Thursday, July 20, 2017

Mitchell U-2 R/C Plane Project Pt. 4

I wanted to get this out today as the R/C plane project has started to really take shape.  So with that in mind I am still hopeful that this project will literally get off the ground someday soon.  Here is where I am at with it as of this morning.

After my recent motorcycle trip to Colorado I was overjoyed to receive more filament for my 3D printer so that I could complete the construction of the fuselage for the plane.  Pictured above is the front and back halves of the fuselage.  The rear section with the blue tape on it had been curing over night so now I was ready to join the two parts.

These two photos of the final assembly of the fuselage worked out rather nicely as the 3D printed parts only need to be held together with a couple of small clamps while the last joint of the fuselage was epoxied and again cured over night.  The fuselage shown above is 16.5 inches long 4.5 inches tall and 4 inches wide where the wing meets the fuselage.  Lots of room inside for extra weight to be added so that I can get it balanced for it for glider test flights.

I then only had to put the canopy on the fuselage and insert the pins installed in the wings into the mounting holes on the fuselage.  It looks pretty impressive already.  With a wingspan of 68 inches and total weight at this point at 2 pounds I am more than happy with the end result even if it is just a static model so far.  The 3D printed parts (fuselage, canopy, wing root edges and the wing tip vertical stabilizers) took 40 hours to make with my 3D printer.

I blocked up the plane on both side to get this shot and looking at it I think that would be exactly where the main landing gear would be mounted.  

I have the fuselage and the canopy pretty well smoothed out at this point. The wings and the fuselage I will not paint until I am sure it actually flies.  No point in going crazy over making it look pretty at this stage of the project.  That can wait till later if all goes as planned.

Inside of the fuselage the wings are held on with some odd shaped washers that I found at my local builders store a couple of weeks ago.  I think they will work out pretty well to hold the wings on when I do the test flights. They are a nice snug fit so I would be really surprised if the wings moved much at all when mounted this way.

I still will have to work out the details of mounting the canopy to the fuselage.  I plan on using magnetic mounts for this part of the construction.  I ordered the neodymium magnets I need a couple of days ago and I suspect it will be next week before I have them in my hands. In the meantime I will work out the 3D printed mounts for the magnets so I can install have them ready when the magnets do arrive. 

Once I get everything assembled I plan on shooting video of the first test flights.  I say flights in the hope that the plane will actually fly.  It could be test crashes for all I know.  Actually I think I have a pretty good shot at getting the project off the ground. I will have to balance the plane so the center of gravity is correct then I will have much better odds of actually getting the plane to fly. 

I flew  large R/C gliders years ago so I have a pretty good idea of how the plane should be set up to fly.  The gliders I flew had wingspans of over 7 feet.  I loved flying them so now to have a model of the actually plane that I built will be even better yet.  Hopefully it will all work out in the end.  Again as before I am still keeping my fingers crossed on the this project just to be on the safe side. 

Saturday, July 15, 2017

Mitchell U-2 R/C Project Update Once Again!

Sorry for not posting anything over the past couple of weeks. I have been on a major road trip this past week doing research on parts for another project that will be happening very soon.  I don't want to get into it at this point but I am sure a lot of you who read my blog regularly will be excited by the project when I do post it in the coming weeks.  So let me get you caught up at least on the Mitchell U-2 Project.

As most of you have already read in the past couple of posts I have been working on a R/C model of the airplane that I built years ago called the Mitchel U-2.  A 34 foot wingspan flying wing.  I have not found any models of my plane so I decided to try and make a radio controlled model of it myself.  I was finally able to get back to work on the project today.

Here once again is an image of what the R/C plane will look like once it is completed.  It will have a 68" wingspan. 1/6th scale of the full sized plane.  If all the test models work out ok this will be the end result of my efforts.

Here is the canopy that I have pretty well smoothed out.  I will have to do some wet sanding yet on this part and figure out the magnetic mounts that I will need to hold it in place for the plane but so far I am very happy with the shape and smoothness of the part.

