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-   -   B-47 1/10.2th Scale, Boeing Stratojet...In The Beginning (https://www.wattflyer.com/forums/showthread.php?t=52194)

Flite-Metal 12-11-2009 03:30 AM

B-47, 1/8.7669 Scale Boeing Stratojet, In The Beginning
1 Attachment(s)
PHASE I: The Work-Up Begins...aka In The Beginning

Does anyone have interest in the Boeing B-47?

Welcome to a B-47E-IV construction project. I and Sam Collins are working our way forward on a pair of
Stratojets. This has been an exceptionally fast ramp up from research to the initial design phase.

It is my intention to share resources to enable anyone interested in replicating a B-47E-IV to be able to
do so from this thread.

This project has grown from an original 1/8th scale to 1/10th, 1/11th, and ended as a 1/8.7669. Why?

Here's why and how... first the B-47's datum lines:

Project Preamble: Please read and determine for yourself how the following applies to you, the reader: :red:

Any and all persons reading this discussion must come to their own determination of the safety and wisdom
of emulating or replicating any and all aspects of what is described within this discussion.

This includes, but is not limited to your own decision on the safety of and whether you should be involved
in this or these activities and any processes or use of equipment related to recreating what is, or has been
discussed here-in by subscribers to WattFlyer, the host of this discussion.

Neither the author of this topic nor WattFlyer are responsible for proper or improper use of, or correct or
incorrectness of any process activity undertaken by any one or all readers of this construction thread.

*As in all modeling activities, reader beware of your abilities to either properly or improperly apply the
principals described here-in. It is impossible to declare whether this activity is or is not proper for readers
of this discussion.


Airframe #1:

Airframe #2:
WB-47B Weather (Cino Atmospheric "Sampling") Bomber :)

Airframe #3: (1 + 1 + 1 = 2)
First flight: Dec. 17, 1947 (prototype XB-47)
Model # 450: ( Built By Boeing, Douglas, Lockheed )
2 - XB-47
1,341 - B-47E
10 - B-47A
255 - RB-47E
397 - B-47B
35 - RB-47H
1 - YB-47C

Classification: Medium Bomber
Span: 116 ft. = 158.7790” @ 1/8.7669
Length: 107.1 ft. = 146.5969” @ 1/8.7669
Height: 27 ft. 11 in. = 38.2119” @ 1/8.7669
Power: Six 7,200 # thrust GEJ47GE25 turbojet
Crew: 3 crew ( original conf. )
Armament: One twin 20 mm turret, 25,000# of bombs YB-47E = 4 Cruise Anti-Radar Miss

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

Per the B-47 Assn. web site and all documentation recorded for the B-47:

The origin of the B-47 Stratojet can be traced back to the Second World War. In June of 1943, an informal USAAF request led several aircraft manufacturers to begin studies of multi-jet aircraft for fast photographic reconnaissance or medium bombing missions. On November 17, 1944, the USAAF issued formal requirements for a jet-powered medium bomber with a range of 3500 miles (3041 nautical miles), a service ceiling of 45,000 feet, and a maximum speed of 550 mph (478 knots).

Even before the USAAF began its study, Boeing had been working on the adaptation of large aircraft to jet propulsion. The initial Boeing study was a Model 424, which was essentially a scaled-down B-29 with four jet engines paired in two nacelles mounted underneath the wing. However, wind tunnel testing proved that this engine arrangement was unsatisfactory.

In December of 1944, Boeing engineers went back to the drawing board and came up with the Model 432, in which all four engines were moved inside the main fuselage to improve the efficiency of the wing. The engines were located right over the main fuel tank area of the fuselage and were fed by bulbous air intakes located beside the cockpit section.
The engines exhausted via tailpipes located on top of the rear fuselage. The aircraft still resembled a B-29, but with a much thinner wing. The USAAF was sufficiently impressed with this design that they awarded Boeing a Phase I study contract for the Model 432 proposal. The project was assigned the designation XB-47. At the same time, contracts were awarded to North American for the XB-45, Convair for the XB-46, and Martin for the XB-48.
The configuration of the XB-47 was soon to undergo a drastic change. Just after VE-Day in May of 1945, the US Army's Scientific Advisory Group headed by the famous aerodynamicist Theodor von Karman was allowed to visit German aircraft factories and aeronautical research facilities to see if any of the innovations developed there could be incorporated into American designs.

