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daveculp

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    Las Vegas, NV
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    Large scale aircraft modeling. 3D printing. Post WW2 military aircraft.

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  1. So I tried Kevin's trick of freezing parts to make the CA glue brittle, and it definitely helped. After a lot of cutting, sawing, prying, twisting and snipping I managed to extricate the original fuselage belly from the wing structure. This will save me a lot of time later. I had believed that the L-39 vertical tail was close enough to correct height for an L-159 that I could leave it alone. Upon further review it just looks too short, so I cut off the tip and am building a new one. This is the kind of thing I'm supposed to figure out earlier in the process. I'm going to print a small extension for the rudder since the geometry is already set in CAD.
  2. Thanks Kevin. I recovered quickly from the wing shock, and am taking it as a blessing. Now I have time to make progress on the fuselage while I await the new kit from Tigger. There are three areas which I still haven't decided on a solution for: 1) The tailpipe - I have an acrylic tube that's the right size but too heavy. I'm still searching for a thin-walled alternative. 2) The cockpit glass is going to be tough. I might have to build up the canopy frames to get a good look and fit. I plan on making the aft canopy closed and pilot's canopy open. 3) The gear will be 3D printed. The question is will they be strong enough? We'll see. -- Dave
  3. With the dorsal hump done I'm starting work on the intakes. The splitter plates need to be scratch built from styrene card. I added a thin spacer where the splitter plates attach in order to move them outboard just a bit. Here I've painted the fuselage and the inboard side of the splitter plates with a primer that closely matches the final color of this area. I also clearly marked the splitter plates to avoid stupid mistakes After the splitters are installed I'll sand the intakes down on the sanding board until they fit flush. I left some extra material at the intake opening for now to keep the part strong while I sand it down. After that more putty and sanding. The tail end is progressing slowly. This end is complicated and requires several interations of putty and sanding. I used Milliput to get the basic shape of the area above the exhaust opening. I'm using Tamiya gray putty for filler work, and I use Bondo glazing and spot putty for the final shaping. The Bondo is very easy to use but it doesn't handle scribing very well, so you have to use it only for small touch-ups. Eventually it'll all come together. The control surfaces are 3D printed, and I printed them with 0.4 mm thick trailing edges. I could go even sharper than that, but I don't want them to be too delicate.
  4. A couple photos from my airshow/museum folders. The F-84F and the F-86. Both appear to be handed.
  5. This is a cross-post from my L-159 project. The question is a general one so I'm posting here to get more opinions. The issue began after I was studying photos and found one that surprised me: (original photo credit: Jan Kouba Czech republic 2013. All rights reserved.) I added the green lines and text. What surprised me is the pylons are perpendicular to the underside of the wing rather than being aligned with the vertical. In this case I figure it's about a 4 degree difference. The best explanation I've read for this comes from forum member Oldbaldguy who figures it's done to keep the pylons from being handed, so they are interchangeable left and right. That sounds like a fair explanation to me. I'm pretty sure I've seen pylons on other airplanes that are aligned with the vertical, and I'm currently pouring over my books looking for examples, but it's hard to find photos taken at just the right angle. I suppose it could vary from one airplane to the next. It might depend on the dihedral angle - too much dihedral and you have to go with handed pylons. It might have to do with weight limits on the pylon - above a certain weight the pylon needs to be vertical. Maybe it's an option for the buyer. Are there any general rules for this, or do you just have to study each airplane? I've learned that you can't trust 3-view drawings, which are really just artist's conceptions.
  6. That makes perfect sense. I assume then that the sway braces in this case will also be angled 4 degrees from horizontal, and the store will hang 4 degrees off from the pylon centerline. In the photo it looks like the gun pod hangs this way.
