1/48 CP-140M Aurora -

[Joel_W]

Mark,

Simply a brilliant engineering plan, perfectly executed. The extra needed 1/4 spacer didn't pose any problems, and the final results are dead on.

Joel

[Trojan Thunder]

Nice method mark. I attempted to stretch a C-130 and it did not go to plan. Looks like I will have another crack at it with this method.

Edited December 28, 2014 by Trojan Thunder

[Aurora Mark]

Mark,

Simply a brilliant engineering plan, perfectly executed. The extra needed 1/4 spacer didn't pose any problems, and the final results are dead on.

Joel

Joel, thank you kindly. I'm certainly having a lot of fun with this CP-140 build, and some of the challenges that it is presenting. As I mentioned before, I am hardly an expert. What I am is lucky; so many folks have written a number of great articles on the internet that act as a fantastic guide. Though there are many ways to skin a cat, thankfully there are many great how-to's on exactly, well, how to do it!

Nice method mark. I attempted to stretch a C-130 and it did not go to plan. Looks like I will have another crack at it with this method.

Trojan Thunder, thanks! I honestly spent many hours looking and reading up on how to stretch a fuselage. This method worked great for me for a few reasons. Firstly, that it was only a quarter inch. What I mean by that, is that if it were a longer stretch, such as stretching a C-130 for a different variant, the length of the stretch would prove to be very flexible, and a weak point. What I would strongly suggest if adding more than 3/4 of an inch, would be to step it. What I mean by that, is that rather than a single cut down the vertical axis of the fuselage, to make a stepped cut, and have the vertical cut staggered by some margine that would allow the original fuselage to overlap on the horizontal axis. If not this, than another method with a round tube fuselage (like the C-130 and CP-140), would be to use different thicknesses of strips.

I used 0.5 mm for everything, and I think that by using a thicker piece inside (the 3/4 inch strip I used), and making it 0.75-1.0 mm, that would work great (but I would recommend rounding it under hot water first, so that it more easily conforms to the inside of the fuselage, as well as a 1/2 inch overlap onto the inside of the fuselage, not just 1/4 inch like I did here), and then using more layers of thinner straps, such as 0.25 mm. That sandwich with the glue would work much better than just 0.5 mm.

I hope this helps, and look forward to hearing how it turned out!

Work pleasantly continued with one of the more daunting tasks - building the floor.

The first thing I did was cut a sheet of 0.5 mm plasticard in half, and tape it end to end. Then it was a matter of drawing out a center line, with division lines every cm. I had a guide line for where the floor should end and butt up to the step to the flight deck, along with the round shape of the rear pressure bulkhead:

Knowing that the tube section (before the taper at the rear) had an even width, I measured out the profile disc from before, to determine how wide the floor should be:

From here, I just went every 5 cm, and drew a quick arc with the compass for the widths all the way up to where the taper started:

Once that was done, simple straight lines were drawn on either side, knowing that this was going to be the interior width where the fuselage floor would be. As for the taper, that was a bit more complicated. So, drawing out the floor level on the exterior of the fuselage from where the taper started and moved rear, I made 1 cm marks until the bulkhead:

From here, using the caliper, I measured the distance from the marked point, to the center of the fuselage. These were then marked out accordingly on the floor, and two lines were drawn for one half (the outside line was the outside dimension, inside line takes into account the thickness of the plastic:

These points were then mirrored on the other side using the same measurements, and the same inside line was drawn in:

After the line was drawn in for the tapered rear fuselage, I needed to take the distance from the pressure bulkhead and where the measurement started. The overall floor length was measured from the corners, not from the center of the pressure bulkhead:

This difference was then added to the front cut line, in order to get the overall right floor length in the cabin:

So, there we go! The floor is ready to begin getting cut up!

[Aurora Mark]

After the first cuts were made, the last little bit was to size up the additional 3/4 inch strap that was used to stretch the fuselage, and remove this little bit:

Now it was time to see if the measurements worked out. I lined up the floor, taped it in along the floor line, and then at the right angle (making sure the floor sat flat), I checked the gap by using my desk lamp from above:

SUCCESS!

