Jim Dall
Sep 01, 1999, 12:00 AM
<div align="center"><center>
<table border="1" cellpadding="4" cellspacing="0" width="80%" bgcolor="#D5EAFF">
<tr>
<td width="50%"><p align="center"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/RYcopy.jpg" alt="RYcopy.jpg (12626 bytes)" WIDTH="387" HEIGHT="154"></td>
<td width="50%"><strong>Specifications as listed:</strong><ul>
<li>Wing San = 48"</li>
<li>Wing Area = 3.33 sq. ft.</li>
<li>Airfoil = Zagi 999</li>
<li>Weight = 19oz (ZAGI1)</li>
<li>Wing Loading = 5.7oz/sq. ft.</li>
<li>Radio = Mixer (V-tail / Elevon)</li>
<li>Motor = Speed 400</li>
</ul>
</td>
</tr>
</table>
</center></div>
<p> </p>
<p><big>Introduction:</big></p>
<blockquote>
<p>I always thought that flying wings were the most efficient practical aircraft design,
but I never considered building such a craft for the following reasons:<ul>
<li>I thought that a flying wing would be difficult to track due the non-existent fuselage
and empenage profile.</li>
<li>I though the airframe was fairly bland and ugly in comparison to traditional aircraft.</li>
<li>I thought the stability and control would be limited.</li>
</ul>
<p>In my mind I would routinely discount a flying wing project until I read Steve
Horney’s column in the June issue of the E-Zone Internet magazine (<a HREF="http://www.ezonemag.com/articles/1999/jun/ctower/clt0699-a.htm">http://www.ezonemag.com/articles/1999/jun/ctower/clt0699-a.htm</a>).
In his column he posted e-mail correspondence from John A. Williams concerning
electrification of the Zagi flying wing. After reading the testimonials in the e-mail
correspondence I thought it might be worth a try. On a subsequent pilgrimage to the hobby
shop I bought the "Zagi-400 complete kit". It included all the components
necessary for a speed 400 electric power system. I figured that if I did not like the
plane I could at least use the speed 400 propulsion system in other models. As it turns
out I love this airplane. This is the most indestructible airplane I have ever flown. The
leading edge of the wing is made of expanded polypropylene (EPP) and it has proven to be
extraordinarily resistant to damage. The remainder of the wing is made of expanded
polystyrene which appears to be lighter but will dent permanently. The Zagi is extremely
maneuverable and can be flown fast or slowed down, with up elevator trim, to a gentle
glide. I have been amazed by its performance envelope and have flown it under power for up
to 13 minutes. On a windy day I thermaled it for flights greater than 16 minutes. A
neighbor with little R/C experience saw this airplane and had to give it a try. He has
been flying with me on a buddy box and has had no trouble controlling this airplane. I
would suggest that an experienced pilot should fly the plane initially to get the trim
right, but from that point on I think the Zagi would be a good step up from a glider-type
aircraft. The information in this article is a compilation of information derived from the
experiences of my neighbor and myself. Overall I have had more fun with this airplane that
any other I have owned!</p>
<p> </p>
</blockquote>
<p><big>Kit Review</big></p>
<blockquote>
<p>All components appeared to be of very good quality. The kit I bought had a uniform dent
in both wing center mating sections and the EPP (expanded polypropylene) leading edge
overlapped the edges of the EPS (expanded polystyrene) wing section. This condition
required some sanding but did not significantly affect the build time.</p>
<p>The content of the kit as well as additional tools and materials required are listed
below:</p>
<p>The complete kit comes with the following:</p>
<div align="center"><center><table BORDER="1" CELLSPACING="1" CELLPADDING="7" WIDTH="80%" bgcolor="#E6E6E6">
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Two composite foam wing halves (EPP leading edge and EPS wing panels) in their beds</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Speed 400 Motor</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Two Winglets made of Corroplast (corrugated plastic)</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>FAI 20 speed controller</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Two pre cut balsa elevons</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Battery pack ( Sanyo, 7 cell, 500N)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Mylar hinge tape</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>1 role of Blue 2.2 mil color poly tape (packing tape)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>2 threaded push rods, clevises, nylon control horns with screws, and adhesive backed
Velcro</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Vacuum formed motor mounting tray and canopy</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>1 loose male Deans Ultra plug (Speed Controller Connector)</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>2 wire ties to secure motor</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>1 male Deans Ultra plug terminated to apr. 5" wires (Charging Interface Harness )</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>1 Propeller</li>
</ul>
</td>
</tr>
</table>
</center></div><p> </p>
<p>Additional tools, material, and components required completing the plane:</p>
<div align="center"><center><table BORDER="1" CELLSPACING="1" CELLPADDING="7" WIDTH="80%" bgcolor="#E8E8E8">
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Soldering iron</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Rounded pencil or ball point pen</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>90 Degree square</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Epoxy and or Aliphatic Resin (Wood Glue)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>3M#77 spray adhesive or comparable (Make sure it does not attack foam)</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>1 additional role of 3 mil packing tape (contrasting color), or 2 rolls of contrasting
colored covering material</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Transmitter / Receiver</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>2 Servos (Light servos may not be the best option)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Mixer (If radio does not perform the mixing function)</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Assorted sandpaper/sanding block (Fine drywall sanding mesh is best on the foam parts)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>1 role ¾" wide filament reinforces strapping tape</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Paint for balsa elevons (the lighter the better)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Hobby knife, scissors, screwdriver, and optional Dremel tool</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Cling wrap or waxed paper</li>
</ul>
</td>
</tr>
</table>
</center></div><p> </p>
<p><strong>Construction:</strong></p>
<blockquote>
<p>Building this kit consisted of four new experiences for me: my fist flying wing, my
first foam plane, my first speed 400 plane, and my first packing tape covering job. I
learned a lot and had a lot of fun building the plane. The manual provided with the kit
was well written and sufficient for construction of the airplane. The kit also included a
very clear and concise insert showing some modifications to the instructions. Although
some of the materials and processes vary from balsa construction, I see no reason why a
builder with minimal experience could not build this plane and fly it successfully.
