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-   -   1/2A ducted fan??? (https://www.rcuniverse.com/forum/1-2-1-8-airplanes-70/7314220-1-2a-ducted-fan.html)

air-madness 03-31-2008 10:09 PM

1/2A ducted fan???
 
Hey all. I was wondering if anyboby had, or knew/knows, what little electric ducted fan kits, non brushless (for rpm reasons), (cheap-o) easily found at Tower that would work for an .049 Sure Start?

I don't want to buy one and find it not able to work; want to convert one.

I am the one who converted my Sure Start to have the AP carb.

Wouldn't a little tiny jet be loads of fun?!!

DeviousDave 03-31-2008 10:28 PM

RE: 1/2A ducted fan???
 
Ducted Fans need a lot of RPM.. Surestarts don't enjoy a suplus of Testicular Fortitude, so they make a poor choice for powering a Ducted Fan setup. I did some playing with EDF's a while back and found that at least from a load perspective the standard Speed 400 3" fan is about the same as a 4.7-4.7 prop. At that load and cell count the fan would be turning about 19,000 on a Astro 020, which is way out of the ballpark for a SureStart. Some of the newer GWS fans may have less load, it might be worth checking it out. The big problem you'll find is how to mount the engine and not take out so much of the fan center that you lose support for the engines and ruin stator rigidity. I'm dealing with this right now trying to get a TD .010 into a little GWS fan.

KidEpoxy 03-31-2008 10:50 PM

RE: 1/2A ducted fan???
 
Wasnt there a kit (I'm thinking Clancy but may be wrong) that had a cut down prop inside the fuselage in something like a F86 Sabre thing? It was almost kinda a little like a ducted fan... maybe for a .10?

combatpigg 04-01-2008 12:22 AM

RE: 1/2A ducted fan???
 
Kamdax sold the Norvel powered F-86. It tilted the entire tail assembly for pitch control, instead of a convoluted linkage to operate the horizontal stab. I took a whack at flying BipeFlyers' F-86 and never did earn my jet pilot rating. It was like trying to balance a balloon on a stick without having any prop blast on the control surfaces to help with takeoff.
Japanman built a much more successful 1/2A F-86 with his own fan unit and a VA engine.
The 1/2A Fantrainer would be a great old "DF" project to re-visit someday with Cyclon power. Not real fast but a real crowd pleaser.
If you have enough SureStarts to mix and match parts with and can perform the basic hop up tricks, you can almost get KillerBee level performance out of one. I suppose then you could experiment with DF set ups on a glider-ish type model to get the feel of it. I think if you could get 12 ozs worth of thrust it would be feasable to build a little jet with enough power to at least fly.

BMatthews 04-01-2008 03:26 AM

RE: 1/2A ducted fan???
 
Back in the day when RK or Kress or whoever it was made DF units for 049's they were intended solely for use with TeeDee's since they were the only engine at the time that made enough RPM to make the fan useable. Something to consider.

airraptor 04-01-2008 04:02 AM

RE: 1/2A ducted fan???
 
get two apc 5x5 props to make a 4 blade one. you can even notch the hubs (take away about 25% of the hub thickness) if needed. now cut them down to 3.75" or so. they will have the high pitch and the r's. make your own duct by finding the right size plastic coke (soda) bottle or other food container. make a very light, small jett with big wing like a U-2 type plane. then as if flies keep cutting the wing tips till you find best speed and best hadling.

could look at long thin wings from the 6volt speed 400 pylong models.

old git 04-01-2008 04:08 AM

RE: 1/2A ducted fan???
 


ORIGINAL: BMatthews

Back in the day when RK or Kress or whoever it was made DF units for 049's they were intended solely for use with TeeDee's since they were the only engine at the time that made enough RPM to make the fan useable. Something to consider.
I believe that Kress are still in business. A couple of years back I bought a twin installation from them "because it existed". I was wondering about using a TD with it.

Alas, as with so many of my good ideas it remains an idea. I can't even remember where I stored the unit. Nice little toothed belts and wheels, must be useful for something!




old git - - - - aka John L.

minan59 04-01-2008 07:16 AM

RE: 1/2A ducted fan???
 
1 Attachment(s)
Clancy avation had a kit called the Turbo Bee. I have made 2 of them,several years apart. Unfortunately the first one died while I was experimenting with different propellers. They both had a Norvel .074 installed in them. This one pictured fly extremely well last year.

