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Pumpkin drop event

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

rockyboy

Skill Collector
Mentor
That's looking spectacular! Are you doing anything special safety wise? I'm guessing you'll be spending a lot of time with the acetone on this project...
 

willsonman

Builder Extraordinare
Mentor
Well, my shop is pretty well-ventilated. It opens up into a large room and the home air return is just up the stairs. In reality, I'm using the acetone on a paper towel so I'm using a very small quantity at a time. As I wipe down the seams, I'm also cleaning the residue off the scissors and #11 blade at the same time. I'm trying to be mindful of all of the fumes but its really no worse than doing a layup of balsa and CA.
 

rockyboy

Skill Collector
Mentor
Well, my shop is pretty well-ventilated. It opens up into a large room and the home air return is just up the stairs. In reality, I'm using the acetone on a paper towel so I'm using a very small quantity at a time. As I wipe down the seams, I'm also cleaning the residue off the scissors and #11 blade at the same time. I'm trying to be mindful of all of the fumes but its really no worse than doing a layup of balsa and CA.
Good to know - I had this on my mind after doing ammonia spray on balsa to bend it this weekend and needed to use the low tech "keep the outside door open" for a while to air the shop out. Thought if anyone had a fancy scientific method of dealing with fumes it would be you :D
 
Ah, who doesn't love the smell of glue, acetone, terpentine, paint and Isopropyl!?

I made some progress.
1. Made the new firewall and new (very low and forward) battery location. Cut of the original firewall first and didn't use the standard motor mount 'box'.
2.Printed the @Willson Bomb drop mechanism, blew it up to 125%, constructed the pylons and glued them on. Used the orginal bombs, but removed the inner crap and closed the holes. The fins seem a bit fragile, so we'll see how that goes.
PS. I didn't cut a hole in the pylon to have the bomb mechanism stick through (like @willson did), I just cut 2 small holes for the hooks to stick through, and designed a new (slightly longer) bomb hook (to compensate for the wall thickness of the pylon).
3.After 16 designs and even more prints, I have finally come to a good fit (and final version) of the cowl air inlet. The cowl shape is incredibly complex, so it's very hard to 3d design a good fit. It's not glued in yet (have to construct the motor and pseudo engine first), but it fits like a glove (it's available on my thingiverse btw).

Besides some servo's, all thats really left to do is the motor and pseudo engine (which make for a extremely tight fit into the cowl). I didn't yet acquire all the electrical stuff (because it will set me back a fortune, and I sure as hell am not going to fly this airplane anytime soon!)
 

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willsonman

Builder Extraordinare
Mentor
Your progress looks good. I'm glad you were able to make use of my drop mechanism. While I understand your trepidation to fly this model, I've not seen a single P-47 that did NOT fly well. Get the CG right and she will be fine.

So, I'm gonna go through the covering steps today. I took sequential pictures so I'll try to explain everything. I'm likely to forget something as there is a lot involved. I hope that from this explanation that you all can grasp the amount of labor involved in this process.

First off, the part needs to be properly prepared... which I've covered previously. Then, the part needs to be clean. Keep your work space clean and be mindful of hard object within the vicinity of your work space. Note that I am using a microfiber cloth to work on. This is to prevent dings and scratches to the surfaces.

