Replies to This Discussion

Permalink Reply by Jonathan Lussier on August 23, 2010 at 9:55am

Maybe a few degrees, looks almost straight...

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ModeratorPermalink Reply by Hooks on August 23, 2010 at 9:56am

Is it this one?

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Permalink Reply by Patrick Hammer on August 23, 2010 at 12:40pm

Yup - that be it - I don't think its much either - something like 7-10degrees(?)

Would be nice to know excatly what the wing dimension/spec's/airfoil etc etc ..... is.

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Permalink Reply by Curt Olson on August 23, 2010 at 1:01pm

That looks a lot like a scan eagle with a tail and a straight wing. The tail would add stability (both horizontal and vertical.) I've never seen the original scan eagle fly, but just from eyeballing the airframe, I would expect it to be pretty bobby in pitch and also exhibit a lot of adverse yaw and be really slow to dampen that out. Putting winglets at the wing tips on a flying wing as your only yaw stability doesn't work nearly as well as you'd hope. The tail would address all of that and also help maintain stability at slower speeds and make it harder to stall/snap. Guessing wing loading on the original scan eagle, I have to think it would have a very high stall speed (by RC standards) and have a wicked stall/snap roll if you did stall it. Not sure what problems they might have had with the swept wing that would cause them to want to straighten it out, but maybe with the tail in place, they don't need to sweep the wing to get their winglets as far back as possible. It's fun to speculate based on random pictures and a smattering of personal experience with my own airplanes.

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Permalink Reply by Patrick Hammer on August 23, 2010 at 9:22pm

Curt

...... looks a lot like the Scan Eagle?
Correct - Insitu acknowledge the relationship between these 2 airframes. It is in effect the Scan Eagle's big brother - and was designed, in part, to address many of the flight characteristics you have commented on.

On RCgroups.com a member built a 50% model of the Scan Eagle. Its interesting to read his comments - again, many of them are along the lines of your observations. That model actually turns out to fly quite well.

Personally, I don't believe there is any one airframe and/or wing type that adds up to the perfect setup. Variation in design from one model/manufacturer to another will of course largely be influenced by the relationship between mission requirements and airframe performance, but I have little doubt asthetics and a need to offer the market something "different" come into the equation somewhere along the line - hence the swept wing design of the Scan Eagle(?).

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Permalink Reply by Curt Olson on August 24, 2010 at 4:35am

Patrick, just to go along with what you are saying, there is also the need for long endurance on a small amount of fuel. Or perhaps said a different way, a need to carry a lot of payload and fuel for the size of the vehicle and then fly efficiently with low drag. That can add up to an airframe that would be a beast to fly manually and that no RC pilot would enjoy flying. So definitely there are reasons the scan eagle is the way it is ... but it's still interesting to ponder the design trade offs. I didn't mean to sound overly critical in my first message. The easiest airplanes to fly and most forgiving (from an RC perspective) are either very draggy (trainers, fun flyers, etc.) or are very light weight and can't carry much of a payload without affecting their easy flight characteristics.

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Permalink Reply by Patrick Hammer on August 24, 2010 at 6:01am

Curt

Points taken - actually, I know next to nothing about airframes and flying or building RC models: one airframe is as good/bad as another to me.

I'm in the early stages of trying to decide which/what to build, so am investigating all options. My only advantage here is that I have the full Catia V5 suite of programs - and have a good few years experience using them - so that side of things will be fun.

Still, I need to start off somewhere. I've ordered myself a Cularis to learn to fly with, and while learning with that will start running through options. The conventional Shadow 200/400 UAV design is appealing. Its a pretty mature paltform and noted for its stability - but everyone and his dog has had a go at building and flying Shadow's. The Integrator is be an option to consider - similar but different.

How different? Good question.

Patrick

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Permalink Reply by Curt Olson on August 24, 2010 at 6:13am

I think that's one of the reasons there is such a huge variety of airframes available and huge variety of designs that people have tried. When it comes to balancing capacity, performance, endurance, handling qualities, and price as well other considerations such as specific payload location or configuration, desired power plant and desired location for it, special needs such as a specific environment that must be operated within (i.e. high altitude environment, marine environment, cold weather, hot weather), along with all the structures and materials issues ... there's no way you can build a one-size-fits-all airframe, and no way you can build even a couple sizes fits all airframe.

I can tell you that it's a huge thrill to see a design come off the drawing board (napkin?) and actually fly! And it's cool then to look at various characteristics and issues of the airframe and work through how to solve them or improve on them. So many of these things have already been studied and discovered and rediscovered long ago, so it's not like we are really learning anything new, but it's a tremendously fun and rewarding process to discover and learn for yourself ... and there's nothing like seeing your baby up and soaring for the first time.

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ModeratorPermalink Reply by Gary Mortimer on August 24, 2010 at 8:31am

@ Patrick... Cularis to learn with, oh my keep it in the box and buy an Easystar first

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Permalink Reply by Patrick Hammer on August 24, 2010 at 2:19pm

Oh great ............... thats just great to hear - it's made my day.

It can't be that much different - is it, Gary?

Permalink Reply by Krzysztof Bosak on August 24, 2010 at 10:24am

I think for learning pure rc EasyGlider has slowest flight, lowest wing loading and intuitive aileron action.
However has much less durable puller prop configuration, and is not evolving at all for cargo plane, not even UAV.

The only downside of EasyStar for learning is that it is louder and noisier, thus discouraging a few first-time flyers to takeoff on full throttle, because it is intimidating.
It is has also a few km/h faster stall speed than easyglider (some 35km/h vs 31km/h, but add 5km/h to both numbers when loaded with extra 200g equipment).

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Permalink Reply by Patrick Hammer on August 24, 2010 at 2:42pm

Yup - Iots of folk say the Easy Glider real easy to fly with. I wanted to get something that wasn't so easy that as soon as I had learnt I was going to find myself wanting to get something else.

Size was also an issue - I've worked in the defence industry all my life (antenna research/development), and free from the IP (intellectual property) clutches of my former employer I'm at liberty now to work on antenna ideas I've had in mind for many years - to play with those ideas requires an airborne platform slightly larger than the Easy Glider, and at least the size of a Cularis.

Antennas are the one aspect of RC/UAV and FPV flying that the hobby (and commercial/military) community have not given the attention to that all the other aspects of model development and hardware performance have been given.

Quite why is odd - its one component in the rf link chain of components that is free from any kind of regulation (as are rf link frequencies and their power outputs). It is also, in many respects, the easiest component*, on the electronic side, for amatuers to get a grasp of and experiment with (practicaly speaking) - so quite why this aspect to flying models lags behind so much I can't quite understand.

easiest component* - comparatively speaking that is - mind you, after nearly 40years playing with antennas and antenna theory, I still learn new things all the time!

Other than for the inherent size limitation on the airborne side of the link, there really isn't any limitation on what can be done with antennas - and they such an important component: antenna performance makes up 50% of your link distance (the other been power output - which is regulated - and the modulation type that is adopted e.g. QAM, QPSK, COFDM ... or whatever).

So understand where I'm coming from - yes, model flying has always appealed to me, but more so, its an excuse to play with some ideas I have, and maybe (just maybe) come up with something that will contribute to my pension (ha ha .....).

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