Electric Windy Day Glider - RC Groups
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Oct 29, 2017, 04:19 PM
Pro Bro #829
steener's Avatar
Discussion

Electric Windy Day Glider


Looking for suggestions for a windy day electric glider. Aside from an Electra my ships are all very light and haven't proven to perform well in 10mph plus winds. I like to build so not interested in a mouldy. I have no problem scratch building or buying a kit. Would like to stray from a polyhedral wing as they get blown sideways when flying at an angle to the prevailing wind.
So what do you fly on breezy days?
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Oct 29, 2017, 06:22 PM
Registered User
On calm days I fly a Pulsar on windy days an Art Hobby Odyssey. Plenty of videos on YouTube of it flying in all sorts of conditions...from light lift thermaling to scorching hot dynamic soaring.
Oct 29, 2017, 06:56 PM
B for Bruce
BMatthews's Avatar
I'll second your idea of a flat wing with ailerons. They work superbly in windy and turbulent conditions.

You'll want something with good penetration. And to still allow it to soar reasonably well I'd suggest a thin and low camber wing rather than an overly heavy wing loading.

And in fact I'd say if you like to build and don't mind altering plans to suit your needs a 2 meter'ish sized slope soarer modified to lighten it up to a more thermal worthy wing loading would be just about perfect.

I had a model of that sort some years ago. It was my own design called the "Flapjack" after the flat wing and flaps. But I foolishly let it go to a club member thinking it would encourage me to build a better one. That day still hasn't come. And at this point it would more than likely have an electric motor in the nose anyway. But it was around for a couple of years of flying and did more than its fair share to convince me that ailerons are the way to go when the wind is strong and blustery.
Oct 29, 2017, 07:50 PM
Pro Bro #829
steener's Avatar
I like the idea of a thin low camber airfoil. AG35-38? Could use Mountain Models Allegro short kit ribs and just build with a bit of dihedral?
Oct 29, 2017, 08:43 PM
Sagitta Fanboy
Sagitta 600 or 900 converted to a flat aileron wing would do well in the wind. Even better if you went to a thinner foil like an AG3x or S3014. These designs can readily have a geared Rimfire Ammo or similar 28mm outrunning installed in the nose.

My usual windy day ship is actually a Sagitta 900 with a somewhat heavy fuselage (56oz RTF), and it does well in 10-15mph winds even with the poly wing.
Oct 31, 2017, 02:40 AM
Registered User
An Allegro Lite wing is very strong, so you could probably ballast one of those. Low drag too. I have a Sagitta 900 myself, but I think the Allegro Lite, with ballast, would be faster.

Once, at a windy RES contest, I borrowed a heavy model with an Allegro Lite wing. It was very fast, and it seemed I was the only one who didn't have to worry about being blown off the field. Unfortunately, it came down fast too, possibly because of the draggy fuselage.

I seriously doubt an RES model with dihedral is going to be "blown sideways" any less than one with polyhedral. To cope with wind, speed is what you need, not a flat wing. Of course, with a relatively flat wing you can use ailerons, which can be helpful if the wind is gusty. A ballasted, unmodified Allegro Lite with ballast is going to be pretty maneuverable, so I'm not sure how much you'd feel the need for ailerons.

On the ground, a relatively flat wing is somewhat less vulnerable to being flipped over by the wind.

If you don't mind dealing with composites, the original Allegro (RES) or the Aegea 2 meter (ailerons) might be good choices, but I suspect either is a fairly large project.

For any of these, except the electric version of the Allegro Lite, you'd have to modify the fuselage for a motor, battery, and maybe ballast if you want to fly on a really windy day.

If you're used to gliders with airfoils that are flat on the bottom, all the way to the leading edge, a glider with a "real" airfoil will handle the wind a lot better. If any of your light models are reasonably strong, they could benefit from ballast on windy days. Especially if they have some "Philipps entry". I suspect there's a better term for it, but it means that the underside of the airfoil curves up i n front to meet the leading edge. See the attached pictures for the difference.
Oct 31, 2017, 02:41 AM
Registered User
P.S. An Allegro Lite with much less dihedral, but no ailerons, would be helpless in a gusty wind. The lack of dihedral would make it slow to respond to the rudder.
Oct 31, 2017, 12:55 PM
Registered User
Don Stackhouse's Avatar
steener, you might take a look at our big 2-meter Chrysalis. It has a much thinner wing than the other planes you mentioned having experience with, and has a far greater speed range as a result. The polyhedral RES version handles wind just fine, without ballast, and we do have a full-house version in the works (and yes, we will be offering separate wing kits of that for folks who already have the RES version).

http://www.djaerotech.com/2m-chrysalis-sailplane-kits/
Oct 31, 2017, 01:18 PM
B for Bruce
BMatthews's Avatar
Quote:
Originally Posted by lincoln
P.S. An Allegro Lite with much less dihedral, but no ailerons, would be helpless in a gusty wind. The lack of dihedral would make it slow to respond to the rudder.
And that would be the downfall of such a modification. I always found on the turbulent days the key to survival and thermal success was very responsive control. And that's where the ailerons came into their own. Very direct and faster to respond because they roll NOW where the rudder and dihedral take a little longer to yaw THEN roll. Keep in mind I'm talking those that are stubborn enough to still fly when all the same folks are packing up before their car blows over....

