RC-135S Cobra Ball - WIP - Part I

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RC-135S Cobra Ball - WIP - Part I

Joined: June 28th, 2007, 7:33 am

October 24th, 2010, 4:55 pm #1

While the painting process of my A-50 Mainstay is going on, I use the dead times due to paints curing to start my next project .
To interrupt the series of Russian aircrafts instead of the M-50 Bounder I decided to have a go with the conversion of the AMT 1/72 scale kit of RC-135V into an RC-135S Cobra Ball as it appeared in the late seventies operating from Shemya AB .
With the invaluable help and infos kindly provided by some Hyperscalers I hope to be able to fullfill the job .
Here are a couple of pics of kit parts clean up .





Any further pics or infos very wellcome .

TIA and Bye


Alberto Accumolli

G.M.B. BRANZACK
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Joined: October 21st, 2005, 2:28 pm

October 24th, 2010, 5:43 pm #2

Hi Alberto,

I have a -135A backdate project about 60% done. Wing- Fuselage mate hasn't taken place yet, mainly because if i do i cannot keep it in the box.

Here are my findings:

1) The plastic in general is very soft and highly prone to warpage. Many of the delicate raised details (like the bands on the aft fuselage) will sand off rapidly if you aren't careful.

2) The fuselage doesn't have enough locator pins. You need to add flanges to the fuselage halves to ensure a more positive joint. Same goes for the floor. Its long, floppy, and there just isn't enough built into the kit to really beef it up and secure it in place.

3) I didn't incorporate a metal spar, but i did find i could make the wings straighter and eliminate the "droop" problem, by using liquid cement and a "splint" made from two pieces of square brass tubing and stationery clamps along the wing trailing edges when gluing the outer lower sections to the upper panels. Personally, i don't think the AMT wings have enough dihedral when viewed from the front when compared to drawings. If the real aeroplane had this much droop, the maximum permissible crosswind component would be 10 knots.

4) The lower surface of the wing has a distinct "kink" in the vicinity of the inboard engine pylons. Unfortunately it sort of cuts in a angled line when you get to the trailing edge. Its important to get the outside surfaces as level with each other as possible here; this is gonna involve some reengineering of the inner wing surfaces to they can be made to dovetail with each other.

5) The locating pegs on the engine pylons are small and not too helpful. Locating the engine pylons is frustrating, keeping them all parallel to each other, and at a 90 degree angle to the front chord line of the wing.

6) I think it would be easier to install and fair the engine pylons to the wing prior to installing the wing to the fuselage.

7) The fit of the front edge of the lower wing carry thru section to the mating edge of the lower fuselage is poor.

I don't mean to scare you, but this kit started off with a good concept but was betrayed by some lazy engineering and indifferent fit issues. I can provide more detail if you want to discuss this with me off board.

HTH,

david
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Joined: January 27th, 2005, 12:07 pm

October 24th, 2010, 5:45 pm #3

While the painting process of my A-50 Mainstay is going on, I use the dead times due to paints curing to start my next project .
To interrupt the series of Russian aircrafts instead of the M-50 Bounder I decided to have a go with the conversion of the AMT 1/72 scale kit of RC-135V into an RC-135S Cobra Ball as it appeared in the late seventies operating from Shemya AB .
With the invaluable help and infos kindly provided by some Hyperscalers I hope to be able to fullfill the job .
Here are a couple of pics of kit parts clean up .





Any further pics or infos very wellcome .

TIA and Bye


Alberto Accumolli

G.M.B. BRANZACK
Hi,
Here's an article how to fix the outer wing droop;

https://www.qcsrfserver2.net/avesstudio ... 0Droop.pdf

Recommended reading!

Regards
Andy K

--------------------------------------------

www.notaussiefloyd.com
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Joined: June 28th, 2007, 7:33 am

October 24th, 2010, 8:10 pm #4

Hi Alberto,

I have a -135A backdate project about 60% done. Wing- Fuselage mate hasn't taken place yet, mainly because if i do i cannot keep it in the box.

Here are my findings:

1) The plastic in general is very soft and highly prone to warpage. Many of the delicate raised details (like the bands on the aft fuselage) will sand off rapidly if you aren't careful.

2) The fuselage doesn't have enough locator pins. You need to add flanges to the fuselage halves to ensure a more positive joint. Same goes for the floor. Its long, floppy, and there just isn't enough built into the kit to really beef it up and secure it in place.

3) I didn't incorporate a metal spar, but i did find i could make the wings straighter and eliminate the "droop" problem, by using liquid cement and a "splint" made from two pieces of square brass tubing and stationery clamps along the wing trailing edges when gluing the outer lower sections to the upper panels. Personally, i don't think the AMT wings have enough dihedral when viewed from the front when compared to drawings. If the real aeroplane had this much droop, the maximum permissible crosswind component would be 10 knots.

4) The lower surface of the wing has a distinct "kink" in the vicinity of the inboard engine pylons. Unfortunately it sort of cuts in a angled line when you get to the trailing edge. Its important to get the outside surfaces as level with each other as possible here; this is gonna involve some reengineering of the inner wing surfaces to they can be made to dovetail with each other.

5) The locating pegs on the engine pylons are small and not too helpful. Locating the engine pylons is frustrating, keeping them all parallel to each other, and at a 90 degree angle to the front chord line of the wing.

6) I think it would be easier to install and fair the engine pylons to the wing prior to installing the wing to the fuselage.

7) The fit of the front edge of the lower wing carry thru section to the mating edge of the lower fuselage is poor.

I don't mean to scare you, but this kit started off with a good concept but was betrayed by some lazy engineering and indifferent fit issues. I can provide more detail if you want to discuss this with me off board.

HTH,

david
Hi David,

you are already in the list of Hyperscalers that helped me when I studied the feasibility of a model of RC-135S Cobra Ball .
Your suggestions are very helpfull for me, so I'd be glad to receive any further infos/pics/building notes from you .
Anyway I agree to continue our discussion off-board by e-mail.

Bye

Alberto Accumolli

G.M.B. BRANZACK
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Joined: June 28th, 2007, 7:33 am

October 24th, 2010, 8:14 pm #5

Hi,
Here's an article how to fix the outer wing droop;

https://www.qcsrfserver2.net/avesstudio ... 0Droop.pdf

Recommended reading!

Regards
Andy K

--------------------------------------------

www.notaussiefloyd.com
Hi Andy,

your info is quite usefull, I checked the site and got my suspects confirmed : the wings need a strong longeron to add rigidity to them .

Many thanks .



Alberto Accumolli

G.M.B. BRANZACK
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