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Freewing Mig 29 EDF to Turbine Conversion

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Freewing Mig 29 EDF to Turbine Conversion

Old 11-13-2020, 10:07 AM
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Viper1GJ
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Default Freewing Mig 29 EDF to Turbine Conversion

This conversion is in collaboration with my friend Keith (Yellowbird911) and is still a work in progress at this date. As of now the jets have not been flown. We hope to test fly this week. This turbine conversion is not new but the fuel system is unique. Keith designed and 3D printed the functional external centerline fuel tank which made this one of the easiest conversions I have done. Here are the finished photos.


Finished jet


Turbine mounted between EDF tunnels



Functional 3D printed semi scale center line fuel tank with FOD shield for turbine.

NOTE: Keith can not print and sell the tanks due to free design software use restrictions, but he has posted the 3D CAD files in Thingiverse. You can download and print as many as you like for free.
The Thingiverse link is:

https://www.thingiverse.com/thing:4651488


Front of tank

Last edited by Viper1GJ; 11-13-2020 at 01:29 PM.
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Old 11-13-2020, 10:14 AM
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And it starts with a box. Keith and I saw the FW Mig 29 EDF fly at the SC Tiger Meet in October and immediately thought it would be a perfect turbine conversion. Keith has done 6 and I have done 4 using the K-45G3 and so far this is the easiest one to do. It requires very little foam cutting.


Touch up paint from Home Depot paint samples.


Paint match for AB nozzle shrouds


Touch up paint for AB nozzles that I had in the shop.
Old 11-13-2020, 10:39 AM
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Mounting turbine


Based on Keith's recommendations and experience from his F-14 conversion I put in some down thrust to compensate for the under slung turbine mount. The amount was 2 degrees based on highly complex TLAR (that looks about right) calculations. The EDF thrust line is the edge of the EDF hatch. I made a card board template to transfer the 2 degree down to the foam.


Stop right here and don't do this!
Next I made a wood template to use as a hot wire cutting guide. I forgot to add the space above it needed for the turbine mounts. As a result my slot was 1/2" too low. If you use this method be sure not to follow my photos as you will have to shim the turbine up about 1/2" to clear he bottom of the fuse.


Hot wire cutter


Slide wire back through the foam. Depth of cut is controlled by the pliers next to the wood.


Slot cut


ARRRGH! My slot was cut too low as I forgot to compensate for the radius of the turbine mount.





Now the fix. Trace turbine wings on foam.


Mark foam to be removed


Plywood rails in foam


Hot wire cutter to remove foam


Foam removed


2 1/4" ply shims placed on top of turbine rails. YOU can avoid this fix if you just cut the slots where they need to be in the first place!


Ok here


Parts ready to glue in


E6000 used to glue in wood. Keith did a glue test with BSI Foam Safe, E6000, and Six10 epoxy. By far the E6000 was best because it bonded to the foam much better.

Old 11-13-2020, 10:47 AM
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Install pitot tube


I will be using a Digitech CTU with an airspeed sensor. Foam had to be removed from the radom to install the pitot tube.


Careful at the nose since removing too much foam will cut through the surface. Just enough clearance for the air tubes to the module is all that is needed.


Done


Doesn't look bad.
Old 11-13-2020, 11:00 AM
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Replacing stock stab servos

There have been some issues with the Mig 29s crashing due to loss of pitch control. The events are well covered in other threads and I won't repeat here. Keith and I decided to replace the stock micro servos with hi torque mini servos and change the stock linkage to 4-40 rods.



I also replace the stock servo extensions with Powerbox Maxi wire


Existing servo hole cut to larger size


Edges cleaned up




New servo installed


4-40 threaded rod used


Pushrod squared to servo arm not the fuse side



Carbon sleeve over threaded rod and inner hole used in servo arm.
Old 11-13-2020, 11:12 AM
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The has been much discussion about the stab mounts twisting on the stock fuse so Keith and I modified the stab mounts as follows.


