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Motorglider wings?

B

BlueRidge

Member
Van is a soaring enthusiast. Do you think the RV-12 would be a good candidate for longer wings to make it a motor glider?

I wish Van would design a kit for something similar to a metal Fournier RF4.

The RF4 is a beautiful aircraft but the cockpit is sized for small Frenchmen. We need an American version!
 
Glider pilots are in a very small subset of pilots. Much like the small number tailwheel pilots compare to the overall pilot population. Those who buy prebuilt gliders are in a smaller subset of glider pilots, and those who build EAB gliders are in an even smaller subset. That means the market for a EAB motor glider is really small for a business case.
 
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I wonder if the center carry through would be adequate to handle the additional loads from the longer wings??

Tail/pitching moment?

While building a set of "glider" wings might be a fun project-------safety first.

When in doubt, research it out.
 
Its not quite that straight forward ...
Longer wings will require a larger fin/rudder to maintain stability and counter the greater adverse yaw - ailerons are further out.
Longer wings usually have thinner chord so a different tailplane (& elevator if there was one) is needed.
That will mean cg envelope will reduce.
One change means several others are required.

Will longer wings really provide a sailplane of any worth? Probably not.
Even in Europe where soaring is much more popular than in the US there are not many motorgliders, and hardly any homebuilts.
Perhaps the only benefit was licencing, but with recent light sport changes that is no longer relevant?

Potentially a lot of effort for not much gain
 
penguin said:
Its not quite that straight forward ...
Longer wings will require a larger fin/rudder to maintain stability and counter the greater adverse yaw - ailerons are further out.
Click to expand...

Not necessarily. Have you seen Al Bowers (NASA Armstrong) work with the Prandtl ‘33 work and incorporating work by the Horten brothers? Proverse yaw not adverse yaw. How? Essentially by fly-down wingtips. Shoot for an overall bell curve lift distribution instead of elliptical. We should note it was Prandtl pre-WWI who found elliptical as most efficient for lift production in a given span. In the interwar years, hence the Prandtl ‘33, he was instead looking for optimum lift for a given mass. Think about it, fly down tips means less upward bend and less stresses through. It also means less to no need for rudder hence less mass (still need a rudder, propeller and all). Adverse yaw is a side effect of mostly extra fly up induced on the outside wing (there is a touch extra parasitic too). Fly down instead will push that tip forward. If you’re going to experiment with longer wings, even if it be merely mental experiment, experiment with wing design too. As for ailerons further out, true only if you’re maintaining proportional roll rates. Some planes have outer and inner aileron only using inner at high speeds. Interesting, the Hornet uses differential stabilizer for roll both high speed and high AOA with aileron only in the mid ranges.
 
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penguin said:
Its not quite that straight forward ...
Longer wings will require a larger fin/rudder to maintain stability and counter the greater adverse yaw - ailerons are further out.
Longer wings usually have thinner chord so a different tailplane (& elevator if there was one) is needed.
That will mean cg envelope will reduce.
One change means several others are required.

Will longer wings really provide a sailplane of any worth? Probably not.
Even in Europe where soaring is much more popular than in the US there are not many motorgliders, and hardly any homebuilts.
Perhaps the only benefit was licencing, but with recent light sport changes that is no longer relevant?

Potentially a lot of effort for not much gain
Click to expand...
This s pretty much dead on info - and a good example can be found with the Sonex Xenos. The Xenos motorglider has the same cockpit and firewall forward as a Sonex sport plane, but when they added the long glider wings, they had to extend the tail cone several feet, and the stabilizers/ruddervators are use compared to the Waiex V-tail…all to make the stability work out. And in the end, it is about a 22:1 glider - not particularly useful, and because of all the aluminum mass in the non-tapered wings, it can be a bit sporty to keep under control while rilling out after landing in gusty winds. Of course, it’s a taildragger….

Can you design an airplane that looks like an RV-12 but has long sailplane wings? Certainly - if you put a lot of design effort into it. But you can’t use much of the airplane “as is”, so you might as well start from scratch and get something that can actually soar.
 
Also, there might not be room inside the fuselage for the spar stub of a motorglider. It ain't going to happen, I expect.

Dave
 
I wish Van would take a second look at designing a mid-performance motor glider. He could design something similar to the Fournier RF4 in metal.
 

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There was a moment in time, late 1960s and early 1970s, where homebuilders were building moderate performance self launch gliders and having lots of fun, using fixed engines in a tractor or pusher configuration.

They'd self launch and fly on marginal lift days, when the pure gliders were on the ground waiting for better conditions. They'd make long cross countries like high performance pure sailplanes, by restarting their engines and climbing back up when moderate performance wasn't good enough. Oh well, iron thermal.

They even had a short lived magazine called "Motorgliding" that described all the fun they were having.

When the high performance Scheibe SF-27M came along it killed the interest in low cost moderate performance gliders, before their advantages were understood.

The Scheibe had a retractable engine that folded away (like most modern glass ships today) and for its day it was a high performance sailplane. It set a course for what we have today, self launching sailplanes with 50 to 1 performance. But they're $300,000 or more.

My point is have we missed the boat? Is there a lot of fun to be had with a moderate performance glider with a fixed engine - that has great handling characteristics that make it a great sport plane too?

If anyone could combine those traits and bring a kit to market it would be Richard VanGrunsven.
 
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Hmmm… longer wings? We had a set of rv12 wings at our airport and were wondering what would happen if we made a clipped wing 12 by chopping off one rib bay off of each panel 😅
 
You'd hurt the rate of climb and ruin the resale value, along with increasing the stall speed. A net loss all around.

Dave
 
PhatRV said:
Glider pilots are in a very small subset of pilots. Much like the small number tailwheel pilots compare to the overall pilot population. Those who buy prebuilt gliders are in a smaller subset of glider pilots, and those who build EAB gliders are in an even smaller subset. That means the market for a EAB motor glider is really small for a business case.
Click to expand...
Yes. I flew gliders in the midwest (Nebraska) all through college (all I could afford). Every flight requires a significant infrastructure, personnel and equipment, that goes well beyond just the plane and pilot. Even if the interest was there, it has to match up with availability.
 
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