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Old Oct 25, 2012, 04:25 AM
speed is always addictive lol
Joined Mar 2009
50 Posts
Help!
wing failure of the balsa f5d

had built 5 balsa f5d but they all crashed by the wing failure......
the wing structure was the combination of 3mm balsa/carbon stripe 0.6*1.0mm spar, 3mm balsa ribs, and 1mm balsa skin, all components were glued together.

is there any buddy can tell me whether i can build a strong enough balsa f5d? or is there anyone had built sucessfully??

how do you guys design yours?? looking forward to you guys.

regards!
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Old Oct 25, 2012, 04:59 AM
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Sunfire's Avatar
Joined Jul 2007
244 Posts
wow looks nice

I don't know bout f5d but me and Joe Yap have built foam core wings for s400 class

http://www.rcgroups.com/forums/showthread.php?t=1289523

the wing was like
from bottom to top

foam core / carbon strip 1 inch / medium fibreglass / hard balsa skin 1mm / monokote

mine was crude vacuum bagged with Elmers Pro Bond

it can take maybe 80 - 100 mph ? I have put a het 3w which is a mega 3 turn into it. did some nice turns but mostly 300 watts plus
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Old Oct 25, 2012, 05:23 AM
I am actually really slow
SlowBarless's Avatar
Brisbane
Joined Jun 2008
969 Posts
Need alot more carbon in the spars. Also a proper shearweb would help. Are you laminating the carbon spars yourself or just buying off the shelf carbon strips?
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Old Oct 25, 2012, 09:09 AM
speed is always addictive lol
Joined Mar 2009
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Quote:
Originally Posted by Sunfire View Post
wow looks nice

I don't know bout f5d but me and Joe Yap have built foam core wings for s400 class

http://www.rcgroups.com/forums/showthread.php?t=1289523

the wing was like
from bottom to top

foam core / carbon strip 1 inch / medium fibreglass / hard balsa skin 1mm / monokote

mine was crude vacuum bagged with Elmers Pro Bond


it can take maybe 80 - 100 mph ? I have put a het 3w which is a mega 3 turn into it. did some nice turns but mostly 300 watts plus

have read joe's thread, nice job he did and his wing should be strong enough to carry the Gs it produces.

but my wing has a span over 1.4m and aspec ratio about 10, emm~ means mine will produce much more bending moment at the wing root...

had a mind of making my wing with foam core, but failed to begin sonce i didn't really think it will be still strong enough at my size.
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Old Oct 25, 2012, 09:49 AM
Even that isn't fast enough
United States, OK, Edmond
Joined Sep 2004
284 Posts
Have you looked at the Ninja Speed build thread? I think that would be very helpful in your endeavor. The wing built in that thread seems to be up to the task.
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Old Oct 25, 2012, 10:05 AM
speed is always addictive lol
Joined Mar 2009
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Quote:
Originally Posted by SlowBarless View Post
Need alot more carbon in the spars. Also a proper shearweb would help. Are you laminating the carbon spars yourself or just buying off the shelf carbon strips?
in the attached pics was the last crashed wing, the plane named yoga. 0.9m length and 1.44m for span, the foil was mh32 and flight weight was about 600 grams, powered by a 3000kv h2218 outer tuner heli motor, 4.75*4.75 apc prop.
the spar was glued with balsa wall in the center and carbon stripes bars, like the pics show.

crashed into pieces because of losing control.

i test the same spar with sports on each sides away from 35 cm from the center point, applied 4kg load at the center with no failure. so about how many Gs it can carry can we say?? or upto what speed it can handle if i'll replace more powerful motor?
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Old Oct 25, 2012, 10:30 AM
speed is always addictive lol
Joined Mar 2009
50 Posts
Quote:
Originally Posted by why_fly_high View Post
Have you looked at the Ninja Speed build thread? I think that would be very helpful in your endeavor. The wing built in that thread seems to be up to the task.
hi, why_fly_high, thank you for your reply, but couldn't find the thread, can you post me the link by the way? many thanks.
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Old Oct 25, 2012, 11:16 AM
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United States, AL
Joined Apr 2007
832 Posts
With such a thin and high aspect ratio the glued points of a built up wing are huge stress points. I'm no expert plane designer but I would think a foam core wing would be better than a built up balsa as the shear forces would be distributed over the entire wing surface instead of concentrated at the glue joints of a built up wing.

