PA 61

Hi friends

I would just like some starting points w/the PA-61

*Tank size using 5% nitro
*prop size 2 bld and 3 bld
*fuel type that works best
*Plugs-what type
*pipe length( starting point only)

I have never used a PA 61--I am going to try one in a 680 sq model somewhere in the 64 oz range.


thanks David

>
>Hi friends
>
>I would just like some starting points w/the PA-61
>
>*Tank size using 5% nitro
>*prop size 2 bld and 3 bld
>*fuel type that works best
>*Plugs-what type
>*pipe length( starting point only)
>
>I have never used a PA 61--I am going to try one in a 680 sq
>model somewhere in the 64 oz range.
>
>
>thanks David

Hi David,

I use a 6 oz. tank. Usually taking out 1/2 oz. of 5%.

12-4 3 blade Bolly, 12 1/2-4 Bolly 2 blade.

Sig 5% Champion in most all occasions. !0% in the "bad heat".

Thunderbolt Hot plug.

17 1/4 pipe length.

All from Randy. Give him a call!

Bill <><


Big Bear <><
Character: It's what you do when no one else is watching.

Hi David,
I'll tell you what worked for me. I used a Thunderbolt RC Long plug.I tried the Thunderbolt 4 cycle plug it's fine also. I used 10% Sig Champion fuel & it charged a bit too much for me so I switched to Byrons 10% added some castor & it calmed down a little. I set my pipe @ 18" to achieve the smoothest runs.I used a 7ounce tank. The prop was a variety of brands 13-4 2 blade. I used a 3 blade on my PA.65 .
Hope this helps.

I think I have some sort of fuel demon that follows me around. When I used an ST60, it seemed it always took about 7.25-7.5oz to get through a pattern. Others used anywhere from 5.5 to 6.25 ounces. With the PA 61 I ran, it took every bit of 6.75oz to get through a pattern. Others seemed to do fine with 5.75 to 6 ounces. Not sure why that is, but if it were me, I'd rather put a big tank in and pull fuel out. Easy to have too much capacity. Much tougher if you don't have enough.

As for the reast, Bill and John are in there.

One thing you need to be aware of is you can do a variety of things with the engine. You can run an 11/5 inch two blade up to a 13 inch three blade (which is what Matt ran). You can vary the venturi size, adjust the head shims, move the pipe in and out depending on the rpm. Shorter and two-blade props will run faster and need a shorter pipe length. Longer and multi-blade props will load it more and run a bit slower with a longer pipe length. A bigger venturi allows a bigger prop. If the engine charges too much you can add head shims (just a couple thousand at a time). If you don't get enough "kick", you can reduce the amount of head shims or go to a bigger venturi, or...

Randy has a chart for the various size props and rpm ranges in relation to needed pipe length to use for starters. If you use his recommended head shims, venturi, prop, rpm, and pipe setting, you will be off to a good start. Many people will have many different ideas of what works best--for them. Just remember, there are no absolutes (such as this prop or that prop or this pipe length). But there are formulas that need to be followed if you vary from the chart.

thanks Len
I like your common sense approach.....
I hear you Len; I know it's Randy motor, and all that stuff.. I know that calling Randy is an excellent idea, however, I am also curious as to what has worked for other people..Sometimes these motors are like guitars, yeah its a fender strat, but it sure sounds and plays different than the last one I had..

The "effective" window is what I guess I am looking for....

David

I think you should use Sig fuel. Color coordination is important in the top echelon of stunt.

Howard Rush

I know for sure that Howard is correct. I had a white plane in 2005 I used the byrons fuel & the under area aft of the pipe turned orange from the Byrons fuel.

One thing you didn't address is the configuration of the engine. Randy told me that ALL PA.61SE engines have conventional (non-pipe) timing. You should definitely call Randy for initial set-up. In fact, Bill Little told me that when he and Aaron go to contests, they just ask Randy for the appropriate set-up for that day's conditions.

>One thing you didn't address is the configuration of the
>engine. Randy told me that ALL PA.61SE engines have
>conventional (non-pipe) timing. You should definitely call
>Randy for initial set-up. In fact, Bill Little told me that
>when he and Aaron go to contests, they just ask Randy for the
>appropriate set-up for that day's conditions.
>


That's a fact, Ralph!

When Randy's there, it's just a matter of asking him. So far, over several years, he hasn't missed yet!

It's somewhat amazing, but I haven't had to change the pipe length on my Geo Juno a single time. And the engine runs are exceptional! Randy "designed" them, developed them, and knows what to do to them better than anyone else. That's a fact.

Why do I need to know when he does?? LOL!!

Big Bear <><
Character: It's what you do when no one else is watching.

You perhaps can increase your mileage be using a smaller venturi. You will give up a little power but if fuel usage is important to you, you will likely develop enough power to pull the sled anyhow, especially with the PA.
Jon Ramsden
<@_@>

I can second what Bill say's about the set-up. I never changed the pipe length on my PA65 from day one for two seasons. Once I got the plane speed/prop/mixture point set per Randy's instructions, it never changed.

I moved up and down in Nitro as requied in the heat/humidity but the basic set-up stays the same.

At the end of last season, I wanted to validate my own understanding of the pipe operation so I changed the fundamental set-up to a much flatter prop. Went from a ground launch of about 9600 up to about 10,300. Pipe went in to the chart setting. and I proved that the engine will cycle EXACTLY the same way and sets on the ground, without a tach, the same way. It drops right down to a four in level flight and cycles up to a 2 at the tops--a little adjustment of Nitro content can place exactly where it comes on and how hard. It can be deep in a four stroke at 11,000 or 9500--just depends on the pipe position and prop.

I flew the same lap speeds with both set-ups.

For any given prop and nitro, the depth of the four cycle, or the operating point as I call it, is set with the pipe length. THe needle has a very narrow range of PROPER operation--it sets the correct fuel mixture.

You can force the engine out of the sweet spot with the needle but it won't be as powerful or friendly.

Randy has spent thousands of hours with these things and you just have to watch him set his own engines to know that what he says works.

Works for me.

Curt