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Carl Goldberg Products Skylark 70 ARF Review

Those of us who were flying R/C airplanes about a quarter-century ago remember the famous Skylark 56 from Carl Goldberg. For many it was the natural progression from the ‘Trainer’ of the day, the Falcon 56 – which was a high winged semi-symmetrical airfoil. Some thought the Skylark was simply a Falcon 56 flipped upside down – oh those debates were lively. Well Carl Goldberg Models hasn’t forgotten those ‘good ole days’ and has released a 70” wingspan version of the Skylark era. Jerry Festa finds that things are just bigger these days!

Splash

Introduction

All of us like to fly in a style correlating with our mood: stick banging fast or graceful and gentle. If you are either of those or somewhere in between, the versatile Skylark 70 will be to your liking. I think one flight and you will be hooked!

Oh so sweet......
Oh so sweet......
Wingspan:70"
Wing Area:907 sq. in.
Recommended Weight:120-132 oz. 7.5-8.25 lbs
Flying Weight:8lbs. 6 oz. (8.375 lbs)
Length:60"
Wing Loading:21.27oz/sq. ft.
Servos:Standard
Transmitter:Futaba T9CAP
Receiver:Futaba R319DPS
Battery:JR 1100 mAh
Engine:OS Max 75 AX
Manufacturer:Carl Goldberg Products
Available From:distributed exclusively by Great Planes Distributors
Retail price:$219.99

Kit Contents

Kit Contains:

  • Two-Piece Wing
  • Lightweight wing tube
  • Ailerons/elevator/rudder hinged not glued
  • Hardware pack including formed landing gear, wheels, tank, nuts/bolts
  • Decals

Kit Requires:

  • 4 Channel radio with 5 servos
  • Engine/propeller of choice
  • 3” Spinner;
  • Epoxy, thick & thin CA
  • Foam protection for battery/receiver
  • 1.5mm Hex Driver

Assembly

First impressions were GOOD! All the components were covered with a very high quality film and applied in a professional manner, no additional covering was required. The instruction booklet even impressed me as it consisted of 18 pages of high glossy paper covered with clear, concise pictures and short simple instructions.

Wing

Each panel of the two-piece wing receives it own servo and one 6” extension. Ailerons were pre-hinged but not glued in place. The precut hinge slots were thin and were TIGHTLY pre-installed. Thin Zap was used on all hinges. The hinges seemed thicker and larger than others I’ve seen. The aileron servo pushrods were mislabeled as to their length in the instructions (Hint: use the shortest ones.)

The main landing gear was easily installed, and the three wheels weighed in at 3.5 oz. The entire set of wheel collars came with their metric set screws already installed – how’d you like to work in production, screwing those in all day long? Nice touch if I do say so myself.

Fuselage

Pushrods for the rudder and elevator had to be constructed of some dowel rod and two threaded rods. Those threaded rods were spring steel and metric in dimensions and were inserted into the fuselage before the stabilizers were glued in place. Two wing hold-down bolts resisted entrance into the pre-installed blind nuts when the wing was placed on the fuselage. It turned out some glue had worked its way into the threads during manufacturing, but by simply working the bolts slowly in and out, the threads were cleared up in a hurry. The wing/fuselage mating was spot-on.

Tail

The covering had to be removed from both stabilizers before they were epoxied in place. A “Hot Knife” from Hobbico was used so only the covering was cut and not the wood underneath the covering. The alignment of the stabilizers was excellent and no additional adjustments were necessary.

Radio Installation

The aileron servos were installed at the beginning of the assembly so all that remained was the installation of three servos in the preinstalled servo tray. All 5 servos were Futaba S9001 and fit into the prearranged slots perfectly. The battery was placed as far forward (and under the tank) as possible to assist in shifting the CG. Plenty of room for the 1100 mAh flat battery.

Engine Installation

“Back in the day…” we used to use what was called a “breakaway” engine mount: a plywood mount to which the engine was installed that was then secured to the hardwood engine mounting rails. The rationale behind this engineering was that (if?) when the plane crashed, the ‘tray’ would fracture and not the engine mounting rails or the firewall. This tray was simple to reproduce and frequently one could crash in the morning and by noon be flying again. Well the 21st Century has finally caught up with the 1970s and this ARF once again uses a plywood tray to mount the engine!

One minor problem developed as the blind nuts (AKA "T-Nuts) were being installed in the engine mount. Because of the width of the engine, a portion of the blind nut was not totally 'in' the wood. Some additional CA and epoxy was added to make up any space missing from the mount.

