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Old 05-30-2010, 02:55 PM
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rbeach84 rbeach84 is offline
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BETA Build: Nobi's Junkers SRF 1:48 scale

Hi all, this is exciting to contribute to the forum with a test build. Chris G. has asked "Deckape" and myself to give Nobi's new design for the Junkers SRF a test drive, so I'm kicking it off with some images to show my progress so far. Deckape has scheduled to begin his build on 1 June, so he will add to the thread as he begins his findings.

Being a newbie (this is only my fourth paper model) I hope my level of technical expertise doesn't prove distracting. I am attempting, for the most part, an "out-of-the-box" build to show what can be done with the design as it was initially passed to me. Any deviations I will note while I go as well as my findings. I have already reported my findings to Nobi to date, so I am just documenting it here for the rest of the Forum's review. I hope it proves interesting. Now, what was the size limit for those images...? Ah, yes.

POST 1:
So to start with, I took the printed PDF's (100% on 8.5x11 inch, 110lb cardstock) and gave then a couple of light, misted coats of Krylon clear gloss acrylic (tip I picked up on the forum.) This seems to help the cutting a bit and doesn't appear to affect the glue strength. I allowed an hour for that to set thoroughly before starting the build.

The kit has two sheets of parts and three pages of perspective drawings to illustrate placement. No written instructions as of yet. Parts are numbered, with formers and spars having an "*" next to them to indicate either doubling or otherwise using heavier material. All these parts are co-located so it is easy to cut off the main sheet and then glue to (as in my case) heavier stock.

I glued the formers to a heavy cereal box material, which is thicker than normal because it was a "double-bag" package (Captain Crunch, as you see.) I tried using glue stick, but the adhesion was spotty so I had to 'reglue' when the cardstock came loose when I cut out the parts. I also marked the numbers on the former parts to help me keep them straight after cutting, avoiding the middle holes.
(To be con't)
Attached Thumbnails
BETA Build: Nobi's Junkers SRF 1:48 scale-img_5779.jpg   BETA Build: Nobi's Junkers SRF 1:48 scale-img_5780.jpg   BETA Build: Nobi's Junkers SRF 1:48 scale-img_5781.jpg   BETA Build: Nobi's Junkers SRF 1:48 scale-img_5783.jpg  
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In Work: Uhu02 Tinkerbell - [under Tapcho's thread] Tinkerbell - a fairy with an attitude
Nobi Junkers SRF BETA build - BETA Build: Nobi's Junkers SRF 1:48 scale
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  #2  
Old 05-30-2010, 04:23 PM
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Great!!! I'm going to follow this one with a lot of attention.
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  #3  
Old 05-30-2010, 08:33 PM
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Post 2

After getting the formers "fortified" using the cereal box (hey, fortified, get it?) I started cutting out the center holes. To start, I wasn't sure of the reasoning behind having the holes there (wasn't actually certain they were holes...) but figured perhaps it was a center of balance issue. Started with the first section of the fuselage nose, conveniently numbered "1", in assembly 'A'. This is essentially a straight tube with a former at each end (they are visible in the first image on the right side.) Because the cylinder is basically parallel sided, I did not cut the formers at an angle. Well, actually, I did cut them at a 90 degree angle as that is what is called for - I want to match the former edge to the "skin" of the tube to maximize the gluing surface. I used a sharp, new blade for cutting and an emery nail sanding stick to smooth the edges of the former, trying to be as precise as possible.

Once the formers were ready, I cut out the corresponding "skin" piece and pre-rolled it using a recycled 'chopstick' - I roll it like a rolling pin, holding both ends. Rolling on the padded table mat works well for these long cylinder parts. I made a matching glue tab, also rolled before gluing, with length adjusted for the thickness of the formers. Now I could assemble the section.

