Johnson 35CS

This seems to be "Johnson Week", so I have a question about the only Johnson I own. (at least for now)
I haven't run this engine and I've had it for over 10 years. Just bolted it on the front of my Giant Stuntmaster (old Scientific profile).
Can I expect it to 4-2, or will I have to go "wet 2". ??
It has the red venturi restrictor, and the pressure fitting in the rear cover has been brazed closed. Good compression, and I plan to use 10% Nitro-25% all castor.
Help.
TIA
Bill <><

Bill: The CS stands for Combat Special! It wants to run pretty much balls out.

I have a Giant Stuntmaster (flew it in the Musciano Unlimited portion of the NVCL contest last September), and, believe me, a Fox 35 Stunt is plenty. Your plane is going to howl, if you insist on using the CS. In fact, you will have a Slow Combat ship, of sorts.

You could tone it down with head gaskets and venturi restriction, but you still have pretty agressive timing. But, if I still haven't talked you out of it, use a very low pitch prop on it, and hang on.

Thanks Currell,
I had a McCoy 35 on it which did pretty good, but I want to try out this Johnson. Think I will go with a 4 pitch to start out with!
Maybe only 5% nitro, too.
I have heard others talk about the early Fox CS running okay for stunt with extra head shims, etc., but don't know a thing about the Johnson!
Will let everyone know!
Bill <><

If it's a 4 pitch, it should be about an 18 diameter.

LOL!! Howard,
I don't think I can clear an 18" prop. Maybe and 11".
Thanks,
Bill <><

Maybe an 11-6. These things take a lot of prop. As Shholt said, we used 9-8s for combat.

You could sell the Johnson to an old combat flyer and use the money to buy a stunt engine.

Hi Howard,
Would a 11X6 be good, or less pitch if it's going to run that fast?
I would like to keep the laps above 4 sec. I've flown some fast combat ships and this one isn't for that, I hope.
Really asking the question, not trying to be cute.

Be glad to work out a swap for a Johnson "S" .
Bill <><

I suspect that the "Giant" Stuntmaster is no larger than some of the early combat airplanes we flew which were around 300 sq in, give or take about 20. With a Johnson on crankcase pressure and a 9X8 prop, the Omega would run about 100 mph. With the venturi restrictor, suction feed, and a 10X5 prop, this could be fun. The CS is a heavy devil (about 8 oz) so c.g. could be a problem.
Steve

Hi Steve,
Not sure of the wing area, it's a 42"-43" WS, and about a 9"-10" constant chord wing. A real barn door! Bigger (visually) than my Ringmaster.
Can't be much worse than a Circus Prince w/ 36X, missle mist, and 9X8 prop!
(of course I was only about 14 years old then)
Thanks,
Bill <><

>Hi Steve,
>Can't be much worse than a Circus Prince w/ 36X, missle
>mist, and 9X8 prop!
>(of course I was only about 14 years old then)
>Thanks,
>Bill <><

Bill,
I'm glad we weren't the only ones putting big, high power engines on small airplanes back then. We thought that going fast was the solution to combat. No, it won't be worse than that.

I've been seriously considering building a Flite Streak for a Fox Mark III or IV Combat Special, just for the fun of it.
Steve

Steve,
It was FUN!!
Go for it with the Streak, you will ge ta kick out of it, but I hope the youngster's reflexes come back.
The most "FUN" plane I ever had was a profile ZERO from MAN plans that had a 40" WS and about a 12" Fuse. It was for Combat/"sport" and a .19-.40. Used the same 36X with the restrictor removed, and a pressure tank in the wing. Even used a speed dolly to take off sometimes. Ohhhh...... was it fast! LOL!! Lost it when both lines broke and it hit the baseball field backstop. ;( Almost went through it!
Bill <><

Don't mess around with a Fox; use a Nelson. Don't skimp on the nitro.

Hi Bill, The Johnson cs is one powerhouse engine! I used these in Open Fast Combat in 1962,3,4, and 5 with some success but always on pressure. There was a restrictor available for the venturies but you may not have it. If not by all means neck it down some how. These engines used fibre gaskets and so didn't lend themselves to being shimmed up to lower compression. Clean off the residue and make you own out of soda can stock scribed out using a compass and chizzle fashioned from 3/32nd piano wire. I am told that turning the work rather than the compass works best for making shimms. Hope all's well wwith you and Aaron! Phil Spillman

Hi Phil,
I have the red restrictor, using a DS NVA, and will make some shims if all works out.
We are doing great, and aaron is about 75% finished with his new PAMPA plane.
Hope to see you soon.
Bill <><

Hey, Pancho - I must agree. The Johnson CS was one top combat engine. I had mine on more Voodoos than I can remember and never a problem when flying combat back in the 60's. When I got back into it in the 90's, the engine started showing its age. First, the glow plug blew out, then the rod broke. All fixed and then two of the six cylinder screws vibrated out, ruining the threads. I retapped them all for 5-40 and now it's back together, ready to run. I will probably have the piston/liner chromed, as it's a bit down on comression, making for tough starts. The only fuel we used back then was Fox Hi-Nitro, mostly on crank pressure.
I cannot imagine trying to get a stunt run out of that engine!
Bob Z

The Giant Stuntmaster has a 40" span, as I recall. Its cousin, the Giant Kingpin, is 43".

(If anyone has the Giant Kingpin kit for sale or trade, let me know...). Also, the Scientific Challenger. Pay your price.

So: The G. S. really is bigger than any combat models, except perhaps the very early days, where we used Ringmasters, etc (what was used on that Mickey Mouse Club segment, by the way? A Nobler!? Too many years...).

But...but...an 11-4ed GS, Johnson CS, on minimal nitro even, will be looking very, very hard at sub 4 lap times, given 60 ft lines.

But, hey, if that is what you want. It does have a certain charm...

The fun of a Giant Stuntmaster is slow, 55 mph stunting, though. That big, low AR wing, with a howling, unmuffled, shaking Fox. The fuse is stiff, and the tailfeathers are (what?) 1/4"? Good crash characteristics, knock on (balsa) wood; I'll probably roll it up next flight.

Mine sat in a pole barn for...decades. I restored it, and in doing so knocked out a bunch of hornet's nests, which lodged in the wing, whereever a spar/rib/LE/TE/bellcrank platform intersection occurred. I caught most, but not all. So...I would hear "sand" inside the wing. Cut the paper on the OB bottom wing, and shake, shake, shake. Hold it up to the light, even, and maybe see the stuff falling through. Or maybe not. Kind of like working a puzzle.

You think that you have it all, but, after a few sharp square maneuvers, more nests turn to sand, and the process continues.

To this day...

To tell the truth, the Johnson posts and looking at my Spacehound prompted the switch of engines!
We will see this weekend (if the weather gods cooperate) just what shakes out!
Bill <><
(looking for a 3.25-3.5 pitch prop)