The test of both fuselage halves together also worked great with no trimming needed anywhere. She sits nice and level like I was hoping!

From here, I went and marked out where the Hydraulic Service Center was, and what would be visible from underneath:

I wanted to add a second layer of plastic to stiffen the floor up, and the only area where the thickness of the floor was key (0.5 mm that is), would be anything visible at the HSC. Hence the cut out. The rest would be perfectly fine being 1.0 mm long. Areas like the bomb bay will use the bottom of this 1.0 mm floor as the ceiling of the bomb bay, and you wont be able to see that the floor is thicker, but where the HSC will be open both from the bottom of the fuselage and from the cabin floor, I wanted to keep the floor looking like it was scale thick. So, once it was cut out, the floor was sanded with 220 grit to rough it up for super glue:

Last but not least, a second layer of 0.5 mm plasticard was glued over top:

This was literally taken a few seconds after the last piece was put on. Right after, I went over it with a roller, to flatten and smooth all the glue out, and then it was sandwiched between two pieces of glass to ensure that it dries completely flat. So, that's about it for tonight. Tomorrow I'll trim out the excess plasticard from the edges, and then measure up where the plasticard lip will be glued onto the fuselage halves for the floor to sit on once it's ready.

Thanks for looking!

Mark.

[Colin K]

Mark......this is super impressive work so far! Like most others, I also have the 72nd scale P-3, which I will build as a CP-140. I will definitely be keeping tabs on this thread.

Oh....do you know a Steve McDonald?

[TommyP]

This is outstanding Mark - I've built many challenging vacs over the years and thought I had all the techniques I needed. However, your really informative tutorials are very valuable and I'm keenly taking notes.

Thanks for taking the time to document your build for us - I'm sure vacform novices and experts alike are taking a great deal from this.

Tom

[Aurora Mark]

Mark......this is super impressive work so far! Like most others, I also have the 72nd scale P-3, which I will build as a CP-140. I will definitely be keeping tabs on this thread.

Oh....do you know a Steve McDonald?

Thanks Colin! And yes, I know him quite well, a really great guy. Nothing but good things to say about him.

This is outstanding Mark - I've built many challenging vacs over the years and thought I had all the techniques I needed. However, your really informative tutorials are very valuable and I'm keenly taking notes.

Thanks for taking the time to document your build for us - I'm sure vacform novices and experts alike are taking a great deal from this.

Tom

Tom, thank you very much! I truly appreciate your comments, they really do mean a lot! As I've mentioned before, there are some fantastic folks out there with some great advice (you being one of them). When in doubt, I turn to what others have made work in the past. I can't take any credit for the techniques I'm using.

I'm about to start working on trimming up the floor, and hopefully starting work on the floor on the flight deck. The plan for that one is a simple one, with just floors, leaving enough room for the future nose wheel wells, MX-20 EO/IR camera, and the bomb bay, while still leaving enough room in the nose for the appropriate weight:

What the actual nose weight requirement will be, I wont know until the kit is complete. so the plan will be to cut the radome off the nose halves, and continue the build without them. This will also give me good access to build up the MX-20 and mount it when the fuselage is complete and painted, without worrying about masking certain things off and possibly damaging the camera. There is quite a bit of room on either side of the nose wheel well to add weight as well, but my hope is that by pushing the weight as far forward as possible, I can keep some of the weight down, rather than stuffing the fuselage and turning this into a 10lb model. She'll be heavy enough on her own, no need to push it.

The other reason for this is that although it would be absolutely fantastic to show the gear in the nose, aside from the MX-20, I can't take reference pictures of the RADAR and build up the kit as I would have hoped. The problem we model builders have. That, and a CP-140 with the nose radome opened and tilted up makes the Aurora look like a grinning gap-toothed fool when looking head on.

More to come soon, and again, thank you very much for following along. Your feedback, advice, and comments are greatly appreciated.

Mark.

[Trojan Thunder]

Still watching and taking notes for a future big vac build.

[Aurora Mark]

Thank you! Hopefully I wont disappoint. What are you planning for your future big vac?

