Wattflyer RC Network: RC Universe :: RCU Magazine :: RCU Forums :: RCU Classifieds :: RCU User Reviews :: RCU YouTube
Home Who's Online Calendar Today's Posts RealTime Post Spy Mark Forums Read
Go Back   WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > Scratch and Kit Built Aircraft
Register Members List Wattflyer Extras Articles Search Today's Posts Mark Forums Read Social Groups

Scratch and Kit Built Aircraft Discuss and share your scratch built or kit built aircraft as well as building techniques, methods, mediums and resources.

Thank you for your support (hide ads)
Reply
 
Thread Tools Display Modes
Old 10-30-2014, 04:50 PM   #1
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,263
Thanked 42 Times in 41 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (7)
Default $100 EDF Scratch Build Contest - EE Canberra

The English Electric Canberra is one of my favourites. A classic example of how to get the best out of the available power.

With this build the question is going to be can I get cheap 30mm EDFs to satisfactorily fly a scale (or as near as possible scale) airframe? I suspect it will be pretty marginal.

So which of the many Mks of Canberra? Actually the basic airframe changed little (discounting the big wing B57s!) so I think I will choose to model the prototype. Simple to paint as it was pale blue over all.
Click image for larger version

Name:	protocolour.jpg
Views:	51
Size:	157.5 KB
ID:	178160
This is actually a later T4 that was painted to look like the prototype in 1999 to mark the anniversary of the Canberra's 50 years in service with the RAF.

With the very limited thrust available (6oz in total if I am lucky!) it will have to be reasonably big to carry the weight efficiently but very, very light.

I think I have been here before!


quorneng is offline  
  Reply With Quote
Old 10-30-2014, 06:16 PM   #2
xmech2k
Ya got any Beeman's?
 
xmech2k's Avatar
 
Join Date: Apr 2009
Location: San Diego, CA
Posts: 2,756
View xmech2k's Gallery21
Thanked 261 Times in 259 Posts
Club: CVMRCC, SEFSD
Awards Showcase

Scratchbuilders Award  1kW  Outstanding Contributor Award 
iTrader: (0)
Friends: (8)
Default

Welcome on board, quorneng! Can't wait to see your build. The Canberra is another rarely modeled planes that deserves better. I got to see the full scale big wing B-57 you mentioned at the Pima Air & Space museum. Looked freaky! I think I read it was created sort of as a back up plan in case the U-2 project didn't work out. Good luck!
xmech2k is offline  
  Reply With Quote
Old 10-31-2014, 03:22 AM   #3
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,263
Thanked 42 Times in 41 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (7)
Default

At the moment this post is more "thinking out loud" than a description of the build of a Canberra with 30mm EDFs.

To my horror Hobbyking quote the thrust of the AEO 30 at just 1.6oz (48g) but of course this is likely to be the 'free air' static thrust so rather less (30%?) when it is in what will be quite a long duct - even in a Canberra!

It would appear to me that for a small diameter fan in a relatively big light airframe its flying speed will be modest so it will pay to optimise the static thrust rather than worry how fast it might go. It follows this is best achieved by mounting the fan well aft to keep the thrust tube short and use the maximum possible inlet duct diameter within scale dimensions.

This is roughly the proportions of a Canberra engine nacelle.
Click image for larger version

Name:	EDFduct.jpg
Views:	12
Size:	38.6 KB
ID:	178169
With a 30mm EDF actually as the scale jet pipe the thrust tube is the Fan Swept Area (FSA) and it is possible to have the whole inlet duct with no less than 3 times the fan area area. In this configuration it should hopefully develop pretty close to its 'free air' thrust figure.

With a 30mm scale jet pipe the Canberra would have a span of 29" (720mm) which sounds reasonable but to stand much chance of flying with no more than 3 oz thrust it should weigh no more than 6 oz (170g) complete.
Hmmm!


