Tower Hobby GP .42

I just happened on to a used GP.42 and was wondering what the conventional thinking is on these engines. I have not attempted to run it yet, but the first impression is;
A. Seems to be decent quality.
B. Not overly porky.
C. Has a goofy carb mount, may complicate a venturi installation.

Anyone famliar with this engine? Any advice? (be nice now)

Assuming this is the Thunder Tiger unit, see:

http://www.clstunt.com/htdocs/dcforum/DCForumID1/11437.html

>I just happened on to a used GP.42 and was wondering what
>the conventional thinking is on these engines. I have not
>attempted to run it yet, but the first impression is;
>A. Seems to be decent quality.
>B. Not overly porky.
>C. Has a goofy carb mount, may complicate a venturi
>installation.
>

They drop right into an FP or LA mount with the same shaft length.
They are good quality as you state.
They are NOT a copy of the FP or LA, but their own bore/stroke combo.
They run quite well, and can run even better when modified.
The venturi conversion isn't difficult. Just remove the carb and sell it to someone who just broke his flying RC.
Then get a venturi and slide it in the hole (the hole is tapered, by the way) that is vacated by the venturi and drill through the case at the upper portion of the circle that you will see on once side of the case. Drill a .140 hole and use an OS needle. The needle will end up about 1/16 lower than "normal" but will not affect tank height.

>The venturi conversion isn't difficult. Just remove the
>carb and sell it to someone who just broke his flying RC.
>Then get a venturi and slide it in the hole (the hole is
>tapered, by the way) that is vacated by the venturi and
>drill through the case at the upper portion of the circle
>that you will see on once side of the case. Drill a .140
>hole and use an OS needle. The needle will end up about
>1/16 lower than "normal" but will not affect tank height.

This is the second time I've seen your method of venturi installation described, Len. It doesn't sound like this method is reversible, unlike other engine conversions from RC to CL. I'm not saying that's bad necessarily, just something to consider before one drills a hole through the case.

Does Thunder Tiger make a bolt-on venture holder that would preserve the carburetor mounting?

This motor is an absolute bargain and is usually sold from $49.95 to $59.95 and generally at the lower price.
You won't be able to return to an RC version once you convert to C/L using Leonards method and no Thundre Tigre dosn't sell a c/l adaptor and probably no one else will make one for sale either.
That said if you really have to have one for R/C then you can usually pick one up cheaply for around $20.00 on the bay. Believe it or not I got 2 of them that were as new, just didn't have a box or papers for about that price each.
They make really good C/L motors and yes if you compete then you need to use .018 lines rather then .015. Airplanes that I have these motors in don't seem to mind the extra .003
Dennis

And Brett says the .018s actually work better even on planes where one can use .015s. They stretch less, and give more positive control. I assume he means at the top end of the range, i.e. with a .36 or .40 engine.

So do these things run OK with the RC carb in place? Just curious..

Isky,
They run O.K. with the carb. wired open, albeit fast when they
run away. They run absolutely great after the boost port is plugged
and a venturi is installed. Lots of torque with a 12 X 5 and a need
for no more than 5 % Nitro.

Don't worry about the .018 lines as there is more than enough
power to haul even my 60 oz ships around.

Curiously enough, my preference would normally be for the .015
lines over the more clumsy .018's for most engines. Ham-handed guys
like me really can't feel the stretch of the .015's or the lack of
therein of the .018s.

The TT .42's are inexpensive, quality and a quick bolt in solution
for a heavy ship.

Best regards,

Richard Ferrell
(one of Bud's partners in crime)

"Curiously enough, my preference would normally be for the .015
lines over the more clumsy .018's for most engines. Ham-handed guys
like me really can't feel the stretch of the .015's or the lack of
therein of the .018s."

