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Jamie @ Sovereign Hobbies

Vietnam CSAR - Lockheed HC-130P "Combat King" and Sikorsky HH-3E "Jolly Green Giant" in 1/72

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I've made a start on a new model which will be something I never really do - a diorama of sorts but really it's two model aircraft. I've had to depart from my preferred 1/48 scale for this for various reasons but let's simplify it down to kit availability.

 

The ultimate aim is to try to recreate a scene like this:

74ae3697-a79e-4e7e-a528-ed37596a67f3.jpg

 

I expect the readership is well familiar with the USAF's Combat Search And Rescue (CSAR) efforts which really came to maturity during the Vietnam war. The Sikorsky S-61R model in USAF service as the CH-3 was modified with long range tanks, refuelling probe, pilots' seat arm, winch and some defensive guns and became the HH-3E, nicknamed the Jolly Green Giant. They didn't and couldn't work alone though. They were still relative sitting ducks to ground fire, expected to fly into a hover in an area where a fast jet had been shot down. They flew in pairs, a high ship providing cover and a low ship which went in to pick up the downed airman/airmen. They usually had an escort of around 4 Douglas Skyraiders which flew under the nickname of "Sandy" which would provide heavy suppressive fire support for the helicopters. The whole operation was initiated, supported and coordinated by the crew of the Combat King however - the HC-130P would patrol and listen on the US military's radio frequencies monitoring ongoing air operations. As soon as they heard communications that suggested a friendly aircraft was in trouble the CSAR machine was warmed up. The Combat King crew would direct the rescue aircraft to the scene but also provided refuelling services to the fairly short-ranged Jolly Green Giants.

 

The models then - I'm using a Whirlybird kit of the HH-3E which is almost entirely resin with a fret of photoetched brass. Unlike their earlier S-61N conversion which used a Revell donor kit, the HH-3E is a complete kit. Good then. The HC-130P is going to be provided by Italeri, with HC-130P conversion parts from David J Parkins' Flightpath, with photo etched details (mainly to get the flaps which, as can be seen above, were normally extended to allow the big Herc to fly slow enough for the helicopter to keep pace and take on fuel) and the correct Alison T56-A-15 engine nacelles from same. I still need the air to air refuelling pods from Flightpath and they're not available right now but David, if you're reading, I'll be keeping an eye on your website for them coming back into stock. It'll be a while before they hold up proceedings though.

resized_df22c0cf-007c-404c-ba6e-07d847b7

 

Never one to be content however, I have decided to attempt to make this much more difficult. I've never been impressed by clear plastic discs with blurry blades and the like, so to try to get a good impression of movement, I've decided to electrify this little ensemble. That's going to be easier said than done... Apart from any thing else, when you've actually seen things like the helicopter (or at least are familiar with its family members) things like relative RPMs begin to matter, within fairly broad reason. When photographed, the relative blur achieved by an camera will be more telling than just looking and since most people will see this through the results of a camera, I wanted to make a reasonable effort during the parts procurement process to try to get it close-ish.

 

I've known 3 Hercules pilots, and have no way of contacting any of them so I've had to guess at what is probably a sensible propeller RPM for a C-130 flying straight and level with flaps down - and my guess is that 1200 RPM isn't going to look out of place. I ordered 4 of these for the Herc:

591b137a-d2b7-42e9-a675-22807ed68118.png

https://www.ebay.co.uk/itm/DC3V-1200RPM-Micro-Mini-6mm-Planetary-Gear-Reducer-Motor-Precision-DIY-Robot-car/254151008187?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2648

 

These are approximately 17mm long and 6mm in diameter. The solid resin engine nacelles are, I believe, a benefit here since I can drill the nacelles in my pillar drill and get all the motors and thus all 4 propellers on the same axis. It would look dreadful if they all had different up/down/side thrust. Everything needs to be straight and aligned properly.

