By: Gary Hethcoat
This review was originally published in Randy Mullins' "R/C Online" magazine.
I was looking for two things in my next project:
The "scale" part pretty much eliminated pattern planes, and I don't really like biplanes all that much, so I started looking at the scale competition aerobatic planes such as the Lasers and Extras. I really like the looks of the Lasers, but unfortunately could not find a suitable kit. The Lanier Laser kits look nice, but I'm a wood man myself. I don't like to build with so much plastic and foam.
The first decision was the engine. The Zenoah G-23 seemed a good choice, since it is not outrageously expensive and it's size would permit its use in a reasonably sized (and priced) plane. I looked at the Goldberg Extra 300 and Sukhoi because of their size and relatively reasonable price. With either it looked like I could put the basic plane together for around $500 less radio. I chose the Extra only because I prefer its looks over the Sukhoi.
The first thing I noticed was how heavy the G-23 is, over 3 pounds! I could see right away that I would need some serious ballast in the tail to balance the model. I began plans right away to install three servos (rudder, two elevator) and the receiver battery pack in the tail. My first weight tests indicated that this would still not be quite enough and a few ounces of dead weight would probably be required in the tail.
Upon
opening the Goldberg Extra 300 kit, I was generally pleased with what I found.
The parts were well packed and organized. I don't really like the use of
ABS parts and lite-ply fuselages, but I'm getting used to it and it seems
to be pretty much standard in the industry for new kits. I'm slowly warming
to lite-ply interlocking fuselages, they go together quickly and with a minimum
of fuss. On the minus side, they make it hard to do nice rounded corners,
resulting in a boxy look on the bottom of the fuse.
The wire landing gear with plywood laminations supplied with the kit is truly pathetic. I can't imagine it holding up for more than a few landings. This is one area where I think Goldberg should have just bitten the bullet and put the extra cost of aluminum gear into the kit.
I
ordered aluminum landing gear, fiberglass cowl and wheel pants from Fiberglass
Specialties. They look nice, but I'm not pleased with the use of gel-coat
for finishing. It is very brittle, and it is hard to even do the cutouts
without a lot of cracking and chipping. I'm told straight fiberglass parts
are available from Ohio R/C or Goldberg.
These
parts will probably need some epoxy/microballons finish work, but at least
the gel-coat would be avoided.
The
tail feathers went together very easily. I liked the sheeted framework
construction of the stab and fin. I've done this myself to replace slab tails
in other models. Per recommendation of a friend, I installed one set of hard
points on the leading edges of the fin and stabs so that support struts could
be installed. After hearing horror stories about Ultimate Bipes shedding
their tail feathers, I decided to just install these without waiting to see
if I needed them. I figured by that time
it
may be too late! One other thing, I would recommend at least installing gussets
and cross-bracing on the rudder and elevators, if not replacing them with
'slab' or frame-and-sheeting units like the fin and stab. The rudder on mine
shattered the first time the plane flipped over on landing (I hit a rut :-)
The
wing is next. The wing design and construction is quite good. The wing dihedral
(very little) and washout (none) is set using cut-out lite ply support pieces
for the root and tips. These work OK, but the whole setup is hard to adjust
and very fragile. The wing ribs have built-in support pieces that rest on
the building board. I found these to be very fragile and difficult to pin
to the building board without destroying them. I would have preferred a trailing
edge prop-up strip, although I understand these are harder to manufacture
because of the taper involved.
I did have some parts problems with the kit. I was soon disappointed to find out that the wrong trailing edge pieces (tapered and notched) had been included in the kit. The ones in the kit were too small in all dimensions and the notches were too close together by a wide margin.
Because of the taper and the notches, these parts are very difficult to make by hand, but facing a 2 week delay to get parts from Goldberg, I had no other choice. It probably took me an extra 2 hours work to make these pieces myself. I also noted several places in the assembly manual where parts were misidentified. This was usually a case where one out of three dimensions given in the manual were incorrect.
I sent a letter to Goldberg telling them about the problems with the TE pieces and the manual. I offered to send them a list of the mistakes I found in the manual. They replied with a very nice letter apologizing for the mistakes, but did not take me up on my offer to send a list of mistakes in the manual. They didn't say why and I didn't ask.
