woodburner

So guys...

Here I am with my new H9 Phoenix 7 ready to go and I enrolled for an F3A contest next July.

Thing is ... I'm using the Phoenix for a couple of reasons:

1- I already had two new .60 engines
2- I can't afford an Oxalys or any of the new breed aircraft...

Sooo... I need to be able to slow down the P7 and still have torque for the uplines.

My idea is to use a Super Tigre G60 with an APC 12.74 x 4.75 (it's turning almost 13500 rpm on 10/16 fuel, but it's still being broken in).. I thought of this prop because it's in the upper diameter range for this ST and has a low pitch, theoretically allowing more torque at lower rpms

Will this arrangement do it?? Any advice????

Thanks!

TonyF

My Feedback: (92)

I flew the P-7 of Tak Takayama's a few weeks ago. He had an O.S. .65 piped with an APC 12x7 on it. I can't say it was slow, but it had pretty much unlimited vertical. I think 4.75 pitch on a Tigre G60 is going to be too slow. Maybe a 6 pitch. But try it, it might work. Are you going to use a pipe?

Have you looked at the crop of "70" size models like the Nuance 70 or Axiome 70? Quite a bit lower cost but they still fly well.

woodburner

No pipe, TonyF... I'm trying to slow it down, you see. I believe the lower pitch will give me more torque for the uplines and the bigger prop disk will slow it down on the downlines (also the bigger prop is a heavier load).

The Phoenix was designed for "old school" (1970's 1980's) pattern, not for turnaround. It's too fast for turnaround if flown as designed.

What do you think?

TonyF

My Feedback: (92)

I've had maybe 10 Phoenix's over the time, starting in 1976. You might check out the build thread I did at another site on my latest H-9 one.

http://www.rcgroups.com/forums/showthread.php?t=2100044

You have all the right ideas for trying to get a P-7 to fly turnaround. But I think the prop you've chose will be too slow. If the engine goes to 14.5K in the air, that's only around 65mph airspeed. Too slow for the P-7. Even our 2-meters are doing more then that in level flight. If your engine can turn a 12x7 at 13K in the air, that's 86mph. Now that is at full throttle. You're going to need to throttle down some in level flight and add it for uplines. But I think it will fly a lot better then with the 4.75 prop.

Are you going to be flying P-15 or the other F3A class?

woodburner

I haven't flown F3A in competition for well over 20 years, so in this particular contest I'll fly the basic schedule. Should I try a 12x6 APC maybe?

woodburner

Is the "F" in your ID what I'm thinking it is?

TonyF

My Feedback: (92)

Don't know about the "F", I've been called a lot of things over the years!

I would certainly try a 12x6. I'd try a lot of different props if you have them. I'd also consider putting a pipe on the engine. It seems counterproductive, but it actually takes more power to fly slower in level flight then to fly fast all the time. You use the throttle to keep the speed at what you want, but when you enter a vertical it takes a lot of power to have the performance you need.

woodburner

F for Frackowiak?


Super Tigre pipe headers are all but inexistent here in Brazill . I do however own an OPS Ursus 60, with a pipe... brand new, which I plan on using on the P7. Matter of fact I took a few pics with it installed on the plane.

woodburner

Yep... your photo answered my question.... and I thought I was enlightening someone about the Phoenix's origins, LOL.....

TonyF

My Feedback: (92)

Nice looking Phoenix! And I love the background! Looks like where I started flying in Pennsylvania.

I have to warn you, you never know what kind of shady characters you'll meet on the internet!

I would lengthen that pipe out on the OPS and give it a try. I don't know exactly what length, but if the engine sounds great in level flight and drops off in a decent size loop, lengthen it.

Macs still sells a lot of headers. They also sell direct. You might check out their website and see if you can order what you need there. I've recently bought a few things and I got very good service.

woodburner

Yeah forgot about MACs... BTW let me ask you... is it preferable to use a pressure nipple off the header or off the pipe itself? My pipe came with a nipple already installed half way.

TonyF

My Feedback: (92)

Honestly, either way works. I usually tap the header just in front of the coupler. I don't tap it near the exhaust of the engine. If your pipe already has a pressure fitting go ahead and use that.

MTK

With nipple in middle of the pipe you will get less pressure variation with each power pulse. Pressure will still be greater than atmospheric and you will pressurize the tank enough to deliver fuel consistently. Back in the day, people tried nipples on headers and nipples on pipes...in the end pressurized tanks still happened with eaither technique.

Do as Tony suggests and lengthen the pipe as far as 16-16 1/2" inches from exhaust flange to the reflector in the pipe. But use a larger load such as 13x6-7. The larger disc will help your speed. The longer pipe will help by slowing rpms but increasing torque. If the gear won't allow the larger diameter, consider a 3 blader.

In F3A flying, speed may still be high enough to be uncomfortable. You may need to resort to some external means of slowing down like air brakes....vertical tabs on the wing and stab TE about 1" vertical width x 2" long, at the wing tips and smaller on the stab tips. Some guys have put these on the rudder but I wouldn't recommend that.

Curious, why a Phoenix 7 for current F3A? Not a particularly good snapper and in F3A you need that capability.

woodburner

A variety of reasons... I flew a Phoenix about 35 years ago and I loved it. Also, I can't afford today's fancy F3A planes and hardware... and I already had a couple of new 60 engines. I have no dreams of winning, just want to participate again.


Art

stuntflyr

I used a 12.25x3.75 on my OS 46 Kaos in Sportsman and it helped a lot. Box was small, model stayed close, the engine revved way up there but the speed was easy to modulate after a few practice flights.
Pipes have been used in 1/4 wave to slow C/L Stunt models on the downhill for 25 years now and they only fly in a 70 foot hemisphere, so if you adjust the pipe length you can get it to brake on the downline pretty easily in a day of flying and testing.
I went to a Osiris 90 sized AMA Pattern style model after the Kaos and determined that it's way better suited to the modern AMA sequences.
Chris...