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Boeing B52 stratofortress build

#1
Hello guys, trust you are all fine. Please I need your technical advice.

I would like to build an RC B52 stratofortess with a wing span of max 60cm. I would like the model to be to scale and also realistic. I would like to power it with electric ducted fans.This leaves me in a dilemma because there are no electric ducted fans small enough to fit in the scaled jet engine housing of the B52.

Can I use a single electric ducted fan placed in the fuselage of the B52 with the exhaust directed to exit through the rear of the aircraft as obtains in aircraft like the U2 spyplane. Would such an arrangement be powerful enough to propel the B52

Any pictures or weblinks of RC B52s that were built in this manner will be highly appreciated.

Thank you my dear friends. Awaiting your kind responses
 

DamoRC

Well-known member
Mentor
#2
Using a single EDF in the fuse is a viable option but if you are trying to maintain scale looks on a 60cm wingspan you're EDF will still be on the smaller side. From drawings I have done previously, a scale fuse for a 60cm wingspan will be approx. 25-30mm diameter. I would guesstimate that your all up weight will be in the 300-400 gram range if you build lightly. See if you can get a 25 or 30 mm EDF unit with 300 grams thrust and design around that unit.

DamoRC
 
#3
Using a single EDF in the fuse is a viable option but if you are trying to maintain scale looks on a 60cm wingspan you're EDF will still be on the smaller side. From drawings I have done previously, a scale fuse for a 60cm wingspan will be approx. 25-30mm diameter. I would guesstimate that your all up weight will be in the 300-400 gram range if you build lightly. See if you can get a 25 or 30 mm EDF unit with 300 grams thrust and design around that unit.

DamoRC
Thank you very much. Your measurements are very correct, the fuselage diameter is 30mm. Do you think the thrust from the EDF will be decreased if inserted in the middle of the fuselage and then conducted through channels to emerge at the back of the B52 where it will emerge through a smaller nozzle
 

DamoRC

Well-known member
Mentor
#4
Thank you very much. Your measurements are very correct, the fuselage diameter is 30mm. Do you think the thrust from the EDF will be decreased if inserted in the middle of the fuselage and then conducted through channels to emerge at the back of the B52 where it will emerge through a smaller nozzle
You will lose some thrust by increasing the thrust tube length but placing it close to or in the middle of the fuselage is a good idea to ensure that you will be able to balance the plane correctly for flight. Regarding the exhaust, a typical exhaust diameter will approx 90% of the fan swept area (FSA) of the EDF. So it will be a little narrower, but you don't want to choke it off to much or you will lose a lot of thrust (depending on the EDF) . Remember to figure the thickness of foam into your calcs for choosing an EDF (30mm outer diameter will be ~ 20-22 mm diameter internal).

DamoRC
 
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DamoRC

Well-known member
Mentor
#5
Quick update - looks like most of the 30mm EDFs I see are in the 200 gram thrust range. Had another look at the drawings and you could probably keep the airframe a lot lighter than the 300-400g I originally quoted (in foamboard, you could probably build a bare airframe weighing 100 grams. I think building around a 30mm unit is viable.

DamoRC
 
#7
Hello guys. Thanks for your responses. Considering my limitations in materials, I decided to switch and build a B17 flying fortress. However, the only control it would have will be the speed of the propellers. I won't be using any servos since i dont have any and it is not readily available where I live. I intend for it to take off in when the propellers are spinning at max rpm and to land I intend to just reduce the rpm of the propellers and hope it will glide safely to the ground without crashing. How practical is this. Do you think it would work? Any advice?
 

d8veh

Well-known member
#8
What about buying a cheap quadcopter and using its electronics, like FT did for their rc paper dart. You could use the drone's flight controller for differential thrust to steer the plane and the throttle to co trol the height. You can buy cheap drones with a transmitter for not much more than $10.

When you scale a model like that, the tail will be too small to control the plane, so don't forget to enlarge them. Make a profile glider first to see what works if you haven't done anything like that before.
 
#9
Thanks so much d8veh. I actually intended to make use of the electronics, motors, propellers etc of a quadcopter like you suggested. If I reduce the thrust of my plane, do you think it can safely land without me using flaps, ailerons, servos etc. Because i dont havethe resources to include them in the plane.
 

d8veh

Well-known member
#10
Thanks so much d8veh. I actually intended to make use of the electronics, motors, propellers etc of a quadcopter like you suggested. If I reduce the thrust of my plane, do you think it can safely land without me using flaps, ailerons, servos etc. Because i dont havethe resources to include them in the plane.
I've flown every type of RC plane from 12" upwards and I've never yet had to use flaps. One or two of my planes had them, but I didn’t use them. They're only really needed on big planes to slow them down enough to land on a short model flying strip/runway.
 

d8veh

Well-known member
#12
Thanks d8veh. From your response, I can safely land my plane by just reducing the throttle right?
Sort of. You have to learn to fly and trim model planes first. A B52 isn't exactly an ideal starter plane. It depends on how light it is. You'll probably need to increase the dihedral to get stable flight.

Another thing: You can buy cheap twin engined RC planes for about $20. The electronics from one of them might work too as long as you find one large enough. Maybe this one. At least you can have fun flying it while you figure out your B52:
https://www.ebay.co.uk/itm/Z51-660m...trksid=p2047675.c100010.m2109&redirect=mobile
 
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#13
Sort of. You have to learn to fly and trim model planes first. A B52 isn't exactly an ideal starter plane. It depends on how light it is. You'll probably need to increase the dihedral to get stable flight.

Another thing: You can buy cheap twin engined RC planes for about $20. The electronics from one of them might work too as long as you find one large enough. Maybe this one. At least you can have fun flying it while you figure out your B52:
https://www.ebay.co.uk/itm/Z51-660m...trksid=p2047675.c100010.m2109&redirect=mobile
Thanks so much.