Through my experiences and experimentation I can testify to the fact that even if the Zagi
is not perfectly built, it will fly just fine. </p>
<p ALIGN="CENTER"><a href="/articles/ezonemag/1999/sep/zagi/zagtable1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagtable1_small.jpg" alt="zagtable1.jpg (42383 bytes)" WIDTH="157" HEIGHT="100"></a> <a href="/articles/ezonemag/1999/sep/zagi/zagtable2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagtable2_small.jpg" alt="zagtable2.jpg (35223 bytes)" WIDTH="157" HEIGHT="100"></a></p>
<p><strong>Vacuum molded Component Preparation</strong> – The battery tray/motor
mount and the cowling are formed from thermal set plastic. Both components require
trimming and the manual is specific and helpful in this regard. You may want to pierce the
holes for the motor tie wrap hold down and the ESC lead exit. Both my neighbor and I had
to rout the ESC through the rib separating the battery section from the motor mount
section of the battery tray.</p>
<p><strong>Foam Preparation</strong> - When cutting EPP with a hot wire the material tends
to melt and form stringy nodules. The Zagi-400 wing has an EPP leading edge so this
material has to be cleaned off before construction of the wing. The instruction manual is
very clear about this step. I initially did not do a good job of this but later found that
by lightly rubbing the surfaces with fine drywall sanding mesh the material would loosen
and I could pick the pieces off the foam with my fingers. In my kit the EPP leading edge
overlapped the EPS wing section and I did not sand the EPP leading edge flush with the EPS
wing sections. I was not aware of the fact that fine drywall sanding mesh worked so well
and the sandpaper I used at the time had a minimal effect on the EPP foam. If I were to do
it again I would sand the two bonding surfaces flush using the fine drywall sanding mesh
before bonding. My neighbor built his plane after I had told him how to sand/shape the
foam with drywall mesh. He ended up with perfect joints all around.</p>
<p><strong>Wing Section Bonding</strong> – The wing is cut out of a slab of foam
material. The material above and below the airfoil is used to form beds that position the
wing halves ensuring alignment during bonding. The manual suggested taping or gluing the
beds together so I opted to implement both methods. I glued the bed halves together with
epoxy and used the tape to hold them together while the epoxy cured. </p>
<p>Warning; test and make sure the adhesive you use to bond the wing sections will not
melt the foam. An edge of the beds could be used to see if the material will attack the
EPS foam. My neighbor used "epoxy" and ended up melting away the foam in the
joining area.</p>
<p>Once the beds were joined together I laid cling wrap in the center sections so the wing
would not bond to the beds. The wing halves are bonded with epoxy and laid in the bottom
bed for alignment. I also taped the wing halves together and laid the top beds over the
wing. Once the wing was sandwiched between the beds I put weights on top of the sandwich
and waited for the epoxy to cure.</p>
<p><strong>Wing Assembly</strong> – After bonding I suggest cutting away the
appropriate trailing edge section per the manual. This cutout is not identified on the
foam itself but is well documented in the manual and associated amendments. The cutout is
necessary to allow for adequate propeller clearance. After bonding of the wing halves I
sprayed the entire wing with the 3M77 adhesive and let dry for 30 min. The wings were then
reinforced with ¾" wide fiber reinforced strapping tape. The manual is very clear
about the location of this reinforcement and I had no problems with this part of the
assembly. I was amazed by how such a thin and fragile piece of foam can produce such a
bulletproof airplane. I believe that much of the structural integrity is due to the
filament reinforced packing tape that is applied to the wing in place of spars and
structural edges.</p>
<p><strong>Wing Covering</strong> – The kit I bought came with one role of 3 mil
colored packing tape but you really need two contrasting colors to keep tack of the
Zagi-400 in flight. I had never used packing tape for covering before so I followed the
instructions in the manual. The instructions were not clear about removing the
covering/packing tape from a factory cutout on the top of the wing. This cutout is to
