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E-Foamies.com Presents the IMAC Practice Extra Foamie ARF! Kirby Pople shares: "I think the best way to sum up this plane, besides a lot of fun, is to say that it makes the perfect advanced 3d trainer. It could easily be used as the plane to try new maneuvers with after they've been nailed on the simulator. It flies more like a balsa or composite plane than most other foam planes, and the best part was that it was nearly indestructible. This is a plane that should be in most serious 3D-ers arsenal, as the "get it out, and beat it up," "all out 3d machine"!
 
Electric Foam Models Presents the IMAC Practice Extra Foamie ARF!
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By Kirby Pople kepople is offline
Old May 02, 2006, 12:00 AM
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Introduction


Wingspan: 34"
Wing Area: 340 sq. in.
Weight: 10-14 oz.
Length: 35.5"
Wing Loading: 4-6 oz/sq. ft.
Prop: GWS 10x4.75 SF
Rx: GWS Pico
Servos: qty 4
7-9g each
Battery: 3s Dualsky 1050, Thunder Power 3s 1320
Motor: Microdan 2510
ESC: CC Phoenix 25
Manufacturer/
Available From:		 E-Foamies.com

When I was approached about reviewing this plane, I knew I wanted to do it, but I was not sure what to expect. The thread on RC groups said this plane was designed to be an IMAC practice plane, so I was extremely curious.

I thought, "There is no way a foam plane can fly precisely through a 3d routine unless some of the known foam plane obstacles, such as the tail twist and weak control surfaces, are overcome "

I have flown designs from Electric Foam models before and they all flew very well, so I was looking forward to seeing what they had come up with this time. The benefit to an EPP foam plane for a practice plane was pretty obvious when it came to durability, but in my experience EPP planes were far too flexible to do anything with precision and consistency.

Kit Contents

When the box arrived, I quickly dove in to see what I was in for, as I did not know how the kit was supplied. I was surprised to find out that the fuselage was already built and the wing was already assembled. The fuse was built up from EPP foam pieces, cut and molded into formers, which made a pretty strong structure even though it was not complete.

Pretty much all that was left to do was to install the motor block, wings and electronics. That was a surprise!

This concerned me a little, but I found out it was more than enough. All the important steps were photographed and it was organized in a logical fashion. To my suprise, I did not have to consult the designers’ thread on RCGroups at all! The plane arrived mostly assembled so there was no special jigging required. The fuselage was already built, and the wing assembled!
 
Wing came prebuilt, just add ailerons. The spar was capped with carbon fiber and reinforced with strapping tape. This was already done as well.
 
The recommended powerplant, MicroDan 2510. The Glue arsenal for this plane. The UHU was "the magic stuff" and was very fast to use in all but a few places.
 

GLUE:

There was no mention of glue recommendations, so I did some investigation before getting started. With EPP being flexible, the best choice of glue was UHU foam safe for all parts. For strong bonds that do not involve Depron parts, I could have used Goop. The Goop will attack the Depron but is safe to use anywhere else, so it is suggested for installing the motor block. UHU and Goop have similar properties in that they can be used as contact cement (apply to both sides and let set before joining the parts) or used by applying to one side and allowing sufficient time to cure. I needed a little CA to make the pushrods, and a few odds and ends, but other than that the UHU was the magic stuff and was very fast to use.

Assembly

HOW TO:...

Making the Carbon Fiber Pushrods

The instructions did not cover making the pushrods, so I've detailed it here.

I have begun making my pushrods on all my planes this way after having tried it on several other Efoamies.com designed planes. They were very stiff and light. I went and purchased a lifetime supply of .070 carbon fiber rod, and .032 wire, as well as several rolls of Kevlar thread so I can gradually replace the push rods on some of my older models. These push rods require a lot less support for a long span than straight piano wire.

* Cut 2 lengths of wire about 2” long for each pushrod you are making.
*Hold the Carbon Fiber rod in place and cut it approximately to the correct length.
 

