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Old 07-02-2022, 06:34 PM
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blackshire blackshire is offline
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Default Boost-*Sailplane* designs (links)

Hello All,

Boost-Gliders (B/Gs) have always suffered from a problem--those that boost high, glide down rather than soar (unless a rather strong, steady wind aloft is about), and those that soar don't boost very high (because their sailplane-type proportions are pretty "draggy" for a rocket motor of reasonable total impulse to pull them aloft; more powerful motors tend to over-stress their long, flutter-prone wings). Also:

These opposing characteristics have resulted in the adoption of a practical, but un-ideal, solution: the "fair-weather" B/G (the sailplane-type ones, which boost best in dead-calm [or nearly so] conditions, not very high, but with a good glide) and the "foul-weather" B/G (the short, swept- or delta-winged, jet plane-like B/Gs that boost high, but don't soar unless there's a rather hefty wind loft), and:

NOTE: A long-burning, medium-total impulse motor *can* boost a sailplane-type "fair-weather" B/G to a respectably high altitude without endangering the glider's long, narrow-chord wings, but R/C (Radio-Control) is usually necessary in order to ensure a straight, near-vertical boost--BUT: I have found what may be a workable solution for F/F (Free-Flight, not requiring radio control) Boost-Sailplanes, boost-gliders that can soar *and* boost high. The following designs also happen to be scale sailplane subjects, although they need not be built that way (their nose sections could be simplified, rather than having cockpit canopies, if desired).

Inspired by the French designer of straight-winged tailless gliders and motor gliders, Charles Fauvel (see: http://www.nurflugel.com/Nurflugel/Fauvel/e_index.htm ), two American glider designers, Al Backstrom (see: http://www.nurflugel.com/Nurflugel/...e_backstrom.htm ) and Jim Marske (see: http://www.nurflugel.com/Nurflugel/Fauvel/e_marske.htm ), designed, built, and sold plans and/or kits for straight-winged, tailless sailplanes of their own; plus:

Several of their designs--Al Backstrom's Flying Plank and Super Plank (see: http://claudel.dopp.free.fr/Les_pla...trom_EPB-1C.htm [actor Larry Linville from M*A*S*H built a Super Plank: https://trekgrrl.wixsite.com/larrylinville/glider ]), and Jim Marske's XM-1A through XM-1D (these were four modified versions of his XM-1 sailplane, see: https://wikimili.com/en/Marske_XM-1 and https://en.wikipedia.org/wiki/Marske_XM-1 )--had constant-chord (rectangular planform) wings, which also had a single, wing root-to-wing tip airfoil section). As well:

These plank gliders of theirs (*all* full-size and model straight-winged tailless gliders are colloquially called "planks" due to their appearance) had/have rather short, low-aspect ratio (span-to-chord ratio) wings, yet they had/have sailplane-level L/D ratios (Lift/Drag ratio, also called the glide ratio; i.e., how many feet a sailplane will glide forward for every foot it sinks, when gliding in calm air).

A glider with a L/D ratio of 20 (or just below 20) or more can soar--gain altitude in normal-strength thermal, slope, or wave lift, that is--and is thus a sailplane (a glider is any unpowered aircraft, but a sailplane is a glider that can soar). The Backstrom Plank and Super Plank, and the Marske XM-1A, XM-1B, XM-1C, and XM-1D all had/have L/D ratios between 20:1 and 24:1. In addition:

These Backstrom and Marske designs flew with both dual wing tip-mounted vertical stabilizers and with a single, rear "pod" fuselage-mounted vertical stabilizer with a movable rudder (which offers another scale modeling option). Boost-Sailplane models of these short-winged sailplanes need not have the reflexed airfoil sections that the full-size ones used (although since their wings used/use a constant airfoil section from root-to-tip, building such models' wings [with appropriate model-size reflexed airfoil sections] using balsa-ribs/spars-and-tissue [or Silkspan, Monokote, or Solar-film covering]--or hotwire-cut foam wings [wth tissue/Silkspan/Monokote/Solar-film/laminated fiberglass & resin covering--construction wouldn't be difficult, if desired), BUT:

