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Old May 13, 2012, 12:03 AM
Build something.
Nodd's Avatar
United States, CT, Fairfield
Joined Mar 2012
688 Posts
Maiden Flight Details
Well the video was fun but I left out a few details. So before you ask...

I used a 2100mAh 3S battery. I landed after 15 minutes not because the battery was getting low but because I didn't want to push my luck on the first flight. I believe I made four, maybe five, climbs during the flight. The battery was at 11.02v when I checked her after the flight, so still had plenty of juice for a few more climbs.

I didn't try to do any thermalling, instead the flight was spent playing with the elevator trim mostly, the rudders & ailerons didn't need trimming. You may notice at the end of the video I show there's maybe an 1/8" of up trim on the ruddervators. The tail was mounted at 1° to the plane's datum line. In hindsight it could probably have used a tad more incidence.

You can't really tell in the video but the flaps & crow mixing were pretty effective. I tried them out while nice & high. It produced a fair amount of ballooning when I dumped in full flaps but that's to be expected. Fed in slowly & with the down elevator I mixed in, the flaps behave nicely. I put them to good use in my rather over extended landing.

Currently I have very little crow mixing, the ailerons move perhaps a 1/4" up at most. I'll play with it more but I think I'm going to stick with the flaps as the main speed brakes so that the ailerons don't get all mushy on me.

Important safety tip! DO NOT mess with the trim when you're 20' off the ground & in a hard turn. Not sure what I was thinking but as the video shows, I took my eyes off the plane for a split second & almost sent her piling straight in. I'm SOOOO glad I was able to recover in time, would never have forgiven my self.

Some may have noticed my ESC was set to slow start. I did this just for the maiden flight. I thought without a proportional throttle it might be nice to have the motor spin up to speed gradually instead of all or nothing. I'll be setting it back to normal after I'm done messing with the throttle to elevator mixing.

The middle position on my three-way throttle switch was set at 30% thrust. Turns out that's pretty wimpy. I think I'm going to increase that to 50%. At 100% she climbs out very nicely though. I think I may have nailed the motor/prop combo.

I will be producing plans for this sailplane. I'll let you all know when those become available.

Anyway that's all I can think of for now. Thank you once again for following my build & a HUGE thanks to those who offered advice.
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Old May 13, 2012, 02:55 AM
f5b-uk
Mike Seale's Avatar
United Kingdom, Dorset
Joined May 2002
3,065 Posts
Excellent work. You must be chuffed with the result of your hard work? The way it responded to your low altitude trimming suggests it is set up well and has no nasty habits.

Mike
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Old May 13, 2012, 05:29 AM
Registered User
Portugal, Faro District, Almancil
Joined Feb 2008
306 Posts
Nodd absolutely beautiful!!!!! Love the gull wing and the pod and boom design. If you give me the plan (lol) i will use a aluminium boom because i have 10 of them already , and when you say you had 1 degree on the vtail to datum line how did you do this with a vtail, im quite familiar with this process on a t tail but cant get my head round it on a v. Also i have this setup waiting

emax 950kv bl 2826/06 motor BL2826 12.0V 13X6.5 (Thin) 8400 61A 2650g

and a emax 60 amp esc.

is this enough to power this glider as this motor weighs around 180g
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Old May 13, 2012, 06:53 AM
Red Merle ALES
Curtis Suter's Avatar
United States, Mt, Helena
Joined Apr 2002
5,481 Posts
Quote:
Originally Posted by Nodd View Post
Maiden Flight Details

I didn't try to do any thermalling, instead the flight was spent playing with the elevator trim mostly, the rudders & ailerons didn't need trimming. You may notice at the end of the video I show there's maybe an 1/8" of up trim on the ruddervators. The tail was mounted at 1° to the plane's datum line. In hindsight it could probably have used a tad more incidence.
Congratulations on the maiden. Very nicely done video as well!

Once you perform more precise balance tests such as the "dive test" my guess is you'll remove a little nose weight and by doing so you can then decrease a little of that up elevator trim. However, don't beat yourself up too much on that amount of trim as aerodynamically it makes little or no difference if it's centered or not, well unless grossly in error which it is not. If you don't believe me I'll post what Dr. Drela says about that.

Quote:
A more precise and technical answer is reprinted below from Mark Drela in the Allegro-Lite YAHOO group, message #6005;

The importance of decalage is way overblown.

First of all, if you have an all-moving tail, then obviously "setting
the decalage" has no meaning. You just set the elevator trim to
whatever it has to be for your CG position and desired trimmed speed.

It turns out that for a hinged elevator, decalage should also have
little effect. You can change pitch trim either by moving the
elevator or moving the entire tail. There should be little or no
difference in pitch stability or elevator response between the two
types of changes. This assumes that the tail airfoil is reasonably
good, and the elevator deflection is modest so that the tail's
cl(alpha) and cl(elevator) curves are still linear. The only reason
to change the decalage (angle of the front stabilizer) in this case is
to null out the elevator trim deflection. This will give more
symmetric elevator range, reduce elevator servo load at high speed,
and perhaps reduce the tail's profile drag very slightly.

