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Old Aug 12, 2009, 10:23 AM
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pinnedup's Avatar
Los Alamos, NM
Joined Jan 2007
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What are the advantages of larger gliders?

I have been flying my 2m Chrysalis for about a year and am thoroughly enjoying the glider. I still have a lot to learn and skills to develop with this glider but I am looking foreword building another woody in the near future, likely a Marauder or the rumored 3m Chrysalis.

My question is what would be expected from and what are the advantages of a 100 inch or 3 meter glider verses a 2m glider? I understand that a larger glider will be more visible at higher elevations, that it should penetrate the wind better and may be more stable. Will the glider climb stronger with less lift? The larder glider will require a larger high start or winch and possibly a larger flying field, so there will be trade offs.

Thanks for your input.
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Old Aug 12, 2009, 10:35 AM
Gasbags & Gussets
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Riverside, Ca
Joined Feb 2009
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Bigger is better...

my 2 cents.

100" i think is the optimum size for building, traveling, hi-starting, and winching.

Supersize/Transform a 2M to a 2.5M, everything *exactly* the same about the 2 models, i believe the 2.5 will stay in the air longer and be easier to launch(less twitchy).

You would need another hi-start, dynaflight makes a 'standard' size highstart that i use.

edit => 3m is pretty big, flys the longest, most build time, more costly, need Heavy duty high start, look extra cool, are a pain in the donkey to transport, really can fly all day, i have 2 of them and prefer the smaller 2.6m models.

Hopefully the Crysalis guys will 'supersize' the glider you have already, give them a call and ask. At best they say yes , worst they say no dice

john s.
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Old Aug 12, 2009, 11:01 AM
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United States, MA, Waltham
Joined Dec 2001
6,893 Posts
Aerodynamics are better as gliders get bigger. You can increase the aspect ratio a bit AND increase the chord so the Reynolds number goes up and the span loading goes down. That means profile drag goes down, and induced drag (relative to the weight, anyway) goes down too.

Unless your field is pretty small, you can probably fly a 3m model there. Especially a light one.

It's probably easier to hit a spot landing with a smaller model.

If you're up for it, I suggest a Bubble Dancer. However, keep in mind that I haven't built one, that it's a scratch build, and that you'd have to be a real craftsman with a lot of persistence. On the other hand, it's a fantastic flyer. I have an Ava which is the next best thing.

I agree that 100 inch is a nice size. However, with a 3 piece wing with a moderate center section, 3 meters or more is not so bad. Especially if the tail feathers are easily removable.
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Old Aug 12, 2009, 12:15 PM
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United States, AZ, Douglas
Joined Nov 2007
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Simply put... Bigger is BETTER!!! Smoother flying, longer flights easier to keep track of at altitude and so on and so forth.

On larger models I'd advise that you look for one that has a break down wing to make transporting it to and from the field a lot easier. My 3m Paragon is a 3 piece wing and it's a breeze to haul to and from the field. I'm currently designing a 4.5m sailplane that will have a 4 piece wing that will bolt onto a pod and boom style fuselage.
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Old Aug 12, 2009, 02:29 PM
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Jim Deck's Avatar
Valparaiso, IN
Joined Apr 2005
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As you get older..

As you get older, you'll appeciate that the larger sailplanes are easier to see at a distance. Include this with the other advantages previously cited.
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Old Aug 12, 2009, 03:46 PM
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LI, New York, USA
Joined Mar 2003
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Let's address your questions and assumptions one at a time. What follows are not facts as much as my opinion and my experience. Your smileage will vary.

Quote:
Originally Posted by pinnedup

My question is what would be expected from and what are the advantages of a 100 inch or 3 meter glider verses a 2m glider? I understand that a larger glider will be more visible at higher elevations,
The advantage of size is the ability to range out further and climb higher in search of or working lift. This is only an advantage if you will actually range out. If you don't go more than 100 yards beyone the edge of your field and won't go abover 1000 feet, then this size will not buy you much. You can see a 2M quite well 1/4 mile out and I have flown my 2M Spirit close to 1/2 mile out. So if you don't have a big flying area, size may not matter in this respect. Of course if your eyesight is not so good, certainly a larger plane might be helpful.

Quote:
Originally Posted by pinnedup
that it should penetrate the wind better
Penetration is a function of airfoil and wing loading. I have seen many 2M planes that penetrate very well. The Duck, for example, is a 2M plane that handles wind very very well. I don't attribute penetration to wing span, but others may differ.

For example, I think the MH32 airfoil would generally be considered to penetrate better than the 7037 airfoil for a given wing loading. Opinions will differ.

Typically a higher wing loading will penetrate better than a lower wing loading. But that is a general rule, not an absolute.

Quote:
Originally Posted by pinnedup
and may be more stable.
Here I agree. Think boats.

You put a small boat and a big boat on a smooth lake and they are both stable. Now put 3 foot waves on that lake and they will impact the small boat much more than the large boat. If you can see that image you can understand why big planes tend to be more stable than smaller planes.

Quote:
Originally Posted by pinnedup
Will the glider climb stronger with less lift?
Not a function of wing span. Certainly the 60" DLGs fly in super light lift. This is really more a function of wing loading and airfoil again. That 60" 10 oz DLG with a 4.5 ounce/sq ft wing loading will likely out climb my 3M Legend at 82 ounces and 13 ounce wing loading.

But my 127" 45 ounce AVA, at 5.7oz/sq ft may outclimb them both in light lift.

