SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Sep 10, 2014, 09:06 PM
Registered User
Joined May 2013
222 Posts
Discussion
Most stable crosswind aircraft?

I'm curious, is a flying wing the least affected aircraft shape affected by crosswinds due to lack of vertical stab and fuselage?


Thanks in advance.

Pete
Petepala1961 is offline Find More Posts by Petepala1961
Reply With Quote
Sign up now
to remove ads between posts
Old Sep 11, 2014, 12:27 PM
Registered User
cbxer55's Avatar
Somewhere in central Oklahoma
Joined Oct 2007
858 Posts
Interesting topic that has garnered no responses as of yet. So I'll throw in my limited experience.

Back in the late 80's I built three Klingberg Wings. These were a two meter sailplane design that could be built with two small fins on the wingtips, or without, your choice. The first one I put the fins on, and as my experience with the plane grew, lopped them off bit-by-bit. I was launching them via hi-start and winch, with a double hook bridle. They were a tad squirrely on launch without the fins, but flew fine once airborne. Never wrecked one on the launch either, quite surprising. I converted one of them to have a gas motor on the back with a pusher prop, an O.S. Max .10 FP being used, it flew awesomely, but you had to think a few steps ahead of it, or it would corkscrew in.

I flew it on days I would not have flown other aircraft due to the wind. Never really though about it until you posted this thread. Obviously it was launched and landed directly into the wind, but other than that it had no real bad tendencies when flying in high winds, other than being light and tending to balloon when turned into the wind.

I've got pics, but they're all the old school hard copy type. Below is a link to some pics of the Klingberg Wings. The one the chick is holding with yellow transparent film is a two meter wing. Great flying airplanes. They make a larger one now, over 100 inches, but it appears to have winglets as part of it's design.

https://www.google.com/search?q=Klin...Q&ved=0CB0QsAQ

Neat airplane. As one guy noted, due to having very little side resistance, it tends to slide downhill when turned sharply. Yes they do. I let a friend fly my powered wing, he crashed it when it got into too sharp a right turn and got away from him. He was not thinking ahead as I had told him to do. Thinking ahead being: as soon as you bank it into a turn, immediately apply reverse aileron to keep it from getting over too far. He neglected to do this, it got into a steep right turn, and slid sideways down onto the ground, right wingtip first. Piled it in good. ;-(

But that ability to slide sideways in a steep turn, is probably why it did not notice strong crosswinds. Is it a good thing? You'll have to decide. Mine, which was over three years old at the time, bit the dust because of it.
cbxer55 is offline Find More Posts by cbxer55
Last edited by cbxer55; Sep 11, 2014 at 12:38 PM.
Reply With Quote
Old Sep 11, 2014, 04:48 PM
Standing Athwart History
roo_ster's Avatar
United States, TX, Dallas
Joined Mar 2011
611 Posts
I'll take a stab at it.

All my FWs had winglets/vert stabs or whatever. Deltas and chevrons both. I have found that the FW form factor is usually more stable in crosswind or gusty conditions relative to planes of similar weight and speed.

I had this stupid 24" WS foamy delta, my second scratchbuild foamy. I could fly that when folks would not fly bigger & heavier planes.
roo_ster is offline Find More Posts by roo_ster
Reply With Quote
Old Sep 11, 2014, 08:17 PM
Ft Lauderdale
Number_6's Avatar
Joined Sep 2012
146 Posts
Quote:
Originally Posted by Petepala1961 View Post
I'm curious, is a flying wing the least affected aircraft shape affected by crosswinds due to lack of vertical stab and fuselage?


Thanks in advance.

Pete
Hi,

Once a plane is launched and flying the wind has no other effect on the way
the plane is flying. It flies the same everytime.... just that the column of air
it is flying in is moving over the ground at a certain speed and direction.

The wind effects navigation headings, ground speed and of course "runway landings"
as the crosswind you mentioned.

One of the best reasons to fly wings (no gear) is that we land on the grass
flying into the wind... whatever direction it is that day....don't need any
stinkin' runways.

If I was going to crosswind land on runways exclusively I'd want
conventional layout of ailerons, elevator, and rudder. This way you can sideslip
into the wind and apply opposite rudder as needed to line up with center
of runway. I'd consider anything more than 15 degrees crosswind as time to pack it in
for the day. This is the biggest reason IMHO why flying wings have the
fields to themselves on windy days.

Tip for windy days, always make flights into the wind...wind in your face.
If something goes wrong the wind will help you get your plane back.

Hmmm, how'd I know?



