Winter Build 2018/19: Hangar 9 P-47D Razorback

[willsonman]

OK, one gear door completed. I screwed in the servo and started playing with a length of push rod that was an approximation. I used tape to hold the hinge in place. After settling on a location for the horn on the door, I finalized the push rod and it was done. The cool part is that I do not have to use any end points... this means that that any other thing on this channel (like the landing light, perhaps), gets its full travel as well. So far in this build, I've managed to mechanically design each part this way so I do not have to program much in the radio.


I then took a little time to program the radio... first I had to test-fit the wing in order to plug everything in... Another first. I had to trim the opening hole in the fuselage. That obstruction you see in the hole is the resonating balsa from the sound system.


Once I knew the wing would fit, I slipped in the aluminum spar and began fishing all 6 of the servo lines up the printed guide tube. Let me tell you... this part works AMAZINGLY well. It was easy. Like, REALLY easy. So after I got the wing roughly in place I started testing the landing gear first, and then the door separately, so I could get the sequence programmed in the radio. Then I got them both working together and adjusted the timing of the inner door. This setup works like butter. I'm super happy with it. I also grabbed a shot of the wires snaked through the printed guide. Plenty of room for the two more lines I will need in this wing.

 

[struggleforlife]

Another question.
My wing and gear well. Please see pic below.
Did you cut the 2nd rib out (counting from root)? Because I was unsure if this was 'harmless'.....

 

[willsonman]

Again... these are different airplanes. They are not the same. There was no inner rib on mine at all.

 

[struggleforlife]

I am probably not using the correct word 'rib'...

This 'thing' with the arrow I mean.

 

[willsonman]

No, that's a rib... did not have it. Please reference post # 174 pictures. The 2nd image you see there is with the skin and ply beneath removed. No modification. There was a small piece aft of the leading edge but that is all. That was simply cut away. No full rib like yours looks to be.

 

[wilmracer]

You're using the right term... that would be a wing rib. The wing design must have been changed between the generation of models and the current model doesn't have a rib in that location. On the current model there is a plastic wheel well that fills most of this area that willsonman has removed so he could make everything more scale. If you are looking to do a similar mod to your jug I think you would be safe widening the opening in that rib to accommodate a servo. I would not expect that to have a significant impact to the strength of the wing.

FWIW, even if there HAD been a rib there that willsonman removed... he will be glassing this wing, which will add a LOT of strength in the skin. Structurally he will be just fine.

 

[willsonman]

To make things crystal clear, I took this succession of shots to show the removal of wood for the inner door. First the balsa was cut away and removed from the top of the ply.


Then the ply was cut while leaving a lip for the glass to rest on when closed. Not that there was some rib material exposed here that is removed...


...in this shot. The hole was cleaned up with the dremel and is ready for the door.


That all said, the other door is installed and functional. There is some additional work I need to do to make it complete but I’ll cover that in my next post.

 

[willsonman]

Quite a few things to cover in my post today so let's get started.

With both inner gear doors now installed and functional, I need to wrap up a few minor details. One is pictured below. The very edge of the main gear doors gets a lip of 1/64" ply. This will be further sanded back as it serves only one purpose and it is over-sized for that. In my days I've observed too many times and had personal experience with any sort of door that you need to reduce gaps in doors. The reason being is that it is much like going down the highway in a car with ONE window open. The air pressure finds the resonant frequency of your car at a specific speed and it sounds like your head is about to explode. This lip I installed prevents air from resonating inside the airplane which can cause a door to want to stay open. This is due to an overly positive pressure. By reducing the amount of gap available for air to enter you effectively eliminate this. I've seen folks make a maneuver with a funny sound and then a door pops open on so many occasions. Then, what typically happens, is the gear goes down and the door servo has failed or the linkage is broken. A couple of grams of prevention here, folks.


So, the first gear door (main) still needs some additional love in the oven. I need to start, in earnest, treating my parts with the acetone vapor bath. I've tested one part and it did not go the way I anticipated. I had vapor condense back onto the tray with the part on it and turned things a little stickier than I wanted. Good thing I used a test print for that. I should put some threadlock on threads on the gear but I'm not too concerned about that. I will need to go over every square inch of this bird when she is ready to fly. I got some additional wiring work done. The light controller for the navigation lights needed to be installed as well. The wires are quickly becoming a rat's nest... and the wings are not even plugged in.