Quote:
Originally Posted by pinnedup
The larder glider will require a larger high start or winch and possibly a larger flying field, so there will be trade offs.
That all depends on how strong of a hi-start you have now. I have one hi-start. It launches my 2M 38 ounce Spirit, my 45 ounce 127" AVA, my 3.4M 65 ounce Supra, my 82 ounce Legend. And it will handle bigger planes.

So, what HS do you have now?

The key here is how much pull will your hi-start generate. You want a minimum pull of about 3 times the weight of the plane. You will get stronger launches with 4X or 5X the weight of the plane. However a delicate wing may be stressed at 5X.

If you are not sure what pull your hi-start generates, you can pick up a fish scale at the local sports store and test it. My hi-start generates about 13 pounds of pull at 150 foot stretch. That is my Spirit launch position. At 300 foot stretch it generates 25+ pounds of pull. That is my Supra, Legend and AVA launch position.

As for field size, well that depends on you.

If you are going to launch off a full size HS, you typically need about 800 feet to launch. That is true for a 2M glider or a 3.5M glider. So the field requirements are pretty much the same. If you have an 800 X800 field you should be able to fly anything from there. If you have a 300X300 foot field, approximately two football fields, use a smaller hi-start. I don't see the size of the plane itself as a big issue if you are a competant pilot.


As for transport, that depends on the wing. A 2M plane with a 1 piece wing has a wing of 78" long. My 122" Thermal Dancer has two 59" Wing pieces that are easier to transport. My 134" Supra has a 3 piece wing with the longest section about 58". Both fit in my car better than a 1 piece 2M wing.


That is my view.
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Old Aug 12, 2009, 04:08 PM
planepainter
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Mt. Juliet, TN
Joined Sep 2008
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I agree with Jim. Larger is easier to see. I fly a 2 meter Spirit on a regular basis. It launches well and has a good wing. It flys almost hands off.It is a blast and fun to search out that lighter lift. With that said, it can be touchy to land in wind and even though it is lighter, it won't stay up there as easily as the bigger more expensive birds. It is all about efficiency.
I also have a Riser 104. It is majestic in the air and is easily seen farther out. Very easy to handle as things are just a bit slower. But it too does not have the endurance of the larget spans. It transports easily as the wing breaks down in halves. But having flown with all kinds of planes I am convinced that if I want to launch and stay up I will need to get a better plane. I recently flew my Riser with a guy that had a Paragon. Even though the Paragon is an older design, the span is bigger and compared to his my plane was like a fat man running up hill trying to catch a bus! I am going to build my own design with a 132" wing span and when Isthmus finally offers an EZBD will most likeky build that too. Or an OLYIII. PP.
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Old Aug 12, 2009, 04:15 PM
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United States, TX, Weatherford
Joined Nov 2002
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Jim said it much nicer that we do in West Texas... Old Kurmudgeons can see 'em better! Same message though...

Jack
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Old Aug 12, 2009, 08:01 PM
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Crestview, Florida
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TNSFS!!!! There's no substitute for span!!
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Old Aug 12, 2009, 08:12 PM
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pinnedup's Avatar
Los Alamos, NM
Joined Jan 2007
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Thanks for the comments, seems the consensus is that visibility at altitude and distance is the main advantage of a larger glider, with the advantage of increased stability.
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Old Aug 12, 2009, 08:41 PM
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Fairlie, New Zealand
Joined Nov 2006
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Not only that, but every sailplane has induced drag at the tips and interference drag with the wing/fus joint. Increasing the span dramatically increases the L/D ratio. That's why a 3m sailplane can weigh twice as much as a 2m but still outperform it, even though wing area is only 50% more and so wingloading is higher.

I put a 500mm centre section on my Chrysalis to make a 2.5m span. I'm VERY happy with it's glide, although I haven't compared it with a 2m.

Oh yes and it went on a diet and weighs 32oz with motor and 3s2100

Nick
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Old Aug 12, 2009, 10:02 PM
Balsa breaks better
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Buchanan Mi
Joined Apr 2005
2,068 Posts
My best performance at the NATS was with a 140" plane called the Legion Air.
Jim also flew it.
I did better with the Legion Air than my Wanderer 99 (not by much though, more flight time), 2m Osprey and 126" Victor (I was starting to improve with the Victor in the last three rounds. I'll learn how to fly that moldie yet!).
My best flying plane is a 173" Super Esprit.
In my youth bigger flew better, now bigger still flies better but I can see what I am doing!!

Joe
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Old Aug 13, 2009, 01:57 PM
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Quote:
Originally Posted by Tappet
TNSFS!!!! There's no substitute for span!!
I SECOND THAT!
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Old Aug 13, 2009, 02:45 PM
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Joined Aug 2005
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Oh yeah, don't forget that when you fly higher, thermals are stronger but then again they can suck your plane up and you'll loose control. Now from 1000 - 2500 ft up, how far will a glider fly??? Pretty far!!!


To me, big planes fly like trucks and respond slowly. Smaller planes react faster - at least from my experience. You will probably need to react sooner in a bigger plane than a smaller one.

Each has their advantages and disadvantages. I figured I would give a few. All types of gliders are fun for some similar and for some different reasons. It is a blast to catch a thermal and all gliders can do that. Sometimes just switching to a more modern design will get you a performance gain. Look how things have changed of the last 10 years - in any glider class 3M, 2M or DLGs. All are far better now than just ten years ago.

Keep flying and having fun!!!


To me, you need to have many planes from ALL CLASSES of gliders!!!

(he who dies with the most planes - wins!!)
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