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Old Aug 17, 2012, 05:02 PM
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R.M. Gellart's Avatar
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Power System Trends-More Watts or Less

We have had a interesting week in a local club where a discussion started with the assumption that power systems for ALES ships are going to escalate and that the club needed to cut this trend off at the pass. The line they wanted to draw in the sand was at 1000W. I am not a power guru and I am flying a set up that was, part A, part B, and part C and I was ready, no real experimentation and the set up works just fine. The set up I used at the Nats in the Tragi is 300W, and it is very small and is more than adequate to get the job done for 70oz airframes.

My feeling is that if anything, as ALES and F5J progress, the airframes are going to get lighter and tighter concerning space and the power systems will follow the trend and get smaller too. This trend will lead to base airframe weights that may be even lighter than some of the lightest string launched sailplanes available.

Now, an undercurrent in all this is the fact that a few of these gents thought that they had a enclave from those bad guys who flew moldies in string launch contests. They have tried to shroud this issue as a safety issue, and no one else seemd to bite on that.

At this time, guys are flying Maxxs, Radians, homebrews, and a moldie maybe (a 95+ oz Supra). They feel that guys are going to buy power systems to fly to an out of sight downwind thermal they see. I have tried to tell them that in many cases flying straight away leads to a sailplane being tough to see and really tough to very exact with in your climb and final placement. Also, to get to 1000W, weight and space starts to become an issue too. At the Nats, I timed for one flier in particular with a large ship, that when flying straight away, it went stealth pretty quickly and he finally had to make corrections to the flight path just to see the ship. This info seemed to fall on deaf ears.

So, what be your thoughts?
Marc
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Old Aug 17, 2012, 05:30 PM
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United States, CA, Folsom
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Logic and sanity often falls on the deaf ears of those that are stuck in their ruts and have no interest in evolution.

The very premise of ALES (30 second max climb, altitude 100-200M) limits the kind of stupidity that your fogies are so afraid of. Fly too far away and you lose contact with what the plane is doing. This kind of tactic only seems to benefit those that don't have the latent soaring ability to find and use the lift that is almost always to be found near enough to be reachable by any reasonable power system.

Now a more reasonable approach might be to limit the watts/lb, so if someone really wants to fly a 1000 watt monster, they might be required to have a ~6.5-7 lb minimum all up weight. This is premised on 150 watts/lb as the maximum power to weight needed to quickly/easily get a sailplane to altitude for an ALES type event.

JT
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Old Aug 17, 2012, 07:11 PM
Always more to Xplore
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JT, would the watts/lb limit count the AUW before or after jettisoning an outboard super-launch battery pack? Just askin'...
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Old Aug 17, 2012, 07:17 PM
the flying is good
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Leave all that "/" stuff for the FAI. Keeps ALES simple.
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Old Aug 17, 2012, 07:32 PM
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Originally Posted by dephela View Post
Leave all that "/" stuff for the FAI. Keeps ALES simple.
Dennis, you know that's fantasy land. As soon as an event is born that becomes a contest, the optimization rush starts. It happened with HL, it happened with RES, it happened with J. ALES is no different, just newer.

JT
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Old Aug 17, 2012, 07:37 PM
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I think that the current rules for ALES do not really favor the higher watt setups. As previously mentioned you can only go so far up, cross or down wind before your ship starts to become invisible. I also believe that the closer you are to the designed weight of the ship that you have chosen the better it's going to fly. I only see one advantage to a high watt motor in ALES. You launch and climb out at ninety degrees with a motor/prop/batt setup that has a prop speed just shy of the models VMO and when you reach 200m and the motor cuts off you coast another 75m before beginning your glide. Your only limiting factor here is having to haul around all that extra weight that it took to get the extra altitude. Plus a good CD should see what is happening and put a stop to this type of launch since it violates the basic concept of ALES.
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Old Aug 18, 2012, 08:37 AM
Red Merle ALES
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Joined Apr 2002
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You can use up to three models in the current rules. So have the lightweight gas bag when the lift is light and the heavy ship when the lift is rockin'. However, they will find in very quick order that the high powered models won't be consistently competitive in the long run. I'll take my 9oz wing loading eSupra "Red Merle" and compete against the guys who can run downwind as far as they like and if they take the trophy home I'll by them a barley pop! It takes me 27 seconds to get to 200m with my power setup, so I can't run downwind at all! This is my experience after running just shy of a dozen ALES contests.