I understand the really big wing B57 actually came into being after Gary Powers had been shot down and U2 over flights were banned so they needed a high altitude plane that could carry the bigger payload of the sideways looking equipment that could be used safely from outside (just!) the Soviet borders.


quorneng is offline  
  Reply With Quote
Old 10-31-2014, 05:12 AM   #4
xmech2k
Ya got any Beeman's?
 
xmech2k's Avatar
 
Join Date: Apr 2009
Location: San Diego, CA
Posts: 2,756
View xmech2k's Gallery21
Thanked 261 Times in 259 Posts
Club: CVMRCC, SEFSD
Awards Showcase

Scratchbuilders Award  1kW  Outstanding Contributor Award 
iTrader: (0)
Friends: (8)
Default

Originally Posted by quorneng View Post
...


I understand the really big wing B57 actually came into being after Gary Powers had been shot down and U2 over flights were banned so they needed a high altitude plane that could carry the bigger payload of the sideways looking equipment that could be used safely from outside (just!) the Soviet borders.
I stand corrected. I'll have to do some more reading on the subject.

Looks like those little edf's may be a challenge. I hope it works well. I'm a little confused about you choosing very large intakes though. I can't speak from experience, only what I've read, and that is that a 90% fsa intakes area was optimum. Having more could create extra drag, as the edf can only pump so much air. Is that only in the faster edf's?
xmech2k is offline  
  Reply With Quote
Old 10-31-2014, 01:03 PM   #5
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,263
Thanked 42 Times in 41 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (7)
Default

xmech2k
I estimate my Canberra will fly at about 20mph as a result of a very low wing loading whereas the fan exit speed will be perhaps 3 times that.
This would mean that the air would simply enter the inlet at more or less flying speed so it would not create any 'drag' as such, at bit like the big turbo fans that look to have a ridiculous frontal area for 600mph but of course they don't create drag either - as long as they are running!
quorneng is offline  
  Reply With Quote
Old 11-01-2014, 02:54 AM   #6
Bill G
Super Contrubutor
 
Bill G's Avatar
 
Join Date: Oct 2005
Location: West Central PA
Posts: 4,298
View Bill G's Gallery86
Thanked 177 Times in 171 Posts
Club: rcg staff
Awards Showcase

Outstanding Contributor Award  Outstanding Contributor Award  Scratchbuilders Award 
iTrader: (3)
Friends: (17)
Default

You could always run an internal fan. The ducting is inefficient, but the fan is much more powerful. On the Comet I have around 22-23 oz of thrust, which on paper should fly the roughly 50" airliner given it's relatively light AUW for it's size.

I had the same concerns, as the 30mm EDFs have low thrust, but are as large as possible to maintain a reasonable scale appearance at somewhere in the 50" span range. 40mm EDFs have exponentially more thrust and would be much more practical, but would be too large for the nacelles for a reasonable scale appearance unless the jet grew to a size where the AUW would likely become unreasonable.

Some of the thrust figures I see advertised for 30mm EDFs seem a bit overstated. Of course I never experimented with the purchase ones, but the 30mm GWS EDFs I was remotoring with the 12mm Feigao inrunner would be lucky to produce much more than 1oz, and were still stressing those tiny fan blades to the point that I would have a difficult time seeing them withstand much more.


Attached Thumbnails
Click image for larger version

Name:	Comet4_12.jpg
Views:	57
Size:	110.8 KB
ID:	178188  
Bill G is offline  
  Reply With Quote
Old 11-02-2014, 01:50 AM   #7
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,263
Thanked 42 Times in 41 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (7)
Default

Bill G
That is a very interesting picture and represents another way of overcoming the inherent lack of efficiency of small fans.

I did use this sort of principle in my XB70 Valkyrie where a single 'buried' 70 mm fan fed six 28 mm diameter nozzles. It certainly works well enough although it does have the advantage of being a more or less 'straight through' duct.
quorneng is offline  
  Reply With Quote
Old 11-02-2014, 09:51 AM   #8
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 4,491
Thanked 492 Times in 458 Posts
Awards Showcase

5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (8)
Default

I used one of those AEO fans in the 17" freeflight Mig 17 I build a few years ago (pic below). I got a lot more than 48g out of it. On a 2s LiPo it produced about 84g thrust in free air. But this did drop significantly when installed in the long duct of the Mig.