Our breakaway tray was a bit too tight a fit for the front of the fuselage, but light use of sandpaper solved it. A light coat of 30-Minute Z-Poxy was applied to the tray for fuel proofing. Being somewhat particular about spinner/fuselage gaps, my 1/16” gap (on the top of the fuse) decreased to less than zero (on the bottom of the fuse) so some sticky back sandpaper was applied to the back portion of the spinner and quickly removed enough wood to make me happy. One tank of 15% Omaga was run through before taking the plane to the flying field.

Completion

Decals were applied by first spraying the area with a soap/water mixture. This permitted the decals to slide around and to be positioned before a credit card was used to squeegee the excess liquid from under the decal.

A pilot is supplied. After cutting and painting, he was secured to the top of the black plastic ‘cockpit insert’. Then the clear canopy was glued to the fuselage. Neither the cockpit insert or canopy had any cut lines to guide the cutting process, but by using common sense (something I often lack - but not this time!), it all worked out nicely. RC 56 glue from Pacer was used to adhere those items to the fuselage.

To position the balance point to 3.5” back from the leading edge, approximately 4.1 oz. of lead shot was required to be added to the front of the fuel tank compartment. The flight battery was positioned under the tank. Total weight combined with the wing area makes the Skylark 70 a very lightly loaded plane at a little over 21 oz./sq. ft. After 3 weeks of test flying, the lead was removed, and no noticeable flight characteristics were noted.

Flying

The Basics Including Takeoff and Landing

The Skylark 70 drew a lot of attention in the pits as it was being assembled for its maiden flights. Many of the guys from the 'old days' commented on how it resembled Top Flight's Taurus or a RCM Kaos. Everyone predicted the flying qualities as 'smooth' and/or 'gentle'.

All starting was accomplished by using a McDaniels Glow Starter and a chicken stick! A quick adjustment of the needle valve produced a high speed of 10,400 RPM's and an idle of 2940. It sure ran quietly when at idle - but barked a loud 95 dB at the 9.9 feet. The 14-6 Master Airscrew prop decided it was ready to fly, so we taxied it out to the 'active'.

A quick acceleration produced a relatively long takeoff run as more and more up elevator was added before the Skylark 70 'jumped' into the air. Some down trim was needed for level flight at full throttle. No additional trim was needed.

The vibrant color scheme produced excellent contrast with the deep blue Arizona sky. Then the fun began! Loops were as large as we wanted, rolls were 'fine' (at low rates) and were 'much better' at high rates. 1/2 reverse Cuban 8's were solid on the upline after rolling but some down elevator was needed to keep the 45-degree up line.

Stall turns demonstrated solid rudder control and spins indicated we might be a bit nose heavy for some maneuvers. Stalls were next to impossible to execute as the plane just mushed ahead, slowly loosing altitude. Loops were very large and the plane didn’t need any correction to complete the loop at the same heading as the start! Inverted flight required a bit more down elevator than I expected, but flew very ‘solid’ in that mode.

Everyone has their own opinions on how well a plane flies – and there were a total of 4 different pilots who had their hands on the transmitter that first day. John, the ‘gentleman’ who takes my videos, LOVED the engine’s performance and was very satisfied with the way the plane handled, especially two wheel landings and scraping the heck out of my rudder as he ‘took off’ (in about 200 feet). Gary (a former B-52 pilot) liked the way the plane would come out of a Cuban 8 and as the plane rolled upright, there wasn’t any ‘tail wiggle’! Flying downwind with wide-open throttle produced a ‘rush’ he liked and Gary ranked it as an 8 out of 10. Ralph complained about having to fly hatless and with his camera strapped around his neck, but felt very comfortable flying the Skylark 70 at low rates. The rest of us preferred the recommended “High Rates”. So we three declared Ralph a ‘wootsie’.

Aerobatics/Special Flight Characteristics

Snap rolls were a waste of time, too slow and too gentle. Knife-edge wasn’t very good (lot of coupling), but 4-point rolls were nice – the plane stayed in an attitude until you changed it. This plane made all four of us look good, especially on landings – that ‘wide track’ main gear made ground handling a breeze. Ralph could even land this bird without bouncing!

