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Author Topic: B-36  (Read 319 times)

Offline Trostle

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B-36
« on: March 21, 2020, 12:21:43 PM »

Offline Jim Carter

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Re: B-36
« Reply #1 on: March 21, 2020, 02:57:55 PM »
I like it.  Make you an offer … you buy it … I'll build it … you own it, store it, transport it and pilot it … I'll be the pit man/mechanic and together we'll enter in it NATS and NASA Team Scale Events??   ;) :)


Offline Trostle

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Re: B-36
« Reply #2 on: March 21, 2020, 05:20:09 PM »
From Magnesium Overcast to Balsa Overcast.  Two men on the handle???  The airfoil looks like a stunt wing foil.   y1

If you can find a good set of 3-views of the B-36 or have the Monogram 1/72 plastic kit, you will see the airfoil is really thick and almost symmetrical.

Keith

Offline Trostle

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Re: B-36
« Reply #3 on: March 21, 2020, 05:21:53 PM »
Jim,

Are you even a little bit serious?  I think we could get the thing to fly with 6 OS .15's, definitely 6 OS .25's.  The short kit shown shows that whoever builds the thing needs to provide the wood for wing sheeting and fuselage planking.  That would put a serious dent on my balsa supply.  We would need flaps and retracts.

Do you have a pick up truck or a long trailer?

Keith


I like it.  Make you an offer … you buy it … I'll build it … you own it, store it, transport it and pilot it … I'll be the pit man/mechanic and together we'll enter in it NATS and NASA Team Scale Events??   ;) :)

Offline John Given

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Re: B-36
« Reply #4 on: March 22, 2020, 03:25:40 AM »
If you can find a good set of 3-views of the B-36 or have the Monogram 1/72 plastic kit, you will see the airfoil is really thick and almost symmetrical.

Keith

The B-36 had a tunnel in each wing that allowed access to the area in front of each of the R-4360s.

Online Dan McEntee

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Re: B-36
« Reply #5 on: March 22, 2020, 08:28:26 AM »
Didn't the B24 have a similar airfoil? D>K

    I don't think so. The B-24 and the PBY had the same air foil, and flat bottomed, high aspect ratio, high lift airfoil that was a departure from the norm at that time. That was how both airplane were able to attain the higher speeds and longer ranges they had than other bombers. The B-24 could carry the same bomb load as the B-17 but do it 100 MPH faster a hundreds of miles farther. Same for the PBY for it's long observation and search patrols. I think the PBY was the first to have some sort of rest room because of it's long duration abilities. When I see the B-36 I always think of the one that was in the old mags built by an Air Force sergeant, a Sgt Ford I believe, and showed him building a shipping crate for it to get ready for his next move. Neat project, just more than what I would want to tackle.
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Offline Trostle

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Re: B-36
« Reply #6 on: March 22, 2020, 12:58:24 PM »
The B-36 had a tunnel in each wing that allowed access to the area in front of each of the R-4360s.

The spark plugs on those P&W 4360's could be changed in flight.

Keith

Offline Jim Carter

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Re: B-36
« Reply #7 on: March 22, 2020, 03:54:26 PM »
Jim,

Are you even a little bit serious?  I think we could get the thing to fly with 6 OS .15's, definitely 6 OS .25's.  The short kit shown shows that whoever builds the thing needs to provide the wood for wing sheeting and fuselage planking.  That would put a serious dent on my balsa supply.  We would need flaps and retracts.

Do you have a pick up truck or a long trailer?

Keith
Sure am!  ;D  I love challenges especially if and when I can find someone who isn't afraid to greet the world with open arms and embrace every moment and opportunity with every breath the Lord give us  ;D! Yes, it would be a challenge, yes, it would dent both yours and my balsa supplies and probably cause my wife to smack me upside the head  :o like in the old cartoon "Maggie and Jiggs" when I start sneaking money from the bank account.  But what the heck ... when it's all said and done and we're standing besides that "Big Beautiful Creation" ... me cranking and tuning the engines, you grabbing and holding the handle ... two more guys grabbing and holding on to you  LL~ LL~ as I release the plane ....!!  Then you nail the flight with a sterling 3 point landing ... man-o-man ... heck yeah, I'm serious   :) :).  It's a visual, I can imagine, embrace and look forward to and I hope you can also!!  ;D ;D ;D

Jim

Offline Jim Carter

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Re: B-36
« Reply #8 on: March 22, 2020, 04:16:18 PM »
Jim,

Are you even a little bit serious?  I think we could get the thing to fly with 6 OS .15's, definitely 6 OS .25's.  The short kit shown shows that whoever builds the thing needs to provide the wood for wing sheeting and fuselage planking.  That would put a serious dent on my balsa supply.  We would need flaps and retracts.

