Stalker 61 RE users

Went to the field yesterday to put up first flights on my new Chevelle/Stalker61. Wind was blowing hard so I put it off for another week. Realized at the last moment that I had not considered whether or not to use muffler pressure. Was wondering what others have found that works on the Stalkers. I actually have 2 versions of this engine. The older one has an all aluminum muffler, while the newer one has the carbon fiber tube section. If you are using muffler pressure, where did you install the pressure tap?

Allan Perret

Locally we are not using muffler pressure on the long strole version

Hi Allen,

First, I am not familiar with the Stalker 61RE but have some experience with the .40 and .46 Stalkers in SE version. My experience on wether or not to use exhaust pressure varies. I have used both setups on both engines. With the .40 I ended up using exhaust pressure as the only way to get a satisfactory engine run to complete the pattern. With the .46 that I am currently using the open vented setup is absolutely best over the exhaust pressure setup as it gives a much more stable engine run from beginning to end of pattern (same laptimes at beginning and end of flight). The .40 was hauling a much overweight and aerodynamically unsound aircraft so it could use the slow but noticable increase in power in the second half of the pattern when you do the square 8, vertical and overhead eight, the hourglass and cloverleaf. My current airplane is not overweight and aerodynamically OK (Vector) so it does not need the extra power, in fact that is a hindrance. Both planes used the same style tanks (tin, uniflow). So the best advise I can give is to try both open vented and exhaust pressure and see what suits you best. BTW, the greatest improvment I found using the Stalker in an inverted setup was using a lonreach glowplug which helped enormously in reducing speedup in outside manouvres. The explanation possibly being that a standard lenght glowplug causes a 'puddle' in the exhaust chamber where excess fuel accumulates during normal flight/inside manouvres. During outside manouvres G-forces 'clear the puddle' and improved combustion causes a power surge. Another Stalker 61 user (Paul Van Dordt) also reported on this power surge phenomenon during outsides so you might want to check if you have the appropriate glowplug.

Rgds, Bram Anker

Pressure or no pressure, that is the Uniflow question.

We all have our respective opinions regarding pressure on uniflow tanks. I personally have always used muffler pressure on my Stalkers, from the .40RE to the .61RE. I use it because it evens out the runs when the wind is blowing a little more than I usually like.

My experience with an open uniflow line is that when flying into the wind, the engine often richens up because of the increased pressure from the wind increasing the apparent speed when flying into the wind.

This also has effects when flying down wind to the point where I want to start my "trick". The engine leans out, the plane speeds up just prior to where I want to start the manuever. Then, when I'm into the multiple manuevers, (3 loops for example)the plane is now directly down wind, and the engine wants to settle back to the setting I made before launch, but, I had to start the manuever at a higher speed, with a slowing down during the multiple manuevers, unless I get some wind up from the wind.

Using muffler pressure, for me, helps even out the flight speeds throughout the flight envelope, due to engine speed up, or down due to varying pressure head to the uniflow.

It makes it a little easier to set size and repeatability to those manuevers.

OK, where do I mount the muffler tap? I mount it on the flat round portion of the muffler, where the header joins the muffler. It winds up fcing directly forward towards the engine

Appreciate the replys. Decided to set up for pressure tap just to make sure I have all the bases covered. John, not clear on your description of tap location. "Flat round" 2nd picture, is that what you mean ? If so I would have to move it around to about 3 on the clock because the tubing has to go under the cross piece because the cowl sits flush on that. 3rd picture is only other convenient location, kind of leary of that ?? Or I could put it in the side of the neck right under the cross piece.

Allan Perret

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Allen,

Picture number two is the correct location. John and I both run the pressure line like in pic. two.

Hope this helps.

Gordy

I run mine as in the center picture with the fitting pointing at the engine. I'm running an older .51RE and found it much more consistant on pressure. I also found it happier on castor/syth blend. I had heat problems and kemp cutting the cowl exit bigger, finally tried the castor and the problem went away.

Randy Ryan <><
AMA 8500
SAM 36
BO all my own M's

Glad to hear that.
I got me 4 gallons of Sig FAI Champion just to feed my 5 Stalkers.

Allan Perret

I don't run Stalker engines, but can tell you that the location in picture no. 3 would be a very bad choice strictly from a "physics" point of view. in that location you would have very high velocity gasses flowing at a right angle to the orifice of the pressure tap and would likely get a "suction" instead of pressure. A pressure tap should always be located in an area of maximum expansion of the exhaust gasses. The location shown in the second picture fulfills this requirement, although the pressure fitting might tend to clog up with oil at the bottom of the muffler as that position appears to be. However if it works for John and Gordy I wouldn't be afraid to use it. Locating it more to one side but effectively in the same general area should also work fine.

Randy C

Gordy, Ryan, and Randy have it right. You can mount it at any convienient location on the flat as shown in the middle picture.

Picture 2 does it!
That is if you feel that muffler pressure is a must.
My 61LS-RE and 66 both run perfectly on 15% Syn, 6% castor, 15% nitro, one head shim & Fox 1.5V long reach Idle bar plug with an Eather 3 blade prop.
Irrespective of wind, in a loop they both switch to 2 stroke at 30 degrees before the top, and switch back at 30 degrees after the top.
I do prefer the 66, it seems to be that little bit smoother and the extra power helps the model keep a line.
Great motors!

"Picture 2 does it!
That is if you feel that muffler pressure is a must.
My 61LS-RE and 66 both run perfectly on 15% Syn, 6% castor,
15% nitro, one head shim & Fox 1.5V long reach Idle bar
plug with an Eather 3 blade prop.
Irrespective of wind, in a loop they both switch to 2 stroke
at 30 degrees before the top, and switch back at 30 degrees
after the top.
I do prefer the 66, it seems to be that little bit smoother
and the extra power helps the model keep a line."

Props, what dia. & pitch you using. I have 2 of the cf Stalker 12x6 3-blade I bought back in 2000. Hoping they work out cause I dont think they are available any more. What's you RPM at launch?


Allan Perret

>My experience with an open uniflow line is that when flying
>into the wind, the engine often richens up because of the
>increased pressure from the wind increasing the apparent speed
>when flying into the wind.

Vent to the inside of the fuselage behind the firewall.

The vent does not no know "wind" after that...

Good point. I have already set up for pressure. But I will also try it vented inside the fuse for comparison. Thanks Brad..

Allan Perret

Allan, the prop is 3 blade Eather, 12 x 5.5", not sure of the RPM, I set it to switching 2-4 on the ground.