Stalker 61 "2-2-2" setup/prop?

A buddy of mine has an Infinity that he built around a Stalker 61 "2-2-2" engine from a few years back. I was just curious if anyone had a well-tested setup for this engine. One thing we found out right away was that the stock venturi would have been better suited for "D" Speed on a pen bladder than stunt - it's .350 if it's a millimeter. Of course, that made it just a little chargey in the maneuvers, not to mention pretty marginal to make it through the takeoff run. With no smaller venturis, we wedged a part of a golf tee next to the spraybar and this really, really helped. But then we switched props and it sounded like it was having a shaft run.

I'm guessing that the venturi wants to be in the range of .290-295, and we have only tried props like a depitched Bolly 12-6 (to 4.5" and it needed to be less). I would imagine that a 13-4 2-blade or maybe a 12-4 3-blade is more like it. It *really, really* didn't like spinning a Bolly 12-4 that was slightly cut down - seemed way too small.

No one around here has any experience with the engine, and I would appreciate anyone's tested knowledge on the topic. It looks like the engine had a lot of potential, and we will eventually figure it out, but anything that might shorten the development period would be appreciated.

EDIT: I also think Bob Reeves is running one in his Lagacy. Remember wasn't he the one who had a recent post about his ship pulling too hard? [email protected] He also has a Stalker 61 in his new Somethin'Extra.

I have 3 Stalker .61's and have spent a little time finding a good setup. May not be THE best as I have limited experience with pipes and my best may not be Expert best (Only Advanced best). Give me a little time and I will be able to tell the exact venturi I am using.

I can tell you the prop is a 13 - 5 1/4 3 blade CF I ordered from Chulan but not sure they are available any longer, this pitch gave me a 5.5 sec lap with plenty of line tension everywhere. I am running Powermaster GMA 5-22 with 3 head shims and Thunderbolt RC plug.

Will get back with the venturi size, and you are right the older engines came with an entirely too large venturi.

Edit: .291 without air filter, .299 with

Today, it was barely "fly-around level" best, so I think most anything would be an improvement!

>
>I can tell you the prop is a 13 - 5 1/4 3 blade CF I ordered
>from Chulan but not sure they are available any longer, this
>pitch gave me a 5.5 sec lap with plenty of line tension
>everywhere. I am running Powermaster GMA 5-22 with 3 head
>shims and Thunderbolt RC plug.
>
>Will get back with the venturi size, and you are right the
>older engines came with an entirely too large venturi.

A 13-5.5 3-b on a "2-2-2" engine? Does it two-stroke in level flight with that prop? The best we got so far (once we wedged a golf tee in next to the spraybar) was a Bolly 12-6 depitched to 4.5. We launched it at about 10000. It was a little too fast, but it was nice and stable and was just barely dropping into a 4 when it nosed into the fairly stiff breeze. But then I got what was marked as a 12-4 Bolly, but it wouldn't run stably at all and needed to spin about 1500 rpm faster than it did before. I thought the tee had fallen out but no, just the different load.

On the topic of the venturi, I could tell it was too large, but didn't have my calipers. What I did have was one of Jim Lee's prop-cutter-offer gadgets with a 5/16 shaft. Very loose in the hole, in fact, at least .040 thousandths over. 5/16=.3125+.040 = .352!!!! Given that an ST60 uses somethinng around .290-300, there doesn't seem to be much doubt that this was, shall we say, an issue. I can't imagine what application this might be used for, but there's no way in the world it was going to suck fuel that way.

I have found the Stalker 2-2 is really not much different than the 4-2 the only change is the head. Stalkers are not high revving engines more like tractors than Chevy's. If I wasn't so senile or had taken better notes I could fill in many of the details on what didn't work. Sad to say I have never put a tach on one, set the needle where it sounded about right, fly it and tweak as needed. I have two tach's just never seem to get one out after I have the engine dialed in.

I finally had pretty good luck with mine. Here's what I did and it worked well, though you probably won't like the prop. I didn't want to even try it until Pat Johnston practically broke my arm to get me to use it. It was one of his.

