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Author Topic: New Project-Big is beautiful B-29 Superfortress  (Read 6854 times)
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RRCA
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« Reply #25 on: November 16, 2013, 11:02:25 PM »

The plans are now at the printers and I am due to collect them on Monday Smiley
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« Reply #26 on: November 17, 2013, 08:40:32 AM »

looking forward to this one.

you not started yet.  Grin
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« Reply #27 on: November 17, 2013, 12:36:41 PM »

Wel, I'll go to the foot of our stairs!!  Yes - that is a really big fellow.  And it is nice to see that you intend adding a bit of detail. I am always curious when I have viewed the large scale models - last was a half scale Tiger Moth - to see that detail is minimal. When you  look at some of the plastic models people make - say 1/48 or 1/32 and 1/24th scale  where the wingspan might be a foot or so the detail there is incredible.  So I have always wondered why? The Scale Glider chaps do go into quite a bit of detail - including often emulating the construction.

Glad you got the pictures - a bit concerned because sometimes things can go astray.  I did not send details of the U/C legs etc. as I assume you will be a bit curtailed by the requirements of the retract system?  (See below however).

As a matter of interest can you say where the test flight will be - might organise a coach party! Roll Eyes Smiley 

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« Reply #28 on: November 17, 2013, 03:28:32 PM »

looking forward to this one.

you not started yet.  Grin

Not yet. It will more than likely be next weekend I start as I'm in work all week

Wel, I'll go to the foot of our stairs!!  Yes - that is a really big fellow.  And it is nice to see that you intend adding a bit of detail. I am always curious when I have viewed the large scale models - last was a half scale Tiger Moth - to see that detail is minimal. When you  look at some of the plastic models people make - say 1/48 or 1/32 and 1/24th scale  where the wingspan might be a foot or so the detail there is incredible.  So I have always wondered why? The Scale Glider chaps do go into quite a bit of detail - including often emulating the construction.

Glad you got the pictures - a bit concerned because sometimes things can go astray.  I did not send details of the U/C legs etc. as I assume you will be a bit curtailed by the requirements of the retract system?  (See below however).

As a matter of interest can you say where the test flight will be - might organise a coach party! Roll Eyes Smiley 



The detail will be in areas most visible, like the cockpit area and although the undercarriage will be a basic tricycle retract system i will be making scale oleo struts to go over the heavy gauge rods and keeping to the twin wheel format as on the real aircraft.

As for the test flight, I'm unsure to the location of this as of yet. I will be hopefully joined a local flying field by the time its built so the test flight will more than likely be there, however I do tend to find a quiet field where I am on my own and undisturbed for test flights of big models. Its bad enough test flying let alone having an audience cheer you on adding pressure to you to make sure it doesn't pile in first flight haha Smiley
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« Reply #29 on: November 17, 2013, 04:13:30 PM »

I've been thinking of another B-29 that I might model mine on. Anyone remember 'Kee Bird'?................ Smiley

For those that don't, 'Kee Bird' made a forced landing in a cold remote Artic range off Greenland and although the crew were picked up some three days after, the B-29 was left there in the same spot it came to rest for 50 years until a chap called Daryl Grenemier had a dream of recovering the bomber. The US goernment gave up possession of the Kee Bird to anyone willing to recover the B-29, and Daryl spent three years organising its recovery. Despite the conditions the Kee Bird remained almost preserved intact with very minimal work required to get it back into the air. After some months work and the loss of one of his closest friends, Daryl finally reached his goal and dream of flying the B-29 out of the Artic. Because it was just after the winter period at this time, snow was dominating the area around the B-29 but it was a rush to take the bomber off from the frozen lake before the ice became to thin to do so. While taxiing the Kee Bird across the bumpy terrian to the runway, the APU that was running at the back of the bomber broke away from its mounting. Fuel spilled onto the hot APU and it caught fire. By the time the bomber had been stopped, fire had already swept through the fuselage. Daryl and his crew all escaped without injury and could do nothing but sit and watch this priceless bomber burn. All the remains of the aircraft including the new engines and propellors would come to rest at the bottom of the frozen lake when it thawed, where it remains still to this day.

