Boeing Stearman Model 75

I

Ivan

Charter Member
Hello Gentlemen,

It appears that my initial assessment of the flight model for the Red Stearman was not correct.

As manufactured, the Stearman 75 only had TWO Ailerons on the four wing tips and was known for a very leisurely roll rate.
Modern Stearman, especially airshow birds typically have been refitted with FOUR Ailerons and have a much faster roll rate.
Now keep in mind that in appearance, the Red Stearman DOES have FOUR Ailerons or at least has the appearance of four Ailerons.

Apparently one model of the Stearman 75 was equipped with a 450 HP Pratt & Whitney Engine and that is actually a pretty good amount of power for aeroplane that probably doesn't weigh over about 3500 pounds loaded and that would explain a pretty high rate of acceleration on the runway.
The Textures do show a 450 and a Pratt & Whitney symbol.....

The Yellow Stearman has a much nicer roll rate but behaves much worse from a handling standpoint.

- Ivan.
 
Which one?

Hello, hello, Ivan and Smilo!

Interesting, useful details, Ivan, as regards the different models. Thanks!
I hadn´t delved into all the information yet. The plane definitely has an appealing shape, and will be a pleasure to build.

I was trying to download the magazine av history article mentioned to get at the drawings, and the page even says it´s free, but even though there are several download options, some mischief is afoot that prevents the download.

Anyway, there are other drawings available. However, as there seem to have been several different models and motorizations, perhaps it would be a good idea to define exactly which one we want.

There was even an armed export model called Stearman 76!

The number of horses up front (not under the bonnet, because there wasn´t one!) can go into the .air file.
The number of ailerons won´t matter for buiding. They can be put on the textures, and in the Roll parameters in the .air file!
So, for a basis, it appears then, that either of the two existing .air files could be fine, depending on the model wanted.

So, to start a new thread will be nice, and we can even write the exact model into the Title!

Smilo, it seems you rather like the one in the av history article, so it it´s not too much to ask, perhaps a scan would be fine. The scale is no problem because it can be figured out from the spec sheet included in the scan. That will also provide the exact model number, if that´s the model you should be interested in.

Cheers,
Aleatorylamp
 
according to the article,
the model 75 originally
came off the line with, either,
a Continental R-670,
a Lycoming R-680,
or a Jacobs R-755.
the Pratt and Whitney R-985 wasp jr
was a post WWII swap out.
 
seems, you were posting as i was typing.

will get the scanner set up shortly.
...unless my son calls
for me to pick him up from work.
either way, i will have the drawings up by morning.

since we're talking two models,
how about a docile military trainer,
and the hotter, modified civilian?
i believe visually, they look the same.
except, for paint, of course.
the devil will be in the air files.
 
Hello Smilo,
It seems you were posting while I was writing just now - the other way around from what happened before!
OK, PT-13 and PT-17 - one AF99 model for two motorizations and two paint schemes.

Were the souped-up civilian version to be cowled, the nose would be correctly shaped, and it would be a modification of the uncowled build, so we´d have 2 AF99 models. No problem! The cowl can be seen as flush with the fuselage on the photos.

For the moment, I haven´t seen a real plane with the cowl of the red version. Of course, I may be wrong, but to be on the safe side, I´d go by the available photos.

Update: Necessary Correction. I am wrong! Both types of cowls exist or existed!
The cowl on the red version IS in fact CORRECT.
I´d already thought it strange that the author of the model would have made such a mistake.
I found 1 photo showing such a cowl, which must be the cowl offered as an option on early types, although the aircraft was flown without it more often than not.
Consequently, it seems only newer post-war civilian or acrobatic versions had cowls flush with the fuselage.

So, there are 3 different shape options for the AF99 model. a) No cowl, b) old cowl and c) new flush-cowl.

Update: Re. .air files:
I can´t guarantee anything better other than to CFS1-doctor up the two existing FS98 .air files with CFS1 engine records and trying adjust flight behaviour a bit, because FS98 files do behave a bit differently.
Maybe Ivan can help us there when the time comes...

Anyway, do let me know if you are interested in a model with either of the cowl shapes, apart from the cowl-less one.