 

On to the helicopter for now though. I needed to measure up what I had to work with, and that meant cleaning up the fuselage halves:

resized_fdee6d05-3830-4135-9a33-3f3a1071

 

resized_6544d92a-0121-42a6-9970-3358745c

 

resized_f2578f76-1272-43a6-a66d-74b211f2

 

The fit is pretty good, but there is a mismatch on the top of the fuselage to deal with later - but it doesn't affect what I need to know now:

resized_6d39d586-726f-4f4b-a29b-56c339ad

 

resized_051486dc-3f72-433c-b77a-2ab42ee3

 

resized_91afbc70-0d6a-4356-959e-fc8f23d3

 

I have a bit of space to work with for the main rotor, but still the smaller the better - I don't really want a huge silver monstrosity gleaming through the cabin windows:

resized_1fbda37d-d669-4ea2-8b38-31f35fdb

 

The tailrotor however is a real issue:

resized_abee11bc-f3aa-413f-831f-d5c06275

 

I have better data here (I think) about what speeds I want, but in truth that probably makes me less satisfied with whatever I get in the end! I have my father available who was licensed on the Sikorsky S-61N and has all of his Sikorsky course notes. I'd love to show some of the amazing reference material inside, but Sikorsky never miss an opportunity to sue people and the course notes have prohibitions on unauthorised disclosure all over them, so you'll have to take my word for the rest. Not knowing any S-61R drivers, but believing the powertrain to be very similar to the S-61N, my dad's course notes state that 100% on the mainrotor is 203 RPM. The same drawing shows that the power take-off for the tail rotor runs at 3030 RPM at 100% and that the 45deg gearbox at the bottom of the pylon is a 1:1 gear ratio. The final drive gearbox to the tail rotor itself has a ratio of 2.4375:1, making the tailrotor run at 1243 RPM at 100%.

 

The best I could find that would fit in the fuselage for the mainrotor was this 242 RPM geared motor, measuring 16.5mm long by 6mm diameter:

b56062f6-03a5-4263-b78c-2682333c7838.png

https://www.ebay.co.uk/itm/253771137237

That's at 3v so I've also ordered some little potentiometers to, hopefully, tweak that down a touch.

 

Compromise is the key here. I considered asking someone to design and 3D print me tiny bevel gears and sit a motor in the pylon coaxial with where the transmission shaft would be on the real thing, but then I found these:

a8a1ccc6-e3ca-4ce5-9e38-fa0b59c32413.png

https://www.ebay.co.uk/itm/DC3V-3-7V-4-2V-Ultra-mini-Coreless-Motor-3-2mm-12-2mm-Vibration-Vibrating-Motor/283101330780?ssPageName=STRK%3AMEBIDX%3AIT&var=583506556671&_trksid=p2057872.m2749.l2649

 

They are tiny little things 3.2mm x 12.2mm overall including the shaft which has a vibrating counterweight attached, so I've ordered 2 of them incase I ruin one. This should just fit in there. I expect it spins far too fast for what I want, but I will mock it up first with a potentiometer and see how low I can get it - but really I think I'll just need to take what I get as this really seems to be the absolute bottom end of what's readily available on the market just now.

 

Since I had the stuff out, I made a move on the sponsons. Whirlybird provides sponsons with separate end plates; one with floats for the HH-3F "Pelican" used by the Coast Guard, one plain as used on some of the CH-3C utility versions and one with the pylon for extended range fuel tanks.

resized_bb808dc2-3bc3-49b4-bc85-c6889308

 

The fit isn't great unfortunately. I spent a while trying to make sure the pylons were aligned and looked like they would be at the same angle of incidence as each other - I don't want one fairly long, spindly fuel tank pointing up and one down!

resized_488b11df-d5e1-436b-a14a-5384860f

 

I've had this stuff for a while but have never used it, so thought I'd give it a go

resized_71a74e84-3c13-4701-af3e-45d4afda

 

It's like Milliput but seems a bit softer and easier to knead/mix than my packets of Milliput. That said, my Milliput has always been quite old whenever I've used it - mixing epoxy putties always seems a real faff so I'll use solvent types normally. For resin here though this is probably more suitable.

resized_b90f4c16-ea09-45cc-8e59-0595ac32

 

 

 

Thanks for looking in. This won't be fast paced - and indeed I need to wait for motors to arrive, but I will work away at it along with my other projects. I'm not always in the mood for shaping / painting / photo etch / sanding / scribing so I like having different models at different stages of build and pick up whichever I'm in the mood for. I'm not a linear person.

