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Jun 07, 2017, 08:12 PM
Watch out for that planet....
Shane McMillan's Avatar
Build Log

RBC Kits MIG 15 for EDF


With the onset of winter here, I have as has been my habit of recent years abandoned my tin shed workshop for the warmth of the great indoors. This means it's time to build a smaller model. Also I have rekindled my love of EDF, which has been dormant for a few years.

Power for this little rocket will be a Wemotec Mini Fan Evo, HET 2W22 (3100 kv) on 4s Lipo. That should wake up the reflexes!

I haven't flown much EDF over the last 10 years or so, so I will drag out a couple of oldies and get them going first whilst the MIG is being built. I have a Lander Grumman Cougar (foamy), and full composite moulded A4 Skyhawk, for Wemo Mini Fan. (Aussie produced model, no longer in production).

The Cougar is stock Lander setup, with the retracts removed for bungy launch. The Skyhawk has Wemo Mini Fan with Plettenberg HP 200-20-6 (brushed). I did consider upgrading the Skyhawk to brushless but will run the Pletty setup till either I wear it out or it won't go fast enough. Will run on 2s Lipo instead of the old 8 NiMh it used to run. Much lighter too.

I'm presently also putting together a new bungee launcher, my old one having been lent out several years ago. We all know how that ended up don't we....

Anyway, on with some build photos. Started with the right wing panel.

Cheers
Shane.
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Jun 08, 2017, 07:06 PM
Watch out for that planet....
Shane McMillan's Avatar
Moving right along I have got both wings built to the point of installing servos and then upper skins. Problem is I don't have the servos yet for the model so will have to leave the wings at this stage for a while.

Have now made a start on the fuselage. After spending an hour or so removing the fuselage parts from their sheets I have made a dry assembly of the fuse.
The MIG fuselage splits behind the wing as per full size to give access to motor and fan unit. Rob at RBC has devised an ingenious Cam Lock system for the fuselage formers to separate. This has to be assembled first, then the fuselage is pretty much self jigging.

At present I have the fuselage frame assembled dry to figure it all out. Next is to jig it up straight and true and start gluing.

Cheers,
Shane.
Jun 08, 2017, 09:25 PM
Big gov never Works
St. Martin's Avatar
Hi Shane

Good choice of power system. It gives the EVO the same watts/amps as the mini-pro with the 2W20 on 4s. I love RBC kits. And I built the YAK 23 with the same 2W22/EVO combo you are using. These RBC kits are really "old school". Most build at upwards of 40+oz, back in the day. Now it's easy to get them at 30-35oz with twice the watts-in.

Rob uses nice clean airfoils. They do not require a lot of power to really move out. Hell..they were designed to fly with 300-400W. I think you will find that you will fly very well at 30% power. With this in mind, use an ESC with plenty of margin, to avoid low power heating.

The only problem I have found with single intake/exhaust jets, is cooling. We can not use the intake as a cooling function, as with bi-furcated intakes. I like using NACA ducting to evacuate the fuselage. You may also find that you may have to use two 2s packs in series, so you can straddle the intake, and have flexability in balancing.

Good luck with the project. I was planning another RBC build soon. Most likely the Skyray.

Fuzz
Jun 08, 2017, 10:04 PM
Watch out for that planet....
Shane McMillan's Avatar
Hi Fuzz,

Good to have you along mate, you were the inspiration for me choosing an RBC kit in the first place. Read through most of your previous builds.

Re the EVO, I actually had a spare Mini Fan, New Old Stock which I bought 20 odd years ago and never used, so I bought an EVO rotor from Rob to upgrade it.

In the start of this thread I made mention of my A4 skyhawk. That is a neat little Model. It was designed by an Aussie Guy named Bill Hamilton, who is a member of our Australian F5B Team and certified speed freak. The model was at one stage produced and Marketed by Brett Solanov (Under the banner of his business name Leading Edge Technology). Brett is my long time Best buddy and I used to help out in production. My model is cobbled together from reject parts, mostly because of paint chips due to mold stickups. I had to repaint the wing and tail top sides. It's fully hollow Moulded F5B model style with hollow wing. It's been sitting around too long while I chased other interests. I've included some photos.

I flew this originally with Kyosho AP29 on 8 2200 NimH's. Now it's going to have 2S 3300 lipo at half the battery weight. Back then I had bought the Plettenberg 200-20-6 from Oliver Wenmacher. Was my first ever internet purchase actually, now it's a regular thing. I never flew it with the Plettenberg so now I will, just to justify the $200 spent all those years ago.

Shane.
Jun 08, 2017, 10:19 PM
a.k.a Maltone
Pat Lynch's Avatar
G'day Shane. I haven't been on the net for a while - in the midst of moving 2nd time in 12 months. But a new workshop is already in my head (no wonder I get headaches!) The lovely garden railway property sold before it was marketed so we managed without an estate agent! Saved $22000 - now what ca I do with the savings......
For a winter project, this will be finished before the month is out. I hope you have more Wintery projects

OK, back to packing stuff onto the trailer!

