Wing construction - RC Groups
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Sep 08, 2017, 10:29 AM
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Discussion

Wing construction


Hi everyone
Previously i was folding 6mm depron wings and it all was fine...
Recently i ordered bunch of 3mm depron.
I made 1000mm wingspan eindekker around 600 gramm.
Wing snapped on the maiden flight..... i made another one with ribs.

The construction was a simple fold design with double vertical spar near cg spot.
Is this normal ? what are you people using for a fast wing build.
Also whats the easiest way of making symmetrical tapered wings for 3d planes like extras edges and sukois?

Im planning on making a 3d plane around 900gramms... wings should be pretty strong, should i just order 6mm depron ?
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Sep 08, 2017, 11:29 AM
Registered User
Fold the 3mm foam around a full wingspan length carbon tube spar.
Sep 08, 2017, 11:52 AM
Registered User
Quote:
Originally Posted by tolyaba
Hi everyone
Previously i was folding 6mm depron wings and it all was fine...
Recently i ordered bunch of 3mm depron.
I made 1000mm wingspan eindekker around 600 gramm.
Wing snapped on the maiden flight..... i made another one with ribs.

The construction was a simple fold design with double vertical spar near cg spot.
Is this normal ? what are you people using for a fast wing build.
Also whats the easiest way of making symmetrical tapered wings for 3d planes like extras edges and sukois?

Im planning on making a 3d plane around 900gramms... wings should be pretty strong, should i just order 6mm depron ?
Where did it break? At the center or farther out?
Sep 08, 2017, 12:46 PM
Registered User
near the fuse
Sep 08, 2017, 01:43 PM
An itch?. Scratch build.
eflightray's Avatar
Build a conventional type wing, just make sure you understand about spar design and strength.

These are 6mm ribs, 3mm sheeting top and bottom, (all Depron), and balsa spars and leading edge.


Ray.
Sep 08, 2017, 03:00 PM
Registered User
Quote:
Originally Posted by tolyaba
near the fuse
In that case, a ply or carbon dihedral brace out to about 1/4 span might be enough. (Note in eflightray's photos above how the wing joiner tubes function to strengthen the center.) The bending force falls off exponentially from the root to tip. So a full span carbon tube strong enough to handle root forces isn't needed at the tips.

Full depth depron spars, root to tip do a good job of keeping the skins apart but aren't usually enough at the root where forces are the highest.
Sep 08, 2017, 03:25 PM
Retired CAD guy
birdofplay's Avatar
Fishing poles are Tapered and wrapped not Pultruded.
Some Kite shops and supply houses have tapered CF as well. Goodwinds , KBI et al
Wrapped CF is going to be more expensive
But ,if you want the highest Strength to weight ratio you have to get the wrapped stuff.
Sep 09, 2017, 09:27 AM
Registered User
psychedvike's Avatar
You could consider a hot wire cut wing core. This method seams to be less popular these days but it is still my favorite method of wing construction. Here's a link to a video on how I cut them.
Hot wire wing core cutter. (13 min 27 sec)
Sep 09, 2017, 02:35 PM
Registered User
Yes wanted to try that a very loooooooooooooong ago but not sure on the foam names in europe.
Is EPS good ?
Sep 09, 2017, 04:15 PM
Registered User
There is a way to be fairly sure just how strong your spar is without risking a full crash.
Put a chair under each wing (about 2/3 away from the root of each wing). Now stack weight on the fuselage (books will do) such that the weight of the books is four times the weight of the plane. If the wing doesn't fold, you're in good shape. Yes, you WILL pull 5 g (or more) maneuvers, if only unintentionally, at times.
You can, of course, test to even larger G's by simply stacking more books.
Personally, I'd rather test the spar strength on the ground rather than the air , just like they do with full scale planes.
Sep 09, 2017, 04:58 PM
Registered User
TigerOC's Avatar
I drew up plans for a 31" Stik for club pylon racing 2 years ago. The wing is an Armin type. The sheet is 3mm and has a 6mm square pine spar sandwiched between 2 strips of 6mm depron and covered with another strip of 6mm depron. The 3mm depron is pre-taped with packing tape before bending. There are 12 flying in the club and I have never seen a wing break. They certainly show signs of bend stress in the centre. I have 3 of these myself and still use the original wing built 2 years ago. Been through some 4 fuselages in that time.
The model uses a Hextronic 24g 1300 kV motor and is capable of speeds over 50mph.
Sep 09, 2017, 05:53 PM
Registered User
how much G do you pull on the blenders and poptops ?
Sep 10, 2017, 02:23 PM
Registered User
Quote:
Yes wanted to try that a very loooooooooooooong ago but not sure on the foam names in europe.
Is EPS good ?
Better choice is XPS (extruded polystyrene).
In my country (Serbia), most popular are BASF or AUSTROTHERM XPS foams, better known as "STYRODUR".
Density is near 30g/dm3.
Cutting goes very well with Kanthal wire.
I'm using 0.3mm kanthal heated with 1.4A current.
Sep 11, 2017, 02:34 AM
Registered User
wow XPS is pretty pricy 8 euro for 1m
Sep 11, 2017, 12:17 PM
Registered User
Read somewhere that 3d planes pull up to 10 g is this correct?


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