 

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I’m fascinated by the mechanical aspects of this build and will be following closely. 

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The props on the Herc spin at 1021rpm (with your -15 engine). The Allison is a constant speed engine - doesn't matter how slow or fast the aircraft is travelling, the engine/prop spins at a constant speed. With different speeds and power settings, the prop just takes bigger or smaller bites of air to maintain that 1021 rpm.  6500hrs on Hercs, some numbers you don't forget.......

Is this the kit that has the external refuel probe for the RAF Herc version? I will be interested to hear your thoughts on it.

Edited by isaneng

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1 hour ago, billn53 said:

I’m fascinated by the mechanical aspects of this build and will be following closely. 

 

Me too! I haven't decided how to hold the models up, but I'm thinking of sacrificing a small element of scale fidelity and making brass tube mounting sockets in 2 separate places for each model; one set to hold it up from underneath like a traditional model stand as per ancient old kits, and maybe another set on one side such that with a "forced perspective" viewpoint they would be invisible. I am wondering if I can make the stands the electrical conductors as well so that the batteries can be external and replaceable.

 

I have decided to take a high risk strategy.

 

Perhaps without intending to, @Jordi challenged me to correct the missing chines low down on the fuselage:

On 5/20/2019 at 1:05 AM, Jordi said:

Italeri completely missed the ‘chine’ that all C-130s have at the level of the cabin floor, making it a flattened circular shape in cross section.  The sharp edge casts a hard shadow.  Not easy to fix unfortunately.

 

We certainly need a new family of C-130 kits to replace the nearly 40 year old Italeri ones!

It's important to understand that I am, fundamentally, a wazzock and there's nothing quite like suggesting something can't easily be done to make me want to go and do it.

 

So, there's a photo on the post linked just above, and here's what the model looks like:

resized_d4e0519a-4b6c-47d5-90fd-6d18af13

 

At this point, @Stew Dapple will be thinking "if I'd known you were going to just ruin it I'd have kept the damned thing myself", but sorry Stew - I shall have to owe you a Hercules and I shall buy you a beer :D

 

The first thing I thought when I saw the photo that Jordi posted was that I need some way to retain a straight chine because if I end up with a wiggly chine, the hard shadow will advertise the fact that I'm a fool and should have left it well alone - even if the aircraft will be flat matt paint. I decided that brass rods would provide that definition in a way that was difficult for me to sand into a wiggly line, so I glued some on

resized_3bd1cf4f-8860-4391-ba0e-eaea3bf3

 

To pack out the fuselage above and below giving me something to blend in and out, I cut out some plasticard

resized_3f036d6d-8bdb-435a-819f-d2351e74

 

...and glued it on. Argh - what a mess! It's ok though, because once the Tamiya Extra Thin (this is one of the only things I am able to successfully use the stuff on) has cured and the styrene hardened up, the Infini Model sanding array shall be deployed and this mess will be tidied up a bit, with the definition of the chine being relatively robust thanks to the brass.

resized_3e39b568-aa0a-447b-a12b-93bca5c1

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12 minutes ago, isaneng said:

The props on the Herc spin at 1021rpm (with your -15 engine). The Allison is a constant speed engine - doesn't matter how slow or fast the aircraft is travelling, the engine/prop spins at a constant speed. With different speeds and power settings, the prop just takes bigger or smaller bites of air to maintain that 1021 rpm.  6500hrs on Hercs, some numbers you don't forget.......