Cheers mate.
Pat
Jun 09, 2017, 05:49 AM
Registered User
dion9146's Avatar
Following with interest. I have yet to build an EDF, but each year they catch my attention more and more. I like the 'old school' nature of these kits, so you have my attention!

Dion
Jun 09, 2017, 11:16 AM
Big gov never Works
St. Martin's Avatar
Good to follow along, Shane. On the 20yr old WeMo rotor.. I purchased my first minifans, in 1997, from EJF, along with a few HP 200-20-6's. They were the only place to go to get these fans in the USA. They were originally non-glass filled. These rotors had a slightly higher load, than the later glass filled. Not sure of the exact reason, but I believe they had sharper edges and were lighter? Using a 4s-2200, Mega /3(HET 3W), they consume about 25 more watts than the glass filled version.

But...they are delicate, and have a limit as to input power, must be VERY balanced. They also sound quieter, when balanced. I used one of these in my first RBC Skyhawk. With a Kontronic 400-23, 5s-1800, she came in under 30oz. This was the quietest fan I have ever owned. You could not hear it except on the fly-by's.

So, don't overlook using these on -500W systems. They just have to be balanced and clocked well. I even use the plastic spinners in these applications. Just dont tighten the spinner screw. Just snug. The rotation of the fan will tighten it enough. I tightened one, in my early days, and it split and destroyed the fan, in-flight.

A lot of these old RBC designes, used a 54mm exhaust. You may want to check yours. The minifan pro works great @ 54mm. But I found the evo needs 56mm minimum, to have the same static/dynamic thrust ratio as the pro. Keep this in mind. It will work at 54mm, but only for high speed applications. There should be ample wood to enlarge the outlet a few mm.

The twist off tail assembly goes back decades. But, once adjusted for friction, is fool proof. I even adapted it to the enlarged BELL F-80C, I built a few yrs ago. I add 1/64th ply spacers between the two mating bulkheads. This makes it easy to cut the strip planking later. Later, I covered the tail section with plastic wrap, assembled the sections, and filled the gap with spackle. Disassemble and soak the spackle on the main fuselage with thin CA. Remove plastic wrap, reassemble and sand smooth. Instant fine line seamless mating surface. Try it.

Fuzz
Jun 09, 2017, 06:06 PM
Watch out for that planet....
Shane McMillan's Avatar
Hi guys, thanks for the input.

Pat Lynch,

G'day mate! Glad to see things are sittling down will there in Nu Zuland. I'll bet you've got your accent back already!

Another house move, you must be sick of it by now. At least your workshop building skills are well developed. The next one should be perfect! Time to crank out some models! You're kids here are well cared for. Polly gets an airing every now and then, always delightful. I need to make a new rocker assembly though for one of those lower cylinders. Knocked one off in the grass on a nose over.

Fritz Hohn is still fit and well and is the scourge of the Moss Vale skies in his famous Fokker DV11. He may soon have some hunting material though as Brisfish has moved on to a new home with one of our other members so may soon be able to get them both airborne at the same time.

Alan finally has flown the Great Lakes Trainer, after a re certification flight by yours truly. A nice gentle machine. I have flown your Avatar Ryan for Graham half a dozen times. He's nervous about breaking it I think.

Annie is due to come down from her lofty perch when the weather warms up enough for me to get back in the shed. Summer project for sure. Perhaps also the Nieuport if summer is long enough. So many projects, so little time! in a way I envy you you're fresh start, (but you can have the house moves to yourself mate).

Cheers, and here's to blowing the froth off a couple!

Dion,

Glad to have your attention, drop in anytime!

Fuzz,

My old Mini fans are from probably the same era as yours, perhaps early 2000's so may very well be the nylon rotors you speak of. Definitely not Pros as they both have the plastic spinners. I should buy an extra shroud perhaps to use the spare rotor I have now. Balancing rotors is a skill set I have yet to acquire....

Checked the MIG tailpipe diameter and it is 56 mm. Perfect! I like your idea of the ply spacers between the formers but will have to store that for later, I'm too far along now. Right now I'm installing the Inlet ducting prior to beginning the planking. I stuffed up the first one I did and had to rip it out and start over. I'm having trouble unrolling the paper fully allong it's length to glue to the formers. Ended up with a kink in the middle I couldn't get rid of. My present thinking is to get some long thick balloons (Rocket Balloons) and blow one up inside the duct. That will expand it evenly then I can glue it in place. Just have to find some Balloons. We had a party supplies shop here in town which recently closed down. I'm sure they would have had just what I want!

