Author Topic: Stalker breaks too hard. (Read 7030 times)

Dave Royer · « **on:** March 07, 2015, 07:37:45 PM »

Greetings from a Stalker newbie seeking advice,

My engine has "st 60 pro" cast into the case. It's a rear exhaust Stalker I acquired slightly used about 10 years ago but otherwise its history is unknown to me. It started and ran sweet on the bench but in the airplane when it breaks from a "4-stroke" to a "2-stroke," it comes on way too strong. The plug is a Thunderbolt R/C Long, I'm running FAI all synthetic oil fuel and a 12-6 three blade prop in a 62 oz. airplane. I would appreciate any ideas on what engine version this is and how I might calm it down for a flyable stunt run.

Thanks,

Dave

RandySmith · « **Reply #1 on:** March 07, 2015, 08:28:56 PM »

If it is breaking too hard these are a few things to do, Go to a 5 or 5.5 pitch prop, go to a larger diameter prop of same pitch, add a head shim, reduce the size of the venturie.
or a combo of the above

Randy

Dave Royer · « **Reply #2 on:** March 07, 2015, 09:07:06 PM »

Thanks for the response Randy. I've got ground clearance limitations so the 13" props are out until I get some taller gear. Lowering compression with no nitro fuel feels a bit counter intuitive but I'll give that a try first. Thanks again.

Dave

Walter Hicks · « **Reply #3 on:** March 07, 2015, 10:28:51 PM »

Hi Dave, per our conversation today at the field. I have two actual Stalker props( they do not make them anymore. They are cut down
3 blade is a 12x6 cut to 11"and 2 blade is 13x6 cut to 11.75.)

I also have an Eather 2 blade that was recommended for a Stalker 66 it has been cut down from 13'' to 12"

also a Thunder Tiger 12.5x5.5 I will get them in the mail as soon as I can . W Hicks

Brett Buck · « **Reply #4 on:** March 08, 2015, 10:04:39 AM »

Quote from: Dave Royer on March 07, 2015, 09:07:06 PM

Thanks for the response Randy. I've got ground clearance limitations so the 13" props are out until I get some taller gear. Lowering compression with no nitro fuel feels a bit counter intuitive but I'll give that a try first. Thanks again.

All the Stalker 60s I have seen locally have had grossly excessive venturi diameters as delivered, and in all cases, the owners either gave up, or got smaller venturis.

Brett

Dave Royer · « **Reply #5 on:** March 08, 2015, 10:19:59 AM »

It was great to see you at the Fun Fly Walter and I really appreciate the loan of the props to try. As Brett has suggested, I think the original owner may have given up right away with the supplied venturi as this engine seems to have very little time on it. I'll measure the one in it and see what's up with that. Thanks guys.

Dave

rustler · « **Reply #6 on:** March 08, 2015, 02:27:36 PM »

When you say it's breaking too hard, I assume you mean the model accelerates in the climb? (And slows down in the dive?).

Chris Wilson · « **Reply #7 on:** March 08, 2015, 04:29:39 PM »

Can you move the tank forwards a bit?

RandySmith · « **Reply #8 on:** March 08, 2015, 07:02:30 PM »

Quote from: Dave Royer on March 07, 2015, 09:07:06 PM

Thanks for the response Randy. I've got ground clearance limitations so the 13" props are out until I get some taller gear. Lowering compression with no nitro fuel feels a bit counter intuitive but I'll give that a try first. Thanks again.

Dave

Hi Dave

i gave you more to try, so use a smaller venturie, and if needed a lower pitch prop, don't worry about adding a shim, both of those will make your problem much improved

Randy

Dave Royer · « **Reply #9 on:** March 08, 2015, 09:15:27 PM »

Well I checked the venturi with a caliper and it is huge as suspected. I changed that this evening and will test tomorrow. I'll save the head shims for when/if I add any nitro to the mix. Thanks again to Randy and all those contributing to my efforts with this new (to me) system.

