9/10 -- Hirobo GPH-346 on Order
I just ordered a new helicopter to take the place of my trusty Nexus
30. I'll be installing an O.S. .46 FX-H engine and Hatori muffler in this machine.
I'll be controlling it with a JR 8103 radio, JR Z-PCM receiver, 1100 mah battery, HS-545
Hitec servos (HS-525 on tail), Arcamax HH gyro and BC-6 battery monitor.
9/17 -- It arrived!
UPS brought my new heli today and I wanted to share a few first impressions with you.
First, it came packaged very well - no damage at all. Many of the more complex assemblies
came pre-assembled. This thing has TONS of ball bearings and all metal parts are finished
to a very high surface quality. I noticed that it does not use a cone starter like my
Nexus, so it's off to the hobby shop to find the right kind of starter shaft.
I was disappointed to find a polypropylene canopy as I had real problems
with my Nexus canopy decals not sticking. I'm asking around to see if anyone else is
having similar problems with the GPH. A nice touch is that the windscreen was already cut
and fitted to the canopy.
The rotor blades look good - they're wood blades covered with a clear
shrink material. You also get a coupon with this heli for a crash kit. It's $50 and
includes blades, main shaft, feathering shaft, tail boom and a few minor parts - what a
Stay tuned as assembly will start soon...
9/19 -- Initial Assembly
I was going to break down assembly into many phases, but this kit is engineered so well
that assembly is taking place rapidly and will only require an 'Initial' and 'Final'
assembly section. A first-time builder may have questions, but if you've build one or two
helis, this is a piece of cake! The instructions are clearly written and follow the
hardware exactly. I had no parts shortages at all. The instructions are incorrect
according to a Hirobo dealer regarding the drive wire. The instructions show
"CAUTION: No. use grease." What that really means is USE GREASE. Just put a
light coating of grease on the drive wire prior to insertion into the wire carrier and
you'll be fine.
That Hatori muffler is really impressive! How in the world do they get
those beautiful welds???
Time to get that radio gear installed...
9/20 -- Final Assembly
The radio installation is complete and the machine is almost ready for
initial hover tests. Thanks to David email@example.com,
I was able to get around a nasty problem I was having with pushrod interference - turns
out that I had installed a bellcrank backward....duuuhhh!
I wet sanded the canopy with 220 paper to get a smoother surface for the
decals. The canopy has a rough surface which only gives you about 50% surface area for the
decals to adhere to (not enough!). By sanding, I got probably 90%. The decals are all cut
out (whew!) and ready for application. I attached the windscreen to the canopy without the
furnished screws. Instead, I used Pacer canopy adhesive. This just makes a cleaner
installation and prevents the windscreen from cracking at the screw holes (been there).
I'll be machining a starting shaft to use until I can get a Pegae system
I'm still very impressed with the quality of this machine.
Here are some photos of the mechanics of the
9/21 -- It's Finished!
Well, it was time to see if this thing would actually fly. It was 8:30 P.M. so I turned on
the outside flood lights to do a few hovering tests. Like all O.S. engines I've used, this
one started up immediately and idled down very smoothly. The first thing I noticed was how
quiet the Hatori muffler was! It has a very mellow sound that is pleasing to the ear. I
spooled it up and noticed that no matter how much I checked it out on the bench, I had the
rudder servo travel reversed. I changed that and spooled her up again. I got it light on
the skids, checked out the controls and brought it into a very low (inches) hover. It was
more sensitive than I was used to, so I cranked in some expo and it felt great. It being
dark I couldn't cut it loose, but I did stab the collective a couple of times and this
baby wants to climb!
I can tell already that I have a new favorite toy. Problem is, my little
Nexus looked kinda sad sitting in a corner of the shop wondering what it did wrong... :(
9/24 -- FFF Tests
I went out after work yesterday and did some fast forward flight
testing. Several points of interest....
1) For my skill level, the controls were a bit too sensitive. I had 40%
expo cranked in for both aileron and elevator, but it's needing less expo and less total
2) This thing really hauls with 30% nitro!!
3) I'm getting fuel 'churning' during hover at times - none at other
times. Mike Davis on the H-list thinks it's due to
carb settings (he's probably right).
4) The engine (OS .46 FXH) is running lean at hover - not sure what to do
about it at this time.
5) When I land, the engine takes forever to slow down - just like the
clutch is still engaged. Yet, when I kill the engine with trim, it stops immediately
indicating the clutch was not engaged. Mike thinks this is due to a lean setting.
6) This is a smooth flying, predictable machine with no apparent bad
habits in FFF.
7) So far, the decals are adhering well - see my method above.
9/27 -- What a Great Weekend
I flew about 8 tanks of fuel through the GPH this weekend. Lots of
'precision' slow flight. I'm working on accuracy and realism. Lots of nose-in hovering and
I'm getting the engine dialed in better now - no more fuel churning. Per
suggestions, I've richened the low end needle.
