high-lift camera foamie... - Page 4

vpatron · Nov 01, 2009, 08:08 PM

Hi Randy,

CG would be similar to the original airfoil, I would think. As Michal mentioned, I'd move it slightly forward for better stability. I would do 25% of chord, no more. I don't know about 20%; you will already have pitch issues with the extreme undercamber.

Basically, your wing is like a normal Clark-Y but will flaps on full deflection! When a wing is curved like that, the tendency of the wing is to "roll over forward" (I'm saying roll as in rotate, not roll as in the roll axis. Technically, I should say an undercambered wing will tend to pitch nose down.) The more the undercamber, the greater the tendency. This has to be compensated for by either more elevator, or increasing the angle of attack of the wing until it's basically pointing up enough that the negative pitch tendency is zero. This is basically the same thing as giving it up elevator.

Anyway, I had the same issue on my design. I kept increasing the angle of attack of the wing by 2 degrees. I think the one I'm flying now has 8 degrees and I still have to put quite a bit of up elevator for level flight. I'm too lazy to build a new fuse so for past 2 years my plane just has a lot of up elevator...

You can determine this empirically by just adding shims under the leading edge of the wing until you get a flat elevator for level flight.

I'm not a big airplane designer or anything. Same as you, I just take off-the-shelf designs and modify for special needs...

For a maiden, I'd just keep the plane as light, ugly and simple as possible in case of a crash. I would even go as far as using a small battery and strapping it outside with rubber bands along with a bit of velcro or sticky tape to keep it from moving. If you do crash, having a heavy battery inside can do a lot of damage. And fly over grass or at least dirt. Lipo hitting cement can be bad. Good luck!

-Vince

Quote:

Originally Posted by rjarois

Vince, it seems to me you have more advanced knowledge of aerodynamics's than i do...would you have any cg recommendation for this high-lift wing?? is it the same as a Clark-y? i have no clue as were to have on the first flight. i was going to have it on the first 30% . would you do any thing different?. thanks for any input from anyone regarding the cg. thanks. randy.

rjarois · Nov 01, 2009, 08:20 PM

thanks vince....keepin it ugly isnt a problem..lols the first flight will be shortly, and hopefully i can get video. randy.

springer · Nov 01, 2009, 09:12 PM

Some time ago,I made a Trainer 1.5 (T1 at 150%) using a folded foil that looks a lot like that, and folk said it looked like an Eppler 377 foil. It flew very nicely, and led me into the doubled leading edge 50% step KFM airfoil that's been called KFC (now officially a KFM5, I think) Got that one on a 42" Blubaby that carries my 3oz cam. emax2822, 1060dd prop on 3s will fly her almost straight vertical to altitude on fresh pack. Then cut motor and glide around snapping pics. If your's flys like that (or better), you are in good shape!

rjarois · Nov 01, 2009, 09:39 PM

springer, man i hope your rite!!! that would be great. randy.

Real Ira · Nov 01, 2009, 09:42 PM

Been looking more closely at the pic's and am inclined agree.
Initial trim may be a bit busy but once dialed in it should be a nice slow flier.

I would do first flight on a very calm day and go for altitude as best you can, then power way back and work on trim adjustments. Aw heck, you already know that.
Good Luck!

rjarois · Nov 01, 2009, 10:07 PM

lols...thanks IRA...i do need the positive reinforcement, lols.....randy.

AP Kihala · Nov 02, 2009, 10:39 AM

Hi,

I am using undercambered airfoil for more than 2 years & it provides good lift. Only thing it needs is a fair amount of downthrust or down elevator during take off. Overall you will love undercambered airfoil. I have a scan of my airfoil. pm me your email id if you want it.