6mm aluminum rod cut to 190mm


Rod had to be sanded some to fit inside the stab bearings


6mm drill bit used to drill through foam in nozzle


Areas around holes scuffed inside nozzle


Dry fit of plywood hard points inside nozzle


Hard points glued in with E6000


This mod stopped the twisting on the stab bearing in the fuse. Very stiff now.


Mods painted to match nozzle color inside and out.
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Old 11-13-2020, 12:01 PM
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What a great step by step amigo. I have an X45 that I intend to use on my conversion. Any chance I can chat with ya about getting a centerline tank? Thank you buck
Old 11-13-2020, 01:41 PM
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Originally Posted by Viper1GJ View Post
The has been much discussion about the stab mounts twisting on the stock fuse so Keith and I modified the stab mounts as follows.


6mm aluminum rod cut to 190mm


Rod had to be sanded some to fit inside the stab bearings


6mm drill bit used to drill through foam in nozzle


Areas around holes scuffed inside nozzle


Dry fit of plywood hard points inside nozzle


Hard points glued in with E6000


This mod stopped the twisting on the stab bearing in the fuse. Very stiff now.


Mods painted to match nozzle color inside and out.
Thats a great idea to reinforce the stabs!
Tone
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Old 11-13-2020, 03:36 PM
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Thingiverse is taking forever to process the files I uploaded for the tank. Here is the link to my files on Google Drive.

https://drive.google.com/folderview?...PeQoCYHNVN7Eu7
Old 11-13-2020, 04:18 PM
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Originally Posted by Viper1GJ View Post
The has been much discussion about the stab mounts twisting on the stock fuse so Keith and I modified the stab mounts as follows.


6mm aluminum rod cut to 190mm


Rod had to be sanded some to fit inside the stab bearings


6mm drill bit used to drill through foam in nozzle


Areas around holes scuffed inside nozzle


Dry fit of plywood hard points inside nozzle


Hard points glued in with E6000


This mod stopped the twisting on the stab bearing in the fuse. Very stiff now.


Mods painted to match nozzle color inside and out.
Thats a great idea to reinforce the stabs!
Tone
Old 11-13-2020, 06:34 PM
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Turbine mounting and aluminum tape


Turbine mounting holes drilled


Turbine screwed on with 3/4" screws to get through all the shims into the mounting rails.


HVAC tape applied to areas around turbine hot section





Gunmetal and grey paint applied to HVAC tape to blend in to the fuse colors later.

Old 11-13-2020, 06:46 PM
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The Tank

What makes this foamy conversion so easy and different is the functional centerline fuel tank. There was not much room for fuel near the CG on the inside of the fuse. Keith had 3D printed external tanks for his F-14 conversion and suggested an operational centerline tank. I found a few photos of the Mig 29 with centerline tanks and Keith went to work making CAD magic.


Good view a scale tank


Rear view


I read that the black hole in the rear of the tank was an APU exhaust port that went through the tank. Could not confirm but it makes sense.


This stuff is way above my paygrade.



Screen shots of CAD magic




And from this you can print real stuff. Who would have ever thunk it?
Old 11-13-2020, 07:18 PM
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The 3D printed semi scale external fuel tank is the heart of this turbine conversion and is what made it so easy since there was very little foam carving needed to fit in the fuel near the CG. This was my first time to do an external tank so I basically followed Keith's lead and advice.


The tank comes out of the printer in 5 pieces. Front, rear, 2 baffles, and a fuel tube holder (not shown here). The tank is printed out of clear PETG filament which Keith says is fuel proof. It is later sealed with a coat of epoxy resin inside and out.


The rear section has a flat front face that forms the rear wall of the tank when the rear section is joined to the front section. The rear section is hollow and is the FOD shield for the turbine. Only the front section holds fuel. We estimate it holds 40oz of fuel. With the 14oz header tank inside the fuse the total fuel capacity is about 54oz plus air trap fuel.


The rear section plugs into the front section with about a 3mm overlap and forms the back of the tank


The two baffles are indexed on small tabs inside the front section


This shows baffles tacked in position with CA

Last edited by Viper1GJ; 11-14-2020 at 04:49 PM.
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Old 11-13-2020, 07:23 PM
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Man, how are some people born with all the talent and the rest of us are just trying to keep up!!