To solve the takeoff condition (jumping off the runway), the nose gear was lowered as far as possible resulting in a near zero-zero angle between the plane and the runway. With that simple adjustment, landings remained the same but the takeoffs were much more gentle and graceful. This also gave a little more ground clearance for the prop. Ralph had nicked the prop while taxiing out of the startup area. I needed to remedy that situation IF I ever let him touch my plane again; he flew so high we all thought he was range checking the radio – by flying over the next county! After removing his telescope he reentered our atmosphere and continued to amaze all of us by not crashing – but he wasn’t worried – it “Isn’t MY airplane” he said.

On our 3rd or 4th flight the canopy flew off and was quickly recovered 100 yards from the pit area. Really it wasn’t that quickly found because while Ralph was sitting in the pits, I was doing the walking out in the desert. Ralph would point left, and I would walk left. Then he would point right and I would walk right. He kept this up for a couple of minutes until I quit paying attention to his ‘random’ direction pointing skills and just looked where I thought it was – and there it was. Thanks Ralph for the exercise (in 100+ degree temps). Ralph thinks I should lose some weight, comb what little hair I have and take a shower, but don’t tell him I know what he is thinking – O.K.?

The lack of a canopy didn’t stop any flying – and no difference if flight characteristics were noted. (Really they should supply the pilot with some sort of goggles, but I guess that’s his problem, not mine!) Some additional aileron movement was discussed between flights, but in all honesty, I liked the recommended high rates for both aileron and elevator. Our next ‘experiment’ was to switch to a 14-8 prop and see if we could cut down on the ‘supersonic tip speed’ that Gary likes so much. You have to remember Gary liked to fly supersonic while in the Air Force (He really was flying a B-52 but he thought it was supersonic because it went "so fast"). Another prop was purchased, balanced and mounted. Ralph finished the day of flying by doing touch and goes - and averaged 7.9 by our panel of expert judges (AKA the Peanut Gallery). Gee, I wish I could fly MY airplane once in a while guys...

A couple of weeks later Jim was our next test pilot. Jim comes from the 'good ole days' when Pattern flying meant flying planes that didn't have to cost a grand to be competitive. Jim loved the old Skylark 56 (he had 3-4 of 'em) and when he got his hands on this bird he indicated he was 'taken back in time'. In fact it took about a 1/2 hour after he landed just to get that grin off his face - HE LOVED THE SKYLARK 70! When asked what he thought of it (from 1 to 10) he gave it an 8.5 - 9.0! His only recommendation was to get the prop changed (it was a 14 x 8 MA at the time) to a 14x6 APC because he felt the 'up lines" where a bit short. I think he 'busted' our 400' ceiling a couple of times - and he wanted MORE???? Oh well pattern guys are a 'unique' breed :). Just don't let him know I richen up the needle valve to about 9100 RPM's as it was a very hot day.

Field Adjustments

By lowering the nose gear, there was a bit more ground clearance but in all honesty, you still needed a LOT of up elevator to rotate on takeoffs, so a larger nose wheel (Du-Bro 2.75") was exchanged for the supplied one (2.5"). That really solved the long takeoff runs that were followed by that 'jump' into the air. When we switched to a Master Airscrew 14-8 propeller and the dB reading dropped to a very respectable 89 dB! We also reduced the amount of Expo to zero on the transmitter (how did THAT get in there anyway as this was a new transmitter!!)? Ralph, you been mess'n with my transmitter again (ya gotta watch that guy all the time)? The additional weight was removed from the fuselage and the shifting of CG didn't have any significant effect on the flight performance.

Flight Video/Photo Gallery

Downloads

Is This For a Beginner?

This plane ‘might’ be a basic trainer IF the beginning student is working closely with an instructor on the buddy box. Twice in two days our club 'instructor' (AKA Destructor John) 'forgot' the club trainer and the Skylark 70 was called upon to do some very basic training! (see the video).

On the other hand, this is an excellent choice for the second plane for someone getting bored with a high winged trainer. This plane doesn't have one bad habit - other than it uses all the fuel you bring to the field!

Conclusion

After four weekends of flying this plane only one word can describe it (O.K. 3 words) 'It's a KEEPER'! I love the way it flies and adore it's color scheme against the blue Arizona sky (we did have a cloud once... but that's another story). Landings really stick because that "wide-trac" main gear gives this bird a very solid 'arrival'. Landings with the nose gear high in the air and as long as the runway are a lot of fun. This is one stable flying airplane in my opinion and apparently others as well. The OS Max .75 was an excellent choice for this bird. I even think John likes it too, but he won't admit it because I won't let him fly it wide open anymore.