No hurry about the scanning.
Cheers,
Aleatorylamp
 
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too funny...no sooner had i stood up
to attach the scanner, than the phone rang
and i was off on a couple hour jaunt.
so it goes.

since it is now, 01:35 in your neighborhood,
this should be waiting for you
when you get up...good morning,
i hope you like it.

as for the cowling question,
i prefer the look of the exposed radial.
yes, it makes the project more complex,
but, it's not something often seen.
 

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Hello Smilo,
I couldn´t sleep and went looking for further details on this plane. I was just about to go to bed but looked into the post.
Excellent, the scan you sent - thanks very much!

OK on the exposed engine - I´ve done it before on the early German Klemm monoplane and on the Ernst Udet Flamingo Biplane, so I was planning to do it anyway for the new Stearman.

I was just wondering if you would want the souped up version to have a cowl - either old fashioned or modern - and was asking just in case, but just like you, I prefer the cowl-less version. So, ONE AF99 model it will be, for 2 versions: a military trainer and a civil hot-rod. Excellent!

Update:
The unit on your scan is a PT-13D, with a nice Lycoming R-680-17 engine delivering 330 Hp. Wow!
Other PT-13´s and also the PT-17 seem to have had more standard 220 Hp engines.
So then: CFS1 engine parameters would be almost the same as the AT-9 Jeep, which had 295 Hp Lycoming R-680-9 engines.
The FD were supervised by Ivan, so at least, engine power on the CFS1 Stearman .air file would not be too difficult to get right.

Perhaps you would like to do the honours for the new Stearman own thread, like you suggested. Also, maybe it would be good to transfer the posts as of #1443 inclusive to the new thread. This is the post just after you suggested having an own thread fot the Stearman 75.
Moving the posts before would perhaps be a bit contradictory. What do you think?

OK, I´m off to bed now...
Good late night!
Aleatorylamp
 
Stearman Data

Hello Gentlemen.

The Boeing Stearman 75 in military configuration could have been either a PT-13, PT-17, or PT-18.
All had radial engines in about the 220-225 HP range at 2100 RPM with a gross weight of just a touch under 3000 pounds.

The Pratt & Whitney R-985 was sometimes fitted as a replacement engine.
450 HP @ 2300 RPM (1 Minute limit) for Take Off
Normal Maximum 310 HP @ 1950 RPM.
Gross Weight is around 3650 pounds.

This is such a popular aeroplane that information can be found in many places though one has to sanity check.
I found several plausible pilot reports / instruction guides in a matter of a few minutes.
The FAA Type Certificate number is A-743 and has more information than you are likely to need.
Just be careful in interpreting data because some of the current limitations may not have been the original military specified limitations.

- Ivan.
 
as has been discussed
in the 'Conspicuous by Their Absence' thread,
a new project is in the works,
the Boeing Stearman Model 75.

the above posts were moved
from the 'Conspicuous by Their Absence' thread.
 
Maybe 3 Stearman-75 models?

Hello Smilo, Hello Ivan,
Well... thanks Smilo, for setting up the thread. I thought it should be "yours"
because you sparked the idea for this new project.

And again thanks, Ivan, for your additional research, this time on the even more
powerful 450 Hp Pratt & Whitney R-985 engine option.

So, there are basically now 3 different motorizations:

A) A 225 Hp Continental 670-5 or -K engine, which would be
the "slow and easy" Army trainer (PT-17).

B) The 330 Hp 9-cylinder Lycoming powered version in the PT-13D scan.
This could also be a Jacobs R-755A1 base line 7-cylinder engine,
or its R-755A2 300 Hp variant,
or an R-755E even more uprated with reduction gearing. (PT18 or PT13)
Any of these would make for a more fun military trainer model with a bit
more of a bite, possibly the Navy version.

C) The 450 Hp Pratt & Whitney R-985 Ivan mentioned.

As the most powerful engine was also frequently fitted to post-war machines,
perhaps Option "C" would be for the civil souped-up version, which would leave
the military one maybe with the specs in the scan you supplied, or maybe we
could have two military ones, Army and Navy with 220 and 330 Hp, respectively,
and the civil one with 450 Hp would be a third variant?

