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Old Jul 11, 2012, 03:03 AM
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ak79's Avatar
United States, CA, Torrance
Joined Apr 2006
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So if I understand right, the new model with ST fuse would need tail weight to CG properly with a Kevlar nose? Maybe the next step is to reduce the nose moment, and use Kevlar?
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Old Jul 11, 2012, 03:09 AM
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Tuomo's Avatar
Jyvaskyla, Finland
Joined Aug 2003
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Originally Posted by ak79 View Post
So if I understand right, the new model with ST fuse would need tail weight to CG properly with a Kevlar nose? Maybe the next step is to reduce the nose moment, and use Kevlar?
I very much prefer longer tail moment
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Old Jul 11, 2012, 03:47 AM
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Italy, Emilia-Romagna, San Lazzaro di Savena
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Originally Posted by Tuomo View Post
There are very few cases when a lighter plane is needed, and many more cases when flying a very light plane is a risk.
Lighter wing loadings need bigger tails for stability.. To my knowledge normal lamination fuselage cannot be ordered with this option.
Tuomo i agree with you!
Lighter planes need careful design of stabilizer and the planes go back really slow....no legs!
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Old Jul 11, 2012, 09:24 AM
F3B and F3K
RetoF3X's Avatar
United States, TX, Dallas
Joined Mar 2009
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Originally Posted by Tuomo View Post
I think if you go to any F3J contest (like Eurotour) and talk with pilots, you cannot find any hype on very light planes. Actually there is a strong consensus that normal spread tow 80 lamination is light enough. It weights at last 10% less than C68 from a few years back.
Apparently there is always a big hype about leightweight on rcgroups.

My experience (however in F3B and F3K) is that weight does not pull through linearly into sink rate.

In F3K we reached the point that some planes when made lighter don't really improve anymore in sink rate (empirically and in simulations). They simply start to fly too slow for the airfoil to work properly. They can have their moment when there is only a gopher-fart to thermal.

While I don't know where the crossover point is in F3J, the only advantages that I practically could envision for "superlights" are faster launch acceleration and better climb rate in marginal thermals.


Best,
Reto
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Old Jul 11, 2012, 10:07 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
857 Posts
Reto,

In general you are right, weight does not translate linearly into sink rate for big changes, say 2.2 kg and 1.6 kg.
However, for small enough increments, it's nearly linear. In the case I mentioned above the change is so small I believe it applies.

As for the eternal pursuit of a "lighter than air" model, I think it's overrated. I believe that a competitive flyer should ideally aim for four models to go to a large F3J competition, with only three models to sign in (only three era allowed in F3J) in accordance to the weather forecast prior to the start of the competition.
The ideal quiver in my mind is a super light model for the "gopher-fart" conditions, two "all weather" models capable of full tow in strong wind if needed and still light enough for weak conditions (probably around 1.9-2.1 kg empty depending on their design) and one stronger than average model for strong winds and “direct tow conditions” when you'll need large amounts of ballast anyways.

BTW, I don't believe the "my model is strong enough and penetrates well enough" remark. If the wind is strong enough and direct tow is called for, there are very few models which are truly strong enough on the line and the flex cost you altitude. Furthermore, there are very few models which can penetrate well enough without large amounts of ballast or a large lose in altitude.
Now, I've flown in winds where a 2.8 kg model in speed mode was getting pushed back and the only way to make your time was to reach wave lift or slope lift way up wind, meaning you need a heavy slippery model or you’re in real trouble. I've had it in at least three international competitions I've competed in.
A super light Xplorer is very nice to have but I wouldn’t give up practicality for 1% in overall weight unless I considered the model to be a specialty model ("gopher-fart" model).
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Old Jul 11, 2012, 10:39 AM
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Reto,
I totally agree the mania for light planes has me confused. There are no podium finishes for having the lightest Toy. On our team, Philip has managed Prestiges with ridiculous weights. These models are really best suited for dawn or night flight but if handled well offer some advantages in dead conditions. Each of the guys have one. Light weight models take more pilot input to be flown well. A super light and an untrained pilot are a bad combination. It becomes a real liability when the air starts cycling and the pilot is unaware of speed to fly.That being said the Prestiges and Perfections have Spread tow fuselages with Kevlar noses. The new Xplorers are nice models, I just disagree with a full carbon nose, when I have seen the other options work well.
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Old Jul 11, 2012, 02:56 PM
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webbsolution's Avatar
Joined Jul 2007
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[QUOTE=Tuomo;22131556]I think if you go to any F3J contest (like Eurotour) and talk with pilots, you cannot find any hype on very light planes. Actually there is a strong consensus that normal spread tow 80 lamination is light enough. It weights at last 10% less than C68 from a few years back.