provide clearance for the vacuum formed battery tray. I did not catch this fact until a
neighbor pointed it out to me. Now I understand why the battery tray did not lay flat
against the wing. The finish was ok but it was far from what I am used to on my other
planes. During later experimentation I found that "Easy-Tex" from Clancy
Aviation worked extremely well. Easy-Tex is a low temperature iron on fabric with
exceptional shrinkage, contouring, and puncture properties. The adhesion of Easy-Tex to
the foam was as good or better than the packing tape. After initial flight I loved the
plane so much I stripped off the packing tape and re-covered with Easy-Tex. The plane came
out to the recommended 19oz.</p>
<p><strong>Wing Tip Installation</strong> – The wing tips are made from Corroplast
and there is minimal preparation for assembly. The manual suggests assembly with filament
reinforced tape. I had seen Zagis assembled this way and could not bring myself to follow
suite. I used epoxy to bond the wing tips to the wing and have had no problems even in my
most unconventional landings/crashes. Heed the warnings about adding a lot of extra weight
here because it does effect balance.</p>
<p><strong>Elevon Preparation</strong> – The elevon preparation and finishing data in
the manual is excellent and does not significantly vary from techniques used to build
balsa planes. I would stress that the ailerons should be as light as possible. Due to
balancing logistics I suggest applying the ailerons to the training edge, with the
supplied Mylar hinge tape, right after wing covering and wing tip installation.</p>
<p><strong>Motor Break-In</strong> – The manual does not mention motor break in at
all. I think this is the one area that the instructions are seriously incomplete. I broke
in the motor using two "D" cells running the motor in its proper configuration
(clockwise) with the positive lead from the battery going to the positive post on the
motor. Electric motor break-in is well-documented and further information and processes
are readily available on the web and in print. A good link for this information is Terry
Gamble’s "How To Break-In an 05 Can Motor @ <a href="http://ezonemag.com/articles/1996/motorbre.htm">http://ezonemag.com/articles/1996/motorbre.htm</a>
</p>
<p><strong>Servo Installation</strong> - The locations for the servos are well identified
on the wing. I found that if the servo pockets are cut out undersized (apr.
.040-.050") the servos will fit very snuggly. To do this I traced the servo on poster
board and cut out inside the outline. Using this template I traced along the cutout
section to produce a slightly smaller pocket. Using a Dremel tool with a router base the
pocket routing was accurate and clinical. The servos fit so snugly I have not even taped
them in place and have had no problems. The manual suggests using balsa shims if the servo
does not fit tight enough, but I can not imagine obtaining a better fit than what can be
achieve using the aforementioned process. Place the servos into the wing, fabricate the
elevon control rods, and install the control horns per the instructions. I highly
recommend waiting until all component placement is identified (after balancing) before
cutting slits in the wing for routing of the servo leads and antenna. DO NOT CUT OUT FOAM
FOR THE RECEIVER until the balance has been checked as specified in the Balancing section
of this article!</p>
<p><strong>Balancing</strong> - I highly recommend dry assembly (no bonding/taping) of all
components with the exception of the receiver. There is NOT a lot of room to move the
battery pack around so you will not have an opportunity to significantly change the
balance after final assembly. With the aforementioned components in place, a round shaft
(pencil etc) should be taped to the bottom of the wing perpendicular to the cord 8"
back from the nose of the wing. Move the receiver up and down the wing cord until balance
is achieved. Mark the desired receiver position and install per instructions excluding the
location information specified in the manual.</p>
<p><strong>Set-Up Verification</strong> – I would recommend verifying the
functionality of all electrical systems to ensure proper operation. This will help you
avoid taking things apart again to switch servo lead connections to the receiver etc.