I mean this just as suggestions to provide differences between the versions, that
would all have the same build. It will not affect the model build itself, so we can
do it whatever way you like!

Cheers,
Aleatorylamp
 
so many choices,
so many decisions,
so little time.
and it's up to me?
gosh...and we haven't even talked about
the crop dusters that saved the beast from extinction.
what was that "can of worms" comment?

seriously, as i see it,
make her too docile
and no one will want to fly it.
(well, maybe once or twice)
but, then again....
it would be nice to show the progression.

a more powerful, challenging
military trainer is in order.
yes, the Lycoming version.

and, of course, the civilian Pratt & Whitney.

in a dream world, three versions.

this is all contingent on you,
the builder and how much do you want
to mess around with visual accuracy,
building 6, 7, or 9 cylinder versions.
then, there's the air file work.

as you should know by now,
none of these tasks are in my department.
all i can be is a cheerleader
beta tester and critic.
that is, unless, you want to send me the afx files
and i could sequence the parts in ad2k.
in that case, build her as complex as you want.
BUT, then again, you know how speedy i am.
 
Hello Smilo,
Not to worry, it´s no problem!
There´s enough time, and the can of worms only referred to Ivan´s comment about some SCASM-improvable shapes on the existing red version which he hinted at, were one to try and SCASM improve the red one to have exposed cylinders.

Thus, I´d personally prefer to build a new one, as you also voiced.
So, as I am going to be the AF99 builder, and I also like the Stearman very much, I would want to make it as per your preferences, because you had started off the idea.

We have already coincided that it would have exposed cylinders, so a cowled version is discarded.
Also, I´ll gladly abide by your choice of which model to supply, because it was your idea to have a good model with exposed cylinders, - a more modern build than FS5 model, and an exposed cylinder model in the quality of the red version.

Must rush, I´ll continue later.
Cheers,
Aleatorylamp
 
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Hello Again, Gentlemen,

From what I have been able to find, there was yet another version: the PT-27 which was the designation given to Lend-Lease versions to Canada.
Also, if you intend to build them as they left the factory, the 330 HP version appears to be a re-fit and not a factory produced version.

I found a pretty good site (actually a bunch of sites) that describe the different models and also looked through the entry in my copy of Jane's and there was no mention of a 330 HP PT-13.
That isn't absolutely conclusive, but it does seem odd to build many similarly powered aircraft models and then build one primary trainer with 100 more HP.

If you intend to stay with AF99, I have an idea for designing the exposed cylinder Radial Engine as a single Component.
I do believe however that you will end up with a much better model with AD2000 instead of AF99 because of the ability to face Polygons the direction you want them, so that would allow a properly shaped engine instead of the minor distortion that would be required in AF99.
I would build a demonstration model of the engine if I had a working Development Computer at the moment.

- Ivan.
 
funny you should mention the pt-27.
according to the article,
about 300 were build
with several modifications.
the most prominent being a canopy.
BUT, the navy intercepted the canopies
for their own cold weather use.
the Canadian planes were shipped
back in short order.

to be honest, which model(s) are built
doesn't really matter to me,
as long as there is a less powerful
military version and the civilian hot rod.
heck, i would be more than satisfied
with just the military Lycoming version.

Stephan, just for fun,
build the engine block
and the number one cylinder.
then, ship me all the parts.
i think i might be able
to put an engine together.
who knows, it might be fun.
 
Hello Smilo, hello Ivan,
So, the main AF99 model to be built is decidedly the one mentioned in the article that Smilo is so enthusiastic about.
Jane´s doesn´t mention it but other sources do - I don´t mind, it won´t affect the building of the model.

The PT-13D had the Lycoming R-680-17 9-cyl engine, and 1450 were delivered to the US Navy, and called N2S-5.
Also, 353 were delivered to the Army as Model E-75. So, it would sound as if they were fitted with these engines ex-factory.

