BETA Build: Nobi's Junkers SRF 1:48 scale

[Sammuel]

rbeach84;

This is looking great. The wing and tail section are formed very clean and sharp.

Sam

[rbeach84]

Thanks again for all the kind comments. Glad you are enjoying the thread!

Quick update. I was looking at the tail skid, which is just a fold-over of left & right halves to give a double thickness skid shape. As I wanted something more three dimensional, I departed a bit by adding a bit of heavy card in between the halves which I shaped to a more airfoil shape by closing the edges around the cardboard insert. This is pure fiction of course, but I figured the designers would have gone that route for streamlining purposes. Looks like I'll need to do some color touchup on those edges...

To finish, I plan on 'wrapping' the skid with a bit of silver paper (or perhaps with a scrap of foil) to show the 'abradable' metal plate usually found on tail skids. As this occurred to me after I'd closed the aft fuselage, I didn't build in an attachment 'structure' onto the aft former. If I had, I could then slot the extra length of my skid into it for a solid mounting. Another BETA build lesson learned!

(To be con't)

[rbeach84]

All, well I took the plunge after completing the starboard wing and glued all the fuselage and tail assemblies together. I will be posting images tonight, but thought to go ahead and put out any new findings.

The second wing went together well enough, though there were some minor differences from the port one, mainly the under-root didn't seem to want to 'close up' as near the centerline as the port wing. Also, the wing tip assembly reinforced the idea that the internal tip plates are a bit too large at the front and side edges of the profile as I had to trim it back a fair bit to close up the side seams. Also, because of the need to 'pull the parts' out to the edges, the contour of the tip pieces were 'flattened' more than I would like. Easiest solution, if the plate parts remain unchanged, would be to simply trim 1.5 mm or so from the edge that glues to the rib, thereby shifting the plate's profile towards the centerline.

After I completed the wings, I found I hadn't paid proper attention to the wing 'washout', so looking at the wings from the rear shows one side with the wing twisting 'up' re: the leading edge while the other twists 'down' (which would be more correct as a depiction of 'washout' - tip angle of attack should decrease when compared to the root so the inner wing stalls first, retaining airflow and control across the ailerons... trivia alert!) I don't know what would best address this issue during construction, though an alignment jig would probably help somewhat, as might a secondary spar - which could also establish the proper amount of wing washout.

I kind of skipped over the dorsal fairing & canopy a bit. The slot & tabs that I incorporated worked fairly well, but you have to take care that the placement and width of the slots will not constrain the fairing parts from "fine position adjustment." Mine were a tiny bit off, so a little bulging resulted. *But* having the tabs made the fairings look and align so much better - more positive location. If Nobi decides to incorporate the slot-tabs, he will be able to make it more precise than what I did.

The 'canopy' pieces went together okay, but show my lack of experience a bit as the windscreen sticks up slightly above the canopy proper. Part of this was due to the tabs being (as noted) less precisely located. Looks okay for the BETA, I would judge the fairing and canopy parts properly sized.

I have started on one of the engines, which are essentially a cylinder within a cylinder (both ends.) Fit of skins to formers was very good, with the formers needing a small amount of sanding reduction to fit into the rolled skins. I did find that the leading part of the outer cylinder should be left to last as the inner (tapered) cylinder doesn't want to be inserted from the front. Also, the intake "bullet" - the tapered 'inner' cylinder - actually has too many parts, making it too long. However, I just left off the rearmost section and it looks just right... so no problem just deleting the extra section. (This may have occurred during design if Nobi was considering inseting the front former of the main body deeper in to give the intake extra 'depth' - but not something that really is needed.) I surmised that the 'prototype' engines would have been centrifugal flow like Whittle's engines, so short and squat with shallow intakes would be fine...

If I've not said it enough, I am having fun with this kit and learning a lot.

[rbeach84]

Here are the images to go with my prior post - hope it illustrates what I wrote about:
First, the fairings and canopy. The 'tab' left out on the windscreen was to remind me to say "not needed"... I used just two near the joint. Bit of wrinkling from my shaping, plus you can see the mis-match at the top - probably my fault!

[rbeach84]

I didn't really have any pix of the wing being finished up, since it was done just like the other side, previously covered. So, instead here is all the fuselage 'buttoned up'. Kinda Jimmy Durante in aspect, isn't it?
The last image was taken sans flash to show the shapes a bit better. Try and remind me to shoot a pix or two of the underside of the wings.

[rbeach84]

This group shows the points I've discussed about the engine construction (so far...)
I started with the center section, a parallel cylinder. Nice fit with the formers, eh?

Then I worked up the outer intake parts, adding (as you can see) a glue strip I sketched up on spare card. This worked fairly well, but the smaller part (the leading edge of the intake) was apparently a tad too large such I had to trim the length to close after I'd glued it mostly in place. So, it looks a bit sloppy. Forewarned next time.

In the background is the former/intake detail which I laminated as double thickness of card - the heavy cardboard wasn't really needed. It fits into the intake assembly. However, you should (which I *did not*) assemble the intake "bullet" first before gluing in the former...

[rbeach84]

...Since the bullet is almost too large (*if* you leave out the extra section as previously noted) to 'shove in' from the front. I did manage it, though, and it looked pretty good.

The first image is where I experimented with adding a glue strip again - unfortunately, the work turned out wasted as this is the section that was unneeded... ah, well.

You can see the height of the 'bullet' with and without the discarded section. As the last two images show, it looks much more like the 'target' design with the 'shorter' stack.

Next time, I'll finish up the exhaust end of the engine for you and take a swag at the pylon.

(To be con't.)

[Alcides]

The complete fuselage looks very nice. I've to say it remembers me more a cartoon plane than a real one.

I understand you didn't it because was a beta but the only point to improve I can see in your build is the white paper borders. Your build looks very smooth with the borders painted Could be a really amazing model.

[rbeach84]

Originally Posted by Alcides

The complete fuselage looks very nice. I've to say it remembers me more a cartoon plane than a real one.

I understand you didn't it because was a beta but the only point to improve I can see in your build is the white paper borders. Your build looks very smooth with the borders painted Could be a really amazing model.

Alcides, thanks for the comments - "cartoonish" was my impression also, which is why I double checked with Nobi about the scale. Funny to think of, but this is a paper model of a "paper" airplane! As such, issues with weight & balance probably were not worked out completely, so the "big fuel tank nose" (as I think of it) would have been reworked if actually built... early jets were thirsty, so big fuel tanks were a concern. But all that mass ahead of the center of gravity would have been a *lot* to deal with, especially with the relatively small wing and tail surfaces!:p

I plan on building it again using my lessons learned to get an even better result. I hope to incorporate:

- Separate control surfaces
- Cockpit & wheel wells (to go with...)
- Landing gear
- Clear canopy
- Minor details such as radio antenna, pitot tube, detailed engine exhaust
- 'Weathering'
- Added access panels (one of which I will add to this build to cover up my 'water stain' on the nose.)

Tall order, I know, but it all looks "do-able". If I can actually 'draft' the detail parts, I'll post into Downloads, or pass to Nobi for inclusion with his kit (his call on what to do...)

[rbeach84]

Just tested, it glides okay (without the engines on the wings, that is...)