rwolfe9

Does anyone have any ideas on some flaps? My son and I are scratch-building a B-52. We are planning on 8-70MM ducted fan units to power it. What I need suggestions on is how to construct some flaps for this(or if I even need them). While surfing the web I saw pictures of a real B-52 with the flaps down, they are huge! I also found a video of a model over in the UK that had 8 jet engines on it. That must have cost a mint. I did not notice any flaps on it, but I did see air brakes. The plans I made I sized to make the 70mm fan units sized correctly, therefore it will be about 11'6" to 12' wingspan.

TFF

If you do one of the NASA B52s; they had the flaps bolted up because they had to saw a chunk out of one of the flaps for the tail of the X-15 to fit and flew them that way for the next 40 years until they got a "new" one a couple of years ago.
On the UK one, I think the engine company loaned them the engines.

rwolfe9

Thanks! That makes things a lot easier! Maybe I need to build an X-15 to go on it too.

Sharku

[X(]

that would be awesome do it , get some rocket motors [relatively cheap ..here..] guessing with the size of it it should be able to carry a good sized payload, if you ever make the x-15 do post

Villa

That sure is a big project. Big plane like that will take a long runway. Are you in an R/C club with a long runway? What other R/C planes have you built and flown? I'm looking forward to your build.

rwolfe9

I was kind of kidding about the X-15, but might have to use rocket motors anyway. The runway our club has is about 300' long. If the plane won't stop quick enough with the air brakes I plan to install, I'm going to try about 3 parachutes. Saw those on some of the real B-52 pix.

I have thus far scratch built a 42" Sopwith Camel, built a P-51 from a standard Guillows stick balsa kit (30"), my son and I built a P-51 also from a Guillows kit with a 17" span, retracts, 7oz, and enough power for 3D. Waiting for the rx to get here so we can try it. Will have to wait for a calm day or do it indoors. It'll probably be too fast for indoors. To be honest I have been building planes and not yet flown them. That's for this year. I built a Piper Cub for a first plane, and found out about tip stall the hard way. My next plane is the 30" P-51, but I was told it was too fast for me to start with. That's why the Camel. It has a huge wing area for very stable flight. My kid already has had his pilot's license for a year, so I will have to catch up. I like building them more than flying them(so far, sure that will change).

Props4ever

This is interesting to know that NASA bolted the flaps of there B-52B that was used in various experiments they had including launching X-15s...I'm not being smart***** on here but dosen't B-52s have 2 sets of flaps, inboards and out boards on each wing. Now being such a heavy aircraft, i would least think if they did bolted the flaps wouldn't they just be inner ones and not outer ones!. I would imagine even without caring any internal/external pay loads, this aircraft would still need flaps on landings at least.

rwolfe9

Since we are running EDF's, do youall think that if we put some relays to lockout 4 motors and to reverse 4 motors operated by channel 6 and the throttle that it wouldn't rip off the pods(4 on 2 pods to cancel torque) or break the fan blades?

TFF

No flaps used they had all of Edwards to land at. I think they have 20,000+ft of runway that can be actually used. They had great pilots; Neil Armstrong almost did not take the Astronaut gig because he was up for chief pilot at Edwards and was flying the B-29 drop ship. I am sure they could have re-engineered but they saw no need; the planes were SN 52-003 and 52-008 and I think they were the lowest time B52s but NASA went to a later model because parts were easer to get. I think both 003 and 008 are in museums.

BMatthews

Keep the model light for it's size and low in wing loading for the size and you won't need the flaps. Try to shoot for a wing loading somewhere between what a 12foot open class sailplane has and the lighter power models of the 100 inch class. I'm going to guess that this would end up at around 20 oz/sq foot. Based on your claim of a 12 foot span or 144 inches I make this out to be around 17 sq feet of area. If we shoot for a 20 oz/sq foot loading that's 20 x 17 = 340 oz or just a bit over 21 lbs. With care and not many scale details I think this is doable and not have too light a structure. After all scale gliders in the same span and fuselage size range are coming in at around this weight.

But more to the point is the amount of weight each motor will need to carry. You'll have 8 fans with each being expected to carry a 2.63 lb portion of the work. To find out if this works out look at models that use these fan units as single fan designs and see what weight they are flying at and just exactly how well they fly. And remember, just because it's a model of an F15 that does not mean the little fan unit is pushing the model around in a truly scale like manner. You'll want to see first hand flying movies or real life flights of models with these units in them. If in doubt build a hack model with one fan unit that has 1/8 of the 17 sq foot wing area and power it with a fan unit and ballast it up to around 36 oz. I make such a test goat to be 334 sq inches area and 36 oz. Not a bad combo. If this single fan test model can fly in a "B-52 like" manner then I think your project is off to a really good start. For examples of how to build big but strong structures study some open class glider plans for wing and spar details. Honestly you'll also gain some efficiency due to the model being so large so even if it comes out to 25'ish lbs overall I don't see any issues. But do try to keep it under control. EDF's are not known for their blustering power output so you're going to need all the help you can arrange in that regard.

