2M vs Bigger, is it really that hard to thermal a 2M or smaller? - RC Groups
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Nov 20, 2010, 07:40 PM
Registered User

2M vs Bigger, is it really that hard to thermal a 2M or smaller?

Here's my current question of the week:

OK, yes, I know all about the fact that bigger sailplane models fly better than smaller ones and I know several size/physics related reasons why that is the case but 2M seems to be pushing the publicy acceptable limits of the nonflying public where I fly and I really think "bigger-than-2m" would be the lightning rod to bring the lightning home to kill ALL flying RC(for myself and others) where I fly, so my question is this:

Q: - Is it really "that" hard to find and stay in a thermal and get lift and stay up off of the ground with a 50" to 2M plane (once you know how to reliably find and get into thermals)?

I get the idea that people do "actually" find thermals with 2M and smaller planes and stay in them, then for reasons of drift, excess altitude gain or whatever -they leave that thermal, fly back closer and find another thermal upwind, gain altitude and float around and over and over until they get tired of it and finally land. I seem to be closing in on that path, I'm just not there yet.

As much as I get appreciated and well founded recommendations to go bigger than 2m, I find myself more interested in 2M and smaller planes.

So, back to the main question, Is it really "that" hard to stay up with 2M (or less)?

Thanks - Paul
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Nov 20, 2010, 09:36 PM
Registered User
SailplaneHawk's Avatar
I, myself find 2M no more diffucult than anything larger. But I build and fly "woodies". The only problem I see is that with the larger stuff you can go much higher which in turn allows you to take advantage of the thermals longer without losing your plane. And the thermals would be larger as you go up too. With pratice I am getting better with my 2M Riser which like you I am pretty much limited to at the park I fly at. Thats my 2cents worth.
Nov 20, 2010, 10:24 PM
The Lone Blue Plaid Flyer
Bob Cook's Avatar
Hi Paul,

I don't have any more problems with 2 meter planes than bigger ones. I fly in a school yard play field. I actually prefer 2 meter planes. When you find a thermal, it's just as much fun with a 2 meter as with a 3 meter. I don't think there is any difference in the difficulty or the fun you get.

Bob in Seattle
Nov 20, 2010, 10:34 PM
AKA - The "Flywheel"
StevenatorLTFO's Avatar
You definitely give up performance with a 2 meter, they don't have the L/D of the bigger birds, but I wouldn't say it is a lot harder, but its not as easy
Nov 20, 2010, 10:36 PM
agony sweetns the victory
atjurhs's Avatar
It has a lot to do with wingloading. Why are DLGs such successful flyers and able to rise up on a frog's fart? Because they have ultra low wingloading values. Unfortunately, most 2Ms have rather high wingloadings, and so they are more difficult to keep aloft. Build a 2M with an equivalent wingloading as a DLG and you'll have similar thermaling performance. Some of the things you won't be able to achieve is the ability to launch as high and range as far. So it's all about trades. You're trading one thing for another.
Nov 20, 2010, 10:50 PM
Registered User
My 2m ships get much more airtime than my bigger birds. I love my bigger birds but the 2m ships just seem more fun to me An interesting note is that my personal longest flight of 1:47 was done on a 2m bird
Nov 20, 2010, 10:58 PM
Fly R/C writer
Hi Paul,

I fly both and anything in between. Here's the deal with 2-meter. They are a bit different breed. They fly at relatively the same speeds as the larger 3-meter+ size birds, depending on weight. I prefer that my 2M planes weigh 34 oz or less to be competitive, because after that, the wing loading begins to work against you when it comes to a pure float where you are going for hang time and eating up the clock in a contest.

Because they do fly at about the same relative speed as the bigger cousins, they will reach the limts of your eyesight faster because they are smaller. This limits one of the big advantages of the larger, faster cruising birds and that is the ability to cover large areas of the sky to find lift. It is not uncommon for an experienced pilot flying a big plane to range out a mile away. You're not going to do that very often with a 2M. So, you have to stay closer to home to find lift, and could limit your flight time ability.

And I find that 2-meter birds don't slow down for landing like a big bird does. I mean, they do slow down when equipped with flaps, but not to some of the ridiculously slow speeds that the current crop of competition models can do. I own an Xplorer 3.8 that weighs in at 71-oz and goes so slow, it should fall out of the sky....but it just keeps on flying right to the landing spot. My current 2M plane is a Nico from Hobbyclub, and weighs a mere 27-oz with flaps and ailerons. It does have a slightly lighter wingloading than the Xplorer and has generous size flaps, but still comes in to land faster.

These two elements, (the inability to range out as far and the speed envelope) makes flying a 2M in competition a different experience. Don't get me wrong as I love to fly 2M. Indeed, I telll most of my fellow club members to fly a 2M...if you can learn to competently fly a 2M, you can fly anything! Before most major contests, I fly my 2M to sharpen the skills. It's the inability to range out that mkes it appear that your fellow pilots appear to thermal, drift out and return to catch another one. But then, guys with bigger planes do the same thing.

As for being harder or easier to thermal a 2M? I think it's just a tad harder for two reasons. A light 2-M like the Nico gets bounced around up there quite easily, so it makes it a different skill to determine if the bounce is from a thermal or just turbulence. Also, because we fly at about the same relative speeds as the bigger planes, it is possible to fly clean through a piece of light lift and not know it. So, I think you have to keep a more critical eye on the plane, and that will sharpen the skills to the point where it's no tougher to stay in lift than any other larger plane. It's just a slight shift in technique. Just my thoughts, and there will be other opinions. YMMV.