Curtis
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Old Aug 18, 2012, 09:55 AM
Flying = Falling (Slowly)
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Tulsa, OK
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For the most part this is a non-issue both for ALES and for F5J, probably less so for F5J than for ALES.

Since the first ZLOGS became available I have been both testing and using numerical models to figure out what role power levels might play in these kinds of events. There are two aspects to consider:

First, the concern about using power to extend the horizontal range of planes up to their specified launch altitude. This is absolutely a non-issue. Both testing and numerical models seem to confirm that 1000 watts in a full sized (3 to 4 meter) plane will allow a person to attain any ALES altitude at a distance that substantially exceeds the useful visibility range for these planes. I flew a 750 or so watt Supra which could be literally flown out of CONTROLLABLE sight in 30 seconds -- that is, the dot which I could see, could not be flown in a way to reasonably use lift if it was detectable.

Second, is the concern about using power to allow a glider to materially exceed its nominal cut-off altitude. This is a distinct reality. But one which is easily dealt with with our existing rules. Logs of my 750 watt Supra demonstrated that it would easily exceed its 200 meter cut-off altitude by 30 to 40 meters. My 450 watt Maxa exceeds its 200 meter cut-off by up to 20 FLYABLE meters. The Supra materially exceeds the 10 percent tolerance for ALES flying. And numerical modeling indicates that a 1000 watt Supra could exceed its shut-off altitude by 50 to 60 meters. Given that our nominal sink rates are in the range of 60 feet per minute it is clear that planes CAN gain a material altitude advantage with more power. When I started studying this problem a few years ago it appeared that the added weight of the higher powered systems would create increased sink rates that would offset or even more than offset the benefits of the added altitude. Since that time I have demonstrated to my own satisfaction that this is no longer the case. First, the advent of 65C batteries sized for a single launch have substantially reduced the battery weight. And secondly, experience with high performance motors has demonstrated to me that for 30 second and shorter motor runs, smaller frame (for example, the Neu 1100 series can be used in 1000+ watt applications where people are now using the 1500 series motors.) Right now, fairly optimized 500-600 watt power systems are coming out around 10 ounces. It is possible to design systems up to 900 to 1000 watts which weigh less than 14 ounces. THE DIFFERENCE IN SINK RATES FOR MORE POWERFUL PLANES IS NOT GOING TO COMPENSATE FOR THE ADDED ALTITUDE THEY CAN PROVIDE.

Is this really a problem? Not really. The CAM switch is perfectly suited for most of the planes we fly. But it is problematic for a high power plane to use a CAM type of device which cannot compensate for the high climb rate and/or which cannot measure actual launch height. But enforcement is nonetheless very simple and inexpensive. At its simplest, guys that fly high power planes can reasonably be expected to demonstrate that they are complying with the 200 meter limit by using one of the other devices which can either compensate for high launch velocities or which can read out real launch altitude upon landing. Whether or not one is interested in F5J flying, the devices that these planes use measure a real launch altitude as defined by the highest altitude attained during a period between the release of the plane and 10 seconds after the motor shuts off. The least expensive of these is the Sky Limit, which I think sells for $50 or $60 dollars. It is basically an ALES cut-off switch which can be set to a altitude and time settings like the CAM. In addition, though, it has an optional zoom algorithm which can compensate for high launch speeds and it has a very, very simple remote LCD readout which will furnish the actual launch height upon landing. WIth the Supra I had concerns about exceeding the maximum launch height tolerance and to ensure compliance I simply took the average real launch altitude of three or four test launches and reduced my set point by the amount by which I was exceeding the maximum launch height tolerance (in my case, 15 to 20 meters). So my Supra was set to shut off at 180 meters -- which it did religiously. I was able to verify my launch altitude after any particular flight by removing the canopy and plugging the remote LCD device in to get an instantaneous, accurate and direct readout of the real launch altitude.