[I apologize for not having close-up images of the action, but I'm still working out how to work the camera and do something with my hands at the same time (the usual problem for us all...) I do have a remote shutter, a 'shorty' tripod and auto focus, so it is possible. For now, I'll just have to describe the action - like an old time radio broadcast ]
(To be con't)
Attached Thumbnails
BETA Build: Nobi's Junkers SRF 1:48 scale-img_5785.jpg   BETA Build: Nobi's Junkers SRF 1:48 scale-img_5784.jpg  
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Regards, Robert
In Work: Uhu02 Tinkerbell - [under Tapcho's thread] Tinkerbell - a fairy with an attitude
Nobi Junkers SRF BETA build - BETA Build: Nobi's Junkers SRF 1:48 scale
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  #4  
Old 05-30-2010, 08:38 PM
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The "holes" in the formers are very useful when you have to position them in the tube. If you don't cut the holes you can't handle them. Usually they don't get in the perfect position at the first try
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Old 05-30-2010, 08:40 PM
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Post 3

To assemble, I used this general procedure: The skins have a line running down the centerline while the formers have an "up" arrow marking. I apply glue to the top half of the former, then lay the skin to the former, aligning the centerline mark with the arrow. I then align the former with the edge of the skin part while holding it in contact with the glued portion, keeping things 'tight' and aligned for about 10-15 seconds or so. Once I'm sure it will stay, I then repeat for the other end of the 'tube'. Then I apply glue to the lower half of *both*formers and the bottom seam as well and complete the remainder of the joints. Obviously, the bottom half is a bit trickier and needs to be done without delay. Plus, the amount and consistency of the glue (Elmer’s white glue) plays a part because of the (as I call it) "soaking factor". The more 'wet' the paper is the more it can distort under pressure, so I try and minimize the amount of glue so the card retains it's strength.

Back to part #1 - I added the glue tab before attaching the formers, then as I 'rolled' the lower half around for a test fit, but after I'd glued the top to the formers I found the skin was too long to meet at a butt joint by about 1.8mm - a significant overlap. So, I carefully removed the overlap in situ and finished gluing the joint. I have the excess strip on top of the assembly to illustrate.

I then completed part #2 and it's formers using essentially the same method. I took the mating former for section 2 and carefully sanded it to match the corresponding former in section 1 to maximize the surface alignment. (This is something I got better at as I went along .) However, as section 2 is a tapering cylinder, I cut out the formers with an appropriate edge angle so the skin and 'bulkhead' met along the same plane. I also attempted to introduce a bit of 'compound curvature' by embossing the interior of the skin after rolling. I'll speak more to this later.

By this point, the wisdom of the center holes was apparent as I could reach the interior of the seams and 'press' them from inside, applying more even pressure to *both* sides, keeping from distorting the seam while sealing it.

The second image shows the top centerline mark that is the primary alignment aid Nobi has incorporated in his design. Notice how the 'arrow' on the former points to it. The sections are not glued together at this point.
(To be con't)
Attached Thumbnails
BETA Build: Nobi's Junkers SRF 1:48 scale-img_5786.jpg   BETA Build: Nobi's Junkers SRF 1:48 scale-img_5787.jpg  
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Regards, Robert
In Work: Uhu02 Tinkerbell - [under Tapcho's thread] Tinkerbell - a fairy with an attitude
Nobi Junkers SRF BETA build - BETA Build: Nobi's Junkers SRF 1:48 scale

Last edited by rbeach84; 05-30-2010 at 09:06 PM.
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  #6  
Old 05-30-2010, 09:05 PM
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Quote:
Originally Posted by Alcides View Post
The "holes" in the formers are very useful when you have to position them in the tube. If you don't cut the holes you can't handle them. Usually they don't get in the perfect position at the first try
Well, as it turned out, the "tubes" would have been too large if I had made them first and then added the formers. Don't know which was correct, so I just went with the formers as the standard as they set the contours.:D
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In Work: Uhu02 Tinkerbell - [under Tapcho's thread] Tinkerbell - a fairy with an attitude
Nobi Junkers SRF BETA build - BETA Build: Nobi's Junkers SRF 1:48 scale
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  #7  
Old 05-30-2010, 09:08 PM
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Post 4

Remaining nose sections were completed essentially in the same manner as 1 & 2. Because of the increasing taper, I attempted to apply compound curvature by burnishing the interior of the skins on my palm after I rolled them with my chopstick. This burnishing tended to 'flatten' the roll, and vice versa, so it was a balancing act to meet both goals. Also, achieving a butt joint with the curvature was more difficult as the cuts I had to make were not strictly straight. Consequently, if you look at the bottom joint line it is not nearly as neat as the top!:o

I also re-established the compound curvature by burnishing through the center holes once the sections were completed and had dried a bit. Interior access was very useful!