I've continued with the main cabin floor, just to finish it off. The glue has been setting for over 24 hours, so it was simply trimming the edges, sanding them down, and then making sure that everything still fit, and thankfully, it does!

Work then went onto the floors in the flight deck. There are two floors that need to be made to give the flight deck. I've quickly drawn out what I'm working on here:

The main cabin floor ends at the step, and then there is what I've called the "Flight Deck Floor" or what the FE's chair is mounted to. Above that is the Pilot/Co-Pilot floor, which, as you guessed it, their two chairs are mounted to. The "Wall" is the forward limit of the floors, and will also be a former to add strength to the front of the aircraft. This is also what the MX-20 will be mounted to.

So, first things first, I wanted to measure out how high up the step was:

Repeating this for both, they were then marked off onto the larger former:

The heights were then marked off inside the fuselage:

And then paralleling the main cabin floor, the floors were drawn out inside the fuselage half:

From here I used the same method for the floor shape as I did with the rear end of the tapered main cabin floor:

This was done with the upper floor as well, and then the cardboard pieces were traced onto plasticard and cut out:

So, that's the three main floor pieces. All that is left is to get the layout of the upper floor, or rather, the cut out measurements in the center of the floor, and then once done, the two floors can be assembled together.

I did think about having the main cabin floor extended before, however, the overall length and "steps" of the flight deck and the main cabin would prove to be extremely long and difficult to handle when building up the details. For this reason, I'm going to use the natural break between the flight deck and the main cabin to my advantage, and will handle both areas completely separately from one another. This will also help a great deal when it comes to building up all the small details of the flight deck (and given that both the overhead and aux emergency exits will be open on the flight deck, combined with the large windows, I don't want to spare any expense on details up in the front office.

More to come soon!

Cheers,

Mark.

[Joel_W]

Mark,

Your continuing tutorial on the interior flooring was written in a style and level that even I can understand. While I don't build vac kits, many of your techniques and procedures can be directly applied to my kit builds.

Joel

[Aurora Mark]

Joel, thank you very much! I really enjoy posting in this manner. It also helps me out a great deal when I go back to see just how I did something. Especially if there's two sides that need to be done the same, it's always a great way to go back and check my numbers. I'm glad you're enjoying it!

Not much done today. The CMK control surfaces arrived today, so that has now distracted me as I'm trying to finally get that one wrapped up. None the less, the radome was cut free today.

The first thing I needed to do was mark out exactly where it'll be cut. Given that it is not only an angled cut, but the non circular shape really caused a bit of fun (it's more of a squashed egg shape). So, first thing was countless tape-line attempts being made, until I finally realized what I was doing wrong. I measured out where the cut passes parallel with the tip of the nose. Figuring that distance out, I had a good midway point, and with that, taping up to the top and down to the bottom wasn't a problem at all:

And looking straight down, not too bad of a cut at all. The trick was to use a fine saw with a very tall blade (I have one that is about 2 inches tall). Working it carefully to maintain the right perpendicular angle on the fuselage, it was a bit slow going, but the cut was without any hiccups:

And here are both fuselage halves without their nose cone:

So, now I'll be able to easily add weight to the nose once the kit is complete, and be able to build up and mount the EO/IR camera without concern, while also being able to look down the fuselage to make sure that everything is lining up nicely.

Thanks again for looking, more to come soon... ...maybe... ...depends on the Il-2 and how that comes along. I need a bit of a break from straight white plastic anyway. Cheers!

Mark.

[Trojan Thunder]

Thank you! Hopefully I won't disappoint. What are you planning for your future big vac?

...

Mark,

I am enjoying you very measured ( pun intended) way you figure out the shapes for your build. I usually just hack away at a piece of card until it looks the right shape :D

The large vac? Well after seeing Tom's work on his C-17 and your's on this build I found a Combat Models C-17 on Evilbay and got it for a good price, so I might have a crack at it. I have plenty of reference for it!