Although the assembly and disassembly process is not extraordinarily difficult, it tends
to get frustrating. Both my neighbor and I had minor noise interference problems and used
the same radio equipment (JR FX6XX series transmitters with R600 receivers). The receiver
I used was battle proven and had been installed in many electric airplanes without any
noise problems. I was able to reduce and almost eliminate this problem by antenna
placement near the leading edge of the wing and using capacitors from the motor poles to
the motor case and a capacitor from pole to pole. I called the folks at Zagi and they
claimed that I was only the second person to report this problem, but they were generously
willing to assist me in the elimination of this problem.</p>
<p><strong>Final Button-up</strong> – Measure the depth of the hole in the propeller
hub and transfer this dimension to the motor shaft. Apply force to the hub until it is
seated all the way to the mark on the motor shaft. Believe me, if this procedure is not
adhered to there is a good chance the propeller will come of in flight. This happened to
me and I never did find the propeller. Luckily this happened in mid flight and nobody was
hurt. When all functionality is verified cut slits in the foam apr. ½" deep to
install the servo leads and antenna wire. Using a flat blade screwdriver press the servo
leads and antenna into the slots and cover then with additional covering. Apply the Velcro
to the batteries, ESC, and the battery tray. Pierce the hole in the motor mounting area
and tie wrap the motor in snugly. Tape the battery tray into position and fit check the
cowling. Once everything is in place and functioning properly, you are ready for a lot of
fun!</p>
<p> </p>
<p><strong>Settings/Launch - </strong>I would normally talk a lot about the preflight
control setting but they are well covered in the instruction manual. The fact of the
matter is; this plane is so crash-proof that even if the setting are not right you will
not be able to hurt this airplane during launch crashes. It is sufficient to say the more
the up elevon trim the easier recovery will be. Not enough up elevon trim will tend to
frustrate you until you correct the setting. The instruction manual suggests launching the
Zagi without power and applying throttle once in a gentile glide. This works great if you
get a good overhead launch. I found that I had approximately a 70% success rate of
launching using this method. Some had suggested adding grip indentation to the bottom of
the wing. I personally found another method of launching but I can not share it for
liability purposes. Remember do as I say and not as I do. This plane is very maneuverable
and only needs a little head of steam to react to the controls. My advice is to stay with
the controls until you either get stabilized or hit the ground. Just remember you will not
be able to hurt this airplane on a bad launch.</p>
<p><big> </big></p>
</blockquote>
<p><big>Lessons Learned:</big></p>
<blockquote>
<ul>
<li>Verify the bonding material used will not attack the foam. I have come across at least
one dime store brand of "epoxy" that will melt EPS foam. I used the same generic
label 15 minute epoxy I always used on balsa models with great success.</li>
<li>Sanding of the foam can be done with good results. I preferred the use of drywall
sanding mesh.</li>
<li>Using a Dremel tool and the router base, routing out pockets in foam is very consistent
and accurate.</li>
<li>Pockets cut out of foam accept and hold components very well if they are routed
undersize. I also found foam was forgiving, and even if there was some slop in the pocket
I was able to hold everything in place with balsa shins and tape.</li>
<li>Foam sealant from the hardware store or Wal-Mart can be used to re-fill areas attacked
by adhesives. It can be sanded to fit the original contours and routs as well as the
original foam (EPS). </li>
<li>East-Tex from Clancy aviation is a very good covering directly over foam (EPS and EPP).
Make sure the iron temperature is not high enough to melt the foam. I personally did not
experience the phenomena but I have seen its results.</li>
<li>Flying wings are not difficult to track in the air if the two sides (top and bottom) are
contrasting colors.</li>
<li>Foam airplanes can be light, strong, and a lot of fun.</li>
</ul>
</blockquote>
<p> </p>
<p><big>Flying :</big></p>
<blockquote>
<p>The Zagi is a blast to fly, and extremely maneuverable and agile. The climb out is
strong, and the plane tracks all the way to a stall in a very predictable manner. The
stall characteristics are gentle, predictable, and easily recoverable. I found that if I
got in trouble I could cut the throttle, pull up on the nose, and either recover or
minimize impact. The Zagi can get going fairly fast but when the throttle is cut and you
bring the nose up it slows to a crawl almost instantaneously. Given the rugged performance
of the airframe and its maneuverability, the Zagi tends to make you a fearless pilot. This
becomes all the more true after you have witnessed the punishment this plane can endure.
The Zagi is stable at all speeds, indestructible, agile, and can be flown fast or slow.
With up elevon trim it can be thermaled or trimmed out to scream through most elevon type
maneuvers. I have been able to mimic some rudder driven maneuvers, like a sloppy stall
turn, by controlling wing stall and momentum. Although not a true high performance plane,
the Zagi is a lot of fun and has become the most favored plane in my stable. </p>
</blockquote>
<p> </p>
<p ALIGN="CENTER"><a href="/articles/ezonemag/1999/sep/zagi/zagfly1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly1_small.jpg" WIDTH="133" HEIGHT="100"></a> <a href="/articles/ezonemag/1999/sep/zagi/zagfly2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly2_small.jpg" alt="zagfly2.jpg (8758 bytes)" WIDTH="133" HEIGHT="100"></a>
<a href="/articles/ezonemag/1999/sep/zagi/zagfly3.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly3_small.jpg" alt="zagfly3.jpg (12874 bytes)" WIDTH="133" HEIGHT="100"></a></p>
<p ALIGN="CENTER"><a href="/articles/ezonemag/1999/sep/zagi/zagfly4.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly4_small.jpg" alt="zagfly4.jpg (13869 bytes)" WIDTH="133" HEIGHT="100"></a> <a href="/articles/ezonemag/1999/sep/zagi/zagfly5.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly5_small.jpg" alt="zagfly5.jpg (16554 bytes)" WIDTH="133" HEIGHT="100"></a> <a href="/articles/ezonemag/1999/sep/zagi/zagfly6.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly6_small.jpg" alt="zagfly6.jpg (24895 bytes)" WIDTH="133" HEIGHT="100"></a></p>
<p> </p>
</blockquote>
<table border="1" cellpadding="4" cellspacing="0" width="80%" bgcolor="#D5EAFF">
<tr>
<td width="50%"><p align="center"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/RYcopy.jpg" alt="RYcopy.jpg (12626 bytes)" WIDTH="387" HEIGHT="154"></td>
<td width="50%"><strong>Specifications as listed:</strong><ul>
<li>Wing San = 48"</li>
<li>Wing Area = 3.33 sq. ft.</li>
<li>Airfoil = Zagi 999</li>
<li>Weight = 19oz (ZAGI1)</li>