Here the first two sections of the fuselage have been joined together.  I used epoxy/micro-balloon mixture at the joint along with several layers of fiber-glass on the inside to hold the nose section securely in place.  I will use the same process on the remaining two sections of the fuselage to put it all together. It should do the trick nicely.

This is one of the inner wing sections being assembled with the mid-wing section.  Again I used the epoxy/micro-balloon mixture to join these parts together.  The sanding block was laid on top of the inner wing section just to hold it flat against the table while the putty mixture dried.  You can see a small piece of wood on the outer edge of the of this assembly.  This will keep this wing section tipped up at the right angle while the resin mixture cures.

Here is a view of the opposite wing with the outer wing section and wing tip being attached to the inner and mid sections of the wing.  Again pieces of wood were used to hold the outer wing tip at the correct angle so the dihedral on the wing could be created and matched on both sides of the plane.

Once the wings assemblies had cured properly I was able to take these four shots of the wing to show you what dihedral is. With the wing tips tipped upward as you can see in the photos the wing becomes more stable and the plane will want to fly level.  I had to place a small 2 X 4 piece of wood where the fuselage would be to keep the inner wing section flat against the work table.  Then the wing tips would be in the right orientation as shown in the photos.

In order to hold the wings on to the fuselage I needed to mark and drill two holes in each wing to hold dowel pins for this task.  I used my drill press and managed to get the 1/2" holes drilled accurately as I could. Surprisingly drilling Styrofoam worked.

I drilled the holes four inches deep and then secured the pins in place using the epoxy/micro-balloon mixture once again.  I poured enough of this mixture into the holes and then slid the pins into place so they could cure overnight.

To make sure the pins would match up exactly with the mounting holes that will be in the sides of the fuselage I 3D printed an exact template of the fuselage side where the airfoil shape meets the wing.  The holes are exactly the same in the template and the fuselage.  Should work perfectly.

After the mounting pins had been installed and cured I mounted an additional 3D printed plate that will match up with an identical surface on each side of the fuselage.  This will help make the end of the inner wing safer from accidental damage due to either flying or even assembling the wings to the plane.   

Lastly I decided to add a 3 ounce layer of fiberglass over the joints where the wing sections meet.  It will add very little weight and give the wing much more strength when flying the model.  

I just received an order for more 3D printer plastic today so I will be able to continue my work on the fuselage.  Hopefully I can get this completed in the coming week and get the glider test model ready for it's first flight.  I also have figured out the center of gravity (CG) for the plane so this will help a lot in making sure that the plane is neither nose or tail heavy. 

I don't plan on covering the wing at this point.  Hopefully I will have some successful test flights for the glider version.  Once this works out then I will figure out battery, radio, and servo locations and get that all working properly.  So one step at a time.  Once I am certain that all will work out as planned then I will think about possibly covering the wing to make it even stronger and give it a nice finished look.  Again just will have to see how testing goes on the glider version first.  Keep your fingers crossed. 

Friday, June 30, 2017

Mitchell U-2 Flying Wing R/C Project Progress and Setbacks

This has been quite a week for me while working on this project.  There has been some nice progress with the build and a setback or two so I thought I best get this out to everyone before I forget what I have been dealing with or give up completely on the project.  Not likely in either case I as I would rather work things out and keep moving forward on the plane to complete it.

For the progress this week I have manage to get the wing of the model pretty well prepped for final sanding.  The flaws that I found after cutting the wing have been either sanded out or filled in with the white colored micro-balloon epoxy mixture.  A very light substance that I mixed up for this and for all my fiberglass projects.  I will have to sand the wing one more time and then I will have to figure out if I am going to do any covering over the wing for the glider tests that will follow.
This side view of the fuselage shows the different sections that will have to be 3D printed to build it. At the top of course is the canopy.  Then starting on the left and moving to the first vertical line is the nose of the fuselage and then three more sections ending with the tail section. This was done this way simply because I do not own an industrial sized 3D printer.  I can make some rather large 3D prints such as the canopy in one piece which by the way is 8 1/2 inches long but the entire fuselage put together comes up to 16 1/2 inches long.  Far larger than my 3D printer can handle so this is the plan of action for the 3D printing part of the project.