I tested a range of fans for the Mig, see picture below. From left to right is the GWS EDF30 with Turnigy 1015 brushless motor (48g thrust), the AEO 30mm fan (84g), the KP aero fan (74g) then the GWS and AEO 40mm fans. Also attached is thrust test picture of the AEO 30mm to verify my numbers.

Good luck with the project.

Steve


Attached Thumbnails
Click image for larger version

Name:	P1010601.jpg
Views:	47
Size:	147.4 KB
ID:	178200   Click image for larger version

Name:	Fans.JPG
Views:	48
Size:	68.0 KB
ID:	178201   Click image for larger version

Name:	thrust_test.JPG
Views:	47
Size:	84.6 KB
ID:	178202  
JetPlaneFlyer is offline  
  Reply With Quote
Old 11-02-2014, 04:04 PM   #9
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,263
Thanked 42 Times in 41 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (7)
Default

Steve
84g from each fan would certainly give me some useful performance.
I shall have to test mine in the same way to check.

To begin with I intend to build just an engine nacelle to find out how much thrust goes missing!
quorneng is offline  
  Reply With Quote
Old 11-02-2014, 06:37 PM   #10
Bill G
Super Contrubutor
 
Bill G's Avatar
 
Join Date: Oct 2005
Location: West Central PA
Posts: 4,298
View Bill G's Gallery86
Thanked 177 Times in 171 Posts
Club: rcg staff
Awards Showcase

Outstanding Contributor Award  Outstanding Contributor Award  Scratchbuilders Award 
iTrader: (3)
Friends: (17)
Default

Originally Posted by quorneng View Post
Bill G
That is a very interesting picture and represents another way of overcoming the inherent lack of efficiency of small fans.

I did use this sort of principle in my XB70 Valkyrie where a single 'buried' 70 mm fan fed six 28 mm diameter nozzles. It certainly works well enough although it does have the advantage of being a more or less 'straight through' duct.
The Comet ducting certainly wasn't as ideal as something like the XB70. I probably lost something like 60% or more thrust, although 22-23oz still should fly the plane on paper. Done again it would have been a bit cleaner, but when you haven't finished a build it's difficult to envision the exact amount of room available to keep things reasonably scale. The joining "V" of the two exits would have been a bit further rearward, done again.


Originally Posted by JetPlaneFlyer View Post
I used one of those AEO fans in the 17" freeflight Mig 17 I build a few years ago (pic below). I got a lot more than 48g out of it. On a 2s LiPo it produced about 84g thrust in free air. But this did drop significantly when installed in the long duct of the Mig.

I tested a range of fans for the Mig, see picture below. From left to right is the GWS EDF30 with Turnigy 1015 brushless motor (48g thrust), the AEO 30mm fan (84g), the KP aero fan (74g) then the GWS and AEO 40mm fans. Also attached is thrust test picture of the AEO 30mm to verify my numbers.

Good luck with the project.

Steve
Very true. The raw spec is really optimistic when compared to mounted in ducting. Your photo got me thinking about how the GWS fans like the EDF40 and 50 are among the fewer small fans without a lip. When I tossed around the idea of mounting fans in Comet nacelles, the EDF40 was as appealing as the smaller 30mm fans, since it had no lip and would keep the nacelle diameter as scale as possible. Of course the 30 could always be hacked down, but some CF wrapping or something similar would be a good idea for rigidity. That KP fan looks interesting, appearing to have no intake lip and a reasonable wall thickness.
Bill G is offline  
  Reply With Quote
Old 11-02-2014, 09:59 PM   #11
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,263
Thanked 42 Times in 41 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (7)
Default

I actually machined off the lips of the four 40mm AEO I used in my Concorde with a lathe. I did not disassemble them but simply held the fan casing in a 3 jaw chuck and very carefully 'parted off' the lip section with a very fine (and sharp!) tool.
Quite nerve raking as the EDF could not be held that firmly in the chuck and if it did moved the EDF would be destroyed.

