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Old Apr 21, 2012, 09:05 AM
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Originally Posted by Tuomo View Post
Yes, that is important the excisting Xplorer owner - many of them.

What I am really interrested in is the way Xplorer2 penetrates. Based on what I have heard from those who already fly Xp2, the difference is not radical. But if it places the Xp2 half way between Xp1 and Aspire, it is an important improvement in acive air with strong sinking areas and in strong winds.
I watched my team mates on the Canadian team test that airframe out and they both said that it moves well. Areend Borst and Keith Thompson both had good things to say about it.

I dont think its going to move as well as the aspire and quite frankly I dont need it to. After flying an aspire a few times I think it gives up too much for its penetration factor and I dont want to be on that side of the curve with the MkII.
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Old Apr 21, 2012, 09:42 AM
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I dont think its going to move as well as the aspire and quite frankly I dont need it to. After flying an aspire a few times I think it gives up too much for its penetration factor and I dont want to be on that side of the curve with the MkII.
The trend in F3J has been towards faster and more slippery designs. My prediction is that in coming years this will continue hand in hand with improving construction techniques.

With latest ST-structures Xplorer 1 was evolving to the edge of being too light, hence lacking in ability to move and fly tactically (without ballasting). I really have great expectations on Xplorer 2. It seems to be a much needed update of a basically solid performer. Fits my flying style, I hope.
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Old Apr 21, 2012, 11:26 AM
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Originally Posted by Tuomo View Post
The trend in F3J has been towards faster and more slippery designs. My prediction is that in coming years this will continue hand in hand with improving construction techniques.

With latest ST-structures Xplorer 1 was evolving to the edge of being too light, hence lacking in ability to move and fly tactically (without ballasting). I really have great expectations on Xplorer 2. It seems to be a much needed update of a basically solid performer. Fits my flying style, I hope.
I dont agree on the weight issue...that defies the direction the manufacturers are mvoing - 18 months ago people were posting that the "perfect all around weight" for a contest ship was 2200 gr!

Last years ST variants were in the mid to upper 60's 1845gr-1930 If that was on the border of too lite then we are overboard now and everything is useless!

This years MK II are going to be closer to 1600-1760 so if last years models were close to being too lite then EVERY manufacturer is going i the wrong direction ? Every manufacturer seemed to make the same mistake? I dont think so. I think they know that as I have said all along there are a lot of benefits to a lite model. The new airfoil being faster is def a good thing and I am excited to know its coming to a shop near me soon!

- Maxa's are in the low 50's to 60 oz - Pike perfection low 60's - Agida - 60 oz - nope I cant agree on the weight factor there. If it was that bad you would not see models coming out this lite...

IMHO and the opinion of others that I respect the penetration issues on the Xplorer had much more to do with a LOT of molded camber. The new wing does not have this feature to the same extent I am told.

Even with the old wing if you tuned it properly it would penetrate quite well but it required that the pilot stay ahead of the model in potentially sinky conditions. I have beat pilots (better pilots than myself) who were flying the Aspire with an unballasted 4.0 in windy conditions last season...zooming around and penetrating is all fine and dandy but its flight time we want. If you dont get to lift because its not there...then allyou get is the mileage award
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Old Apr 21, 2012, 12:03 PM
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This topic is worn out... Maybe we get to it after SA WC. Last years Euro Champs in Bovec were little special case, very hot and low winds.
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Old Apr 23, 2012, 08:33 AM
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Not so quick Tuomo stick around.
David I am very interested in your comments and obsevations.
I know that there has been a tremendous endeavor by sailplane manufacturers to build lighter airframes. From your experience and thinking on the subject of F3J model perfomance? Please explain how you would go about deciding a model is too light, taking structural considerations out of the equation. And how would you decide that your model was too heavy? If you could have your wish from Nicholy and you could get that EX2 at whatever weight you ordered, what would that ideal weight be. I amhaving a very difficult time believing that you kicked ass on Aspires in the same air...If they were out running you it was because they were not setup properly or in float mode...LJ
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Old Apr 23, 2012, 10:29 AM
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Originally Posted by Larry Jolly View Post
Not so quick Tuomo stick around.
David I am very interested in your comments and obsevations.
I know that there has been a tremendous endeavor by sailplane manufacturers to build lighter airframes. From your experience and thinking on the subject of F3J model perfomance? Please explain how you would go about deciding a model is too light, taking structural considerations out of the equation. And how would you decide that your model was too heavy? If you could have your wish from Nicholy and you could get that EX2 at whatever weight you ordered, what would that ideal weight be. I amhaving a very difficult time believing that you kicked ass on Aspires in the same air...If they were out running you it was because they were not setup properly or in float mode...LJ



Larry you flatter me...and trap me at the same time! Thanks for that!

