Author Topic: Paul Walkers Impact at the the Nats (Read 7618 times)

Keith Renecle · « **on:** July 13, 2011, 01:18:49 AM »

Hi All, I was hoping that someone would make mention of the outstanding job done by Paul Walker at the Nats with his latest electric Impact. Congrats and well done to Paul for placing a close second behind Dave Fitzgerald. Dave and the Thundergazer are a hard package to beat, and I would love to hear from those present at the Nats about how Paul's electric package was working. It was obviously working rather well but it would be great to hear the nitty-gritty.

Maybe Paul can post the final set-up details for us as well when he gets a gap. I would really appreciate this. Thanks very much.

Keith R

James Mills · « **Reply #1 on:** July 13, 2011, 05:54:59 PM »

Keith,

I can't give you any specifics about his plane but I was able to watch a few of his practice flights Monday while we were at the beginners circle. I had a nice side view of where he was flying and the plane looked rock solid.

James

Keith Renecle · « **Reply #2 on:** July 14, 2011, 09:21:25 AM »

Thanks James, it must have been a treat to be there! PW is certainly one of the best fliers around and he puts a lot into his designs.........this is why I'm dying to hear some of the details!

Keith R

Paul Walker · « **Reply #3 on:** July 14, 2011, 08:40:53 PM »

Maybe Paul can post the final set-up details for us as well when he gets a gap. I would really appreciate this. Thanks very much.

Keith,
The motor was a Plettenberg Orbit 20-16. The ESC was a Shultze 18.46 F2B. The timer was the Will Hubin FM9R, and the battery was the Thunder Power 5S2600. The Prop was the 13*4.5 APC pusher. Plane weight ready for flight was 59 ounces.Wing area 650 in^2.

Since I returned home, I have changed the motor to the 25-14, as the plane wants more nose weight. Derek managed to see a flight with no additional nose weight, and it didn't penetrate the overhead very well with the aft CG. Adding nose weight, along with the correct tip weight and LO position fixed that issue.

Paul

Keith Renecle · « **Reply #4 on:** July 14, 2011, 11:59:49 PM »

Derek, Thanks for the candid opinion. I was talking to Peter Germann at the 2008 world champs and Igor was flying his Max 2 with the AXI 2826/12 setup. Peter remarked that the model certainly did not look like it had enough power in the overheads for the windy, turbulent conditions. Igor placed 2nd! I spent a lot of time with Igor over there and watched plenty of his flights. He had no problem with power at all. I also mentioned to Peter Germann that the apparent lack of power could be due to the lack of the engine sound. Let's face it........Dave Fitzgerald's PA .75 definitely sounds good and also powerful. Just by the way, Peter Germann is flying mostly electric these days. You really need to take Bob up on his offer to fly his plane. It is different, and "different" can be most interesting!

Paul, thanks for the feedback on your system. Just a few more questions for you:

What rpm range are you running in, and how much did this change from the coast to Muncie?
What is a comfortable lap time, and what length lines are you using?

As you know, we fly here in Johannesburg at 5000~6000 ft. ASL, so these details will be very useful. Percy Attfield has built an Impact with electric power and we are playing around with motors and props right now. Thanks again.

Keith R

Peter Germann · « **Reply #5 on:** July 15, 2011, 05:03:10 AM »

Quote from: Keith Renecle on July 14, 2011, 11:59:49 PM

...Just by the way, Peter Germann is flying mostly electric these days. ...

I flew PA.75's for a couple of years and I am now in the middle of my first e-power competition season. While far from stating E being superior, I'd like to define it being a) fully competitive and b) 100% predictable aka user friendly or reproducible.
Current setup for 702 in.sq / 63.5oz is AXI 2826/12. Phoenix ICE lite 75 A. Hubin FM-9, APC 13x4.5 EP, 5S2600 mAh.
lines 0.015 x 64 ft (eye-eye) 9'553 RPM 5.35 sec/lap 1'850 mAh used. (such as flown over last weekend in Landres (Turbulence City), France)
Peter Germann

Keith Renecle · « **Reply #6 on:** July 15, 2011, 07:52:39 AM »

Quote from: Peter Germann on July 15, 2011, 05:03:10 AM

I flew PA.75's for a couple of years and I am now in the middle of my first e-power competition season. While far from stating E being superior, I'd like to define it being a) fully competitive and b) 100% predictable aka user friendly or reproducible.
Current setup for 702 in.sq / 63.5oz is AXI 2826/12. Phoenix ICE lite 75 A. Hubin FM-9, APC 13x4.5 EP, 5S2600 mAh.
lines 0.015 x 64 ft (eye-eye) 9'553 RPM 5.35 sec/lap 1'850 mAh used. (such as flown over last weekend in Landres (Turbulence City), France)
Peter Germann

Hi Peter, thanks for adding your comments, and also the setup details. I need to get an APC 13 x 4,5 EP prop, because I'm puzzled by the lap times at 9553 rpm. My 12 x 6 in the Electron turns at 9100 rpm for 5,2 sec lap times on close to full length lines. I did not think that the extra 1 inch in diameter would make up that much in thrust for such a low pitch.