Updated Paragraph:
So as not to sound cutting with my comment on the Lycoming powered units, I want to expound on the fact that the P13-D model did exist, and that the 300 and 330 hp versions may not have been retrofitted, although it is quite possible that some were.
There seem to have been several sub-groups of the PT-13 type, all with Lycoming R-680 engines, totalling 2141 models.
It must be that Jane´s probably didn´t mention the sub-groups, only the main group.
The US Army got the following different types of Lycoming-powered P-13 units.
PT-13 - 26 initial production models with R-680-B4B engines
PT-13-A (Model A-75) - 92 units delivered 1937-38 with R-680-7 engines
PT-13-B - 255 units delivered 1939-40 with R-680-11 engines
PT-13-C - 6 PT-13B units modified for instrument flying
PT-13-D - 353 units delivered, PT13-A equipped with R-680-17 engines. Model E-75

Updated Paragraph:
The US Navy got the N2S model, Known colloquially as the "Yellow Peril" from its overall-yellow paint scheme, and these were the Lycoming-powered ones:
N2S-2: R-680-8 engine. 125 delivered .
N2S-4: 99 US Army units diverted to the U.S. Navy, plus 577 newly-build aircraft.
N2S-5: R-680-17 engine. 1,450 delivered to the U.S. Navy.

So I´ll build the base version with 9 exposed cylinders. I´ve done 5 and a 7 cylinder ones before, with no great bleed problems. OOooppsss... No FS98 bleed problems, to be exact... Anyway, let´s see how it goes. I´m game.

I can also offer a 7-cylinder one, if we should want a 220 Hp Continental R-670 PT-17, I´m not worried, but I gather there´s not much demand for this one, judging by what Smilo has said!

The civilian version will definitely have the 450 Hp Pratt & Whitney R-985 Wasp Junior engine, also 9 cylinders, so in reality only one AF99 model is needed.

Updated paragraph:
...and more about the civil hot-rod:
A popular approved modification to increase the maximum takeoff weight and climb performance involved fitting a larger Pratt & Whitney R-985 Wasp Junior engine and a constant-speed propeller.

I was trying not to worry about AD2K, I´m afraid, but on the other hand, being a single engined job without engine nacelles on the wings, it would be easer in AD2K model than a twin. However, I know what´s going to happen if I go into AD2K with this one now, so I´m a bit reticent about it. There´s enough on the AD2K table here with the twin that´s underway (it´s not discarded by any means) to complicate it with another model.

If you insist, Smilo, I will send you a cylinder. No problem. Let me get the side and top profile of the whole plane into AF99 first, and then I´ll make a cylinder.

Must rush again, sorry! There´s no rest for the wicked.
Cheers,
Aleatorylamp
 
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no worries, Stephan.
it's the weekend and unless i'm mistaken,
it's family time as well.

...and don't worry about ad2k.
this is your af99 project.
relax and enjoy yourself.
i was merely thinking with my keyboard.
i'm in no rush for engine parts
or, for that matter, any parts.
there's more than enough for me to do
with the L10 wing and nacelle.

also, if you want to put together
a 7 cylinder engine, i say, go for it.
i certainly won't turn my nose up at it.

it just started raining,
which is very welcome.
it's been a few months
since we've had a good downpour.
 
Hello Smilo,
I haven´t done any building at all, just looking at the different options.
As you say, family time is also good: To fight the sweltering heat, I´ve been busy making pallet furniture - two seats and a sofa with a table - for the inner courtyard to sit around when it gets cooler in the evenings (23 decrees C), or during the day under a big umbrella in the shade. The courtyard is walled, I think with the shade it heats the house less. Right now it´s 10 a.m. and there´s already 24 degrees C outside, and rising again. Must get the big umprella up quickly!

Navy and Army Stearmans had 2 different attractive colour schemes, and perhaps they can both be used. The blue-yellow one and the "Yellow Peril" one. However, to make it more interesting, I´d thought of having one of them with the 330 Hp Lycoming engine and the other with the 220 Hp Continental, hence a second build with a 7-cylinder engine.

Then there are a couple of attractive liveries for the civil hot-rod. Perhaps the re-and-white one will come through best in the sim. So there would be 3 Stearmans! I think that would be great.