APK

rjarois · Nov 02, 2009, 07:00 PM

got a chance to get out this morning and get the hi-lift wing its first flight....the model was very pitchy...trimmed for level flight at half speed, its fine. give some throttle and the thing would loop, lols. cut the power, and it would dive down on a 45 deg angle...i made two flights, with a cg change, and although the model flies great at any certain speed, and it lands at a walking speed...the pitch problem....well lets just say I'm not going to deal with that carrying a camera. i made the decision to go back to the Clark-y, as its proven on the smaller model...i programmed the wing the same with the 2 deg, tip washout. I'm not sure why, but the fellas on the e-zone told me it would fly very pitch sensitive...they were right. that's the beauty of the cnc machines...pull up the file, and wham ya got a new wing fast. i just cut out the Clark-y airfoil on the phlatty and used as a layout template for the fuse saddle...easy fix...so any how, i will re maiden in a few days, after i glue up the new wing....randy.

DiveBombDave · Nov 02, 2009, 08:02 PM

it needed more downthrust.

Dave

Real Ira · Nov 02, 2009, 09:04 PM

How did it fly power off?

rjarois · Nov 02, 2009, 10:07 PM

Quote:

Originally Posted by Real Ira

How did it fly power off?

ira, the model flew great....at any given speed....if i trimmed for power off, when ya give it power, it would do a loop, lols....if ya trimmed for half power, when ya killed the power, it would go into a 45 deg, dive..and trimmed at half throttle if ya give it full the thing went straight up, lols....it was the dumbest thing i ever seen...i wrote this on the phlatboyz forum...ever since i built my cnc, i kinda hang ther alot...randy.

yea, i hear ya bird...with the high-lift foil, you would ether do a throttle mix that gave full down with more throttle, or get like a 45 deg down thrust angle....man i never seen anything like it, lols...well i will have the new wing remade by tomorrow, so its no biggie...all i have to do is glue on the spar strap. also i took out that noob flier polyhedral out...don't know why i even made with it to start with, lols. also the new wing i made a even 60in. span. my original magpie had a 54in....i just gave 3in more a side...it will be ready to re maiden when the weather is rite....should be in a few days, at most. here is a photo of the new wing differences. randy.

highflier · Nov 02, 2009, 10:21 PM

I would not give up so quick.

1) Adjust CG until trim was near neutral, at a good glide speed.

2) Add downtrust to the motor so that you do not balloon up on throttle.

3) Tweak flight with Throttle to elevator trim. I do that all the time when I am to lazy to add downthrust.

you might want to do a flight test with a chunk of lead = to you camera setup. You might find you like the lift effect of the wing and continue to put some effort into getting the setup right.

Highflier

AP Kihala · Nov 02, 2009, 10:25 PM

Hi,

undercambered wing's CG fall at 1/2 chord. Set CG at 1/2 chord & you will be amazed by the rersults.

APK

rjarois · Nov 02, 2009, 10:29 PM

yea highflier, i hear ya man...but i gave up banging my head on the wall years ago, lols. i only wish my friends could of got video..i knew the whole thing was a experimental wing project goin into...i have a small version of this model also with a Clark-y airfoil, and its a proven flier. randy.

rjarois · Nov 02, 2009, 10:32 PM

Quote:

Originally Posted by AP Kihala

Hi,

undercambered wing's CG fall at 1/2 chord. Set CG at 1/2 chord & you will be amazed by the rersults.

APK

like make it more tail heavy??

Nov 02, 2009, 07:00 PM	#53
rjarois Registered User Join Date: Sep 2004 Location: royal oak, michigan Posts: 1,386	morning maiden... got a chance to get out this morning and get the hi-lift wing its first flight....the model was very pitchy...trimmed for level flight at half speed, its fine. give some throttle and the thing would loop, lols. cut the power, and it would dive down on a 45 deg angle...i made two flights, with a cg change, and although the model flies great at any certain speed, and it lands at a walking speed...the pitch problem....well lets just say I'm not going to deal with that carrying a camera. i made the decision to go back to the Clark-y, as its proven on the smaller model...i programmed the wing the same with the 2 deg, tip washout. I'm not sure why, but the fellas on the e-zone told me it would fly very pitch sensitive...they were right. that's the beauty of the cnc machines...pull up the file, and wham ya got a new wing fast. i just cut out the Clark-y airfoil on the phlatty and used as a layout template for the fuse saddle...easy fix...so any how, i will re maiden in a few days, after i glue up the new wing....randy.