I still enjoy engines, but I don't think that I will compete any more with them in serious competitions. Just the sheer ability of electric power to put your model down, switch on and fly the same setting every time, is enough to convince me of its superiority over engines.

Keith R

Russell Bond · « **Reply #7 on:** July 15, 2011, 08:12:40 AM »

The 13x4.5 in undercambered, that's why it acts like a 5.5" pitch (approx).
However APC has changed the mold a bit at the root and now you need more revs to do the same lap speeds.
I think APC is going to address this problem soon.....I hope.

WhittleN · « **Reply #8 on:** July 15, 2011, 08:22:09 AM »

Keith
Before the known shortage of thin hub’d APC 13 X 4.5 EP props, I cut one down to 12” – it took an additional 550 RPM to get back to my 5.35 second lap time. I am now running the 13 x 4.5 EP at 9650 RPM on 66’ lines for a 5.35 lap. Wish I had that prop back now.
Regards
Norm

Keith Renecle · « **Reply #9 on:** July 16, 2011, 12:21:59 AM »

Thanks guys for bringing this thread back to where I started. I really just needed the info from Paul on his setup, rpm and lap times. I would like to hear about Bob Hunt's setup as well, seeing that his Crossfire is flying slower lap times. I learned a great deal about e-power when I started on my governor timer project, so the more data I have the better.

Flying a constant rpm setup always looks fast if you look at lap times, but Windy once said that you should rather time the whole maneuver then you will see very similar times from all of the power packages. There is no really perfect system around. I think that Igor has done huge amounts of research and development around an electric 2/4 break system, and it works incredibly well in ideal conditions......just like the glow equivalents. When flying in turbulence however, most times these systems do not work as well, and a constant rpm is a better option. At least you know what you've got!

To Derek, I share your frustration on trying to get judging closer to perfection. It is an ongoing story and it all comes down to us as human beings that are not perfect and have our own personal likes and dislikes. I have spent the last 14 years trying to provide judges with better training systems, and have had some frustrating times, but also some wonderful times working with some great people. Working with people like Peter Germann, Andy Sweetland, Igor, Keith Trostle and many others through the years has been a priveldge for me, and together we have fixed the FAI rules to the point where they are now at least technical correct as far as the maneuver shapes go. My next task is to complete the interactive judges training program that I started a few years ago. It was a little ambitious for me, because my enthusiasm was greater than my programming ability. Unfortunately, life got in the way when the global financial crises hit the world and I had to put that on the backburner for a while.

Ron Merril asked if there is a computer tracking system available for stunt. As far as I know, there isn't one, and when it does become practical and affordable, then I see this more as a judges training device initially. This is always a fun subject but it's not for this electric forum.

Keith R

Igor Burger · « **Reply #10 on:** July 16, 2011, 03:37:44 AM »

Quote from: Keith Renecle on July 14, 2011, 11:59:49 PM

Igor was flying his Max 2 with the AXI 2826/12 setup

... with teh 12x6 APC prop ... the same setup as I had last year in Gyula and those windy conditions was advantage for me ... well ... until the wind stopped

I went even to 11x5 3blade this year and I just right now went back from field with 9m/s wind and did not have any problems with 1800g heavy model. Czestochowa next week will be another wash machine so I am OK with that setup

And regarding that regulation - yes you are right, it works well in calm (I tested it and developed in winter in gym - so it is clear), but I needed to switch it off on Landres because of turbullence, I needed to make it less sensitive in Gyula as it started oscillate, but this year I have even newer software, I think it will work already, and if still not, we have plenty of years fron of us, it WILL work one day ... at least it will be better and better

... but we will see

Keith Renecle · « **Reply #11 on:** July 16, 2011, 07:56:56 AM »

Good luck Igor, I am always amazed by your innovations, so I am sure that we are all looking forward to seeing your results with the Max Bee. Enjoy!

Keith R

Paul Walker · « **Reply #12 on:** July 16, 2011, 05:36:05 PM »

Doug,
Thanks for the objective (well, as objective as possible) review of the electric planes. I was never able to watch all the plance, and obviously haven't seen mine from the outside.

Speed has always been a concern for me. At the NW regionals, I was flying at about 5.35 sec/lap. At home in Deer Park, flying mostly at a density altitude if 3500 feet, I was going about 5.4 sec/lap. However, when I got to Muncie, everything changed.