Hello Ivan,
Your offer of explaining some goodies about making 7 or 9-cyl radial engines less bleed-riddled with AF99 sounds very attractive indeed, and I´d be very much looking forward to hearing them from you, even if they should involve some light SCASMing, which I think I could handle.

Now we´re off to the farmer´s market...
Have a nice Sunday with your families!
Cheers,
Aleatorylamp.
 
nope...sorry, too hot for me.
your morning temperatures
are pushing my comfort level.

the past week or so has cooled down here.
been hazy overcast, due to fires up north,
but that is dissipating and for me,
the rain is always welcome.

i would have been surprised to hear
you've already started building.
lots of research to get done first, right?
the design seems very straight forward
with the only real difference being
engine cylinder numbers and size.
as i said, the difference is in the air files.
which ever you decide to do is fine with me.
any others would be an added bonus.

now, it's all about the waiting game
and patience, patience, patience.
 
Hello Smilo,

24 Degrees Centigrade is only 75 Degrees Fahrenheit.
Around here, it has been more like 31 Degrees Centigrade by around 10 AM.
I would welcome only 24C around here right now though it HAS actually been around there the last couple days.
I expect it will get back to the 95F by mid afternoon in a few days.

It is a pity that the subject you wanted was the Boeing Stearman 75. If it had been a Curtiss P-6E or a F11C, I would not have hesitated in starting another project. Both are on my build list. The Stearman 75 doesn't look entirely unattractive to me, so with the research I will certainly be doing, perhaps it will gain greater appeal.


Hello Aleatorylamp,

I am pretty sure your 330 HP engine is a modern retrofit with fuel injection and probably electronic ignition and other modern cool stuff that would not have been found in a 1940's aeroplane. It is like finding a modern Spitfire Mk.V or a Hurricane with a 4 blade propeller. Yes, they exist today, but that wasn't how they were built originally.

I believe I can build a basic 7 or 9 cylinder exposed cylinder radial with a single Component in Aircraft Factory 99.
The question is how nicely I can refine the shape within the Parts Count limitation (50?) of a single Component.
Do you know offhand how many Parts are allowed in a single Component? I don't want to fire up the Development Machine just to check that.
I get the impression that its days are numbered and I want to have it available to pull off the data and programs that don't exist anywhere else before it dies.
AF99 probably still won't die even when the Parts count in a Component is exceeded, but as you already know with the BV 141B, sometimes the problems show up elsewhere. If the limit is only 50 Parts, I might need to use two Components for the Engine for the 9 Cylinder version which is still less than the typical three Components I use for a Radial Engine in other designs.

I would like probably to start off with the 9 cylinder version because it is the one more likely to push limits, so I guess I need to go figure out which engine we are discussing and what its external dimensions actually are.

- Ivan.
 
Hello Ivan,
Well, it got a lot hotter towards midday and early afternoon, around 30 C, but now at 6 o´clock it´s down to 25 C again.
Of course, it´s nowhere as bad as last week where it was at 41 C for quite a few days. That WAS bad...

I wouldn´t have expected it to get so hot around your area, as you are in quite a northerly zone. Every 100 years or so it´s also the opposite, I gather, when Niagara Falls freeze up! The logical interpretation is climatic cycles, and pollution doesn´t have any positive effects either, but there is some controversy about that, so I don´t know.

Anyway, the Stearman engine:
I doubt that there was any electronics or fuel injection, and I know there wasn´t a supercharger.

I´ve seen that some versions had the same engine as the 1941-1943 AT-9 Jeep: 295 Hp Lycoming R-680-9 or 300 Hp Lycoming R-680-13.

Presumably the R-680-17 on the PT-13-D Stearman was further souped up with more compression perhaps (no supercharger though). I know there was an R-680-E3A with 330 Hp and 7:1 compression, but I can´t find info on the R680-17.

I´ll let you know the building details for the radial engine as soon as I get them out of the 7-cyl Udet Flamingo biplane I built some time ago. I think it was 30 parts in one component, apart from the pushrods. For a 9-cyl one it would be 36.
Of course done in left/right halves it would be a bit different.
I´ll confirm later, also the size etc. Thanks for your interest!
Cheers,
Aleatorylamp
 
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