Conference vmszoo::rc

A quick preliminary review of the GM Precision Products Thermal Charger.

You remember this plane when you see it because it is an electric
with a pusher configuration to protect the prop.

It has a V-Tail so the pusher prop don't blow the elevator off.

I just finished building mine but haven't flown it yet.

It came in at 39 oz with 2 of those being lead in the nose.

The wood quality was first rate.  Great wood.

The instructions are elaborate but not without error.
For instance if you only followed the directions you would
never cut a hole or slot to mount the canopy.  You would never
put the dowel in the wing.

I pretty much followed the directions and only made a few mods.
(1) I put carbon fiber on the bottom spar (probably not necessary).
(2) I lightened up the ruddervators (they were solid wood).
(3) I used radio V-tail coupling instead of the Dubro mechanical
    mixer (which was called for in the instructions but not included
	in the kit).
(4) I cut off all their Kyosho connectors and replaced with Sermos.

I took Tom Tenerozics's advise and did not glass the wing center section.
The instructions did not say to do this and Tom says it is overkill.
I tend to agree.  Even at 39 oz it weights 1.5 oz less than my Sagitta
which doesn't have a motor or motor battery.

I used 3 MRC micro servos (try finding control horns for those!).

First flight may be this weekend - I'm in no rush.  I was rushing
to make it to the Electric fly in the Cape this last weekend and
just missed.

So the summary is:

Great wood!

Bob Comings(sp) also just completed one so perhaps he can add his
review to this.

Bye          --+--
Kay R. Fisher  |
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39 ozs! Kay, I'm impressed. My Challenger came in at 47 oz, and I thought I
built it pretty light. How big is the wingspan on this thing? Are you sure you
can fly a plane this light?

Dave

    Kay, that 2 Oz is 5% of the weight of the plane!  Rip it out and move
    something forward to get it trimmed.  It *WILL* make a difference.

>    Kay, that 2 Oz is 5% of the weight of the plane!  Rip it out and move
>    something forward to get it trimmed.  It *WILL* make a difference.

Actually unlike a lot of planes this one has plans that show a CG range.
Naturally being a chicken I have it set at the front of the range.
I can later remove the lead and still be within range.

Does sound light doesn't it.  Maybe I better re-weight it in case I
dropped a decimal point.

Bye          --+--
Kay R. Fisher  |
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        Re:          <<< Note 1136.4 by K::FISHER "Stop and Smell the Balsa!" >>>

        Kay,
        
                Gliders are  the  exact opposite of power planes.  CG too
        far forward makes  the  plane porpoise and continually stall.  CG
        too far back forces  you to fly it all the time.  If its up to me
        I'll start with it too far back and move it forward.
        
                      _ 
                     / |
           _----____/==|
         /__====------- 
             |-          
            /              
           /               
         Hang in there!      
                           
             Anker           

>< Note 1136.0 by FLYING::COLLINS >
>                       -< Thermal Charger - kit review >-
...
>	As stated earlier, the roll/yaw controls are very sensitive.  When 
>banking the A/C, it's easy to overcontrol the bank and get onto sprialing 
>dive.  This is a disadvantage when trying to level the wings on final for
>landing.  All three of my "hard" landings were cause by the roll/yaw 
>sensitivity of the model.  Each of these landing caused the A/C to cartwheel 
>along the wing tips.  Surprisingly, the wing has suffered NO DAMAGE!.  The wing 
>is definitely well designed and well built.  

I flew my Thermal Charger for the first time yesterday.  Since I had to send
my charger back to tower I only had one battery charge to use up.  I used
up most of that range testing.  I was paranoid that when the motor was
on I would get noise interference - it didn't happen.  But when range testing
about the point where you might expect to see a glitch (with the antenna down)
I lost motor control.  That is it would never come on.  I thought I blew
a fuse and but it turned out I had a bad Sermos connection.  Later I cut the
connector off and threw it away and replaced with a new one.

Anyway here I was at the field and the motor wouldn't run so I figured I
would hand launch and trim a bit.  First launch was OK but needed a lot
up up elevator trim.  OK - added sum and next launch was better but still
needed up elevator trim.  Now I'm near the end of the field so I get lazy
and figure I can throw it down wind as long as I wait for the breeze to let
up and throw nice and hard.  It did and I did and it stalled and cart wheeled
in.  Like bob - the wing came thru without a problem - but it broke up
the front of the fuselage.  So I went home for repair.  Sometimes I'm such
a dummy I can't believe myself.  So I fixed the fuse (need to re-paint tonight.
Then I'm back at the field just at sunset.  Range test again and launch.
Not much climb - but I'm still using the factory prop that Bob Collins already
advised me to replace and the battery hasn't been charged in a week.

Kinda normal flight (about 1 - 2 minutes of motor run) and absolutely no
lift at sunset as it gets cold.  Didn't get much of a chance to even get
good trimming.  Cut the motor power early as I saw (and heard - it's really
loud!) it sagging and after a near landing powered up and went around one
more time - no climb (not enough power) just level flight.  Perfect
landing in modestly long (about 4-6 inches) grass and cut up the MonoKote
on one of the V-Tails.