Well, there's more to the story. At the NW regionals I was using a 25-10 and things worked fine. Son after that contest, I went back to the "ranch" (Deer Park) and started immediately having overheating issues with the ESC. After several shut downs because of this, I switched back to the 20-16, and the heating issue was completely resolved. However, the plane didn't fly as well with 1 ounce less nose weight. After several switches back and forth between the 25-10 and the 20-16, I concluded is was simply the nose weight. I added clay to balance it and all was good (I thought).

Forward to Muncie. Early flights showed less than perfect penetration in the overheads (as we have heard earlier). Vertical performance was also acceptable, but not as good as home. After some adjusting, (tip weight, LO's, wing level) it was better. I added some extra noseweight and things were better. It was in the form of clay on the outside of the nose. Monday was appearance judging, so back to the motel and off with the outside clay. I intended to add it to the inside before appearance judging. Somehow I managed to forget. I flew the rest of the time being more tail heavy than I wanted. This also forced a faster speed to get the penetration in the wind I needed. That's how it flew it's competition flights. In the calm, it was matching David, but in the wind, it was less than perfect. I couldn't figure out why. On Friday night before the finals, I mentioned to Don (my coach) that I toiught I should add some nose weight. He didn't think it wise to be changing something like that at that time. I left it was it was.

After the finish of the finals, Bob Hunt had me fly his plane. His is balanced significantly more nose heavy than mine. It flew slower, but held out just fine. On the drive home it became crystal clear. I WAS flying too tail heavy, and it cost me. When I got home, I replaced the 20-16 with a 25-14. This combination worked much better, and once again feels like it did at the NW regionals. There are a few other changes I am going to make all in hope of making it present slower but more positive.

Your other comment about how the "lift" through the corners is sooooo true. For the life of me, I can't get them to turn like an IC plane. However, I still think my corners are "adequate" in terms of radius.

Once again, thanks for your comments. I intend to use this information to make this plane better!

Paul

Keith Renecle · « **Reply #13 on:** July 17, 2011, 01:10:17 AM »

Thanks Paul and others, this is very good info and just what I was looking for. On the corner issue, maybe Igor's new model with the small 3-bladed prop will provide some more good feedback. Igor mentioned to me how well this new Max Bee corners.

It could also be something to do with the governor being too solid as well. Maybe the IC engines loose a little more in the corners. I had some interesting feedback from Christoph Holtermann in Germany that has been playing with my governor timer on his model with a Jeti Spin esc. The Jeti has one of the best governors around, and Christoph tried my system on the Jeti with the governor disabled. He said that he could feel that my governor is not as fast as the Jeti in reaction time, but that he managed better bottoms with my system. Overall he was most impressed by my simple system. So maybe there is something in there to experiment with? You can lower the governor gain on some of the esc's like the CC Ice and possibly the Schultze as well. If anyone tries this then please post the results here.

My first tests with my external governor system were really interesting, and I can remember that on my 16 pole MVVS motor, the rpm would hunt quite a lot between the two extremes, but the model always felt very good through the pattern. It just sounded a little funny. It could be that my continuous "2/4" break was giving me a good average rpm I suppose.

I enjoyed Doug's comments (always do) about the model design for electric, and it sure looks like the nose length has to be increased over the engine designs. Thanks to all for their great feedback, and let's keep going!

Keith R

Dean Pappas · « **Reply #14 on:** July 18, 2011, 01:40:54 PM »

Hello All,
I hate having to take action like this, but almost anything that smelled of either judging or attack has been purged from the discussion.
If I used a heavy hand, I apologise.

take care,
Dean P.

Crist Rigotti · « **Reply #15 on:** July 18, 2011, 03:56:33 PM »

Thank you Dean.

Russell Bond · « **Reply #16 on:** July 18, 2011, 05:37:11 PM »

Thanks Dean.

PJ Rowland · « **Reply #17 on:** July 18, 2011, 07:20:52 PM »

I had a chance to fly consecutive flights of Bob Hunts Crossfire.

1st flight was a feel out session
2nd Flight was a complete Pattern.

I actually flew it in the same configuration Paul flew it in - slightly faster - it was a real eye opener. Its really difficult to have a conversation with someone about Electrics not having power or thrust once you have flown one setup properly.

It easily had the same power output of the larger motors. What impressed me the most - and was hard to get my head around was the lack of slow down out of corners. It FELT like it was speeding up , but in reality it was just remaining constant. A real eye opening experience.

I said to Bob afterward - It would have been great to fly Pauls setup to guage how 2 setups were. I was impressed with Pauls setup. and equally with Bobs, ( which I flew ) really only PW can comment accurately on how the 2 setups differ.

Dean Pappas · « **Reply #18 on:** July 18, 2011, 09:03:24 PM »

I get to say something about toy airplanes, Oh Boy!
Hi All,
Hi Keith,
Actually I think that nirvana lies in having both: lots of governor gain AND a very fast settling time to load transients.
The control bandwidth issue of often ignored, and I am quite certain it is key. This is what PJ encountered.
I have to chuckle when I hear about the airplane flying through the corner as a problem.
If you really want the slowdown then use less diameter and more pitch ... but in my opinion, that is not the right approach at all.
Yes, Igor and I have agreed not to agree on this one!