Outstanding! Just Outstanding!!!

Old 11-13-2020, 07:26 PM
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Hey Rav,
Keith my buddy has the talent, I just beat on it with a hammer till it looks ok.
Old 11-13-2020, 07:31 PM
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There is no clunk in the design? Air is trapped in the header tank instead?
Old 11-14-2020, 04:56 AM
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Gary I noticed in the videos the stabs bow during flight when the flaps are lowered in particular. I would be inclined to glass the stabs as a final step. Looking forward to your flight videos.
Old 11-14-2020, 05:03 AM
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Rav, yes the theory is the air is caught in the header tank in the fuse. Ill post some photos to show the total system.

Bob, I had thought of that or maybe a strip of carbon tow on top and bottom for same purpose. Still working on it but the stabs are where most of the flex is now after the stab pivot rod mod. Thanks.

Last edited by Viper1GJ; 11-14-2020 at 06:22 PM.
Old 11-14-2020, 11:55 AM
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Installing header tank


Dubro 14 oz tank in rear battery compartment fits perfectly.


I removed the factory wood parts and cut out the foam to make a flat floor for the header tank


Foam removed


Header tank floor. NOTE: I did not yet have the centerline tank when I cut this piece. If you do this floor make it the full length of the compartment since the front lug of the center line tank will be mounted to this wood piece. I had to extend mine later.


Area for foam removal for tank hold down strap. Make the wood extend all the way to the front of the compartment for later centerline tank mounting.


Foam removal


Thin Velcro strap in


Tank in

Winged felt clunk part number from DDM Racing Davesmotorsports.com if you want to use one


WInged felt clunk


Tank build. I forgot I only needed two brass tubes and later removed the third tube.

Last edited by Viper1GJ; 11-14-2020 at 06:24 PM.
Old 11-14-2020, 12:01 PM
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Turbine mount touch up paint


Tamiya X-10 Gun Metal matches the dark silver in front of the AB nozzles for the turbine mounts




Old 11-14-2020, 12:29 PM
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Mounting front half of centerline tank


Tank parts


1/4" plywood used for main tank mount into foam. Plywood needs to extend inside the EDF ducts for later reinforcement


Plywood mount and tank in the NACA cheater holes. Tank lugs are against the aft edge of the NACA hole


Foam removed down to bottom of fuse on each side


Lines for foam removal for plywood mount


1/4" foam removed making the plywood flush with the fuse bottom


Dry fit plywood in slot


Holes drilled to fit tank mounting lugs and 6-32 blind nuts installed, CA glued, and taped over to prevent glue from fouling the threads. E6000 will be used to glue in tank mounts later


6-32 bolt with rubber sealing washer to hold against plastic mounting lug



From inside the duct. The plywood extending inside the duct is for reinforcement against the foam since this is the main part holding on the tank under G loads


Rear tank part dry fit to ensure everything is correct.

Last edited by Viper1GJ; 11-14-2020 at 06:26 PM.
Old 11-14-2020, 12:39 PM
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Front tank lug mount


Tap front lug hole for 6-32 bolt


1/4" ply front mount bolted to tank lug


Plywood outline traced on foam fuse bottom


Area of foam removal


Remove foam from under header tank floor. This is where I learned I should have made the tank floor cover the entire front compartment.


Ply wood tank mount rounded to fit foam shape behind nose gear doors. I did not work too hard here since it on the bottom and out of site


Header tank floor extended, drilled, and counter sunk for a 6-32 flat head bolt


Header tank fits over bolt


Front and rear tank mounts glued in with E6000, weighted, and let dry overnight


Internal plywood braces cut from 1/8" plywood


Brackets installed on inside of each duct. Epoxy is used on the wood to wood contact areas and E6000 is used on the wood to foam contact areas. This to help spread the load over the foam holding the tank on the jet during G loads

Last edited by Viper1GJ; 11-14-2020 at 12:46 PM.
Old 11-14-2020, 01:02 PM
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Rear tank mounts and turbine air inlet holes