Sure am getting to appreciate T-Tails on gliders and electrics that don't 
have landing gears.

Sure seems like all Bob's suggestions for beefing up the Charger really
hit the mark.  Mine was completed about the same weekend as his so I couldn't
put all his suggestions in but if your just starting one I second his
suggestions.  The wing is very strong.

I forgot to mention that one other mod I made was I couldn't just
thread the thin plywood for the wing hold down screw - and I grafted
some hardwood on to the plywood so that my threads were longer.

One thing nice about the Thermal Charger - it has a unique and distinctive
shape - it would be very hard to become disoriented with this plane.

It looks so much like a flying boat that it is hard to imagine it up side down.

Bye          --+--
Kay R. Fisher  |
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You hand launched it down wind? A  heavy electric, no less??!!!  Tsk, tsk.
Weren't you in on the glider discussion?

>< Note 1136.7 by IGUANO::WALTER >
>                       -< Down wind hand launch? Hmmmm. >-
>
>You hand launched it down wind? A  heavy electric, no less??!!!  Tsk, tsk.
>Weren't you in on the glider discussion?

Add with the motor off.  As I'm walking over to the parts I'm mumbling
"I don't believe how stupid I am!" and kicking the ground.

Well - anyway I didn't throw my transmitter :-)

I was hoping to bring it to the DECRCM meeting for show and tell
but now our leader (Eric are you listening) doesn't think we can have a 
successful meeting without them making a lot of hoopla with video tapes 
and censoring Al Ryder from talking about the notes file :-)

Bye          --+--
Kay R. Fisher  |
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I put 4 or 5 more flights on the Charger this weekend.  

It was about 25 degrees out and at times a good breeze.
I was trying to fly out of a little clearing amongst tall
trees on all 4 sides just behind our church.  They were
making Christmas wreaths so between flights I would help
(and warm up while the battery recharged).

The first flight was the longest flight - about 8.5 minutes.
Subsequent flights were shorter because the sun quit shinning
and I lost thermal activity.

The first flight was also on the stock 6x2.5 prop.  The second
was on a 6x3 prop and the remaining flights were on a 6x4 prop.
Each prop had a better climb but a shorter run.  The 6x2.5 would
run about 4 minutes.  The 6x4 about 2.5 minutes.  The tricky
part was the first 60 seconds of motor run and trying to climb out
of the tree line.  

Now about V-tails in general.  I am not impressed.  Although on my first
flight I caught a couple of thermals and it circled OK I have some
general reservations about V-tails.

It seemed really squirrely in cross winds.  Picture this.  The prop
has tremendous blast over the tail - just between the V.  If you have
a cross wind the prop blast ends up on one of the ruddervators - not both.

Even without the motor running think about this.  When you pull up both
ruddervators rise.  The left V-tail wants to make the plane turn right
and the right V-tail wants to make the plane turn left.  With no wind
the forces cancel but with a little breeze one ruddervator becomes more
effective than the other.  So when you pull up it also turns in some
direction.  The reverse is also true.  The double reverse is also true.
That is if you turn left the left V-tail drops and the right V-tail rises.
Now normally they cancel.  But if there is a wind to push the air stream
across the tail one ruddervator becomes more effective than the other so
as you turn it tends to either rise (and stall) or dive.  I suspect that
this may be the reason that Bob Collins cart wheeled a few times.  

As you are attempting a max climb out you want to increase the angle of attack
till just before stall.  Then as the wind gusts effect the tail you get forced
into a stall anyway.  Not fun when your trying to climb over a tree line
and suddenly you loose control.  

I asked an experienced retired Air Force pilot about this and he said that
V-Tail Beech Bonanzas were known for being squirrely in a cross wind.

All my landings were at Mach 1.  Usually it would skid once and rise up a foot
or two then settle in again.  I wasn't actually bouncing on the belly.  That
would be too harsh.  But at fast speed when you skid on the belly it must have
changed the angle of attack and re-launched.  Kinda fun.

Anybody with experience on V-Tails want to shed some light on this matter.
Seems like every time I have a new plane it takes me quite a few flights before
I am comfortable with it.  For now this Thermal Charger is a hand full.

Bye          --+--
Kay R. Fisher  |
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Kay,

I've tried twice to enter this and had the net abort logical link so I'm writing
this at DCL level so as not to lose it a third time.

Back in '75, I familiarized and checked out in a Bonanza, then flew myself and
3-buddies to the Reno Air Races, logging something under 15-hours in the pro-
cess.  

In that amount of time, I became aware of the V-tail's eccentricities, namely 
its propensity to "hunt" in the yaw-axis, producing a slow, almost nauseating 
Dutch-roll which made compass-steering/navigation more of a chore than it needed
to be.