Cheers,
Shane.
Jun 09, 2017, 06:39 PM
Big gov never Works
St. Martin's Avatar
Hi Shane, those may be the Classic glass rotors/plastic spinners. The Pro came out dynamically balanced and alum spinner about 8 yrs ago. The original non glass rotors had the plastic spinner but non glass. These were phased out around 1998. I had the RCG thread where Oliver spoke of the change, in my faves, but lost it. I'll have to search. If you have both rotor types, the difference is obvious.

Good about the exhaust area. 56mm is perfect. While you can get at the Bristol paper duct, seal it. I use reg lacquer. Don't use anything water based. Good idea with the balloons. I'll have to remember that one. I have never had the bulkhead duct openings line up perfectly, for the tube. Just get the intake and fan bulkhead good. You can go back later and fill any bulkheads not contacting the duct. Or, relieve any bulkheads that are causing tension.

Fuzz
Jun 10, 2017, 04:57 PM
Watch out for that planet....
Shane McMillan's Avatar
With some fiddling and the help of a balloon I have got the ducts in place and sealed with shellac. The inflated balloon trick did work well although some bulging of the duct in between the formers did occur, which lead to some puckering when I straightened it out again. Not perfect but acceptable.

Also have begun some planking on the upper fuselage.

Shane.
Jun 11, 2017, 06:58 PM
Watch out for that planet....
Shane McMillan's Avatar
Still gluing planking strips on to this fuselage. Have got he fuse top side planked and a few strips on the bottom side. Stopped to give the upper side a sand.
I have used Deluxe Materials Super Phatic glue to join the strip edges, after attaching each strip to the formers with Medium CA. This Super Phatic glue, whilst it can be applied to the top of each joint and wicks into the joint very well, dries slightly rubbery. I was concerned that it wasn't going to sand very well, thus sanding down the top side now.

The result after sanding is OK but it does leave a slight ridge. A bit like sanding PVA glue. I think for the remainder of the planking I will switch to regular aliphatic glue for better sandability. I managed to snap off the rear fin post with careless use of the sanding bar so fixed that by inserting a short length of carbon rod into its base. Will be fine once the fin structure is built. I have also run some servo lead through the rear fuselage for the elevator servo as this would be hard to do after the fuse is fully planked.

Given that the radio bay is within the cockpit , (unless I make some serious changes to the structure to open up the inside of the fuselage), I will have to plan some wiring entry points there also before I get too carried away closing up the fuse for good. I think there is ample room under the hood for receiver and battery so I won't consider opening up the interior just yet. I considered Fuzz's suggestion of dual batteries saddling the intake duct but as yet I don't think it is necessary.

Cheers
Shane.
Last edited by Shane McMillan; Jun 12, 2017 at 06:56 PM. Reason: spelling correction
Jun 12, 2017, 01:14 PM
Big gov never Works
St. Martin's Avatar
Shane, those rubbery edges need to be stiffened to sand. Rub a little med ca into the ridges. It will sand then. Not sure if available in your area, but I use reg Elmers school white glue for between the planks. I just run a bead on the plank and hold to the bulkheads with thin CA. The school glue works fine. Sands well, dries fast.

Fuzz
Jun 12, 2017, 06:53 PM
Watch out for that planet....
Shane McMillan's Avatar
Quote:
Originally Posted by St. Martin
Shane, those rubbery edges need to be stiffened to sand. Rub a little med ca into the ridges. It will sand then. Not sure if available in your area, but I use reg Elmers school white glue for between the planks. I just run a bead on the plank and hold to the bulkheads with thin CA. The school glue works fine. Sands well, dries fast.

Fuzz
Hi Fuzz,

Thanks for the tip about the CA on the ridges. I'll do that. Your method with the white glue and holding with ca to the formers is how i'm doing it now.
We don't have Elmers brand here (at least I haven't seen it). I'm using regular aliphatic wood glue which I know sands well.

I now have a similar amount planked on the bottom side of fuse and will keep alternating until they join up, then start splicing the ends.

I'm hoping my servos show up soon or it will throw a spanner in the works big time!

Shane.
Jun 14, 2017, 08:27 PM
Watch out for that planet....
Shane McMillan's Avatar
My modelling time this week has been somewhat limited due to having household visitors to entertain. I have however managed to continue installing planks onto the fuselage.

I have been working alternately from top and bottom sides and now now have about 3 planks left to place on each side. I have had to shape the last two planks on each end as the buckling of the strips due to the sideways bend was getting excessive. I have found that I can control the buckling that tends to occur by wetting the plank and heating with the covering iron to steam the wood to proper shape. this works well and can be done after gluing the strip in place.

Before I completely close the fuse planking I will run the aileron servo leads through from the radio bay as this will be hard to do later. Will just have to sand around the lead where it sticks out of the fuse side.

Still waiting for my servos. The joys of buying from China.....

Shane.
Jun 15, 2017, 03:33 AM
Big gov never Works
St. Martin's Avatar
Hi Shane, I install the servos in the tail section, on these twist-off designs. Then there is no pushrod to mess with if removing the rear section. Just an extension.

Fuzz


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