The decals were starting to lift just a little, so I took a small artist's
brush and wicked thin CA along all the decal edges - I'd highly recommend doing this prior
to flying to prevent oil from creeping under the decals.
I had one scare Sunday afternoon....I thought I'd try a loop, so I got her
all lined up (two mistakes high) and did a fairly nice one. Having built my confidence up
a bit, I thought I'd try another (without setting it up as well as the first one). Just as
it was inverted I lost perspective and the dang thing started falling like a rock! Not
sure how, but I finally snapped onto the correct perspective and recovered maybe 30 feel
This is one smooth-flying machine!
9/28 -- Fueling Modification
I got tired of having to pull the fuel line off the carb to fuel the
heli, and didn't want one of those expensive, leaky fueling valves, so I did something a
little different. I cut a round hole in the top of the fuel tank very carefully with an
Exacto knife somewhat smaller than fuel tubing, Then, I inserted the fuel line into the
hole and sealed with a little Pacer Canopy Glue. I put a tie wrap around the tubing an
inch from the tank to secure it and plugged the end of the tubing. No more fueling
Now, if only Hirobo had molded a second nipple in the top of the tank
(just like the one that is already there for the vent - I wouldn't have had to cut the
10/6 -- More 'Progress'
I burned about 6 tanks this afternoon after work and had
a BLAST! Here's what I tried and the results obtained...
1) I flipped the Auto switch at 20' a few times to
get the feel for it (sure wish it was in a better position on the JR 8103). I turned
up the gyro gain and got the tail under control in the process - no problem. I then
got up the nerve (finally) to try it at two feet. I'm sure it was me, but it came
down faster than I expected, bounced and came to rest. Didn't like this exercise.
2) I then shot quite a few power autos in 'Normal'
mode. Sure sounds funny when you pour the coals to it after idling down. This
does seem to help me understand what a real auto will be like.
3) Still don't like the way the engine overrevs when
performing a steep descent in idle-up 1. Yes, I have the idle mixture rich - it
slobbers pretty badly when coming up from an idle just prior to hover RPM. Yet hover
in idle-up 1 is fine. I know, I've complained about this before. Sorry.
4) I did some loops - successfully. They
actually looked pretty good. I did them in idle-up 2 with the throttle 'V' curve and
a bit of low collective stick when inverted.
5) Couldn't get up the nerve to do rolls - I just
read today that the machine should be set for 2 or 3 seconds rolls. I only get 1/4
roll in 1 second. Feels way too slow, yet I think my roll cyclic is almost at max.
10/8 -- Drilling the carburetor
Several OS .46 owners suggested drilling the carburetor per the drawing
below to get a richer midrange and leaner idle. The drawing is of the 'S' from the 'OS' on
the front of the carb. I'll try it this weekend. ..
10/8 -- Carb Mod Worked!
I couldn't wait for the weekend to try
the carb mod on my OS .46 FXH, so I did it tonight (after fighting the mixture problem
after work at the field). I now have a perfect idle and perfect midrange! I
haven't done any FFF with it yet - just hovered tonight in the back yard. WHAT A
10/9 -- Carb Mod Works in FFF Also
I just returned from the field and found
that the new carb mod works perfectly in FFF, hover and idle. Anyone out there with this
engine really should do this simple mod. If you don't like for some strange reason, just
JB Weld it shut.
10/11 -- Great Weekend
Two perfect days of flying. I met with an experienced local flier (Carl
Atherton) who helped me get the heli dialed in properly. I was having trouble getting the
sustained vertical performance out of it that I knew this machine is capable of. I was
only getting 8 degrees of high pitch - any more than that and the engine sagged. The carb
was about 6 clicks too rich. Also, the head speed was a bit low, preventing the engine
from getting into it's power band. All is well now - I'm getting 10 degrees with 15% nitro
and nice climb performance.
Carl is also a professional fiberglass r/c boat builder and has
volunteered to help me fabricate a fiberglass canopy for my GPH (thanks, Carl!). I'm going
to build the 'plug' and glass it. Carl will then fab the mold from the plug and we'll pop
out a shiny new glass canopy! I'll keep you posted on that process in case you want to
give it a try sometime.
10/12 -- Canopy Progress
Here's a shot of it so far...this could end up being a real challenge!!
10/16 -- DON'T DO IT!!!
After getting the 'plug' all smooth and nice, I started really checking
over the dimensions and found out that they was off quite a bit. It's just too difficult
trying to duplicate the real canopy with this foam block. My next step is to buy a
fiberglass canopy from Hobbies and Helis for $55 and see how it looks. I may then make a
mold off of it (or even my original GPH canopy), then make a few canopies from that mold.
10/17 -- My First Autorotations!
