what_the?!,

I don't claim to be a expert in ducted fans. What I do know is that raeding this thread is making you sound like the arrogant , smart mouth and all of the other "nice" things that you have called everyone that has a different opinion than you. Everyone that you have blasted for disagreeing with you has givin so many people so much help in this forum encluding myself. Never have I seen any name calling ie."tool" out of any of them.

mr_matt, Terry Holston, grbaker, patf all go the extra mile to help newbys SAVE TIME AND MONEY by letting people know what has worked and has not worked for them during their many years of flying. I don't believe that you are the first to ask to question, "Are ducted fans producing the most thrust they possibly can"? I think the simple answer to that is yes. You arent going to fit a 7" fan in many jets and people realized that, so they developed the turbine. Good luck in your trials, when your done I'm sure matt will sell you a Jetcat!

By the way everyone that you have spoken to uses there real name here, no ones trying to hide.

kfalcon..absolute rubbish..

evryone who has contributed constructively has received either more questions, or a clarification request, or similar.

i never referred to anyone disrespectfully until a certian person started doing so...

as far as this topic goes, am i the only one who wants to question to the void?...is everyone only too happy to accept and conform?

the evidence is that there are gains to be made..so the simple answer is not "yes"...

and i have no idea what you're referring to about real names...i was referring to the dissing of something known as glascat...

arrogance is where someone blatantly argues without basis and dismisses all and sundry. i am definitely not doing that...i am happy to have intelligent, informed conversation that is contributory...but am not happy to have guesstimates, assumptions, general rules etc rammed down my throat...however frsutrating this may be to some of the readers.

i appreciate the fact that certain people try to do things, but the list you have, some of them get defensive and abusive and rude if you dare to question... if a post is completely sound, then i should be able to question to the void and get answers back to first principles..this is a way of checking validity..that's merely all im doing...and it seems to really annoy some doesnt it?...particularly those who cant answer to the void...

again, this technique is nothing new...

oh ,a nd for the record...i'm not after opinion...opinion is over-rated.

just the facts please....that's all i ask.

what-the,

Jeeeeeez!!! You are arguing with some of the MOST experienced D/F guys on the planet!!!

Thrust is a combination of volume and velocity. The larger fans trade velocity for volume. This is why you see larger thrust values for the larger fan units. Yes, a Byron fan produces more thrust (static) than a BVM Viojet but not nearly the velocity that the BVM fan unit produces. The Byro-Fan is moving more air (volume) but at a slower rate. (velocity) The BVM fan trades volume for velocity.

To get speed you MUST increase velocity while maintaining adequate volume. You keep quoting thrust figures---I can tell you that in the real world it doesn't work this way!!!

Go ahead and buy your Rossi 105. After you've beat your head on the concrete for several hours trying to get it to run, re-post here with your bruised head (along with the bruised ego) and tell us what you have found. You are trying to re-invent the wheel where several guys here have already "Been There and Done That"..... Also, go ahead and try to buy a hurricane fan. The last I heard they were no longer available. If these fan units were any good dont'cha think they would still be around.

Signed...Been There and Done That----Kevin

ROTFLMAO!!! [sm=lol.gif]

Most people ask questions on forums to get different opinions from different people.
An opinion is what someone preceives to be a fact. To draw your own opinions, spend more time in the garage with your planes and less asking for "opinions" on forums.

man this is sooo boring now..do i have to go through semantics with you guys..?

firstly, volume already has the velocity component in it..otherwise it'd be area..

scondly, opinion is just that, opinion.. fact is fact...

perception has nothing to do with it...

if i told you 1 + 1 was 3..as i perceived it to be...what good would that do you?...answer...nothing...and that is an opinion..

however, if i told you 1 + 1 was 2, because i know that it is, not because i feel that it is, then that would be fact....

anyway, it seems that alot of ppl rely on not knowing quite everything that is needed to know, and are secure in knowing what is only what they perceive as "necessary"... and those who want to know more are immediately set upon by the mob....

ive had it with this thread...i know have an excellent gauge of what to expect..if i want real info, i have to look elsewhere...

it's funny though, even when the proof to the se high fallutin "theory" as you so like to bag, is right there...as for the case of the guy who had the 7 inch fan and os combo at 20 lb...you guys still wanta rag on me...

theory suggests that a 6 inch fan would be somewhere between the 5 and 7 right?....and i suppose the bench tests will tell me that the theory is not correct...?... bah!...you're kidding me right?

ill go for theory AND test anyday.. you guys go for test alone, dont bother about the theory...


it's analogous to a wrist watch... you guys just want to know that it keeps time, and what time it is... i want to know why it keeps time, and how....

remember it was heresy to suggest the world was round?....well this is like that... the mob wants to burn me at the stake...

ill get back to ya when i prove that it's round....

What I find a little weird is that you disregard everything anyone says that is not in line with what you want to hear, but when one guy makes the above I think, I believe statement

RIGHT WHERE?

I thought we were talking about ducted fans with near turbine performance. But I guess we were mislead.

BTW - There was a guy here in the States (Josh Harel) that developed a 7.5" Prop-fan that put out between 12.5# (3 blade) and 16.5# (4 blade). Top speeds were around 90 - 100 mph.

In summary then, larger fans (with lower pitched blades to maintain the same
power input requirement) will produce more thrust. Seems reasonable since that's the way normal propeller driven aeroplanes seem to work.

It also seems that the fans you can actually buy are not optimised for low speed thrust. Not surprising, really, since that's not really what most people want out of a jet. It's like looking for the best race car to buy for pulling stumps.

BINGO...after all, the DF is really only a prop with a shroud... AND this is the entire basis for my argument. If you have a more powerful engine for your conventional prop, do you expect mor thrust?...or do you just accept what you are told and that there doesnt exist a bigger prop so dont dare even explore the concept?...

There appears to be another conclusion..that the DF fans on the market are optimised for best mix of speed and acceleration... and that may mean at the expense of static and/or dynamic thrust...that's fine. If you have plenty of power, you can get more than 13 lb thrust from a 5.25 inch, and 6 inch fan also, provided you match the fan to your engine's characteristics. But to be told and abused for asking is not fine. Especially since it appears that what the "theory" suggests, is infact, correct. (well countsarnit!, who'd 'v thought?)

and yes, grbaker..you must have been reading another thread... it was mentioned that a bottom of the line turbine generates 18 lb thrust...., and that you should be able to get up to 25 lb with perfect fan, no losses, no turbine...and it was also clearly stated that top speeds were not required...

regarding what i want to hear.., well no again...(you're not doing too well are you?)...i cant dismiss what people have seen can i?... and i never did, did i??... what i did do was ask about how the result was achieved.

after explaining myself about how i thought aht more power/ proper fan aselection should give more than 13 lb, i already figured why- i just needed to hear that someone else had figured the same thing... so there's no need to question that one is there?

sigh...

Who the hell flies Ducted fans anymore anyway??

Who cares what horsepower the fan and motor combination yeilds?


Do you want to fly airplanes or fly your bench? If you are trying to move your bench get a bigger fan and bigger motor, if you want to fly a fast airplane get a BVM .91 and Viofan and go fly a jet. Of ocurse if you are really a bottom feeding troll you just want to argue anyway.

Mr. what_the?!,

Make sure when you reply you call DavidR something besides a TOOL... that one has been used!