What you want instead is less flap and more elevator in the corners, which may not be ideal in the rounds.
Clever folks like Werwage and Berger have figured this out. Difference is that Igor's setup never jammed and made him skip heartbeats!
When you can rotate the plane fast enough to nearly stall it, then you will be thankful for instant added thrust that yanks the plane out of the corner with authority.

Sure, a momentary loss of airspeed will desensitize the airplane, but I suspect there are better ways to accomplish the same thing.

Fortunately, there is more than one way to skin the proverbial cat.
I'd love to see very different setups evolve: we are all wired just a little bit differently.

Regards,
Dean P.

Keith Renecle · « **Reply #19 on:** July 19, 2011, 12:33:16 AM »

Hi Dean,
Thanks for "fixing" this thread! As usual, your comments are most objective, and come from years of experience and a darn good understanding of these technical things. I think that your last line sums it all up very well when you said "I'd love to see very different setups evolve: we are all wired just a little bit differently."

I once asked Yuri Yatsenko (clever chap) what makes his models fly so well and lock in and out of corners so solidly. He replied "the answer is simple......EVERYTHING!" He then explained the importance of "everything" that had to be in balance and work together at the same time. Engine, prop, alignment, balance, weight, handle setting etc. etc. etc......! He also mentioned personal preference and flying style. I think that we all agree 100% that a good solid engine run is the one common factor that can make or break a good stunt performance, and here electric rules as far as being able to change the setup to suit our different flying styles. I had a bunch of Yuri's Retro 60's but I did not enjoy the funny vibration and hard 4-stroke. I never liked the idea of tuned pipes (sorry Dean) although they work very well. I just don't see the point of the long pipe running through the model and also the expense of the system with the special props and all. I tried 4-bangers (Enya 53) as well, and although they do indeed run at a constant speed, I found the brrrrrrrrrrrrrrr coming down the lines irritating.

The nearest engine to electric that I played with for a long time, was the diesel. Good solid constant speed and smooth running (not PAW's!!). In fact, I would say that they are the closest thing to running electric. When it comes to finding good fuel, plus the pong and goo.....well that's another story! Nothing compares to electric right now, especially with the availability of plug n' play systems, cheap props and cheap(er) batteries. In fact..... here is a statement of fact. Never before in the history of stunt, has it been so easy to find a power package that allows anyone from beginner to expert, to fly stunt so well and so easily!

What to me is so great is the sharing of info in the stunt community on forums like this. This is how we develop and learn. The flap/elevator and prop/diameter/pitch debates will always be a part of this crazy sport of ours. This is what makes stunt so much fun. Imagine if there was only one design and setup that was really vastly superior to all others?? How boring!

Thanks to all for the info on Paul and Bob's stunters. My Electron flies o.k. at a maximum of 5.2 secs/lap. I would like to fly a little slower but up here in Johannesburg SA at 5000~6000 ft. the air is a little thin. I'm using an APC 12 x 6 EP prop turning at around 9100~9200 rpm and the model weighs too much at 1810 grams (64 oz). My latest design should weigh no more than 1600 grams so this will be interesting when I get it going.

Keith R

Dean Pappas · « **Reply #20 on:** July 19, 2011, 07:49:09 AM »

Hi Gang,

Paul,
if you would, please talk a little bit more about this "flying through" versus rotating through the corners issue.
maybe we can sneak up on some underlying fundamentals, here.

Dean

Doug Moon · « **Reply #21 on:** July 19, 2011, 10:23:10 AM »

One thing puzzles me about the electric setup. The prop. Most will agree the correct prop is a major part of getting the plane to fly exactly how you want it to fly.

For years in IC setup Carbon props were an absolute necessity due to the fact they would not flex under heavy loads and give up performance, especially at the tips. Anything less than carbon just wasnt going to cut it. And in many cases wasnt even considered.

Now we see electric rigs flying with APC electric props. Those are thin and flexible, especially at the tips. In heavy loads and in heavy winds this will show up and the pattern will suffer. Is it because the prop producers are not making pusher props at this time?

What gives....?? What am I missing??

Doug Moon · « **Reply #22 on:** July 19, 2011, 10:47:45 AM »

Quote from: Dean Pappas on July 19, 2011, 07:49:09 AM

Hi Gang,

Paul,
if you would, please talk a little bit more about this "flying through" versus rotating through the corners issue.
maybe we can sneak up on some underlying fundamentals, here.

Dean

Flying through the corner is just that... "Flying" through it. You know all about the pipe setup.

