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Phoenix Edge 540 .46 ARF

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Phoenix Edge 540 .46 ARF

Old 03-20-2021, 03:59 AM
  #51  
RICKSTUBBZ
 
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Originally Posted by Bknaws View Post
Have about completed the build and waiting on good weather to fly. I did several things to reduce weight -- smaller servos, carbon fiber landing gear and wing tube, removed a lot of wood from fuselage and motor mount area. Overall I saved about 8.5 oz and the plane ended up weighing 5 1/2 pounds. The wing loading end up being about 22.7 oz per square foot. Should be a good flier with the Saito 82. I plan to do the first flight with CG at 90 mm. Will post results after initial flight.
I look forward to the flight report.
8-1/2 ounces is a significant overall weight loss. Will definitely make a difference in the flight envelope.
Any pictures or details as to the wood removal?
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Old 03-20-2021, 07:29 AM
  #52  
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Default Weight reduction

Only about 1.25 oz of the 8.57 oz was wood removal. .42 of that was from the fuselage and most of that was from the motor mount structure. To keep the CG in the 95mm range I had to put the battery rlight behind the tank. So if you used a lighter engine than the Saito 82 you probably would have to move the battery up over the tank and maybe even add some weight which would negate the wood removal from the nose - so you might want to not fool with the weight reduction up front. The .35 oz removed from the turtle deck is probably worth the effort. It doesn't play any structural role so I just used a dremel sanding drum and made all the border and formers narrower. Also trimed as about 3/16 from the pilot's height. It is interesting that the literature says the weight range is 6-7 pounds. Even if I had built it to plans it woild only have been 6 pounds so I can't imsgine how it could be as much as 7 - maybe electrics with huge batteries. On the CG range I used the on-line calculator and the neutral point comes out to be 110mm and the recommended CG is 97mm. So I can see why folks on this thread found the recomended range of 80-85 terribly nose heavy. Later when I have the plane apart I will try to take some pics and post
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Old 03-31-2021, 06:04 AM
  #53  
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Default First Flight

Made my first flight Monday. I feel lucky to have survived the first flight. Almost was not controllable. The plane pitched up severely and required more down trim than was available. Somehow I was able to make a good landing and went home scratching my head. As I mentioned before the "on line" CG program suggested 97 mm with 5% margin with the neutral point being 110mm. The set up on my first flight was 94mm without fuel and 85mm with full fuel so should have been fine but sure exhibited tail heavy behavior. Has anyone out there used the on line program? I have used it for three scratch designs models and it seemed pretty accurate. I checked wing incidence and it is about + 1/2 degree relative to the horizontal stabilizer. Engine thrust is 2 degrees right and about 1 degree down. This all seemed reasonable. Any advice would be appreciated.
Old 03-31-2021, 12:14 PM
  #54  
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BKNAWS
I'm so glad you survived a wild maiden... From your spec's, you should have had a great flying plane.
I know you had trouble keeping it from looping, but could you tell if it was stable in pitch? On landing, did you notice if the tail dropped Or if she resisted flaring?
I'm not convinced that it is tail heavy and I sure wonder about the positive incidence being a factor.
If it were me, I would include all the down-trim you had during your maiden flight as your new center elevator position. Once you can keep it under control it will be easier to determine pitch sensitivity. As I'm sure you know, pitch sensitivity affects the elevator down as well as up.
If required, you would have four wing hole positions to patch and redrill. Not an operation I would look forward to.

Originally Posted by Bknaws View Post
Made my first flight Monday. I feel lucky to have survived the first flight. Almost was not controllable. The plane pitched up severely and required more down trim than was available. Somehow I was able to make a good landing and went home scratching my head. As I mentioned before the "on line" CG program suggested 97 mm with 5% margin with the neutral point being 110mm. The set up on my first flight was 94mm without fuel and 85mm with full fuel so should have been fine but sure exhibited tail heavy behavior. Has anyone out there used the on line program? I have used it for three scratch designs models and it seemed pretty accurate. I checked wing incidence and it is about + 1/2 degree relative to the horizontal stabilizer. Engine thrust is 2 degrees right and about 1 degree down. This all seemed reasonable. Any advice would be appreciated.
Old 03-31-2021, 08:27 PM
  #55  
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Default First Flight

Thanks for your thoughts. The plane was definitely very pitch sensitive. Due to your earlier comments I had even toned down the elevator deflections -- glad I did or I might not have survived. Even though is not tail heavy by measurement nor the cg calculator, I can't imagine it would have behaved so pitchy if not tail heavy. So I move the battery to above the tank. I will report back with results. May be a few weeks.
Old 04-01-2021, 06:48 PM
  #56  
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Default Ballance Point ?

Originally Posted by Bknaws View Post
Thanks for your thoughts. The plane was definitely very pitch sensitive. Due to your earlier comments I had even toned down the elevator deflections -- glad I did or I might not have survived. Even though is not tail heavy by measurement nor the cg calculator, I can't imagine it would have behaved so pitchy if not tail heavy. So I move the battery to above the tank. I will report back with results. May be a few weeks.
I appreciate you sharing your experience with this plane and will be watching to see the results after you make some changes.