It should be you who tells us your perspective. Ill post mine which is based in relatively short experience and no aero engineering background. Its less technical and more common sense.

Where is Ben C in this thread anyways - he always has the most intelligent posts.

I won't comment on the setup of the competitors planes. My point in making the comment was that so much leverage was being placed on an airframes ability to penetrate well and the aspire does that however in more than a few scenarios it did not equate to the overall goal for F3J or TD even. It just covered sky...but sank faster than my 4.0 - in those rounds we did not find lift...no one in the round did.

If they were all setup wrong then it's a strange situation... The Aspire is a great plane as well. I have never told anyone thinking of getting one anything different.


More to your other questions - Too lite ? You are asking me to answer a question which is attached to subjective conditions - how much wind ? how much span. Desired usage of the airframe? I am not considering that a 59 oz XII - Supra - Agida - (fill in the blank) is going to be used in strong winds even if ballasted because the starting weight of the airframe might make it less probable that if could even hold enough ballast for high winds. Low 60 oz planes start to become a bit if a specialty arrow in the quiver just like double carbon monsters.

-Subjective areas .. example - Handling, I might in my "noob" approach be able to accept a poorly handling a/c when you might toss the transmitter back and say "goodness man set this thing up". That's subjective....


Regardless of what constitutes good or bad handling - Handling in the LZ is a factor I would not take a reduction in performance if a plane was so lite that it was tossed around in the circle or LZ so much that it costs points then it might be too lite. So far, handling seems to be getting better not worse as the aircraft lose weight. Again manufacturers are I am sure much more intelligent than I in this regard.

The issues on "too lite vs just right" being thrown around in my opinion are more about application of the airframe. No one flies an 80 oz plane in early morning rounds and no one flies a 55 oz supra in 30 MPH winds.. ...unless everything else is broken!

Comparing a sub 60 oz plane in high wind to something at the "perfect" weight posted some time back at 2200 gr or 77 oz That is like asking a guy to Race a VW TDI against a Porche in a top speed race...not really fair nor is it fare to compare the two on economic fuel consumption. Each have their own niche.


Too heavy? fill in the blank with an applicable scenario but even just the experience of watching you, Daryl , Arend and other pilots has shown me that when the air is rising near and far they are not grabbing a 77 oz plane...they are choosing planes that weight less. Sometimes far less. Could they do it with a heavier plane - probably they are great pilots but they are grabbing a lite airframe most of the time unless the wind starts to howl. So stating that planes are "too lite" is "too general a statement.

By the way Larry It was sick watching your reflight round at the SWC you had found what you needed to save your round and then ...the unthinkable what happened?
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Old Apr 23, 2012, 12:30 PM
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I think it'd be interesting to ask the airfoil designer about the Reynolds number range he had in mind when he optimized the airfoil. That could shed some light on "how light is too light".
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Old Apr 23, 2012, 12:36 PM
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I'll give it a shot!

Every competitive F3J/TD plane out there has the ability to win rounds, that is until the Pilot screws it up. It has less to do with 4 oz heavier here or 6 oz lighter there or my span is bigger than your span and more to do with the decisions the pilot makes as soon as they pick up their plane. Every time I lose a round I ask myself what I should have done differently and not should I have flown a different plane?

David,

Looking forward to flying with you guys this weekend! Don't worry, I won't beat up on you with my Aspire. (Broken tail boom. I guess I cracked it at the TS last Oct and didn't even notice it) I will however try to out fly you with my Maxa 3.5 Hard Spread Tow, sub 65 oz, XII killer.

