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Old 02-08-2016, 01:49 PM
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blackshire blackshire is offline
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Default Tailless B/G idea

Hello All,

While looking up plans for old model rocket B/Gs (boost-gliders), I came across the plans for the SAI (Space Age Industries) Mini Bat kit (see: http://oldrocketplans.com/sai/saiK17/saiK17.htm ), which was a tailless boost-glider. (Of course, front motor boost-gliders which do *not* have V-tails, including the Mini Bat, have inverted vertical stabilizers so that the rocket motor exhaust won't impinge upon them.) Also:

Looking at the plans for the conventional (swept-wing, with conventional tail assemblies) Estes Falcon (see: http://www.airplanesandrockets.com/rockets/falcon.htm and http://www.spacemodeling.org/jimz/estes/k-13.pdf ) and the similar AMROCS Hawk (see: http://www.oldrocketplans.com/amroc.../amr101-150.htm ), it occurred to me that a tailless variant of such a boost-glider type is possible. By locating the swept wings farther back on the fuselage boom, or by using more sharply swept-back wings (or by doing both), a tailless front motor boost-glider having a planform like that of the tailless Northrop SM-62 Snark cruise missile (see: http://www.designation-systems.net/...app1/sm-62.html [this site also has material on the XSSM-A-3 Snark test vehicle]) could be built. In addition:

As well as being an effective tailless boost-glider (which could use either the motor-ejection method or a separating, streamer- or parachute-recovered motor pop-pod), a boost-glider of this design would eliminate or greatly reduce a problem of motor-ejecting front motor boost-gliders with conventional tail assemblies (which is discussed *here*: http://oldrocketforum.com/showthread.php?t=4843 ). The rearward-ejecting motor can break the model's tail boom just ahead of the horizontal stabilizer; this occurs because the tumbling spent motor case can strike the tail (which is often pitched up into the motor case's path by the model's reaction to the motor's ejection impulse, which causes a nose-down pitching moment--this happened to my father's Estes Falcon, whose tail boom he had to repair a few times). As well:

A contributory (or even primary) cause of tail boom breakage can also be the downward bending load that is suddenly imposed upon the boom by the upward-pitched horizontal stabilizer at ejection. In both cases, the tailless configuration could eliminate or reduce these stresses. Having no horizontal stabilizer, the rear end of the tailless model's tail boom presents a smaller "target" for the randomly-tumbling motor case to hit. The rear end of the model's tail boom is also not subjected to aerodynamically-caused bending stresses at motor ejection, because it has no horizontal stabilizer (those loads are distributed among the larger areas of the wings' outer portions).

I hope this information will be helpful.
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Old 02-08-2016, 02:14 PM
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I've always loved the elegant simplicity of tailless B/G's.

This kit used to be available from HD (Holverson Designs) and was called the silver hawk. I built this one several years ago, "The Vixen" hand colored the glider with markers.

Glided beautifully! If it caught a nice thermal it would soar well out of sight............unfortunately.
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Old 02-08-2016, 06:26 PM
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Quote:
Originally Posted by jeffyjeep
I've always loved the elegant simplicity of tailless B/G's.

This kit used to be available from HD (Holverson Designs) and was called the silver hawk. I built this one several years ago, "The Vixen" hand colored the glider with markers.

Glided beautifully! If it caught a nice thermal it would soar well out of sight............unfortunately.
Indeed--the Vixen was rather reminiscent of the Estes Nighthawk tailless B/G. I have the foam-wing, RTF version of Holverson Design's Zoomie tailless B/G, which ejects its motor (like Starlight's larger Sparrow kit).

A tailless boost-glider with a fuselage boom might be less wont to "hunt" in pitch than the short-coupled Zoomie and Sparrow, due to the length and mass of the fuselage boom. They glide well, but are more sensitive in pitch due to their short pitch moment arms; their "pitch hunting" can lose more altitude (and shorten the glide duration) on breezy days (although this isn't necessarily a bad thing, if the flying field is on the small side).
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Old 02-08-2016, 09:54 PM
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You're really talking about flying wings. Modern jets have winglets now both top and bottom. Near flying wings with a big tube holding bioflesh inside between them.

Jerry
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Old 02-09-2016, 06:53 AM
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Quote:
Originally Posted by Jerry Irvine
You're really talking about flying wings. Modern jets have winglets now both top and bottom. Near flying wings with a big tube holding bioflesh inside between them.

Jerry
No. A flying wing is an all-wing aircraft, while the term "tailless aircraft" (flying wings *are* tailless, of course, having no separate horizontal stabilizer) is applied to aircraft that have conventional fuselages, but have no horizontal stabilizer (some such aircraft are "borderline" cases, and are called both flying wings and tailless aircraft by different people). Also:

Straight-winged ("plank") and swept-winged flying wings and tailless aircraft (some people call planks--such as the Fauvel sailplanes--flying wings because their pod fuselages are very short, not much longer than the wing chord) are very short in relation to their wing spans (unless their wings are *very* sharply swept back, akin to a delta-winged aircraft's leading edge sweepback). Tailless aircraft like the SM-62 Snark and its XSSM-A-3 test vehicle (see: http://www.designation-systems.net/...app1/sm-62.html ) are longer in relation to their wing spans. The Navy's Regulus I cruise missile (see: http://www.designation-systems.net/dusrm/m-6.html ) was also laid out like this, having a normally-proportioned fuselage with a swept back vertical stabilizer--but no horizontal stabilizer--at its rear, with swept back wings mounted about halfway between the nose and the tail. A few drones and aerial targets also had/have similar configurations. Now:

This, and their normally-proportioned fuselages (and the mass distributed in their fuselages), give such tailless aircraft longer pitch (and yaw) moment arms, which should reduce the "hunting" in pitch that occurs (particularly in breezy conditions) in short flying wing and tailless aircraft. The boost-glider (and rocket glider) concept that I described above has a longer fuselage (of the boom type, as used in conventional-configuration boost-gliders such as the Falcon, Hawk, and Sky Slash II), which makes it similar in planform to the Snark, the XSSM-A-3, and the Regulus I.
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http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
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