* Make a Z bend in one of the 2” long pieces of wire, the other will be straight.
* Rough up the wire on some sandpaper.
 

* Use CA to tack the wire to the CF rod and apply some zipkicker.
 

*Wrap Kevlar thread around the end of the wire only, then coil the thread around both wire and the CF rod.
* The final wrap of thread should be on the wire only on the other end from where you started.
* Apply some zip kicker.
 

* Repeat this step for the other piece of wire leaving about 1” over hang of the wire.
 

 

Making Over & Under (Barndoor) Hinges

To get nearly 90 degrees of travel for a control surface, the over & under hinges are the best choice. I use regular Scotch Multipurpose tape or packing tape.

The wing came with the trailing edge wrapped in strapping tape. This gave me a good place to bond the tape, as tape would not stick to the EPP for long. I used regular Scotch Brand multipurpose tape. (I used the shiny kind, not the matte, which will not s
 

*Pull 2 strips of tape approximately 1 ¼ inch long..
* Flip one strip over, and overlap the other piece the thickness of your foam, in this case 6 mm. Close is okay.
*Apply the strips to the rudder in this case. Place them so that the tape overlap
 

* Fold the strips back on the opposite side and double the end just to hold it in place.
 

* Hold the surface tight against the surface to adhere it to, in this case the vertical stab.
 

* Fold the tape back and secure it to the vertical stab. The tighter you make this joint when you stick the tape down, the less slop you will have in your surface.
 

* If done properly, you can move the surface 90 degrees in both directions.
 

The steps that were involved were covered in the instructions and on the RCGroups thread, but I will cover some of the highlights of what I got to do.

I used CA to insert the wing and glue it in place. I but found out later that UHU would have worked as well. I was able to lift up the sides of the fuse and spread it, then push the parts together.

NOTE: For what its worth, the CA has not broken loose yet.

Installing the tail group was a snap once I had cut the opening in the fuse, and made a temporary slit in the fuse to slide the elevator into place.

The bottom of the fuse was left open so that the builder could run the wires for the receiver.

Ailerons are beveled and tape hinges are used. I used CA to glue the tail servos in place, but found that goop would have worked as well. I tried goop here, on the aileron servos, and, to date, they have not come loose.
 

The steps for making the carbon fiber pushrods were not detailed in the instructions, so I've detailed how to do it in the side bar. The same techniques are used to make the landing gear for some of the other designs. In the case of the Extra, the designer notes that they went with solid wire on this plane since it will not break.

Once the pushrods were built, I was able to install the horns. I typically center the servo, glue it in place, then position the horn in the slot before gluing. It was recommended that I use the Dubro or Great Planes micro adjusters on the servo end of the linkages. This just made life so much easier. Once it’s all dry, I could center the surface and tighten the screw and I was done.

Tail skid was made of two pieces of carbon fiber rod, foam safe CA’d to the fuse, and then joined together with CA and Kevlar thread. This system was very strong. I added this piece of Carbon fiber to keep the two elevator halves from flexing independent of each other during high G maneuvers.
 

Installing the motor:

The motor was mounted to a thick block of EPP foam that was wrapped in strapping tape then glued in place. A plywood mount used for the motor's back plate was then glued to the block. It was recommended that the strapping tape go all the way around the block both horizontally and vertically. I slid the block in place and marked it, then removed it and put Goop inside the airframe. I slid the block back in place, and let it cure for several hours, which produced a really secure mount. I then could have used Goop or Epoxy to glue the plywood to the tape-wrapped EPP block.

I used a sheetrock sanding foam block to add the bevel to the motor mount block to match the taper of the fuselage sides. Strapping tape was wrapped around the block to keep it strong.
 
I slid the block in and glued with Goop.
 

All that was left were cosmetic items such as gluing the cowl and bending/installing the landing gear wire...

The added top foam to the fuse using UHU, and T pins to hold in place. I used Krylon Shortcuts red, orange, yellow, and white to paint my wheelpants.
 
I bent the gear wire and installed through the fuse. The canopy was very well produced and requires minimal trimming.
 
