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Old Nov 29, 2004, 08:31 PM
TROUT OR THERMALS
steelhead's Avatar
Eureka, Ca
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CROSS COUNTRY PROJECT... OR... EVERYTHING YOU WANTED TO KNOW ABOUT XC on the Cheap :)

Howdy all-

Im excited about big planes. I need to build one (or more) now.

Several friends of mine and I are about to embark on a beautiful quest. We HAVE to start flying CROSS COUNTRY RC SAILPLANES.

Hopefully this thread will prove useful to others than just my small group of remarkable individuals. I'm hoping it will answer many questions and help promote the sport.

It seems that most people who Fly XC contests all fly the RnR SB XC. From what little I can actually find of the sport online, I'd say as much as 80 to 90% of the planes flown are these, with a few self designs and a few unlimited contest birds along the way.

How much must one spend to be competitive?
What and how much radio gear and electronics is necessary?
What are the rules?

I've read about some people flying their 120 inch unlimited birds with Varios tucked into the fuse, and I've even read that some people have flown a large amount of course with a 2 meter glider, and no extra electronics.

I would very much like to build a large bird in my shop, and since I have a sailplane manufacturing shop, I should be able to do most all of it here. Hopefully saving a few dollars, and having fun finding a less expensive entry into the sport.

I do have to admit- my knowledge of RC sailplanes ends at about 120 inch span. Does anyone have access to designs that they can share the specifics on the airframe? Span, area, length, airfoil, tail and nose moments etc?

How many people out their have flown self designs?
Should I just load up an unlimited bird and fly it, or should I go for the vario and the rest of the hot shot gear?

During my research, I have read that you should expect to spend 2 to 3 grand on the gear and airframe. Why? I know that large birds are expensive, but I should be able to construct an airframe from bagged wings and a "3 or 5 off" fiberglass fuse perhaps with the "lost foam technique" and spend a decent bit of money on the spar system, right?

So far, the only "do it yourself planes" that I've really seen are the Sagitta XC and the PARAMOUNT. Are there any others out there? Any planes that would lend themselves to 12 to 14 foot spans and foam coare wings?

What is the minimum amount of gear that a person would need to at least not get last place at a XC event?

Im not looking to win. I just am looking to have a good time, something to look forward to rather than "timed lawn darting" and enjoy a good group of people and a hearty BBQ picnic as well.

Well, if anyone has knowledge to spare, Im looking forward to discussion and photos of your ships, both store bought and homebuilt.

Who knows, perhaps we will come out with a less expensive entry level XC sailplane and boost the participation and number of events

Dean
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Old Nov 29, 2004, 09:45 PM
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United States, AL, Madison
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No need for all that $$. You do need to invest in a good Vario, though. You want to be high all the time. When the plane is a speck in the sky, you need the vario to tell you if you're in lift or sink.

Go lookup some old copies of S&E Modeler magazine. Gordon Jennings wrote a 2-part article on X-C plane design. He gave a lot of design parameters that should get you started.

You don't need a high $$ plane. I know some of the top guys prefer rudder/elevator only. You want a stable plane that will keep going where you point it when this 13' plane is a mere speck in the sky. Yes, they sometimes fly into clouds.

The only "rule" I can remember is your plane must weigh less than 5kg. This paramater alone drives a lot of other decisions. Gordon went into this very well in his articles.

Other rules are dependent on who's running the contest. Most allow multiple launch attempts (before you enter the course).

A few places to look for good reading and stories are:

www.xcsoaring.com
www.yahoogroups.com/group/xcsoaring

Yes, you'll find most out there willing to invest the $$ settle on the SB-XC. You can do just as good with your own bird. Don't scrimp on $$ for the spar.
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Old Nov 30, 2004, 12:15 PM
TROUT OR THERMALS
steelhead's Avatar
Eureka, Ca
Joined Sep 2002
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Does anyone have those copies of the article? Know what dates etc?

Any links for Varios? I've used the Picolario before.

Any allowances for onboard video? Or is it more a test of eyesight on pilot and crew?

Any photos of homespun planes?

Thanks for the info-

Dean
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Old Nov 30, 2004, 01:05 PM
Think Thermals!!!!
SoCalGliderFlyr's Avatar
Costa Mesa, California
Joined Mar 2004
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Been working on an airspeed feedback for the elevator. On board closed loop system.
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Old Nov 30, 2004, 08:38 PM
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Eureka, Ca
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Running the numbers with a friend of mine, It looks like a 150 inch span should work pretty well.

What are some other opinons on lower aspect ratio wings being used, instead of higher aspect wings and the ability to see them from a distance?

We are also looking at the materials list for a bagged wing using wood laminate sheeting and a beefy spar.

Also- A few emails have come my way that have stated I should take a look at a sailair kit. It is my belief they are not being produced any more. Does anyone have a set of plans or a kit for this plane they would be willing to part with? A modernized version might be a good starting point for this project.

There are soooo many varios and electronics- what is the least expensive vario system out there that would work?