For example RWO, when the pipe setup is really working well on the way down you can hear the pipe shutting the engine down some, from inside the circle it almost sounds like it is shutting down. Then when you give control for the exit it throws on the brakes while the engine is slowing from the pipe regulation. It "appears" to "swing" the tail around a certain point, the CG. Now the engine is loaded and the rpm is below the pipe setting and it starts to release and the rpms begin to go up. At the same time you release control to level to exit the maneuver. The rpms come back up and you fly away from that point. When the plane is trimmed properly and the motor setting is correct the corner is a "non-event"

In the 4s and more so in the electric setups (electrics that I have seen, a small amount but some of the really good ones at that) you dont get this stop and start "appearance" in the corner. The corners are blinding for sure with electric setup but it can look very violent at times. In some cases I saw the plane "appeared" (that is a keyword, appeared) to speed up through the corner. The corner looks noticeably different than the IC powered model.

I think PW touched on it a bit too. I know some others watching noticed the same thing.

PJ Rowland · « **Reply #23 on:** July 19, 2011, 11:03:39 AM »

Doug :

I asked Bob Hunt the EXACT same question about the props, his answer was simple.

They dont really exist yet. Reverse pitch is one of the advantages of electric setup, noone is doing a good solid reverse pitch carbon prop.

Dean Pappas · « **Reply #24 on:** July 19, 2011, 11:58:59 AM »

To add to what PJ said: when the very stiff, low rotational inertia hollow-bladed carbon pusher props materialize, you will notice the difference.
Dean P.

Thanks Doug, though I did get that much. I was more interested in the subtle "at the handle tangibles" rather than the physics.
That's where I suspect that the problem statement is to be found.
My first data point is a complaint about too much sensitivity coming out of the corner.
More Input! Need More Input!

Dean

Paul Walker · « **Reply #25 on:** July 19, 2011, 02:54:08 PM »

After returning from the Nats, I tried several other props I had to see how they worked (again, because of this "flexibility" issue with the APC's).

I tried the carbon version of the Yatchenco prop that I had used for several years on electrics. It pulled well, cornerec well, but made much more noise in the corners than the APC 13*4.5 pusher. Of course, being a tractor, it made the noise on the insides, versus the outsides for the pusher.
I then tries and APC 12*6 tractor. I have heard that others have used this prop. I found no improvement in corner, and in fact it tracked worse than the 13*4.5 APC. It also lost tension in the overheads. It was clearly not as good of a prop on my plane as the 13*4.5. The interesting thing was that these other two props didn't change the corners much.

A tear previously, I had tried a 11.3*4.0 Bolly on the same plane. It slew fairly well, was overall quieter, but the corners if anything were not as tight!! That was a big surprise to me. In my IC days, diameter was the number one factor in determining the corner radius. Small changes in diameter were easily felt.

Then (back to being after this years Nats) I put the 13*4.5 APC pusher back on and the improvement in the total package was noticable. This APC prop works very well! I have a few more 3 blade carbon props to try, but doubt that they will be the answer.

Just like Dean mentioned, I have sped up the elevator and added nose weight. This way I am getting the best of both worlds: Better corner and smooth rounds. More experiments here in the coming months as well.

In terms of the corner, the IC planes "look" like the fuselage rotates first then lifts up through the corner. I think this fools the eye into thinking the corner is tighter. The electrics seem to lift first and then rotate. This is the effect I believe we are talking about.

The question is :Why? Why do these two different systems "appear" to fly through the corners differently? Well, the prop is spinning at "about" the same speed, ther planes are flying at about the same speed. The only difference is that the power being delivered to the air from an IC engine comes in pulses once every revolution, where as the electric is 10ish times a revolution.

That's my guess.

Paul

Dean Pappas · « **Reply #26 on:** July 19, 2011, 04:02:52 PM »

My first guess (and it's only a conjecture) is that the time lag before the added torque returns is less with a fast governed electric.
Dean

ptg · « **Reply #27 on:** July 19, 2011, 04:04:41 PM »

Now that this thread has morphed into something informative, here are a few more observations. Since I just got home from flying things are still fresh in my mind. First props, corners and tracking. Elroy now has 120 flights with a variety of props and two different motors (Eflite 25 & Plettenberg 20-12). I have tried many props including some wooden electric props. There have been tractors and pushers of different sizes and pitch. The one prop I keep coming back to is the APC 13 x 4.5 original thin blade pusher. One thing I have found that helps soften the corners a bit is to put a layer of .02 oz. carbon veil on both sides of the prop. I just sand the blades lightly with 320 and apply the carbon with thin CA. The best way to finish is to apply several coats of CA it usually takes me 3 to 5 coats sanding between coats with 220# until you get a smooth surface. This procedure will stiffen the prop and make it slightly thicker while maintaining the under camber. It will require more RPM to achieve the same flight speed. How much depends on the airplane so just keep turning it up until you get the desired flight speed. For me that's 5.35 to 5.4 lap speeds. The prop will sound different in both level flight and during maneuvers. It will track well in rounds and give a more pleasing and controllable corner.