The funny thing is that I'd never CHOOSE to go fly on a messy day. But the times I got to the field and it was just tolerable but got worse and while I had that aileron model I found I had a lot of fun. Not so much catching thermals as doing a form of flatland dynamic soaring. At the time I didn't know about using a line of trees as a shear line but just used the sudden velocity changes by turning into them when they tried to tip me away. Or on one day where following a thermal would have been suicide I found some odd wave effect and was able to just put my nose into the wind and hold station from the ground and the model just sat there. it was a wild ride with almost constant corrections needed to keep it there but it stayed up for well over a half hour and secured me the "longest flight of the day" trophy at a Boeing Hawks electric flyin back in the early 90's. But it was the sort of day that at home rather than after a long drive I'd have just said "nah" and gone back to the warm house.

If I lived in places with generally higher winds I would likely have moved over to flat wing models with ailerons long ago.
Oct 31, 2017, 01:54 PM
Registered User
I had been thinking of this very problem myself - and realized that di/polyhedral wings and gusty wind is a tough compromise at best when the wind picks up - any side swirl to a gust front and you have a turned plane, and it goes downhill from there . On the flip side, while I like the responsiveness that flat wing planes provide, I like the inherent self leveling that polyhedral planes have - I'm someone who is more interested in seeking thermals than doing 3D acrobatics.

To that end, I have wondered if using a flat wing plane, with a thinner wing (Heron? Perhaps Don's future flat wing Chrysalis?) with some low gain stabilization (lemon stab +?) and active gyro may be just the ticket for windier days - or at least have that as a switchable option. Seems it would also help flying back upwind too. And for lighter / medium air - do RES with a lawnchair.
Nov 01, 2017, 01:20 AM
B for Bruce
BMatthews's Avatar
Fdsailor, when I compare how my aileron model flew to my poly model in high winds I actually found that the flat wing was MORE stable just because it wasn't turned as strongly by the side gusts.

A flat wing does not need to totally lack stability either. The model I was flying used about 2" of dihedral over the 1 meter of wing panel.... So around 3 I put it in there originally to aid with keeping the tips out of the grass during landing. But it also gave the model a nice tendency to level its own wings. Combined with this was a carefully trimmed vertical stabilizer size to find what I felt was a good value for the vertical tail coefficient that allowed for a minimizing of side slip in turns but not so high that the model wanted to wind into the turns at any but the more extreme angles. This too aided the flyability. The result was not as hands free in moderate conditions as a poly model but in blustery air with lots of variable gusts it was WAY easier to fly than a poly ship. And even in the calm stuff once set to level and straight it would stay level and straight hands off with out any issue. It would also self level out of a roughly 15 turn if I neutralized the controls and just ran the elevator to maintain speed. Again not as fast as a poly model would manage. But well enough.

I'd be against using auto stabilizing in a glider as an initial feeling because I suspect it would damp out the very upsets from the air around the model that I rely on to tell if it's getting into lift, sink or other effects. I use those kicks and pushes to decide on what to do next. And auto stabilizing would reduce their effect and thus how visible they are and mask the magnitude of the air that is doing the upsetting. I guess I expect my gliders to get tossed around. I use that to tell what the air around them is doing. I don't want anything that will reduce that.
Last edited by BMatthews; Nov 01, 2017 at 01:26 AM.
Nov 01, 2017, 07:44 AM
Pro Bro #829
steener's Avatar
Thanks for all the helpful ideas.
Don, I just built one of your 1.5E Chrysalis and really enjoyed it. Great design and great ship for light lift. She doesnt need much to just play around on a dead air day too. Looking forward to your full house.
Im leaning towards using a Sapphire pod and boom, Allegro Lite tail, and then experimenting with wings. Id like to try a low dihedral wing with ailerons. Is there any reason an Allegro Lite set of ribs shouldnt be used to build that wing? AG35 isnt a flat bottom, has phillips entry. I dont see the need for the complicated wrapped spar. CF caps should be plenty. The sheeted Dbox should be strong enough tortionally to hopd up to some 1" ish sized rons. Thoughts?
Nov 01, 2017, 01:23 PM
B for Bruce
BMatthews's Avatar
Your idea is a match for what I've been thinking about doing for a couple of years now.