There are very few cases when a lighter plane is needed, and many more cases when flying a very light plane is a risk. Flying a plane - any plane - very very light hurts L/D (the more the faster you want to go). I also think very light planes are often critical to handle. Very little momentum and narrow speed range. This is the reason why I fly my 1.8kg Xp1 normally with 200g ballast. This weight takes it to the C68 "design weight".


I have one Xp2 3.8m on order. I agree the problem with with 2.4 Ghz antennas, but I made my choise because carbon fuselage can have the larger rudder. Lighter wing loadings need bigger tails for stability.. To my knowledge normal lamination fuselage cannot be ordered with this option.[/QUOT

Let me get this straight...lite planes are bad...and they need to be ballasted in order to have the best ld and handling....ok...

you ordered an X2 because it has a big fin...and a big fin is a requirement at such low wing loading but you will be flying with 300gr of ballast so you dont need the big fin because you will bring you wing loading up with lead...as you aptly stated these plan are too lite....pft you contradict yourself. If you drank your own coolaid then you shoukd have ordered a double carbon x2/with the standard fuse.
Tuomo, its time to come out of the closet i think you just crossed over to the other side...you ordered a x2 lite because you wanted to win....
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Old Jul 11, 2012, 05:03 PM
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Jyvaskyla, Finland
Joined Aug 2003
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Originally Posted by webbsolution View Post
Let me get this straight...lite planes are bad...and they need to be ballasted in order to have the best ld and handling....ok...

you ordered an X2 because it has a big fin...and a big fin is a requirement at such low wing loading but you will be flying with 300gr of ballast so you dont need the big fin because you will bring you wing loading up with lead...as you aptly stated these plan are too lite....pft you contradict yourself. If you drank your own coolaid then you shoukd have ordered a double carbon x2/with the standard fuse.
Tuomo, its time to come out of the closet i think you just crossed over to the other side...you ordered a x2 lite because you wanted to win....
The new Xp2 3.8m I got is not lighter than my 3.8m Xp1 But Xp2 wing profile is (I hope) more optimized for light loadings and large x-tail rudder gives better stability in low air speed, hence improving efficiency and handling in floating speeds. It will fly better... This is what I call progress - getting all the pieces together so that they work together. Maybe also get a similar fuse for my old Xp1?

And now I will tell you secret about winning...Who knows, maybe worth also in SA? The floating is tough - you fight for 10 minutes and win the opponent by 3 points. On the next flight you land 97 points and the marginal is gone. The most easy points one can collect in F3J are available in the strong wind groups. I mean those groups when 50% of pilots have too fragile plane, have not ballasted enough, do not dare to make direct tow, or just are have never practiced in higher than 8m/s wind. Then you can easily win a group by 300 points margin. It is worth going for it...!! This is why I like to have have a heavy lamination F3J ship in my hangar, and never leave to competition with a plane that can take hard direct tow efficiently and without flexing too much.


BTW Regarding to Larry's post about Light Prestiges. In June Phillip gave a me a short 4 min lecture about "aeromerchanical stability". In plain english (if I understood him right) he meant that tail feathers must be large enough and fuse long enough so that plane does not wobble even when manourverd at min air speeds. This is the practical F3J approach: do not look at highest theoretical efficiency, look at how efficiently plane can be flown in practical contest environment. (By an average pilot, I would like to add )

Looking at new F3J planes since Prestige, it is easy to see that this is the winning trend in F3J. The best example of the success of this approach is new x-tail Stork. Well not totally new, since the wing is old... But compared to the old v-tail, the new long x-tail fuse obviously makes Stork wing work radically more efficiently at low air speeds. I am sure anyone who saw Juraj Adamek fly his Stork in the 2nd flight of the very difficult fly off in Hungary will agree with me.
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Old Jul 11, 2012, 10:17 PM
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J. Wydronek's Avatar
United States, AZ, Buckeye
Joined Mar 2010
649 Posts
Webb

Great looking plane. Guess its a good thing you dont fly spektrum it would look like a porcupine with all the wiskers sticking out. And if the x2 is such a huge jump from the standard x i am going to have to get on. My d box flies great already kinda excited. Bob what a great product.