You have to first mark off your part with the panel lines. The lines will have an overlap but there is wiggle room here. I'm using true masking tape, not blue painter's tape. I need to see THROUGH the tape. The leading edge of this part is complex so it is easier to apply the masking tape and cut away tape that is not needed. The masking tape will create a ledge of sorts for a reference on where to cut the foil. Generally, on the full-scale subjects, panels are applied from the front to the back. So, I'm masking off the rear areas with the leading edge to be applied last.
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The first two panels of aluminum are applied. Note that there is a "grain" of sorts to the aluminum. You can play with this to replicate different view angles if you are going for a more in-use look. I'm going with an airshow look so I want things to be more or less consistent so the grain is maintained as much as possible. The panels are applied using a SOFT paper towel. I'm using Viva brand that has no quilting. A microfiber cloth will do as well but the aluminum will rub off and later can cause scratches on subsequent panels. I opted to have a disposable applicator of the paper towel for this reason. Note that you can see the panel lines and generally know where to cut. The trailing edge is also cut fairly close to the edge of the panel.
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Because your #11 blade WILL wander as you try to cut, I then crease the edges of the panel with the tip of a bamboo skewer. This creates a groove that will help guide your cut.
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Then we cut the panel along the grooves and remove the excess foil. The trailing edge is then burnished down with a hard wood tool. This allows the edge to be crisp while stretching the foil to the curvature of the edge. I also use the burnishing tool to seat the edges of the panels so that they do not get caught on anything and rip... sort of like a hangnail.
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The masking tape is moved (re-used) to different locations for additional panels. Note that the trim tab for this elevator is taped off and goes against what I previously stated about moving aft forward. This makes sense in this particular instance. When foil is applied this time, the crease is done at the edge of the tape again but it's tricky. The skewer can wander into the seam where the foil overlaps so you have to be careful and take your time.
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rinse and repeating the steps previous, you are left with a mostly completed panel. Note how the grain is all in the same direction here. The masking tape is removed and discarded next and new tape is applied. I then cut triangles to expose the edge for the overlap here.
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Note how the grain is different at the leading edge here. This provides slight contrast to accent this interesting visual. Once polished, a lot of the tooling will disappear. The leading edge was applied as two pieces for each side. Smaller pieces work out easier. These are not flat parts so NEVER assume that a single piece will work when more will work better. The other side of the part is done this same way and the trailing edge overlaps. I use tiny manicure scissors (old pair) to trim the edges of overlap. Large scissors are too clunky and lack the ability to get into the fine corners needed. The edges are then burnished down.
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From here, you need to let the adhesive cure out for at least 24 hours. The glue will harden a bit. I tried polishing and further processing of parts previously and it creates waves in the aluminum. You are better off being patient and let things take their natural course. Clean up your seams with acetone. The glue will ooze slightly and this cleans that up. You will be then left with a smeary haze over the aluminum. I then clean this off with lysol but a glass cleaner will work just as well. Other citrus-based adhesive removers will work too if you have concerns about safety using acetone. If you plan to polish, do so next. You want the polishing done before rivets and paint work. I'll get more into these additional finish techniques later after I've finished the covering... at a later date.

Got it? Yeah, me neither. This part took about 2 hours from start to finish, and I work fairly fast. Think of it as wrapping a very elaborate anniversary gift for your spouse. If you mess it up, you will never hear the end of it.
 
It looks a million, but holey moley, what a crazy amount of work!
You should consider remodeling part of your workshop to a sweatshop and employing some chinese guys to do this labour...
 

wilmracer

I build things that fly (sometimes)
Mentor
Yeah, its definitely a lot of work, but the results speak for themselves. Tough to beat that look for scale authenticity.
 

willsonman

Builder Extraordinare
Mentor
Not much to visually report on. I was invited by another forum member to present the project at his club meeting this week. I took this as motivation to finally assemble all the parts, although only dry fitting them, and get everything working and programmed.

I was able to confirm that the gear and gear doors were working together in sync. The switch was in the wrong direction so I had to correct that in the programming. I also got the landing light movement and light on/off channels programmed. It took a little bit of finesse to get the pylons to drop properly as the movement is very tiny. My endpoints had to be finely adjusted and I setup the servo to have no tension at dead center. The endpoints ended up at 0 and +25%. A far cry from -100 to +100%. From there I needed to check the movement of the accessories. The cowl flaps were perfect as well as the oil cooler/ waste gate valve assembly. I inspected the intercooler doors as well and one needed a tiny bit of adjustment. The servors for those doors procude a little bit of chatter but that mainly has to do with the long servo arm extensions. It makes it a tiny bit harder for the servos to properly center with any sort of load on them. I verified this by changing the endpoint for them. It would remove the chatter but once position changed and then returned the chatter would return. It's not a major issue but it is something to keep an eye on. The tail gear continues to be rock solid, something I had concerns about but it just keeps working perfectly, along with the doors. I then dry fitted the ailerons, flaps, elevators, and rudder. The H-stab was slipped into position as well. I received a proper wing bag in the mail so after all of this, I put the wings in the bag and it also includes a pocket for the wing tube. A nice touch. The bag has padding on the inside as well as two pockets. The big thing is that it is lined with a microfiber fleece. Something I HAD to have to avoid scratches and wear over time.

Tonight, I'll focus on laying down more panel lines. This way, once the club meeting is over, I can make a major push to complete the foil covering.
 

wilmracer

I build things that fly (sometimes)
Mentor
So pumped to see this tomorrow night! She looks great in pictures and video but I can only image how awesome she looks in person.
 

willsonman

Builder Extraordinare
Mentor
I hope it's not too much of a let-down. There are areas of bling right now but I think the full experience will be when we go to SEFF. There will be SOOOOO much more to look at and my hope is to talk folks into coming back later to look at it in different lighting conditions. I think you will be able to appreciate the transformation by seeing it tomorrow as well as the completed model.
 

willsonman

Builder Extraordinare
Mentor
Got more panel lines applied. Both tops of the wings are done and I got the bottom done on one side. Due to the change in layout of the gear, pylon, and servo hatches, I made several compromises in terms of panel line location. There is a lot that is different but the look will be right. Everything is coming together now. The rudder will take time, similar to the elevators. The H-stab will be pretty easy, comparatively speaking.
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