Boeing's chief aerodynamicist, George Schairer, accompanied the group. One of the items that was discovered was the results of some German research dating back to the mid-1930s on the use of swept-wings to improve the performance of high-speed aircraft. These studies confirmed independent studies carried out by NACA in the USA. The use of sweep angles as high as 45 degrees enhanced high-speed performance by delaying the formation of shock waves as the aircraft neared the speed of sound.

Word about the German research on swept wings was flashed back to Seattle, and Boeing engineers immediately stopped work on the straight-winged XB-47. Wind tunnel tests confirmed the essential validity of the German findings, and work began on a swept-winged version of the XB-47. Early in September of 1945, Boeing was ready with the first swept-wing design for the XB-47, which was designated Model 448 by the company. It retained the fuselage of the Model 432 but featured a thin wing swept back at an angle of 35 degrees at quarter chord, and incorporated two more engines added in the extreme tail for a total of six.

The other four engines were still mounted inside the upper fuselage, but were now fed by intakes cut into the extreme nose and exhausted over the top of the wing. The USAAF felt that housing engines inside the fuselage constituted a fire hazard, and preferred designs that incorporated externally mounted engines that would be easier to maintain or replace. In October of 1945, Boeing engineers returned to the drawing board and came up with the Model 450-1-1, which carried six jet engines mounted in pods - 2 pairs in strut-mounted inboard nacelles suspended underneath the inner wing and single units in pods attached to the wingtips. The USAAF liked the change, and approved the Model 450-1-1 in October of 1945.


Bub Steve 12-11-2009 03:32 AM

Oh Ya! bubsteve

Flite-Metal 12-11-2009 03:41 AM

5 Attachment(s)
In order to do that you'll need this, or these... : )

Alpea42 12-11-2009 08:35 AM

Jimmy Stewart in The Strategic Air Command. Great movie of that plane.

Bub Steve 12-11-2009 08:28 PM

Originally Posted by Flite-Metal (Post 670406)
In order to do that you'll need this, or these... : )

looks like they worked real good!! bubsteve

Flite-Metal 12-12-2009 12:39 AM

ATO Parts
3 Attachment(s)

The engines were so low on initial thrust they had to use RATO to get the B-47 off the ground when
carrying the bomb. I'm looking for 1/2 inch diameter slow burn smoke that can be ignited electrically.
There were 33 bottles on the RATO girdle.

Early 47's had internal RATO. After the E they utilized a horse collar harness which released after firing
during takeoff sequence.


Voyager2lcats 12-12-2009 04:24 AM

You certainly wouldn't have had any trouble finding the B-47 immediately after takeoff with those rockets. Good lord that's a lot of smoke!:eek:

Flite-Metal 12-13-2009 07:05 PM

B-47 Thus Far
1 Attachment(s)
Thus far this has been learned:


Flite-Metal 12-13-2009 10:03 PM

We're Not The First...
1 Attachment(s)
Its been a productive afternoon...

As you can see, the rear mains using the Robart 160 tailwheel retract mechanism have no problem providing
proper retraction. Robart 160 up front requires change to air cylinder attachment point and alteration of the
scissors....both are a simple do.

After reviewing the Robart 160 tailwheel assembly with Sam Collins, we determined it need only the addition
of a cross tube between the bent sheet metal and a full width all-thread replacement of the pivot pins to
offset diagonal stress encountered during less than perfect landings.

The B-47 landing was best with both mains touching down at the same time. The Robart 160's have 3/8's
compression. This will be increased by another 1/4". Considering take off and landing are to be virtually
level, this should do the job.

Above...Joe Martin, of Sherline mill and lathe fame, appears on cover of '64 New England Scale Championships
program holding 80" w/s B-47D. The B-47D turboprop had comparable performance to the pure jet B-47s. Its
short coming, aka failing, was reliability.

Above is Joe at the 1965 NAVY NATs declared as a 78" w/s... Back at that time the U.S. NAVY hosted
AMA NATs at naval bases all across the U.S.