I thought that if I build the Kee Bird at least it will still be flying in some form Smiley
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« Reply #30 on: November 19, 2013, 05:56:47 AM »

Well the printers totally got the plans wrong. They took it up on themselves to decide I must of got the measurements wrong with my plan and it was cm not inches it was meant to be because such a size model plane must of been wrong! Was not impressed one bit! So they are now reprinting to the correct size but due to work means I cannot get them until Friday.

On another good note, my vacuum former unit will be finished this weekend ready to form the cowls and dummy radial engines, gun turrets, clear fuselage blisters and the main nose/canopy. I will also be using this method to form the undercarrige doors and bomb bay doors
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« Reply #31 on: November 20, 2013, 08:12:56 AM »

I'm scratching my head over something and this is aimed at anyone that has built an electric multi. I'm planning to have the motors rotating clockwise on the starboard wing and counter clockwise on the port. I'm using FMS's excellent scale 14" dia four bladed props but then realised I don't think they do counter rotating four bladers only three bladers for the 80" Mitchell B-25 or the P-38 Lightning. The P-38s 3 blades will be too small. The Mitchell's will be big enough bit not scale as the 29 swung 4 bladers.

So what do I do? Do I go for the larger 3 blades or do I stick to the 14" for blades and run all four outrunners the same direction? If I do, what are the chances the bomber rolling over or should it be fine with this set up?
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« Reply #32 on: November 20, 2013, 08:38:01 AM »

i would go for the three blades for flight and the 4 blades for display.
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« Reply #33 on: November 20, 2013, 10:54:35 AM »


Haha  Cheesy At least I know where to go if I want a to scale escort fighter lol

Gaa... Now you've got me thinking about a P-47N, and my brain hurts! Cheesy
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« Reply #34 on: November 20, 2013, 02:32:03 PM »

My FMS P-47 has a 4 blader and it sounds awesome. I've been informed by a modeller with lots of experience that having all four motors rotating in the same direction will not effect the flight performance so I'm still king with the 4 bladed scale P-47 props. They look good and sound awesome.
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« Reply #35 on: November 22, 2013, 09:47:01 AM »

Happy bunny. Plans have now finally arrived and can now get on with the task of drawing on the extra mods for the R/C conversion Smiley
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« Reply #36 on: November 23, 2013, 03:30:22 PM »

Not happy with conventional methods, I am currently designing a Fowler flap system for the B-29
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« Reply #37 on: November 25, 2013, 02:44:00 AM »

I'm still in two minds about the powerplants for the 29? I was planning on four 500kV outrunners turning 14" 4 bladed props bit am now thinking it might be overpowered? I'm trying to design and construct it to keep the weight down to 10lbs or less. I want it to fly as scale like as possible and pretty slow not like a fighter place so am now thinking four 850kV outrunners swinging 14" 4 bladers could be enough. Any thoughts?
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« Reply #38 on: November 25, 2013, 04:29:09 AM »

I am a complete amateur when it comes to electric motors and there are some useful works on the internet; but it seems to boil down to weight primarily and then the kind of performance required. I assume you will go for the slower revving motor as you will want a steady pull.

I have built a couple of "sport" vintage models and they are overpowered, certainly. But it seems to do no harm. One will fly quite happily on quarter throttle. Excess power is better than "marginal".

Years ago a chum of mine was a multi fan and as "glows" were the only option did not have the opportunity of contra - rotating engines. He never had any problems as I recall.

 
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« Reply #39 on: November 25, 2013, 07:19:09 AM »

I'm no "eggsburt" either, but flying electric primarily at "quarter throttle" is a good way to fry the bits.  You'll want to set up the system to where it operates in its efficiency rating (where you'll "cruise" at >65% throttle).  The motors usually have a published "efficiency" at a certain Amp draw with a certain Voltage.