I added a false floor made of 3mm Depron to hide the receiver and wires. This ensured a little classier look, it was totally removable, and did not add measurable weight.
 

That was all there was to that, now it was time to fly!

 

 

Setup:

For throws, I set full deflection on all surfaces for 3D. If I placed the horns so that the hole was on the hinge line, and used the second from the bottom hole on the horn, I could get nearly 90 degrees of elevator throw from the standard supplied long arm of most servos. The rudder and ailerons were only about 45 degrees, which was more than enough.

For low rates, I chopped these throws in half, and about 15 degrees on the elevator, which was more than enough for maneuvering through sport flying. The plane has a huge CG range, of 1”-2” behind the spar. I found about 2 ¼” to be neutral with my particular plane. If you intend to do more sport flying, you would want to start at the forward limit. I set expo at about 35% on low rates, and ended up with about 60% on high rates.

 

A tip for setting expo: Move the stick about ¼ deflection and make a mental note of where the surface physically is. Dial the expo on high rates so that with about ¼ deflection the surface is in the same place. This allows the pilot to ensure the plane will fly the same on high rates and low rates through the first ¼ stick of travel, allowing better control when landing or taking off.

Flying

CG was neutral with it set at its rearward limit. Hover was not difficult, but required an active set of thumbs.
 

The plane was billed as an IMAC practice type plane and it certainly flew bigger than it physically was. It is still a foam plane and as such it had some foam benefits, such as being easy to fix and not having traumatic results when I made a mistake that sent it piling into the ground. (See the video for an example of this). It flew through the precision maneuvers better if I kept a little more speed and flew it on low rates. It was very nimble and, being short-coupled, spins and snaps were tight if not a little too deep. Down line and vertical rolls were axial with no differential required, threw a snap in for a touch of class and it could be stopped where I wanted it. Down line outside snaps appeared to accelerate their rotation speed on the way down.

In knife-edge, the plane had some coupling, but in my case, it was mostly pilot-induced. There was a slight pitch to the gear with the CG at the rear limit. Knife-edge loops had minimal roll out at the bottom, which impressed me quite a bit. If I kept full power on during the loop, the Extra flipped in a pretty tight radius. Top-side snaps from a knife-edge position were pretty weak and wobbly but an outside snap looked really nice.

No reason to fear the deck with EPP. Tons of rudder authority in knife edge.
 

Indoor Flying:

This plane could be flown indoors very well if kept light. The plane can fly slow enough to maneuver in a small gym and still do quite a few maneuvers in the confined space. The beauty of this plane indoors is durability. Several arrivals and inverted landings resulted in little more than a loose landing gear leg. At one point during this plane’s first time indoors, I had a midair with the designer flying his lighter Extra. Both planes flew away essentially undamaged. I had a slight tear in the wing EPP, which was easily mended with UHU. The plane can fly indoors consistently, but really excelled when I stepped outside.

Outdoor Flying:

Here is where the Extra proved it was a 3d powerhouse. You can see the report card for its outstanding qualities, however a few of this planes maneuvers deserve special notation. One of its best qualities was solid flat spinning. Hit the gas and go vertical, add a few vertical rolls, a snap or two for style points, then level at the top. Kill the power, add full left rudder and full up elevator, then add a smidge of power and the plane just yaws around its left wing tip nearly flat. If the wing was not completely stalled, it was still a deep spin, but not entirely flat. It did very nice powered climbing flat spins as well, tighter in fact than power off descending spins.

Inverted flat spins were similar but the Extra seemed to take a little more power to flatten out. A blender entry into the inverted flat spin really was spectacular, with a very tight acceleration around the wing tip, then slowing into a beautiful flat plate.

Another bonus was the planes tumbling, waterfall, and flipping abilities. This plane could just flip around its spar like it was on a string. Roll inverted, reduce the power and add full down elevator. It flipped very quickly, and adding power on the up line side made the Extra almost maintain altitude. Indoors, I was able to do three consecutive flips before needing to bail. Outdoors, I could have made myself dizzy before I lost altitude. The Extra was able to do a near perfect waterfall. Pull the wall, then full down and the plane tumbled over the waterfall straight down with little rudder required.