I also managed to make some really nice 3D printed parts for the project as shown above.  The top piece is the nose of the fuselage.  This I sanded smooth starting with 120 grit then moving on to 600 grit for wet sanding and then another round of 800 grit also wet sanding to give it a very smooth and uniform surface.   Below the nose are the two wing tips for the plane.  These I did not need to be sand at all as the are plenty smooth and will work out perfectly.  The nose of the plane took four hours to 3D print and the two wing tips took an additional three hours total to make.  Not out of the ordinary as 3D printing large parts takes a bunch of time.  The nose is 3 1/2 inches tall and the two wing tips are 3 1/4 inches tall.  

Here is the second section of the fuselage.  I am very please that this part turned out as well as it did as it is one of the key pieces to mounting the wings.  You can see the first portion of the airfoil on the side of the fuselage with a hole going through it.  This hole along with another one in the next section will allow the wing to be attached and removed when I am transporting it.  The wing having a span of 68 inches makes this a necessity.   The wing will have wooden dowels that will match the mounting holes and then be locked together inside of the fuselage. I have a plan for that when the time comes.  This being another large part  being 4.5 inches tall, 4 inches wide, and 5 inches long took 9 hours to 3D print.  Again I sanded it smooth to prep it for final assembly to the rest of the fuselage.

Now on to the setback and recovery of the project so far.  Pictured above is the bubble canopy that will be on the plane.  It was to take five hours to print this large part and be totally black and pretty in the process.  I was not so lucky with this 3D print.  Four hours into the making of this part my 3D printed decided it had enough and stopped printing. Auggah!!!!!!   So now I had a windshield instead of a bubble. What caused the failure was a clogged drive wheel for the extruder.  It happens.  Not that I like it but it happens.  Any easy fix and I am 3D printing once again. 

I shifted gears and last night epoxied and fiberglassed a small piece of Styrofoam to the failed 3D print.  It was a shot in the dark to try and save this part and not have to try and print another that would take an additional five hours to complete. 

With some careful trimming and sanding I was able to resurrect the part and save it from the trash can. With the shape of the canopy pretty well formed already it was only a matter of a few minutes work and I was able to save the part.  I will then fiberglass the exterior completely with a couple of light layers of fiberglass cloth and then sand and smooth everything as I had originally planned.  I think the weight will not be a factor as the foam and glass combined will give me the shape but not add to much more weight to the part. 

I had to tape the parts together to give you a good photo of how the fuselage will look for real if only the front section can be shown so far.   I will fiberglass all of the parts together once everything has been 3D printed.  All except the bubble canopy which I plan to make removable.  This will allow me to open up the fuselage to add or remove weight to it when I want to balance the plane for glider testing.  If that all works out then I will look at making it a full R/C plane with electric power.  I may have to remake the wings at that point to get the controls all set up in the plane but this will be far simpler than having to duplicate the fuselage that by the way will probably take nearly 30 hours of 3D printing to complete.  I will give you the correct number on that aspect of the project when I get that far along.  Hopefully in the coming week.  So for now the project is still moving forward and looking pretty amazing on top of it all. Only time will tell if the project will succeed or not.  Just will have to keep playing with it.  

Monday, June 26, 2017

The Mitchell U-2 R/C Flying Wing Project Has Started!

It's been a little while since I last posted anything so I thought I'd better catch up a bit and let you know what I have been playing with since my last post.  I had been thinking of several different projects over the past few weeks and finally decided to work on one that has been on my mind for some time.  Years ago I built an ultralight aircraft.  It was called a Mitchell U-2 which was a flying wing.  A lot of people at the time asked me if it was a kit.  I told them if a pile of wood, some tubing, wheels and an engine was a kit than that what it was.  Not to mention a ton of fabrication and a lot of luck to even complete the project. But it was a very rewarding project just the same.  

Here are a couple photos of my plane.  It was a massive project and I am proud to say that I built it by myself.    This was quite some time ago when I built this.  (1982-1983 or somewhere around that time).  That brings us to today.  I thought it would be fun to build another plane like the Mitchell only much smaller.  I thought a replica of the Mitchell U-2 would be fun to recreate as an radio controlled electric model.  