<li>Wing Loading = 5.7oz/sq. ft.</li>
<li>Radio = Mixer (V-tail / Elevon)</li>
<li>Motor = Speed 400</li>
</ul>
</td>
</tr>
</table>
</center></div>
<p> </p>
<p><big>Introduction:</big></p>
<blockquote>
<p>I always thought that flying wings were the most efficient practical aircraft design,
but I never considered building such a craft for the following reasons:<ul>
<li>I thought that a flying wing would be difficult to track due the non-existent fuselage
and empenage profile.</li>
<li>I though the airframe was fairly bland and ugly in comparison to traditional aircraft.</li>
<li>I thought the stability and control would be limited.</li>
</ul>
<p>In my mind I would routinely discount a flying wing project until I read Steve
Horney’s column in the June issue of the E-Zone Internet magazine (<a HREF="http://www.ezonemag.com/articles/1999/jun/ctower/clt0699-a.htm">http://www.ezonemag.com/articles/1999/jun/ctower/clt0699-a.htm</a>).
In his column he posted e-mail correspondence from John A. Williams concerning
electrification of the Zagi flying wing. After reading the testimonials in the e-mail
correspondence I thought it might be worth a try. On a subsequent pilgrimage to the hobby
shop I bought the "Zagi-400 complete kit". It included all the components
necessary for a speed 400 electric power system. I figured that if I did not like the
plane I could at least use the speed 400 propulsion system in other models. As it turns
out I love this airplane. This is the most indestructible airplane I have ever flown. The
leading edge of the wing is made of expanded polypropylene (EPP) and it has proven to be
extraordinarily resistant to damage. The remainder of the wing is made of expanded
polystyrene which appears to be lighter but will dent permanently. The Zagi is extremely
maneuverable and can be flown fast or slowed down, with up elevator trim, to a gentle
glide. I have been amazed by its performance envelope and have flown it under power for up
to 13 minutes. On a windy day I thermaled it for flights greater than 16 minutes. A
neighbor with little R/C experience saw this airplane and had to give it a try. He has
been flying with me on a buddy box and has had no trouble controlling this airplane. I
would suggest that an experienced pilot should fly the plane initially to get the trim
right, but from that point on I think the Zagi would be a good step up from a glider-type
aircraft. The information in this article is a compilation of information derived from the
experiences of my neighbor and myself. Overall I have had more fun with this airplane that
any other I have owned!</p>
<p> </p>
</blockquote>
<p><big>Kit Review</big></p>
<blockquote>
<p>All components appeared to be of very good quality. The kit I bought had a uniform dent
in both wing center mating sections and the EPP (expanded polypropylene) leading edge
overlapped the edges of the EPS (expanded polystyrene) wing section. This condition
required some sanding but did not significantly affect the build time.</p>
<p>The content of the kit as well as additional tools and materials required are listed
below:</p>
<p>The complete kit comes with the following:</p>
<div align="center"><center><table BORDER="1" CELLSPACING="1" CELLPADDING="7" WIDTH="80%" bgcolor="#E6E6E6">
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Two composite foam wing halves (EPP leading edge and EPS wing panels) in their beds</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Speed 400 Motor</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Two Winglets made of Corroplast (corrugated plastic)</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>FAI 20 speed controller</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Two pre cut balsa elevons</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Battery pack ( Sanyo, 7 cell, 500N)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Mylar hinge tape</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>1 role of Blue 2.2 mil color poly tape (packing tape)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>2 threaded push rods, clevises, nylon control horns with screws, and adhesive backed
Velcro</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>Vacuum formed motor mounting tray and canopy</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>1 loose male Deans Ultra plug (Speed Controller Connector)</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>2 wire ties to secure motor</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>1 male Deans Ultra plug terminated to apr. 5" wires (Charging Interface Harness )</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="29"><ul>
<li>1 Propeller</li>
</ul>
</td>
</tr>
</table>
</center></div><p> </p>
<p>Additional tools, material, and components required completing the plane:</p>
<div align="center"><center><table BORDER="1" CELLSPACING="1" CELLPADDING="7" WIDTH="80%" bgcolor="#E8E8E8">
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Soldering iron</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Rounded pencil or ball point pen</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>90 Degree square</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Epoxy and or Aliphatic Resin (Wood Glue)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>3M#77 spray adhesive or comparable (Make sure it does not attack foam)</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>1 additional role of 3 mil packing tape (contrasting color), or 2 rolls of contrasting
colored covering material</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Transmitter / Receiver</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>2 Servos (Light servos may not be the best option)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Mixer (If radio does not perform the mixing function)</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Assorted sandpaper/sanding block (Fine drywall sanding mesh is best on the foam parts)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>1 role ¾" wide filament reinforces strapping tape</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Paint for balsa elevons (the lighter the better)</li>
</ul>
</td>
</tr>
<tr>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Hobby knife, scissors, screwdriver, and optional Dremel tool</li>
</ul>
</td>
<td WIDTH="50%" VALIGN="TOP" HEIGHT="30"><ul>
<li>Cling wrap or waxed paper</li>
</ul>
</td>
</tr>
</table>
</center></div><p> </p>
<p><strong>Construction:</strong></p>
<blockquote>
<p>Building this kit consisted of four new experiences for me: my fist flying wing, my
first foam plane, my first speed 400 plane, and my first packing tape covering job. I
learned a lot and had a lot of fun building the plane. The manual provided with the kit
was well written and sufficient for construction of the airplane. The kit also included a
very clear and concise insert showing some modifications to the instructions. Although
some of the materials and processes vary from balsa construction, I see no reason why a
builder with minimal experience could not build this plane and fly it successfully.
