but with some trimming and strategic positioning I ended up only using four boards with scrap to spare. Now it's off to cutting the pieces out which I am not looking forward too. If only I had a laser cutter :p. I will also have to refer to the plans online to check the line colors because I printed in black and white. Right now it is looking to be about the size of the FT3D, maybe slightly smaller.

plans2.jpg
 

Snarls

Gravity Tester
Mentor
#11
Continuing on with the build I started and finished cutting out all the pieces. It was actually quicker than I thought, although some of the pieces are much more intricate than what I've seen in FT builds. A nice sharp blade went a long way. I also took a look at the plans and added color to my black and white plans so I could tell when to score vs cut.

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Following along with the build instructions of FPRC's article, I assembled the internals of the fuselage. I forgot that my plans where scaled to 80% so some of the slots to join the pieces were a little tight. At this point the build seemed weak and flexible and I was unsure how the rest would turn out.

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I decided to strip the paper off some of the long pieces. This turned out to be a bad idea as the long pieces, which define the shape of the fuselage, were easily bent. This problem was easily fixed later when the skin was added to the fuselage.

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The pieces of foam board to skin the back of the fuselage has a lot of 50% cuts to get the proper shape. I quickly found that going over the 50% cuts with the end of a small flat head screwdriver really helped the piece bend into shape easier.

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Next the foam skinning was glued to the back of the internal framework. This took multiple glue and forming sessions, working from the bottom to the top as per FPRC's instructions.

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The skin for the front of the internal framework was applied in much the same way as the back, using two separate pieces. For the midsection the foam has markings where the wing will attach, but there is no actual cut out yet. I assume this is to preserve the strength of the foam as you wrap it around the internal frame. Once the foam is attached you can cut out the hole for the wing.

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Inside there is still plenty of space to route wiring and fit a battery and ESC. The framing has holes cut out to fit the FPRC powerpod, but I decided to just mount a firewall to the front.

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The control rods were actually added before I finished skinning the fuselage. I actually recommend putting in the control rods for rudder and elevator as soon as the internal framework is built.

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The front cowling shape involves some interesting geometry. It is a bit of a pain to glue in, but not as difficult as it looks. I will clean it up more when I cover the plane with tissue paper and minwax later.

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This sums up the construction of the fuselage. It actually was a very quick build. Compared to what I thought earlier about the framework being weak and flexible, the skinned fuselage feels very strong and rigid. Next up I will work on the wings.
 

Snarls

Gravity Tester
Mentor
#12
This portion of the build involves the wings, specifically the inner wing sections and the outer wing sections. Both use similar techniques to construct.

The inner wing section involves multiple 50% cuts to achieve the proper curvature for the wing. There are two ribs that go in to this part of the wing, with a two foam board thick par in between. To get a sharp trailing edge the ends of the foam board are sanded down. This did not take a long time to do using low grit sandpaper to approximate and high grit to finalize the shape.

There are no electronics in this section of the wing on the FPRC build, but this is where the landing gear goes on the real thing. I have some retracts laying around from my old AP multirotor build. They do seem a bit small for this build, but I will still try to use them. There is one problem I am having. The wheels on the real F6F fit into the wing along a line parallel to the ribs, with the face of the wheel parallel to the bottom face of the wing. With my retracts getting the wheels to line up would only be possible if the length of the retract was perpendicular to the ribs. Otherwise I will have to find a way to rotate the wheels 90 degrees as the retracts. Suggestions are appreciated.

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The rest of the inner wing section is on hold as I decide what to do about the retracts. Next up then is the outer wing section. Once again the edges are sanded to get a sharp trailing edge. Like the inner section there are once again 50% cuts to achieve the curvature of the wing.

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There are also two ribs in this portion of the wing. The spar is a single foam board thick piece. The servo is positioned as shown. Using 80% scale the little 9g servo barely fits.

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The face of the wing piece was actually cut to fit the servo. This allows for the servo to removed or serviced without having to cut it out of the wing. A piece of poster board will cover up the hole when the servo is in place. To hold the servo in the wing I build a little housing for it. It is just made out of scrap foam to fit the size of my servos.

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FPRC recommends making another sanded trailing edge to glue right above the ones from the plans. This is so when you cut out the ailerons later, there is no gap in between the foam that was folded on to itself.

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The wings are then glues together a little bit at a time. One 50% cut is filled with hot glue, the desired shape is achieved, then the next cut is glued and repeat.

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Finally the ailerons are cut out of the trailing edge of the wing. FPRC includes aileron cutting guides in his plans which really helped. The ailerons are beveled simply using an angled cut. I decided to bevel the ailerons on the bottom of the wing rather than the top to give it a cleaning look from the top side. As of now the ends of the wings are open. When covering the build with tissue paper and minwax I will probably fill the end in and round it a little more.

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This almost concludes the construction of the wing. I sill have to work out the retract system. Then the inner and outer wing sections have to be glued together at an angle. After than it is time to work on the control surfaces in the back.
 

willsonman

Builder Extraordinare
Mentor
#13
you will find that foam without paper is quite flimsy... until you glue a bunch of it together. See the J-22 Build in my signature. I know all about it.
 

wilmracer

I build things that fly (sometimes)
Mentor
#14

unrauv

Active member
#15
A double wood spar box design works very well. Check out my designs. You can key the gear supports into the spars, you will have to do a joining spar.