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V tail setup?

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Old 06-08-2011, 10:31 AM
  #1
stick man
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Default V tail setup?

I'm building a Salto H101 with V-tail and trying to get my mind around the servo/rx connections (DX7/AR500) as well as any mixes that may be needed, which seem crucial with the V.

Anyone have experience with this?
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Old 06-13-2011, 07:13 AM
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Default RE: V tail setup?

I have flown 3 different 'V' tail airplanes. One of two power planes had so much engine torque the rudder was ineffective until sufficient groundspeed obtained (not good). One was a Spirit sailplane with a flattened (not polyhedral) wing and ailerons. I didn't need any special mixes. Each control function seemed to work independantly well without the need for mixes. The 'V' was set at 110 degrees. Rudder authority was average. Ailerons needed to 'core' thermals better. I could have mixed ailerons to 'V' tail but I got used to it. It would make a nice experiment to have the same wing and two fuselages- one traditional and one 'V'- for comparison. Hope this helps.
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Old 06-13-2011, 08:45 AM
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Default RE: V tail setup?

Thanks, ARUP. I was able to sort out the servo wiring and functions, so I'm good there.

Also, I'm considering a mild mix of ailerons to rudder (maybe 7-10%?) for no other reason except the geometry of the V-tail seems like it would tend to roll the plane left when giving right-rudder input. Has anyone else tried this?

Fingers crossed, I hope to maiden this week.
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Old 06-13-2011, 11:00 AM
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Default RE: V tail setup?

One you have your V-tail servos sorted out, do your mixing exactly as you would on a regular tail.  Then tune to taste.
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Old 06-13-2011, 02:24 PM
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Default RE: V tail setup?

I've not noticed adverse roll when turning, I use coupled ailerons and rudder (switchable) and the v tail acts like rudder not ailerons.
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Old 06-13-2011, 04:07 PM
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Default RE: V tail setup?

When setting up a V tail, yaw response is improved if you run differential on the ruddivators. A little more up throw then down just the same as ailerons.
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Old 06-13-2011, 09:56 PM
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Default RE: V tail setup?

Thanks, guys.

So I maidened the Salto today and now I have a new problem, I crashed it!

The first problem was that (Ithink) it was way too windy, because when Ihand launched it, it really took off, rapidly gaining altitude and sort of darting around. It flew pretty good but also seemed unstable. Ihad too really work the controls to keep it steady. But I'm not sure if it was the high wind factor, or the CG is off, or BOTH.

Its not too badly damaged so I will try again. But next time I'll add some weight to the nose and wait for a day thats not as windy.
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Old 06-13-2011, 10:02 PM
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Default RE: V tail setup?

Always try to maiden a new plane in calm to near calm conditions.   You can't tell anything about set-up if it is windy or gusty.
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Old 06-13-2011, 10:29 PM
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Default RE: V tail setup?


Quote:
ORIGINAL: stick man

Thanks, guys.

So I maidened the Salto today and I had too really work the controls to keep it steady. But I'm not sure if it was the high wind factor, or the CG is off, or BOTH.

Its not too badly damaged so I will try again. But next time I'll add some weight to the nose and wait for a day thats not as windy.
Or perhaps you have too much throw on the controls....
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Old 06-14-2011, 06:47 AM
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Default RE: V tail setup?

Sorry to learn of the crash. Go to the 'cgcalculator.com' page and check things out. Too much control throw is the usual suspect and for a Salto (to which I have no experience in flying) types could be disasterous. Good call A10FLYER. The aerodynamically ideal 'V' tail would be an inverted design. I am strictly an armchair aeroengineer and my comments are purely ancetdotal based on some empirical evidence through limited experience!
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Old 06-14-2011, 09:35 AM
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Default RE: V tail setup?

Hmmm... well I do have quite a bit of throw dialed in, so I will take some out before the next try.

Also, the reason I went for it on a windy day is because when I tried to glide my Sonic 185 with no power, it was barely staying afloat in winds of @ 15-20mph. And it only weighs 2.1 lbs, whereas my Salto weighs @ 3.2lbs. So i figured it needed more wind. I guess I was wrong because the Salto seemed to be very efficient.
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Old 06-26-2011, 10:37 PM
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Default RE: V tail setup?

I take it you are attempting slope soaring?

If not then remember - gliders don't fly because of the wind!
They are powered by gravity.
I fly full size gliders and a lot of spectators ask 'What happens if the wind stops?!"
Thermals or slope updrafts merely postpone landing.
Flying in too much wind means your downwind speed relative to you, is higher and up wind slower, and turbulence will disrupt smooth flight.
15-20mph should be plenty to maiden a sloper, provided the slope is suitable, and the plane has been trimmed out properly on low javelin hand tosses first.
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Old 06-27-2011, 02:42 AM
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Default RE: V tail setup?


Quote:
ORIGINAL: stick man

Hmmm... well I do have quite a bit of throw dialed in, so I will take some out before the next try.

Also, the reason I went for it on a windy day is because when I tried to glide my Sonic 185 with no power, it was barely staying afloat in winds of @ 15-20mph. And it only weighs 2.1 lbs, whereas my Salto weighs @ 3.2lbs. So i figured it needed more wind. I guess I was wrong because the Salto seemed to be very efficient.
Oh, you are slope soaring. My earlier comments assumed you were flat field thermal soaring. Slope soaring is completely different although Ioften test slope gliders on flat fields using a hi-start.


