I spent 3 evenings hogging out the inside of the fuselage enough to mount a Wemo midi 11" aft of the "stock" location. This was accomplished using a wire wheel on a drill for the rough cut and 80 grit paper wrapped around a big 500 count vitamin c bottle for the final shaping.
With the fan in the modified postion it comes up about 9-1/2" from the rear of the housing to the end of the tail cone. Much better than the 20" that would have been in the stock location. That was after shortening the the cone about 1-1/4" as it only had a 55 mm exit which is much to small for a 90mm fan.
After the initial cutting the exit is at 3" but still needs a little more.
9/12/08
After a little more work in opening up the aft portion to get a 3-1/4" exit size the fan unit is test fitted.
9/13/08
To make inlet ducting (from factory position to the modified one) I made a couple of light ply formers. One is the same size as the inner fan housing (89mm), the other the same diameter as the factory opening (96mm). These were placed inside a tube made from a clear desk protector spaced 11" apart.
The tube is "glassed" using 3" wide strips wound in a spiral with a 50% ovelap. I also wrapped a spare fan housing with wax paper and put a couple of wraps of cloth & resin around it to make the adapter ring.
Before removing the ply formers the outside is sanded to remove some of the rough burrs. Still looks pretty ugly on the outside.
But, the inside is nice and smooth.
The spare housing is again wrapped with wax paper and the adapter ring slid on. The fan end of the tube is coated with 5 minute epoxy and slid inside the adapter ring until it butts against the fan housing.
This shot down the tube shows how the inside of it aligns almost perfectly with the inside diameter of the fan housing. Somthing that helps increase performance and cut down on noise.
The assembly is test fitted to the fuselage and trimmed as needed on the front for it to fit to the stock inlet lip.
A shot "down the throat" with fuselage sides temporarily joined. I was hoping to show how well the insides of the inlet tube aligns with the factory inlet, but it's a little on the dark side.
Final exit opening size, 3-1/4" even though it meant removing about 1-1/4" from the rear of the cone.
9/15/08
I attached the wings to the fuselage yesterday after installing the servos. (also glassed the bottom of the wing, vertcal fin and did some paint work) I really didn't feel right about relying on the glue joint only so decided to add some carbon fiber spars.
I found enough 6 mm rod in my parts collection to make two 5" spars and marked a long drill bit with tape for the proper depth into the wing.
The hole is drilled through the thick portion of the fuse (drill bit still in place to show alignment location) This gives about 2-1/2" of rod in the fuse and the same into the wing past the molded hump.
The wing may still break, but it will now take a large chunk of the fuse with it if it does.
A generous amount of 30 minute epoxy was pumped into the hole and coat applied to the CF rod before pushing it in to just below the fuselage sides. Excess was cleaned away since this is the area where my home made fiberglass ducting meets with the factory inlet.
Click here for RC Groups discussion thread on this model.
9/19/08
Even after getting the heat sink for the motor still didn't like the heat index on the Mega. So, I pulled the Hacker B50-9XL out of my Mirage and installed it in the fan.
Clear silicon adhesive was used where the fan housing contacts the fuselage and at the front of the inlet ducting as well.
Fuselage halves joined with 30 minute epoxy.
9/20/08
Steering servo and linkage installed prior to joining front fuse halves
Halves joined with 30 minute epoxy and rear wedge added. This wedge plays an important part in the structural strength of joining the fron to the rear fuse sections.
I added the hole shown here to help flow some air through the battery compartment.
Front section joined to rear with 5 minute epoxy. Here I applied glue to the upper portion 1st and allowed it to set before repeating the procedure on the bottom.
Wires routed through into the forward fuse. I also added a CC 10 amp BEC to my wiring since I really don't trust an ESC to supply voltage for the 4 servos.
At this point the basic airframe is pretty much complete and the lower fuse has had all the seams "glassed" with light cloth and Minwax Poly Acrylic. Now for the hard part. Letting it dry so I can sand and prime it.
9/24/08
Paintwork has been completed and time to install a battery tray. There was so much fuss about this one coming up nose heavy, I guess I overdid it with the fan location. To attain balance I can't use the existing foam compartment. 1/8" light ply doublers are epoxied to the fuselage sides with a 1/4"x1/2" spruce rail for the battery tray to attach to. I went ahead and added a 1/4" ply block for a bungee hook in the bottom of the fuse while at it,
1/8" light ply battery tray made and epoxied to the light ply doublers. Yhe receiver and all the servo wires will wind up occupying the space originally planned for the battery. The cutout in the center will allow for more cooling on the battery and even give a little access to the steering servo & linkage.
That's a Flight Power 5000 ma 6s Evo 25 in the compartment right now and it balances the model with it pushed all the way to the rear.
I plan to run a Zippy R 4800 5s 25c once it arrives as I don;t know how long the Hacker would live running on 6s and it would be about impossible to get to it or the ESC without doing some major cutting on the fuselage.
The canopy will still fit with the 6s pack in place, but not with the front velcro strap attached as it's in the same location as the lowest part of the canopy. Bummer. Otherwise I'd be really tempted to try it with "throttle management" on 6s.
I wasn't happy with the holding capability of the included magnets so added some velcro strips to the bottom side of the canopy with mating strips attached to the fuselage. The front one required a slight recess into the foam for the canopy to sit flush & tight.
9/27/08
It took a while to clean up the excess wiring. If I had it to do over again I probably would have located the receiver back in the fan hatch area. As it is, all the leads have been neatly bundled and tucked underneath with the receiver and BEC located in what was supposed to be the battery compartment.
9/29/08
Overkill would be the best description for the wire leads on the Zippy 4800 ma 5s 25c pack. It looks like 8 or maybe even 6 gauge wire. The deans connector is there just to give some scale.
Even with the monster 6.5mm Castle bullets I still had to trim away some strands of the wire to get the connectors on. A mating 12 gauge wire connector was made to adapt it to the planes wiring harness. On 5s the Hacker only draws 55-60 amps spinning a Wemo midi fan.
10/2/08
This project has been finished for a while now but probably won't get around to a test flight for another couple of weeks due to Fly-ins happening at the sites I normally fly at.
AUW with Zippy 4800 ma 5s: 5 lbs. 14 oz.
Watts at WOT on 5s:
1050, Amps 55
AUW with EVO 25 5000 ma 6s: 6 lbs.
Watts at WOT on 6s: 1600, Amps: 75
It can be flown on either although running a 6s pack will require throttle management.
10/18/08
The 1st flight attempt was not even close to being a success. Plenty of speed but it refused to rotate and ran into the grass folding all the stock landing gear. My thoughts are that the gear fails to give it enough positive AOA along with being too wimpy to support the weight of the model.
11/8/08
Finally. A day when we were not having 15-20 mph crosswinds, at least early in the morning. So, my neighbor and I went down to SRQ's facility for some test flights.
Increasing the angle of attack made a world of difference and the JAS rotated with no problems. (I found the old nose gear strut from my FlyFly Mirage and it was about 1/2" longer).
In the air it flies well enough but is a little boring at the same time. 1100 watts just is not enough to make this big airframe go fast. About the only challenge is to grease the landing so that the wimpy landing gear design will survive.
Click Image for Flight Video