HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Feb 09, 2010, 11:15 PM
Registered User
Joined Feb 2006
2,405 Posts
Discussion
can someone explain to me the advantage or disadvantage

of having two fans vrs 1 fan? It just makes senise that two fans with high wattage would fly faster than one? thanks in advance
sherlockshah is offline Find More Posts by sherlockshah
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 09, 2010, 11:23 PM
Registered User
Joined Mar 2008
1,129 Posts
Quote:
Originally Posted by sherlockshah View Post
of having two fans vrs 1 fan? It just makes senise that two fans with high wattage would fly faster than one? thanks in advance
depends on the model...and if it is faster, its not going to be by much
sheppard559 is offline Find More Posts by sheppard559
Reply With Quote
Old Feb 09, 2010, 11:27 PM
Registered User
Joined Feb 2006
2,405 Posts
then why have two fans and two esc and two motors and spend

extra money? what is the point? of dual fans?
sherlockshah is offline Find More Posts by sherlockshah
Reply With Quote
Old Feb 09, 2010, 11:34 PM
Registered User
Joined Mar 2008
1,129 Posts
there is none really, but again it depends on the model and how its modeled: example f-14, airliners, a-10, etc, those to name a few would be hard to make as a single- but some jets like f-4, f-18,f-22 f-15 can be made as a single , it all depends on YOU and what you wanna spend
sheppard559 is offline Find More Posts by sheppard559
Reply With Quote
Old Feb 09, 2010, 11:35 PM
Registered User
Joined Mar 2008
1,129 Posts
if your going for all out 70mm speed , i say go with the fiberglass f-16
sheppard559 is offline Find More Posts by sheppard559
Reply With Quote
Old Feb 09, 2010, 11:41 PM
Registered User
Joined Feb 2006
2,405 Posts
that is what I am buying

F16 from proedf
sherlockshah is offline Find More Posts by sherlockshah
Reply With Quote
Old Feb 09, 2010, 11:47 PM
Team White Llama!
gundamnitpete's Avatar
Joined Jan 2008
8,144 Posts
sherlock, edf power can be complicated. If you want to understand it all you need to do more reading, less thread starting.
gundamnitpete is offline Find More Posts by gundamnitpete
Reply With Quote
Old Feb 09, 2010, 11:51 PM
Suspended Account
lavochkin's Avatar
Mokena,Illinois -United States
Joined Oct 2006
5,826 Posts
Two versus one fan. Two fan jets are always much more efficient than a single fan. Bottom line.
lavochkin is offline Find More Posts by lavochkin
Reply With Quote
Old Feb 10, 2010, 12:15 AM
Team White Llama!
gundamnitpete's Avatar
Joined Jan 2008
8,144 Posts
Quote:
Originally Posted by lavochkin View Post
Two versus one fan. Two fan jets are always much more efficient than a single fan. Bottom line.
Joe, I disagree here.

A 70mm fan at 700 watts produces about 2.5 pounds of thrust, at about 150mph efflux.

Two of these fans produce 5 pounds total, at 150mph efflux. This is a more efficient way of producing low speed thrust (to help push a draggy airframe).

One single fan at 2000 watts produces 5 pounds thrust, and 200 mph efflux. It uses 600 more watts than two fans at 700 watts and makes the same thrust, but at 200 mph efflux.

The single fan makes more efflux, but less thrust (better for dnamic thrust, or speed)

the dual fans make better thrust, but less efflux (better for vertical climbs and draggy airframes.)
gundamnitpete is offline Find More Posts by gundamnitpete
Reply With Quote
Old Feb 10, 2010, 02:22 AM
Jets fly goooood!
felix72's Avatar
Italy, Lazio, Ariccia
Joined May 2004
569 Posts
My point of view of having 2 fans instead of 1 is this.
Not considering the model in itself, I mean if its a single engine model of course cannot consider to use 2 fans in it, but if its a 2 engine then you have the chance to make it fly with only 1!
Usually 1 fan make the job easy if the fan is powerful enough, but if you have a big scale model then you can make it fly properly with 2 fans but maybe not at all with 1 fan!
Many of us on the Groups have see the big F-14 powered with 2 XPS fans, well that model is huge and it could never fly with a single fan of course!
So the point for me is, if you have a 2 engine model you want to power, go single fan unless you really can't choose differently or the performance with a single would be border line and not jet like!