Is this the kit that has the external refuel probe for the RAF Herc version? I will be interested to hear your thoughts on it.

 

Thank you! :D

 

That's not too far away and with another variable resistor I should be able to get close to that. I have an optical tachometer from my R/C model flying alternate existence so can try my best to get to 1021 RPM. I'm not sure I can synchronise them all in phase though :whistle:

 

Also - I now know of four Hercules pilots!

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Attention duly grabbed Jamie and comfortable chair prepared.

 

I'm going to ask one question though - shouldn't there be a second HH-3E ? :)

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4 minutes ago, Richard E said:

Attention duly grabbed Jamie and comfortable chair prepared.

 

I'm going to ask one question though - shouldn't there be a second HH-3E ? :)

Yes there should - but one kit is the thick end of £70 😂

 

We shall be pretending that the second ship is hanging back a little 🤐

 

@Duncan B would have me adding all 4 A-1s into the scene as well...

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3 minutes ago, Richard E said:

Attention duly grabbed Jamie and comfortable chair prepared.

 

I'm going to ask one question though - shouldn't there be a second HH-3E ? :)

I did spend an interesting and amusing evening trying to get Jamie to buy several Skyraiders for this madcap scheme.

 

It's finally happened, all those paint fumes have gone to poor Jamie's head. I look forward to seeing how this one progresses.

 

DB

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An excellent project, look forward to the engineering solutions as they occur

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13 minutes ago, Duncan B said:

I did spend an interesting and amusing evening trying to get Jamie to buy several Skyraiders for this madcap scheme.

 

It's finally happened, all those paint fumes have gone to poor Jamie's head. I look forward to seeing how this one progresses.

 

DB

 

We could make this a group build effort and assemble it in its totality at Telford this year for a big BM photo opportunity :D

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8 minutes ago, Jamie @ Sovereign Hobbies said:

 

We could make this a group build effort and assemble it in its totality at Telford this year for a big BM photo opportunity :D

It had crossed my mind to offer to build the A-1s but fitting the motor would be a pain. You really think all this will be ready for Telford in this decade :) ?

 

DB

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3 minutes ago, Duncan B said:

It had crossed my mind to offer to build the A-1s but fitting the motor would be a pain. You really think all this will be ready for Telford in this decade :) ?

 

DB

I'll admit my track record isn't great. I am as slow at the model bench as I am swift on the tarmac 😎

 

How about you build the downed F-105D instead. Can't quite manage scale distance but you can put it on the AMS club table and I'll put the Air to Air refuelling in Hall 1. 

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Just now, Jamie @ Sovereign Hobbies said:

I'll admit my track record isn't great. I am as slow at the model bench as I am swift on the tarmac 😎

....and I am a paragon of prolific plastic production!!

 

DB

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Damn you Duff, I am now on Scalemates checking out A-1s again :frantic:

 

DB

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2 minutes ago, Duncan B said:

Damn you Duff, I am now on Scalemates checking out A-1s again :frantic:

 

DB

4No. Hasegawas please.

 

A-1Es would have been nice for variety, but if you're building 4 of them then it's probably best to start with good kits.

 

Lucky for me there's only one HC-130P involved 😂

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A fascinating project Jamie I will be adding this to the list of Sovereign Hobbies builds I will watch out for  ;)

 

I saw a very realistic Sea King HC4 at Huddersfield a few years back with the rotors turning

 

When I asked about the tail rotor he smiled and said the motor for that fitted inside the actual rotor head moulding

A mobile phone vibrator buzzer is a rotating but very tiny footprint device he said, "and that is what is in there"

 

So I have just ordered one to use as a sacrificial unit

 

I will strip it down and see what he was talking about, maybe a better bet than that long one you are looking at

 

Should be here by midweek

 

This kind of unit

 

s-l400.jpg

 

 

 

This is very tiny

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This is a very interesting build, Jamie. I love the combination. It evokes many memories of images of this combination in magazines of The time :)