One need not go to such trouble to build boost-sailplanes such as these. As with the Estes Space Plane kit (see: http://www.spacemodeling.org/jimz/estes/k-03.pdf [and here is Chan Stevens' review of Semroc's "Retro-Repro" of this kit: https://www.rocketreviews.com/semro...an-stevens.html ]), rocket-boosted models of these Backstrom and Marske straight-winged tailless sailplanes could use flat sheet balsa wings, with nylon screw-adjustable elevons--*OR*, better, separate "central" elevators of this type--(with optional, similarly-adjustable ailerons, farther out toward the wings' tips). As with the full-size Backstrom and Marske plank sailplanes, these smaller elevators and ailerons would greatly reduce the wings' drag (the elevons on the Estes/Semroc Space Plane's swept wings extend fully across its wings' trailing edges). PLUS:

Models of the Backstrom and Marske sailplanes would glide with un-sanded, "square-edged" sheet balsa wings, but taking the time to at least round their leading edges would improve their gliding performance. The booster could be simply a long, finless rocket (optionally with nose ballast) with attachment points for two of the sailplane models on opposite sides of the rear of the rocket. A "single-sailplane booster" could be built the same way, except for the addition of one fin (or two fins, forming a 120-degree "V" angle between them, as viewed from the front or rear), with the sailplane model mounted opposite them, serving as a third fin. Having rather short, rather low-aspect ratio wings, more powerful motors could be used without risking wing flutter and failure, yet these tailless sailplane models would glide well, and they could also soar. PLUS:

Below are links to information on, and to drawings and pictures of, these Backstrom and Marske straight-winged, tailless sailplanes:

Straight-winged, Tailless Glider Designs
==============================

Backstrom Plank and Super Plank tailless glider variants:

https://en.wikipedia.org/wiki/Backs...-1_Flying_Plank

https://www.google.com/search?q=Bac...chrome&ie=UTF-8

https://www.google.com/search?rlz=1...0&bih=789&dpr=1

http://www.nurflugel.com/Nurflugel/...e_backstrom.htm

http://claudel.dopp.free.fr/Les_pla...trom_EPB-1C.htm


Marske XM-1, XM-1C, and XM-1D tailless glider variants:

https://wikimili.com/en/Marske_XM-1

https://en.wikipedia.org/wiki/Marske_XM-1

https://www.google.com/search?q=Mar...sclient=gws-wiz

http://detlefkolletzki.bplaced.net/...htm#Marske_XM_1

https://www.rcgroups.com/forums/sho...ond-time-around


Marske Pioneer I - IV tailless glider variants (Included for completeness' sake; the Pioneer I - IV have more complex wing shapes):

http://all-aero.com/index.php/60-gl...craft-pioneer-i

https://marskeaircraft.com/flying-wing-history

https://kollmanwings.com/Pioneer_4.html

https://en.wikipedia.org/wiki/Marske_Pioneer

http://www.nurflugel.com/Nurflugel/Fauvel/e_marske.htm

https://www.google.com/search?q=Mar...chrome&ie=UTF-8


I hope this information will be useful, and Happy Independence Day, everyone!!!
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Old 07-03-2022, 12:45 PM
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If that design of glider were to stall, it would, most likely, start tumbling "end over end". I believe that it would be virtually impossible to recover from that situation.

Dave F.
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Old 07-03-2022, 07:44 PM
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Originally Posted by Ez2cDave
If that design of glider were to stall, it would, most likely, start tumbling "end over end". I believe that it would be virtually impossible to recover from that situation.

Dave F.
Surprisingly, they are stall- and spin-proof. Charles Fauvel first noticed those attributes with his plank sailplanes (see: http://www.nurflugel.com/Nurflugel/...ing%20 formula. ) Al Backstrom and Jim Marske also found their straight-winged tailless sailplanes to not be stall-able or spin-able (they both tried--vigorously--to make their gliders stall and spin, to no avail), and:

In fact, Jim Marske became interested in plank gliders after he had a potentially fatal accident in a Schweizer SGU 1-19 sailplane (see: https://en.wikipedia.org/wiki/Schweizer_SGU_1-19 ), as a teenager. (*Here* https://www.youtube.com/results?search_query=Jim+Marske is a series of brief videos about his life story--it's very interesting; as a kid, he saw a DC-3 [Army Air Corps C-47] towing a captured German Me 163 Komet rocket plane over the family's farm, heading for Wright Field [the home of ATIC, the Air Technical Intelligence Center, where Project Blue Book was later based]--he describes this in the video called "In the Beginning.") Also:

