Most of the RC model gliders I designed and flew in the 1960's I used wing tip spoilers to turn since I would automatically get a coordinated turn (yaw and roll together). These always rose out of the wing and were flush when not being used. They were mounted just a short distance back from the leading edge to disturb the flow when raised. The front of the spoiler was the hinge edge so they were like a door opening.
Happy Anniversary to the start of the Colver Skysail ... November 5. 51 years ago ... Thanks, Frank, for your contribution to building dreams ...
Steve Pearson wrote:intuition based on previous experience
=============== After elevon gone: Rudder, Colver SkySail
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=========================== Choices might stem from objectives serving one's goal. Objectives vary. E.g. One might want to go for the lowest mass HG that gives L/D of 5, not more than 5, not less than 5. Such contrasts with an objective that reaches for a HG with L/D of 12. Getting clear on objectives may well help bring progress to a project. ========================== Which has more induced drag: a HG with L/D of 5 or a HG with L/D of 12? Are you sure? Is that even a fair question? I am not sure. https://www.faa.gov/regulations_policie ... h_ch03.pdf ========================== A HG is a potential energy user. How does a HG collect potential energy? Various ways! One way is to convert the energy of gasoline into potential energy. Another way is convert the kinetic energy of a thermal into potential energy. Kt takes energy to give altitude to a HG. What energy do you spend to get to launch altitude? What is the altitude of your home? What is the altitude of your HG's launch point? What is the weight of you, your gear, and your HG? Lift that weight from the altitude of your home to the altitude of your launch point; add the work to overcome the friction of your spouse, the friction of moving from home to launch site; add the energy needed to battle winds from during the trip from home to launch site. Add up the energy spent to pay for the things involved and means of moving. Add the energy expended in your body during the move from home to launch. Miss any energy cost?
JoeF wrote:========================== Which has more induced drag: a HG with L/D of 5 or a HG with L/D of 12? Are you sure? Is that even a fair question? I am not sure. https://www.faa.gov/regulations_policie ... h_ch03.pdf ==========================
I am not sure either. I would think that the poor L/D of 5 might be the result of greater induced drag. But that's not clear. They could be flying with a parabolic antenna mounted on the kingpost and pointing forward which ... would be all parasitic drag. The question may be ill-posed, but again, I'm not sure.
However, I am sure that you've posted a really good web site Joe. I've only skimmed that article, but it looks like the FAA did a very good job on it.
Join a National Hang Gliding Organization:US Hawks at ushawks.org View my rating at:US Hang Gliding Rating System Every human at every point in history has an opportunity to choose courage over cowardice. Look around and you will find that opportunity in your own time.
What energy do you spend to get to launch altitude?
Plus the energy to fly XC for 10 hours straight, or the energy to put together a team, and tow launch across the country. Energy out, energy in. Risk Reward.
Bob wrote
They could be flying with a parabolic antenna ?
Could a parabolic antenna be formed in the shape of an airfoil? Kind of a top hat.
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Sometimes you gotta' push the stick forward while you're lookn' at the ground
The L/D of 5 HG is not lifting as much as the L/D of 12 HG. "induced drag" is drag from lift. Then do we conclude that the L/D of 5 HG has less induced drag, but has more of other drag: parasite, profile, skin, .... We see a sleek sailplane and know it has less profile drag, but it fights sink because it has more lift, and thus more induced drag, less profile drag, less parasitic drag, less skin drag, less total drag. The puzzle question is about "induced drag." Not total drag. ======================================
Craig, thanks. So....... will electrically-assisted HG (eHG) eventually take over the scene?
JoeF wrote:The L/D of 5 HG is not lifting as much as the L/D of 12 HG.
I'm not sure if that's accurate. In level flight, the total lift is always equal to the total weight. Do the two weigh the same? It's not really specified. That's partly why I said that the question may be ill-posed.
It's also tricky because we say that the induced drag is the drag due to producing lift. But that doesn't mean that the induced drag is the same for all aircraft with the same weight. As noted in the FAA article, a long slender wing produces less induced drag than a short stubby wing. If they weigh the same (and therefore need to produce the same total lift), then the induced drag from the long slender wing will be less even though it produces the same lift.
Join a National Hang Gliding Organization:US Hawks at ushawks.org View my rating at:US Hang Gliding Rating System Every human at every point in history has an opportunity to choose courage over cowardice. Look around and you will find that opportunity in your own time.
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