While the Extra walled on a dime even with a lot of airspeed, it did require me to be on the rudder in the hover. It was actually pretty easy to hover with low rates on the elevator since the plane was pitch sensitive with the CG this far back, but once I got it stabilized it torque rolled very easily. Tail slides were nice with the Extra falling backwards a good few feet before I really had to get on the sticks. It also made a nice whip stall out of it to recover. Since the CG was almost neutral with it set to the rearward limit, the Extra will exit straight and level with just the addition of power at that point.

The extra walled on a dime, even with a lot of airspeed. It did require rudder input in the hover, and torque rolled easily.
 

Enter a descent, add a roll or two, then pop full elevator. The plane parachuted with little rudder required until I started into the elevator. I had to fly the rudder fairly aggressively to hold the elevator all the way to the ground, but with the near 90 degrees of elevator throw I was able to get with barn door hinges, and these control horns, I did not need any power to keep the nose up. Add a little power and the plane flew a good harrier. I am still working on my skill at harrier rolls, but I can do several with the plane easily. Inverted Harriers were more stable than up right of course, and less rudder activity was required. That was good news for me as I usually blow this maneuver once or twice a flight. The best part of this plane though, was that a rudder dumb thumb low to the ground was not a big problem since it would not tear up the plane.

Grading the IMAC Practice Extra Foamie

3D Report Card

Waterfalls: 8
Flat Spins: 10
Blender: 9
Rolls: 8
Knife: 7
Flat Turns: 8
Inverted Flat Spin : 8
Flat Turns: 8
Power: 9
Harrier: 8
Inverted Harrier: 8
Parachute: 8
Wall: 8
Elevator: 8
Power Off Snaps: 8
Parachute: 8
Knife Edge Loops: 8
Flip: 8

Precision flying through 3D maneuvers

  • Rudder needed on climbs
  • Roll fairly axial, but needs rudder to track straight
  • Vertical rolls axial
  • Cuban 8’s good if correct lines with rudder
  • Loops use rudder over the top
  • Knife lots of rudder available, with minimal coupling to the gear and a touch of aileron





Flight Video/Photo Gallery

Downloads
Type Name
Size
The IMAC practice Extra flies great!
10.30 MB

Conclusion

I think the best way to sum up this plane, besides just saying it was a lot of fun, is to say that it makes the perfect advanced 3d trainer. It could easily be used as the plane to try new maneuvers with after they've been nailed on the simulator.

It did fly more like a balsa or composite plane than most other foam planes I have tried, and the best part was that it was nearly indestructible. That gave me the benefit of being able to let others try it and show me what they were able to do. Then I could try out what they showed me without the fear of tearing up a good flying balsa 3d plane. This is a plane that should be in most serious 3D-ers arsenal, as the "get it out, and beat it up," "all out 3d machine."

 
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Old May 02, 2006, 10:33 AM   #2
Motor Maniac
 
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Location: Orange County, CA
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Very good article with plenty of build detail. One thing that is missing that I always want to know about is battery installation/removal. This is one of my deciding factors when looking at an airplane. Poor battery access will disqualify a plane that flies great.
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Old May 02, 2006, 11:40 AM   #3
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10,

Thanks for the compliment...
The battery access could not be easier. There are two flaps in the bottem of the plane that you open to get to the battery. I will try to shoot it and put it in the additions.

Regards;
Kirby
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Old May 02, 2006, 02:36 PM   #4
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Thanks for the excellent review Kirby, and the video too! I have this one sitting in my basement, just waitnig for me to crash one of my other foamies. As luck would have it, I quit crashing now that I have an epp plane waiting for some electronics! I'm only more excited after reading your article on the extra though.

