I want to build new wing on my F3A and I don´t know which airfoil use to precision aerobatics and good spin-rolls. And can you recommend me root and tip dimensions? I plan Wing Span 1980mm.

Pls, sorry my English. I´m from Czech Republic.

Hi MadBox,

There been some interest on airfoils recently, I cannot find proper thread just now.

Try this search [link=http://www.rcuniverse.com/forum/searchpro.asp?phrase=airfoil&fuzzyMatch=on&author= &forumid=101&topicreply=combined&message=both&time frame=%3E&timefilter=0&language=single&top=500&cri teria=AND&minRank=0&sortMethod=d&submitbutton=+OK+]link[/link]

Thanks, I had NACA 63A012, it was great airfoil, but with this airfoil I cannot do good spin roll. Somebody told me that with this airfoil it is hard to do spin roll. So I am looking for soma another airfoil. Do you think that NACA0012 will be better?

Yes. The high point should be moved to about 33-35% though.

-Mike

Thank you mike. And what about tip airfoil, Will you use the same airfoil or the airfoil with less thickness?

The tip and taper is where you get to play

Some people like a really thick tip, some like a really thin tip. Both have different characteristics; the best I can say is try one and go fly it, see how you like it. if it's not what you want, change it. You can spend a lifetime playing with airfoils. And still find yourself drawing the same conclusion: it doesn't matter all that much.

-Mike

Do you mean snap roll when you say spin roll? (or another way is to call it a flick roll---same thing as a snap roll)
If you do, then plan form and wing loading are more important than the section, but, for what it's worth 64012 at the root and down to 64009 at the tip works well in my hands at least.

Thank you for everything.
I want to bulid new wing on my F3A Atlantis, because old wing are so heavy and it is hard to make nice snap roll with them.



This is my model.

I´m sorry but I don´t understand few words, because my english isn´t good enough: plan form , section Can somebody explain me these words?

"planform" is normally the outline of the plane if viewed from above-----as most aircraft plans are presented this way it becomes the "planform" view.

"Section" is another way of referring to the airfoil chosen. If you took a completed wing and cut vertically through it and then viewed the cut from its side you have a "section". It means the same as the airfoil outline.

Hope this helps.

Last year here, had been informed to use a NACA 65A018 at the root tapering to a 65A012 at tip. This is a quite pointy airfoil, and has been used for decades.

Wm.

Thank you,really it helps. Now I'm more clever.

Looking at your nice pictures of your Atlantis, and reading that your present wings are heavy, I would guess that the weight of the wing is the problem.
Is the problem that it is difficult to make the snap stop at the right place?
If so, a wing panel that is lighter, especially out towards the tip, will make the snap roll much easier to start and stop, and is more important than the airfoil used.

When I´m trying to make two snap rolls then 1st roll is slow and the 2nd if much more faster and better than 1st.

Right wing: 550 grams
Left wing : 545 grams

So I think that it is too much and I would to have 350-400 grams. So I will try to make a smaller wing.
Can you recommend me wing loadnig ? I'm not sure how big should be the wings.

The current generation of "2 metre" f3a models snap better than earlier ones, and they have smaller wings
than your Atlantis.
Have a look at the designs for Oxalys, Beryl, Integral(New Stephane Carrier model @ Zn Line), Genesis---They'll all have wing spans near 74 inches (1.88 metres) and wing area about 950 square inches(sorry, don't know metric for that!)

But---have you tried different control settings just for snaps? My Abbra (Made in the Czech Republic!) is OK for single snaps on my normal flight settings, but needs much more aileron. a little more elevator, and less rudder for anything more than one.

My wing area is 1003 square inches. I think that it is so much.
But I have used OS160FX and the weight of my model is 4900grams (172.8 ounces) and I´m afraid of wing loading, because a lot of models(oxalys, Beryl,...) are more lighter (4300grams=151.6 ounces) What do you think, should i do quite larger wings?

I have tried everything and finally I must have a lot of ailerons and rudder and i little of elevator, but it still isn't right. My friend have Rhapsody(too from JM composite) and it do snap rolls much better than my Atlantis.


I know Abbra very well. And the models from JM Composite are the most used in czech pattern flying.

Hello Madbox
Weight of each wing of my Partner (balsa foam with Oracover ) is 460 g totaly équiped. Carbon tube is 50 g.
I also had a Cocaine and Rhapsody (JM composite/ Modelltechnik-lorenz). Weight of each wing painted in mold) is about 450 g totaly equiped and carbon tube is 70 g.
Now wingspan is about 1,85m. End of wing is smaller than before about 200 to 210 mm.
A good airfoil is Eppler 168
http://epervier.sudluberon.free.fr/spp/21profil.htm
regards

Thank you. It looks like great page, but I can't speak French. Know anybody similar page in English?

Hello
I think you'll have no problem with weight about 5000 g and new small wings.
Now same pattern like Oxalys are set up with "electric motor and batteries " as they are set up with Yamada about 4600 g. They are near 4900 / 5000 g with same wings about 63 dm2 and there are no problem with wing load.
Claude

Thanks everybody.

I will make smaller wings. And after I fly with them, I will tell you how it fly.

http://zzmanu.club.fr/spp/spp.html

Manu

Is that a wing tube used on your Atlantis? Maybe you can shorten the current wings to experiment.

Yes there is a wing tube an my Atlantis. But I made new much smaller and lighter wings already. Now my Atlantis flies great.

Don't worry too much about the airfoil. I got an NACA0016 to snap well once I tapered down 50%. If it isn't crisp enough try reducing the leading edge radius at the tips.

airfoils -a waste of time
make it as thin as you can and as light as you can and use at least a 2-1 taper ratio
The shape will be dictated by thickness and high point needed to prevent twist and flex.
The strongest lightest one you can get will be 1 lb foam with 1/16" thick 6 lb balsa welded on with a press to get an absolute 100% bond . epoxy OR ProBond either one done right works.
a cf wing tube and sleeve with top n bottom spars connecting top to tube to bottom - then extended out a few inches completes th job -do not stop th e tube and spar at same spot.
The completed covered assembled 1200sq in assy inc servos is under two lbs.
dun it over n over
snaps are a product of the model setup - you can snap a 20% airfoil if you setup for a quick pitch.