Dick,
Cannot feel the stretch? That sounds like another investigative experiment appropriate for examination out at the "Old Neddy" flying field. Now all we have to do is wait for the snow and freezing weather in Chicago to warm up and we can try that experiment (using one of your planes of course ).
DennisV

I assume one can get away from the runaway problem by just letting it run where it wants to and use a 3-4" pitch prop? There's an APC 11x3, a 11.5x4 and a 12.25 x 3.75 (the latter, the local RC prop-hanger type fliers like to use).

good C/L motors and yes if you compete then
>you need to use .018 lines rather then .015. Airplanes that
>I have these motors in don't seem to mind the extra .003
>Dennis

AMA Rules for stunt lines are 35 years out of date. We should have gone to .018" at .35 long ago. A modern 40 on .015 lines is on the edge of failure.

>
>AMA Rules for stunt lines are 35 years out of date. We
>should have gone to .018" at .35 long ago. A modern 40 on
>.015 lines is on the edge of failure.

Hi Paul,
What's craizer is that .015s are legal on very large .40 piped ships!
Of course, IIRC, the FAI has no regulations as to line diameter.
Bill <><

Sagameister...I'm just a phone call away. I'll turn one for you without the thru hole if you want. As the seagull once said ...One good tern deserves another.

Divot

>Sagameister...I'm just a phone call away. I'll turn one for
>you without the thru hole if you want. As the seagull once
>said ...One good tern deserves another.
>
>Divot

The neck of the venturi is about the same diameter at the top as an FP with about a 3 degree taper towards the bottom. I have Delrin venturis for this in stock (easier to drill the cross hole--easier to make, too) but if you are offering to make one for free...

As to returning the engine to RC, I don't know why anyone would want to use an engine for dual purposes. If you convert it, convert it. A lot of ST 46 and 60 engines started life as RC, but did we ever bother to convert them back?

The only time I ever flew an RC plane was once when a guy I was watching fly asked me if I wanted to try. He handed me his transmitter and I flew it level for a short stretch and then did a loop. He grabbed the transmitter and that was the end of my short lived glory. In CL we only fly a couple of laps straight and level and I guess it just got the best of me.

WHO SAID ANYTHING ABOUT FREE ?

Thanks for the info Len.

>
>WHO SAID ANYTHING ABOUT FREE ?
>
>Thanks for the info Len.

Divot,
I'm sure we can use the barter system I have TT veturis that you want ,,,,, you have TT veturis I want,,,, You want to learn to fly as good as I,,,, I want to learn to divot like you ((((NOT))))RRRRRRRRRRR
Good idea though I'll call ya

THANKS to y'all for the info looks like the GP.42 might be an OK engine (I don't mean an "OK" engine, I just mean an OK engine) well what I really mean is it should be,,,,,, Never mind,,,,

I've used a GP 42 on a Brodak Tanager for a few years now. I adjusted the R/C carb throttle wide open with the arm up against the exhaust outlet. It worked just fine until I drive it straight onto the ground. The little flanges that hold the carb in place broke off, forcing me to machine a C/L venturi for it. I used Leonard's list to determine the correct bore size, turned an aluminum venturi to properly fit the cast tapered engine intake hole, and secured it with a 4-40 screw on one side only. The NVA was placed above the engine casting on a slight angle away from the prop. What a great engine!

I thought you used wood props! That looks like plastic to me.
Is it fixed?

MO,
Thanks for the photo. AND thanks for the info. I like what I see and I like what I hear. I will have one flyin' come spring. Not real sure what I'll put it in yet, got lots of choices....

What prop, fuel, and speed do you run?

This plane/engine combo flew best with a 12-4 wooden Zinger prop and using regular R/C type fuel, 10% nitro, castor/synthetic.
I may not use wooden props any more though. Last weekend after start up, the blade tips touched our temporary cardboard launch platform and stalled the engine. Thinking nothing of that, I restarted the engine and got launched. After one lap it threw a blade, made a horrible buzzing sound for a split second, and killed the engine again, losing the other blade. Upon examination after a smooth landing, I realized that the fuselage was split vertically half way along the wing, above and below, and the wings were split from the fuselage half way to the tips, slightly ahead of the spar! Serious damage, much repair necessary. Luckily it threw the blade in flight, not while we were starting and holding for launch. It also shook the muffler bolts loose. I believe the engine is fine, but I won't know for sure until well after Christmas, once the plane is repaired, again.
Cheers!
Mo