All motors with individual ESC's and battery packs is the common way to set multis up and you'll probably need at least 38-40mm class motors on 5S to swing 14" x 4 blade props.  Your initial choice of 500kV motors with the 5S packs is a better choice than the 850.  Your 10# target weight sounds a bit low.  You're carrying 2# of batteries alone, plus 4 x ~200 grams of motor (another 2#).  That weight added to full-house control and electric retracts...good luck.  I don't think too many of the users of this Forum can offer adequate help.

BUT...

Good bets would be on WattFlyer and The E-Zone.  In any case, a prime piece of equipment would be a Watt-meter.  MotoCalc is also a good tool if it is a current version.
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« Reply #40 on: November 25, 2013, 09:21:59 AM »

That's twice now I have had the original option of 500kV said to be the best because of swinging the 14" 4 bladers so I think that will be the way to go although saying that I forgot about motocalc so will look at that as well. The weight is deffo a key factor it seems and until I get all the equipment needed to fit into the model weighed up only then will I roughly know what the weight target is going to be close too.

My 55" span P-47 weighs in at 4lb and is powered by a 500kV motor swinging a 4 blader so in theory 4 500kV motors should pull a model weighing in at 16lb around the sky easily so if I keep it below 16lb I should ve all good.
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« Reply #41 on: November 25, 2013, 09:41:01 AM »

Thank you Pit - something else I have learnt! I presume you mean burn it out by the way. I thought I was being clever and getting the max out to the battery!  Yes at  quarter throttle it was very slow and it was just an attempt to see how slowly it would fly. I would guess that normally it runs at 1/3rd to 1/2 throttle -but not "fast" enough even then! However being a vintage style model I do cut the motor after a minute or so and let it glide and then open up again if I want to gain more height, then repeat the process.

Must say these electric motors are quit complex and very fussy. With diesels and glows it was very much by "ear" - make sure it is not running too lean or over compressed and that was about it!  Hmmmm.... glad I have still got my diesels.........

But thank you again - I do not recall seeing anything in what I have read about using electric motors - mostly it centres on not abusing the lipos.

Sorry for digressing on your topic, Rob, but had to thank Pit.
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« Reply #42 on: November 25, 2013, 09:51:06 AM »

No that's fine mate its what we are all here for end of the day Smiley Electric motors aren't complex David just a bit of a scratcher trying to figure out the balance of weight and power. Lipo batteries are excellent provided they are balance charged properly and with brushless outrunners you stand a hell of a lot less a chance of burning out a motor than you do a brushed one. ESC's however can burn easy if not matched well. A low amp ESC coupled with a big powerful motor is a recipe for disaster.

On a diff note Dave, I don't suppose you have any good ebooks in pdf on the B-29 do you? Smiley
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« Reply #43 on: November 25, 2013, 03:10:41 PM »

Thank you Rob - and no - at least I don't think so - not sure what an ebook is but do know a pdf.

I suppose having had years of experience with diesels and i/c engines I am more familiar and thus confident. Yes I have appreciated that the ESC and Motor need to be "matched" and so far have been a bit meticulous in this respect. I think too it is a generation thing but I don't like using anything to it's full potential so thought that running the motor below it's maximum capability was good! But one lives and learns.

I suppose it is a bit mean to taunt you but I do have the "Boeing B29 Superfortress - the Ultimate Look: from Drawing Board to VJ Day" by William Wolf.  It is possibly one of the most detailed books on any aeroplane that has been published.

Is there anything in particular that you are wanting in case I can copy it for you.

I fly sometimes at Sculthorpe which is just up the road (still MoD).  Washingtons were based there and I have to admit that when I am driving along the runway or peri. track I do have the odd fantasy!  
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« Reply #44 on: November 26, 2013, 12:07:42 AM »

Thank you Rob - and no - at least I don't think so - not sure what an ebook is but do know a pdf.