I should add that my wings all have tip fins but still don't
do a good crosswind landing with only elevons... maybe just me.
Number_6 is online now Find More Posts by Number_6
Last edited by Number_6; Sep 11, 2014 at 08:22 PM. Reason: sp
Reply With Quote
Old Sep 11, 2014, 09:30 PM
Registered User
1fullbird's Avatar
United States, NE, Omaha
Joined Nov 2011
1,064 Posts
Yup, When it gets really windy the only thing I see at my flying field in the air are the larger wings.
1fullbird is offline Find More Posts by 1fullbird
Reply With Quote
Old Sep 12, 2014, 02:41 AM
Registered User
Joined Apr 2013
528 Posts
Yeah, for "proper" crosswind landings (on a specific heading that is NOT directly into the wind) rudder and aileron (cross-controlled) is extremely useful. Otherwise you're going to be landing "crabbed" into the wind even if your flight path is straight down the runway. Depending on how severely you're nose heading is off from the flight path, you can have some nasty "landings".
nuteman is online now Find More Posts by nuteman
RCG Plus Member
Latest blog entry: My youtube channel
Reply With Quote
Old Sep 12, 2014, 10:54 AM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
4,145 Posts
Quote:
Originally Posted by nuteman View Post
Yeah, for "proper" crosswind landings (on a specific heading that is NOT directly into the wind) rudder and aileron (cross-controlled) is extremely useful. Otherwise you're going to be landing "crabbed" into the wind even if your flight path is straight down the runway. Depending on how severely you're nose heading is off from the flight path, you can have some nasty "landings".
On a good note, a well designed wing is strong enough that if you are crabbed with one wing down and do the tumbleweed thing the only thing hurt is your pride.
Rockin Robbins is online now Find More Posts by Rockin Robbins
Reply With Quote
Old Sep 12, 2014, 04:37 PM
Registered User
1fullbird's Avatar
United States, NE, Omaha
Joined Nov 2011
1,064 Posts
Crash Test Hobby wings sure fit the bill.
Assassin vs Brick Wall 3 12 (4 min 14 sec)
1fullbird is offline Find More Posts by 1fullbird
Reply With Quote
Old Sep 14, 2014, 09:41 AM
Registered User
Joined May 2013
222 Posts
Thanks guys.
I'd've thought this'd be the best design on windy days. The assassin is amazing in the abuse it can handle and keep fling.

Anyone fly 2 meter wings?

Pete
Petepala1961 is offline Find More Posts by Petepala1961
Reply With Quote
Old Sep 14, 2014, 12:00 PM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
4,145 Posts
Well, my Grim Reaper is 60" before it's swept and becomes 55". That's a tad short of a meter........nope!

Just a weird thing about wing aerodynamics. You know if you put a vertical stabilizer on it and hang a rudder off the back what happens? Not much, just a braking effect! If you have a centered vertical fin and the plane gets sideways, what happens? Nothing, the plane just slows down! So what keeps these puppies pointing straight ahead?

There are two strategies that get used, shown by my Grim Reaper and the Assassin. Best illustration is the Assassin's logo:

See the leading edge on the outside where two notches are cut? Those are straight vertical cuts through the airfoil at an angle. Those guys work just like a vertical stabilizer on a regular airplane tail. How, you say?

These things cause drag out on the end of the wings. Let's yaw that plane to the left, throwing the left wing forward and right wing back. Can you see how the notch on the right, because it swings back, shows less frontal area to the wind. Now that wing has less drag than usual. Can you see how the notch on the leading left wing now shows more frontal area to the wind? That wings now has more drag than normal. This differential drag causes the wing to rotate back to the right until the forces balance. The taller the notch the better it works, and that's why this works best in thicker wings like the Assassin and Titan.

Notches work on thinner wings like Grim Reaper, but not as well. Rather than stabilizing quickly, the lesser forces let the wing oscillate back and forth across the neutral yaw position and finally settle down. Unfortunately, you've restarted the process well before then as you perform another maneuver.

If you want that plane to track in-line with stability you need more drag out there and the solution is our winglets. But be careful there because they work differently than a vertical stabilizer on a conventional plane, which works like an arrow. Winglets on a wing aligned perfectly with the direction of flight don't do anything. The plane is just as happy flying straight, sideways or backwards.

To make them work you have to toe them in, just like the notches of the Assassin are toed in but to a lesser extent. I think Lee said that the toe in on the Grim Reaper is a quarter inch. So let's visualize these winglets (not vertical stabilizers!) and how they work like the notches on the Assassin.

If you yaw the plane to the left, throwing the right wing forward, that right wing's winglet now shows more of its frontal area to the wind. Drag on that side is increased. The trailing wing, because of the winglet toes in, will show less frontal area and have less drag than the leading wing. The difference in drag rotates the plane around to the right, straightening it out.