As is usually the case with the projects that I build I start by doing some research and designing the project in my computer. This was the only image that I could find online of the Mitchell Wing that was of any use to me.  It is a good drawing to start with so from it I was able to create a 3D model of the R/C plane and begin working out some of the design.

 The image above is what I have come up with for the project of the Mitchell U-2 electric R/C plane.  As I stated earlier the original plane had a 34 foot wingspan.  I wanted the model plane to have a good size which I thought would be simpler to create and also not have to deal with very small parts out on the wing tips.  The plane that I plan to make will be 1/6th scale.  This will reduce the span down to 68 inches.  Still quite a large plane but this will give me lots of room for the radio gear, servo's, electric motor, and battery in the fuselage.  

The servo's for the plane need to be mounted into the outer portion of the wing to be able to activate the rudders at the tips along with the elevons. The elevens are the pieces that extend out past the trailing edge of the wing to have control like an aileron and an elevator on a conventional plane.  Only both functions at the same time. 

This will take some planning for sure as it has been some time since I've done anything with radio controlled planes.  I was able to create the 3D model and from it them start making the templates to create the wings in Styrofoam.  The image above shows the wing in blue and white.  Actually each side of the wing will be built in three sections. A white inner wing, then the blue middle section, and finally another white outer wing.  If you look at the image above you can see three differently shaped sections of the wing.  From these sections I started printing out templates for the various shapes of each wing end. 

Here is what the ribs looked like once I had plotted them out full size.  The top rib (Rib One) is 11 inches long and the smallest rib (Rib Four) is only around 2 1/2 inches long.  This short rib is used at the very tip of the wing. 

I then took the paper templates and transferred them on to 1/8" plywood, cut them out on my band saw and temporarily attached them to 2" thick pieces of Styrofoam.  The wooden pieces were then used as guides for my hotwire table so that I could cut out the inner most sections of the wing for the plane. 

These were a couple of first failed attempts at cutting the Styrofoam with the plywood guides and my hot wire table.  The trick was to start the cut at the same angle as the leading edge and then work my way around to the front of the wing.  I had more than enough scrap 2" Styrofoam sitting around in the shop from other projects so this was a good project to use it on.

After the first couple failed attempts at cutting the foam sections I got the process down to where with careful planning I had achieved near perfection on the shape of the first section of the wing.  As you can see the number one rib and number two rib templates gives the wing a very different look as to compared with a normal straight wing where the rib pattern is all the same across the wing. 

Here all of the wing parts have been shaped using the rib templates for the left side of the wing. Pretty impressive so far considering the wing has a long ways to go yet.

Here again is another shot with all of the major wing parts that I have completed.  At this point I will start sanding any imperfections that I have in each section of the wing and filling in any voids using a micro-balloon and resin mixture.  Then more sanding will be the order of the day to get the wings perfectly shaped the way I want.

I had to slide all of the pieces for the wing together to check and see how close I was to that actual dimensions that I had designed on the computer.  The wing above measures 64" exactly.  This is perfect as there is no fuselage built yet but I do know that it will be 4" wide so this will give me exactly 68" as I had planned. 

One other thing that I had to plan for while cutting out the Styrofoam for the wings was the dihedral that is designed into the wing for stability.  This took some carful planning in the cutting of the blanks for each section of the wing along with correct placement of the wooden rib templates.  From what I can see I think I have this worked out.  Just will have to see once I start test flying it.

The fuselage on the plane I had originally thought I would make out of fiberglass.  But after looking at the assembly in the computer I changed my mind and thought I would try and 3D print it instead.  The fuselage is 16 1/2" inches long, 7" tall and 4" wide at the widest section.   Quite large but I have it laid out in the computer and with some fancy cutting and splicing together of the 3D printed parts I think it is possible.  I'll give it a try anyway.  I printed just the nose section so far and that alone took four hours.  The next section going rearward looks to have to take nine hours+ so it will be a bunch of hours just to make the fuselage.  I'll keep track for sure on this part of the build.