For example my first take on a fuselage structure for such a model would be a square box structure that uses something like 1/4 sq aircraft spruce and a full on warren truss of medium balsa. In other words look at the big crane booms that are built up with all the diagonals and copy that. Onto this box "crutch" I'd slab on pieces of blue or pink syrofoam. Then cut all the excess away to reveal the hidden B-52'ish nature of its soul Onto this I'd glass on some really light fiberglass and epoxy. Something like 2 oz cloth and as little resin as you can manage to use and still make the cloth go clear. Of course various areas of the basic crutch would require beefing up for things like the wing and landing gear mount points and the hatches to allow the placement of the battery packs for the motors. But I think you'll find that a structure of this sort would come out quite light IF you keep the fiberglass content under control.

With these sorts of weight in mind you won't need the complexity and complications that flaps would bring. It'll land in a very glider like manner at that wing loading. And from what I've seen about EDF's you'll want to keep it down to around this sort of weight anyhow or the EDF's won't be able to move enough air to make it climb well. And in this case "climb well" does not refer to a jet fighter like performance that most of us modellers aspire to. Im suggesting that if it's much over 23 to 25 lbs then it won't even be able to "glide uphill" decently depending on the performance that these EDF units and motors can muster.

Props4ever

I found few pictures of NB-52A and B on the web, NB-52B 008's pictures show that IB flaps were sealed off/bolted off but OB were still deploy able. I haven't come across any landing pictures of these aircraft as yet but all are off taking off and yes NO FLAPS were used in take offs!, in a way that was cool as B-52 would take off as normal airplane Vs Guppy style!....

Props4ever

Bill,

How can wing flex curvature of actual aircraft be made on RC model wings!, Man that's huge flex curvature!, i know how BB Weber replicated it of his Tu-95 but that would be at outer wings Vs B-52 where it's right off the inner wing section...

TFF

So they did have some flaps; not much though. It sure would have been cool to see 003 and the X-15 together.

Props4ever

Here you go, your wish come true...

Yes they did as i suspected they would have to use some flaps specially for landings...

Props4ever

Here are some more unique B52 experimental and test bed vehicles...

RB-52E CCV
B-52E as PW JT9Ds engine test bed vehicle.

rwolfe9

Much thanks to all!

Props4ever

No problem, i try to help where ever i can.
Are you going to do build thread on here, it would be great to see your model's progress.
How did you designed your 52s wings in terms of construction of them. Would they be built up type or foam core type and what sort of spar box have you planned for it as that will be the major key to the wing's structural integrity.

rwolfe9

Duh, what's a spar box?

Props4ever

Sorry i meant by box spar with sheer web.

rwolfe9

Right now I have the main spar long enough to extend through the fuse into the opposite wing. It is 3/4 x 1-1/2 poplar. That is the idea for now, more details after I get farther.



Beware Murphy's Law!

rwolfe9

More than one way to skin a cat.

Props4ever

Here are couple more nice dramatic shot of various B52s...

I'm including picture of NB-52A 003 after it's retirement in 1986 as it was stored at Pima Air & Space Museum

Props4ever

So this means that your wings are built up, i mean foam wing could have same length of spar also. Poplar is good wood to use but will your wings flex a bit with this spar or would they be solid constantly...

rwolfe9

Right now it is fairly rigid, with about a 2" bow with a force of about 10lbs applied at the middle. If I'm seeing it correctly, the real B-52 on the tarmack has no dihedral, it is created in flight when the weight is taken up by the wings. Also, I'm wondering how much torque I'm going to need to operate the control surfaces. I was considering putting 2 standard Futaba servos in tandem to operate each aileron. Also, I'd like to completely enclose the servos and rods in the wings. I think the lever arms would have enough room in the wing. Does anyone have some formulas for these processes?

Props4ever

Here you go Robert, Servo calculator...

http://www.scaleaero.com/Servos_To_Use.htm

As for dihedral is concerned, there is none on B-52!, what you see those in pictures is "wing flex curvature", it happens due to weight of the payload that aircraft is carrying.

I am also coming to conclusion that 52s don't have anhedral also, it's more of optical illusion then anhedral!. The reason i say this is, if you look at the pictures where aircraft has very little fuel load in the wings, outer wing LGs don't even stay on the ground, they suspend in the air as wing at that time doesn't even curve down!. So basically when there is a lot of fuel load on board in the wings, wings curve down otherwise they stay straight.