Rear tank section is taped in place on front tank section and then the FOD cover lines are traced on the foam


FOD cover lines traced on foam


Turbine air inlet cut lines marked just below the FOD cover lines


Turbine air inlet holes cut by removing foam from the EDF hatches


Turbine inlet holes


FOD shield mounting tab location marked on foam just below the FOD cover line. Slot cut with hot wire as before for 1/8" ply mounting tabs


Mounting tabs installed and drilled


View from the rear


Rear section of tank FOD cover secured with servo screws. Now the front section of the tank and the rear section of the tank can be glued together and held in alignment with the front mounting bolts and rear screws while epoxy is curing....but not yet!

Old 11-14-2020, 01:42 PM
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Sealing, installing fuel tubes, joining, and painting the tank


The inside and outside is sealed with a coat of epoxy. We used West Systems 106 with 206 hardener. I mixed 60 grams and it did the whole job. First prepare a place where the epoxy can drain out when pored in the front tank. Next prepare a hanger system that will allow parts to drain and cure with out touching. I used a coat hanger wire on the front part and the mounting holes in the FOD shield on the rear part. Keith used a screw in the front lug. Pour enough epoxy in the front section and roll it around to coat all the inside surfaces. The epoxy will secure the baffles to the sides. Allow the epoxy to drain out and then brush a coat on the outside of all surfaces on both front and rear sections. NOTE: This step must be done before the fuel tubes are installed.


After the epoxy is cured the hardened drips are ground off the front and rear sections for a good joint


Rear section cleaned up.


Next the 5/32" brass pickup tube hole is drilled aiming at the center of the rear baffle.


The drill passes through the front baffle and the tube is pushed in through the center of the rear baffle


The brass pickup tube is bent to fit prior to tack gluing in with CA. The fuel tube holder is shown here.


Fuel pick up tube is tacked in with CA at the front hole and is NOT glued to the holder. Only the holder is glued to the bottom of the tank. This allows the tube to expand and contract and flex inside the tank and not stress the glue joints.


Vent tube drilled and installed on left side here. After tacking in with CA and getting proper alignment the tubes and tubing holder are glued in with SIX10 epoxy. The tube holder is also epoxied to the bottom of the tank. NOTE: the tube is not glued into the holder, only the holder glued to the tank bottom so that the tube can flex in the holder. On my jet I chose to put the pickup on the right and vent on the left.


Next a piece of plastic is laid across the fuse bottom where he tank joint is. Then SIX10 epoxy is applied to the front and rear sections and they are pressed together. Squeeze out is cleaned off and then I taped the tank parts together. Then the tank is transferred to the fuse mounts and screwed down. This photo shows the tape removed and the tank is screwed to the mounts and ready to cure.


It is critical not to get epoxy in the fuel pick up tube. I had it about 1/2" ahead of the joint line.


Tank removed when epoxy cured. An under water leak check should be done and any pin holes fixed. I had no leaks. I rough sanded the tank with 220 wet sandpaper.


I brushed on a thick coat of 2K auto primer and let it cure


Next was a wet sanding with 220 paper. I kept telling my self " its on the bottom out of sight" so I didn't go overboard with finishing


Next I brushed on 2 coats of KlassKote satin white epoxy paint and let it cure overnight


I free handed the grey and black paint on the rear section


Good enough, Its on the bottom!


All done it was 14.1 oz and came out much better than I expected. I was happy with the results.

Last edited by Viper1GJ; 11-14-2020 at 04:47 PM.
Old 11-14-2020, 05:07 PM
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Making fiberglass NACA hole FOD covers


2 layers of 3 oz cloth placed into two cut off 1 gal zip lock freezer bags like envelopes


Epoxy resin poured in on glass cloth and excess resin squeegeed out


Freezer bags taped on engine necelles to cure


Cured parts cut to size and corner holes drilled over NACA holes. The center line tank holds the lower part of the covers in place.


Plywood squares imbedded in foam to hold screws


Covers painted and trimmed to clear tank mounting lugs








Covers installed with small screws

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