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Old Jan 09, 2011, 05:52 PM
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Build Log
EOT Models 47 inch Rare Bear build!!

I was asked to do a build thread and test flight on this EOT Rare Bear EPP model. This model was made for EOT models by Hacker Model. EOT models will soon be selling these from the following website.
http://www.equationoftime.com/eotmodels.html

First impressions are...well...impressive! Kit contents are beautifully CNC wire cut EPP, that is then printed in a scale manner. It even has sponsor logos and panel lines printed on the surfaces. All the edges were sanded and the surfaces are live-hinged, so it should go together very easily. And it's a nice big size foamie that should be mild mannered yet handle some wind.
Here's the specs:
Span is 47.24 inches
Weight is 25+ ounces
Power system is for a 250watt to 400 watt outrunner
All EPP with full span carbon rod reinforcements and plywood motor mount and nose reinforcement.

How I will equip it:
Motor, ESC and battery all came from www.valuehobby.com. The motor is their Topstar E480 outrunner rated at around 380 watts. I've flown valuehobby motors in the past and I've been very impressed with the performance for the money. The ESC is their Hobbywing 40 amp and the battery is a Gforce 2200, 30C 3S lipo. I'll be using the Hextronic HXT900 servos on all surfaces. This is about the lowest cost power system I've found and all but the servos can be purchases here in the States from valuehobby.com. Now on to building...

Mike
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Old Jan 09, 2011, 06:13 PM
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First step on the instructions, which are well written by the way, is to join the wing halves. Throughout the instructions they recommend to use CA and accelerator for the build but I'll be substituting other adhesives based on my prior experience building EPP foamies. That being said, I joined the wing with Goop. I had some Automotive Goop from my last EPP slope combat wing so I used it. Goop is bar none the best EPP adhesive for a strong AND flexible joint. The drawback is it takes a few hours to really setup. It also dries clear. The various types of "Goop" are nearly identical in how they work with EPP and I beleive the Automotive Goop has a UV inhibitor in it so it shouldn't yellow in time.
After the wing was dry I measured and cut the slots for the carbon rod reinforcements. Notice my depth guide for cutting the slots. Simply a Sharpie mark on the X-acto blade. I roughed up the smooth carbon rods by sanding them. Then, I pushed the carbon rods into the slot. Before glueing I cut and installed the carbon spar in the other side of the wing. This way I can verify the wing is perfectly true before glueing and locking in any twist. The instructions don't mention this, so I strayed a bit. They also say to use CA and activator. I used thin CA, just wicked it right in over the slot and watched it penetrate. I did NOT use activator as that would, in my experience yellow the nice white EPP wing color. The tradeoff is thin CA takes 10-15 minutes to dry on EPP. One way I've learned to speed this up is to take a dry paper towel over the glue joint. This does two things: 1) It cleans up any excess glue and 2) The tiny towel fibers act to "kick" the glue, starting the curing process. I learned this trick on the Slope forum here on RCGroups.
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Old Jan 09, 2011, 06:22 PM
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On to the fuselage

The same procedure is used to strengthen the fuse. Measure and cut a slot, then fit in carbon rods, then glue. Again I used thin CA and allowed plenty of time for it to cure. The end result was a straight and strong fuse. The fuse is about 2 inches thick. So far in the build I've followed the instructions other than substituting glue strategies a couple times.
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Old Jan 09, 2011, 06:38 PM
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Mark wing for servo locations

The next step is to install the wing in the fuse and then mark the location where the servo wires will come up through the wing and match up with the precut channels in the fuse up to the canopy area where the receiver will go. Once the wing is in the fuse and centered, you push a pen or pencil through the hole until it touches the wing. Then remove the wing and cut a retangular hole through the entire wing as per the instructions dimensions. Then following the measurements stated in the instructions, layout and cut servo pockets for the aileron servos.
I strayed from the instructions slightly in that they said to install the servos so the pushrods go straight back to the ailerons. I chose to angle the servos slightly so that the pushrods are 90 degrees to the hingeline of the ailerons. This will reduce the amount of twisting force on the control horns.
I simply traced the servos and made cuts with an X-acto, then used a pair of hemostats to remove foam in a twisting motion. This is one of many ways to do this. Some use a dremel to router out pockets, some melt the foam. Pick you method and do deep enough so the servos are flush with the underside of the wing.
At this time the pushrods are assembled. Pushrods are made up from the supplied carbon rod that is CA'd and shrunk wrapped to a steel wire with a z-bend on the end.
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Old Jan 09, 2011, 06:55 PM
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Tail surfaces

As per the instructions, the elevator gets a hardwood stiffener buried in it. The hardwood piece is the same thickness as the elevator so I chose to cut a full depth slot to bury it in the surface. To glue this, I used Gorilla Glue Ultra. This is the clear Gorilla Glue that dries white. I love using GG anywhere a lightweight joint is needed and possibly fill gaps. Over wax paper I loaded the joint with glue, then moistened the hardwood joiner with water, then buried it in the surface. Then I taped the joint with masking tape, covered it with another piece of wax paper, then added weight to keep everything flat while the Gorilla Glue cured.
After this cured, the joint was gap free and very stiff. The stab however, was VERY flexy and there was no mention of reinforcements of this and the vertical stab and rudder for that matter. For a larger foamie, I felt this was a bad idea as it would definitely be seeing higher flight stresses than a 10 ounce foamie. I chose to bury a carbon spar in the horizontal stab again with the gorilla glue ultra.
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Old Jan 09, 2011, 07:09 PM
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Vertical Stab

