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Hello @Killingholme ... Thanks for the tip. I usually paint the wheel wells early in a build. I hate having to paint them afterwords. Nothing like getting green/ZCY/ or whatever color smeared on the bottom color. Because I paint them early i usually stuff them with some form of masking. Sometimes i have a touch up to do , sometines i get lucky and everything is good. 

 

Dennis

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Hello folks sorry for the stoppage on this. I am waiting on parts for my Soviet Hurricane. Once the hurricane is ready for paint i will paint them together, since they will both have the DFS. Might possibly have a Spitfire as well ? Im down to just this and the Hurricane so i may start a Mk.XIV from Legato ? Which is marked as AZ inside the wings. Im guessing the Legato’s were AZ Kits that were re-popped. 

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Sadly i will have to say i will see you on the 29th. Between all the Doctors and the long distance driving involved this week. I haven't had the energy to get in the office since Tuesday. I will have to spend tomorrow an hour away at a family member’s and taxi them around. They are having many more issues than i am. Sunday i have to clean for our houseguests on Monday. I will not have any chance to get to work on anything.  Im already going through withdrawals from the Glue & paints. 

 

Dennis  

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  • 3 weeks later...

Hello everyone ... Happy to say i can get back to work on this finally. Our Houseguest has gone home today and i reclaimed my office. I will begin painting the DFS on the Airacobra Mk.1 for this and my Hurricane for the Brits abroad group build on Monday. Probably do both Grey’s. Then i can spray the green on Tuesday or Wednesday. See you soon with some updates. 

 

Dennis

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Hello everyone ... I was able to get to the RAF Dk. Green today. A9ZTfJ6.jpg

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It needs a touch up of the grey near the starboard wingroot. The mask i used wasn't looking good after i pulled it up. I decided it needed some touchups. I will give this a touchup & a clear coat tomorrow and then its onto decals.

 

Dennis

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On 8/28/2018 at 10:40 PM, Procopius said:

Hey Dennis, 

 

I pulled out my copy of Air Enthusiast August 1971, which has an article on RAF Airacobras, and while most photos show nothing there (except two parallel rail-type structures), this one, of the second delivered airframe, shows what appears to be black boxes of some sort:

 

43618668724_5c5a168d9c_h.jpg2018-08-28_09-32-00 by Edward IX, on Flickr 

 

The engine is directly below that shelf-like area, though, so I'm not sure what that was. A cutaway drawing of the Airacobra I in the same source puts the radio receiver and transmitter inside the fuselage abaft the airscoop, almost directly in front of the fin.

 

Interestingly enough, the RAF found in trials that the Airacobra could out-turn a Bf109E and catch it in a dive of over 4,000 feet, but that it couldn't out-turn or out-climb a Spitfire Vb. At 15,000 feet or below, it was faster than the Spitfire Vb by about 18 MPH, but of course over France at this time they were routinely fighting at 24,000 feet (which must have been very unpleasant), where the Spitfire was 55 MPH (!) faster than the Airacobra I.

The difference in airspeed advantage was the result of the lack of a two-stage supercharger in the P-39. It’s critical altitude (maximum speed) was about 12-15,000 feet. After that, its level-flight top speed fell off steadily. For a comparison of the speed versus altitude for airplanes with single-stage and two-stage superchargers, see http://thanlont.blogspot.com/2008/05/engine-makes-difference.html

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Not quite.  It was the lack of a turbocharger rather than a two-stage supercharger.  I have not seen a fully convincing description of the thinking behind this, and the similar lack of a turbocharger on export P-38s, but at the time the turbocharger was considered very advanced technology, it  was having problems getting into mass production, and was seen as something the US had to protect for its own use.  I suspect that at the time the decision was made affecting the P-39, it was foreseen that there were simply not going to be enough turbochargers to go around all the designs queuing up for them, and it was the P-39 that lost out.  

 

I've seen it said that the French chose the non-turbocharged P-38 for compatibility with their order for P-40s, and we just tagged along.  Whereas there is some logic to this, it isn't completely convincing and has the air of making the best deal available.

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6 hours ago, Graham Boak said:

but at the time the turbocharger was considered very advanced technology

I don't think it was the turbocharger technology per se that was the problem, Graham, I rather suspect it was the metalurgy that had been developed to make it work that the US wasn't keen to export. By the late 30's turbines had been around for over 50 years and were well understood, as was supercharging of IC engines. The problem at that time was finding metals with properties suitable to be used at the extreme temperatures encountered in a gas turbine compared to the more moderate temperatures in an operating steam turbine. This was also a problem Whittle was experiencing developing the gas turbine.