I'm just wondering what you thought of the Micro Dan? From what I have heard it seems like the most overlooked little power house out there. Alomost sounds too good to be true. I bought one with the extra when Tim had a combo sale and the quality looks excellent.

You've inspired me. I'm off to try and crash a foamy!

Greg
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Old May 02, 2006, 03:54 PM   #5
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GP,
best of luck on your Destruction...

I am pretty impressed with the Dans. yes they are over looked. I have 2 regulars on other planes, including an Equalizer from efoamies.com, and then this double. I just ordered 2 of the Speed microdans for another project to really put them through thier high amp/high rpm testing....

The best thing about the Single Microdan, they are VERY light. The double is light as well of course.

Kirby
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Old May 02, 2006, 09:34 PM   #6
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I think that plane and that pilot is awesome.Can you give us the planes?
Thanks
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Old May 02, 2006, 10:03 PM   #7
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Great review ...excellent tips ...pretty fair flying job (kidding of course!) AND..superb camera work..! So many times the camera work is not good.

thanks,
Bill
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Old May 02, 2006, 10:10 PM   #8
iumop ap!sdn w,I
 
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Quote:
Originally Posted by elaerico
I think that plane and that pilot is awesome.Can you give us the planes?
Thanks

Tim at www.e-foamies.com can give you the planes!

I don't think he's going to give the plans away if that's what you want.

Take care,
Greg
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Old May 02, 2006, 10:44 PM   #9
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Great work as ususal, Kirb. I've worn my original Extra out, I'm waiting on the replacement - it's as good as you say!
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Old May 02, 2006, 11:35 PM   #10
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Thanks Guys;
The video was shot by Kelvin Ritchie. He practices the video shooting and tries his best to keep it in the frame. I was having some fun with him in the video as well trying to make him dizzy flying high speed circles around him, but he never fell down. He only flinched when I nearly hit him in the head on an inverted harrier...chicken.

Thanks for the good work on the video Kelvin...

Kirby
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Old May 03, 2006, 11:33 AM   #11
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Well done Kelvin ...we all remember you from "crooked E3D fuselage" days....oh so long ago, EH..!
Ain't THAT a nice claim to fame..!

Still gotta get my E3D airborn, it's close..so many planes!

Back on topic...THIS is one of the three BEST reviews I've read in four years of being "Ezoned"...!

thanks again..
Bill
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Old May 03, 2006, 06:21 PM   #12
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Nicely done Kirby! I really appreciate the "How-To" sidebars. I'm writing a review on the RCGroups foamy now. May I reference your article for those how-tos? You've just saved me a lot of typing!

On pushrods, I'm using heatshrink on the Z end and just using a regular (not mini) EZ Link on the control horn. The carbon rod slips right into the hole of the EZ Link, viola. The weight should be similar, if not a bit lighter. Any reason not to do it this way and change to your style?
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Old May 03, 2006, 08:44 PM   #13
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Nice review Kirby!

I get a kick out of flying the foamies, when the wind is down!

I'm glad to see more foamies coming to market with more than a profile design. I don't think I've seen as much axial performance from a foamy, as you got from that one. I'm sure the rounded edges gives quite a bit less bluntness when pulling the tights.

Nice!

John
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Old May 03, 2006, 10:44 PM   #14
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RetiredVtt;
Thats quite a compliment. Thank you very much.

JWarren;
Could not agree more on fuse fuse foam. I am looking for the first true pattern practice plane to come out, and I see them slowly starting to immerge.

Jludwick;
Only problem is that when I have tried to use CF rods in an Easy connector, the screw crushed the CF rod when I cinched it down enough so it wont slip... The Shrink tubing method is another way to do the wire connection, and thats the way mountain models does thier push rods, but the kelvar thread comes with this kit, and so thats what I did. Weight wise the difference between the two is negligable. PM me if you have any other questions...

Kirby
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Old May 04, 2006, 03:29 PM   #15
55' Edge is too sweet!
 
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Great review again! I have enjoyed watching you fly this one. You have to atribute some of it to the thumbs, though. Good flying!

dp
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