Thread Tools
May 04, 2017, 12:34 PM
Registered User
Wonderful project. Just curious, how much oversize from scale will you need to make the engine nacelles to fit the fans? I ask because I made a similar size model as a static display for my office (but put in control rods in case I wanted to try it as a PSS some day) when I was in the USAF, and the scale size nacelles were way too small to even think about EDFs...Pete M
Sign up now
to remove ads between posts
May 04, 2017, 01:39 PM
Registered User
fuelsguy's Avatar
Names, where I was born and raised, in South Wales, there were quite a few Ivor's around. Some spelt the correct Welsh way of Ifor. (Pronounced with a v sound not an f sound) Very rare in the USA. In my work at the FAA most people forgot my last name and I was simply Ivor in a lot of correspondence. Ivar, the Scandinavian version, is much more usual.
In Seattle there was a famous restaurateur named Ivar Hagland, so people assume that's how I spell my name.

Back to the B-52 thread.
I laid out a KC-135 at 1:27 scale and the 64mm EDF looks a very nice match to the nacelle size. Now I have to decide to build or not to build and how to get it in my Subaru..
Ivor
May 04, 2017, 01:56 PM
Registered User
pmisuinas
Nice model but are the nacelles on your model true scale?
It you start with a B52H that uses turbo fans at 7 ft span you can get a 35 mm EDF in a scale nacelle relatively easily.

Sparks
I do wonder about your concept of not using full power.
My guess is you probably will have to and you certainly have to set up the electrics so that it can be used.
This leads on to another issue. I presume the battery(s) go in the fuselage which means you are going to have to run long wires thick enough to carry current out to the EDFs. I suspect you will find the total wire weight will start to become significant (as heavy as the EDFs?) particularly for the outboard pair.
Then you have to consider where to put the ESCs and how to cool them.
Ideally they should be fairly close to the battery to avoid voltage spikes. You can use additional capacitors to allow longer wires but even then with multi EDFs you can get some odd effects.
I had to re-position the ESCs to be closer to the battery on my 8 ft long scratch built scale Depron Concorde (4x40 mm EDFs total 60A from one 2s) before I could get all the fans to perform reliably.
Name: Complete.JPG
Views: 134
Size: 115.4 KB
Description:
I would suggest that you build a 'working' nacelle to see how much thrust it generates and at what amps before you commit to building the air frame.
May 04, 2017, 03:30 PM
Mike
i12flyrc's Avatar
Sub'd
Mike
May 04, 2017, 03:35 PM
RC 4 Life
sparks's Avatar
Thread OP
I'm building the model around the Fans so the inlet will be/is scale.
As for wire, the AWG starts heavy and reduces as they go out board to save weight .

Batteries, two ea. two cell 5000 MAH.
This gives me plenty of options to work with.

My thrust test shows I'll have a little less than half the projected weight of the model.
Plenty for a plane that is basically a glider.
May 04, 2017, 04:10 PM
Rotormantic
FNFAL's Avatar

B-52 Future


Airforce plans to fly the B-52 for 100 years.

http://www.thedailybeast.com/article...ear-old-planes

When you approach the Airforce academy in Colorado Springs, you can see a beautifully mounted 52 by the roadside...and of course the one here in the good ole AF museum.
Last edited by FNFAL; May 05, 2017 at 12:20 PM.
May 04, 2017, 04:41 PM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
Worked D models at Dyess in Abilene back in the 70s... nice to see the tall fin...
May 04, 2017, 04:56 PM
Registered User
Quote:
Originally Posted by Quorneng
.....

This leads on to another issue. I presume the battery(s) go in the fuselage which means you are going to have to run long wires thick enough to carry current out to the EDFs. I suspect you will find the total wire weight will start to become significant (as heavy as the EDFs?) particularly for the outboard pair......
I'm surprised you didn't mention the use of solid magnet wire to save weight. You've used it on several on your light weight EDF models haven't you?
May 04, 2017, 05:07 PM
RC 4 Life
sparks's Avatar
Thread OP
No,
The idea here is for an average builder to have a B-52.
If I go crazy with cost, builders would turn away .
Id rather have two guys show me how to do it "right" and have several build it to have fun without breaking their hobby bank.
May 04, 2017, 05:52 PM
EDF rules... :)
AirX's Avatar
Hey Keith, great to see the Buff coming together.
Hope to see it at BEST this year.