As mentioned before, the Skylark 56 was frequently the ‘second’ kit built by the novice RC’er. Today I feel the same way as I did back then – this plane will make an excellent second plane for those among us who have conquered the high winged trainer and are looking for the ‘next’ plane. And this plane makes an excellent 'Sunday Flyer' for the sport pilot who wants to look better than he (or she) really is! The Skylark 70 assembles quickly, the parts fit and it flies very well – what are you waiting for?

Pluses:

  • Excellent covering and color scheme
  • Quick assembly
  • Complete hardware
  • Two-piece wing
  • Great flying - you look better than you are-especially on landings. One excellent flying plane!

Minuses:

  • Some hardware difficult to work with (Phillips head screws)
  • Blind nuts on breakaway engine mount too close to the side
  • Cockpit and canopy plastic lacked cut lines
  • Pilot figure very 'thin' plastic
Last edited by Angela H; Oct 09, 2007 at 10:56 PM..

Discussion

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Old Oct 15, 2007, 06:45 PM
Retired and Lovin' it!
United States, KY, Sturgis
Joined Jul 2007
2,559 Posts
If this plane flies at all like the original Skylark 56, then its definitely a sweet airplane. Goldberg made some really nice planes. And they weren't really difficult to build either.
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Old Oct 15, 2007, 08:39 PM
know it all
Miami, Fl
Joined Nov 2003
2,949 Posts
did they make a Skylark 70?.. would it be legal for vintage pattern?
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Old Oct 16, 2007, 10:58 PM
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tailskid2's Avatar
USA, AZ, Phoenix
Joined May 2003
3,369 Posts
One minor problem has developed....the nose gear mounting nuts came off - I shook the plane and heard this rattle; opened her up and four little nuts were floating around the fuse. Flew it anyway and the take-offs and touch and goes were straighter than ever! Go figure....anyway, add some thin CA to those nuts before you put in the tank...

Jerry
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Old Oct 18, 2007, 10:06 AM
small electrics r BIG FUN
Iowa
Joined Aug 2000
4,320 Posts
Nice review and nice looking airplane.

Has anyone converted the Skylark 70 to electric power ?
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Old Oct 18, 2007, 11:53 AM
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pda4you's Avatar
USA, TX, Trophy Club
Joined May 2002
14,519 Posts
Man this brings back MANY fond memories....



Mike
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Old Oct 18, 2007, 12:49 PM
know it all
Miami, Fl
Joined Nov 2003
2,949 Posts
Did the original Skylark have a span of 56" or 70"?, it was based on Falcon 56 with the wing on the bottom..they even had a twin option in the kit I believe. Legendary planes.
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Old Oct 18, 2007, 01:00 PM
know it all
Miami, Fl
Joined Nov 2003
2,949 Posts
the review plane used a 14*6 MA prop at 10,400 rpm.. that works out to 1350watts at the prop, assuming 80% effcient electric motor then you would need 1600 watts input to simulate the OS 75 engine. Probably an 8s lipo pack at 60amps.

Quote:
Originally Posted by Al P
Nice review and nice looking airplane.

Has anyone converted the Skylark 70 to electric power ?
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Old Nov 01, 2007, 11:18 AM
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Acetronics's Avatar
Le Treport, France
Joined Jun 2004
1,409 Posts
Quote:
Originally Posted by hermperez
Did the original Skylark have a span of 56" or 70"?, it was based on Falcon 56 with the wing on the bottom..they even had a twin option in the kit I believe. Legendary planes.

Hi,Herm,

I had a Skylark 56 with my KRAFT KP4B in ...1970.

It was a "free flight" converted to R/C ... as it was really easy to fly. I saw once a twin version ... but , at field, it's owner was just able to "spin" ... never got its engines in sync !!!

I bought a Skylark MK2 in 1980, but was really disappointed : Very Heavy weighted and an awful stab incidence !!! ( First flight was done with full forward left stick ...)
I finally crashed it at the end of a looping ( dynamic stall ...)

was not an easy plane to fly ... too heavy !!! and symmetric profile ... not so good !

Last but not least ... I'm just finishing the plans of a 76 " Skylark twin !!! of course an enlarged model of the MK2, for the better design ( still have both versions plans )
Bill Wike's Twinsync will be aboard ...

Alain
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Old Nov 01, 2007, 11:25 PM
Hey y'all, watch this
Bob_Richards's Avatar
Raleigh, NC
Joined Jan 2006
220 Posts
To answer a few questions, I will try to answer a few that I know.