 

Martin

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8 hours ago, perdu said:

A fascinating project Jamie I will be adding this to the list of Sovereign Hobbies builds I will watch out for  ;)

 

I saw a very realistic Sea King HC4 at Huddersfield a few years back with the rotors turning

 

When I asked about the tail rotor he smiled and said the motor for that fitted inside the actual rotor head moulding

A mobile phone vibrator buzzer is a rotating but very tiny footprint device he said, "and that is what is in there"

 

So I have just ordered one to use as a sacrificial unit

 

I will strip it down and see what he was talking about, maybe a better bet than that long one you are looking at

 

Should be here by midweek

 

This kind of unit

 

s-l400.jpg

 

 

 

This is very tiny

 

Hi Bill,

 

I must admit it never occurred to me to place the magnet inside the hub. Hmm. I'll be very interested to see what your purchase results in. It will probably reach you before mine reach me! I ordered the Hercules motors about a week ago but only placed the order for the helicopter motors last week.

 

Another challenge I need to overcome is getting a suitable coning of the main rotor disc. Flat or slightly droopy is fine for sitting on the ground but the big Sikorsky's develop a noticeable cone as the collective is pulled on.

h-3-a3c.jpg

 

 

And a couple more of the pair together I found :)

ch-3-DF-ST-82-07960.jpg

 

ch-3-DF-ST-82-07983.jpg

 

 

 

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Coning in flight is nothing like as prominent as when the lifting loads come on is it?

 

I find, when doing jobs like this, that a thin layer of superglue underneath can stiffen the plastic almost invisibly If there is a need for stiffness to be imparted


The thin layer of cyano will counter the usual tendency of polystyrene to flop under gravitational forces

 

If you have the blades turning the extra centri-something forces will aid you too no doubt

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Hi Jamie,

 

Seriously challenging project; I shall be watching agog as this progresses.

 

Dumb question: how warm will the motors get?  I'm thinking:

 

heat + resin = 😫

 

Regards

 

Martin

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6 minutes ago, mike romeo said:

Hi Jamie,

 

Seriously challenging project; I shall be watching agog as this progresses.

 

Dumb question: how warm will the motors get?  I'm thinking:

 

heat + resin = 😫

 

Regards

 

Martin

 

Not a dumb question at all...

 

As hinted above I've done quite a bit of r/c flying and some of that has been electric. In those circumstances a fair bit of heat is generated, but they are producing considerable power - 300 watts to 2 kilowatts is not uncommon. The thrust they generate for a model which can achieve car-like speeds (over 100mph is common for electric ducted fan "jets") requires this power and if, for arguments sake, a 1KW model aeroplane motor has an efficiency factor of 0.8 then the wasted 200 watts is disposed of partly by noise and mostly by heat.

 

That would be a real problem.

 

Here though, I don't plan on generating any thrust and therefore the torque will be as close to zero as possible and therefore the power produced will be as close to zero as possible. The lower the power the motors have to develop, the less waste heat there is to worry about. In addition, the likelihood is that these will only ever be run for short periods at a time.

 

Hopefully it's manageable, but you're right - it's something I am thinking about. I have an infrared thermometer, so I can do some testing with, for example, one of the C-130 motors in a nacelle before building up the full model to check that there isn't a worrying build up of heat.

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Good question

 

In consideration I have noticed several rotor or propellor turning displays over the entire display at Telford which seem to maintain their rotation without wavering all weekend

 

Not that I have used resin so much, I'd certainly do the task if I had the old Revell HH3 to do it with

 

(Wanders off considering adding the HH3 to my 'must buy' list for any shows I attend this year...)

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1 hour ago, perdu said:

I'd certainly do the task if I had the old Revell HH3 to do it with

 

(Wanders off considering adding the HH3 to my 'must buy' list for any shows I attend this year...)

 

I think I have most of one somewhere - if I can find the important bits you're welcome to it.

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