Nov 21, 2010, 08:27 AM
LSF 4685
My ability to find thermals is probably limited. I find that the height of launch affects finding thermals. That said, launching a 50" bird to a great height seems to be a difficult task to me. Mind you I've never owned a 50" bird. I have flown a friend's a couple of times.

Launching of an eight ounce, 50" inch bird seems difficult to me. A regular high start would generate too much tension and an Upstart, being much better suited for the small bird, won't yield a high launch. Winching would be out of the question in my mind. Forget DLG or hand launch.

So to me, it boils down to launch height. If there is a day with strong thermals low to the ground, you will find thermals. If not, prepare for a day of one and a half minute flights and a lot of exercise walking to retrieve and pull the upstart.

Now please tell me why I am wrong. I am about to build a 50" Mini-Lil Bird from Skybench and I need the education.


Nov 21, 2010, 07:38 PM
Thermal Naked!
Hossfly72's Avatar
You're going to love that plane Dave. A Dynaflite Upstart will give a 200-300 foot launch. It's not as big or strong as a full highstart, but it'll launch up to a 2 meter just fine (only lower). You're gonna freak out when you find a thermal around 10-15 feet though. That's where I learned to thermal with Skeeters back in the day. And if Ray's balsa is still as good as it used to be, you'll have no trouble building it with a very nice and light wingloading! Make sure to follow the advice on his "Tips" page!
Nov 21, 2010, 08:22 PM
Registered User
If you're using the older airfoils, the size difference is pretty important. Of course it's not all that hard to thermal a Riser or something on a good day, but it's more vulnerable to sink and wind, and it doesn't float quite as well as something larger.

DLG's stay up not so much because of the weight, though that helps, but because they have thin airfoils and are clean, so the Reynold's number problem doesn't hit them as hard as the older gliders. But it's still harder to fly them well because everything happens faster and the launch is lower.

If you really want to fly 2 meter, and your vision is quite good, then don't worry about it. It's not that hard. And perhaps if your vision is just average you could fly a Chrysalis 2M or something. Of course a Chrysalis 2M will look larger than, say, an Allegro Lite. And I'd guess its ultimate performance would be somewhat less than that of the Allegro Lite.

If you want to go even smaller, the hand launch Chrysalis is pretty easy to fly and has decent performance.

I don't see any reason, if you're going to fly small gliders, not to use lighter line and rubber with your hi start, but keep it just as long as the hi starts for larger models. You'll still launch fairly high, if you keep the line small. Say, 25 lb test fishing line or something. Just get it in a fluorescent color.

I flew 2M exclusively for several years. But now I like bigger gliders better when hi starting or winching. And smaller ones when hand launching.
Nov 21, 2010, 09:02 PM
Ochroma Pyramidale Tekton
Fly Wheel's Avatar
The first thermal I ever caught was at an asphalt "field" at my Jr. high school. It was with a small free flight plane that I had hand tossed into the air. It leveled out and started a slow circling. But instead of slowly drifting to the ground it rose! And continued to do so until, as I watched helplessly, it drifted out of sight (still rising) down wind. No real loss, since I had made it simply by folding up a sheet of notebook paper!

It had a wingspan of about 7 inches. So yeah, small planes can find thermals just fine.
Nov 21, 2010, 09:48 PM
Registered User
Yup. I've lost 3 or 4 ff catapult gliders myself, in thermals.

Also at least one paper plane. I used to toss them from the 6th floor or so of a building at school. One vanished while climbing at a prodigious rate over the dome of the main building.

Have to admit that a similar attempt from the Empire State Building was a failure!

However, I've seen a paper bag get sucked off the ground and do 30 seconds, or was it a minute? Also a P-30 wing. And this is in the east. I expect if I go to Arizona the right time of year I will see the same thing happen to small, fuzzy dogs. ;-p
Nov 21, 2010, 11:28 PM
Registered User
Hi all. I have the same challenge with 2m vs larger, more complex. Typical 2m planes don't seem to have the best lift/drag ratios, compared to dlg's or larger sailplanes. dlg's have very thin airfoils so that gives them range and longer duration.
Then the typical 2m (which is designed and priced with the beginner in mind) has a wing up to 3/4" thick, and commonly a flat bottom section. You will notice that larger planes (3m) have wings the same thickness as the 2m. With the extra weight and size the larger plane effectively has relatively thinner wings than the 2m, so the lift/drag advantage is regained.
Most 2m planes just don't have the range because the wings could be thinner (less drag like a dlg) so its more demanding to achieve sucess. More efficient designs are not that forgiving to fly (stall and handling) but it all happens slower with a larger model. Something in 2m size that is efficient enough to be exceptional (Drela airfoils and such) will be either highly priced or very tricky to build, which are the other compromises of 2m.
The main advantage is that they are so much more convenient to take to the field. I am also attatched because that's where I started, and the fact that they are about the size of a soaring bird is intriguing too.
Nov 22, 2010, 12:08 AM
planepainter's Avatar
I have seen first hand what a well built Allegro Lite (efficient Drela design) can do and will be building one soon.
That said, I also fly a 2 meter New Spirit and an OLYIII. I find that I can take advantage of small cores with my 2 meter better than my big O3. The Spirit turns smaller, tighter circles, pirouetting on one wing almost, and I can take advantage of the small bubbles when there are no "boomers" about. It is fun to flit from one small core to another. You may not gain much altitude, but at least it is not going down...
Nov 22, 2010, 12:24 AM
Registered User
ozmo01's Avatar
Lot's of good advice/info but I think atjurhs nailed it with the wing loading statement.
Not all 2 meter birds are created equal either. Lots of 2 meter intro level gliders are built a bit heavy for durability and may have design features (decalage and airfoils) for the same reason. So when choosing look for weight and airfoil to suit your needs.

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