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PHOENIX Sukhoi .46 nose weight ????

Old 11-08-2005, 07:38 AM
  #1  
da Rock
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Default PHOENIX Sukhoi .46 nose weight ????

I picked up a PHOENIX Sukhoi SU-31 .46 size a couple of weeks ago at the LHS. It looked pretty good when I looked into the box. Turns out there are a lot of plusses to that ARF. And... maybe a minus or two.... but that's to be seen.....

I was in the LHS yesterday and one of the clerks asked how my Sukhoi was coming along. He had sort of a sly grin when he asked.

After I went through the litany of what I found that had to be corrected and that I feared might cause the next purchaser troubles and what I found kewl..... He was grinning even wider. So he tells me that after they'd special ordered it for me and had seen how nice it looked and how it came with the surfaces already hinged etc etc he tells me about the guy who bought the next one after they'd gotten their 2nd shipment.

Seems the guy was feeling around inside the nose, behind the firewall, and discovered that his model has a "weight" stuck in there. And the guy said it was fairly heavy. And he had to drill through the firewall to "get it out". Sounds strange to me and the clerk didn't know any more details.

Mine is ready to go.... today!!! (and looking out the window the wind looks to be dead calm) And it came out balanced with no nose weight, but that was after I put the battery as far up front as it'd go, and put the motor servo forward too. But the a/c did seem to come out heavier than I thought it would for the size. It is just over 5lb 12oz ready to fly, dry.

And I've silicone glued the tank in, so I don't have easy access to the lower reaches in that nose to see if mine came from Phoenix with pre-installed nose weight.

Any of you guys got a Phoenix Sukhoi .46 with access to the inside of the nose? Did y'all's come from the factory like that?
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Old 11-08-2005, 10:37 AM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

Yes, I ended up removing the slug. As I remember it was around 2 oz. With my plane I had dificulty getting the cg, I had to split the battery and move it as far back as possible. I flew it for about 8-9 months before the fatal. It was much more fun for me on the nose heavy end.
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Old 11-09-2005, 04:58 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

I am building mine now. It does have the weight. I really am not going to worry about it until I am balancing it. If it can still be balanced with it in I will not touch it.
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Old 11-13-2005, 08:21 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

It has the weight for a reason and that is the designer knew it would be needed to balance the plane with a .46 engine. I'm on my third one (see reviews) and I have never taken the weight out. I flew the first with a .52 Magnum 4-stroke and the latest with a .45 Super Tigre and they both flew great. They balance perfect and handle just fine so don't worry about the weight until the plane is done and then see how the balance is. Remember...Nose heavy survives, tail heavy dies.
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Old 11-21-2005, 12:15 AM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

Well this nose weight has now come to annoy me. I need to add 3oz of weight to the tail now.

I was able to get one flight in today before the sun went down. Took nearly all afternoon to figure out an engine problem.
The flight was a little bit harry whilst getting it trimmed.

Hopefully the rain will hold off tomorrow and I can get some real flights in.
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Old 11-21-2005, 09:27 AM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

After having flown my Sukhoi, the nose weight annoys me too. And what else annoys me is that the suggested CG location also seems to be wrong.

On my first flights, I had to dial in up trim for level flight. I had the balance very near the suggested "stable" location, but the sucker was so aerodynamically nose heavy it took a bunch of trim. After I got home, I ran the formulas to see where a decent static margin would put the CG and nuts! Their manual suggests what? 100mm from the leading edge at the root to 120mm. That's less than 4" to about 4.7". (But then the manual also says there is no down thrust and theres more down thrust than right thrust.)

My calculations suggested that about 4.5" would be a stable starting point.

I'm now using an extra large rx battery and it's back as far as the wires will reach. I did a quick estimation of it's balance effect back there, and it's 5 ounces just about balance the 2 ounces Phoenix hid in nose. I'm figuring that the a/c is about 5-6 ounces heavier than it ever needed to be and am seriously thinking about pulling my fuel tank floor to get at that weight. And that floor was epoxied in to give the firewall extra support and to give the tank decent support. And the tank is siliconed down.... arrrgggghhhhhh....

But hey, the a/c flies pretty good.
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Old 11-21-2005, 04:43 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

That was my first maiden flight. Usually let someone else do it. It was scary. But I got it dialed in ok. I am going to just live with the weight for now.
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Old 11-21-2005, 11:29 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

HMMMMM

I got one in the box downstairs. I think I'll go check and see if it has the weight.

I'd rather take the weight out and slap a bigger engine in it.[:-] No sense having dead weight up front. You can slap a bigger engine in it and fly it around at 1/2 throttle. Then if you need power in an emergency--you got it.
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Old 11-22-2005, 07:57 AM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

The fuselage has a huge amount of room. It would be dead simple to move everything forward of the CG in that thing.

