SeditiousCanary

I recently acquired a new/in box Sterling Models Inc. Diamant Sailplane. After being away from model airplanes for well over fifteen years, I have a re-sparked interest in flying models. CA glues were a somewhat new and servos were huge. I find myself with more options in some areas like servo options and better batteries, while having far fewer when it comes to kits and designs. I really enjoy building wings instead of using foam or shell wings, and there just don't seem to be many options. I also have a strong fondness for dihedral wing over polyhedral wings, of which there also seem to be very few choices. After reading a few manufacture websites, I have a good knowledge of servos that are being made, but little understanding when it comes to applying it. Here are the few questions I have that I am hoping you can give me some advice on. They all apply to the aforementioned Diamant Sailplane. I will be modifying the basic design a little to include elevators and I am considering adding both ailerons and flaps.

What torque servos should I be using for:
Rudder?
Elevators?
Flaps?
Ailerons?

What suggestions would you give me to make the wings removable (I have a small car)?

Do you think a T-style horo stab or conventional horo stab has better performance?

I am considering designing and building my own sailplane. I have found Micheal Selig's website (http://www.aae.uiuc.edu/m-selig/) to be very helpful on the listing of airfoils, but I am still having difficulties selecting a airfoil to use that have minimal drag and good lift. I plan on the model having about a six to seven foot wingspan and target weight of about four pounds.

Can you suggest any reading material to bolster my knowledge of aerodynamics or give me a few suggestions on well-suited airfoils?

Thanks for your time and help!

Chris

AcintSpec

Chris:

Servo examples that are commonly used would be (HiTech) 81 or 85 MG's for ailerons or flaps. Could also use the 125 MG wing servos there to but more pricey. Something along the lines of an 81 (light 2 meter) or 225 on elevator/rudder. MG (metal gear) especially helpful on flap servos is you are like me and slow on the draw retracting them on landing.

As far as airfoil goes, that depends on the designed use for your plane. Four pounds sounds a little heavy to me but then if you are sloping, this may not be to bad compared to flat land flying. Most of the 2 meter planes I have been flying weigh in around 2, 2 1/2 pounds or so. But then again, I fly thermal duration where the lighter loaded wing is a little more suited to the task. You may be interested in some of the airfoils that Dr. Drella has developed from MIT. References on the Charles River RC site can point you in that direction if desired.

Regards,
Gene

SeditiousCanary

Blast, I had been hoping to run some HS-55's for rudder and elevator, but they only have a pound of torque compared to the 4 pound range of the servos you suggested. Well, add nearly another ounce to the model for rudder and elevators and an ounce for flaps and ailerons.

It's been tough looking at all the new radio stuff that have come out and knowing what I could use and what would not have the power to do what I need. I am guessing that the receiver and battery pack should weigh in at about 150 grams or so. I plan on running a 4.8V setup and using a 4 cell battery pack. Most of them seem to be about 115 grams to 135 grams. Receivers seems to be about 20 grams or so. Four servos (2 HS-81MG and 2 HS-225MG) should add up to about 100 grams. Sadly, I can't really find weights on things like Du-Bro hinges, bellcranks and push rods, so I can't really do too much guessing there unless I took my Ohurs triple beam into the local hobby shop. If my Diamant is any sort of comparison, the model should weigh about 450 grams once it is covered and wheels are in place with no RC gear. So we are already at a guessed weight of 750 grams without any linkage. Add to this that I tend to overbuild things so I don't have to rebuild things, I am guessing that adding a few bits of plywood here and there, bass in place of balsa should drive it up about another 120 or 250 grams. I do plan on keeping the weight down, but don't know how much weight will be added in the overbuilding process.


So, to drag this out ever further, how long can I expect a 4 cell battery pack to last? I live in Tucson Arizona and we have nothing but heat for about 70% of the year. I suspect thermals are a dime a dozen, but from what the local hobby shops have said, there are very few people buying soaring stuff, so I have to go at it alone. I also expect that my interest will be duration soaring with a few tricks thrown in here and there (control line combat habits are hard to kill).

The only sad part is that I will be moving to either IL, MI, MA or lesser DC area in June or so for my wife to attend grad school. This will kill my nearly endless thermal source, but I have flown in DC before.

BMatthews

I remember seeing one of those kits in the bones. I hate to say it but this was NOT a model for any sort of serious or even sport flying. More than many other models of this type the Diamant was intended for hanging from a cieling. Or at most a few hand tosses at the local bump in a park. The stock wing structure will not take any sort of decent launch. As I recall the spars were all balsa of rather small dimension. Nothing with a decent load carrying capacity to resist the launch loads. Even a low power high start may be too much for it.

Now if you modify it to add some form of decent spar system and then cover the whole framework with 1/32 sheet plus add full controls then you may have a nice fun sport scale model. But frankly the amount of mods required would make it a long building project.

While I always enjoy hearing about someone coming back to the flock I cringe at how you may have stacked the deck against yourself in that moment of zeal. You may want to look into some other options to ease your return. Something that will have a better expectation of a good lifespan in the air.