Let me start by saying that my Phoenix 55” edge 540 is still in the box. But your situation got my curiosity up so I grabbed the box and pulled out the parts and did some measuring.

I have done a bit of experimenting with “balance points” on a few planes and have learned a few things both from reading and experimentation. Anyway, for the sake of conversation and thought, I will throw in my two cents.

I think the general consensus for a starting point, for the balance, is around 27% mean aerodynamic cord. Or would it be safe to say average cord? A couple of things that I have learned that will allow you to move the balance point more reward are; light wing loading and a large horizontal tail surface area. Also a flying stab (airfoiled stab) will also make a difference. Not to mention wing attributes can also play an effect on moving the balance point. The shape, airfoil thickness and so on.

I just realized, that as far as wing loading goes this thing is a PIG! So, I drew up the wing on my computer and calculating wing area including the area occupied by the fuse this airplane comes out to just over 557sq in. Using only the wing surface there is almost 485 sq in.

Taking what I now know about this plane I would start the balance point somewhere really close to 26% - 27%. At 27% I come up with 2.653” from leading edge shown in the first picture below. Using the second method that I have a picture of suggest 2.725” from leading edge

I know these are way off from what the manual says? None the less, when mine goes together I will use these numbers as a starting point and fine tune based on flight performance.

Here are pictures to support where I came up with the distance:


My initial calculation

This calculation is from some documentation that I have from way back when

Last edited by RICKSTUBBZ; 04-01-2021 at 06:54 PM.
Old 04-01-2021, 08:06 PM
  #57  
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Thanks for your thoughts. Yes, the number I came up with using the "on line" c.g. calculator was 560.16 square inches including the fuselage area which was pretty close to what you calculated. The MAC was 10.45 inches and it was 12.42 inches out from the center of the fuselage. I have used this calculator on several scratch designs and it has seemed pretty accurate. This program suggests 3.82 inches behind the leading edge with a 5% safety margin which is quite a bit further aft than your numbers or the recommended numbers in the kit. My first flight , however, suggests your numbers may be more correct! All the planes I fly are in the 18-20 oz per square foot. This plane, if I had built it without any changes would have been 96 oz which would be 24.68 oz per ft squared which made me uncomfortable. By using small servos, carbon fiber landing gear and wing tube plus a few other odds and ends I was able to get the plane down to 90 oz. So as I am testing it now it is 23.13 oz per square foot. Better but still a little higher than I would like. The latest article I read about this Phoenix plane (although it looks like a prior design with servos in the rear and a different color scheme) came out to be 129.6 oz which would be 33.32 oz per square foot!! The article said it was a highly loaded wing but said it flew okay which was a real surprise to me. Anyway, I will keep you posted on what I learn in the next several weeks.
Old 04-02-2021, 06:46 AM
  #58  
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RICKSTUBBZ, since I still had my balance rig set up I experimented a bit to see how much weight it would take to balance at 27% of MAC. Basically it took an extra 6 oz in the engine area to balance to the 27% C.G. So if you build to plans and don't go through the weight reductions that I went through the plane would end up being 102 oz. This would yield a wing loading of 26.22 oz per square foot which is pretty high. Even with my weight reductions it would end up at 96 oz or 24.67 oz per square foot which still seems too high. Anyway my engine is a Saito 82 which is pretty big for this plane and it weighs with prop 19.6 oz plus I have the battery on top of the tank which is as far forward as possible. So unless you have a much heavier engine it looks like you will likely be stuck with adding quite a bit of weight to the nose to reach 27%. Hopefully my experimenting will confirm that such a far forward C.G is not necessary. My next flight will be at 83mm (3.27") which is in the range Phoenix recommends but an amount others on this thread have found to still be too far forward. Hopefully my second flight will help point us in a good direction.
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Old 04-05-2021, 05:47 PM
  #59  
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Default Second Flights

Had two successful flights today. The plane is now performing like I had hoped. Even though the wing loading is 23.2 oz per square foot it is a real floater on landing with no indication of dropping a wing. Even though I haven't flown it much yet, I feel it is the nicest landing plane that I have. With the cg set at 83mm the plane is still toward the tail heavy end. For example it flies hands off inverted and when climbing inverted and cutting throttle it also continues on track. It is still a puzzlement that some folks are flying this model with a cg as high as 95 mm. Also the online cg calculator suggests 97 mm. We may never know the answer but I am convinced that if my cg was 95 or 97 mm it would not be flyable. In fact it almost wasn't flyable at 90 mm. If I learn more after a few more flights I will let everyone know. Thanks to those that offered advice along the way.
Old 04-06-2021, 02:18 PM
  #60  
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Bknaws,
Thanks for the update...I know it's a relief to get a baseline and a good flight out of it.
Does it groove well enough (at such a size) to pull off some quality IMAC routines?
Old 04-06-2021, 06:52 PM
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Up to this point the planes I have built and flown are more sport planes than precision airplanes. Although I flown a lot of hours and have put those planes through some violent maneuvers I have never been a very prcise flier. So I think this plane will improve my flying skills and at some point I may be able to answer your question. As I get more experience with the plane I will share what I learn.

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