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Jul 08, 2019, 07:07 AM
Watch out for that planet....
Shane McMillan's Avatar
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Build Log

Resurrecting the dead


Lately I have been having a lot of fun flying electric ducted fan, with my RBC Mig 15, which I have been flying a lot lately and really enjoying. It even doesn't seem so fast any more!

I decided to resurrect my old RC Lander ARF foam Grumman Cougar, to compliment the Mig (well, maybe!). The model was overweight with all those fancy metal retracts and heavy and inefficient Lander fan. Model only had 3 or 4 flights before I gave up on it.

Ripped out the retracts and their mounts along with the nose gear steering servo. The model will be bungee launched. Keeping the rudder servo though as a working rudder will be nice. Also unceremoniously ripped out the Lander fan unit. This will be replaced with a mongrel fan made using the shroud from a Chinese Wemotec knockoff 70 mm fan, but using a genuine Wemotec Mini Fan 480 rotor which I have lying around at present. Also lying around unused is a HET 2W 20 motor which go into the mix.

Reworked the ducting using added in foam to smooth things out airflow wise and have glued the wing onto the fuselage instead of having it held on with bolts which never really held thing rigid and were heavy too. Some photos below of my progress along with the before shots from when the model was new.

I'll keep adding to this blog until the model is finished and flying.

Cheers,
Shane.
Last edited by Shane McMillan; Jul 08, 2019 at 07:52 AM.
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Jul 08, 2019, 09:10 AM
Big gov never Works
St. Martin's Avatar
HiYa' Shane!

Are you keeping the cheater? The scale intakes are too small for 68mm, even the Wemo, unless you going for a high efflux dynamic thrust situation. The WeMo rotor will still work fine, down to 75% FSA, but static thrust is lost. This is a dirty air frame. So, a pure dynamic flow system is not really the most efficient. To gain back some of the static, then watts will need to be 1000+W. That means weight. Brent Hect (corsair nut) did this mod, complete ducting. I use the cheater, without the hole punched cover. Reshaped the cheater. But...if you want to get rid of the cheater, the scale intakes will work much better, if you go with the 65mm505. Same 2W20, less static than the 68 w/cheater, but what an increase in efflux flow speed. I have several 505 rotors 5b. And if you send me your knock off shroud, motor, I'll make you a 65-505 with FUZZ shroud, like I did Vicky.

One rule taught to me by Stu Maxwell.. "the exhaust area of any fan system, can not be greater than that of the intake area. The exhaust should be equal, or smaller than the intake area". You would need to calculate the intake area to find the exhaust. As the 65-505 rotor will operate efficiently at 52mm(80% FSA) the intakes are most likely more than 80%. I also have a balsa intake lip to fit the 65. It's in the pics on Vicky's fan, in the Hunter thread. Worked very well in my Cougar, but with the cheater and 53mm exhaust. If not, keep the cheater for the mongrel unit you now have. The cheater actually makes the pro rotor sound quite nice, if it's clocked real smooth.

Fuzz
Jul 08, 2019, 04:51 PM
Watch out for that planet....
Shane McMillan's Avatar
Thread OP
Hey fuzz,

Sounds like a good offer. I haven't as yet got another shroud so I only have at this stage a Rotor, motor and adapter. I can send you all that, is that all you need? Do I have to buy a 505 fan too to get the mount and stator assembly? I was planning to keep the cheater, as you say this is a dirty airframe.
Interestingly Lander had done away with the cheater. Mine has no perforations in the cover. It did fly OK without it on the Lander fan. I removed it after seeing how you did yours. Thats why the foam looks fresh there.

PM me your details and I'll get some stuff in the mail after we have worked out exactly what you need.

Cheers,
Shane.
Jul 08, 2019, 05:50 PM
Big gov never Works
St. Martin's Avatar
Hi Shane, If your keeping the cheater, then you should use the 68 WeMo rotor as is. I suggest the 65mm version if you planned on covering the cheater. I flew mine with the 65mm pro and EVO rotors. But was a waste with the cheater, that did not allow the smaller fan to run with high influx and efflux flow. With the cheater, go with the full size 68, and get the benefit of the higher static thrust. You can still run the 68 at 56mm exhaust(85%) for good top end. But..wait...

I just checked my rotor boxes, and I have a 68Evo rotor, but with the nylon spinner. Do you have the alum spinner with your WeMo rotor(68)? Here's what I can do. Send me the motor, ESC with motor/ESC wires made to length. Chinese shroud, rotor, adapter and spinner. I'll give you the spare evo rotor. There is one concern with the 2W20 and the Evo. The 2W20 was designed to run with the 5b pro rotor on 4s for [email protected] With the Evo rotor, this jumps to [email protected] Het designed the 2W23 to replace the 2W20 with the Evo. The 2W23 gives the same numbers as the 5b, with the Evo. [email protected]


So..using the 2W20 and Evo will require a 60A ESC and limited full thrtl. Or, get a 2W23. The Evo will sound nice. Either way, it will be a good fan. I will need the chinese shroud, for the stators. Or I can hack out the stators of an old CS that is (4) stators, I have on hand.