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The US were ahead of all other nations in the turbocharging of aircraft engines, and had them in service in small numbers on the B-17.  No doubt one key contribution was the metallurgy, but that doesn't explain why Bell was prevented from developing the original P-39 design which had the turbocharger,  for the USAAC itself.  It wasn't a case of preventing overseas nations from having it (as perhaps was the case with the P-38)  because the US weren't going to get it either.  This is always described as a decision made by General Arnold, rather than that by US engine companies.  The massive increase in numbers expected to be required, and the necessary ramp-up in production for B-17s and P-38s (not to mention the following B-24s and P-47s) would cause problems in supply.  The P-39 would have made too many demands too soon on what was seen as a limited resource in the short run, and it was considered the least promising design in the long run.

  

It should also be added that the RAF were to receive a small number of early B-17s, which doesn't fit with any overall ban on the technology.

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3 hours ago, Graham Boak said:

The massive increase in numbers expected to be required, and the necessary ramp-up in production for B-17s and P-38s (not to mention the following B-24s and P-47s) would cause problems in supply.

Agreed, new metsls in initial limited supply would limit production and make prioritisation fo certain aircraft necessary at least initially.

3 hours ago, Graham Boak said:

It should also be added that the RAF were to receive a small number of early B-17s, which doesn't fit with any overall ban on the technology.

True, the USAAF were keen to see how these performed in combat, seconding aircrew to the RAF as well; but not so keen to supply the Norden bomb sight to go with them though.

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15 hours ago, Graham Boak said:

Not quite.  It was the lack of a turbocharger rather than a two-stage supercharger.  I have not seen a fully convincing description of the thinking behind this, and the similar lack of a turbocharger on export P-38s, but at the time the turbocharger was considered very advanced technology, it  was having problems getting into mass production, and was seen as something the US had to protect for its own use.  I suspect that at the time the decision was made affecting the P-39, it was foreseen that there were simply not going to be enough turbochargers to go around all the designs queuing up for them, and it was the P-39 that lost out.  

 

I've seen it said that the French chose the non-turbocharged P-38 for compatibility with their order for P-40s, and we just tagged along.  Whereas there is some logic to this, it isn't completely convincing and has the air of making the best deal available.

It is true that the XP-39 included a turbocharger. However, it presented an installation problem in the small airframe (the P-38 housed its turbochargers in the tail booms; the P-47's was located in the lower aft fuselage) and it was thought by some, based in part on a NACA wind tunnel test, that the turbocharger installation in the P-39 resulted in an increase in weight and drag relative to a supercharger. The U.S. Army Air Corps therefore gave Bell a pass on the altitude requirement of 20,000 feet for top speed when Larry Bell claimed that the production P-39s, powered by an Allison V-1710 with a single-stage supercharger, would have a top speed of 400 mph at a critical altitude of "approximately" 15,000 feet. It would have been more accurate for me to state that the P-39 lacked sufficient supercharging above 15,000 feet compared to airplanes with two-stage superchargers (the Merlin-powered P-51 for example) or turbo-superchargers. (n.b. A supercharger's compressor is mechanically driven; a turbo-supercharger or turbocharger's is driven by the engine exhaust.)

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Hello Everyone ... I added the yellow leading edges and the sky band tonight. 

LLYyP3w.jpg

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Decals tomorrow for both this and my Hurricane build. I have a rather busy week with Doctors, Gov’t. officials, and The wife has Phys. Therapy 2 times this week. 

 

Dennis

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Hello All ... Well i got the decals on this today.

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I had to repaint the codes as the decals were a particular shade of sky blue that i wasn't sure about ? So i just used a sky greygreen color to match the fuselage band and spinner.

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You will notice i goofed and used the wrong red dot in the fuselage roundel. I wound up painting the ones on the lower wing as the tiny dot wouldn't have looked right.

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I will attack the serial #’s this week as i have to cut up some numbers. Then its on to the weathering,  all be it light as these weren't used too hard. 

 

Dennis

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Hello again ... Well codes & landing gear are on, the exhaust is painted up. Will put the exhaust on and finish the landing gear doors tonight, and will then post some photo’s. Weathering & satin coat tomorrow or friday and then shes done. 

 

Dennis

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Hello ... I did the little bit of weathering today. Mostly a light exhaust staining and a little bit of dirt near the landing gear bays. I then sprayed a satin coat today i will post photos but they will look very similar, just a touch duller than the last set. ⬆️ Then its the canopy, antenna, rollover bars, & pitot. I figure by saturday or sunday on the outside. 

 

Dennis

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