Today I was flying American Pi. Although it looks similar to Elroy they are two very different airplanes. Pi’s corners are crisp but very smooth and lock very easily. Elroy has a bit more attitude.

Just a few observations here. IMHO, because electric is such different power from IC, it warrants some design changes. There are many in both Pi and Elroy. A couple of design changes you might find advantageous to virtually any good IC design are increasing the overall stab area and reducing the aspect ratio of the entire tail plane (elevator and stab). High lifting airfoils, lower aspect ratios, smaller flaps, longer tail moments, increased aft fuselage area are a few of my favorite electric things, but that's just me sitting here after a very productive and pleasant day of flying.

Allan Perret · « **Reply #28 on:** July 19, 2011, 04:23:07 PM »

Stiffer prop=softer corner.
I believe it, I just dont understand.
Whats the explanation ?

PJ Rowland · « **Reply #29 on:** July 19, 2011, 10:30:03 PM »

Quote :

" The question is :Why? Why do these two different systems "appear" to fly through the corners differently? Well, the prop is spinning at "about" the same speed, ther planes are flying at about the same speed. The only difference is that the power being delivered to the air from an IC engine comes in pulses once every revolution, where as the electric is 10ish times a revolution.

That's my guess. "

That seems to be the answer also from everyone else I've spoken too.

It is certainly noticeable difference between the exit speed of the ship from EL to IC. With El being far better.

Without a doubt Pauls Impact did the sharpest corners I've ever witnessed.

Howard Rush · « **Reply #30 on:** July 20, 2011, 09:26:32 AM »

Quote from: ptg on July 19, 2011, 04:04:41 PM

A couple of design changes you might find advantageous to virtually any good IC design are increasing the overall stab area and reducing the aspect ratio of the entire tail plane (elevator and stab).

Under construction at JCT North as we speak.

Oops (edit). I thought you wrote increasing the aspect ratio, which makes the tail more effective if it's stiff enough.

When you talk JCT, you talk stiff enough.
It's not just our stabs that have the right stuff.

Mark Scarborough · « **Reply #31 on:** July 20, 2011, 10:14:51 AM »

Quote from: Howard Rush on July 20, 2011, 09:26:32 AM

Under construction at JCT North as we speak.

interesting, similar Ideas to what is occuring at the Cougar skunk works currently as well,, hmmm

Dean Pappas · « **Reply #32 on:** July 20, 2011, 11:59:52 AM »

Hello All,
Phil,
The thicker blades on the last generation E-props from APC are the direct result (at least in part) of my flying buddy Dave Lockhart doing exactly the same with light carbon cloth on his F3A props. Think 20-1/2 X 14 and the like. The reduced flapping and ugly noises in corners and snap rolls came with twin benefits: reduced noise and reduced power consumption! Blade resonances are noise makers and energy wasters. The added weight did worsen the gyroscopic issues, however. The hollow bladed carbon near-clones of the APC E-props are in high demand in F3A despite their price!

We will, no doubt, evolve a similar direction.
Dean

Howard Rush · « **Reply #33 on:** July 20, 2011, 12:01:26 PM »

Quote from: Keith Renecle on July 17, 2011, 01:10:17 AM

Thanks Paul and others, this is very good info and just what I was looking for. On the corner issue, maybe Igor's new model with the small 3-bladed prop will provide some more good feedback. Igor mentioned to me how well this new Max Bee corners.

It could also be something to do with the governor being too solid as well. Maybe the IC engines loose a little more in the corners. I had some interesting feedback from Christoph Holtermann in Germany that has been playing with my governor timer on his model with a Jeti Spin esc. The Jeti has one of the best governors around, and Christoph tried my system on the Jeti with the governor disabled. He said that he could feel that my governor is not as fast as the Jeti in reaction time, but that he managed better bottoms with my system. Overall he was most impressed by my simple system. So maybe there is something in there to experiment with? You can lower the governor gain on some of the esc's like the CC Ice and possibly the Schultze as well. If anyone tries this then please post the results here.

My first tests with my external governor system were really interesting, and I can remember that on my 16 pole MVVS motor, the rpm would hunt quite a lot between the two extremes, but the model always felt very good through the pattern. It just sounded a little funny. It could be that my continuous "2/4" break was giving me a good average rpm I suppose.

I enjoyed Doug's comments (always do) about the model design for electric, and it sure looks like the nose length has to be increased over the engine designs. Thanks to all for their great feedback, and let's keep going!

Keith R

Hmm, synthetic induced drag. You could vary it as a function of wind speed, maybe with a beta vane.

Howard Rush · « **Reply #34 on:** July 20, 2011, 12:06:25 PM »

Quote from: Dean Pappas on July 20, 2011, 11:59:52 AM

...hollow bladed carbon near-clones of the APC E-props...