The original Skylark was 56", and was basically a Falcon 56 with the wing on the bottom. The kit came with the parts (nacelles) to make it a twin. (I still have an original kit BTW). The airfoil was semi symmetrical. The tail was held on by rubber bands similar to the original Falcon. It was trike landing gear with a fixed (non steerable) nose gear. The recommended engine size was .09 to .19, and had around 6 inches of dihedral. I would have to look at the plans to be sure, but I don't think the plans even showed ailerons, it was a three channel plane.

The Mark II Skylark I believe had a fully symmetrical airfoil. Less dihedral, ailerons standard, and larger recommended engine size.

I talked to a person that used to kit the old Goldberg designs, he had a conversation with someone that used to work at Goldberg many years ago. The word was that Goldberg had a prototype for a large Skylark, the same size as the Senior Falcon. They never produced it, not sure why.

The Skylark that I flew many years ago ('73 - '76) was modified from the original design. The nose had to be widened for a K&B 40 to fit, I reduced the dihedral to 1", and added ailerons. It flew great, very little coupling, and was the first plane I ever did point rolls and slow rolls with. I crashed it and rebuilt it as a taildragger, and even used it as a glider tow plane. I probably had over 1000 flights on that plane.

It would be great if the Skylark 70 would be legal for vintage or SPA pattern. If someone can produce proof that a prototype did exist for a Senior Skylark way back when, then it could be argued that this plane would be legal.

Gosh, this does bring back memories. Kraft 5ch Sport Series radio with KPS-11 servos, K&B 40 with the rotating baffle exhaust and Perry carb, later I used a Proline single stick radio. Some of the best times flying that I've ever had.

Bob R.
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Old Nov 02, 2007, 11:27 AM
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skylarkmk1's Avatar
St Louis, MO Area
Joined Jan 2007
3 Posts
I most definately agree with Acetronics and Bob R, the original Skylark 56 (with semi-symetrical airfoil, rubber bands holding both the wing and tail on) flew much better than the Mk II. Back in 1973-75, I had just three channels (RET), no steerable nose wheel, Kraft Series 71 radio and at first an old Enya .35 (plain bearing), then up graded to a new Enya 45 (BB). Did the 2 wheel drag often enough I put a tail skid on. After flying it so much, I was able to win a few club "fun fly" contests against full house planes, I finally retired it, the front end was oil soaked and getting a bit soft.

When I built the MK II, construction was similar but that was were the similarities ended. I still had the original (MK I -see my name) at the time and checked the incidence and every thing against it. Symetrical airfoil (a bad move in my opinion), dihedral was much less (original did have 6" under one wing tip), bolt on wing, fixed tail (glued on), ailerons, steerable nose wheel were installed with the same radio and engine. The MK II was heavier, flew faster, would not slow down well and just was not as much fun to fly so it sits in the rafters today. I have had other planes that were much better flyers and more fun than the MK II; 2 Top Flite Top Dawgs, an "EL Camino" (Kaos look alike), "Hoss Fly", "Jr Falcons" and others, but none are remembered as foundly as the original Skylark 56.

The AMA Plans service has both plans, original G-21 and the MK II (G-21 II) available.
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Old Dec 02, 2007, 01:09 AM
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USA, AZ, Phoenix
Joined May 2003
3,369 Posts
Still pounding those landings and the landing gear is as solid as the day it was assemblied! Silly plane even came in second place in our club's spot landing contest - and believe me, it was all plane, not pilot!
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Old Apr 05, 2010, 02:51 PM
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Joined Feb 2006
4 Posts
Senior Skylark or Skylark 70

I remember seeing a short article in one of the model magazines back in the late 60's or erly 70's that showed Carl Goldberg holding a Senior Skylark and it was stated in the article it would be available the next year- which never happened. I will look for the article and post it when I find it.
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Old Apr 08, 2010, 10:50 PM
I'm a pilot... 100 yrs to late
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USA, FL, Palm Harbor
Joined Jan 2005
3,460 Posts
RC Report did a review of this several months back... I recall it being an excellent product.
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Old Apr 17, 2010, 05:21 PM
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USA, AZ, Phoenix
Joined May 2003
3,369 Posts
Yep, Wayne Gladen and I agree with each other - this plane is ? (was) I winner - don't know why they discontinued it - pick one up if you get a chance, you WON'T regret it!
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