Do we need to legislate more limiting parameters for ALES? I do not think so. Let guys put arc welders in the noses of their planes. Let them fly their planes beyond out of sight. Simply place the onus of confirming that you are flying within the altitude and time parameters on the shoulders of the individual competitor. It will require nothing of guys flying reasonably powered planes. And when a guy standing next to you with a plane that makes more noise than your lawn boy's weedwacker launches well above you, have the CD ask him to confirm his launch altitude.

As to where power systems will likely go, I am inclined to believe that they will generally settle out at less than 150 watts per pound. My Supra at 175 watts per pound had more than I could really take advantage of. My Maxa, at around 100 per pound doesn't quite have the poop into the wind that I would like to have -- I'll be moving it up to 125-140 before too long. Looking at F5J is kind of interesting. A lot of these planes are flying with fairly low power systems (I'm guessing in the 120 to 130 watt/lb range). I think a several things are in play here. First, they seldom launch to 200 meters -- more often to less than 150 meters. And second, you get thirty seconds of "run" time which counts as a part of your flight (just like ALES) -- why waste it with a rocket like takeoff? And finally, I suspect the better pilots are using slower launch velocities to facilitate their thermal searches while they are launching.

It may be that we will discover some advantage to powering our planes up as our experience with ALES progresses. But as long as everybody understands that 200 meters (or whatever) MEANS 200 meters, the guys who build planes to get around that parameter will ultimately discover that they are wasting their time and money.

Happy Landings,

Don
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Old Aug 18, 2012, 11:23 AM
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And excellent and well thought out post, Don.

As far as setting a watts/lb limit of some kind -- it seems like that would create quite an interesting enforcement problem, unless you rely on the honor system.

The Sky Limit device (of which I have 3) does address the altitude problem very nicely (as Don has mentioned) and can easily be checked after a competition flight by the person timing and whatever penalties (if any) can be applied.

If launches are only allowed upwind (until the motor cuts off, and enforced by some kind of "line judge") then there is no incentive to run downwind with the monster motor. After all, that's pretty much what we do in TD. After your zoom, go where you like. After the motor cuts off do the same. Or is that idea too much regulation for the ALES guys? Gonna range out upwind in speed mode? Have at it.

Okay. That's my 2 cents.

Preston

P.S. Don - are you moving to an 1107 for your Maxa? Just gathering data.
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Old Aug 18, 2012, 11:26 AM
Flying = Falling (Slowly)
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Tulsa, OK
Joined May 2004
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Quote:
Originally Posted by CloudyIFR View Post
You can use up to three models in the current rules. So have the lightweight gas bag when the lift is light and the heavy ship when the lift is rockin'. However, they will find in very quick order that the high powered models won't be consistently competitive in the long run. I'll take my 9oz wing loading eSupra "Red Merle" and compete against the guys who can run downwind as far as they like and if they take the trophy home I'll by them a barley pop! It takes me 27 seconds to get to 200m with my power setup, so I can't run downwind at all! This is my experience after running just shy of a dozen ALES contests.

Curtis
Curtis,

The advantage of more power is more likely to be manifested in the ability to launch into the wind on breezy days. It is useful to be able launch 400 or 500 meters into the wind on one of those 15 to 20 mph days. It gives you more working space to find and stay with lift as it moves downwind. My 750 watt Supra could go farther into a 20 mph wind than I could see or fly it and gave me a better chance to get back to the field as I was carried downwind. My Maxa can get to 200 meters in 25 or so seconds, but once the wind comes up over 10 or 12 mph, I am pretty limited as to how far I can launch into the wind.

The collateral benefit of being able to move further into the wind is that you can get away with a lighter wing loading (less ballast) for any particular set of conditions. Remember, most of our planes right now are flying at weights which are the equivalent of their TD nephews plus ballast. My Maxa is the first electric that I have flown which finished out at the same weight as its TD equivalent (and very low at that). Most electric flyers haven't gotten to the point where ballast is ever used. But when our flying weights approach the flying weights of typical TD planes, ballast WILL come into play. Its just that the more of the upwind field you fly in, the less ballast you may need in some conditions. (It seems that many of our TNT TD contests are flown in windy conditions with iffy lift, and many times the problem boils down to minimizing your sink while maintaining the ability to get back to the landing zone.)