I can size the ply shroud to accept the minifan intake lip, which I have lots of. I had to size Vicky's shroud to have the ID of a 505, but the OD equal to the Wattage shroud, so the provided parts in the Hunter kit would fit. This took (3) lams of ply, normally I used two.

Either way, 2W20/Pro rotor, or 2W23/Evo rotor, I can build a nice fan. If you donot want to get the 2W23, the pro rotor will work fine.

Fuzz
Jul 08, 2019, 06:00 PM
Big gov never Works
St. Martin's Avatar
BTW, I'm using the 2W23 in the SM69 on 4s. Just a little higher load than the Evo. [email protected] 700W.
Jul 08, 2019, 06:37 PM
Watch out for that planet....
Shane McMillan's Avatar
Thread OP
Quote:
Originally Posted by St. Martin
Hi Shane, If your keeping the cheater, then you should use the 68 WeMo rotor as is. I suggest the 65mm version if you planned on covering the cheater. I flew mine with the 65mm pro and EVO rotors. But was a waste with the cheater, that did not allow the smaller fan to run with high influx and efflux flow. With the cheater, go with the full size 68, and get the benefit of the higher static thrust. You can still run the 68 at 56mm exhaust(85%) for good top end. But..wait...

I just checked my rotor boxes, and I have a 68Evo rotor, but with the nylon spinner. Do you have the alum spinner with your WeMo rotor(68)? Here's what I can do. Send me the motor, ESC with motor/ESC wires made to length. Chinese shroud, rotor, adapter and spinner. I'll give you the spare evo rotor. There is one concern with the 2W20 and the Evo. The 2W20 was designed to run with the 5b pro rotor on 4s for [email protected] With the Evo rotor, this jumps to [email protected] Het designed the 2W23 to replace the 2W20 with the Evo. The 2W23 gives the same numbers as the 5b, with the Evo. [email protected]


So..using the 2W20 and Evo will require a 60A ESC and limited full thrtl. Or, get a 2W23. The Evo will sound nice. Either way, it will be a good fan. I will need the chinese shroud, for the stators. Or I can hack out the stators of an old CS that is (4) stators, I have on hand.

I can size the ply shroud to accept the minifan intake lip, which I have lots of. I had to size Vicky's shroud to have the ID of a 505, but the OD equal to the Wattage shroud, so the provided parts in the Hunter kit would fit. This took (3) lams of ply, normally I used two.

Either way, 2W20/Pro rotor, or 2W23/Evo rotor, I can build a nice fan. If you donot want to get the 2W23, the pro rotor will work fine.

Fuzz
Fuzz, the 68 rotor I have is from the older (original) Minifan 480. It is not a pro rotor so has not been dynamically balanced and has the nylon spinner. The Aluminium spinner is available as a spare part from Wemotec and also from RBC. What do you think, worth playing with at all? I could just buy another evo from Mark. Probably going to do that anyway and will get a A 2w 23 or 25 for that to run on 6S, but was planning that for another model.

To my way of thinking, the cougar is not a high speed airframe so therefore higher static thrust is probably more desirable than high dynamic thrust, high eflux velocity.

Fuzz, you've been flying it what are your thoughts. At present I don't have a fan so can jump either way, 68mm or 65mm. I also can buy a complete 65 mm Wemo 505 fan from New Zealand where seemingly there is some stock of the old Wemo units. They have the 68 mm Pro's in stock too.
http://www.wattsup.co.nz/catalog/index.php?cPath=25

i guess I'm a bit confused on which way to jump right now...

Cheers,
Shane.
Last edited by Shane McMillan; Jul 08, 2019 at 06:42 PM.
Jul 09, 2019, 02:36 AM
Big gov never Works
St. Martin's Avatar
Hi Shane, It's good to know there are some 505's still out there. To bad they are not 505 Evo's. But those old 505's are great for really restricted slick frame's. You may have one of the early non-glass filled rotors. If so, they are a jewel, if running under 500W. I still have one of these left, and they are great with a HET or Mega 3W or /3 on 4s. The blades are thinner and load higher than the glass filled. You can tell, if they are real shiny.

I have balanced pro rotors, but I have no alum spinners left. The plastic spinners are good to 500W safely. If you can get an alum spinner, I'll donate the balanced pro rotor. Then you have a good use for the older 2W20 for this rotor. You will need a 50A ESC minimum.

Here's what I need: the 2W20, ESC w/motor wires the length to reach the battery location. The chinese knock-off shroud, alum spinner, and send your old minifan rotor. You pay for the return shipping via Pay Pal. My only investment is my labor, which I gladly give.(and the pro rotor which you are exchanging).