Joe, first to fly B-47 in competitive flying scale modeling, proved 36 degree sweep did not poise challenge
at the lower end of the r/c speed envelope...in 1962. Yes, you read it right, 1962. Joe campaigned his B-47D
from 1962 through '65.

The 1:1 Stratojet had yaw issues (Dutch Roll) during the landing approach which required use of a a drag
chute to reduce yaw during final approach. A second chute deployed after touch down slowed the B-47 to
enable the BF Goodrich brakes to stop it.

Calling Joe 47 years after his contest experience, I listened to a technicolor play by play that served to be
rocket fuel to my B-47E-IV aspiration. Joe's only regret...he failed to anticipate the B-47's need for a shallow
approach and landing. Joe's vivid recollection projected a visual as he described the B-47 bucking and bouncing
down the runway after contact.

Frankly, if it were not for my conversation with Joe Martin, I would not be doing this project. Joe Martin is a
true designer, builder, and scale pilot. You need only know the RC systems Joe was forced to use to gain a
HUGE appreciation for his piloting to say nothing for his design and construction skills.

1962 R/C systems left Joe with a having to create a lot of innovative methods to replicate functional control
surface found on the 1:1 B-47.

Thanks, Joe! Passing the torch forward... ;^)


Capt. Midnight 12-16-2009 04:17 AM

Hello Flite Metal!

What sort of model are you planning for your B-47? I recall seeing many B-47s at Boeing Field when I worked for Boeing (1951-1955), just before entering USAF pilot training. I don't recall any RATO-assisted TOs, but I worked 2nd shift, so wouldn't have seen all the flights. One of my pals from USAF pilot training was killed in a B-47 accident after we graduated.

Are you planning a 6-EDF model, and what scale?


Dave Plummer

Flite-Metal 12-27-2009 12:36 AM

B-47 Stratojet @ 1/11.48 aka 1/12

Its a wee over 1/12th at 121"w/s (during this initial stage). Below are the first specs. As for RATO takeoff,
it was only utilized when nuclear weapon was onboard given runway length required it.

That was from the first EvoJet (turbine) work-up. I have moved to the StuMax 110 to reduce AUW. A pair
of StuMax in the inboard nacelles with the opposite engine bay occupied by batteries is where I am today.

This provides as much air flow across the elevator as possible at lower speeds. Landing speed being THE
issue at this point. With the EvoJet the LS would have been around 75 mph... :-(


Flite-Metal 12-29-2009 02:06 AM

I thought it would be no big challenge to find a bottle rocket size smoke bomb to simply ignite using either a
NCad or NMH onboard battery pack but its been a little more than frustrating to find.

Diameter of the RATO bottles is around 1/2 inch at 1/12th and about 1" long. Anyone have an idea what I can
use and where to source them?



Capt. Midnight 12-29-2009 05:53 AM

Smoke 'Canisters' For B-47
Hi Ed!

Wouldn't Shorty's Basement be a good source for your smoke canisters (http://www.shortysbasement.com/index.php)?

My faint recollection is that (especially the early models of) the B-47 only needed the RATO assists for rather high ambient temperatures, when engine thrust was reduced; and I think the final versions of the aircraft (with increased-thrust engines) further reduced the need for the RATO devices. But, clearly, it would be impressive to have some smoke generators for your model, and Shorty's Basement might be a help.


David Plummer

kenchiroalpha 12-29-2009 07:55 AM

Hi Ed
That would be an awesome sight
You could contact RC Smoke They may be able to help
They are local to me here in CT and i have seen and used there products many times
They work great
Take care

Flite-Metal 12-29-2009 02:14 PM

Smok'n :0
Thanks Dave and Hank ! ! This site is so helpful :^) I plan to make resin canisters inserted with the smoke
generators and attached to girdle released after take off.

Well, it appears at first glance and conversation my RATO solution is found... :) Regin S102 with 45 sec burn
time appears to be the way to go compared to all the others I didn't find close to its size 1.25" long x .55" dia.
This is well within the fudge factor size wise. Its 45 sec burn time is longer than I need, yet it was said the ignition
is virtually instant. Here is photo of 10 to the box @ $1.4 ea.