Jim
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Old Apr 23, 2012, 01:04 PM
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The reason why I said this topic is worn out was because we all have our own experiences and different ways of coping with the challenges of F3J. If we talk about our personal way of flying F3J... That cannot be very fruitful.

Ballasting is very subjective thing and pilots of talk about handling and stability etc, trying to put in words the experience of piloting the plane. However, it is very difficult to rationally explain why plane of certain (light) AUW is better than the other (heavy) plane.

Thinking rationally, ballast should improve handling, not make it worse. More weight translates to higher air speed, that translates to better control response. In a ballasted plane masses are also better centralized, inertia should be less of a problem. The only reason to for the experience of "light handls better" is that plane is flown grossly too slow.

Another rational yet not scientific approach to ballasting is to think about the airfoil. Using excess reflex or thermal camber (obviously) does not help the airfoil to work more efficiently. So if you need reflex very often to come back from downwind, you are propably flying your plane lighter than optimal. (Or if you can cope high winds with a light plane, you are not propably following the thermals long enough )

I have some opposite experiences. Sometimes I have also been caught with flying a too heavy plane, needing excell thermal camber for normal circling. That is (obviously again) not very efficient way of thermalling.


To make my point more clear, I use Pike Perfect (3.5 meter, I think?) polar from Samba. I am sure they do not mind that we borrow it



There are 3 polars calculated. The design weight of 2200g, and ballasted to 2800 and 3400g. Looking at the graphs I make three observations.

1) The 3400g plane has best max glide ratio by about 10% margin (compared to 2200g plane)
2) The difference of best glide speeds varies from 7m/s to 10m/s. The 3400g does not have much tolerance of flying too slow.
3) At typical F3J windy weather distance flights speeds (say 15m/s) the unballasted plane really suffers. Also the 3400g must fly faster than ideal air speed.

You could also read the graphs differently but to me the messege is obvious.
1) Our currently typical 2kg 3.7-3.8 meter F3J planes are really light. In typical distance flight they already suffer from being too light. (Fortunately we have the reflex...)
2) To freelychase the thermal in normal active weather it would be (performancewise) ideal to have the plane lightly balasted.
3) When it blows close to the 12m/s FAI limit (in altitude the wind is propably stronger) a heavily ballasted plane is almost allways a benefit. It just makes life more easy...

Talking of light planes, my 3.8 meter v-tail Xplorer is 1845g and spread tow Aspire is a tad over 1900g. Aspire seems to cope this light weight better, maybe thanks to its faster airfoil. For Aspire the new ST structure is a real improvment (although for some reason the little lighter disser Aspire seems to much more critical to fly)! Xplorer on the other hand lacks in L/d and handling unless I ballast it a little. With 200g ballast it grooves much better (like Aspire) through thermal turns and alsocomes better back home. I fly it empty only in calm conditions.

About Xplorer2? I hope the faster airfoil makes it more capable to make the best out of the light AUWs that are currently (structurally) possible. This is important because we (even me ) like to fly our planes lighter than what is theretically ideal. There are many practical considerations - light plane is propably more tolearnt to slight pilot mistakes, mostly flying too slow. Light plane is also more agile in landing circle and theretically it should do better in short lauches. Normally slightly lower min sink is not very important.

I really look forwad to get my hands on Xp2
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Old Apr 23, 2012, 01:12 PM
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Originally Posted by Francesco View Post
I think it'd be interesting to ask the airfoil designer about the Reynolds number range he had in mind when he optimized the airfoil. That could shed some light on "how light is too light".
To some extent we can cope with this phenomena by flying the lighter plane with less camber.