Dave

Dave Royer · « **Reply #10 on:** March 09, 2015, 07:13:38 PM »

Problem solved. Much smaller venturi did the trick. Learning to set the needle correctly with no nitro fuel is the next challenge. Thanks for everyones input.

Allan Perret · « **Reply #11 on:** March 09, 2015, 07:37:59 PM »

Quote from: Dave Royer on March 09, 2015, 07:13:38 PM

Problem solved. Much smaller venturi did the trick. Learning to set the needle correctly with no nitro fuel is the next challenge. Thanks for everyones input.

Why are you using no nitro ?

Chris Wilson · « **Reply #12 on:** March 09, 2015, 07:51:31 PM »

From the Modusa Stalker web site-

"Fuel - 17% to 22% synthetic oil (Klotz is recommended) , no castor oil for Stalker ABC piston/liner. WE DO NOT RECOMMEND THE USE CASTOR OIL IN THE FUEL.
Nitro 5 -15% depending on wind conditions etc., more Nitro less fuel economy. For 0% nitro fuel, remove one or two of the fitted head gaskets, for 8-15% nitro add one or two extra gaskets. Increasing the nitro content of the fuel also increases the compression and you MUST allow for this by adding the extra head gaskets. If you do not add the extra head gaskets you will cause damage to the small end of the con-rod, possible snap the gudgeon pin and or damage the piston. "

I guess the answer may well be "why not?"

Dave Royer · « **Reply #13 on:** March 09, 2015, 08:47:46 PM »

At the time I started this project, FAI was synonymous with no nitro and that was the experience I was looking for. And indeed, why not? To me it's all a "Come on, it'll be fun!" kind of thing in the end anyway.

Dave

Allan Perret · « **Reply #14 on:** March 09, 2015, 11:07:28 PM »

Quote from: Dave Royer on March 09, 2015, 08:47:46 PM

And indeed, why not?
Dave

Because as you stated, it makes it harder to set needle.

Chris Wilson · « **Reply #15 on:** March 10, 2015, 01:41:11 PM »

Quote from: Allan Perret on March 09, 2015, 11:07:28 PM

Because as you stated, it makes it harder to set needle.

Hi Al,
That may have been the case with the older larger Venturi but with a correctly sized one I am betting that the challenge will be nonexistent.

Brian Hampton · « **Reply #16 on:** March 10, 2015, 06:54:58 PM »

My Stalker 61 (gold head, 2-2 version) came with a 7.5mm venturi and has always been run with zero nitro fuel. Needling was never sensitive to me but that may be because I've never used nitro so can't compare.

John Leidle · « **Reply #17 on:** March 11, 2015, 11:38:30 PM »

Hey Buddy , NO NITRO !!!!?? My stuff likes 15% all Synthetic ... have you tried a 12-7 APC

??
John

Brett Buck · « **Reply #18 on:** March 11, 2015, 11:50:18 PM »

Quote from: Chris Wilson on March 09, 2015, 07:51:31 PM

I guess the answer may well be "why not?"

Part of the reason is that it is very hard to find, in most cases, you have to special order it or mix it yourself. In fact, if you buy from hobby shops, even 5 or 10% is not always easily available.

Brett

Chris Wilson · « **Reply #19 on:** March 12, 2015, 03:43:01 AM »

Tower Hobbies seems to sell 2 types of FAI fuel, as does Byron fuels and SIG.

But most stores in the States don't stock it?

Dane Martin · « **Reply #20 on:** March 12, 2015, 08:09:25 AM »

Not that I'm adding to the stalker engine talk, i know nothing about them... But I've lived in las Vegas since 1996 and i don't remember ever seeing FAI fuels in the hobby shops. It's always been 10 and up.

Brett Buck · « **Reply #21 on:** March 12, 2015, 09:14:55 AM »

Quote from: Chris Wilson on March 12, 2015, 03:43:01 AM

Tower Hobbies seems to sell 2 types of FAI fuel, as does Byron fuels and SIG.

But most stores in the States don't stock it?

Most have never even heard of it. Neither are they aware the existence of the FAI, for that matter.

