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Old Mar 18, 2012, 06:17 PM
PaulG
Newcastle, NSW Australia
Joined Dec 2004
321 Posts
Discussion
Comparison of current crop of F3J/TD Planes

I was looking for a way to compare my Egida with the current crop of planes in some fairly simple way. I came across the concept of cubic loading, which is supposed to take into consideration the volume of the wing by dividing the weight by the wing area raised to the power of 1.5. I guess this is a fudge factor but is supposed to have some validity if the same wing profile is used. I know that the wing profiles are different but not that different, so I made the table. I then arranged the various planes in order of their cubic loading at various weights. I took weights of planes I have or had and published data of information from friends. What is apparent is the similarity between a lot of the planes that seem,at first, to be different
It is very obvious that the two Jaro Muller planes use a different philosophy to the others, veering towards the F3B end of the spectrum with regards to wing loading and cubic loading but retaining the low weight of the most modern planes (and thus good launch potential). The average chord of the Espada and Egida are also the smallest, which will affect the Reynolds numbers and, as I have found, mean that the Egida has to be flown faster than the other planes to work at similar Reynolds numbers. It also explains why if you dawdle through sink, the Egida comes down fairly smartly, whereas at higher speeds it does not seem to loose much height at all. I am in no way anything of an aerodynamicist, can hardly spell it, and know that there are other factors involved in how a plane flies but it may be of interest to you. I have added the Crossfire 2 as a F3b comparison, although the profiles used on F3B planes are probably fairly different to those used in F3J planes
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Old Mar 19, 2012, 02:25 AM
Thermal Wrangler
DrFragnasty's Avatar
Launceston Tasmania
Joined Mar 2004
2,145 Posts
Number Crunching

Verrrrry interesting Paul. Thanks for crunching the numbers. I've never seen this characteristic before (cubic loading).

Here's the data as a jpg (hope you don't mind the format change) to make it more accessible (see below):
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Old Mar 19, 2012, 02:40 AM
PaulG
Newcastle, NSW Australia
Joined Dec 2004
321 Posts
Thanks,

No Chris, I don't mind at all, took me all my time to change it from a .docx extension to a .doc extension
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Old Mar 19, 2012, 11:38 AM
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NorCal
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How can we do a comparison of top F3J planes without including the current World Champion Icon 2?
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Old Mar 19, 2012, 04:10 PM
PaulG
Newcastle, NSW Australia
Joined Dec 2004
321 Posts
Your right

The Icon 2 seems to be a North America only plane, I think due to the transport problems of the long centre section but I'll add it.
Cheers,
Paul
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Old Mar 19, 2012, 04:43 PM
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Joined Mar 2004
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By using the 1.5 fudge factor you are simply ranking planes by wing loading. It would be much more interesting if you actually calculated the wing volume but that would be nearly impossible as it requires a decent CAD model of every plane.
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Old Mar 19, 2012, 05:06 PM
VHO
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Armidale NSW Australia
Joined Feb 2007
568 Posts
Interesting, but...

Hi Paul,

Weather must have been not so good down your way lately

Thanks for the calculations. My take is that the data presented that way demonstrate that models can get to similar performance by many routes. I do like how your Egida can high (well low really) tail it out of sink faster than most, as for the data, I agree the ranking is on wing loading. You don't fancy putting each model into XFLR-5 and cycling them through a series of what ifs do you? Maybe a job for a longer bout of south easterlies

Hutton
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Old Mar 19, 2012, 05:35 PM
PaulG
Newcastle, NSW Australia
Joined Dec 2004
321 Posts
Yes, But

The weather has been bad but its the Heathcote Cup this weekend, then the Millenium Cup round at Queanbeyan and then I'm off o/s for a month. Plus, the next Egida comes this week, Plus I've got a copy of the program but don't know how to use it!
I've added the Icon2 see how similar it looks to my Xplorer 3.8 cross tail at its heavier weight. I am sure they fly differently but probably not in the sink rates and L/D.
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Old Mar 20, 2012, 01:13 AM
Bro
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Southern California
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Xplorer II

Howdy,
How about the 3.8 Xplorer II @ 1745gm? And full strength.
We will not even talk about the 1500gm "lite"...
Same size wing a original X 3.8.
Flying in Europe for a year, and now USA as well!