In the videos "Jim Marske Flying Wings 2" [and 3], he describes the Schweizer 1-19 accident, and how it got him into plank-type tailless gliders. He had been flying the 1-19 in a tail-heavy condition, got it into a flat spin, and banged down hard enough to fracture his back and skull; fortunately, the surgery was successful, and he recovered. While he was recovering in the hospital, a friend of his brought him material on Charles Fauvel's plank gliders, and he first thought the photographs were faked--he said, "There's no way that thing can fly!" BUT:

After he got home to complete his convalescence, he made several small hand-launched model gliders--including of the Fauvels--to amuse himself. To his surprise, he found that when he launched the tailless Fauvel glider models into the severely-angled slope lift created by the wind passing up the wall of their barn and over its roof, they refused to stall, unlike the conventionally-configured (with tails) model gliders that he tossed into the "barn slope lift"; Fauvel had been right. As well:

When he built his XM-1A plank-type glider (originally with dual wing tip fins; he removed them and installed the single rear centerline tail fin later, on the XM-1C and-1D variants [they were all the same glider, not multiple ones], although the original wing tip fins worked fine; the centerline fin simply worked better), he tried to stall it and spin it, and it just wouldn't do either. When he tried to stall it (or dived to gain speed, then pulled up into a vertical climb, to do a tail slide [which the Fauvels also wouldn't/won't do]), the glider's nose just quickly dropped, and it would resume level flight, and:

Trying to spin the XM-1 (as with the Fauvel and Backstrom plank gliders) only produced a loose spiral turn, which the glider would straighten itself out of. Deliberately holding the controls over as far as possible to try to spin it just caused it to lose airspeed, drop the nose, then level out again, in a sort of "stair-step" pattern. They're quite stable; in fact, in one of the videos, Jim Marske says that he is afraid to fly conventional aircraft with tails, because there are so many ways they can end up in stalls, spins, flat spins, and inverted flat spins, even with highly-experienced pilots at the controls (an unexpected gust of wind, especially at low altitude and slow airspeed, can get such conventional-configuration planes and gliders into trouble). Now:

A plank-type tailless glider or airplane (Fauvel and others designed/design such motor gliders and light planes [Al Backstrom also designed such an airplane]) *can* "pancake" onto the ground if its airspeed drops too low (without enough altitude to re-gain adequate speed), but ^any^ heavier-than-air flying machine--even a helicopter or a gyroplane, or an autogyro--has to have appropriately-rapid airflow over its lifting surfaces, or it just won't fly. Planks won't, however, suddenly drop a wing, as a stalling conventional plane or glider does (neither will a delta-winged aircraft; while deltas can stall, they "mush" downward, without suddenly dropping a wing, which is also safer when trying to re-gain adequate flying speed). Canard ("horizontal tail-first") aircraft and gliders also won't spin; while they *can* be made to stall, it requires great, intentional effort to make them stall, and they give very early warning of an approaching stall, long before one is anywhere near the danger zone (as Burt Rutan had Ben Kocivar--then writing for Popular Science--demonstrate for himself, when he and Ben flew one of Rutan's VariEze canard homebuilt light planes; Ben found that the forward canard stalled first, then dropped the VariEze's nose back down, resuming level flight).
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Last edited by blackshire : 07-03-2022 at 08:01 PM.
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Old 07-03-2022, 08:18 PM
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Quote:
Originally Posted by blackshire
Surprisingly, they are stall- and spin-proof. Charles Fauvel first noticed those attributes with his plank sailplanes (see: http://www.nurflugel.com/Nurflugel/...ing%20 formula. ) Al Backstrom and Jim Marske also found their straight-winged tailless sailplanes to not be stall-able or spin-able (they both tried--vigorously--to make their gliders stall and spin, to no avail), and:


Hmm . . . I bet that, if they put the CG as far aft as possible ( behind the CP ), by adding rear ballast to exceed the pilot's weight , they would stall.