KidEpoxy 04-01-2008 11:45 AM

RE: 1/2A ducted fan???
 
I mentioned this not long ago, but seems relavent here,
Would a large spinner help unload a fan/cut-prop/4blade that would otherwise bog the surestart?
Like a 2" spinner in a 4" duct?

I have visons of the center pod with spinner in front and cone in rear with a taper duct exit to match (keep airflow sectional area). Maybe even some balsa cheeks & chin next to the engine.

skaliwag 04-01-2008 12:05 PM

RE: 1/2A ducted fan???
 
This may help with your cone.
Sulivan Bullet Tank
SUL376. 1.5 Ounces / 44 cc.
1-3/16" diameter x 4-1/4"/ long 30 mm dia x 108 mm long

gcb 04-01-2008 01:35 PM

RE: 1/2A ducted fan???
 
Don't think I would use a ducted fan intended for electric for glow power any more than using an electric prop on a glow engine. Different kind of stresses imposed.

The original owner of Kress Jets passed away. Don't know if the next owners are still in business. Haven't seen any advertisements.

George

bolar 04-01-2008 01:50 PM

RE: 1/2A ducted fan???
 


ORIGINAL: minan59

Clancy avation had a kit called the Turbo Bee. I have made 2 of them,several years apart. Unfortunately the first one died while I was experimenting with different propellers. They both had a Norvel .074 installed in them. This one pictured fly extremely well last year.
Which prop did you settle on?

minan59 04-01-2008 05:06 PM

RE: 1/2A ducted fan???
 
I am using a cut down Top Flite 9-7 prop. It looks a little wierd in the fuselage being so wide, but it has a decent airfoil close to the hub

air-madness 04-01-2008 06:09 PM

RE: 1/2A ducted fan???
 
I have an original mail-out production guide/price list with pictures and prices of the little DF units from Kress. The little booklet is all black-and-white and has units for .049s to .18s in it. Pretty pricy for what they consist of though. I will look at other various units.

DeviousDave 04-01-2008 07:58 PM

RE: 1/2A ducted fan???
 


ORIGINAL: BMatthews

Back in the day when RK or Kress or whoever it was made DF units for 049's they were intended solely for use with TeeDee's since they were the only engine at the time that made enough RPM to make the fan useable. Something to consider.

What he said...

airraptor 04-01-2008 08:58 PM

RE: 1/2A ducted fan???
 
i dont think you will get much thrust out of that prop since the airfoil is so think it will just slow the motor down. did you try the little props like i sugested. you could even use a apc electric 7x4 too just cut to size.

those APC 5x5 i spin close to 30,000 with them so cutting the tips or in half will be ok

ClemenTang 04-03-2008 09:48 AM

RE: 1/2A ducted fan???
 
1 Attachment(s)
I have the RK-709 smallest in the family specified for the TD09 @18000rpm weak I mean weak manual says trim down the blades or get the Cox .15 Conquest I think why not use a buggy engine put an OS .15 RX wow 30000+ ground rpm! If you're thinking 049 the one fan unit is for Midwest A-4 first generatioin foam jet balsa wing from the 70's don't think those who still own one willing to sell e-fans are designed for high rpm with low pitch won't get far on a 049.

KidEpoxy 04-03-2008 11:21 AM

RE: 1/2A ducted fan???
 
So if we know the 120mm duct (5") Clancy Tubo Bee worked with a 074 & fatblade 7pitch,
and the EDFs are 40/50/64/75mm with lower pitch & rpm out of our range,
how far down can we go from the Clancy toward the 55mm EDF.
Especially for a SureStart.... didnt I see they were only ballpark 30-40watts somewhere?

Looking at it from a wattage side,
a 40w electric motor would only try to spin ~50mm EDF
(gws brushless 55EDF ~ 40w @ ~20krpm)

The nice thing about trying to make a 4blade from cut 8x4 - 9x5 is the large hub would still have a lot of meat left after the notch thins it by half. I wouldnt trust a half thick 8x4 on a .15, but how hard can a SureStart torque spike all that hub meat still left on the prop.
3x5 FourBlade in 75mm duct, 1.5Spinner, with cheeks & tail for the engine - worth a shot

airraptor 04-03-2008 06:20 PM

RE: 1/2A ducted fan???
 
i still say the smaller apc props cut down is WAY better than large plane props cut down. to thick hubs, to thick airfoils, to slow rpm, and not enough thrust to fly itself. take one of those props cut it down put on engine stand then run it how much air is it moving? about 4-5 ounces worth.

apc makes a 5.25x6.25 that when cut down and using two of them will less hub thickness than you larger props and give 3 times the thrust.

combatpigg 04-03-2008 10:23 PM

RE: 1/2A ducted fan???
 