There's an irritating tendency among 20something hobby shop clerks to refer to glow motors as "nitro" motors.

Brett

Dave Royer · « **Reply #22 on:** March 12, 2015, 09:25:37 AM »

I'm just experimenting with this setup. I haven't gotten to prop testing yet but will definitely try the APC 12-7 at some point. I'm getting some pretty good stuff from the MA 12-6 3-blade for now. Currently working on getting a handle figured out. The nitro amount is as yet to be determined but the original quest was to try to make it work with none at all.

Dave

Brian Hampton · « **Reply #23 on:** March 12, 2015, 06:25:03 PM »

Quote from: Brett Buck on March 12, 2015, 09:14:55 AM

Most have never even heard of it. Neither are they aware the existence of the FAI, for that matter.

Just to clear things up, the FAI (Fédération Aéronautique Internationale) is the world governing body for all types of airborne competitions like parachuting, gliding, hang gliding etc and sets the rules for events so all countries are on an equal footing especially when records are to be set. In the case of aeromodelling and fuels, what's called FAI fuel is 80% methanol and 20% pure castor. This is only required to be used where engine HP is a prime requisite for setting records and is only applied to CL speed, RC Pylon and FF power. This avoids secret blends of fuel and the FAI fuel is supplied by the organisers. With one exception, in all other events (CL stunt for instance) you use whatever fuel you want. The exception is CL combat where nitro is limited to 10%.

Chris Wilson · « **Reply #24 on:** March 12, 2015, 06:59:50 PM »

Quote from: Brett Buck on March 12, 2015, 09:14:55 AM

There's an irritating tendency among 20something hobby shop clerks to refer to glow motors as "nitro" motors.

Brett

Hah! What gives me the extra irrit's is seeing a model diesel advertised as "Nitro" when really .......... simply being a diesel should be cause enough!

Brett Buck · « **Reply #25 on:** March 12, 2015, 08:52:29 PM »

Quote from: Brian Hampton on March 12, 2015, 06:25:03 PM

Just to clear things up, the FAI (Fédération Aéronautique Internationale) is the world governing body for all types of airborne competitions like parachuting, gliding, hang gliding etc and sets the rules for events so all countries are on an equal footing especially when records are to be set.

I am pretty sure everyone here understands what the FAI is. I don't really want to spend the time to explain it to the metal-head RC car jocks at the local hobby shop, however!

Brett

John Sunderland · « **Reply #26 on:** March 12, 2015, 09:44:40 PM »

Just ad a head shim. Extras came with mine. Easy fix. With that head shim it gives you the ability to give your FAI fuel a boost on those muggy 90 degree days. With FAI it only burned 5.5oz. On 10% nitro and a larger venturi made almost on par with a ST 60 of the day but, it was really a poor comparison.

Mine liked a 12 x 5.25 pitch wood prop. I carved mine from some old Rev-Up 16/ 4 pitch Joe R. found at an estate sale. In 1997 or 98

that sounds like yesterday to me.

. By hand.

Steve Helmick · « **Reply #27 on:** March 19, 2015, 02:08:07 PM »

What percentage of Coleman lantern fuel are you using, Dave?

Steve

Alan Resinger · « **Reply #28 on:** March 19, 2015, 03:55:32 PM »

Dave,
When I come down to Portland next month I'll bring some shims, a couple of extra venturi and some special props for the Stalker that you can try. I remember that the gent that makes Stalkers told me he uses all castor FAI fuel but would use 50/50 if he could easily get Klotz.
Alan

Dave Royer · « **Reply #29 on:** March 19, 2015, 08:26:40 PM »

The problem has been most happily solved. Got a hand full of venturis from Kaz and settled on the metric equivalent of a .295 for just the run I was looking for. Thanks for the offer Alan. Special props are always welcomed. I have been very pleasantly surprised by the power this thing produces with no nitro.

And to Steve: I'm using two drops of Colemans in the venturi for the first cold start. Nitro? We don't need no stinkin' nitro!

Author Topic: Stalker breaks too hard. (Read 7030 times)

Walter Hicks

John Leidle