Good luck, welcome back, and I hope I have not scared you away.

PS: If you do carry on with the Diamant then it's a light enough model (especially if you carry through with the tissue or light plastic fabric covering) to use the HS55's or other park flyer servos just fine. A model of this size and weight will not over power such a servo. I'm assuming you use separate servos for each aileron then one each for the elevators and rudder. Just keep the hinges free moving. If you plan on one servo for the ailerons with linkage then shoot for the HS81 or equivalent mini servo for the extra torque.

For all your bigger and heavier plans you WILL need standard and mini servos depending on the task.

SeditiousCanary

This is exactly what I thought too. I am already planning on beefing it up with better spars, shear webs, skinning the front (if not all) of the wing, relocating the horo stab, adding elevators, adding ailerons, adding Fowler flaps, placement of four servos instead of the designed one servo, wingtip and tail draggers, making a new canopy (mine is cracked) and I'm even trying to figure out an easy way to make the wings removable. It's really not going to be the same plane. I have considered just building it as is for the practice and then designing and building a model that will be more like what I am thinking about converting this one into. I think the project of doing it would be fun, if not a little time consuming. I know the Diamant won't be everything I want, but it's a 30 year old model.

BMatthews

As long as you're going into this with your eyes open and an understanding mindset then I'll just wish you good luck and enjoy the trip.

One thing for sure. It IS a cutie and will brighten up any chunk of sky.

SeditiousCanary

I understand it's going to be a huge pain.

I never really did kit bashing, so I expect it will be like building a 85% cut out scratch build with documentation on about 70% of what to do. I also expect there will be some fabrication for controls where there were previously none, and to accomidate things it wasn't designed to (like Two bloody servos, sheesh...). But this is what I love, figuring out how to make things work and working with my hands.

aeajr

My Feedback: (2)

I am not really a builder, so forgive my dumb question. Why invest a lot of time taking a model that really doesn't lend itself to your goals and start modifying it. Kits are not that expensive adn plans are even cheaper. Why not build something that is intended to meet your goals, what ever they are.

SeditiousCanary

Well, two reasons. First, I like the modification process and figuring out how to get it to work. Second, There aren't that many kits out, let alone kits for what I'm looking for (namely a 2M sail plane with flaps, ailerons and that is not a polyhedral). I'd be better off bashing a kit or scratch building. I have no problem scratch building, but I figured a kit would be a good place to start for my first model in several years.

aeajr

My Feedback: (2)

There are a lot of kits of the type you describe.

But clearly it is the challenge you like. I can understand that.

Enjoy the kit bashing. Hopefully you will keep us up to date on your progress. maybe you can post some photos along the way.

Have fun with it!

SeditiousCanary

Really? I can't really find any. Who makes them?

aeajr

My Feedback: (2)

[/quote]
Well, two reasons. First, I like the modification process and figuring out how to get it to work. Second, There aren't that many kits out, let alone kits for what I'm looking for (namely a 2M sail plane with flaps, ailerons and that is not a polyhedral). I'd be better off bashing a kit or scratch building. I have no problem scratch building, but I figured a kit would be a good place to start for my first model in several years.
[/quote]

Perhaps I don't really understand what you want, but let me throw out some ideas.

www.nesail.com
lots of sailplanes of all kinds - Tend to be more to the high end, but definately high performance planes available.

For lower cost type kits these might be of interest

Great planes kits:
Of course there is the standard spirit, but that is the poly wing you don't want. So consider these. You might still do some minor mods, but not as much as what you were talking about for the other kit

Spirit elite - 2M full house - build with or without dihedral
http://www.greatplanes.com/airplanes/gpma0535.html

100" full house, again just remove any modest dihedral
http://www.greatplanes.com/airplanes/gpma0550.html

Dynaflite Bobcat - just work in the flaps
http://www2.towerhobbies.com/cgi-bin...?&I=LXE621&P=0

Are we getting closer?

SeditiousCanary

Hey, thanks. That was helpful. I like more classic planes I guess. The Extreme DP R looks like something I would own, though I am oddly werry of carbon or glass fuses that are smaller then my thumb. I like built up from wood stuff. I guess this is a sign of the times.

OK, I'm a dork...

What are spoilers? Are they air brakes, or what I would call air brakes?

aeajr

My Feedback: (2)

There are two secondary control surfaces, usually used in landing but not
always.

Flaps - These are a moveable part of the trailing edge of the wing that you
lower to slow a plane while adding lift to the wing and LOWERING the stall
speed.

Spoilers - Typically used in landing gliders or sailplanes, these are on the
top of the wing. When these are raised, they reduce, or spoil the lift of the
wing in that area. They can help slow a plane down and RAISE the stall speed
of the plane causing it to descend from lack of wing lift. These can also be
helpful in getting sailplanes out of strong thermals.

When they "spoil" the lift of the wing they allow the plane to come down on a flatter glide path. They can help you land in smaller areas, or on a precise location. They can also help you get out of a really powerful thermal. I have spoilers on both of my 2 meter gliders. See the photos below.