I do not need them to burn the full 45 seconds. I plan to bandsaw these in half if not thirds to accommodate the
number needed and reduce the burn time closer to 15 seconds. They are ignited by nichrome wire across one end
from a battery.

DO NOT use LiPo batteries to ignite them... :(

The overall shape affords easy front end attachment and consealment within the girdle. A simple molded
resin rear nozzle facade works for static resemblence to the 1:1 shape shown above. Ignition via cross
cut of the face then span the cross cut with nichrome is going to be the simplest method...yet to be
tested. I have tons of "fused" 4kmah packs with intelligent fast chargers for onboard ignition from wireless
data terminals I sell. Those should do the trick...safely.

John at Regin took interest in my project and answered questions as best he could. Most RC applications
they sell components for are for sky writing and aerobatic maneuver enhancement. I committed to providing
plenty of witness to their S102 capabilities if it served to satisfy my requirements. Since this is intended as
a Flite-Metal poster child to begin with Regin will definately get their payback for sharing information.

Below is a visual overview that should set the level of expectation for this project.

Thanks guys :^)

Flite-Metal 12-31-2009 01:39 AM

D' Ageless Resource
Our project got a good kick in the rear to shove it forward with introduction of plans from the late 50's.
If you are interested you can acquire the plans from Air Age. We reviewed everything and its going to
contribute a great deal to meaned former shape as we replot the fuselage.

Retract requirement was sealed with the Robart 160 series unit altered to provide greater lateral strength.
Will show the 160's alteration as we move forward. The alteration is something anyone can do to firm up
the lateral strength of the retract frame.


kenchiroalpha 12-31-2009 02:26 AM

Hi Ed
And a very happy and prosperous New Year to you my friend
Im overjoyed that you are making progress with this fantastic model
Heres some thing to inspire you
Take care

Flite-Metal 12-31-2009 03:10 AM

New Resources
1 Attachment(s)

Gotta love it :^)

Yes, its been a rewarding day. I finally have an auditable former set that will permit me to move forward
rapidly. Considering the short turn around on resources I have it will be interesting to see how all the data
flows from the planset we received today. Its the AirAge B-47 planset published in the mid 50's. Definately
answered initial questions which could not be answered from the miltiple view line art.

Its been interesting to note the majority of the line art does not show a datum line view with concentracy...
There is a 5 degree stance plus 2 degrees of wing incidence. For some reason that confuses the artists who
are used to drawing the wing in the head-on view such that only the leading edge is seen. This makes the
fuselage forward of the wing appear to slope down and therefore does not permit the viewer to observe the
concentracy of the fuselage.


Flite-Metal 01-01-2010 10:17 PM

CNC Multi-Axis Hotwire Cutter Needed
I considered using a multiple-axis hotwire cutter for each section of the model. It is important that they are in the hobby to
reduce amount of error due to mis-communication.

There are three fuselage sections...

A). Nose back to last full panel ahead of wing centerline appex within fuselage.
B). Rear section just forward of the vertical fin leading edge intersect with fuselage rearward to rear most point.
C). Center section between above portions.

Within the fuselage I plan for a truss supporting the above three sections of the model.


CHELLIE 01-01-2010 11:26 PM

Originally Posted by Flite-Metal (Post 678015)
I rapidly approach the need to find a multiple-axis hotwire cutter who is in the hobby. It is important that they are in the hobby to reduce amount of communication relative to detail.

There are three fuselage sections...

1). Nose back to last full panel ahead of wing centerline appex within fuselage.
2). Tail forward to where fuselage width and height remain constant.
3). Center section between above portions.

Within the fuselage is a tig welded truss supporting the wing, and the fore & aft main gear.

maybe these people can help you, Hope that helps, Chellie



Flite-Metal 01-02-2010 12:45 AM


Thanks, I spoke to Bob Mellon back some time ago and he was "not into cutting fuselages" from high density
. I was very surprised that he was not eager to do it. He does wings and that appears to be all he
wants to do.

Fuselages require a tremendous amount of double checking over a multi-datum line alignment matrix. Checking
multiple times before cutting is a must or the trash gets full fast.

I failed to find any reference to CNC multi-axis on the second site.