Is the shear web on the failed wings broken? How is the wing attached to the fuselage? All that wood cut away from the wing center is a huge stress riser, you need as much strength at the root as possible!
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Old Oct 25, 2012, 11:20 AM
I am actually really slow
SlowBarless's Avatar
Brisbane
Joined Jun 2008
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Quote:
Originally Posted by bigcatdairy View Post
in the attached pics was the last crashed wing, the plane named yoga. 0.9m length and 1.44m for span, the foil was mh32 and flight weight was about 600 grams, powered by a 3000kv h2218 outer tuner heli motor, 4.75*4.75 apc prop.
the spar was glued with balsa wall in the center and carbon stripes bars, like the pics show.

crashed into pieces because of losing control.

i test the same spar with sports on each sides away from 35 cm from the center point, applied 4kg load at the center with no failure. so about how many Gs it can carry can we say?? or upto what speed it can handle if i'll replace more powerful motor?
With a 4kg load at 600rtf, safe to say around 7G's. Keep in mind a typical F5D plane will pull close to 35G in a hard turn. You really need to stregthen the main spar for it to work. Make the spar caps thicker and wider. Try to source end grain balsa for the shearweb as it's compressive properties are superior to standard cut balsa. Really you might be better off learning how to mould your own? A balsa F5D will never be as strong as the mouldies can be.

Also, you're doing an awesome job with the build! Looks really nice and it's good to see something different.
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Old Oct 25, 2012, 11:33 AM
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Canada, SK, Prince Albert
Joined Jan 2006
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Here is my built up wing: http://www.rcgroups.com/forums/showthread.php?t=1506582

The outside was glassed....crashed the plane and the Fuz was destroyed...BUT I still have the wing which was not damaged...Tuff.

Oh Yeah, that is beautiful wood work!
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Old Oct 25, 2012, 12:24 PM
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Canada, SK, Prince Albert
Joined Jan 2006
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I looked at some close ups of your wing pics. It looks like you have tow on top and bottom of a balsa or hard wood strip. Like some of the other guys have said F5D pulls some serious G's. You need carbon box or rods run through the length of that wing and I would use two. Did you glass the outside of the wing surface or just cover it?

I know these steps add weight and no one wants that...but to pull f5D turns there is no way around it! Two carbon spars inside that wing might help with the wing twisting around the carbon you already have when the speed starts to go up.
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Old Oct 25, 2012, 12:49 PM
speed is always addictive lol
Joined Mar 2009
50 Posts
thank you arcticflyer, i have read your post, and have some question:
1 i saw you were using 2 carbon bar as main and 2ndary spar, was it regid enough?
2 how's your power train?
3 is that mh43 you used fast enough?
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Old Oct 25, 2012, 01:01 PM
speed is always addictive lol
Joined Mar 2009
50 Posts
Quote:
Originally Posted by SlowBarless View Post
With a 4kg load at 600rtf, safe to say around 7G's. Keep in mind a typical F5D plane will pull close to 35G in a hard turn. You really need to stregthen the main spar for it to work. Make the spar caps thicker and wider. Try to source end grain balsa for the shearweb as it's compressive properties are superior to standard cut balsa. Really you might be better off learning how to mould your own? A balsa F5D will never be as strong as the mouldies can be.

Also, you're doing an awesome job with the build! Looks really nice and it's good to see something different.
slowbarless,

600g of rtf weight is a smooth power train, with standard f5d power i believe the total weight will be around 1kg. means my spar or my wing gonna be stayed in 1 piece with about 40kg of loading at the center and with same of the rest test condition above......

and 35Gs to 7Gs, pretty distance to a real f5d, since i don't have a special work shop and unexperience in molding technique lack of budget etc, i would like to try to use foam core with glass reinforement as a 2nd step, to see what will happen.

anyway, 35~40Gs is my goal, hope to get it. thank you very much for your advise
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Old Oct 25, 2012, 03:23 PM
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Deutschland, RP, Niederzissen
Joined Dec 2011
883 Posts
Pretty nice challange!!