Through my experiences and experimentation I can testify to the fact that even if the Zagi
is not perfectly built, it will fly just fine. </p>
<p ALIGN="CENTER"><a href="/articles/ezonemag/1999/sep/zagi/zagtable1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagtable1_small.jpg" alt="zagtable1.jpg (42383 bytes)" WIDTH="157" HEIGHT="100"></a> <a href="/articles/ezonemag/1999/sep/zagi/zagtable2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagtable2_small.jpg" alt="zagtable2.jpg (35223 bytes)" WIDTH="157" HEIGHT="100"></a></p>
<p><strong>Vacuum molded Component Preparation</strong> – The battery tray/motor
mount and the cowling are formed from thermal set plastic. Both components require
trimming and the manual is specific and helpful in this regard. You may want to pierce the
holes for the motor tie wrap hold down and the ESC lead exit. Both my neighbor and I had
to rout the ESC through the rib separating the battery section from the motor mount
section of the battery tray.</p>
<p><strong>Foam Preparation</strong> - When cutting EPP with a hot wire the material tends
to melt and form stringy nodules. The Zagi-400 wing has an EPP leading edge so this
material has to be cleaned off before construction of the wing. The instruction manual is
very clear about this step. I initially did not do a good job of this but later found that
by lightly rubbing the surfaces with fine drywall sanding mesh the material would loosen
and I could pick the pieces off the foam with my fingers. In my kit the EPP leading edge
overlapped the EPS wing section and I did not sand the EPP leading edge flush with the EPS
wing sections. I was not aware of the fact that fine drywall sanding mesh worked so well
and the sandpaper I used at the time had a minimal effect on the EPP foam. If I were to do
it again I would sand the two bonding surfaces flush using the fine drywall sanding mesh
before bonding. My neighbor built his plane after I had told him how to sand/shape the
foam with drywall mesh. He ended up with perfect joints all around.</p>
<p><strong>Wing Section Bonding</strong> – The wing is cut out of a slab of foam
material. The material above and below the airfoil is used to form beds that position the
wing halves ensuring alignment during bonding. The manual suggested taping or gluing the
beds together so I opted to implement both methods. I glued the bed halves together with
epoxy and used the tape to hold them together while the epoxy cured. </p>
<p>Warning; test and make sure the adhesive you use to bond the wing sections will not
melt the foam. An edge of the beds could be used to see if the material will attack the
EPS foam. My neighbor used "epoxy" and ended up melting away the foam in the
joining area.</p>
<p>Once the beds were joined together I laid cling wrap in the center sections so the wing
would not bond to the beds. The wing halves are bonded with epoxy and laid in the bottom
bed for alignment. I also taped the wing halves together and laid the top beds over the
wing. Once the wing was sandwiched between the beds I put weights on top of the sandwich
and waited for the epoxy to cure.</p>
<p><strong>Wing Assembly</strong> – After bonding I suggest cutting away the
appropriate trailing edge section per the manual. This cutout is not identified on the
foam itself but is well documented in the manual and associated amendments. The cutout is
necessary to allow for adequate propeller clearance. After bonding of the wing halves I
sprayed the entire wing with the 3M77 adhesive and let dry for 30 min. The wings were then
reinforced with ¾" wide fiber reinforced strapping tape. The manual is very clear
about the location of this reinforcement and I had no problems with this part of the
assembly. I was amazed by how such a thin and fragile piece of foam can produce such a
bulletproof airplane. I believe that much of the structural integrity is due to the
filament reinforced packing tape that is applied to the wing in place of spars and
structural edges.</p>
<p><strong>Wing Covering</strong> – The kit I bought came with one role of 3 mil
colored packing tape but you really need two contrasting colors to keep tack of the
Zagi-400 in flight. I had never used packing tape for covering before so I followed the
instructions in the manual. The instructions were not clear about removing the
covering/packing tape from a factory cutout on the top of the wing. This cutout is to