CHELLIE 01-02-2010 06:38 AM

no job to small or big they claim :)


Foam Cutting and Composites Services
We-Cut-Foam specialize in customized foam cutting out of almost every foam available, No project too small or to large, with projects

ranging from a few inches to 20' x 30' full 3D shapes.
Full scale racing car, full scale truck and even airplane fuselage

GGRN 01-02-2010 06:28 PM

2 Attachment(s)
HI guys ! Happy new year to all !
As for me, great interest for the Stratojet ! I've started building one for 6 GWS EDF 50 and feigao 5300Kv... 2, 00 meters long, 2,30 meters WS, retracts. I'm targeting a final weight of 2 kg...
Here are the firsts pics of the build... All the airframe will be out of 3 mm depron, with some plywood reinforcements where needed : Something as simple and light as possible to save some weight. Just have some uncertainity about the CoG location... Where would you locate it ?
Greetings from Paris


Flite-Metal 01-02-2010 07:36 PM

B-47 CG Calculation

Originally Posted by GGRN (Post 678233)
HI guys ! Happy new year to all ! As for me, great interest for the Stratojet ! Just have some uncertainity
about the CoG location... Where would you locate it ? Greetings from Paris Philippe


Here are my two CG calculators from ScaleAero.com:



The CG on the planset I am using as an audit tool is 9" from the wing apex with a sweep of 35+ degrees
on a 57" w/s. This position should be weighed agains the calculators. My 121" w/s is a 2.1228 ratio to the
measurements on the (AT THIS SCALE) 57" 50% w/s. As we progress the w/s of our model will change as
we work through all components.

As for your use of Depron. I do not want to assume anything...it appears you have used XPS to skin built
up wood structure instead of using balsa or obeechi skinned hot wired foam.

The most critical element of the B-47 is the wing root and fixture mechanism to enable a multiple piece wing
to be used. I am creating a fuselage truss from which my wings are suspended. It is designed as an internal
T&C component.

Looking at this from one end looks like a vertical diamond polygon. There are two telescoptic sections to the
truss. Each section is bonded to a hot wired cavity within each fuselage section. Each of the three sections
telescope to permit proper break-down for transport.

As for CG, Boeing provided Dave with this illustration showing 25% of MAC within it.


Flite-Metal 01-03-2010 03:29 PM

PHASE II: Refining Airframe Sectional Shapes
1 Attachment(s)
January 3, 2010 marks phase II for this project. All the raw resources I have collected-to-date are refined,
not unlike oil when it first comes out of the ground.

From this point forward, the process is a series of audits to mean out all but what is deemed "the" proper
shape. Remember we are dealing with art and individual interpretation by each artist as they drew multiple
points of view. It is extremely important you read and understand the next paragraph..... <l:^0

In "every drawing set" I discovered none of the individual perspectives (head-on, side, top-down, bottom-up,
& rear-on) views~drawings were drawn with accuracy of scale...to each other. As you move forward, all
perspectives are being rescaled and meaned to a composite illustration. It is absolutely necessary every view
is sized properly. Otherwise guys, they are useless... Go check your favorite three view and see what I mean.

If all I wanted was a simple three or more view of the B-47.....I've found there are several out there.

These become the tools with which to work-up and derive a meaned set of refined tools to build a B-47E-IV
model. This is not to say this is "the" way or how it should be done. I'm saying this is the only way I know of
achieving this without a laser scanner.

At the beginning of this thread this was my infant work-up. Today, I work with everything gathered to create
"the project image master" and a measurement index.


Sam Collins is my partner in crime. http://www.wattflyer.com/forums/atta...1&d=1350565524 Sam shared my interest in the B-47 and wanted to
build one the same size with edf for power instead of BB's quest to build it with six turbines. After I worked up
a B-47 powered with a pair of EvoJet turbines the AUW brought me back to edf.

After our last skull session, Sam was left working mechanics of the flaps. Later today I'll send wing bottom-up,
rear, and head-on view at scale for Sam to work with. Our last conversation had us headed down a path to a
pair of carbon fiber tube-in-tube for alignment and a tilt-mechanism with a laser cut and channel lined cam
path either side of each flap section. I more or less stole this from a friend's Tu-95. George Maiorana's Tu-95
is shown on my YouTube flap focus.

I'll be back and share as this moves forward... :^ )


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