An ebook is basically a downloadable book you can read on your pc or lappy or suppose I better mention it....Ipad/Tablet - but 9 times out of 10 they are in pdf format so chances are you may have one now Smiley

The bloody position of the front landing gear retract is doing my head in!!  Angry

I'm trying to keep the scale appearance as best as I can but because the nose wheel sits forward at an angle it means when the wheels go up they stop short of the UC doors so it means they wont shut. I need a retract unit that passes 90 degrees which I dont think exsist or I have to put the unit further up into the fuselage but that then means the front wheel wont be sat right then and it will be too close to the body of the bomber.

I could bend the strut forward but that then brings me back to the doors not being able to shut again. The only other option is to loose the scale look slightly at the front and have the retract unit 90 degrees to the front bulkhead and up 1/2 inch higher than I originally wanted, that then gives me an extra 1/2 inch clearance allowing the doors to shut but on the ground it will be 1/2 an inch lower than it should be. The tips of the 14" diameter props are gonna be close to lawn cutting as it is.

Oh the joys of building models eh?  Roll Eyes
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« Reply #45 on: November 26, 2013, 04:12:01 AM »

mount the retract on a moveable base, then you could retract the leg as far as it goes, then tilt the base to finish the movement.

just a thought, probably a crap one though.  Roll Eyes
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« Reply #46 on: November 26, 2013, 10:29:07 AM »

The principle is there and in theory could work if I hinged the mount and then used a servo connected to the sequencer that operates the uc doors. It would have to be a metal geared servo though and a good one cause is going to take a lot of strain with impacts and bumps
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« Reply #47 on: November 27, 2013, 04:48:14 AM »

I have finally got the powerplant sorted for the B-29 Smiley

850kV brushless ourrunners x 4
40Amp ESC x 4 turning 11x5 four blade props on a separate bec
14.8V 3300mAh Lipo batteries x 2

These calculations are for two motors with one ESC each from one of the Lipos.

Batt Amps 66.0 Motor Amps 66.0 Motor Volts 12.6 Input (w) 832 Prop rpm 9848 Thrust (oz) 124.4 PSpd (mph) 46.6 Flight time (full throt ) 4.00 mins.

Those calculations have been done with direct drive props via MotoCalc with the airframe weight estimated at 6.5lbs empty ie no motors ESC or batteries fitted. The combination was tested by the program and it worked. The only final analysis issue being the batteries could run hot. Its answer for reducing heat was to reduce the diameter of the props or they're pitch or increasing the power output of the batteries. Calculated using 6 cells at 4000mAh hardly changed the input but increased the flight time but 2 minutes. No issues resulted and the heating.g up issue with the battries went.

I think I have my powerplant finally Smiley
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« Reply #48 on: November 27, 2013, 08:02:32 AM »

Thank you Rob - and no - at least I don't think so - not sure what an ebook is but do know a pdf.


An ebook is basically a downloadable book you can read on your pc or lappy or suppose I better mention it....Ipad/Tablet - but 9 times out of 10 they are in pdf format so chances are you may have one now Smiley



No don't have any of those - it is a generation thing - I am a "bookie" (I think I must have a few hundred) and I just cannot read things of any length from the computer screen, ipad or a Kindle (although I can see the advantages). I do know what an ipad is (refined version of a tablet Wink) and I also have an ipod but like the TV/CDplayer/apple TV device and humax hardly ever use them!
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« Reply #49 on: November 29, 2013, 10:49:43 PM »

And so the building begins  Grin

Stage 1 Fin and Rudder

The images speak for themselves really but cut the parts out and they all went together nicely. The leading edge I made from 1/4 soft sheet laminated between 3/32 hard giving it a plywood effect. It's well strong.

Slotting the ribs together gave a ridged strong join and the whole assembly is tough but still light. R20 rib was not glued in place like the rest though as this is the rib I'm using for the Rudder servo as you can see in the image. The servo is a 9gm Nano and the cylinder links are a snug fit held in place by two nuts locking them down. I also dropped a spot of CA on the threads to make sure. This link or servo will never leave the tail so extra effort has been made to ensure it does not fail although the rudder isn't really critical in flight even if it does.
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