You don't say. How do they make them?

Dennis Toth · « **Reply #35 on:** July 20, 2011, 12:39:19 PM »

SOOOOO, if we go back to the old Top Flite bendable nylon prop we should have an instantaneous 90 deg corner that stops the forward motion of the ship for an instant then rockets it out as the blades spring back. AH HA, that's how those guys did it in the 60's.

OR

You can build the hollow CF prop by molding two half (top side then bottom) then filling the hub with chopped CF and bond the top and bottom half of the prop. Lots of work as the matting edges need to be perfectly flat. Some have built these and filled the blades (not the hub) with foam or put spars down them using CF tow. Seems we could take a Pusher Zinger wood prop kit and come out with any shape we want to see how the stiffness impacts the flight performance, just need to sand in the undercamber.

Best, DennisT

PJ Rowland · « **Reply #36 on:** July 20, 2011, 05:50:45 PM »

I would like to see 4 blade E flight style Carbon props with aggressive Undercamber. very narrow blades.

Dennis Toth · « **Reply #37 on:** July 22, 2011, 01:22:01 PM »

Paul,
You mentioned that Bob was slightly more nose heavy then were you balanced your ship and that you think yours might be tail heavy. What % of the MAC are you balanced at and were will you move it to?

Best, DennisT

Dean Pappas · « **Reply #38 on:** July 22, 2011, 02:04:44 PM »

Quoting ... "SOOOOO, if we go back to the old Top Flite bendable nylon prop we should have an instantaneous 90 deg corner that stops the forward motion of the ship for an instant then rockets it out as the blades spring back. AH HA, that's how those guys did it in the 60's."

What about an electric-style folding prop?
I suspect that you will find the noises that a folder makes during a corner to be very disconcerting.
Has anyone already tried it?

Dean P.

Paul Walker · « **Reply #39 on:** July 22, 2011, 07:08:05 PM »

Quote from: Dennis Toth on July 22, 2011, 01:22:01 PM

Paul,
You mentioned that Bob was slightly more nose heavy then were you balanced your ship and that you think yours might be tail heavy. What % of the MAC are you balanced at and were will you move it to?

Best, DennisT

OK, slightly is a kind way of putting it. It was by the feel of the plane, not by measuring.

Mine balances at 13.6% of MAC. This is VERY far forward of anything else I have had. However, this plane also has more sweep than my others.

I am guessing that I might sneek it forward another 1.5%.

Paul

Keith Renecle · « **Reply #40 on:** July 23, 2011, 12:46:10 AM »

Hi Paul, It would be interesting to see a basic outline 3-view of your new Impact if you wouldn't mind posting it. Looking at Igor's new Max Bee, the CG is also very far forward, but just like your model, the Max wing has a lot of sweep. If you build another one the same, will you make the nose longer?

Keith R

Crist Rigotti · « **Reply #41 on:** July 23, 2011, 10:24:06 AM »

Quote from: Paul Walker on July 22, 2011, 07:08:05 PM

OK, slightly is a kind way of putting it. It was by the feel of the plane, not by measuring.

Mine balances at 13.6% of MAC. This is VERY far forward of anything else I have had. However, this plane also has more sweep than my others.

I am guessing that I might sneek it forward another 1.5%.

Paul

Paul,
I was surprised that you are flying at such a forward CG of MAC. I thought that the closer we fly to the 25% MAC the less difference the weather, read wind, has an effect on how the plane flys. It would be very interesting for me and others as well as to why you choose to fly that far forward and even considering going further. Flight characteristics, windy vs calm, etc. I understand that LE sweep will move the MAC further aft form the LE of the wing, but what has sweep have to do with flying with a forward CG? Thank you in advance for taking the time to share your thoughts.

Dennis Toth · « **Reply #42 on:** July 23, 2011, 04:53:09 PM »

Guys,
I tried the forward CG on my ship this morning (a modified Tutor II profile) that has a rather normal sweep to the wing. Up to now I have been flying with the CG around the 23% - 26% point. I always had a little bounce off the bottom of my squares and pull outs. I attributed it to lack of practice and worked on control ratios and prop size. I was appling pipe setups/trim to electrics since this was the current trend.