The third image shows the completed nose. I glued all the sections together and then formed up the nose "cap". The cap was pre-formed in my palm, and since it was sized to the original skin diameters, it also had to be trimmed. Once it was shaped and it's seam glued, I applied it to the nose tip by first 'tacking' it at the point of the centerline mark (so alignment was established) then I had to 'wrestle' the last section and the cap parts a bit, gluing incrementally until I got the best butt joint possible. Given the amount of "fettling" on the skins, I think it turned out okay.

Note, however, the amount of wobble of the underside profile due to my seam work. As I said earlier, I got better as I went along.
(To be con't)
Attached Thumbnails
BETA Build: Nobi's Junkers SRF 1:48 scale-img_5788.jpg   BETA Build: Nobi's Junkers SRF 1:48 scale-img_5789.jpg   BETA Build: Nobi's Junkers SRF 1:48 scale-img_5791.jpg  
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Regards, Robert
In Work: Uhu02 Tinkerbell - [under Tapcho's thread] Tinkerbell - a fairy with an attitude
Nobi Junkers SRF BETA build - BETA Build: Nobi's Junkers SRF 1:48 scale
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  #8  
Old 05-30-2010, 09:08 PM
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Robert,
You are doing great. I like your explanation of what you are doing
and the results obtained. Very concise. Ron
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Old 05-30-2010, 09:18 PM
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Quote:
Originally Posted by rbeach84 View Post
Remaining nose sections were completed essentially in the same manner as 1 & 2. Because of the increasing taper, I attempted to apply compound curvature by burnishing the interior of the skins on my palm after I rolled them with my chopstick. This burnishing tended to 'flatten' the roll, and vice versa, so it was a balancing act to meet both goals. Also, achieving a butt joint with the curvature was more difficult as the cuts I had to make were not strictly straight. Consequently, if you look at the bottom joint line it is not nearly as neat as the top!:o

I also re-established the compound curvature by burnishing through the center holes once the sections were completed and had dried a bit. Interior access was very useful!

The third image shows the completed nose. I glued all the sections together and then formed up the nose "cap". The cap was pre-formed in my palm, and since it was sized to the original skin diameters, it also had to be trimmed. Once it was shaped and it's seam glued, I applied it to the nose tip by first 'tacking' it at the point of the centerline mark (so alignment was established) then I had to 'wrestle' the last section and the cap parts a bit, gluing incrementally until I got the best butt joint possible. Given the amount of "fettling" on the skins, I think it turned out okay.

Note, however, the amount of wobble of the underside profile due to my seam work. As I said earlier, I got better as I went along.
(To be con't)


Looking Great
Your doing a great job the explaination of construction is very good ver self expainatary.
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  #10  
Old 05-30-2010, 09:35 PM
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Post 5

I next began the aft fuselage with the center section. This is a tapered tube and holds the wing spar - so I made sure and cut out the spar slots before rolling. I did a slightly different procedure regarding the bottom seam. Instead of trimming, I just glued the overlap, again using the end formers to set the diameter. To make the seam neater, I 'chamfered' the edges. I first tried a 'shaving' technique I'd seen on the forum to thin the edge, but I didn't have much success. So then I simply sanded the edges, and this worked okay though with some 'fuzziness' - which didn't matter being on the inside of the seam. If you look closely, you can see how the seam overlaps, plus it is not 'down the center' as a proper butt join would have been. However, as the top marks set the alignment, everything is oriented correctly otherwise.

I deviated here as I used an oversized "glue tab" of cardstock to reinforce the bottom skin. The 'tab' overlaps the spar slots, providing a little extra thickness and strength there. I've had difficulty with "wrapping" spar wings in the past, so I tend to be over cautious. In fact, this spar gave me a bit trouble by 'kinking' at the rib cutout notch. Also, the spar has a slightly greater depth than the designed slot, so there was a little distortion. This makes for a tight fit, however!:p

As near as I can tell, the spar alignment is good and the wings should be fine.
(As always, to be con't)
Attached Thumbnails
BETA Build: Nobi's Junkers SRF 1:48 scale-img_5793.jpg   BETA Build: Nobi's Junkers SRF 1:48 scale-img_5794.jpg  
__________________
Regards, Robert
In Work: Uhu02 Tinkerbell - [under Tapcho's thread] Tinkerbell - a fairy with an attitude
Nobi Junkers SRF BETA build - BETA Build: Nobi's Junkers SRF 1:48 scale
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