First you have to watch the forces created by the F5d- style flying, as mentioned the G-forces are a main part but at a wingspan of 1400mm and the typical F5d wingarea torsionforces may be your neckbreaker!!

years ago we build some F5d Flippers for F5d limited competition (800g) with oracovered balsaskin with foam core out of the mould as it was required by regulation, we did not pay much attention at the spar,( if i remember right we just took steped 3 or 4 rovings at top and bottom but we used carbonweave underneath the balsa shell!

Just check out a typical F5d wing, its a carbon -balsa- glasfibersandwich with a solid spar.
Maybe its possible to get such a sandwich without a mould, i think the foam core will be the best way to get it.
this (german)thread may give some inspiration:

http://www.rc-network.de/forum/showt...Funjet-Antrieb.
If necessary i can translate.

The 2/3 has less wingspan with slightly higher wingarea so airfoil is thicker and stiffness is less challenging.
But it is able to performe 220mph at 1,1 Kg even with a nervous stickfinger(but sure with less than 35G!!)

To be honest, i dont think you will be able to get the same performance in corner or topspeed than a moulded F5d but if you would manage to get somehow close it may be much more satisfying than just buying one!

If you need help with spar dimentioning or other F5d buiding technics just ask!

Regards

Yello
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Old Oct 25, 2012, 04:53 PM
speed is always addictive lol
Joined Mar 2009
50 Posts
Quote:
Originally Posted by Mreyello View Post
Pretty nice challange!!

First you have to watch the forces created by the F5d- style flying, as mentioned the G-forces are a main part but at a wingspan of 1400mm and the typical F5d wingarea torsionforces may be your neckbreaker!!

years ago we build some F5d Flippers for F5d limited competition (800g) with oracovered balsaskin with foam core out of the mould as it was required by regulation, we did not pay much attention at the spar,( if i remember right we just took steped 3 or 4 rovings at top and bottom but we used carbonweave underneath the balsa shell!

Just check out a typical F5d wing, its a carbon -balsa- glasfibersandwich with a solid spar.
Maybe its possible to get such a sandwich without a mould, i think the foam core will be the best way to get it.
this (german)thread may give some inspiration:

http://www.rc-network.de/forum/showt...Funjet-Antrieb.
If necessary i can translate.

The 2/3 has less wingspan with slightly higher wingarea so airfoil is thicker and stiffness is less challenging.
But it is able to performe 220mph at 1,1 Kg even with a nervous stickfinger(but sure with less than 35G!!)

To be honest, i dont think you will be able to get the same performance in corner or topspeed than a moulded F5d but if you would manage to get somehow close it may be much more satisfying than just buying one!

If you need help with spar dimentioning or other F5d buiding technics just ask!

Regards

Yello

yello, that's very nice of you and your reply was kinda inspiring me much. i think i can understand what whey said at the thread with the help of google translate, can i make a longer span wing using the same method with doing addition reinforcement?

i have a lot of questions for designing/constructing a f5d pylon racer since i don't have any experience beside making those 5 crashed planes. lol

for example, how can i choose a right airfoil? how can i overcome the potential problem will cause by the torsion force? how will the assembling torlerance will effect the performance? and how can i read the aerodynamic parameters of the airfoil? what can i do if i can't buy a proper prop at the local market, can i mould it myself?

i can put all those questions an further to you if you don't mind

time and patient won't be a problem for me.

Sounds like a plan to buy a commercial plane for experiencing extreme performance. but i like to let u know that beside the 5 crashed pylon racers, i totaled 3 additional well designed commercial planes in 2 monthes think i can't afford for 3 F5D lol... and love the feeling of challange, so i'll keep developing it my own.

what do you think about I spar and round spar? which one will be better or their + and - ?

could you please pm me your email by the way?
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