If you read the term RES, that means Rudder/elevator/spoilers.

Many intro gliders are rudder/elevator only. The polyhedral wing helps the plane to turn and makes it more stable as opposed to a flat wing which is harder to fly and requires more attention.

The addition of spoilers to a poly wing keeps the controls simple, but gives the plane much better landing characteristics.

Hope that wasn't too much.

The first photo is of my Sagitta 600 RES 2 Meter. Note the Spoilers are up. I just landed the plane.

The second shows the inside of th spoiler. These are operated by a single servo connected to the throttle channel in the fuse that pulls a pair of strings that lift each wing's spoilers

The third photo is of the servo mounted in the wing of my Spirit 2M RES plane. Here there is one servo in each wing. They are connected to channel three, the thortle channel via Y cable.

aeajr

My Feedback: (2)

You might want to visit this thread. People are talking about their favoriate gliders/sailplanes.

http://www.torqueroll.com/forums/sho...s=&threadid=58

SeditiousCanary

Not at all. I'm already looking at Reynolds numbers for these airfoils:
S7012
S7055
RG15
RG15A111
RG15A213
E205
S3021

I want to design my own sailplane (which I think I have mentioned), and I have a painfully high appreciation for taking advantage of knowledge rather then trying to rediscover it unnecessarily. I tend to ask questions ahead of the rest of the class since tend to think further ahead when trying to understand how something works, or as in my case, how to make it work better. Most things mechanical make sense to me without any sort of formalized training. Then again, I have spent most of my working life as a bicycle mechanic, computer mechanic or some other kind of mechanic. In the case of my Diamant, I wanted to improve a few things I saw as easy improvements (assuming you thing adding 25% of chord Fowler flaps to a 4.2" chord wing with about a 8:1 aspect ratio [closer to 10:1 at the 75% point] and adding ailerons to a plane which doesn't normally have them). Retracts seems to be going to far, though I have a nifty idea for how to do it easily, at low cost and with some rather nice socks. Damn that bicycle suspension knowledge...

The thing I wish I had more first hand experience with and could find more information on is levers, cams, controls arms and how they all work together. For example, I look at retracts on the market, and I get how they work. I also think they are far more complicated then they need to be, but I am frustrated with how little I know when it comes to figuring out how much servo throw will affect a control arm, and in turn how the control arm will affect the gear, flap, gizmo thing. I have some ideas, but don't have any idea how to execute them.

Have I mentioned that my dad is an aeronautical engineer for NavAir? Or that my grandfather flew a Grumman F6F Hellcat in the Pacific Theater? Lets just say I come from a long line or airplane enthusiasts.

aeajr

My Feedback: (2)

Well my friend, you and I have a lot in common in terms of asking first and thinking out front. My college major was Business, but I have a minor in Physics. Interesting combo, yes?

You are ahead of me in the pure aerodynamics. I don't speak reynolds numbers yet. Someday.

Here is how I would suggest you proceed.

Pick a plane, advanced or basic, that you like and build it stock. Planes like the Spirit 100 allow you to build two different kinds of wings. Build them both!

Fly it! Analyze it as a baseline.

Now, working from there look for opportunity for incremental improvement, or radical new design. replace the wing, but keep the fuse as a development platform. Push the wing as far as you can, then, when you think you have what you want, work on a new fuse design to complemnt that wing.

Then finally, go back and tune the wing to the fuselage.

This is what I would suggest. This is what I would do. If you have no base line to measure against, how will you quantify the improvements?

You get to have some fun flying while you develop. You can always slap a stock wing back on for a relaxing day of thermaling while you thing about the new wing.

On the other hand you can start from scratch, in which case, why are you looking at kits?

SeditiousCanary

So I can spot obvious things which nobody makes. If I want it and it doesn't exist, everyone else does too, right?

aeajr

My Feedback: (2)

Oh! I see.

Well, let me knwo how I can help. I would love to follow the development.

Perhaps I will do an article on you and the development of a new glider.

SeditiousCanary

That would be cool. I can't say it'll make me more or less motivated to get it done, but it would be cool none the less.
I'll be sure the document the process.

aeajr

My Feedback: (2)

Post to this thread and we can keep in touch, or send me a PM through the forum.

Or, you can post up at www.torqueroll.com. I moderate the glider forum there.

In any case, keep in touch and you can share this new creation as it unfolds.

mmartin55

Chris,

Send a picture of the Diamant in the air and on the ground when you complete it and give us a report on your modifications with pictures and the flying characteristics. I'd like to include your findings and documentation on my web page... I'm sure my visitors will be interested in your experience.

Also if you post on the other sailplane forums you should find someone who can share very similar experineces with their Sterling Diamant. Good luck,

Tom
http://www.lightfastgraphics.com/schweizer_126.html[URL]

SeditiousCanary

Wow, and old thread. Frankly, I've stalled on the project due to researching other construction methods. Thanks for reminding me though. I'll see what I can do to get it done.