Cheers,
Eric B.
May 05, 2017, 07:11 AM
Registered User
Quote:
Originally Posted by Quorneng
pmisuinas
Nice model but are the nacelles on your model true scale?
It you start with a B52H that uses turbo fans at 7 ft span you can get a 35 mm EDF in a scale nacelle relatively easily.
As far as I was able to tell, yes, they are scale, for the SE Asia D version...but yes, I can see where the turbofan version would provide the extra size needed...Pete M
May 05, 2017, 10:56 AM
Build'm,Fly'm,Crash'm
redlite's Avatar
Great! Here's an awesome project that's rarely seen. My meager attempt awhile ago...

This was built in the early 90's, based on Don Ross's (legendary Scale Free Flight-er, who died January, this year) free flight Mig 15. Typing paper wound around a mandrel (plexi tube) and then wet balsa strips wound around for bulkheads, using white glue for the adhesive. Way stronger than you'd think and at 36 grams per pod, minus the electronics, made the project feasible. He used tissue paper for the Mig 15 skin and my pod uses 1/32 sheet. The motors for the fans were done using Don's kit and instruction sheet, stripping the fine wire out and rewinding with the heavy wire supplied...micro electric motors that could spin a fan back then were non-existent, so this is what you did. Still needed more fairings to finish, mount the motors...but this where I left off. The enormity of the project was too much, so this was mostly a learning lesson.

Curious what one of the foam pods weigh in at, minus the electrics?

Mine has a 2 inch (50mm) gaping intake.

Scale inlet diameter is key to the look of this model when in flight, something that would have been impossible even a short while ago, but the exit exhaust diameter makes rivet counting a moot point for the nacelles.

Joe
May 05, 2017, 03:51 PM
EB-66C Team Member
J Morgan's Avatar
I can only clean the shop so long before the building itch gets unbearable. Haven't even unpacked everything from the trailer( SEFF) but I did bring in
my building equipment.
I got started on the fuse. Tack glued two pieces of foam together having traced the sides out on the top one. Same on top & bottom pieces. Not easy to handle but I cut the sides, top & bottom out on the band saw. I've found trying to cut any foam over 1/4" thick is problematic with an exacto or snap off blade. The blade tends to "hunt" and I can never get a consistent vertical cut. Band saw cures that problem.
Cut out the sides, top & bottom and then glued the top & bottom to one side per Sparky's instructions. I wipe a damp rag across the gluing surface to activate the Gorilla glue and use books to hold them steady. Then I keep checking vertical for the next 20 min. By then they aren't going to move.
I'll get the other side glued today but that's about all the progress for today.

J
May 05, 2017, 06:52 PM
RC 4 Life
sparks's Avatar
Thread OP
I missed the "getting the foam damp step", thanks john.
It helps a bunch at filling surface imperfections.
May 05, 2017, 06:57 PM
RC 4 Life
sparks's Avatar
Thread OP

Fuselage shaping


By now you know what is next, the fuselage is much easier to shape if you have a long standing bar.
I stick 90 grit paper to the sanding bar with two sided tape. If you can't find a long sheet of sand paper buy a cheap sanding belt and cut it.
Apply light pressure and let the sandpaper do the work.
Count your strokes, let's say 25.
Rotate the fuselage to the next corner and do 25 more. repeat.
This method will go a long way toward shaping it evenly.
As you get closer to the final shape reduce the grit to 120 then 180 .
Just be glad your shop is not 100 degrees, this stuff will stick to you unless you have a fan to blow it into the backyard.
16 thru 23


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Advice for building 5 ft wing span/12 lbm model airplane? mutyo051026 Modeling Science 4 Sep 23, 2016 04:26 PM
Discussion 4-ft span foam glider from Wal-Mart, converted to R/C? Little-Acorn Foamies (Kits) 433 Mar 29, 2015 11:09 AM
Discussion 7 ft. span 757 - my first DF project sparks RC Airliners (Commercial, Cargo, Troop Carrier) 400 Feb 17, 2012 06:59 AM
Discussion 7 ft foam and balsa eagle. macboffin Foamies (Scratchbuilt) 5 Feb 20, 2011 04:55 AM
7 Ft. Span Airliner keith sparks Foamies (Kits) 41 Jun 09, 2004 12:16 PM