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Old Sep 19, 2012, 12:46 PM
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roo_ster's Avatar
United States, TX, Dallas
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Winglets vs Vertical Stabilizers on Delta Wing

Howdy:

Since I am building a FFF delta wing, I was wondering about the pros/cons of winglets vs vert stabs on deltas and (if winglets are better), ought the winglets go under the wing and extend behind the elevons?

A recent chevron-style wing I built greatly benefited from extending the winglets below the plane of the wing and to an inch beyond the elevons. It was noticeably more stable in the air afterwards. Is there a similar effect on deltas?

The delta I am building has a 36" WS and will be used for aerial photography, so more stability is better.

Also, I am considering using a gyro for more stability. I had thought I would be content with ail & el hooked to the gyro, but perhaps I ought to consider a rudder, too? If so, center or wing tip?
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Old Sep 19, 2012, 01:34 PM
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eflightray's Avatar
South Wales U.K.
Joined Mar 2003
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Can't help in the winglets, I think that's more down to experimentation.

But for stabilization, this one is worth considering, (and it's cheap ) -

OrangeRX 3-Axis Flight Stabilizer thread , it's in the Parkflyers forum, but also appears in a few other forums as well.
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Old Sep 19, 2012, 01:57 PM
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United States, UT, Salt Lake City
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Quote:
Originally Posted by roo_ster View Post
Howdy:

Since I am building a FFF delta wing, I was wondering about the pros/cons of winglets vs vert stabs on deltas and (if winglets are better), ought the winglets go under the wing and extend behind the elevons?

A recent chevron-style wing I built greatly benefited from extending the winglets below the plane of the wing and to an inch beyond the elevons. It was noticeably more stable in the air afterwards. Is there a similar effect on deltas?

The delta I am building has a 36" WS and will be used for aerial photography, so more stability is better.

Also, I am considering using a gyro for more stability. I had thought I would be content with ail & el hooked to the gyro, but perhaps I ought to consider a rudder, too? If so, center or wing tip?
Depending on your version of Delta - the fences do stabilize in high angles of attack.
as a camera model tho -- low speed will likely get wobbly
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Old Sep 19, 2012, 02:08 PM
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The 'Wack, BC, Canada
Joined Oct 2002
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I see this as one of those "it depends" sort of solutions where you would simply need to experiment with the various options.

The "it depends" is due to the way the airflow works over a delta wing where it depends a lot on the amount of wing sweep and the speed and related angle of attack you'll use for your camera flying.

The optimum solution would be to make the wing with "hardened" tip ribs that have a couple of T nuts so you can experiment with different tip fins. Similarly put a root rib sandwich with a slot in the center so you can add fins above and below and secure them with angled cross pins.

Done neatly you'll add very little weight to achieve this amount of adaptability and you can then easily experiment with a wide variety of tip or center fin options.

With the optimum fin arrangement as determined from testing you should not require any onboard gyro units for added stability.

It's hard to say much more than this without knowing what sort of planform you consider to be a "delta wing". Too many think that if the trailing edge is straight that it's a delta wing despite the reality being that it's more of a swept and tapered normal flying wing that just happens to have a straight trailing edge.
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Old Sep 19, 2012, 06:53 PM
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roo_ster's Avatar
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Quote:
Originally Posted by richard hanson
Depending on your version of Delta - the fences do stabilize in high angles of attack.
as a camera model tho -- low speed will likely get wobbly
Yep, low speed performance is important. I chose the power train with that in mind (lower KV, larger prop) and ran with a 36" delta rather than a 36" chevron (longer vs shorter chord) to decrease the wing loading.

Quote:
Originally Posted by BMatthews View Post
I see this as one of those "it depends" sort of solutions where you would simply need to experiment with the various options.

The "it depends" is due to the way the airflow works over a delta wing where it depends a lot on the amount of wing sweep and the speed and related angle of attack you'll use for your camera flying.

The optimum solution would be to make the wing with "hardened" tip ribs that have a couple of T nuts so you can experiment with different tip fins. Similarly put a root rib sandwich with a slot in the center so you can add fins above and below and secure them with angled cross pins.

Done neatly you'll add very little weight to achieve this amount of adaptability and you can then easily experiment with a wide variety of tip or center fin options.

With the optimum fin arrangement as determined from testing you should not require any onboard gyro units for added stability.

It's hard to say much more than this without knowing what sort of planform you consider to be a "delta wing". Too many think that if the trailing edge is straight that it's a delta wing despite the reality being that it's more of a swept and tapered normal flying wing that just happens to have a straight trailing edge.
Outstanding idea.

Here is an image of the shape, courtesy of another RCGroups member:


Size is 150% of this image (36" WS in reality, 24" WS in image) Ignore the prop slot, I am running a tail mount. Also, I built it up with a mild KFm3 airfoil, not a KFm4. (Mild, in that I didn't make it as thick as suggested. I read somewhere these delta airfoils do OK with a less aggressive / less thick airfoil.)
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Old Sep 19, 2012, 08:07 PM
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Thicker is lust less sensitive
I build as thin as strength will allow
be carful on th e rear mount - tail heavy is easy to achieve
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Old Sep 19, 2012, 11:21 PM
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The 'Wack, BC, Canada
Joined Oct 2002
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That's really a far more aerobatic sort of deal than you may want. I trust you're going to make the elevons about 1/3 of the width as shown.

With a flat shaped wing I wonder where you plan on putting the camera? Or will you just velcro it to the flat wing?

In any event Dick is right. The CG has to be way up around about 1/3 of the root chord. That means that just about everything BUT the motor will need to be located well forward to avoid the model needing a heap of nose weight added to the mix for balancing.
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Old Sep 20, 2012, 10:51 AM
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Yes, I will make the elevons smaller, both in width and length. I did that for my previous 24" WS pusher variant of this.

Fore & aft balance for CG won't be as bad as it looks in the image, as I have installed a KFm3 airfoil, which doubles the mass up front and two sets of lateral dowel reinforcement: one at the leading edge and one at the first step of the KFm3.

Also, I have already produced a 24" WS version of this with a pusher motor and a KFm2 airfoil. It balanced just fine. The motor & power system I chose for the 36" WS is proportional to the power system I chose for the 24" WS version. My 36" WS version will have a lower wing loading (without camera) as I am using the same 1/4" thick FFF for both. The 36" WS version will have a motor suitable for a PZ T28 sort of aircraft (but lighter weight than the PZ480) and has 1/4 or 1/3 more wing area than the PZT28 and will be lighter (before camera) than the PZT28. I ought to be able to lift a decent amount of camera gear.

The camera will go up front, pointed off-axis and depressed. I will affix velcro from nose a good ways back so I can easily adjust for CG using my camera and a 2200mah 3S lipo. I need to craft a mount/cradle for the camera that will have a servo-actuated deal trip the camera.
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