If you look at the airfoils used on the AL the upper rear is comprised of a series of flat "facets". The trailing edge being one of those facets. So it seems like it would be a natural step to make the trailing edge into the aileron and to cap off the rear of the ribs with a hinge line spar where the top of that added spar is the finish point of that facet in front of the aileron.

And as you say it would never see a big power winch so spruce and balsa with relatively thin carbon caps would do just fine.

What I would do though is to sand in a long taper in the thin caps and then overlap them by a good 1.5 inch at the dihedral joints where there's no joiner. But you may not need that if you do the obvious thing and put the split wing joint at the fuselage for this style of model. Assuming you make the full tapered and raked back style design you would need/want to see the spar caps sort of overlap chord wise somewhat with tapered joints but that doesn't require sanding the thickness. Just cutting the top view to gain as much overlap as possible.

Windy day landings can tend to be rough. For a dedicated windy day model I would prefer that the tail be done in a way that is a little more protected. For me that means possibly a V tail or a fuselage blending to a well shaped fin and rudder that has a full flying stabilator mounted up at mid tail so it doesn't have a chance of catching in any grass. And where the bottom edge of the rudder is angled up away from the lower corner of the fin. And perhaps even protected by a bit of a skid so any unexpected side ways skids to a halt don't see anything pulling against the rudder and thus possibly straining the servo.

I love the look of the V tails but the mid fin mounted plug on stabilator would be FAR more easy to break down for transporting. And I can't help thinking that with a good fuselage built into a fully airfoiled fin and rudder would also be far more rugged and damage resistant than the delicate all flying stabilizer mount as seen on the AL. Catch a tip at a good speed on that sort of mount and carbon or not something at the hinge mount is gonna give!

For my own design I feel that good handling in a stormy day model is more important than absolute aerodynamic efficiency. So I'm thinking 2 meters as a nice size for seeing at a distance but big enough to be more efficient. And I'm thinking of more like a constant chord or slight taper to more of a shorter and simpler raked back wing tip. with perhaps this tip being about as long as the outer chord width and angled up about 4 or 5 degrees from the rest of the wing which would have around 2.5 degrees at the root. That should make the tips a little less likely to catch and dig in during blustery arrivals .

I'd also want enough fuselage to hold onto for launching. So a little more depth than we often see just under the wing at the balance point. And maybe a couple of sandpaper patches to aid with grip. That extra room might even allow for a bit of a ballast box to ramp up the cruise speed for moving around the sky more.

That model that I talked about above was a real looker with mid mounted wings. But in the end the mid mounted wings and neatly rounded shape forced me to hold for launching from behind the wing. And that was never a really great thing. So I'd favor a shape for a windy weather model that gives me that flat sided area at least large enough for a good grip before the shape turns rounded. I don't know what the fuselage you're considering looks like but I'd offer up that a good positive grip in windy weather is an important feature. I know I won't make that mistake again. Although with my model that was a pure glider holding it just ahead of the wing was not an option since the line was pulling like a banshee right through the thin web of my hand. But for an electric model holding it just ahead of the wing becomes a valid method. Doing it that way the model can "weather vane" out behind the grip. And as long as the folding prop blades don't extend back to the fingers area all is good. I'd still use the sandpaper patches though... Don't need to have our grip slip and fingers reach ahead to the running prop when not intended....

Thoughts back from you?
Nov 01, 2017, 02:30 PM
Registered User
Essex BOF's Avatar
My model of choice when the wind gets up, is a Nan Models Shadow. Not the new version as it is quite light, but the old one, which has a bigger fuselage that can take an out runner plus has plenty of room for ballast. With a V tail version at 3.65 metre span, loves a breeze. Been flying one for some 5 years when the wind gets up in ALES type comps here in GB.
Nov 01, 2017, 05:03 PM
Registered User
Don Stackhouse's Avatar
One point that really hasn't been firmly recognized in this discussion. "Windy" is not the same thing at all as "gusty", and the existence of one of those conditions does not automatically mean the presence of the other. One of those requires adequate penetration; the other requires adequate control response. Not the same thing at all.

Also, polyhedral with RES does not have to have slower roll response, and having ailerons does not automatically mean quicker roll response. At our Reynolds numbers, the necessary chord percentages and detail design are NOT the same as for full-scale, yet far too many model designs use the control surface chords recommended for full-scale aircraft (20-25%) from Abbott and von Doenhoff's "Theory of Wing Sections".

A well-designed poly RES ship with minimized inertia in the extremities could indeed have better control response than an aileron ship designed by TLAR or rules of thumb.


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