In the Canberra by making the EDF the actual jet pipe the scale nacelle is large enough to allow the lip to be retained.
quorneng is offline  
  Reply With Quote
Old 11-02-2014, 10:02 PM   #12
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 4,491
Thanked 492 Times in 458 Posts
Awards Showcase

5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (8)
Default

On my Mig i just extended the inlet ducting into the throat of the fan, just far enough so it 'bypassed' the bellmouth.
JetPlaneFlyer is offline  
  Reply With Quote
Old 11-15-2014, 02:15 AM   #13
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,263
Thanked 42 Times in 41 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (7)
Default

As my current project is neraring completion I can start thinking about the Canberra.
First task is to create an 'outline only' 3 view.
Click image for larger version

Name:	SimpleB2s.jpg
Views:	10
Size:	80.9 KB
ID:	178370
This has been developed from on a nice scale 3 view drawing so it should be reasonably accurate.
On reflection I think a B2 (camo top, all black under) will be more visible than the pale blue overall of the prototype.


quorneng is offline  
  Reply With Quote
Old 11-22-2014, 01:57 AM   #14
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,263
Thanked 42 Times in 41 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (7)
Default

A bit more drawing.
A scale Canberra nacelle with a 35mm EDF right at the back acting as a slightly over scale jet pipe.
Click image for larger version

Name:	EDFduct1.jpg
Views:	6
Size:	41.7 KB
ID:	178465
This allows virtually the entire inlet duct to be just over twice the FSA which should significantly reduce the duct losses.
However
Done like this the Canberra will come out rather larger than I had intended at 40" (1016mm)span.

Putting the EDF right at the front of the nacelle would allow the overall size to be reduced a bit to about 35" span, the fan bell mouth could be retained (good for low speed thrust) and the spinner would be a reasonable representation of the Avon's 'bullet' but I fear the losses resulting from the long 35mm exhaust duct would be greater than with the EDF at the back.

"I think I had better think it out again!".


quorneng is offline  
  Reply With Quote
Old 11-23-2014, 11:03 PM   #15
Bill G
Super Contrubutor
 
Bill G's Avatar
 
Join Date: Oct 2005
Location: West Central PA
Posts: 4,298
View Bill G's Gallery86
Thanked 177 Times in 171 Posts
Club: rcg staff
Awards Showcase

Outstanding Contributor Award  Outstanding Contributor Award  Scratchbuilders Award 
iTrader: (3)
Friends: (17)
Default

I'm blaming you for this one Quorneng.
Since I've never gotten around to finding an adequate field for my larger version, I just printed out 30 sheets for a smaller, 33" span, hand launchable version with a centrally mounted EDF. There's something about these sleek, integral wing nacelles that draws us to these subjects. Not surprising, I believe Chris Golds has modeled both of these subjects.


Attached Thumbnails
Click image for larger version

Name:	comet_33in.jpg
Views:	14
Size:	658.1 KB
ID:	178478   Click image for larger version

Name:	Comet4_111_25percent.jpg
Views:	12
Size:	124.5 KB
ID:	178479  
Bill G is offline  
  Reply With Quote
Old 11-24-2014, 01:55 AM   #16
xmech2k
Ya got any Beeman's?
 
xmech2k's Avatar
 
Join Date: Apr 2009
Location: San Diego, CA
Posts: 2,756
View xmech2k's Gallery21
Thanked 261 Times in 259 Posts
Club: CVMRCC, SEFSD
Awards Showcase

Scratchbuilders Award  1kW  Outstanding Contributor Award 
iTrader: (0)
Friends: (8)
Default

Bill G, my (stolen from Chellie) offer to maiden that Comet for you still stands, if you care to make the short drive over here! Our did it happen already and you didn't tell us?
xmech2k is offline  
  Reply With Quote
Old 11-24-2014, 05:51 AM   #17
Bill G
Super Contrubutor
 