If there IS a difference in handling from a change of decalage, then
you surely have poor airfoil flow over the tail, with some combination
of dead band or hysteresis. This also indicates the presence of large
separation bubbles and high profile drag. A simple slab airfoil with
a semi-circular LE is very common, and is prone to these types of
problems. Making the LE more elliptical rather than round should give
a significant improvement.
Curtis
Montana
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Old May 13, 2012, 07:35 AM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
Joined Dec 2010
6,830 Posts
nice !
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Old May 13, 2012, 07:50 AM
Balsa builder and balsa basher
RC Trainer plane's Avatar
Joined Apr 2012
683 Posts
Superb design, excellent build and a great maiden flight well done
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Old May 13, 2012, 11:15 AM
f5b-uk
Mike Seale's Avatar
United Kingdom, Dorset
Joined May 2002
3,065 Posts
Quote:
Originally Posted by CloudyIFR View Post
Once you perform more precise balance tests such as the "dive test" my guess is you'll remove a little nose weight
I don't think he's got any nose weight to remove!

Quote:
Originally Posted by Nodd View Post
I added a little over an ounce of lead to the tail & she's now sitting pretty on my CG stand.
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Old May 13, 2012, 12:41 PM
Good, fast or cheap, pick two
robh's Avatar
Napa, California
Joined Jul 2006
2,602 Posts
Awesome project Nodd! Very inspirational and she looks like you've got a winner there! Please keep us posted as to how she shakes out?

Rob
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Old May 13, 2012, 12:43 PM
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Nodd's Avatar
United States, CT, Fairfield
Joined Mar 2012
688 Posts
Yeah I'm not really worried about the elevator trim, I don't mind that. I'm just thinking ahead, like for the plans, I could increase the tail's angle of incidence from 1° to 1½° perhaps. That'd help center the elevators. I could also address the nose heavy issue with a slightly shorter nose or maybe a slightly larger diameter tail-boom. She's a work in progress, this being the prototype. I still need to play around with dive tests & see if changing the CG makes sense. Lots of fun stuff to do.
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Old May 13, 2012, 12:50 PM
Balsa builder and balsa basher
RC Trainer plane's Avatar
Joined Apr 2012
683 Posts
This is one of the best builds i've seen for a long time, becuase you kept us informed from the design to the maiden
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Old May 13, 2012, 01:38 PM
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Nodd's Avatar
United States, CT, Fairfield
Joined Mar 2012
688 Posts
Quote:
Originally Posted by MAT1978 View Post
Nodd absolutely beautiful!!!!! Love the gull wing and the pod and boom design. If you give me the plan (lol) i will use a aluminium boom because i have 10 of them already , and when you say you had 1 degree on the vtail to datum line how did you do this with a vtail, im quite familiar with this process on a t tail but cant get my head round it on a v. Also i have this setup waiting

emax 950kv bl 2826/06 motor BL2826 12.0V 13X6.5 (Thin) 8400 61A 2650g

and a emax 60 amp esc.

is this enough to power this glider as this motor weighs around 180g
I'm not going to guess at motor setups as I'm far from an expert. So far I've gotten lucky with just two out of three planes. The third, my Texan, barely has enough power to maintain level flight. If the emax 950kv is comparable to the Turnigy G15 710kv then it might workout.

An aluminum tail-boom should be fine assuming it thick enough. The CF rod I'm using, while impressively strong on the bench turned out to be marginal at best on the glider with a fair amount of flex in the tail. It could stand to be a little stronger but as long as I behave my self & keep the speed & G's down it should be fine, fingers crossed.

The 1° angle of incidence on the tail means the entire v-tail assembly is angled up slightly. Here maybe this diagram will help...



Doesn't really matter if its a conventional, T or V tail, the horizontal stabilizing surfaces are generally angled up very slightly to counter the wings natural tendency to dive. At least that's my understanding of it.
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Old May 13, 2012, 02:39 PM
skumgummi dave
Gresham, OR.
Joined Mar 2004
1,829 Posts
Nodd:

Thanks for sharing your build and the maiden video. Bravo!

Dave-
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Old May 13, 2012, 08:15 PM
Joined Nov 2011
89 Posts
Nodd really nice, great job.

Audience Claps (0 min 27 sec)
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Old May 13, 2012, 09:45 PM
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Nodd's Avatar
United States, CT, Fairfield
Joined Mar 2012
688 Posts
LOL thanks for the applause, much appreciated.
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Old May 14, 2012, 08:59 AM
Registered User
Joined Mar 2007
65 Posts
Nodd,

good job... and very well documented!!!

Did you use tape to fix the wing tips to the center panel?

Best Regards
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