Also, the ship had a "slippery" feel, i.e. it did unexpected things in various 
conditions/situations/attitudes; nothing threatening but it prevented me from 
ever quite feeling I'd found the handle on the bird.  I never got comfortable 
with the Bonanza and determined that I'd go back to the Mooney the next time I 
had need of a fast 4-seater.

However, that time never came as my class-III medical expired shortly after the
Reno flight and I decided it'd become too overly complicated and expensive to
fly for recreation and let it expire, redoubling my R/C efforts which, regard-
less what some may think, is <FAR-AND-AWAY> a cheaper way to enjoy aviation.

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    Yes, my highly modified Electra is a V-tail.  I've noticed all these
    problems.  The best way to describe it is "Twitchy".  Never had any
    trouble landing though.  Just problems with precise control at altitude.
    

Oh yah - one more thing about this Charger.
When I was up about 200 feet I decided to dive for speed and try
a roll.  I got distracted and forgot about the roll when I heard the
sound.  It sounded just like the phoney engine sound in the song
by the "Three Guardsman" "Snoopy vs the Red Baron".  It was the sound
of the air stream forcing the prop to spin on my shutdown electric
leasure 05 motor.  Roaaaaaaaaaaaaarrrr.

Kinda neat but had the effect of speed breaks in the dive.  Well
on to a folding prop!

Bye          --+--
Kay R. Fisher  |
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>Kinda neat but had the effect of speed breaks in the dive.  Well
>on to a folding prop!


    Hah!  on a Pusher that's gonna look mighty peculiar!

    If you're just using motor on-off, go to a SPDT switch and use the extra
    pole as a motor brake.

    i'm looking into getting this kit for winter flying but i have two
    questions to ask before i do:
    
    1. i notice a lot of unsatisfied comment about the V-tail. can a T-tail
    or standard tail be used instead?
    2. how well does electric flying fit with winter???
    
    thanks for ALL you advice
    
    bruce

>                  <<< Note 1136.14 by DNEAST::MALCOLM_BRUC >>>
>                             -< 2 questions asked >-
>
>    i'm looking into getting this kit for winter flying but i have two
>    questions to ask before i do:
>    
>    1. i notice a lot of unsatisfied comment about the V-tail. can a T-tail
>    or standard tail be used instead?

Don't recall enough about the instructions to know how hard it would be
to do but I imagine it wouldn't be too difficult.

>    2. how well does electric flying fit with winter???

I kinda like the idea of electrics in the winter.
From my perspective it is the easiest way to get in those
"all season flyer" flights in really cold months.  Just
charge everything up and get it ready to launch then put 
it in the car and go the the field.  Take the plane out
turn it on and throw.  One flight down.

Remember diminished capacity of NiCads in the cold.  This won't
mean much on the motor battery since it draws plenty of current
and warms itself up.  But the Tx and Rx will have noticable
decreased capacity.  Usually not a factor because your fingers
will also wanna quit sooner.

One last thing regarding the thermal charger.  A couple of weeks
ago I saw my old thermal charger at auction - it had the center section
of the wing recovered and the V-Tail control surfaces recovered
but didn't look any the worse for wear.

Also I had a Devil of a time getting the trim to stay on the charger
which ultimately was one of the reasons I sold it.  But it turned out
that my Transmitter was defective and every time I told it to memorize
the trim settings it was giving one and a half clicks of down trim
to me.  Eventually  I found the problem and sent my radio to California
to get fixed.  Now I would like to try it again!

I just re-read this whole note string and am glad I did.  I was thinking
about a V-Tail HLG and now that I have refreshed my memory about V-Tails
I think I'd rather not.

One more "one last thing" about the Thermal Charger.  When it was first
introduced it seemed like a good way to make a prop survive an electric
plane.  Since then we have many many good folding props.  I would recommend
a more conventional electric sailplane with a gear reduction unit and
a folding prop.  The Thermal Charger was draggy and noisy.

Bye          --+--
Kay R. Fisher  |
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I'll second the noisy bit. Kay's was the only electric that I felt needed 
a muffler! 8^)

Seemed to be some resonance in the airframe/motor combination

    And the Charger has a really big cross section. Looks sort of like a
    sea-glider to my eyes. I think there are better electrics out there.
    Even the Electra or Eclipse would probably do fine for casual winter
    flying.
    
    Dave
    

    well, I took everyone's advise, went out and bought the Great Planes 
    Spectra, 1500 battery, the 905 charger and some foreign 7-3 folding
    prop for 550 electrics. I built this kit before so I know what to
    expect. It's a nice looking ship, I think I will go with yellow and
    black trim. 
    
    Thanks for all your help!!
    
    Bruce
    
    

>    expect. It's a nice looking ship, I think I will go with yellow and
>    black trim. 

Bruce, never make color decisions this close to Halloween :-)

Bye          --+--
Kay R. Fisher  |
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    how about red and white :-)
    
    Bruce
    

re:how about red and white :-)
    
Bruce,
you're talking to Kay.

One of those colors needs to be BLUE.

8^)

But more usually, both 8^)