provide clearance for the vacuum formed battery tray. I did not catch this fact until a
neighbor pointed it out to me. Now I understand why the battery tray did not lay flat
against the wing. The finish was ok but it was far from what I am used to on my other
planes. During later experimentation I found that "Easy-Tex" from Clancy
Aviation worked extremely well. Easy-Tex is a low temperature iron on fabric with
exceptional shrinkage, contouring, and puncture properties. The adhesion of Easy-Tex to
the foam was as good or better than the packing tape. After initial flight I loved the
plane so much I stripped off the packing tape and re-covered with Easy-Tex. The plane came
out to the recommended 19oz.</p>
<p><strong>Wing Tip Installation</strong> – The wing tips are made from Corroplast
and there is minimal preparation for assembly. The manual suggests assembly with filament
reinforced tape. I had seen Zagis assembled this way and could not bring myself to follow
suite. I used epoxy to bond the wing tips to the wing and have had no problems even in my
most unconventional landings/crashes. Heed the warnings about adding a lot of extra weight
here because it does effect balance.</p>
<p><strong>Elevon Preparation</strong> – The elevon preparation and finishing data in
the manual is excellent and does not significantly vary from techniques used to build
balsa planes. I would stress that the ailerons should be as light as possible. Due to
balancing logistics I suggest applying the ailerons to the training edge, with the
supplied Mylar hinge tape, right after wing covering and wing tip installation.</p>
<p><strong>Motor Break-In</strong> – The manual does not mention motor break in at
all. I think this is the one area that the instructions are seriously incomplete. I broke
in the motor using two "D" cells running the motor in its proper configuration
(clockwise) with the positive lead from the battery going to the positive post on the
motor. Electric motor break-in is well-documented and further information and processes
are readily available on the web and in print. A good link for this information is Terry
Gamble’s "How To Break-In an 05 Can Motor @ <a href="http://ezonemag.com/articles/1996/motorbre.htm">http://ezonemag.com/articles/1996/motorbre.htm</a>
</p>
<p><strong>Servo Installation</strong> - The locations for the servos are well identified
on the wing. I found that if the servo pockets are cut out undersized (apr.
.040-.050") the servos will fit very snuggly. To do this I traced the servo on poster
board and cut out inside the outline. Using this template I traced along the cutout
section to produce a slightly smaller pocket. Using a Dremel tool with a router base the
pocket routing was accurate and clinical. The servos fit so snugly I have not even taped
them in place and have had no problems. The manual suggests using balsa shims if the servo
does not fit tight enough, but I can not imagine obtaining a better fit than what can be
achieve using the aforementioned process. Place the servos into the wing, fabricate the
elevon control rods, and install the control horns per the instructions. I highly
recommend waiting until all component placement is identified (after balancing) before
cutting slits in the wing for routing of the servo leads and antenna. DO NOT CUT OUT FOAM
FOR THE RECEIVER until the balance has been checked as specified in the Balancing section
of this article!</p>
<p><strong>Balancing</strong> - I highly recommend dry assembly (no bonding/taping) of all
components with the exception of the receiver. There is NOT a lot of room to move the
battery pack around so you will not have an opportunity to significantly change the
balance after final assembly. With the aforementioned components in place, a round shaft
(pencil etc) should be taped to the bottom of the wing perpendicular to the cord 8"
back from the nose of the wing. Move the receiver up and down the wing cord until balance
is achieved. Mark the desired receiver position and install per instructions excluding the
location information specified in the manual.</p>
<p><strong>Set-Up Verification</strong> – I would recommend verifying the
functionality of all electrical systems to ensure proper operation. This will help you
avoid taking things apart again to switch servo lead connections to the receiver etc.