Happy Landings,

Don
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Old Aug 18, 2012, 11:28 AM
Flying = Falling (Slowly)
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Tulsa, OK
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Quote:
Originally Posted by jaizon View Post
Don - are you moving to an 1107 for your Maxa? Just gathering data.
Yes.

And for my 2 cents, regulating watts/lb or something like that would be a fools errand.
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Old Aug 18, 2012, 02:04 PM
turn, turn, turn.
Athol, Massachusetts
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Quote:
Originally Posted by jaizon View Post
And excellent and well thought out post, Don.

As far as setting a watts/lb limit of some kind -- it seems like that would create quite an interesting enforcement problem, unless you rely on the honor system.

The Sky Limit device (of which I have 3) does address the altitude problem very nicely (as Don has mentioned) and can easily be checked after a competition flight by the person timing and whatever penalties (if any) can be applied.

If launches are only allowed upwind (until the motor cuts off, and enforced by some kind of "line judge") then there is no incentive to run downwind with the monster motor. After all, that's pretty much what we do in TD. After your zoom, go where you like. After the motor cuts off do the same. Or is that idea too much regulation for the ALES guys? Gonna range out upwind in speed mode? Have at it.

Okay. That's my 2 cents.

Preston

P.S. Don - are you moving to an 1107 for your Maxa? Just gathering data.
Yeah, if you can't launch downwind, why bother?
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Old Aug 18, 2012, 02:10 PM
turn, turn, turn.
Athol, Massachusetts
Joined Oct 2005
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Quite honestly, I think a downwind launch is the most relevant variable to this topic...
Until the rule is cleared up, and downwind launches are still allowed, high wattage rules.
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Old Aug 18, 2012, 05:47 PM
Flying = Falling (Slowly)
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Tulsa, OK
Joined May 2004
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Kenny,

As useful as a downwind launch can be, its usefulness is clearly influenced by the windspeed you are flying in. Guys like Darryl may launch downwind in 20 mph winds, but 99 percent of the rest of mortals worry less about getting downwind when the breeze comes up than they do getting back to the LZ FROM downwind.

In that context, I am not sure why power beyond a certain point really makes a difference in most planes' abilities to get downwind. My lower powered (maybe underpowered) Maxa can be flown under power to the effective limits of my visibility in any direction (even if the launch is into the wind) and to 200 meters when breezes are light (say, less than 5 mph). As the breeze picks up the downwind distance increases (to well beyond the limits of visibility) and the upwind distance decreases. Above 15 mph or so, the plane's upwind limit is very substantially limited and its downwind limit is well beyond the limits of my sight -- and likely in the lack of substantial lift, beyond the plane's ability to get back to the LZ.

While I would be reluctant to release my 175 watt/lb Supra in a downwind direction in 15-20 mph winds, I was easily able to release it into the wind at those speeds and fly to any point inside a disk defined by a 200 meter ceiling and the limits of my ability to see and control the plane. Even at 130 or 140 watts/lb all of the planes I have flown were easily capable of VTO and could fly anywhere within the "useful disk" that I wanted. And if there were limits to covering the "useful disk" they were always upwind rather than downwind.

Beyond these relatively modest power ratings, it is not clear to me what more power might buy me -- besides shorter motor runs and more flying time.
Finally, even my lowest powered plane, the Maxa, is easily capable of flying out of my hand in dead air without anything resembling a push.

If a person has all the power required to power a plane to the limits of visibility and to 200 meters, what will more power offer?

Happy Landings,

Don
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Old Aug 18, 2012, 07:54 PM
turn, turn, turn.
Athol, Massachusetts
Joined Oct 2005
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Yeah Don, I basically agree.

I wouldn't want anymore power than I have...about 1000 watts.

I sure do like the climb outs though.
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