Vintage RC Helicopters - Peter Christy

Peter Christy

Hi Joe,

Yes, I've been a Lark flyer since 1975. My wife bought me one for Xmas in 1974, and its still flying!

Tips: Ditch the floats! Larks tend to be marginal on power anyway, and the floats kill all the lift! I remember one hot summers day when the factory demo pilot couldn't get a .40 powered one airborne on floats, whilst my HB.20 powered one was flying fine!

Sweep the blades *forward* about an inch at the tips. If you don't, it will develop a violent porpoise oscillation when you throttle back for landing! The full-size Lockheed's had a similar problem, which is where we discovered the cure!

I only ever flew a 40 powered one once! It was the designer's (Peter Valentine) prototype fitted with a Webra speed 40, and no gyro! Having a Tiger by the tail barely describes the experience.......!!!

The tail rotor control is very powerful unless you use a gyro. The main cyclic controls are slightly slow by modern standards, though back in the day they were regarded as alarmingly quick...!

You need an engine with perfect throttling characteristics! No stammering or coughing or you'll be in trouble!

There is no cooling fan! Don't leave it in the hover too long in hot calm conditions or you will cook the engine! In winter, or with a slight breeze it isn't a problem!

Best of luck!   Pete

               
Please find attached some Lark pictures!  The Mk 1 is mostly flown by my son as a bit of light relief from his competition flying! A friend who owned a model shop took it in part exchange for something and passed it on to me - complete with an HB 25 - probably the best engine ever fitted to a Lark.
 
My own is the one with the Linnet cabin and Snoopy at the controls. When these pix were taken, it was fitted with a GSM 25, but I've gone back to a Super-Tigre in it now. In case you're wondering about the strange looking tranny I'm holding, its a home made 459MHz set....!
 
A couple of more tips I should have passed on....
 
The bolts that hold the boom to the fuselage and the tail rotor to the boom should either be replaced with Allen caps, or increased in size to 4BA. (Be careful enlarging the holes in the tail gear box as they are very close to the shaft!)
 
The original 6BA mild steel ones are prone to snapping due to vibration fatigue....!  Also, if yours have the tail blades made up with hardwood, as supplied in the early kits, DON'T use them! They generate a lot of vibration which aggravates the tendency of the bolts to snap!
 
The ideal tail blades are 4"x1"x1/8", sanded to a Clark Y type section, and reinforced at the roots with 1"x1/4"x1/32" ply both sides. The reinforcements should be tapered - like a thin triangle - to avoid stress points where the reinforcement ends. I usually soak the leading and trailing edges in cyano for added strength, and then cover them with lightweight Solar film.
 
I wouldn't recommend allowing the main blades to freely lead/lag. They are pretty light, and there is no weight in them as standard. The head speed is fairly low, and I doubt there is enough centrifugal force to keep them out! You *might* get away with it with the 40 powered version, but I wouldn't bank on it!
 
If you have a teetering head, lock it up! I drilled the holes for the rubber dampers through, tapped them to 4BA and inserted bolts. These are done up until the dampers are compressed so tight that the head can't budge! As noted above, the combination of lowish head speed and light blades doesn't provide enough centrifugal force for a teetering head to work properly. The controls get VERY wallowy if you have any significant teeter. The slop in the bearings provides quite enough!!! ;-)
 
Hope this helps!  Pete

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