  7. While I await a new kit to re-do the wings, here's the progress on the fuselage: For conversion to the L-159 type: 1. Make the exhaust area straight (parallel to red line shown) 2. Add a filet below the rudder that extends all the way back 3. Add a small fairing for a rear-facing light 4. Finish up the dorsal hump For general additional detail: 5. Cut out the NACA scoops 6. Cut out the elevators I won't print a new set of elevators until the horizontal stabs are installed. That way I'll have a final set of measurements to use. And I won't install the horizontal stabs until the aft fuselage is close to complete. While looking at photos of the L-159 on the internet I noticed something unexpected. The wing pylons seem to be perpendicular to the underside of the wing rather than parallel to the local vertical (gravity vector). It's only about 4 degrees of difference, but I wonder how common this is? Maybe it's like this on all airplanes and I just never noticed before? I've always assumed the pylons are vertical. (original photo credit: Jan Kouba Czech republic 2013. All rights reserved.)
  8. The lower surfaces are installed correctly, but the upper surfaces are on backwards. I then cut the upper surface ailerons and flaps off based on the location of the molded-in recess marking the aileron hinge line. Then I flipped it over and cut the bottom surface. End result is the upper surfaces are cut correctly but installed backwards. The lower surfaces are installed correctly but cut on the wrong edge.
  9. I installed the wings backwards. The fuselage is wider at the rear, so it can only go on one way. This is what i get for not marking the parts with an arrow pointing forward. I considered cutting the wings off, but there's enough CA glue there to hold a real L-159 together.
  10. The project is on hold because an unrecoverable problem appeared. While I await another vacuform kit from Tigger I'll continue to work on the fuselage. See if you can spot the problem: I need a drink.
  11. How did I miss the hump? It was staring right at me the whole time. Here's a shot of wing trailing edges installed and the new spine being built.
  12. Your're right, it does! Thanks for noticing that. I'll have to build in a hump.
  13. The 3D printed wing trailing edge came out just right. I've decided not to worry about weight any more. If I have to pose the airplane on a stick then so be it. Maybe I'll learn how to make brass gear. The resin parts can be scribed just like styrene. The right side is printing now. I spent much of the day carving out NACA scoops and drawing up the instrument panel decals.
  14. I have the cockpit roughed in and am printing up the small bits. I've made the front panel, pedestal and pedals all one piece. I've decided to make decals for the instruments, so they'll be 2-dimensional. The left console will have the throttle designed in, but the rest will be decals. I'll wait for installation until after the exterior is painted. I know one of the big chores when making a vacuform model is getting the wings and tail surfaces the right thickness, and giving the trailing edge a sharp edge. Judging by the amount of work this process has already required just for the rudder I don't think I'll have the patience to shape the wings. So, alternate plan is to cut off the trailing edge and either scratch build or print new ailerons and flaps. Either way will work. Printing them will be less work but will weigh more (and they're behind the CG). I'm inclined to print just because I like repeatable processes, but I've discovered that in the vacuform world the printed parts are all designed to fit the current model - and I don't think I could make the vac parts the same way twice. By the way, the more work I put into the rudder the more likely I'll just cut it off and make one as well. The drawing seems not quite accurate. From photos I've seen the aileron leading edges aren't swept - they go straight out just like Tigger molded them.
  15. The Honey Badger has a single seat cockpit, the rear cockpit being full of electrical equipment with a sun shade built in. Here's a photo from wiki commons (credit Thomas Del Coro): One thing to note in this image is that the rear canopy is raised up a few inches. Also, note that the crease where the fuselage side meets the canopies extends aft and disappears behind the splitter plate. So, the kit's one-piece canopy part needs to be cut up so the aft canopy can be raised. Locating the wings so I know where to cut open the fuselage. I cut out the belly of the airplane so that the wings can be attached at the correct angles. It also make it easier to install a spar. I gave the bottom of the wing 4 degrees dihedral. That should give the top surface of the wing about 1.5 degrees diredral. The wings look pretty strong, so I only need to run the spar out to the main landing gear mount points.
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