Do you have a pick up truck or a long trailer?

Keith
I'll share this with you so and everybody so you would have an idea as to what you would be getting into based upon my KYO B-29 Stratofortress that I replicated and built.

   “DOC” Spec Sheet
Planked fuselage diameter @ cockpit windows = 5.125
Planked fuselage @ horizontal stab l.e. = 3.187
Planked fuse @ tail frame = 2.125
Wing span fuselage to outer panel joint = 20.625
Sheeted wing root @fuselage = 1.687
Sheeted wing root @ outboard rib (w/o tip) = .812
Sheeted wing root @ joiner =1.187
Span of outer panel (w/o tip) = 17.812
Wing cord @ root = 10.125
Wing cord @ tip = 4.5
Horizontal stab span = 29
Horizontal stab cord @ fuse =3.75
Horizontal stab @ outer rib = 1.75
Vertical stab height off fuselage @ rudder l.e. = 10.125
Power = 4 ea. OS Max 25 R/C w/mufflers
Spectrum receiver, 4 ea. servos, 6v ni-mh battery and switch
Weight (dry) = 9 pounds 4.8 ounces

I have a full photo documentation of the project and would do the same with this project if anybody is willing to "jump in the alligator pond with me … without complaining!!   ??? :-\ LL~ LL~

Offline Trostle

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Re: B-36
« Reply #9 on: March 22, 2020, 05:42:39 PM »
Jim,

So, your B-29 weighed less than 10 pounds.  If your KYO version is the same 1/2" = 1' scale (or 1/24 full size) as this B-36, then based on information I have on the B-29 which had 1,736 sq ft of wing area, your model had 434 sq in of area and you flew it with 4 OS .25's. and it weighs almost 10 pounds.

According to my reference, the wing area of the B-36 is 4,772 sq ft.  At 1/2" = 1' scale (1/24 full size), the area of the model would be 1,193 sq in almost triple the area of your B-29.  Could this B-36 be built at 20 pounds or less (without fuel) which is the limit for AMA CL Scale?  Six OS 25's would be easily enough power.  Six OS 15's might do it.  I have the engines, FP's  and RC and all new.  You might be talking ourselves into something.

This B-36 would be nearly three times the area as your B-29 and could not be more than twice the weight.  That 20 pound max weight might be a deal breaker, but unless we can do retracts and flaps, it would not be competitive with the AMA rules.  Also, if this is done right, I think the engines need to be buried in the wing so there are no protruding heads which probably means shaft extensions and provisions for good cooling.  I think there is a way to take care of the extension shafts but there is added weight.  Cooling will still be a problem.

I can remember seeing a Lockheed Electra with four ST .29s built and flown by Earl Carpenter in Southern California.  He had a harness around his upper torso with straps on the back so that he could be restrained by a helper in the center of the circle without being dragged around.  I do not know how much it weighed, but it was a handful with the handle strapped to his wrist.  The model hung in the T&A Hobby Shop in Burbank for years and was on the cover of a Flying Models magazine.

I flew my Martin Baker at almost 5 pounds on 400 sq in had an OS 60H rear drum engine.   (It is in the AMA museum.)  It was challenged in the wind but could get 45o sustained high flight with no wind.

I could get semi-serious about this, but see some challenges.  First the weight.  Then the cooling problem unless we go ahead and expose the engines.  To be competitive in team scale, even though there might not be many competitors at the Nats, there will be some scale detail needed for the cockpit area which is under a glass house for all to see and at least some rudimentary detail will be needed there which becomes a challenge by itself.  And the blisters might need some detail.  The retracts and flaps should be doable but takes time and a lot of attention to detail.