I normally mount my motor control servo forward anyway, but never thought I'd need to stick the servo tray forward too. And would have done that in a heartbeat. And it would have been zero extra work since I make my own pushrods anyway. And the fuel tank takes up about 1/4 the room inside the nose too. So bottom line, everything could easily have moved forward, and if you figure the battery and all 3 servos ahead of the CG instead of behind..... I'd have had to add tail weight.... Nuts!

As it is, it looks to me like all I've got to do is pull the weight and I could move my battery back into the nose, and the sucker would balance ok. There are big pockets on either side of the fuel tank up there and the battery (surrounded in rubber) drops into one of them fine and sorta sticks in there thanks to the rubber.

One of the LHS clerks said that the weight is just a couple of lead balls and is at the bottom of the firewall on the inside. An area I covered over with thin plywood epoxied to the firewall and bulkheads (to support the tank better and buttress the firewall) and is now going to be very hard to access.
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Old 11-22-2005, 08:07 AM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

Hey rcpilet, let me know where it is and how much it weighs. I've about decided that if you find it, I'm going to pull mine by going through the firewall from the front. There is a "hot air tunnel" in the lower middle of the firewall so I'm guessing they put a lead ball on each side of that slot area.

By the way, I've got an OS .46ax on mine and it's got a TON of power. I've flown mine at about half throttle most of the time so far and it has still been FAST at that setting. And it's vertical does not suffer because all it takes is pushing the throttle stick to do it. I'm planning on trying out an 11.5-5 whenever the weather settles down. I've only flown it with a 6" pitch so far. Actually, I've got 3 different 5" pitch props I've carved out of 12-5s and am itching to see work. I think at least one of them is going to be the trick for this a/c. It's a tad bit fast on landing and I'm just getting back into RC after years off. So I think the 5" pitch will be good. And of course, I'm still pulling the idle down as the brand new engine proves it'll run slower and slower on idle. Once upon a time I wouldn't be flying a new a/c with an engine that didn't have sufficient bench running to be dead reliable on a low idle, but times change.
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Old 11-26-2005, 03:14 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

Here is an image of the lead weight added in the nose of Phoenix Models Su-31 at the factory
[link]http://image.rcuniverse.com/gallery/galleryimages/lg-32934.jpg[/link]
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Old 11-26-2005, 09:32 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

Thanks for that picture.

I never thought to look down there. It's on the cooling air tunnel directly below where the tank sits on bulkheads. I floored the bulkhead tank support opening with thin plywood to give the tank better support and to tie the firewall to the bulkheads to beef up the nose, and never looked at what I was covering up.

Have flown the sucker on 3 outings so far. Flew it today. And the sucker gives every indication that it's going to be a favorite. I wish the weight wasn't there, but figure it's not a big deal the way she flies.

I got her to float in on landing so slowly today that one of the field experts came running out to warn me I was going to stall it. We'd had calm all afternoon and he thought I didn't have any airspeed. Truth is I'd felt a breeze for the last couple of minutes and had checked the stall speed higher up before landing and felt she could have easily gone slower.

Thanks for the picture.
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Old 09-03-2006, 04:03 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

Hi All,

I took a short break during the assembly of my Phoenix Sukhoi Su-31 ; now I can not find my manual.
Can anyone tell me the recommended throws on the control surfaces ????


Thanks in advance!


Rick

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Old 09-03-2006, 04:48 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

Aileron 10mm up, same down
Elevator 11mm up, same down
Rudder 20mm left, same right

Jeez, I'm glad there were only 5 or 6 threads on the Sukhoi.
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Old 09-03-2006, 04:55 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

Thank you darock,

I just finished the balance on mine and was waiting to double check the throws before taking her out on her maiden.
Here is a pic... I will do the madien without the cowl.... should be fun :-)



Rick,
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Old 09-03-2006, 11:54 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

Be careful test flying without the cowl. Remember your cg will change with it on or off. Also, you could risk losing some rudder/elevator authority without the cowl. The big, flat firewall really creates alot of turbulance.
That being said...I love mine....great sport plane. I shoe-horned some 3 inch wheels in the wheel pants. Now grass take offs and landings are a breeze.
Good luck !
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Old 04-09-2007, 01:48 AM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

I have a .76 on mine straight from the factory, I just set mybattery pack as far back as I could and it flew great today. Maybe just a bit tail heavy if you are not used to that. I flew great though.
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Old 04-09-2007, 09:38 AM
  #18  
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Default RE: PHOENIX Sukhoi .46 nose weight ????

hey guys only some of these came with weight in the noise mine didnt and i put a os61 on the front end and hade to put battry in tail runner
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Old 04-10-2007, 12:07 PM
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Default RE: PHOENIX Sukhoi .46 nose weight ????

Don't fly this ship without the cowl. It becomes super elevator sensitive without and very hard to fly.
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