Next
came the fuse. It went together very quickly and the finished structure is
very light. I did a bit of beefing up forward of the CG because of the large
heavy engine I planned to install. This mainly took the form of some triangle
stock added here and there to add extra strength. Some of the formers were
a bit flimsy, so I doubled them or added triangle stock until they stiffened
up.
If
you build such a fuse, save all of the knockouts,
as they often come in handy later on. They make great hatches if you decide
you need access to some part of the fuse later on. They also can be simply
glued in for strengthening areas where gear will be stored, such as around
the CG where radio gear (and in my case fuel tanks) will be stored. I also
glued the knockouts back in the tail where I installed plywood rails for
the servos. I've also found it is good to have hatch access in the tail for
adding weight internally and resolving any tailwheel problems, so I hatched
one side of the tail knockouts. I also added a hardwood block inside to give
the tailwheel screws something to bite into. I'm using the new Sullivan tailwheel
assembly which attaches with screws and has a coiled spring strut and spring
loaded (servo saving) rudder attachment. I like the design of this unit very
much. It is completely serviceable.
I'm using a total of six servos, one for each aileron and one for each elevator half. This is the first plane I've built where each surface is driven independently by a separate servo. In many ways it simplifies the installation, and there certainly isn't much slop in the linkages! Also, from a recommendation, I put 2-56 nuts with Locktite on the pushrods to lock the clevises in place and eliminate slop in the linkage. Also for eliminating slop, a guy at the field recommended using a piece of wire pushrod that has been cut with wire cutters as a drill to open up the holes in the servo horn. That way you get a perfect fit with no slop or play. After these mods the only play in the linkage is in the servo itself, which is very little.
I'm driving each aileron on a separate channel (permitting flaperons and other mixing possibilities) and the elevator servos on the same channel using a Y connector. Having had bad experiences with Futaba connectors in the past and facing the cost of $50 or so just for extension cords, I decided to convert entirely over to Dean's connectors for this model. I used computer ribbon cable torn into three strand ribbons for extension cords. I can make these as long as I want, and they cost about $1.50 as opposed to $6-$8 for the Futaba variety. When soldered properly, the Dean's connectors are much more robust than Futabas, which are just stamped onto the wires. Also, the Dean's connectors are serviceable. They can be taken apart and cleaned, etc. Try them if you haven't already. Tower has them in bulk (2 dozen) for about $1 each.
After much fiddling and cursing with various plane-mounted radio charging jacks, I've switched over to a 3/32" phono plug for this model. They are cheap (2 for $1.59 at Radio Shack) and they are easier to use than the commercially available plugs, most of which make it difficult to plug in the charger or ESV. If you're concerned about dirt getting in, just put a dummy plug in when you're not using it.
After adding a simple kill switch for the engine, the electrical setup was complete and it was time for final assembly and balancing.
Not really liking any of the color schemes I had seen for the Extra 300, I turned to Scale Model Research for info. They have five photo packs for different Extra 300s, one of which sounded attractive and not too complicated, so I paid the $18 or so and received a package of about 24 snapshots of a red and white Extra 300 that was one of the first produced and had German registration. The pictures were comprehensive, covering all of the markings and even had cockpit shots. I scanned some of these into the computer and used them for drawing templates for the markings using AutoCAD (which I'm very impressed with, by the way).
I
used Monokote red and white for most of the plane. Monokote Red (Missile
Red) turned out to be difficult to match with paint. All of the off-the-shelf
"reds" I could find were not orange enough. I tried some Chevron "Perfect
Paint" that was supposed to match Monokote red, but it was far too orange.
Also, when it was thinned to a sprayable condition it was so translucent
that ten coats or more would have been necessary to cover. Needless to say
I was not impressed.
Next
was some Black Baron spray-can paint I ordered from Tower Hobbies. This stuff
was slightly too red, but closer than the Perfect Paint so I gave up and
used it. To complicate things further there was also some color variation
in the "red" monokote that I bought, one roll being noticeably more orange
than the rest. ARGHHH!
I think I'm going to do another glass cloth/resin/paint finish on my next scale model!
I've
talked to guys that say they have bought Zenoah engines that ran perfectly
out of the box, mine did not. To be fair, though, mine was not factory sealed
when I bought it, so it could have been altered after it left the factory.
