|Feb 11, 2009, 09:47 AM|
Rounding The Cowl
More progress on the p-47. The cowl ring needs to be shaped to look like the real thing. Looking at the images attached to this post, we started by carving off excess balsa material. Mark drew several reference lines onto the cowl ring so we could do this in stages. We used various tools including knives, files and various grades of sandpaper.
Speaking of sandpaper, there were several types used. 80 grit, 150 grit and a flexible sponge-type sandpaper that was really nice to use on the curves.
I can't tell you how many times I have used a knife/blade on balsa or some other wood and gashed our gouged it because I was cutting up the grain or against the grain . Mark showed me that by cuting down and along the grain makes whittling/carving much easier and the end result is wonderful. I am sure there are posts that address wood grain and carving/cutting techniques somewhere here at rcgroups that can better explain what I am talking about.
Ok, so we placed blue tape around the foam where it meets the firewall. Gashing or sanding that area by mistake can easily happen and the foam is easy to mess up with these tools. We left the blue tape there until we needed to blend in the foam with the firewall/cowl.
We didn't need to do a lot of sanding to the foam that leads up to the firewall & cowl ring, but just enough to be able to blend to a nice smooth finish. The goal was to be able to smooth our hand over the foam, firewall and cowl ring, back and forth, and have it feel completely smooth.
The inside of the cowl ring was sanded and then the outer edge was sanded to a nice smooth rounded lip just like on a real Jug .
|Feb 11, 2009, 04:34 PM|
Joined Feb 2002
Beautiful!! You could label that sequence of pictures "the joy of modeling"! Doing such work gives us a tiny peek at how Michaelangelo might have felt on his good days.
|Feb 11, 2009, 05:17 PM|
To me, this was probably the scariest part of the built so far..... the next will be the maiden
As I was working on the cowl ring, Mark's mind was working overtime preparing a jig to cut out the wing saddle. The P-47 Thunderbolt wing runs through the fuselage. This means that not only do we need to create a wing saddle but also the belly. The cut we will make here will provide for both.
Here is the process we used to cut out the wing saddle:
1. Created a jig to hold the fuselage upside-down on the workbench. (we used foam)
2. Created a template to run the hotwire to cut the foam (we used cardboard and heavy card stock for the hotwire to run along as a guide)
3. Laid our drawing on the belly of the fuselage and marked our starting and ending points for our cut
4. Used a Zona saw to cut the keel (balsa) so the hotwire could pass through.
5. Aligned the fuselage so it was perfectly perpendicular to the table surface & cutting jig
6. Cut the wind saddle with a hotwire.
Making the Jig to hold the fuselage upside-down while we cut the wing saddle was done by using the "E" templates of the fuselage as a reference and creating a new template. Two of these were made and used so Mark could hotwire the foam. It was a perfect fit and held the fuselage in place wonderfully.
Making the templates to cut the wing saddle was more complex. The template Mark made was pinned (attached) at the base of both sides of the fuselage wing saddle jig. The pictures will better explain what it looked like and how it worked. Maybe Mark could address this more if need be.
The All Important Keel
For those who asked if the keel was necessary...... the short answer is "YES". It would have been extremely difficult to align the fuselage perfectly straight so that our wing saddle cut was lined up. See the picture below and notice the right angle tool we used to check the alignment. The added strength to the fuselage and then to be able to use it as a reference for sanding/shaping as well as the wing saddle cut has made this one of the best decisions to include in our design & construction.
Next we will be working on supporting the inside of the wing saddle with wood and then cutting, putting some CA on the cowl ring for protection and cutting the top hatch.
|Feb 11, 2009, 10:11 PM|
Real master at work here, I sure hope the ARF world isn't looking in; if they are they must be praying this doesn't rub off on to many people -- you mean you can "build" a model ?
|Feb 12, 2009, 12:02 AM|
This is a fabulous build log. Thank you for taking the time to describe your processes and techniques. The global economy may be slumping, but my guess is there will be a run up on wire cutters at local hobby shops across the nation. This really looks like you're having fun!
Have you designed your control surface systems? If yes, could you give us a sneak preview or brief description?
|Feb 12, 2009, 07:34 AM|
No rudder, as there is no gear for which to really need one. Standard pushrod elevator. Still doing some thinking on the ailerons. Have to have a look at the geometry and see if we can pull off torque rods. If not, then maybe flexible pushrods...
|Feb 12, 2009, 07:34 PM|
Thanks for the support and comments guys.........
Jugjock, I was looking at Mark's Spitfire the other day and noticed that he had 1 servo for both ailerons. Each aileron had a direct pushrod that ran inside the wing directly to the control surface. There were no pushrods or control horns showing on the wing..... a nice realistic clean look. See this link and scroll down and look at the pictures of Mark's Spitfire:
I really am having fun with this project. I am learning a great deal about model building. I think that it has truly changed the way I look at the hobby and hopefully improved my skill level Here are a couple of examples I learned from Mark:
Before Mark's Instruction - fill any gaps in the wood with glue
After Mark's Instruction - Cut, sand & fit wood so there are no gaps
Result - Stronger and lighter model (light flies right)
Before Mark's Instruction - When sanding wood or foam, more pressure is better
After Mark's Instruction - Let the tool do the work
Result - Fewer mistakes and a nicer looking job.
I am glad this thread is helpful for those who might not have really been able to see "how something was done". I would strongly recommend everyone to checkout some of Mark Rittingers Build Logs. You will be able to see and learn some really cool and interesting techniques/methods that he used on his various projects. If you are interested in doing a scratch build project try Mark's p-51 Mustang........ According to Mark, it is the easiest and quickest of his Warbird Series to build.