Will probably be cheaper than buying the mini pro from watts-up. plus, you have a shroud that is perfectly round and ridged if I make it. Later, you could use it with a 1500W system, with no worries. I will also make up the mylar exhaust @ 56mm and rout the motor wires through the shroud. Be sure to make the motor wires a little long with 3.5 connectors. You can always shorten them. I need about 4" of loop motor wires behind the motor, then still reach the batt area.

I'll get to your email when I return home later today.

Fuzz
Jul 09, 2019, 04:44 PM
Watch out for that planet....
Shane McMillan's Avatar
Thread OP
Hey Fuzz,

Sounds great! I spoke to Mark at Extreme Hobbies yesterday. He has spare pro rotors with the aluminium Spinner which I can get for 10 bux each. Says he has lots of them. I also asked if he had a spare Minifan shroud but he wasn't confident about that. Said he would look though.

When I get all the bits together I'll ship it off to you. Might be a week or so though as I only just ordered the Chinese fan yesterday from HobbyKing. This is
the one:
https://hobbyking.com/en_us/10-blade...-fan-unit.html

I chose that one as it looks like it's very similar to the Wemotec hub and stator design. Probably a rip off!
I will use the 2W20 motor as I already have it. Oh and my spare rotor is the glass filled one, but with the plastic spinner.

Still filling and sanding on the Cougar.

Cheers,
Shane.
Jul 10, 2019, 11:39 AM
Big gov never Works
St. Martin's Avatar
What ever you send me, I'll build you a good fan Shane. I really should recondition my Cougar, also. It looks pretty worn. I really can not fly it for now, or any of my bungee jets. Just not good at our field anymore. Thats why I want to build a light stick jet of good size, but very light. With a light system. So, I'm going to put that 68Evo rotor with the plastic spinner to use. Have you gotten my emails? I'm going to do a light Evo system. Either 5s-1500 or 6s-2000 with a Het 5W. If the 5s flys it, I'll stick with it. But, it may need the 6s to hand launch.

Fuzz
Jul 10, 2019, 09:53 PM
Watch out for that planet....
Shane McMillan's Avatar
Thread OP
Hi Fuzz,

Haven't received any emails from you. Perhaps something went wrong...I just sent you another test email from my address.

No Minifan shrouds available from Mark at Extreme so will be waiting for the Chinese option to arrive.

I will be watching your Skyhawk project with interest.

Shane
Jul 13, 2019, 05:39 PM
Watch out for that planet....
Shane McMillan's Avatar
Thread OP
Have been a bit preoccupied with other stuff the past few days so not much progress. I did however manage to get the wheel wells covered over and some preliminary filling and sanding done on the airframe. It needs a few more rounds of fill-on sand -off.

At this point the major airframe mods are done now its on to the finishing stage. This won't be any concours winner, It's going to be an everyday hack model!

Now, few questions for you Fuzz cos I know you'll be looking in here.

Where have you got yours balanced? Manual I have says 80mm behind the front intake lip. That seems a long way forward. Given that I plan to place the bungee hook at 50% from nose to CG then that becomes dependent on ultimate CG position.

Bungee hook will be a plywood hook plate RBC style glued into the nose block.

Shane.
Jul 13, 2019, 06:47 PM
Big gov never Works
St. Martin's Avatar
Hi Shane, I use a #2 washer, soldered into the slot of a #2 SM screw. I inserted a piece of inner Nyrod(yellow) to receive the screw. I have this located 73mm behind the wing bolt. Very easy to get the CG by hanging up-side down. I do this in most of my jets. After confirmation of the batt placement in flight, the screw/washer can be removed. My bungee hook is just a 1/8CF dowel that goes up to the battery tray for additional support. I have this located 138mm in front of the wing bolt. Excellent release everytime. RBC style hook works great too. I covered my wheel wells with packing tape. It looks it... Really need to re-condition this thing. It deserves it. Look at that pretty, secret, 11b fan! It's a work of art. Looks like it needs some fod cleaning..

Fuzz
Jul 13, 2019, 06:52 PM
Big gov never Works
St. Martin's Avatar
Shane, got your email. No problem. I can use the plastic spinners. Thanx for trying.

Fuzz
Jul 15, 2019, 05:34 AM
Watch out for that planet....
Shane McMillan's Avatar
Thread OP
Thanks for that Fuzz.

Your CG then is pretty close to the recommended position. I'll shamelessly copy your hook location as it works!

I've been doing a web search for aluminium spinners for you and have drawn a blank. Even Wemotec don't have them listed.

Have the bottom of the model all sanded smooth (well, smooth enough!) and ready for some paint. Just have to site the bungee hook.

Cheers,
Shane.
Jul 15, 2019, 01:26 PM
Big gov never Works
St. Martin's Avatar
With that CG/hook location, I have to hold about 4mm up elevator. I'm using about 15# on the Aero-foam 3/8ID zip. Mine is sure butt-ugly compared to yours. Been flying since 2012. Needs a good reconditioning.

Fuzz


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