I did start on some finish work last night. Remember that hatch modification? Yeah I had to correct some glass work on that. All better now. I got the wing hatches sealed up and I should be able to just slap on some foil and call it a day. Coming up soon on the foil tutorial. Stay tuned for that.

 

[willsonman]

So, way back on 24JAN I posted a list of things to get done. The only one left on that list is to glass the wings. I'll need to tape off the navigation light covers, remove the main gear doors, tape off the retract units and landing light all before I can do any glass work. While It may have seemed smarter to glass before I did all this installation, some of this would have had to be re-done anyway. Particularly the bottom of the wing once the holes were filled. Then all this work on the wing has been on the bottom so the top, had it been glassed, would likely have seen some rash. So, here we are.

The airplane is basically finishing itself at this point. Each piece of the concluding puzzle is directing that the next part be done in succession. I have some chromate green paint to shoot on interior areas before I foil. Paint masks need to be ordered. Cockpit interior and pilot need to be done. The canopy will go on last, for fairly obvious reasons. There are just little things now that have to be done before the next little thing.

 

[struggleforlife]

Well guys, I did my own version of the wheel well/gear door modification. After all: monkey see, monkey do.... I am pretty pleased with the result, even more so as this is my first mod of the kind. Nastiest job was the gear door itself (the glassing). The cutting was very do-able. And I made a few new ribs to make up for lost strength due to the cutting; the extra effect being a really neat bay. Final step will be the painting the bays in chromate green.

 

[willsonman]

Bravo! Looks like you know what you are doing... and a warning... mods like this are infectious. You do one and then the next thing you know, you have an entire airplane full of them.

 

[struggleforlife]

thanks. I have a few other mods going as we speak: tailwheel, intercooler, exhaust, cockpit and engine. Will update you when I have something good to show!

 

[willsonman]

Not much done last night. After a full day of work at home with the kids, the ankle and foot were quite swollen and I needed to elevate.

What I DID finish was the gear door that needed some love. I put it in the oven for 6 minutes... which was a bit too long. I had to work pretty fast as this was much softer than before. In the end I did get much better closure but I was terrified. With the door finally sorted I got the gap filled with 1/64" ply as was done on the other side.


I thought about getting preparations for paint work done but it required some moving around in the shop; something I did not want to do much of. So, I decided to apply some foil. These are just the servo hatches on the bottom of the wing. They need polished and some rivet work but I think you get the idea that flat parts are really easy and the default finish is quite reflective.

 

[SlingShot]

Which radio do you use?

 

[willsonman]

FrSky Horus X10S

 

[willsonman]

No picture progress but I have substantial progress to report. I spent an evening preparing the wings for glass by applying masking tape where needed and removing the main gear. The main doors were sanded and prepped for paint and aluminum. The gear bays will be shot with chromate green. I have a little something special planned for the tail gear bay. Some additional work was done on other parts in preparation for aluminum application.

The wings were also glassed last night. I got the top on first and let it cure out for a full hour. I trimmed the excess and then did the bottom in two sections. The pylon was the divider but no issues encountered. The application of the cloth with sanding sealer (SS) is really easy, low odor, easy cleanup, and dries fast. It can be accelerated by means of heat, such as a hair dryer. I have, in the past, observed that both water-based polyurethane (WBPU) and SS can warp balsa on the first application. For this reason, I use a light first coat of the stuff to seal the wood, dry with a hair dryer, let cure for at least one hour, then sand, and then apply the glass using SS or WBPU. I have come to find that SS is essentially a more concentrated form of WBPU and does dry faster since it has a bit less water content.

Further still, I've made significant progress on the cockpit modeling. Both side panels are nearly done and ready for test print but I want to be sure they are before I do. Again, the spirit of this model is that as-purchased it is a sport-scale ARF and I am building it out in a more scale way. Not purely scale but just adding details. The idea for the cockpit is to add some depth. The dash is a good start but the side panels need attention as well to really draw you in to look at those tiny details. I'll try to grab some screenshots from Fusion when I have the chance.

 

[rockyboy]

Any particular brand recommendations on the sanding sealer?

 

[willsonman]

Whatever is cheap.

 

[willsonman]

Left and right side panels for the cockpit. The instrument panel goes in the center of these two so you know the layout.

 

[AkimboGlueGuns]

Left and right side panels for the cockpit. The instrument panel goes in the center of these two so you know the layout.
View attachment 124641 View attachment 124642

I dig it. You're surpassing the Corsair in terms of scale awesomeness.