RCU Forums - DUCTED FANS

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Does anyone have any experience with the really small fan units? Hobbyking has some very small fan units such as several around 2 inches. Am planing a small, indoor XB-70, with a single fan. Sure doesn't seem like something that small would put out much thrust. I guess if I keep it 3 or 4 ounces it might work. Any suggestions?

I had a 30mm fan unit on a one of Space Shutt le. The fan exploded! With the correct set up they produce thrust, but stay out of the path of the fan blades.

head over to the other forum site, they have a section for fans 40mm and below and I frequent that part of the forum :)

The problem with small fans is they are extremely dependent on high rpm to make good performance. The glow motors make enough power but not at an rpm fast enough to be of use in a tiny fan. The new micro fans turn 60Krpm, the best glow motors are half that.

I wonder what the smallest size glow engine is that can acheive great performance and with a halfway scale looking plane..?

By great performance, let's call it at least 1:1 thrust to weight.

Found that F-16 with TD .020 and home made fan:
In 1986 or 1987 this was the World's smallest RC Ducted Fan F-16. It has a Cox TD .020 and a home made 2 inch fan unit. Turns 30000 RPM!

Ailerons and full flying Stabs, too!
http://terry_holston.tripod.com/id11.html
Remember seing another Mig-15 with TD .020 in MAN in the early 90's, also with home made fan.

Many years ago, I tried to make a ducted fan with a TD.09 and a computer fan (about 80 mm diameter), and a duct made from fibreglass over a lost-foam core. When I finally got it running inside the duct, the airflow was hardly enough to blow out a candle. I turned my back on ducted fans after that. Still have the TD.

Computer fans have low pitch and a very large hub, so small actual working blades to allow high air flow. The Axiflow for 1/2A(.049/.051)gave reasonable airflow but the Cox engine couldn't produce enough rpm for real high performance compared to what electric can achieve now with 40000+ rpm. DF is still possible for very light free flight models as was done in the 50's in the UK.

Quote:

ORIGINAL: combatpigg

I wonder what the smallest size glow engine is that can acheive great performance and with a halfway scale looking plane..?

By great performance, let's call it at least 1:1 thrust to weight.

That would probably end up being more a matter of how light you can build than how much power you can put into a 3" fan. A Cyclon or similar would be a good start I reckon....

Quote:

ORIGINAL: DeviousDave

Quote:

That would probably end up being more a matter of how light you can build than how much power you can put into a 3'' fan. A Cyclon or similar would be a good start I reckon....

Quote:

ORIGINAL: DeviousDave

Quote:

That would probably end up being more a matter of how light you can build than how much power you can put into a 3'' fan. A Cyclon or similar would be a good start I reckon....

I conjure up an imagine of a model that has 200 hours in it with a $240 Cyclon and who knows how much more money for the rest of the innards... that ends up with a top speed of 80 mph....:D

A blast from the past(1/2A ducted fan project):
http://www.rcgroups.com/forums/showp...68&postcount=1

Jetpack gave me plans for the Berkeley tiger I have them somewhere.<div>Also there was a kit for it on eBay a wile back including impeller and it went to over $100!</div>