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Old Aug 16, 2013, 10:44 AM
F3B
satinet's Avatar
Warwickshire, England
Joined Sep 2006
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F3b - how heavy?

Hi

Just wondering what people think is acceptable normal weight for an empty F3b model particularly to do with weights for duration. The radical jazz specs got me thinking.

I have been offered an fs4 double carbon. I want an fs4 but it is 2300g. Do you think that is getting a bit heavy for duration?

My old double carbon fs3 rds was 2150g. Where does extra 150g come from in 19cm more of wing span?! My mate's single carbon fs4 is 2190g. My current fs3 single carbon is 2020g. Has TUD changed something?

Clearly the fosa and fosa lift have quite a high wing loading because of the aspect ratio. But then the aspect ratio is an advantage.

Here is a table from a japanese site comparing loadings:
http://blogs.yahoo.co.jp/f3b_info/10832043.html
not hard to understand if you google translate it.

My current model is a stinger that weighs 2040g, which I consider pretty normal nowadays (?). The wing area is very similar to the fs4 - i would notice flying with 260g of ballast in i think.

I am being too fussy?

Cheers
Tom
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Last edited by satinet; Aug 16, 2013 at 10:52 AM.
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Old Aug 16, 2013, 11:12 AM
Thermal Wrangler
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Launceston Tasmania
Joined Mar 2004
2,098 Posts
Your table is ready

Here's that table (again) with translated row headings.

I took a guess at some of the units.

Chris.
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Old Aug 16, 2013, 12:17 PM
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Joined Apr 2012
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my $.02 opinion is learn to fly with it as is... 2300.. sure its a bit heavier but its also a bigger airplane. we all want a lighter plane but we also put these things though hell on launching. Aspect ratio will help in efficiency but it is the area dm2 of the wing that will give you your wing loading. I too make molded f3b f3f wings and i can tell you it is not easy keeping the strength up where its needed and keeping the weight down.. I would not put too much disappointment in TUD. they are building planes for the masses and doing a great gob at it.
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Old Aug 16, 2013, 03:12 PM
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If you often fly in wind, then you want the stiffer model for speed and distance. Ballast can't make a model less flexible.
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Old Aug 16, 2013, 10:00 PM
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Australia, WA, Perth
Joined Oct 2003
881 Posts
Both my Shooter and Fosa Lift weigh within a few grams of 2kg. One of the better thermalling F3B models I've had before these weighed 2350, it was a double carbon layup and extremely stiff VV Viking.
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Old Aug 16, 2013, 11:12 PM
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Joined Oct 2006
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Fs4

I think you will find the extra weight in the 2300gm FS4 is in a stronger boom ( F3F) and more nose weight.

The competition light F3B fuse can be ready to fly at around 2150gm depending on your preferred CG. The trade off is a boom that will break quite easily ( on landing only)

I have not flown the 2300gm FS4 but know people who do and they do not seem to have any issue with it.
Yet to be tested in really weak early morning stuff though.
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Old Aug 17, 2013, 01:29 AM
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United States, CA, San Luis Obispo
Joined Aug 2006
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Lighter is certainly better for duration. But not at the expense of a flexible airframe. It wasn't very long ago that an 80-100oz airframe was normal. Think V-ultra, T-warp and Cobra. Even the Estrella was pretty darned heavy, 80-90 ounces. The current generation of models with very thin airfoils have become especially sensitive to empty weight while thermalling, but luckily empty weights have also gotten lower.

I don't think anyone can tell you whether or not to buy that particular model. But you can bet that there is probably a long line of people that wouldn't kick an FS4 out of bed at 2300g.
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Old Aug 17, 2013, 03:03 AM
I do this for fun!
Sunshine Coast, Australia
Joined Sep 2004
1,197 Posts
Hi Tom,

Fly in lift and you'll never notice the difference!

Launch high and you'll never notice the difference!

In fact, the only time you will notice the difference is if there is no lift at all for the whole flight and you are flying against very very good pilots with lighter planes.

Other than that, see my first and second offerings

Ken ( who flies a 2.6 Kg Caracho 3.1 in thermal comps and is looking forward to trying his Stinger out at 2.2kg)
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Old Aug 17, 2013, 12:39 PM
Challenge is rewarding
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San Diego, CA
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For reference, all of my double carbon FS4s weight between 2.18 and 2.22 Kg
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Old Aug 17, 2013, 12:41 PM
F3B
satinet's Avatar
Warwickshire, England
Joined Sep 2006
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hmm this one seems a bit heavy
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Old Aug 17, 2013, 12:45 PM
Detail Freak
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Harbor City, CA
Joined Oct 2003
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Isn't it true that a lighter model being the same design launches higher in the same conditions? Or at least, CAN be launched higher?
Obviously, in that statement stiffness isn't taken into account.

R,
Target
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Old Aug 17, 2013, 12:49 PM
Challenge is rewarding
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San Diego, CA
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Also, I build light. Life batteries, cast lead nose weights, custome wiring harnesses....light servos....
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Old Aug 17, 2013, 12:51 PM
Detail Freak
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Harbor City, CA
Joined Oct 2003
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Tom-

Are you having trouble with duration on either model??
I think that setup has quite a bit to do with how a model flies for thermalling.
As Ken stated, they all seem to do well when flown in lift, regardless of 100g either way.

I even think some of it may be mental; thinking your plane is "too heavy" wont help you make your time, but that is just a theory I have (and may also suffer from).

R,
Target
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Old Aug 17, 2013, 12:51 PM
F3B
satinet's Avatar
Warwickshire, England
Joined Sep 2006
5,510 Posts
Quote:
Originally Posted by target View Post
Isn't it true that a lighter model being the same design launches higher in the same conditions? Or at least, CAN be launched higher?
Obviously, in that statement stiffness isn't taken into account.

R,
Target
yes Mate, but don't forget that you only fly with no ballast 1/3rd of the time in f3b. Getting good launches with no ballast is a lot easier than getting a good launch with lots of ballast.

In distance and speed you fly with ballast.
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Old Aug 17, 2013, 12:56 PM
Detail Freak
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Harbor City, CA
Joined Oct 2003
21,618 Posts
Thats my point; its on your side of the question for duration.
Higher launch= possibly easier time making 10:00....
So long as you can get the weight you want with full ballast, its better to have a lighter plane for Duration, if duration is a problem. Right?

R,
Target
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