Just because winglets look familiar doesn't mean they work like you would expect!
Rockin Robbins is online now Find More Posts by Rockin Robbins
Last edited by Rockin Robbins; Sep 14, 2014 at 12:18 PM.
Reply With Quote
Old Sep 14, 2014, 02:23 PM
Registered User
cbxer55's Avatar
Somewhere in central Oklahoma
Joined Oct 2007
858 Posts
My experiences with totally fin-less wings, the Klingberg Wings, had no notches or any other type of trickery on them. Nothing. They still flew well, and generally stayed pointed straight ahead. They did however, have some weird adverse yaw traits, that took some getting used to. When I built the first one, I did put the small fins on that the kit provided. They were pointed straight ahead, no toe-in whatsoever. They were attached to the end rib prior to attaching the wingtip block in place.

So no notches and no toe-in on the fins. Yet they flew just fine. I've always thought it had to do with the sweep back angle, and the large amount of washout the things had. Arrowhead stability. I've seen that bandied about a bit here-and-there.

I'm definitely no expert on wing aerodynamics. And it's been years since I last flew one. But I still like them a lot more than conventional configurations. It's just neat seeing a wing fly, with nothing else on it to distract your viewing pleasure.
cbxer55 is offline Find More Posts by cbxer55
Reply With Quote
Old Sep 14, 2014, 10:49 PM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
4,145 Posts
Sure, CBXER, sweepback works to some degree to stabilize yaw. When the plane yaws the leading wing is more square to the wind, presenting more frontal area, while the trailing wing presents less frontal area. The differential drag causes the yaw to return to zero. You probably noticed some oscillating. Thicker airfoils would be more stable in yaw.
Rockin Robbins is online now Find More Posts by Rockin Robbins
Reply With Quote
Old Sep 15, 2014, 12:41 AM
Registered User
cbxer55's Avatar
Somewhere in central Oklahoma
Joined Oct 2007
858 Posts
Oscillating? Sure enough. It's what I referred to in those wings, as being ahead of the airplane. Bank it into a left turn, immediately get on opposite aileron to prevent it from going in on a wing tip.

I got so used to the characteristics flying one with a gas motor in the pusher configuration, when I let a friend fly it, he crashed it on the first flight. Spun it in on it's left wingtip. Banked it over hard and neglected to get on opposite aileron fast enough, BANG!!!!!

I was sorry to see it go, it was a nice flying airplane. TO ME. LOL

Marriage kept me out of the hobby for a number of years. Now that I am single again, I'm eyeing wings again.

Rockin Robbin and eye disagreee on what a flying wing is. While I agree with him that a wing with nothing else on it sure is neato, I still think the ME-163 is a flying wing.

I still think a delta is a flying wing (loosely).

Was watching a video the other day on the B-2 (I worked on them for 11 years), and the ME-163 was referred to as a flying wing. Some people just like a plane with a vertical fin and rudder for the things such a craft can do. Rudders are useful.
cbxer55 is offline Find More Posts by cbxer55
Reply With Quote
Old Sep 15, 2014, 01:05 AM
Registered User
Joined Apr 2013
528 Posts
When the flight path is not exactly aligned with the center-line of the aircraft (in a "skid" or "slip") there will be a lateral relative flow.
So on a wing with a fair amount of sweep, even zero-toe-in winglets will provide yaw stability ("vertical stabilizers") when the plane's nose is perturbed to the left or right of the flight path (as they're well behind the CG) - in exactly the same way as a vertical stabilizer would weather-vane a conventional plane.
Sweep alone (without winglets) provides some yaw stability, but typically not enough for "comfortable/predictable" behavior on higher aspect ratio wings. Note how even the Crash Test planes that are higher aspect ratio do have winglets.
nuteman is online now Find More Posts by nuteman
RCG Plus Member
Latest blog entry: My youtube channel
Reply With Quote
Old Sep 15, 2014, 04:54 AM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
3,277 Posts
Schapel SA-882 mit Strahltriebwerk (1 min 49 sec)

Check out some of his other wings.Great designer/builder/pilot.Not many fins on show
Stupot46 is offline Find More Posts by Stupot46
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Wookkong M ---Most updated and stable Firmware?? quadman Multirotor Talk 4 Apr 02, 2014 07:30 AM
Discussion which is most stable 4 begginer 6ch? yours truly Micro Helis 16 Jan 21, 2014 03:40 PM
Discussion Most stable HK Electric Warbird under 1 meter jrk74 Electric Warbirds 3 Nov 27, 2013 12:50 PM
Discussion Most stable FPV platform? Prove it? Barn-E-Stormer FPV Aircraft 19 Nov 11, 2013 10:10 PM