.320 venturi (seems big, but smaller than stock)
Idle bar plug (I used a Fox Miracle plug, but other idle bars would probably work fine too)
Chicken hopper, uniflow tank. (my own design, but I imagine any uniflow would work)
5%/17% all synthetic fuel (very important, don't skip it)
Prop: 14x5 RevUp THP cut down to 13.5 and cleaned up (I suspect a 14x5 Zinger prop kit shaped similarly would work too)
Ground launch rpm was about 9700 just bubbling on the 2/4 stroke border. Lap times were right on 5.3 seconds with a ton of power. Took about 6.25oz of fuel per flight.

Anyway, that what I ended up with and it was pretty happy.

I'm currently building for the Stalker .61RE and would like to know what brand of fuel you were using if you didn't blend your own. Just about everything I have seen in the shops so far has some castor in it.

Keith Varley and John Miller,

Would you guys please let us Stalker "newbies" in on what fuel we might be able to get in the LHS for these motors that complies with Chulan's no castor emphasis?

I love big old style thumpers and given the advantages of the rear exhaust I'd really like to make the Stalker happy in my new ship.

Well, I used all synthetic Wildcat fuel from the LHS. It came in FAI, 5% and 10%. I acutally ordered the Wildcat %5 nitro/17% oil from my LHS guy. He had the FAI fuel in stock.

Sure made a difference. Don't know what Keith used, but his ran very well too.

edit: I really should use the preview function.

Magnum FAI fuel, nothing added to it.

Launching RPM, 7400 to 7600

APC 12 X 6 prop. (I am considering a 5 pitch as it does break a little harder than I like, or adding a head gasket.)

I'm using one of the newer mufflers without the heavy restriction of the older versions.

I don't see any need for adding Castor, or Nitro. The engine makes gobs of power.

Hope this helps,

John

P.S. This is really John Miller on Gordy's computer.....

Regards and Happy Mothers Day to all the Wives and Girlfriends out there.

Mr. 1969 NATS

Bob Lampione

Hey, yeah, I forgot about that! Kaz ought to know something about it.

But I think I now see where it was going wrong, at least in the gross. But I think I might be able to do a bit better than a golf tee* jammed in the venturi!!!

Brett

p.s. It *was* at least a Big Time Stunt golf tee- MR. Fancher had hit a golf ball off of it before. Far better than those regular old "sport flier" golf tees.

Here in Brazil we use for testing a *lone star venturi*.

Just stick a wedge of balsa in the venturi and you can at least have an idea of how a smaller venturi will work. Never heard any cases o the balsa coming out on flight.

>Just stick a wedge of balsa in the venturi and you can at
>least have an idea of how a smaller venturi will work.
>Never heard any cases o the balsa coming out on flight.

That was idea #1. Only problem was that I didn't have any balsa at the time.

The workmanship of the engine is good. The timing isn't out of the ordinary. The curved baffle? .... baffle .. smaffle .. neat but probablly not any effect one way of the other. But .... the bypass ... Its a huge volume ... The total volume is probably twice that of an ST, maybe more. I use artist clay to quickly mold bypass volumes. Pack it in and a minute or so with the hot air gun to harden it. I must sound like "Johnny one note" but I've got to wonder. I gave up on the motor with the NATS comming on and never did experiment with filling up the volume. For sure the verturi was too large stock, at least for a smaller prop.

Good Luck
Frank Williams

Brett,

Is Uncle Jimby considering bringing his Infinity to the N.W. Regionals?

Yes (well, assuming he can overcome his many neuroses over paint and actually get it done (in fact, he and Ted are both planning to have maiden flights weekend after next))- but that's not the one at question here. Uncle Jimby's will have a PA65, and let's say it has had some asthetic changes made to it.

The model in question was built by Jim Goss (Charter member of the Northern California Circle Jerks). I flew it, and although the engine was *incredibly* chargy, it did seem to have some good characteristics and similar feel in some ways to the original. There seems to be no question of the Stalker providing sufficient power, more like how to I get rid of some of it.

Between the information here, and also that supplied by Brian Eather, I think I have a pretty good idea where to go next.

I have two Stalkers in process of getting planes. I also have a variety of venturis. I have been in contact with Jim, however, I'm not sure what size he wants or his address. I have your address. I can mail what you want. Let me know.

Cleon

New: Brett. Just heard from Jim. He has a delrin venturi on the way, but the offer stands....

C

Scott(need to know)Riese:7