Dean
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Old Nov 30, 2004, 09:28 PM
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you don't want to come in last, right? You want a plane to cover the miles, not float in the clouds. Forget the Sailaire. Too light, and too slow. IMHO

Some sacrifice of aspect ratio may be prudent, just to give you a larger, more visible, wing chord. Pick your span, AR, area, airfoil accordingly.
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Old Nov 30, 2004, 09:49 PM
Think Thermals!!!!
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Joined Mar 2004
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How about the Ed Slobod Paramount?
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Old Dec 01, 2004, 03:54 PM
Who needs a pilot??
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Alexandria, VA
Joined Jul 2002
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I like this thread!

I started doing XC with a small <2m powered glider in pretty much downtown Raleigh, NC. I would take off from a local field, turn on the onboard video (stored, not live), and get trucking. Never really did a real distance attempt, as flying over a shopping center, local college campus, and a medium sized lake was enough adrennaline for me. Flight distance was probably around 3 miles for a 25 minute flight. May not have been fast, but it was really fun....

If you're just looking for a challenge and to feel out how hard XC can be, take out a trusty RES floater and hop in a car (yes, cars work too if you don't mind hanging your head out from time to time) and just go out and back. It's really disorienting the first few times, so it pays to learn on a forgiving airplane.


On another note, I haven't ever flown with a vario onboard. Besides the Skymelody, are there other model varios available? Maybe a DIY project with some guidance from a website? I'm really interested in this little piece of XC gold, but don't have the $500 to drop into the Skymelody. Any ideas?

Dan
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Old Dec 01, 2004, 03:58 PM
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Eureka, Ca
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The paramount is looking like a good entry level ship. Really excited to hear that new CAD plans are being drawn up for it, It has good lines. Is there enough room in the fuse for the electronics? How many kits were originally made, and where are the original plans available from?

Dean
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Old Dec 01, 2004, 04:56 PM
Think Thermals!!!!
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Paramount: From what I have been able to gather the first and only production run in the early 80's was about 30 kits. The fuse is very generous in volume at 2.75 wide by 3.75 deep at the thickest point just at the wings LE. It could be a bit less deep to reduce the frontal area and still have room for a thermal sniffer.

About the plans: Midway Models has "ownership" of the Ed Slobod plans and the templates for the kits. Also has one of the original kits as a reference. The original plans do not have the rib outlines on them. This is way they are being CAD'd. Also it was reported by a couple of the original flyers that the stabilator was a weak design. This is being corrected.

Should this be re-kited I would expect it to be expensive as there is a lot of wood in this plane! The intent is to provide self explanatory plans and short kits to those that really want to build this plane. Yes, all three or four of you!

A cross country plane needs to be big so you can see it from the ground. Fourteen foot wing spans and larger are not uncommon. The Paramount was launched via hand tow with a hi-start. I would think that 500 foot AGL was the release altitude. The Paramount's fuse does not have the customary 1/4" square stringers at the intersections of the fuse sides. Other wise there is nothing trick about it. It's just a very large D tube build up with a semi symetrical airfoil and flaps. No ailerons.

The biggest problem is sensing lift and over speed in your runs. A thermal sensor takes care of the first. An air speed sensor coupled to the elevator should take care of the latter.
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Old Dec 01, 2004, 07:05 PM
TROUT OR THERMALS
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Eureka, Ca
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Since I have all the capability, I am trying to make my wing from foam with wood sheeting bagged on. This would save the time of all the balsa and plywood ribs, making investment less (time is money) Instead of 90 ribs, I would plan on making 10 plywood ones, and spending more time/money on the carbon and plywood spar.

My interest in the SAILAIR was becasue the aspect ratio and the moments seemed to work well, providing a good visibilty, and not allowing the plane to go too fast. The plane simply did not go too fast, from what I hear. Also- I hear that "going too fast" is a very large beginner mistake...broken spars..sheered wings etc....

How is an airspeed sensor hooked to the elevator?

Dean
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Old Dec 01, 2004, 07:24 PM
Think Thermals!!!!
SoCalGliderFlyr's Avatar
Costa Mesa, California
Joined Mar 2004
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Would have to capture or go between the receiver and elevator servo. Use a three possition switch on a aux channel to set speed, cruse and thermal speeds. Needs a pito tube or other sensor on the outside of the fuse in undisturbed air. Doing it with a PIC processor and a pressure transducer. Pilot movement of the elevator would disable the feed back loop for a set time or until the three possition switch changes state.
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Old Dec 01, 2004, 07:41 PM
Think Thermals!!!!
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Thinking this might even be a seperate form here under Sailplanes.
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Old Dec 01, 2004, 08:01 PM
Think Thermals!!!!
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Costa Mesa, California
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Here is a web site just for cross country:

http://www.xcsoaring.com/

Here is a picture of some planes and contestants in a recent contest:

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Old Dec 01, 2004, 09:05 PM
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Eureka, Ca
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I love pics like that But it does stress a point- I see only 3 or 4 planes that appear to not be stock SB XC's. How well did the team with the yellow scale glider do?

Has anyone recently contacted RnR to see how much an SBXC costs? How much are the replacment parts? etc?

I love the classic birds like the Sagittas and the Paramounts, Just really interested in the low-tech meets high tech aspect of it all.

Has anyone built a 12+ footer using sheeted foam wings? What was the all up weight of the contest ready plane?

Dean
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