Joe
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Old Jul 11, 2012, 11:29 PM
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Joined Jul 2007
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Joe,

yea i cant imagine the royal pain in the ass having a second rx would be...I have been really fortunate that all my full carbon birds with wiskered fhss 3 installs encounteted zero lockouts. may it continue. i think i flew wiskers on 5 or 6 models prior...i basically ranged checked it and gave a bunch of tosses.

i havw another to complete and a sl 4.0 fuse
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Old Jul 12, 2012, 03:52 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
857 Posts
Quote:
Originally Posted by Tuomo View Post
And now I will tell you secret about winning...Who knows, maybe worth also in SA? The floating is tough - you fight for 10 minutes and win the opponent by 3 points. On the next flight you land 97 points and the marginal is gone. The most easy points one can collect in F3J are available in the strong wind groups. I mean those groups when 50% of pilots have too fragile plane, have not ballasted enough, do not dare to make direct tow, or just are have never practiced in higher than 8m/s wind. Then you can easily win a group by 300 points margin. It is worth going for it...!! This is why I like to have have a heavy lamination F3J ship in my hangar, and never leave to competition with a plane that can take hard direct tow efficiently and without flexing too much.
I totally agree, even though I don't enjoy flying in nasty weather, the discriminating factor for me in all the F3J competitions I placed well in was surviving the nasty weather just a little bit better than most. At times it's even worth flying conservative during this type of weather to reduce the point loss enough in order to better your placing. I remember many rounds in WCís and ECís Iíve participated in where rounds were won with 7 and 8 min.
Taking big risks in nasty weather can reward greatly or can bury you. Team work is also very important in such weather as changing tactics and switching to different air quickly when yours is spent is detrimental to achieving a long flight. In a WC you can have both a helper and the team manager at your side, use them both to search for alternatives and donít have them get too focused on your model.
A suitable model for such weather is usually a heavy one with lots of inertia in the wing so it doesnít get thrown around the sky like a rag doll (heavy carbon wing does the trick).
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Old Jul 12, 2012, 08:38 AM
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Australia, WA, Perth
Joined Oct 2003
902 Posts
Agree with you there Tuomo, thats why I took 2x Supra and my third model was a full carbon80 Aspire with a dry weight of 2.4kg. Strong and stiff, was used to great effect in a round in France WC when conditions were bad, many pilots picked up their throw out in that round.
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Old Jul 12, 2012, 09:27 AM
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Italy, Emilia-Romagna, San Lazzaro di Savena
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Originally Posted by lesterpk View Post
Agree with you there Tuomo, thats why I took 2x Supra and my third model was a full carbon80 Aspire with a dry weight of 2.4kg. Strong and stiff, was used to great effect in a round in France WC when conditions were bad, many pilots picked up their throw out in that round.
Why not a f3b plane for windy weather?
Launch high and lot of speed for coming back..Fosa Lift?
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Old Jul 12, 2012, 09:28 AM
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Originally Posted by SoaringDude View Post
Teflon battery bearings? The launches on those things are awesome.
Im hoping the effect is better than any sum of parts i could combine.
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Old Jul 12, 2012, 10:25 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
857 Posts
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Originally Posted by mverardi View Post
Why not a f3b plane for windy weather?
Launch high and lot of speed for coming back..Fosa Lift?
An F3B could work well and a Fosa may do an excellent job in capable hands, but there are two draw backs, one has to do with size and the other with stability:
1. An F3J model is larger (3.5+ meter) so it's easier to see and therefore possible to fly longer in a thermal before the distance is too great from a visibility point of view. Longer time in a thermal is sometimes the difference between full times and only partial times. An Aspire at 3.7 meters could fly almost 15% further Then a 3.2 meter Fosa. In 2000 WC I had an F3B eagle with me as my windy model but the smaller wing span 2.9m was limiting at times.
2. An F3J model is designed with greater stability in mind, larger tail and dihedral angle so is easier to fly and thermal at near stall speeds.
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