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Nov 01, 2009, 08:20 PM	#47
rjarois Registered User Join Date: Sep 2004 Location: royal oak, michigan Posts: 1,386	thanks vince....keepin it ugly isnt a problem..lols the first flight will be shortly, and hopefully i can get video. randy.

Nov 01, 2009, 09:12 PM	#48
springer treefinder Join Date: Oct 2004 Location: SE MI Posts: 2,709	Some time ago,I made a Trainer 1.5 (T1 at 150%) using a folded foil that looks a lot like that, and folk said it looked like an Eppler 377 foil. It flew very nicely, and led me into the doubled leading edge 50% step KFM airfoil that's been called KFC (now officially a KFM5, I think) Got that one on a 42" Blubaby that carries my 3oz cam. emax2822, 1060dd prop on 3s will fly her almost straight vertical to altitude on fresh pack. Then cut motor and glide around snapping pics. If your's flys like that (or better), you are in good shape!

Nov 01, 2009, 09:39 PM	#49
rjarois Registered User Join Date: Sep 2004 Location: royal oak, michigan Posts: 1,386	springer, man i hope your rite!!! that would be great. randy.

Nov 01, 2009, 09:42 PM	#50
Real Ira Ya, THAT Ira Join Date: Jan 2006 Location: Coupeville, Wa Posts: 4,642	Been looking more closely at the pic's and am inclined agree. Initial trim may be a bit busy but once dialed in it should be a nice slow flier. I would do first flight on a very calm day and go for altitude as best you can, then power way back and work on trim adjustments. Aw heck, you already know that. Good Luck!

Nov 01, 2009, 10:07 PM	#51
rjarois Registered User Join Date: Sep 2004 Location: royal oak, michigan Posts: 1,386	lols...thanks IRA...i do need the positive reinforcement, lols.....randy.

Nov 02, 2009, 10:39 AM	#52
AP Kihala Registered User Join Date: Jun 2009 Posts: 29	Hi, I am using undercambered airfoil for more than 2 years & it provides good lift. Only thing it needs is a fair amount of downthrust or down elevator during take off. Overall you will love undercambered airfoil. I have a scan of my airfoil. pm me your email id if you want it. APK

Nov 02, 2009, 08:02 PM	#54
DiveBombDave Pull out early! Join Date: Jan 2005 Location: Lexington, KY Posts: 1,956	it needed more downthrust. Dave

Nov 02, 2009, 09:04 PM	#55
Real Ira Ya, THAT Ira Join Date: Jan 2006 Location: Coupeville, Wa Posts: 4,642	How did it fly power off?

Nov 02, 2009, 10:21 PM	#57
highflier Speed cost money. Join Date: Dec 2002 Location: Holland, Pennsylvania, United States Posts: 2,508	I would not give up so quick. 1) Adjust CG until trim was near neutral, at a good glide speed. 2) Add downtrust to the motor so that you do not balloon up on throttle. 3) Tweak flight with Throttle to elevator trim. I do that all the time when I am to lazy to add downthrust. you might want to do a flight test with a chunk of lead = to you camera setup. You might find you like the lift effect of the wing and continue to put some effort into getting the setup right. Highflier

Nov 02, 2009, 10:25 PM	#58
AP Kihala Registered User Join Date: Jun 2009 Posts: 29	Hi, undercambered wing's CG fall at 1/2 chord. Set CG at 1/2 chord & you will be amazed by the rersults. APK

Nov 02, 2009, 10:29 PM	#59
rjarois Registered User Join Date: Sep 2004 Location: royal oak, michigan Posts: 1,386	yea highflier, i hear ya man...but i gave up banging my head on the wall years ago, lols. i only wish my friends could of got video..i knew the whole thing was a experimental wing project goin into...i have a small version of this model also with a Clark-y airfoil, and its a proven flier. randy.