[Aurora Mark]

Thank you kindly. I found that by measuring out a few times, it really went a long way to one good cut, and then just some fine sanding with 600 grit along the edges to get things to fit. Right now, I'm in a bit of a bind... I ran out of the plasticard I'm using. Tomorrow though, it's off to a LHS here, to pick up some plasticard for underfloor framing, as well as brass, brass, and more brass, to start working on the box frame for the wing spars. I'm still planning out a design for that, but I'm actually pretty excited to get working on the dihedral/spar on this one.

The box is going to be fairly straight forward, spanning the width of the fuselage from wing joint to wing joint. The height will be the bottom of the floor I just made, to the bottom of the fuselage. The spars themselves, I'm still not sure if I want to make them from a rectangular box shape, or from a hexagonal tube. I'm just taking a bit of a break from the design work on it right now to write this up. I'm thinking the rectangular box would be best to use, having the actual spars fixed inside the wings, and then just sliding into the fuselage box itself. We'll see. The trick will be light weight but strong, with little flexibility. Some, but very little.

As for the C-17, congrats! That's awesome! It's fantastic to see so many people building the 4-Fan Trash-Can... ...Looking forward to watching that build when you get started! As for me, it's back to the drawing board. I think this is a good example of square peg, round hole, lol.

Thanks!

Mark.

[Joel_W]

Mark,

Your description on how you cut the nose off using a fine tooth tall saw hit me like a ton of bricks. For ages I've been using my old exacto saw about 1 inch in height, and always wander off course on big cuts. So I'm going to head to a local tool supply and to the saw section, looking for a fine tooth carpentry saw. Might even buy two for different heights.

Joel

Edited December 31, 2014 by Joel_W

[Hornet14]

Still chugging along with this one I see nice work keep it up!

[Barneydhc82]

Joel: Forget the hardware store variety. Get a UMM ultrafine modelling saw for very fine accurate cuts.. Check out my Tracker butchery using Dymo Tape and the UMM saw. It is one of the best tools for this type of work

Barney http://www.barneysairforce.com

[Joel_W]

Joel: Forget the hardware store variety. Get a UMM ultrafine modelling saw for very fine accurate cuts.. Check out my Tracker butchery using Dymo Tape and the UMM saw. It is one of the best tools for this type of work

Barney http://www.barneysairforce.com

Barney,

Thanks for the heads up. I have a small order just about ready to be placed with UMM-USA, and will get one of their saws.

Joel

[Aurora Mark]

Joel, Barney,

I do use the UMM saw and tape for straight cuts as well, however, for a complex curve like this, where I have an angled cut on a cone shape, the taller saw worked as the better option.

There is no single tool that does it all, and having options where one can use the right tool for the job is the way to go.

Just my 2 cents.

Work has started with the brass spar pieces, but as it'll be a multi day bit of work, I'd like to post the job start to finish. So, hopefully a good update soon.

Cheers,

Mark

[Aurora Mark]

Still chugging along with this one I see nice work keep it up!

Oh yes good Sir, definitely still chugging along with this one. Thank you for your comment (and I apologize for missing it before).

Work has certainly continued, and I had mentioned that I wanted to do it all as one update, but, well, there's a lot, and I'd like to be able to go into a few details (especially with the hit/miss issues), rather than breeze through it. So, here we go.

I wanted to have a spar that had the right angle for dihedral, and could be two pieces, rather than three like the actual aircraft spar would have been. So, measuring things out, I found the dihedral angle from the guys at the maintenance shop to be just about 5 degrees. Keeping with this, in order to obtain the right dihedral with just two pieces, I would need the spar to have enough of an angle to clear all the internal plastic of the fuselage, while still being able to have the right shape.

This is just a quick sketch done on paintbrush to show a few key angles, and what I needed to consider. It's a much more sensible version than the countless papers that were on my desk by the time I figured things out:

Angle A (the green line) represents the true dihedral of the wing where it starts, at the wing/fuselage joint just after the wing fairing. This angle is 5 degrees.

Angle B (the blue line) represents the angle of dihedral of the bottom of the wing, which has a slight taper up, 5.19 degrees.