I agree, it is real easy to overload a .049. To make this idea work, a guy will have to get smarter than Mr. Kress and all the others who have already tried. I don't know anything about EDFs, but think you would need to get some for guinea pigs and start doing some carving.
If there are sentimental reasons for trying this with Cox power, fine...but the chances for success would be [obviously] better if using a Cyclon or lower timed GZ .061.

DeviousDave 04-03-2008 10:39 PM

RE: 1/2A ducted fan???
 
I keep hoping that GKamyzs will get his half-a fan design done and cut. He's really into the math/Formulae end of ducted fans and for a while was talking about something like this. The main problem with fans to date is that the diameter is too large for the application. 3" seems to be a default because the airframes were large due to weight and the thrust was needed to get them going-The Midwest A-4 is supposed to be a pooch from what I hear. These guys need smaller diameter and higher pitch.. GKamyzs had an impellor for something this size rapid prototyped at one time for an electric, now he has the CNC machines to make molds. Hint-Hint.

Well, maybe after the baby comes. Mrs. GKamyzs are expecting their first any day now! WHOOT!!

Japanman 04-04-2008 07:59 AM

RE: 1/2A ducted fan???
 
I think you could make a plane that flys o.k with a sure start. You would need it to be light- I think you want to be about 12oz to work.
In my experiments I found that high rpms are not necessary, and about 4.5 inches of pitch with about 50% blade area in the duct works well.
I think something you need to think about is time here- it is all and order of complexity more than a simple prop- so you want to be prepared for that.
My best bet for success would be getting the edf unit sold by kyosho about 5 years ago and using it. The impeller will work but needs to be very carfully looked after as it is made of very brittle stuff- but it will hold together unless you throw rocks at it.
Build a very very light plane and tell us how you go!

J.M

KidEpoxy 04-04-2008 12:34 PM

RE: 1/2A ducted fan???
 

In my experiments I found that high rpms are not necessary, and about 4.5 inches of pitch with about 50% blade area in the duct works well.
Uh... 50% what now?
Is that saying half of the, lets just say 3" for now, half of the 3" round area should be blade sweep, which is just determining the hub/pod/spinner size,

or half of the sweep area should be blade... kinda like 1/2 the prop disk should be prop.

Japanman 04-06-2008 04:53 PM

RE: 1/2A ducted fan???
 

Uh... 50% what now?
Is that saying half of the, lets just say 3" for now, half of the 3" round area should be blade sweep, which is just determining the hub/pod/spinner size,

or half of the sweep area should be blade... kinda like 1/2 the prop disk should be prop.
Imagine the fan is a disc of paper with no blades cut out to start with. The disc would be divided into 8 and then half of the pieces are cut out to leave four blades with 1/2 the blade area.
The hub area is relatively small even at 40mm, which is a good size to hide most of an engine in.

I didn`t mention diameters, I have used 75mm (3" ) and it seems just right. I think you could go smaller to say 2.5" or 2.2" if you made a drive shaft to get the engine back from the fan and motor fairing ala C/L speed plane, AND used an engine happy to run 35K like the GZ/ Cyclon / Fora

But then as fun as it would be, you would want to be pretty motivated when 3" works pretty well.

J.M


cyclops2 04-06-2008 09:58 PM

RE: 1/2A ducted fan???
 


About using a small GWS 40 mm EDF . I am using 2 of them powered buy 2...brushless motors.
Each motor pulls 7 amps @ 12 volts or 84 watts. Gives 6 ounces of thrust. 2 of them in a small 1lb. A-10 do a nice scale flight. The rpm is so high I can hear less noise near the peak.

A 2 bladed prop in the same plane, I have one made, wants to jump vertically out of my hand.

My read is, ducted fans are for outragiously powerfull setups. Less blades has always given more thrust & speed for a given power..

The airflow into the carb is dicey.


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