Although both Paul and Bob H have said that the electrics seem to handle more forward CG placement I was skeptically that it would work on convert ships. Well, I was pleasantly surprised when I trying this setup. My profile ship has the battery mounted through the fuse in a slot with a outside support that allows it to be slide for and aft to adjust the CG. In the past I would move the battery 1/4" or so rearward to see were the ship would turn the hardest. Looking at what Paul indicated I checked how much I could move the CG forward with the slot I had. I move the battery all the way forward about 1 1/4" from the normal position. It moved the CG 1/2" forward to about the 16% MAC point. The first flight was in the claim light winds ~5mph, it took a few feet more to lift of but once in the air it was evident that it was very solid. As I began the pattern it just felt great. It turned smoothly and the bounce at the bottom was gone. I was impressed. On the next flight I changed props to slow the ship to a 5.3 sec lap time from 5.2. Again it was solid and smooth. By the third flight the wind came up to 12 mph plus. In the wind it was still smooth and again I was surprised how good this worked. At this point I didn't trim the leadout position and think with a little adjustment it will be even better. I can't move any further forward without modifying the fuse so I may try to add clay just to see what the limit is. If someone else can try this it will be interesting to hear your results.

Best, DennisT

Paul Walker · « **Reply #43 on:** July 23, 2011, 05:23:13 PM »

Quote from: Keith Renecle on July 23, 2011, 12:46:10 AM

Hi Paul, It would be interesting to see a basic outline 3-view of your new Impact if you wouldn't mind posting it. Looking at Igor's new Max Bee, the CG is also very far forward, but just like your model, the Max wing has a lot of sweep. If you build another one the same, will you make the nose longer?

Keith R

I don't have the outlines available at this time.
When (not if) I build the next one, the nose WILL be longer, and have the lighter motor in it.
I have found that as the CG moves forward, the better the penetration into the wind it has. (That alone should have signalled something was missing early on at the Nats!).

Paul

Doug Moon · « **Reply #44 on:** July 23, 2011, 07:37:09 PM »

This is exactly what I was talking about in my earlier posts about electric thoughts on design.

Typical stunt stuff probably wont apply. 25% tail sections and mac at 25% I dont think will be the ideal envelope...I could be wrong but then again...

The motor is just not doing the same thing (no gyro effect) and causing the same trim issues we have with IC motors. You guys are into a whole new world.

I envision, significantly longer nose moments, slightly longer tail moments with small tail sections. Maybe even very small stabs with larger elevators with large counter balances. All the stuff considered a little unstable or hard to work with in IC stunt planes might be awesome for the electric stunt plane as the delivery of power is going is more linear and isnt fighting itself with a counter balanced crank creating directional gyro.

Just my thoughts on it......

Its going to be interesting for sure. I cant wait to see more.

PJ Rowland · « **Reply #45 on:** July 23, 2011, 08:37:24 PM »

Doug : You mean like an Ares?

I did'nt feel pauls lacked penetration in the flyoff.

Keith Renecle · « **Reply #46 on:** July 24, 2011, 12:39:59 AM »

Quote from: Paul Walker on July 23, 2011, 05:23:13 PM

I don't have the outlines available at this time.
When (not if) I build the next one, the nose WILL be longer, and have the lighter motor in it.
I have found that as the CG moves forward, the better the penetration into the wind it has. (That alone should have signalled something was missing early on at the Nats!).

Paul

Thanks Paul. It looks we are in for some interesting new info in the coming months, so we are rather fortunate to have top fliers like yourself putting in this sort of R & D.

Keith R

Dennis Toth · « **Reply #47 on:** July 24, 2011, 06:36:42 AM »

Doug,
Adding to your comments it seems if we ECL's can handle the forward CG location it will allow getting the battery up in the traditional tank location in front of the wing without cutting the leading edge or planking that will allow in-line vertical CG and a lower mounting of the motor thrust line, i.e. "all in-line" layout. This would make the roll trim less affected by wind and airspeed if you start with a straight wing. Lots to consider.

Best, DennisT

Dean Pappas · « **Reply #48 on:** July 28, 2011, 11:59:33 AM »

Quote from: Howard Rush on July 20, 2011, 12:06:25 PM

You don't say. How do they make them?

Hi Howard,
Sorry for the delay, but I did a little checking.
The hollow carbon props are laid up as separate shells (face and back sides) using carbon cloth.
The face and back halves are joined with mulch at the edges and with unidirectional glass and carbon to fill the hub.
Unidirectional fibers also run out at the airfoil high-point to maybe half-span.
Props are balanced, post molding and joining by poking a tiny hole in the face at half-span and squirting filled resin into the light blade.

Dean

John Witt · « **Reply #49 on:** July 28, 2011, 12:43:10 PM »

Quote from: Paul Walker on July 23, 2011, 05:23:13 PM

I don't have the outlines available at this time.
When (not if) I build the next one, the nose WILL be longer, and have the lighter motor in it.
I have found that as the CG moves forward, the better the penetration into the wind it has. (That alone should have signalled something was missing early on at the Nats!).

Paul

Paul, is what you are alluding to a change in the longitudinal polar moment ( about the spanwise line through the CG)? As the polar moment is larger, the time constant for pitch disturbances would also become longer. Then, of course, you need more effective controls to make the same turn radius, assuming lift and mass stay constant.

It's the old trade-off that manuverablility and stability are opposites.

John