How much wind is needed depends on four things things:

Angle of wind to the hill. 5 degrees off dead center makes a difference. 10 degrees off center may be unflyable.
height of the hill - Ihave sloped 4 foot dunes wtih light planes but the 75 foot cliffs are much better.
Angle of the hill - 70 degrees is much better than 45
Wing loading of the glider - 5 ounces/sq ft doesn't need as much wind as 15 oz/sq ftt wing loading.

At many of our hills you can slop soar an Easy Glider in 5 mph winds, if they are straight into the hill.

So what is the WL of your Sonic 185? What is the WL of the Salto?

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Old 06-27-2011, 09:52 AM
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Default RE: V tail setup?

Oh yes, sorry i forgot to include flight location details. This particular spot is a @ 75-80ft Bluff at about 50-60deg. There is always wind to some degree, usually anywhere from 5mph to 40mph (seat of the pants estimation.)

I have also noticed that the air can get quite turbulant, possibly because of the relative angle that the wind is blowing and the irregular face of the Bluff. (the pitch of the Bluff varies in spots too).

I have flown my powered foamie at this location several times now and it is very stable, and if the windspeed is @ 7-8mph (guessing) or above, I can fly without using the motor. I cannot find any specs for the airfoil, etc. but this is the plane-http://www.nitroplanes.com/60a-dy892...185-24ghz.html

The Salto specs are:
Wing Span: 2.45 m (96.5")
Wing Area: 30 dm2 (465 sq. in.)
Wing Airfoil: HN 805
Wing Loading: 46 g/dm2 (15 oz/sq. ft.)
Flying Weight: 1.4 kg (50 oz
http://www.nitroplanes.com/sah12racosa.html


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Old 06-27-2011, 10:21 AM
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Default RE: V tail setup?

A couple of notes.

Be careful of the range on your Sonic, the radio is only rated for 350 feet. That is very short range. You don't want to lose it. I launch my thermal gliders higher than that.



The wing loading on the Salto is about 16 oz/sq ft.. By thermal soaring standards that is a brick, But by slope soaring standards that should be a fast arobatic glider. But it will definatly need more wind than your Sonic.

At 50 to 60 degrees the hill is not very steep. I would think, based on your hill, you are going to need at least15 mph to keep it flying and 20-25 would probably be optimum. That is a total guess, but you are going to need a lot more than the Sonic.

Also, if your Salto was unstable, you may have the CGback a bit too far. Are you balaned according to the instructions?
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Old 06-27-2011, 01:09 PM
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Default RE: V tail setup?

Yes I have been careful not to get the Sonic too far away. No more than 100yds-ish. So far so good.

Regarding the Salto, I thought I would need more wind so on the first attempt I launched it on a day with about @ 17-20mph, again just a guess. It lifted quite nicelybut as I posted earlier, it suddenly dropped a wingtip and spiraled downward. I saved it but was then too low for lift and had to ditch it on the beach below.

On the next attempt (several days later) I added weight to the nose (i also thought that may have been the problem) and went back to the Bluff. It was not as windy this time, maybe 10-15mph, but thinking that it had been too windy the time before, I went ahead and tossed it into the abyss. This time it did not lift as much, it stayed at about the altitude that I had launched, eye level to me as I stood on the edge of the Bluff. All was well, until again, it dipped the right wing and spiraled downward. I recovered but this time it was VERY low, right on top of the water... and trying to make it back to the beach, I came up about 5 ft short and it landed in the shallow surf. Oopsie! The good news is that I was able to salvage the Rx and 2 servos, but shes waterlogged and now hanging on the wall of my garage... pretty to look at but not airworthy.

But to answer your question, yes I moved the CG more fwd than the plans suggested and it still "fell off". Could be turbulance but I just dont know.
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Old 06-27-2011, 08:04 PM
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Default RE: V tail setup?

Sounds like you are letting it slow down too much.   With that high wing loading, it is not going to float like your sonic.  That bird needs to run! 
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Old 06-28-2011, 08:32 AM
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Default RE: V tail setup?

I suspect you're right, it was probably just your basic stall.

And btw I'm pretty vague on the wing loading concept. What does that mean, exactly?
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Old 06-28-2011, 10:05 AM
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Default RE: V tail setup?



Wing loading is the amount of weight being supported by each square foot of wing area.  The higher the wing loading the faster the plane has to fly in order to generate enough lift to stay in the air.

The Salto specs are:
Wing Span: 2.45 m (96.5")
Wing Area: 30 dm2 (465 sq. in.)
Wing Airfoil: HN 805
Wing Loading: 46 g/dm2 (15 oz/sq. ft.)
Flying Weight: 1.4 kg (50 oz
http://www.nitroplanes.com/sah12racosa.html

So, take 465 sq inches and divide by 144sq inches per sq foot.    = 3.23 sq ft of wing area

Divide 50 oz/3.23 sq ft and that gives you 15.48 oz/sq ft. 

My Ava has a wing loading of about 5.2 oz.  Floats like a feather.
My Supra has a wing loading of about 8.8 oz.   Has to fly faster than the AVA to stay in the air.

Your Salto has a wing loading of 15.48 oz so it has to fly roughly twice as fast as my Supra or about 3 times as fast as my AVA just to stay in the air.   I am sure some engineer will point out that the air foil is a factor and drag and other stuff, but you get the general idea.

The wing loading is not provided for your Sonic, but I am going to guess it is around 10 oz/sq ft.  So, if you fly the Salto like the sonic, the Salto will stall and fall out of the sky.  That is what I think you have been doing.

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