The vertical stab is very flexy so I had to change this. Ideally, I beleive if EOT had provided more of the solid carbon rod as they did for the wing and fuse, everything would be adequately rigid. Since they didn't and I didn't have any carbon rod, I chose to add a full depth spar out of some carbon ribbon I had leftover from a high speed foamie plank wing from my sloping days. I got the ribbon from www.canuckengineering.com. Measurements can be found here. http://www.canuckengineering.com/new...carbon-ribbons

This ribbon weighs next to nothing and it extremely stiff in one direction. I made a cut in the stab that was full depth and in a location that the excess ribbon would go down the part of the stab that gets keyed into the fuse. This should really tie in the stab to the fuse. See pics. White Gorilla glue again since this stuff wicks into the EPP pores and makes a strong, light joint. The end result is dramatically stiff.
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Old Jan 09, 2011, 07:11 PM
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More to come later. So far so good. I'm a 3D flier at heart but I'm really psyched to have something different in my hangar. And the size is just right. Small enough to transport, yet big enough to handle some wind, yet not so big that it requires tons of reinforcement. Stay tuned. I should be working on it tomorrow evening.
Feel free to comment or ask questions.

Mike
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Old Jan 13, 2011, 06:07 PM
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Tail servos

I made some more progress on the build. Next was marking and mounting the tail servos. Following the directions this is a painless affair. Using the instruction's recommendations for both servos makes sure the servo wires will line up with the internal channel that's precut that will lead the wires up to the canopy area. Nice. I chose to ditch the servo extension connectors and just use the pins and then shrink wrap them to hold them together. This makes fishing the wires up the channel very easy.

Mike
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Old Jan 13, 2011, 06:09 PM
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Mike, picked mine up today! Will copy a lot from you :-) Mine is yellow, can't wait for some formation flying

http://www.iflytailies.com/
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Old Jan 13, 2011, 06:22 PM
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Motor mount

The provided motor mount plywood accepts blind nuts on the back for an outrunner's radial mount. The hole locations worked perfectly for the motor I used. One side of the ply mount top and bottom has small holes drilled in for identification. The holes go on the right side of the mount. It's hard to see it but the instructions claim there's an "offset" built into the mount if installed this way. I used fast cure, white gorilla glue for this.
The ESC gets mounted in a cutout in the bottom of the fuse. I'm not sure I like this idea since there's no landing gear on this plane and this is right where belly landing forces will contact, but I thought I'd try it before making any changes. The ESC's throttle wire then goes through a hole into the wing saddle and then up through a precut hole to the canopy area. I like how despite being essentially a profile plane, that all the wires are hidden. Makes for a clean look.
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Old Jan 13, 2011, 06:29 PM
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Mounting tail surfaces

I glued the horizontal stab on with CA and kicker as the instructions mentioned. I usually use Goop or Gorilla glue but I figured CA would be more likely to pop off rather than tear the foam in the event of a cartwheel, possibly saving the fuse. We'll see. The vertical stab however, without much gluing surface area, I used Goop on. The mod I made to the vertical stab with the carbon reinforcement made a HUGE difference once it was all glued together. The extra length of carbon ribbon now buries itself in the fuse tying it all together nicely.
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Old Jan 13, 2011, 06:33 PM
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Quote:
Originally Posted by iflytailies View Post
Mike, picked mine up today! Will copy a lot from you :-) Mine is yellow, can't wait for some formation flying

http://iflytailies.jimdo.com/
Cool! I'm always up for formation flying or some racing...

Mike
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Old Jan 13, 2011, 06:58 PM
aka Schleppmeister
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oh oh, forgot you are good at midairs

http://www.iflytailies.com/
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Old Jan 17, 2011, 07:40 PM
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fitting and glueing the wing

After dry fitting the wing and checking aileron function, I'm ready to glue the wing on. The directions say to use thin CA and accelerator. I used medium CA and accelerator. I wasn't going to use CA at all but after thinking about it CA makes sense. If I ever need to remove the wing to reinstall servos I can probably pop the CA joint loose pretty cleanly, where Goop or Gorilla glue would most likely tear out a lot of foam in the process.
After gluing, there is about an 1/8th inch gap from where the wing saddle was but during manufacture. The instructions say to glue this gap. I chose to fill it with a piece of 1/8th inch plywood. It didn't add much weight and should stiffen up the bottom of the fuse nicely. Should be ready to fly soon.

Mike
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Old Jan 22, 2011, 03:29 PM
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Installing canopy

The instructions say to glue the canopy on but I chose to use some servo mounting screws. To do this I simply cut some short pieces of 1/4 inch dowel rod to go into the fuse foam that I'd then drill for the screws. It worked great. The canopy is very secure, yet easy to remove to gain access to the receiver.

Mike
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