In that condition, they would be "dynamicically unstable", from the "get-go" !

https://www.differencebetween.com/d...namic-stability

Dave F.
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Old 07-03-2022, 11:18 PM
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Originally Posted by Ez2cDave
Hmm . . . I bet that, if they put the CG as far aft as possible ( behind the CP ), by adding rear ballast to exceed the pilot's weight , they would stall.

In that condition, they would be "dynamicically unstable", from the "get-go" !

https://www.differencebetween.com/d...namic-stability

Dave F.
Of course they would stall if you moved the CG as far back as possible (I even have the NASA Langley Research Center [LaRC] book--it's boxed up at the moment; I think its title is "An Introduction to the Aerodynamics of Flight"--from which that website's drawings illustrating static and dynamic stability came), but why would anyone ^want^ to do that, with either a model or a full-size sailplane or airplane? With rocket-boosted models of them (or *any* models of them, for that matter), the best CG point in the CG range (which is narrower than that of a conventional, tailed glider, but isn't just a "single point range," either) would be easy to find--even if one didn't have the locations from the full-size ones' plans--just by doing hand launches, and moving the ballast as needed until one got the longest glide, and:

Marske's point was simply that even a properly-balanced (with its CG in the right range) conventional-configuration glider or powered airplane can *still* stall and spin, while a plank-type tailless one with a properly-located CG can't (which he, Fauvel, Backstrom, and other pilots of such plank-type sailplanes, motor gliders, and airplanes--plus countless F/F and R/C modelers who've built and flown such models--have proved). As well:

Jack Lambie, a highly experienced sailplane pilot who once owned what was--then (the late 1950s to early 1960s)--the *only* Fauvel AV-36 operating in the United States (that's *this* http://www.nurflugel.com/Nurflugel/Fauvel/e_AV36.htm one, and most of ^these^ http://www.nurflugel.com/Nurflugel/...ing%20 formula. [except for the two-seat, AV-22 http://www.nurflugel.com/Nurflugel/Fauvel/e_AV22.htm <also made as the AV-221 http://www.nurflugel.com/Nurflugel/Fauvel/e_AV221.htm & AV-222 http://www.nurflugel.com/Nurflugel/Fauvel/e_AV222.htm motor gliders> on the right]), tried countless times to do "tailless tail-slides" with his AV-36, and it just wouldn't do it; the nose would drop, and it would resume level flight. (Marske's Schweizer 1-19 flat spin accident occurred because he didn't know, at the time, that it was tail-heavy [he had just started taking glider flying lessons at the time]; later, he learned that even properly-balanced conventional aircraft can stall and spin, but that properly-balanced plank-type tailless ones won't stall or spin.)
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Old 07-03-2022, 11:45 PM
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Quote:
Originally Posted by blackshire
Of course they would stall if you moved the CG as far back as possible (I even have the NASA Langley Research Center [LaRC] book--it's boxed up at the moment; I think its title is "An Introduction to the Aerodynamics of Flight"--from which that website's drawings illustrating static and dynamic stability came), but why would anyone ^want^ to do that, with either a model or a full-size sailplane or airplane?


I see them as "stall-resistant", rather than "stall-proof". To me, "stall-proof" implies that they can't be stalled, under any circumstances. Their "stall-resistance", however, is very interesting !

Dave F.
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Old 07-03-2022, 11:38 PM
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Quote:
Originally Posted by Ez2cDave
Hmm . . . I bet that, if they put the CG as far aft as possible ( behind the CP ), by adding rear ballast to exceed the pilot's weight , they would stall.

In that condition, they would be "dynamicically unstable", from the "get-go" !

https://www.differencebetween.com/d...namic-stability

Dave F.
Here (see: https://www.google.com/search?q=BKB...sclient=gws-wiz ) is a tailless, aerobatic sailplane that was designed to--among other things--tumble end-over-end, the Brochocki BKB-1. R/C model plans and kits of the BKB-1 are also available (see: https://www.google.com/search?q=Bro...sclient=gws-wiz ), and:

It wasn't a plank, as it had swept-back, constant-chord wings. The BKB-1 also had a good glide ratio, 30:1 (see: https://en.wikipedia.org/wiki/Brochocki_BKB-1 ), despite having relatively short, low aspect ratio wings--which would also make it a good boost-sailplane model, whose booster could safely use high-impulse motors.
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