To also work out some of the bugs that I will come across in the design the first plane will only be a glider. This way I can figure out the weight and balance of the plane and then later upgrade it so that the glider will then be radio controlled.  If that all works out then the final version will be a full electric powered motor glider.  So step by step.  I'll post more as I get some if not all of the parts for the fuselage 3D printed and put together.  

Stay tuned for further developments.  

Thursday, June 15, 2017

The "Altara" Concept Blender 3D Car Is Born!

When the dusts settles in my workshop from finishing a project I usually  can be found elsewhere creating something new on my computer using Blender 3D.  This is the case with the creation of a concept car that I originally drew a little over four years ago. At that time it was just a 2D image that was a spark of inspiration and so the idea was born to change it to a 3D model.  

Here are a couple of the completed images of the Altara concept car that I managed to put together over the past couple of weeks.  But before we get into more details on what you see here I want to show you where it all started and then the process of how I got to where it is now.

I liked the shape that I had come up with the time I put this image together but after looking at it again changes were the order of the day to make it just a bit more refined and workable as a 3D model.  The wheels needed to be changed first as what I have here was way to simple of a design.  So it was added to my growing list of what needed to be improved.

Having only a side view of the car to work with I needed to flesh out the rest of the body in Blender 3D to work out the front, rear, and top of the car to my liking.   Even the openings for the wheels needed to be tweaked a bit but at least the body at this point was taking shape.  

 Following cues from my original 2D drawing I started putting in the openings for the windshield and the rear window.  It was a start but everything that I added at this point was just to get an idea of what would actually work and not work in the real world.  I realized early on that I had a long way to go with the model.

Next I cut the openings for the headlights and refined the front hood of the car.  This was not terribly difficult and so progress was being made and I was encouraged that the design was possible at this point. 

Early on I start playing around with lighting of the car to see what I can see when I put the body together.  In the image above you can see the seams for the front hood, canopy and the rear hatch. I also started looking at headlight covers at this point.

At this point I added the tires and some rims to the design.  I kept the body height the same as the original 2D drawing and this was the result of that decision.  Not good to be sure.  The body looks nice and sleek but the tires look too small and unusable in the real world.  The front tires are not believable in the fact that the wheel opening is way to small for the tire to be able to roll much less turn.  More work changes to my list was in order.

At this point I raised the car up to give the wheels more clearance and enlarged the wheel opens to something that looked more proper. The wheel rims were close to what I was looking for but the centers were to small and there was no bolts holding the rims onto the hubs.  More items for my list of changes. 

The next step was getting the wheels and rims more correct looking.  I enlarged the center of the rims and added the nuts for the hubs.  Also I added a disc brake inside of the wheels rather than have it all blacked out by the lighting. On the front of the car I added a grill, running lights, signal lights and headlights. 

This next series of images gives you good views of the car body from the rear.  Taken from the original drawing is of course the body itself, the rear body quarter panel with the top arch and the rear window. 

Here you can see the original placement of the tires and rims. The body again at this point was still in the original placement that matched the original drawing.  In other words it is to low.  That and the fact that the tires are set to far into the body to be believable. 

I moved the wheels outward at this point which worked out very nicely but the wheel openings are to small as I said earlier in the post. 

Finally I have the wheels and opening corrected with the right body height.  But now what stuck out was the rear window.  Way to small!  It would not do.  So that would be the next step. 

I proceeded to make the rear window larger and with this process it cleaned up the entire look of the rear of the car.  

This is a good look at the side of the car before I finished off the wheels with the disc brakes.  I like the rear window and roof line now with the larger rear window.  Much more believable. 

 With the rear of the car I started playing around with taillights and a name plate for the car.  "Altara" I came up with from an old SciFi movie that I remembered so I thought it would be a good name for this sleek looking vehicle.  The rear of the body was recessed for the lights and no tail pipes.  I thought would be good as an electric car. So no tail pipes. 

Lastly I changed the glass in the car to clear instead of gloss black.  This made it look much more like a vehicle instead of just a model of one.  I still can put a lot more detail into the car by finishing out the interior with all the it needs but for now this will do nicely. Enjoy the images. 😀