One thing that would help is the use of a material called Flite Skins.  This is a form of fiber glass sheets, really smooth,  that is available in fairly large sheets.  It is used on some large RC scale birds and is ready for final paint, though leading and trailing edges still have to be worked.  I think it could be used to wrap the circular fuselage of the B-36.  It would save some weight and make the finishing process a bit easier.

For transportability, I think the wings need to be addressed in some fashion.  Removable in two halves.  To have just some portion of the outer panels removable would result in a core part of the airplane that becomes impractical to transport.

So, is less than 20 pounds doable on a span of almost 11 feet?

Keith

Offline Fred Cronenwett

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Re: B-36
« Reply #10 on: March 22, 2020, 06:24:10 PM »
I have a complete walk around set of pictures from the B-36 at Air Force museum. I have the 115" span plans for this model, when did the numbers if I used electric it would have 6 E-flite 10's on board with 3S batteries. Put 9" three blade props on you have more than enough power

Just so everyone knows the main gear retracts are very complex. When we look at the real aircraft there are no less than 6 doors on these units can you find them all...? it's kinda like finding waldo. Here is a hint there are two doors that you can't even see that are internal to the aircraft structure.

If anyone is anyone is interested in a set of the pictures let me know and I can make them available.

I figured if I built one of these it would have the following
1) simplified main landing gear
2) flaps
3) 6 electric motors with the 3S batteries in the nacelles
4) retracts

Bomb day doors are possible but also another engineering science project once you see how the doors are hinge and open
You will also need a gear door sequencer for the nose gear and main gear doors, I think they behave like the gear doors on a P-51 Mustang
It would pull like a tank, just like my B-29 does 30+ lbs, remember the line tension is controlled by the line guide location, even if the model is heavy you can trim these guys to pull enough to fly but not so much they pull you over. This model would require an adjustable line guide.
With 10 wheels, 6 spinners, 6 props, it would be a beast, and make my B-29 look small.
Using 2.4 Ghz here is the parts required

6 ESC's
6 motors
12 batteries (you want spares and enough to fly twice in one day)
10 wheels
6 spinners
6 props
gear door sequecer (1 or 2 could work, better if separate)
6 flaps - 6 servos
nose gear - retract unit with 2 servos for the doors
main gear - 2 HD retracts with 2 std servos for the main door
adjustable line guide

Fred
Fred Cronenwett
AMA 3879 - CL Scale
Model Aviation CL Scale columnist

Online Steve Berry

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Re: B-36
« Reply #11 on: March 22, 2020, 06:32:17 PM »
Scale really isn't my thing, but could you go electric with this? That would solve the exposed engine head aspect, and batteries could be moved around as needed for balance. Also the structure could be made lighter since there would be very little, if any, engine vibration, and that means a lighter overall model. Bob Hunt has loads of experience with multi-motor electrics, so I would recommend contacting him on Moto setup.

Either way, I would love to see this project come together.

Offline Fred Cronenwett

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Re: B-36
« Reply #12 on: March 22, 2020, 06:41:30 PM »
Kieth,

I notice a lot of builders tend to make the models too strong, they need to be light but strong enough not to break during flight. I figured if I built one of these it would come in around 16 lbs but it would be on a diet. 1/32 balsa skins over a foam cores with fiberglass.

The inboard engines and wing section would be built into the model as one piece and then the outer wing sections would plug in (they would have each have two motors). Then have a wing tube that joins the outer wing to the inner wing section.

It would take a trailer to haul this model, keep in mind that the vertical fin is quite tall, the top of the fin is 22" from the floor. 8' long with a 7" dia fuselage.

I wouldn't even consider a glow powered version of this, I was going to put the ESC and the battery in the front of the nacelle where there is an scale air intake. Electric scares people off but you can hide electric motors in all sorts of cowls with no bumps or holes.