Here are several of the builds he has done providing some really good examples of different building techniques.
JMGlascraft North American 262 Reno Racer
Rittinger Fw 190A8
Rittinger A26 Invader
S400 DH7 Caribou
The Python (P-51)
Me Bf 109 E/G
MM Geared P-40
S400 Ki61 Tony
I am sure there are other builds that I have missed, but these are some of the highlights. Enjoy.
|Feb 12, 2009, 09:11 PM|
I went ahead and cut the wing blanks.
What we are going to do is cut inner and outer sections, join them, then sheet and sand smooth. The outer sections will have 1/8" washout.
After sanding, we'll sheet them, then cut the ellipse from the Trailing Edge.
At that point the ailerons will get cut out and faced, and the tips added from balsa.
|Feb 17, 2009, 10:59 AM|
Foam Wing Cores Cut
As pictured in the previous post, Mark cut out the 4 blocks of foam that will be used for the wings of this P-47. We are using 3 templates to make our wing shape......
- Wing Root (inner) Template
- Center Section Template
- Wingtip (outer) Section Template
Templates were pinned onto the side of the foam block and use as a guide when we hotwire cut the wings. It is important to have a foam block that has straight 90 degree sides so each wing section will fit snug and flush.
There are a couple of considerations when cutting wings with foam.
1. Washout - We added about 1/8" washout to the outer sections of the wings. This means that when the wing is complete, from the wing root (center of the wing) to the tip, the wing will appear to have a twist. This twist is there so when the plane is flying to slow and begins to stall, the outer section of the wing will not stall first. In short, this "washout" will help prevent the plane from "Tip Stalling". We accomplished adding "washout" to the wings by taking the outer template and angling the leading edge of the template downward 1/8 inch. See pictures below for more details.
2. Dihedral - We will be adding dihedral to the wings when they are glued together. This will take place by sanding our dihedral angle into the root at that time. When you add dihedral to a complete wing, you are creating a slight "V" shape. The wing is not flat, but the tips are elevated higher than the root. This helps with increase lift when banking the plane and generally provides for a more stable aircraft.
If you are confused or want more information about both washout and dihedral, check out this link http://www.aerospaceweb.org/question...cs/q0055.shtml . It includes some pictures and drawings that will help make more sense.
We used the hotwire to make all four sections. Mark did all of the wing cutting. Let me tell you..... he cut all 4 sections and did not have to scrap or redo any of the sections! I got some video of the hotwire and will try and post it soon.
The leftover foam that was cut away from the wings are saved and will be used to "sandwich" the balsa onto the foam when we sheet the wings. In the meantime, it will protect the wing until it is sheeted.
Wing sheeting will be done soon and then cutting the eliptical shape on the back of the wing. More details on this in a later post.
|Feb 18, 2009, 07:41 PM|
P-47 Canopy Mold
This project will have a plastic molded clear canopy with the framework just like the real plane To accomplish this, we will be using the vacuum form method to make it. Mark found a nice piece of basswood to use and cut the rough shape using a band saw, then filed it down with a rough file and then used the disk sander...... its nice having some sweet power tools when needed. After some fun sanding with 120 grit sandpaper the mold is ready for the "greenhouse" framework. More on that later.
|Feb 19, 2009, 09:23 AM|
Wing Saddle Inside Support
The wing saddle has been cut as posted previously. By doing this, we have made the fuselage much weaker. Being that this bird will have a permanent wing and won't be removed, it will help make the fuselage a very strong unit. Having said that, we are putting 1/16th balsa strips inside the fuselage along the wing saddle area. This will give added strength, but most importantly, it will help keep the fuselage together when we cut the hatch (in my next post).
So, we took a rectangular piece of balsa, laid it inside the saddle area and then drew a line along the saddle onto the balsa support. We also traced an outline of the rest of the balsa piece inside the fuselage. After trimming the pieces to shape, it was time for the glue.
Mark suggested Dave Brown Southern's Sorghum contact cement as the adhesive. I had never heard of this stuff. It is used for sheeting wings to foam..... It looks like wood glue. After wiping it on both the inside of the fuselage (within the traced outline where the balsa would be applied) and the balsa that was to be used as the saddle support it took about 15 minutes to dry to a clear state. That is the indication it is ready to apply. This stuff is really sticky. As soon as it touches, it wants to stick! Once in position, pressure can be applied to permanently set the support in place. After that, a little trimming to make the balsa flush with the foam saddle was needed and next we will put 1/32 ply strips along the the saddle edge where it will join the wing...... but first, it is time to cut the hatch
|Feb 20, 2009, 11:00 PM|
Cutting the Hatch
Now that the inside wing saddle have added support, we can cut the top hatch of the P-47. The servos, speed control, receiver and battery will all be accessed through the top hatch because the wing will be permanently attached to the fuselage.
Determining how big the hatch would be was based on need/accessibility. After deciding the size, the lines were drawn and an xacto knife was used to cut the hatch. A 45 degree angle was maintained so the hatch would not slide around during flight.
We used an metal straight edge to cut a nice straight line. We used an xacto saw to cut through the keel. Strips of 1/32 ply will be used to line both the hatch and the opening.
|Feb 21, 2009, 04:10 PM|
We should make some good progress this week Mike.
We'll be able to add the edging on the hatch,and the framework on the canopy mold.
After that, it's on to the wing joining and sheeting....
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