Well, I finally got up the nerve to try my first full-down auto. I
practiced a few from 3-4 feet and let them settle, then shot maybe a dozen power autos.
The wind conditions were right (about 10 mph) and I went for the real thing! Wow! What a
rush! I shot a total of probably 100 - ended up breaking my tail rotor blades at one point
and fabricated a few sets from tongue depressors. I couldn't tell ANY difference in flight
characteristics using the them over the original blades. I have now improved this process
by fiberglassing and balancing them - it only takes a few minutes to make them and I'll be
putting them on for my auto practice.
10/26 -- New Glass Canopy
I just received a Hobbies and Helies fiberglass canopy shown below...
It has a glass smooth gell coat, NO seams and light weight. I'll be using it (once
painted) until I make my own fiberglass mold from the stock GPH plastic canopy. Stay
10/30 -- Paint Job Finished
Here's how it turned out...
I don't know if the photo shows it, but this will be MUCH more visible in the sky then the
stock canopy. The fiberglass canopy also adds a lot to the overall quality look of the
I'm just now beginning to get started with inverted hovering (at 20,000
feet!). I'm starting to hold it for a few seconds at the top of loops. Yeah, that's no big
deal for some of you, but it's a BIG DEAL for me!!! I have my idle-up set for +10, -10 and
throttle in a 'V' curve which all seems to be working with the inverted attitude.
10/31 -- Just More Status
Well, that yellow canopy REALLY shows up in the sky!! No comparison with the stock canopy.
It's also a thousand times easier to clean - glass surface instead of the milk bottle
surface. You GPH guys really ought to give it a try!
Just more practice this weekend. More autos, more FFF, and a little more
inverted practice. I need to get my simulator back (loaned it to a friend) so I can
practice inverted with it first. I'm starting to get a better feel for rolls - they're
sure a lot easier to do downwind!
I now have about 25 hours on this machine and have had ZERO problems with
it to date. It's extremely reliable and EXTREMELY FUN!!
11/6 -- New Blades
I just tried some new fiberglass blades from Victor Meek firstname.lastname@example.org in Phoenix and they
are GREAT - especially for the price - they were only $33!!!! These blades weigh the same
as the stock wood blades and balanced perfectly right out of the box. They auto real well,
have no bad habits and have a nice appearance. All this at less than half the price of
other fiberglass blades!
I am spending more time practicing inverted flight - what a challenge!
11/15 -- Need More Cyclic
As I get more and more used to this terrific machine I'm finding that I want more cyclic
throw. Maybe I just need more cyclic response. I have a question out on the H-list for
help with this one. Maybe just lighter flybar paddles? The stock paddles are weighted with
two weights. Maybe just pull one or both? But which one? See the problem?
Anyway, when I get more info, I'll pass it along. What I'm looking for is
a faster roll rate. Right now, I'm getting a complete roll in about 2-3 seconds - I'd like
a roll per second.
I've flown this heli 40 hours to date.
11/17 -- Have More Cyclic
I removed both weights from my stock flybar paddles and now have the cyclic I was looking
for. I have 40% expo dialed in my transmitter and have a nice soft center, but it really
dances when you throw full stick.
I'm putting in a lot of practice on the CSM simulator doing inverted
flight. THIS AIN'T EASY!! I'm sure I'll get it one of these days, but it sure isn't coming
11/22 -- It's Squealing!
Yesterday, the GPH started squealing when it was idling - and only when idling. After a
lot of investigation and trial and error, it turned out to be the clutch/starter shaft
that passes up through the clutch bell housing. The top bearing (large one toward the
bottom of the bearing block) was not making a good connection with the bell housing. The
bearing race actually rides against a gear that has been turned down to fit the bearing -
not a great idea. Anyway, I cleaned it with Acetone and put some 5-minute epoxy on the
gear and reassembled it. So far, so good. I'll post my results as I continue to fly it. So
far, I have 40 hours on this heli.
I also put one of the flybar weights (the brass one) back in. It was a
little too sensitive with both weights removed. Much better now.
11/30 -- No More Squealing
Well, the 5-minute epoxy idea didn't work - no real surprise there. It started squealing
again after only four flights. Time for a permanent fix. I disassembled the clutch bell
and machined a steel sleeve to press over the turned down gear (see above). The bearing
now fits perfectly over the sleeve. I used red Loctite to keep the races from turning and
reassembled. So far, about 20 flights later, still no problem. I really believe it'll
never squeal again.
Also helped a friend test fly his GPH. Another perfect machine - can't
beat these things!