Wow...
Fred
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AMA 3879 - CL Scale
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Offline Fred Cronenwett

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Re: B-36
« Reply #13 on: March 22, 2020, 06:51:09 PM »
with electric the motors have two numbers Kv and watts. I tend to ignore the Kv number (see my Feb 20 CL scale column) and look at the watts. There are electric motors that can power this without any problems, because there are 6 of them this is how to figure out the power required

Total weight of the model  = 15 lbs
15 / 6 = 2.5 lbs of model per motor

use 140 watts per lb of model to determine the total power you need

15 * 140 = 2,100 watts

There are electric motors that provide that much power but it is done by all 6 so...

2100 / 6 = 350 watts of power per motor

All you need is 6 electric motors that have at least 350 watts of power per motor with the prop size that fits the model

Bottom line there are electric motors that can power this model

And you move the batteries around to move the CG the motors would be at the trailing edge of the wing and typically they are lighter than the batteries

Fred
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AMA 3879 - CL Scale
Model Aviation CL Scale columnist

Offline Fred Cronenwett

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Re: B-36
« Reply #14 on: March 22, 2020, 07:16:18 PM »
There would have been a team of multiple engineers designing those landing gear doors back when this aircraft was built doing nothing the doors and the mechanisms to open and close them.
Fred Cronenwett
AMA 3879 - CL Scale
Model Aviation CL Scale columnist

Offline wwwarbird

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Re: B-36
« Reply #15 on: March 22, 2020, 09:18:11 PM »
The spark plugs on those P&W 4360's could be changed in flight.

Keith

 All 224 of them.  ;D
Narrowly averting disaster since 1964! 

Wayne Willey
Albert Lea, MN U.S.A. IC C/L Aircraft Modeler, Ex AMA member

Offline Howard Rush

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Re: B-36
« Reply #16 on: March 22, 2020, 10:03:14 PM »
    I don't think so. The B-24 and the PBY had the same air foil, and flat bottomed, high aspect ratio, high lift airfoil that was a departure from the norm at that time. That was how both airplane were able to attain the higher speeds and longer ranges they had than other bombers. The B-24 could carry the same bomb load as the B-17 but do it 100 MPH faster a hundreds of miles farther. Same for the PBY for it's long observation and search patrols. I think the PBY was the first to have some sort of rest room because of it's long duration abilities.

PBY airfoil, according to David Lednicer’s site, was an NACA 21.  B-24 is was a 22% Davis airfoil at the root, 9.3% at the tip.  B-36 had NACA 63-series airfoils.  The B-17 had symmetrical airfoils, so it might have made a good stunt plane.  Come to think of it, it did make a good stunt plane.
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Online Dan McEntee

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Re: B-36
« Reply #17 on: March 23, 2020, 08:37:35 AM »
PBY airfoil, according to David Lednicer’s site, was an NACA 21.  B-24 is was a 22% Davis airfoil at the root, 9.3% at the tip.  B-36 had NACA 63-series airfoils.  The B-17 had symmetrical airfoils, so it might have made a good stunt plane.  Come to think of it, it did make a good stunt plane.

    Well, I stand corrected. I was going on an old memory of one of the TV shows from the early days of cable TV such as Great Planes, First Flights, or WINGS which described them as such. Both originally built by Consolidated, I think the PBY came first and B-24 followed. I'll have to look up the three views or reference the site you mentionedand check them out.

    I was fortunate enough to see the B-17 put through some patterns at a NATS years ago when Sean was entered in Junior or Senior. It was definitely and impressive sight to see.
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Offline Jim Carter

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Re: B-36
« Reply #18 on: March 23, 2020, 05:01:16 PM »
Jim,
So, is less than 20 pounds doable on a span of almost 11 feet?