Although the assembly and disassembly process is not extraordinarily difficult, it tends
to get frustrating. Both my neighbor and I had minor noise interference problems and used
the same radio equipment (JR FX6XX series transmitters with R600 receivers). The receiver
I used was battle proven and had been installed in many electric airplanes without any
noise problems. I was able to reduce and almost eliminate this problem by antenna
placement near the leading edge of the wing and using capacitors from the motor poles to
the motor case and a capacitor from pole to pole. I called the folks at Zagi and they
claimed that I was only the second person to report this problem, but they were generously
willing to assist me in the elimination of this problem.</p>
<p><strong>Final Button-up</strong> – Measure the depth of the hole in the propeller
hub and transfer this dimension to the motor shaft. Apply force to the hub until it is
seated all the way to the mark on the motor shaft. Believe me, if this procedure is not
adhered to there is a good chance the propeller will come of in flight. This happened to
me and I never did find the propeller. Luckily this happened in mid flight and nobody was
hurt. When all functionality is verified cut slits in the foam apr. ½" deep to
install the servo leads and antenna wire. Using a flat blade screwdriver press the servo
leads and antenna into the slots and cover then with additional covering. Apply the Velcro
to the batteries, ESC, and the battery tray. Pierce the hole in the motor mounting area
and tie wrap the motor in snugly. Tape the battery tray into position and fit check the
cowling. Once everything is in place and functioning properly, you are ready for a lot of
fun!</p>
<p> </p>
<p><strong>Settings/Launch - </strong>I would normally talk a lot about the preflight
control setting but they are well covered in the instruction manual. The fact of the
matter is; this plane is so crash-proof that even if the setting are not right you will
not be able to hurt this airplane during launch crashes. It is sufficient to say the more
the up elevon trim the easier recovery will be. Not enough up elevon trim will tend to
frustrate you until you correct the setting. The instruction manual suggests launching the
Zagi without power and applying throttle once in a gentile glide. This works great if you
get a good overhead launch. I found that I had approximately a 70% success rate of
launching using this method. Some had suggested adding grip indentation to the bottom of
the wing. I personally found another method of launching but I can not share it for
liability purposes. Remember do as I say and not as I do. This plane is very maneuverable
and only needs a little head of steam to react to the controls. My advice is to stay with
the controls until you either get stabilized or hit the ground. Just remember you will not
be able to hurt this airplane on a bad launch.</p>
<p><big> </big></p>
</blockquote>
<p><big>Lessons Learned:</big></p>
<blockquote>
<ul>
<li>Verify the bonding material used will not attack the foam. I have come across at least
one dime store brand of "epoxy" that will melt EPS foam. I used the same generic
label 15 minute epoxy I always used on balsa models with great success.</li>
<li>Sanding of the foam can be done with good results. I preferred the use of drywall
sanding mesh.</li>
<li>Using a Dremel tool and the router base, routing out pockets in foam is very consistent
and accurate.</li>
<li>Pockets cut out of foam accept and hold components very well if they are routed
undersize. I also found foam was forgiving, and even if there was some slop in the pocket
I was able to hold everything in place with balsa shins and tape.</li>
<li>Foam sealant from the hardware store or Wal-Mart can be used to re-fill areas attacked
by adhesives. It can be sanded to fit the original contours and routs as well as the
original foam (EPS). </li>
<li>East-Tex from Clancy aviation is a very good covering directly over foam (EPS and EPP).
Make sure the iron temperature is not high enough to melt the foam. I personally did not
experience the phenomena but I have seen its results.</li>
<li>Flying wings are not difficult to track in the air if the two sides (top and bottom) are
contrasting colors.</li>
<li>Foam airplanes can be light, strong, and a lot of fun.</li>
</ul>
</blockquote>
<p> </p>
<p><big>Flying :</big></p>
<blockquote>
<p>The Zagi is a blast to fly, and extremely maneuverable and agile. The climb out is
strong, and the plane tracks all the way to a stall in a very predictable manner. The
stall characteristics are gentle, predictable, and easily recoverable. I found that if I
got in trouble I could cut the throttle, pull up on the nose, and either recover or
minimize impact. The Zagi can get going fairly fast but when the throttle is cut and you
bring the nose up it slows to a crawl almost instantaneously. Given the rugged performance
of the airframe and its maneuverability, the Zagi tends to make you a fearless pilot. This
becomes all the more true after you have witnessed the punishment this plane can endure.
The Zagi is stable at all speeds, indestructible, agile, and can be flown fast or slow.
With up elevon trim it can be thermaled or trimmed out to scream through most elevon type
maneuvers. I have been able to mimic some rudder driven maneuvers, like a sloppy stall
turn, by controlling wing stall and momentum. Although not a true high performance plane,
the Zagi is a lot of fun and has become the most favored plane in my stable. </p>
</blockquote>
<p> </p>
<p ALIGN="CENTER"><a href="/articles/ezonemag/1999/sep/zagi/zagfly1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly1_small.jpg" WIDTH="133" HEIGHT="100"></a> <a href="/articles/ezonemag/1999/sep/zagi/zagfly2.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly2_small.jpg" alt="zagfly2.jpg (8758 bytes)" WIDTH="133" HEIGHT="100"></a>
<a href="/articles/ezonemag/1999/sep/zagi/zagfly3.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly3_small.jpg" alt="zagfly3.jpg (12874 bytes)" WIDTH="133" HEIGHT="100"></a></p>
<p ALIGN="CENTER"><a href="/articles/ezonemag/1999/sep/zagi/zagfly4.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly4_small.jpg" alt="zagfly4.jpg (13869 bytes)" WIDTH="133" HEIGHT="100"></a> <a href="/articles/ezonemag/1999/sep/zagi/zagfly5.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly5_small.jpg" alt="zagfly5.jpg (16554 bytes)" WIDTH="133" HEIGHT="100"></a> <a href="/articles/ezonemag/1999/sep/zagi/zagfly6.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/1999/sep/zagi/zagfly6_small.jpg" alt="zagfly6.jpg (24895 bytes)" WIDTH="133" HEIGHT="100"></a></p>
<p> </p>
</blockquote>