12/6 -- Auto Clutch Too Loose
This past weekend, I noticed that my tail rotor was almost stopping when doing autos. So,
I put some feelers out on the net and it sounded like a direct driven tail was the way to
go. I thought, "This'll be a piece of cake - just put JB Weld all around the auto
clutch to lock it up and I'll have a direct driven tail". Well, that gave me a direct
driven tail alright, but when it came time to auto, that also keeps the main clutch
engaged and the engine does not drop to idle, causing a BUNCH of drag on the whole driven
system - rotor speed goes to pot!! Anyway, off came the JB Weld and I'm back to trying to
find a way to tighten the auto clutch - shims?
12/11 -- My Baby Bites the Dust!
Well, it had to happen sooner or later....my GPH was flying
really sweetly this morning (as usual) and, all of a sudden, the tail started spinning
like crazy! I hit the hold switch but, at only about 20' of altitude, I didn't have
time to do a real auto. I ran out of collective way too soon and it did the funcky
chicken all over the ground. Looks like the pitch slider lever broke for some
unknown reason. I was not driving the linkage to the stops - no load other than
normal flight loads. Damage: landing gear, tail boom, flybar, boom supports,
pitch slider, drive wire, pitch arms, minor canopy damage. Surprisingly, fiberglass
blades ok, main shaft and feathering spindle ok.
The parts will be here tomorrow
morning. Of course, that's with about $40 shipping. :(
12/12 -- Back in the Air!
Thanks to Ron at Rick's Heli, I'm back in the air the next
day - total including shipping was $106. Not too bad. Flies just like before - no shakes,
rattles or rolls. Well, maybe a few rolls...and a few loops as well!
12/17 -- Stainless Steel Pitch Lever
So, anyway, I didn't ever want to crash due to the pitch
slider lever breaking again, so I made one out of stainless steel.
Yeah, it's overkill, but I had the material laying around and, believe me, this guy won't
12/21 -- Crashed Again
Well, this time, a steel ball unscrewed itself from the
pitch control arm on the rotor head. I was coming in for a landing, about 15 up when, all
of a sudden, a blade dropped pitch and smacked the boom - down she came, like a wounded
duck! The usual damage, blades, boom, drive wire, flybar, fin set. While I'm repairing it,
ALL metal-to-metal threads are being locked with RED Loctite. That same flying session,
two other screws on the factory assembled head came almost all the way out before being
12/25 -- Pitching Up in FFF
Right after the rebuild, I noticed almost violent pitching up in FFF. It was suggested
that it was the cordwise CG of the rotor bladed, lightened flybar paddles, flybar paddle
incidence, heli CG, etc. Turns out it was excessive positive collective pitch. After the
rebuild, I failed to check the pitch and had almost 15 degrees! Cranked it back down to 10
and all is well again.
12/27 -- Elevator Centering Problem
I was recently plagued with the elevator not centering
after flying around. I was constantly having to retrim elevator. We suspected the Hitec
servo was at fault until we changed it and the problem stayed. It was actually the
'Elevator Torque Lever Pivot' (part #403-235 on page 66 of the manual) slipping on the
shaft. The shaft NEEDS A FLAT ground on it for the set screw!!!! All GPH owners, do
yourself a favor and make this mod NOW! It could easily caused a crash. This is not an
isolated case as another, almost new, GPH at our field had the same problem.
12/29 -- Just Bought an X-Cell Graphite
No, I'm not selling my trusty GPH!! But check out the
details on the X-Cell purchase.
1/7 -- Tail Pitch Slider Upgrade
Now, I'm not a real big fan of upgrades just to upgrade. It
was recommended that the tail pitch slider be upgraded to prevent in-flight tail rotor
failure. Looking more closely at the stock slider, I could see why. The slider 'arms' are
quite thin. I gritted my teeth and bought the upgraded slider from Rick's Heli - $41. It's
excellent - all ball bearing, strong, anodized and very smooth. Here's a shot of it:
2/21 -- Almost Crashed It!!!
So, there I was about two mistakes trying to learn inverted forward flight (after quite a
few hours on the sim) when, all of a sudden, I lost orientation of the dang thing (big
surprise) and here it comes out of the sky like a shot duck - falling like a box of
rocks!!! I'm fighting it all the way down: left cyclic - NO! right cyclic,
full collective - NO, I'm inverted! Left rudder, NO! - well, you get the
picture. Anyway, just as it was about to completely destroy itself, I somehow
managed to get it back under control - problem was it started eating a tree!! It was
a fairly small tree, but a tree none the less. It was whacking leaves and branches,
but kept on ticking. Somehow I managed to keep it aloft, and bring it back to a
landing. The fiberglass blades (thanks, Vic!) held together somehow. Lots of
green streaks on them, as well as green streaks on the tail rotor blades! The blades
were busted at the tips, but held together long enough to get her home.
Guardian angels, guys!
5/8 -- Sold It
Well, after enjoying the GPH for eight months, I decided to sell it. I
sold it to a local guy who is in the early stages of hovering. It'll make him a great
machine. So, even though I kinda hate to see it go, I'll be able to continue watching it
It's been a great heli.