Bill G's Avatar
 
Join Date: Oct 2005
Location: West Central PA
Posts: 4,298
View Bill G's Gallery86
Thanked 177 Times in 171 Posts
Club: rcg staff
Awards Showcase

Outstanding Contributor Award  Outstanding Contributor Award  Scratchbuilders Award 
iTrader: (3)
Friends: (17)
Default

Originally Posted by xmech2k View Post
Bill G, my (stolen from Chellie) offer to maiden that Comet for you still stands, if you care to make the short drive over here! Our did it happen already and you didn't tell us?
Might think about it, with the weather as of late. May even think of going to the UK and having Quorneng fly it. Still better weather than here.
Bill G is offline  
  Reply With Quote
Old 11-24-2014, 08:27 PM   #18
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,263
Thanked 42 Times in 41 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (7)
Default

Bill G
If you come over, I would fly it!

A bit more doodling with a comparison of EDF at the front and the back of the Canberra engine nacelle.
Click image for larger version

Name:	EDFductsS.jpg
Views:	4
Size:	32.0 KB
ID:	178486
The EDF are the same size (a cut and past!) but as I hoped is does allow the nacelle and thus the entire airframe to be reduced by 15%. My biggest concern is the losses resulting from the long & small diameter exhaust tube.
I have shown an 'after body' behind the EDF that brings the 'annular' airflow from around the out runner bell efficiently to a circular duct of 27mm diam.

On balance I think I will try the 'fan at the front' option first as it will have a better scale appearance and the fact that the duct is a smaller diameter allows more space for the wing spar to go 'over and under'.


quorneng is offline  
  Reply With Quote
Old Yesterday, 02:46 PM   #19
quorneng
Super Contributor
 
quorneng's Avatar
 
Join Date: Jul 2008
Location: Cheshire, UK
Posts: 1,263
Thanked 42 Times in 41 Posts
Club: A lone flyer!
Awards Showcase

Scratchbuilders Award 
iTrader: (0)
Friends: (7)
Default

Still doodling away but it is starting to come together.
With a 30 mm EDF right at the front of each nacelle the Canberra will have a span of 28.4" (720 mm)
On this plan the RH nacelle with the EDF is in a 'direct' plan view where as of course in the plane the whole thing is canted nose up.
Click image for larger version

Name:	B2plan.jpg
Views:	3
Size:	241.9 KB
ID:	178490
The issue is going to be that long exhaust tube. To match the area of the 'annulus' around the motor it will be just 22 mm diameter, hence the need to build just one nacelle first to check the thrust actually available.

At 28" span it will have a wing area of just over 1 sq ft so if I can keep the all up weight to 4oz it stands a change of flying reasonably well on 3oz static thrust but it will be one heck of a light weight build.
HK suggest the 30 mm EDF can give 1.69 oz on a 2s so a lot is going to depend on the efficiency of that long exhaust tube.


quorneng is offline  
  Reply With Quote
Reply

  WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > Scratch and Kit Built Aircraft

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
$100 EDF Semi Scratch Anything Goes! Contest xmech2k Scratch and Kit Built Aircraft 34 11-23-2014 07:00 AM
$100 EDF Scratch Build Contest Flying Wing CHELLIE Scratch and Kit Built Aircraft 72 11-21-2014 11:52 PM
$100 Semi Scratch, Twin Build Contest CHELLIE Scratch and Kit Built Aircraft 64 08-23-2014 01:04 PM
$50.00 Scratch Build Contest, It has Begun :) CHELLIE Scratch and Kit Built Aircraft 120 12-07-2013 04:27 PM
$100 Scratch Build Contest "Best Looking" poll here hillbillynamedpossum Scratch and Kit Built Aircraft 107 08-27-2013 12:23 AM


All times are GMT +1. The time now is 12:14 AM.


Powered by: vBulletin
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

Charities we support Select: Yorkie Rescue  ::  Crohn's & Colitis Foundation



Page generated in 1.31805 seconds with 65 queries