Angle C (the red line) represents the angle of dihedral expanded into the center-line of the fuselage, maintaining true wing dihedral, at the lowest point while clearing the wing fairing structure, 4 degrees.

The need for Angle A is very self explanatory. The need for Angle B was to ensure that the angle was shallow enough that there would be no noticeable difference between the angle at the bottom of the wing, the true dihedral, and what could be achieved with an actual spar (shown with Angle C). In other words, I wanted to make sure that I could glue the bottom of the wing to the spar pieces and still have a decent dihedral, where the space would be made up with shaped plasticard shims. The other option would be to raise the spar higher, make it shallower, and have it glued to the top of the wing.

The top of the wing had a dihedral angle of 3.75 degrees. It would have been easier to do, however, for the spar to be glued to the top of the wing, then extend down to the center of the fuselage with the same angle, it would have taken up more room than I was willing to give, between it and the floor. So, bottom of the wing it was.

This handy little template was made up. In measuring out the angles. The upper black angles represent the wing dihedral of 5 degrees (what it would be if it were started right at the wing root), the red line is what the spars will be matched up to, which will be 4 degrees out from the center line:

These are the brass pieces I'll be using to construct the spar box:

The first part was to construct the spars. So, the angle was measured off of the ends of the segments of the spars - here you can see them marked off - and were cut off with a hobby saw:

The pieces were then butted up and measured against the angle guide to make sure it was true. The smaller piece you see with the V-Cut was used as a temporary join, so that I could mock up the entire spar structure without having to solder anything. It would be replaced later on with a 1.5 inch section that would ensure that the spars would stick together:

Here is the first spar piece soldered together:

The second spar was constructed, and then using the flat plate that was cut to width, bent in the centre at 4 degrees, and soldered to the spars top and bottom. These plates now prevent the twisting and flexing, and move the forces of the weight of the model away from the center joint, spreading it over the spars:

As you can see the spars have also been cut down. The will reach out to about 1/2 inch beyond the no. 2 and 3 nacelles, allowing enough room to solder the plate between the spars that the main landing gear legs will be mounted to.

So, that is the spar box. It still needs some cleaning, however, I'll do the final cleaning once those last two plates (angled off to be flat) are soldered on.

Mark.

[Aurora Mark]

Next up was to get a strong mounting point and spar face-piece (for lack of a better phrase) to have this brass piece mounted solid to the aircraft. The trick was to ensure that the joint was both strong, but in a place that would prevent inadvertent flexing of the fuselage or wings with the weight of the kit. So, the wing roots on the inside were my first choice.

As you can see in this picture, they are crisp, flat, large, and just perfect for the task:

With the shape of both port and starboard inner wing roots being different from one another... ...to get the right shape, the first thing I did was add tape in there, and push it right into the edge:

Next up with a DULL knife I went over the tape until it was cut free. I say dull knife blade, as I wanted to cut just the tape, and not the plastic:

From here, the tape was moved over to a piece of hard cardboard paper:

The cardboard was cut out, then trimmed until it fit just right:

Here are both port and starboard pieces measured out, and you can see the difference in shapes:

Next up will be using these templates much as I did with the floor pieces before, but I will be cutting a 2.0 mm piece of plasticard to fit into the wing root area. Once those fit just right, small rectangles will be cut for the spars to protrude through, and then some fine measuring will be made to ensure that the thick plasticard has just the right amount of opening for the spar pieces.

More to come soon. Thanks as always for looking.

Cheers,

Mark.

[Aurora Mark]

The most difficult thing now that the spar box has been constructed, is to ensure that everything lines up properly within the wing. I want to make bridge plates between the spars, so that the weight of the entire body of the model (aside from the weight holding the nose down forward of the ole tipping point) is moved straight down over top of the main wheels. Yes, no matter what I would have done, the MLG would take the weight of the model. True. But, my plan is to have the spar box move the load, not the plastic fuselage/floor/wing joint.

