It all started like this.
On the Vintage & Old Timers forum on RCGroups, some senior members run a 'build off' once in 6 months. There is a theme selected by participants, and everyone tries to build an appropriate model in the next 6 months. The prize for completing it is the participant's own model. So everyone who completes has his own new model as a prize! There's also a vote for the most popular build.
Those who fail to complete can participate in the next CAP (Complete A Project)

The theme for the second half of this year was EAR (Early Age Revisit). Participants were to build a model that they really desired in their early age, but never built for some reason or the other.

In the 1960s, I flew towline gliders, Cox or Mills powered free flights, and Frog/AM 1.5cc powered control line models. Later progressed to Enya .19, OS .20 powered Peacemakers...

Couldn't even imagine a 35 glow powered Nobler or Thunderbird!

But one of my friends had an OS Pet powered Control Line Graupner UltraStunter.
Another had a Control Line Mercury Marvin.

I knew back then that one day, sooner or later, I'd build these models.

The time has come.

So I downloaded the Mercury Marvin plan from OuterZone, and got it printed. The cost of printing it full size (Rs 70) was far more than I expected.

I'm converting it to RC and electric power.

I've cut out the ribs, and fabricated the leading edge and spars.

If anyone is interested, I'll post pics as my build proceeds...

Here's the plan...

Made a ply template for the ribs...

Deterioration in workmanship due to age is apparent...

Some improvement with the help of a sanding block...

Here is the original instructions booklet...
https://outerzone.co.uk/download_file.asp?planID=7458&FileType=Supp&Filename=Marvin_CL_Mercury_oz7458_instructions.pdf

Some observations about the control line model, while thinking of RC and electric power conversion.

1. Flew at 50mph. Or 75fps. On 40' lines., or a 250' circle. That is 3.3 secs per lap. Was it really so fast?
As far as I can recollect after 40 years, my OS20 powered Peacemaker couldn't have been under 5 sec on 50' lines.
2. 75fps on a 6" pitch prop means 150 rps, or 9000 rpm, or 10500rpm on 5" pitch. Probably ran at much higher rpm to drag the lines along
3. July 1956 Model Aircraft review (Sceptreflight.com) of the AM10 diesel shows 0.1 bhp (80w) at 10500rpm, and 1.2 bhp (100 w) at 14000.
4. Weighed 10-12oz all up

So it could do the stunt pattern, lines and all, at say 150 watts/lb...

Without the lines, perhaps 100w/lb would suffice

That AM10 weighed 3oz, so with tank and fuel, say 150gms

So an 80gm 2s 1000mah lipo, with a 30 gm motor plus Esc and 2-3 9gm servos may be enough?

I'm planning on aileron, elevator, throttle. No rudder.

What motor, prop, Esc, Lipo would be suitable for this RC version?

Interesting, very interesting

Assume 12 oz, about 350 gm

RCB's PRO C 2822 KV 1200 gives:
● Get 350gms Thrust
PROP – 8x4E
Lipo – 2cell 7.4V
ESC - 20 amp

My calculations show at 7000 RPM, 7.4 V, the thrust is 10.3 oz, absorbed power (by prop) is 35 W

Assuming 70% efficiency (prop + motor) current draw is ~ 7 A

So 1000 mah LiPo will last 1/7 X 60 = ~ 8.5 minutes at full power

If you use a 3S battery, more weight, but also more thrust! (if needed)

Mr Iyer,
Congratulations on such a great project. Marvin was a second step  at our NCC. Loved it. Converting it to electric RC would be terrific.

for airplanes around 12 ozs i have successfully used Hacker A20-22L, 20 amp esc and on a 3s lipo around 1000 mah. Just sharing. here are the details: http://www.flybrushless.com/motor/view/255.
A bit costly but mine has lasted 10 years with a couple nose dives crashes.

Anyways, wish you the best on your project. will watch this thread closely.

Some progress atlast...

Trailing Edge top sheet attached with PVA glue and taped down to drawing board edge to ensure no warps.

  Subscribed...

I guess old age brings its own problems .
Forgot to bevel the edge of the bottom TE sheeting.
So on gluing on the top TE sheet, I got a reflexed TE.

To correct that, painted the top TE with water and the bottom with dope.

Found that the dope was dark brown, having got impregnated with rust. Rusty dope I last used over 40 years ago...

But it cured the problem. At least on the starboard side (pic 1)
But not on the Port side (pic 2)

Crawling along at a snail's pace...
Added centre section webbing.
Then some unnecessary stuff.
Added perimeter to tips to ensure adequate contact patch for covering.
Then finding it wider than needed, chamfered the inner edge.
Utterly unnecessary.
Will add servo mount plates and centre section sheeting between dinner and bedtime. Hopefully.

Getting better...

What a joy it is to cut those corners with the Dremel...

Bottom open till servos stuck on with double sided tape...

Once you start the Dremel, it's not easy to stop...

Sad to cut the wing in two.
Wanted a bit of dihedral to avoid a droopy look.

As of now,
231 views on RCI,
1823 on RCG!

Coming along well!

Nice one sir.

Thanks folks, but it gets worse!

First trial with Doculam. Disaster.
Then did another tip in Chinese film, to check if I still remembered how.

Just use monokote!