The "instructions" (a two page fold-up) weren't much help, and even suggested
an incorrect starting point for the needle valves. (0 to 1/4 turn for the
high speed needle, Yeah, RIGHT! 1-1/4
turned out to be correct)
After
about a gallon of fuel and five sessions of engine running and flying, I
had it running nicely. My biggest impression: these engines like to be wet!
It seems impossible to flood them, and every problem I had was due to one
of the mixtures being too lean. The engine would slow down and sputter a
bit when too rich but it would not die. The low speed needle was the hardest
to adjust. If it is too lean the engine will hesitate or die when going from
idle to full throttle. Also, this behavior may not be displayed until the
engine gets hot, so a ground run of at least 30 seconds at full throttle
should be done before testing the transition. Likes: kill switch, cheap fuel,
reliable inverted running, no glow battery, less oil/fuel residue on model.
Dislikes: power to weight ratio far lower than for glow, nasty smell and
lower safety factor of gasoline, black oily residue on model--stains clothes.
In short - I like the engine very much, and if they are as reliable as they
say, I'm going to buy nothing else from now on.
Unfortunately
I started flying before I had the engine running properly, and my first six
flights or so were dead-stick landings. My first flight was disappointing
because the engine wasn't producing enough power and quit on a low-high
transition. Later flights were much better. Engine power was much improved
by getting rid of the extension tube and lawn mower muffler I added to the
JTEC muffler to cut down the noise. It's a bit loud now, but the added power
is worth it. It's significantly lighter now too.
I'm
very impressed with the flying qualities of this design. Even as overweight
as mine is (10.5 lb) it still handles well, with straight ahead and gentle
stalls. The plane will 'mush' the air amazingly at low speed considering
its wing loading. Inverted performance is super with just a tiny bit of down
elevator required for straight and level flight once the model is trimmed.
I put the recommended 2-1/2 degrees of right thrust into the model which
seems about right. The plane is the most maneuverable I've flown, it needs
very little sky for a turn. The speed so far is not heart-stopping, but that
is not what this plane is designed for. Vertical performance is satisfactory
so far but not unlimited. I'm told the ignition engines don't produce their
full power potential until at least 2-3 gallons of fuel have been run through.
My
overall recommendation: Go for it! If you like the looks of the Extra and
want a scale plane that will do any maneuver imaginable, this is the plane
for you. The kit has some problems, but overall it went together pretty well.
My recommendation on the Zenoah G-23 is the same. It seems to be a
great engine, if a bit heavy. I think I'm hooked on gasoline now!
I would not recommend the combination of the Extra and the G-23 together, however. See the Epilogue below.
It's been over a year now since I originally wrote this review. After about three months of flying the Extra I lost it due to pilot error. I started a spin with only about 150 feet of altitude. This was the first real spin I had attempted with the plane. I had also just installed an auxiliary fuel tank in it, adding another 20 oz. of fuel. The crash happened only a few minutes into the flight. Everything seemed OK until, after about two revolutions in the spin, I brought the sticks to neutral and the plane did not stop spinning. This is the first time this has happened to me and it caused me to panic, because I did not have much altitude left at that point. I froze for an instant and then watched it spin into the ground. The wing is repairable but the forward 2/3 of the fuse was completely destroyed. The engine was unscathed. :-) This was a hard crash to take given the time I had put in on the project and the preventable nature of the crash.
In hindsight I would change my recommendation a bit. I don't think that the G-23 is ultimately a good engine for the Extra. It is not powerful enough to give the sort of vertical performance needed for this type of plane. I did get some additional performance out of it in the 30 or so flights I made before crashing it, and I'm told the engine's performance will continue to improve. However I don't think that it would be sufficient even given some more improvement.
I still like the engine, though. So much that I searched high and low for something that *would* be a good choice for this engine. The ideal plane would probably have a short nose and a radial engine, to make it easier to balance and give you more space up front. However, I saw the Dynaflite 80" Spitfire and fell in love. It is supposed to build light and be relatively easy to fly. I love warbirds, and it looked like the G-23 would be suitable, so I went for it. See my review of it elsewhere on this site.
I will try to get permission from Scale Model Research to post a few pictures
of the full size Extra 300 that I based my model on.
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