Best,
Bob
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Old Mar 20, 2012, 04:26 AM
PaulG
Newcastle, NSW Australia
Joined Dec 2004
321 Posts
Yes, All good

Getting the weight down whilst retaining enough strength to take a launch in light winds must be good for dead air times as the wing loading has a direct effect on the sink rate. Once it gets even a bit thermic, that all goes out the window but with the known good handling of the Xplorer range it looks a good bet. However, pilots win competitions not planes. I started this just to see how my Egida sits in the ranks and it is a bit further out on a limb than the others. I have had several Xplorers and retain my 4m ST bought from your good self because it is certainly great in the light conditions. I think that if you can get the weight down whilst retaining full strength, your launches are going to be better. I know that the Egida launches better than anything else I have and is strong enough not to show much bend in the wings and that is with a D box construction! Of course, again, we saw from the last WC that the best pilots can get away from the most ridiculously low launches but, as most of them practice of a short bungy or hand throws, it is not surprising.
Cheers,
Paul
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Old Mar 20, 2012, 02:24 PM
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Jyvaskyla, Finland
Joined Aug 2003
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Nice comparison pigly. I also fully agree with your previous post. To me Orca v-tail was the slippery plane that launched well. Orca had very good performance in almost any weather, but was little tricky to fly. I think is the reason why Orca has almost disappeared from competition circles.

The nice thing with F3J is that the plane is not critical. Current mainstream planes can be built at 2kg with quite strong ST structure. This not too expensive and weight and stiffness are just the right for an allrounder. When Perfect / Aspire / Xplorer came out the std lay-up was C68, giving about 2.2 flying weight, which was ok for most conditions, but in very light weather the planes felt little heavy.
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Old Mar 20, 2012, 05:33 PM
Ricky Windsock
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USA, FL, Sanford
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The standard 3.5M Xplorer ST crosstail flown all over comes out at about 1900grams flying weight. It seems that the 3.5 Xplorer in your comparison must be an old Carbon D Box from 2 or 3 years ago.
Do you think you could add the current 3.5ST?
Thanks
Gordon
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Old Mar 20, 2012, 06:56 PM
PaulG
Newcastle, NSW Australia
Joined Dec 2004
321 Posts
yes

I'll do that and the Orca and the light Xplorer when I have a sec, probably today
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Old Mar 20, 2012, 09:35 PM
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Comparing wingloading is an impractical means of comparing the current group of F3J models. This method is lacking enough information to truly evaluate a design and certainly not enough to compare apples and oranges. Just got back from The North Cyprus contest where I flew all day Saturday at 2.6 Kilos with a 3.67 meter wingspan model. There simply is just more to it than squares and weight. LJ
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Old Mar 21, 2012, 12:48 AM
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United States, CA, Midway City
Joined Dec 2003
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How can I resist posting in this thread. I've done this for every model out there too, but my formula is a bit different. I use the wing loading in oz/sq. ft and divide that by the sq root of that wing area (in sq ft.) I get the same numbers as pigly, except for the Supra which I have at 67.9 sq dm and not 69.4 .

Anyway,
Quote:
Originally Posted by Bob McGowan View Post
How can we do a comparison of top F3J planes without including the current World Champion Icon 2?
70 oz icon = 2.71


Quote:
Originally Posted by Bro View Post
Howdy,
How about the 3.8 Xplorer II @ 1745gm? And full strength.
We will not even talk about the 1500gm "lite"...
Same size wing a original X 3.8.
Flying in Europe for a year, and now USA as well!

Best,
Bob
1745g 3.8 XII = 2.37

Quote:
Originally Posted by aussief3b View Post
The standard 3.5M Xplorer ST crosstail flown all over comes out at about 1900grams flying weight. It seems that the 3.5 Xplorer in your comparison must be an old Carbon D Box from 2 or 3 years ago.
Do you think you could add the current 3.5ST?
Thanks
Gordon
1900g X = 2.87

One big thing about the planes getting lighter and the span gettng bigger. The plane can thermal too slowly for its bank angle making the speed differential between inside panel and outside panel too great.

Also regarding comment of Egida outlaunching Xporers, I would find that at odds with all my data. Egida and 3.5X would be about the same weight. The X would have much more wing area to generate higher tension. That higher tension would accelerate the same mass 3.5X more.
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