Gianluca
felix72 is offline Find More Posts by felix72
Reply With Quote
Old Feb 10, 2010, 03:31 AM
My project: FAIREY DELTA 1
Erik v. Schaik's Avatar
Uden Volkel, Netherlands
Joined Dec 2003
4,976 Posts
Quote:
Originally Posted by sherlockshah View Post
of having two fans vrs 1 fan? It just makes senise that two fans with high wattage would fly faster than one? thanks in advance
As pete wrote: efficiency in thrust.
My converted 80",12lbs (13s2p a123) turbine trainer:
http://airtoimedia.nl/web/upload/Emi...28sept2008.wmv
Erik v. Schaik is offline Find More Posts by Erik v. Schaik
Reply With Quote
Old Feb 10, 2010, 08:27 AM
Effumall
kelberts's Avatar
Joined Nov 2005
3,619 Posts
Agree. But, the downsides of 2 fans:

More expense
More complicated
More things to fail
More weight
More noise
Asymmetric thrust issues in event of a "flame out"

In my case, I don't do twins anymore (except A10, Learjet, etc) if a single fan version of the airframe is available.

Although speed isn't my thing, the best way to go fast is to be light and slippery.
kelberts is offline Find More Posts by kelberts
Reply With Quote
Old Feb 10, 2010, 05:05 PM
James L
TANGOSIERRAROM's Avatar
Beck Row Mildenhall
Joined Mar 2009
813 Posts
Horses for courses I'm afraid. 1 large fan versus two smaller ones. Same thrust more or less, same sort of wattage. One set up may be lighter, one may fit the model shape better. Large fan setup may have more scope for development but an A10 with a single fan looks a bit wrong somehow don't you think?

twin fans of say 55mm versus one say 55mm running a lot more power, then the twin design is more efficient but heavier. But an F16 with a twin in it may look a bit odd.
TANGOSIERRAROM is offline Find More Posts by TANGOSIERRAROM
Reply With Quote
Old Feb 10, 2010, 07:52 PM
Watt me worry?
Madmax1965's Avatar
Florida
Joined Mar 2006
4,145 Posts
Weight(batteries)can be a problem on a twin fan......and cost. I have a twin I am changing over to single.
Madmax1965 is offline Find More Posts by Madmax1965
Reply With Quote
Old Feb 10, 2010, 08:26 PM
James L
TANGOSIERRAROM's Avatar
Beck Row Mildenhall
Joined Mar 2009
813 Posts
Madmax 1965 you got me, why is battery weight more of an issue with the twin design? Cost can definitely be a factor.
I always thought that wattage is likely to be of the same order whether you design a twin or a single. Unless you go for a single fan with a lot more power of the same size fan as the twin fan design in which case the heavier battery will be in the single fan design as you will 8 times the power to do twice the work in the same time. Twins tend to be heavier because they have two ducts, mounts, fan units, motors, ESCs and wiring although some like Pontious manage to get two running on one ESC and some small fan and motor combinations are now very light. eg twin 55mm @ 60-80 grams each versus a 70mm at 120-200 grams depending make and model.
TANGOSIERRAROM is offline Find More Posts by TANGOSIERRAROM
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion can someone explain RC to me in detail? epoweredrcgirl09 Foamies (Scratchbuilt) 6 Feb 07, 2010 12:50 PM
Wanted can someone help me, I need 2s or 2 individual sherlockshah Aircraft - Electric - Batteries & Chargers (FS/W) 2 Feb 05, 2010 12:34 PM
Question Can someone explain to me im lost fearlesshugo Electric Plane Talk 19 Dec 13, 2009 06:44 AM
Can someone explain to me Mah, cells, and voltage and what it means? JStory Electric Plane Talk 1 Jul 01, 2001 01:38 AM