It is also interesting that my heavy double carbon Aspire seems to be quite happy with relatively larger camber settings (like 3mm in stead of 1,5-2mm). Its empty weight is 2400g and I fly it only in windy conditions when 3kg ballasted AUW is not uncommon (to my friends in US, that is well over 100oz).
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Old Apr 23, 2012, 01:23 PM
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There are of course limits to how heavy/ how light dependant on both aero and structural considerations. However once that range has been determined then there will be the subjective point soemwhere in between at which the pilot will be comfortable with the way his glider handles. It has been my experience that a glider that is on the light side for the conditions will require a greater effort or work load for the pilot. In other words I subscribe that a light glider can be flown closer to its potential by the more experienced pilot. Ballasting is something that the indivuidual pilot should play with in advance of actually having to compete in wind so he has some experience on which to base his descision. While speed to fly is more dependant for a positive outcome when wind flying, a little ballast can help get you through a stiff headwind, and help get you home for points. It is apparent to me that the builders can now build your glider at such a low weight that it will be truly usefull maybe 5% of the time. So it is more likely that you will be ballasting sooner than use to be the case. LJ
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Old Apr 23, 2012, 01:24 PM
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So , Tuomo, are you talking about the lighter plane's ability to cover ground against headwind?
In this case, the easiest thing to do is to copy what full-scale pilots do. Instead of looking at the CL/CD vs. airspeed graph, take the speed polar (Vsink vs. airspeed), and shift the origin to the right for headwind, and to the left for tailwind. The usual method of tracing the tangent line from the origin to the curve would give you the glide angle relative to the ground. This graphically explains the benefit of having a heavier wing loading, IF your goal is to cover enough ground to find lift or come back from far downwind.
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Old Apr 23, 2012, 02:24 PM
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I'll give it a shot!

Every competitive F3J/TD plane out there has the ability to win rounds, that is until the Pilot screws it up. It has less to do with 4 oz heavier here or 6 oz lighter there or my span is bigger than your span and more to do with the decisions the pilot makes as soon as they pick up their plane. Every time I lose a round I ask myself what I should have done differently and not should I have flown a different plane?

David,

Looking forward to flying with you guys this weekend! Don't worry, I won't beat up on you with my Aspire. (Broken tail boom. I guess I cracked it at the TS last Oct and didn't even notice it) I will however try to out fly you with my Maxa 3.5 Hard Spread Tow, sub 65 oz, XII killer.

Jim
Jim its always fun flying with you, against you an I agree its my thumbs that loses rounds not my plane. I look forward to getting my ass kicked.

Everyone will be flying a maxa this weekend lol ! Aredn has one Keith has one - you have one. I dont thihnk ill have my MKII in the air by the weekend as I expect them to be in transit to me and maybe if I am lucky land by friday...
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Old Apr 23, 2012, 02:32 PM
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... It is apparent to me that the builders can now build your glider at such a low weight that it will be truly useful maybe 5% of the time. So it is more likely that you will be ballasting sooner than use to be the case. LJ
Totally agree. And once you ballast up you are then facing more (at least fuse) damage on harder landings.

The best of both worlds--at least for my flying style/skills--may be to have two separate fuselages: a light no-ballast fuse for those "5%" light air rounds, and another stronger/heavier fuse that can take harder landings when ballasted up. Cheaper than 2 separate planes... Anyone tried this?

Chris B.
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Old Apr 23, 2012, 03:21 PM
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So , Tuomo, are you talking about the lighter plane's ability to cover ground against headwind?
In this case, the easiest thing to do is to copy what full-scale pilots do. Instead of looking at the CL/CD vs. airspeed graph, take the speed polar (Vsink vs. airspeed), and shift the origin to the right for headwind, and to the left for tailwind. The usual method of tracing the tangent line from the origin to the curve would give you the glide angle relative to the ground. This graphically explains the benefit of having a heavier wing loading, IF your goal is to cover enough ground to find lift or come back from far downwind.
My knowledge about full scale soaring is limited, but basically I think you hit the point I was trying to make. To simplify my thinking: in windy conditions going up is rarely the problem, getting back home is the tough part of the flight. So you better ballast (mostly) for the homebound stretch... (it is always a compromise). Please explain better Francesco, I am running out of words

With a too heavy plane you loose 30 seconds but with a too light plane you maybe land outside 75 meters and get zero points. Or get caught to that big sink, giving you 5 min flight. A too light plane for the conditions is a much bigger risk than a slightly too heavy plane.

Larry, I agree with you. Experience and knowing the plane are key factors. One should practice flying with different amounts of ballast. Air is never the same, the ideal ballast changes all the time. One can never practice too much - at least not with the long winters we have
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