Keith
Howdy again!  Well, I've read your post and the thoughts of Fred and the other guys and still, in all honesty, I believe it could be done and still be "grams" under the 20# rule  ;).  At the same time, I love the idea of the hidden engine heads but I wouldn't want to tackle that level of complexity … not that it couldn't be done but in the words of Dirty Harry: "... a man has got to know his limitations" ;)!!  I recognize mine, 'fer shur' ;D!! Yet, for the scale judging, I understand the nacelles could be in a configuration that would allow the engines to be hidden and then reconfigured for flight.  So that's a possibility for nitro engines.  As for the concept of electric power … I like it, I really like it BUT like Fred points out it would be a matter of selecting the right combinations so on the one hand … we may have "inherited" another team member, of sorts ;D LL~!  Removable wings would certainly need to be incorporated into the build.  There's a number of approaches, sliding aluminum rods, dowels and even the tongue method that was used for the B-29, so I don't see that as a problem other than deciding for personal preferences.  However, ONLY if you want to spend some serious money to have some "scale" gear designed by Robart or Century Jet, I'd say let's give up a few points and smile using some E-Flite 60 retracts  :-[!   Okay, as to fuselage and wing skinning methodologies, I'm sure you know there are quite a few.  I planked my B-29 with all 3/32" square balsa, plank by plank.  This project could also be planked or sheeted with 1/16" balsa, or even sheeted with 1/64" ply.  Then topped with a layer of silkspan, I suppose, if it is to be doped or just coated with some Sig Stix-It and monokoted as I did with the B-29.  Just so you know, I have no experience with Flite Skins and minimal experience with fiberglassing.  However, I suppose if you wanted to go that route, one of the guys on this site could recommend another "team member to-be" who could take over the project and give it an immaculate world class FAI scale finish (I never pursued that skill level, sorry)  :-[  Well, I guess that about covers my thoughts for the moment.  Let's see where this goes and what other thoughts come in, shall we!!  ;D ;) ;)

Offline wwwarbird

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Re: B-36
« Reply #19 on: March 23, 2020, 08:38:46 PM »
The B-17 had symmetrical airfoils,

 Furreal? Recalling building my old Monogram 1/48th B-17 years ago I knew it was close but...
Narrowly averting disaster since 1964! 

Wayne Willey
Albert Lea, MN U.S.A. IC C/L Aircraft Modeler, Ex AMA member

Offline Jim Carter

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Re: B-36
« Reply #20 on: March 24, 2020, 12:11:11 PM »
Furreal? Recalling building my old Monogram 1/48th B-17 years ago I knew it was close but...
Greetings!  I ain't all 'dat smart but here's what I found!  The B-17 used a NACA0018 aerofoil, a fully symmetrical section which gives a consistent performance over a wide speed range with lowish drag co-efficient: https://www.quora.com/Why-was-the-B-17-designed-with-a-symmetrical-airfoil-of-the-wing  Hope this helps!  H^^

Offline Trostle

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Re: B-36
« Reply #21 on: March 24, 2020, 05:09:58 PM »
Jim,

Are you even a little bit serious? 

Keith

Well, after not so much thought --  I have a bucket list of models that I need to build.  A project like this would be about #72 on that list, even for somebody else to build it.  Even with the extra engines, it would not be any more competitive in competition than say a B-26 (another contender on my bucket list) built to the same standard.  In fact, that size with the 11 foot wing span, it would not score as well for realism of flight than a smaller ship because it is just too big to fit comfortably and look "realistic" on a circle limited to a 70 foot radius.   Something that big is really impractical for CL, even as a novelty.

I already have another B-36, much smaller like with 6 TD .010's, much higher on my bucket list.

BTW, I have successfully flown and competed a Republic XF-12 at the Tucson 1/2A multi-engine profile scale contest with 4 TD .010 engines.  38 1/2" span.  That was enjoyable.  An 11 foot beast would not be so.

Keith

Offline Fred Cronenwett

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Re: B-36
« Reply #22 on: March 24, 2020, 08:10:47 PM »
six main gear doors, two large ones, one folded up against the bottom of the wing aft of the strut and three small ones that allow strut to retract and then cover the gap.
Fred Cronenwett
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Offline wwwarbird

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Re: B-36
« Reply #23 on: March 24, 2020, 09:18:30 PM »

 --  I have a bucket list of models that I need to build.  A project like this would be about #72 on that list,

Keith

 Exactly why I sold the kit I had.
Narrowly averting disaster since 1964! 

Wayne Willey
Albert Lea, MN U.S.A. IC C/L Aircraft Modeler, Ex AMA member

Offline Jim Carter

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Re: B-36
« Reply #24 on: March 25, 2020, 08:49:47 AM »
 :-\  Oh well, I acknowledge and understand!  Can't say I didn't offer though!! :)  Guess I'll put my superglue back in the freezer  LL~ LL~!

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