Wing construction - Page 2 - RC Groups
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Sep 11, 2017, 03:28 PM
Registered User
Quote:
Originally Posted by tolyaba
Read somewhere that 3d planes pull up to 10 g is this correct?
All depends on how you fly.
You might pull even more if you try to.
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Sep 12, 2017, 03:03 PM
Registered User
so if a plane weights 1000 gramms wings should be able to carry 10 000 gramms of weight....
sounds crazy that foam able to do that ;D
Sep 12, 2017, 06:32 PM
Registered User
Quote:
Originally Posted by tolyaba
so if a plane weights 1000 gramms wings should be able to carry 10 000 gramms of weight....
sounds crazy that foam able to do that ;D
Exactly.
Which is exactly why several have suggested that foam alone will not enable the plane to play in the major league aerobatics arena without a strong spar (like carbon fiber tube or the like).
There's no getting around this...
Sep 15, 2017, 05:36 AM
Registered User
Im done guys... i followed spitfire build from FT... reinforced the wing spars with 4 mm carbon rods guess what just snapped it on the maiden.. ok i pulled max on elevator when i lost orientation while trimming the plane was upside down resulting in a very sharp loop then aftet the loop the wing snaped on next turn ..again near the fuselage.... even carbon rod broke... i dont get how these Flite Test guys get away with just foam... im just going back to my 6 mm wings with wood spars and foam ribs..((
Sep 15, 2017, 09:01 AM
Registered User
Quote:
Originally Posted by tolyaba
...ok i pulled max on elevator when i lost orientation while trimming the plane was upside down resulting in a very sharp loop then aftet the loop the wing snaped on next turn ..again near the fuselage.... even carbon rod broke... i dont get how these Flite Test guys get away with just foam... im just going back to my 6 mm wings with wood spars and foam ribs..((
Were you also at high throttle setting? If yes, maximum elevator coupled with high throttle (especially for a moderate-to-high wing loading, which your Spitfire may have) is a recipe for disaster without a very beefy spar or spars.
The flitetest guys are probably not pulling insane G's like you did.
Sep 15, 2017, 09:04 AM
flyin' fool
goldguy's Avatar
Tape.
Sep 15, 2017, 09:48 AM
Registered User
Its a 110 cm spitfire with around 600gramms i think its a very light wing loading. Also the airspeed wasnt that great like 20 mph
Sep 15, 2017, 10:45 AM
Registered User
Maybe the stuff i use is not true depron? More like polyprone.. At least it doesnt come with paper layer. Can some one weigth 1 square meter of 3 mm depron you are using ( without paper)
Sep 15, 2017, 01:44 PM
An itch?. Scratch build.
eflightray's Avatar
It seems I have run out of 3mm Depron so weighed a 6mm sheet.

Sheet 1000mm x 350mm x 6mm thk = 75g

I calculate that a square meter at 3mm thk as 107g (plus or minus a week ).

It's not just the weight though, 'Depron' may have other properties depending on who manufactures it.

UK Depron never had paper backing.


Ray.
Sep 15, 2017, 02:43 PM
flyin' fool
goldguy's Avatar
True/real Depron has a hard shiny finish on both sides, unlike other underlay type foams.
Sep 15, 2017, 03:37 PM
Registered User
mine weights 130 and is shiny.......
i guess its my new job to stress test the wings.... 3 plane snaps in a row that must be a record
Sep 15, 2017, 03:44 PM
Registered User
What i'm thinking now maybe the way i mount the wings in the fuselage is the problem...
maybe cutting 2 holes on the sides and sliding the wing inside is stressing the wing somehow....
Maybe making a horizontal stiff "bed" and gluing to a bigger surface will help.
Sep 16, 2017, 12:02 PM
Registered User
Quote:
Originally Posted by tolyaba
What i'm thinking now maybe the way i mount the wings in the fuselage is the problem...
maybe cutting 2 holes on the sides and sliding the wing inside is stressing the wing somehow....
Maybe making a horizontal stiff "bed" and gluing to a bigger surface will help.
I wouldn't "rely" on the fuselage at all. Think of flying wings with no fuselage. The spar(s) in the wing should be doing the job. Stressing the spar on the ground (even before it ever gets installed in the wing) so that you know its max load is the least painful way. You risk only a snapped spar
Sep 17, 2017, 12:54 PM
Laughs at un-boxing videos...
basicguy's Avatar
Carbon is a neat material but it is not strong at all under compression loads. In other words the top of spar when you are using up elevator. Compressed carbon will delaminate and fail very quickly carbon has great strength under tension (being pulled at the ends).

Carbon tubes also are not equal I have had hobby king tubes which were very easily crushed.

If you want to use those carbon spars take one of your broken ones and put it at the center in addition to a full span spar. The center has the highest loads by far.

You could glue the shorter spar on top of the full length spar or even lay it along side the full length.
Sep 17, 2017, 03:52 PM
Registered User
currently building edge, using double full length wood spar from pine i think, with ribs hope it holds....
let you guys know by friday ;D


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