What I want to prevent would be... well, let's take the 1/48 Revellogram B-17's for example. The fuselage wing joint has two tabs that lock in, and slide forward on the wing root. The two tabs on each wing locking and sliding into place share the weight load with the outter edge of the airfoil shaped fuselage/wing joint. The joint is one of the best I have seen in large aircraft with low/mid wings. The landing gear takes up a significant portion of the weight. But imagine dropping the model a little too hard, or just downward pressure from the fuselage; the wings wont split - the fuselage will right at the bomb bay. I want to stay far, far away from any chance of this happening.

With the 1/48 B-29, which has a spar box in the kit, the load is shared by both the plastic spars, and the fuselage/wing joint. The spars spread the weight of the model nicely within the wings, and also add a superb way to securely mount the large wings to the fuselage. Further to that, both the main gear leg and the drag links mount directly underneath either one of the two spars, so there is no risk of any downward force or weight causing the wing to twist overtime. At least that's what my little peanut figures is the way to go.

My problem with this wing in the CP-140 is that the main gear leg doesn't actually sit directly underneath either of the spars. So, the bridge plate will allow the MLG to mount securely between the spars, and all the downward force from the body, through the spars, will move vertically through the MLG. I think I've over-complicated things far too much... to the pictures!

First step was to figure out exactly how far out the bridge plate needs to be. So, needing a few measurements, I started with the centre of the fuselage out the inside of the wing root:

From here I just worked my way outward. The next big ones were the distances of the inner and outer edges of the engine nacelles:

Although as mentioned before there are a number of ways to skin a cat, if you find yourself building this 1/48 kit, and want my measurements for the spar work I'm doing here, here they are:

So, from the centre of the box, the outside edge of the bridge plate will be 117mm:

All the measurements marked out on the spars:

And a mock-up of where the spars will line up within the wing once it's assembled:

Well, that's about it. Next step will be to line up exactly how far forward or back the spars will be, cut some windows, and then it is off to the "solder-shop" one more time.

Thanks for looking.

Mark.

[dams301]

Very impressive and instuctive work Mark. I take somes notes for my build and surely do some purchase next week

[phantom]

Serious work!

[Joel_W]

Mark,

Your thought process is just amazing, and is dead on from that last picture. The key as I see it is that the bottom plate be the exact width of the fuselage minus the thickness of the walls on both sides. the width of the plate being the front and back of the wheel wells seams like logical placement points, and as you pointed out, a structurally sound base for the landing gear.

Joel

[Aurora Mark]

Very impressive and instuctive work Mark. I take somes notes for my build and surely do some purchase next week :thumbsup:/>

Thank you very much! I am happy to hear that my posts are helping folks out there. Makes the how-to/photographs worth while!

Serious work!

Thank you!

Mark,

Your thought process is just amazing, and is dead on from that last picture. The key as I see it is that the bottom plate be the exact width of the fuselage minus the thickness of the walls on both sides. the width of the plate being the front and back of the wheel wells seams like logical placement points, and as you pointed out, a structurally sound base for the landing gear.

Joel

Joel,

Thank you kindly for your words. The plan was to have as much room as possible on the spars afforded to the top and bottom plates, to allow for rigidity. There is still some flex in the structure, so that it isn't 100% stone-solid, and this was to allow for anything that happened to the model in regular handling and moving. I wanted to prevent the shock from any bangs or bumps be taken up completely by the plastic.

The next step with the actual bridge plates wont come until I have the spars seated inside the fuselage, protruding from the wing roots. When I have that, I will be able to take a very close look at exactly how much space there will be between the spars, and the top of the main gear wells. They aren't exactly a rectangular box on the real thing, but rather a fairly dynamic shape. The key will be to have enough of a bridge plate made (forward and back) to give a surface to mount the gear well to, without cutting into the shape, or rather, the open cavity in the actual gear well.

Right now, I'm going to be working on two things, first is to set the fuselage up for the floors, by gluing in a "ledge" for the main cabin floor to sit on, along with the flight deck. After that, as this kit doesn't have any alignment pins, I will be making those as well. Not pins, but just some plasticard that will be glued along the edge of the fuselage halves to allow me to join them together, tape them up, and then work on filling in any gaps created when I removed them from the backing-sheet. More to come soon!

Thanks as always for looking.

Cheers,

Mark.