105 pound HAIG Minibat

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Victor Bravo

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The Minibat concept wasn't necessarily bad, it just needed better execution.
It would seem that the confluence of more recent high performance hang gliders, Part 103 true sailplanes like the Sparrowhawk, and Marske's Monarch/Pioneer series might essentially render the Minibat concept obsolete???

Meaning... if you created an aerodynamically safe and structurally sound version of the Minibat, what would it do for you that other current designs could not do better? I would guess the Monarch would soar better and slower in light lift, the Sparrowhawk would run away from it in a race, and the ATOS HG would fold up into a smaller package.
 

Topaz

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It would seem that the confluence of more recent high performance hang gliders, Part 103 true sailplanes like the Sparrowhawk, and Marske's Monarch/Pioneer series might essentially render the Minibat concept obsolete???

Meaning... if you created an aerodynamically safe and structurally sound version of the Minibat, what would it do for you that other current designs could not do better? I would guess the Monarch would soar better and slower in light lift, the Sparrowhawk would run away from it in a race, and the ATOS HG would fold up into a smaller package.
Couple of things. For one, it would fold into a smaller package than the Monarch, but have close to the same performance, better than the ATOS for ridge-soaring, IMHO.

And the MiniBat has something none of the others have: The ability to cut off a relatively low tow and still climb on its own up to altitude, or explore dubious lift without worrying about landing out. It was part of a brief fad of "sustainer" gliders, where it had just enough motor to climb out of sink or do its own "save", but not so big and heavy a motor that it could self-launch. The market ultimately decided against sustainer gliders - most pilots just figured, if you have a motor at all, just go all the way and self-launch - but for very inexpensive recreational soaring, the concept still has merit. Not that being a "sustainer" glider is, in any way, unique to the MiniBat, but this airplane had a particularly neat engine and prop installation.

I'm not recommending it, just saying that, if the design were "fixed", it represents another viable set of design/performance priorities that might appeal to someone. The Moni was probably a better overall set of choices, but then you already know that.
 

Norman

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Hmm... any?

I am specially interested in Minibat wing structure. Any recemblence with AM Eagle wing or it was some different detail approach?
I am courious just as want to know how as made and maybe lear something.. in order not to do such way or even find out something interested.

O.K. I made some searching and find out this article, where:

Construction
Minibat construction was unique for the time period. Most of the 18 major parts consist of a PVC
core with Þberglass on both sides and formed in a female mold. A few dozen hardware parts are
sufÞcient to complete the aircraft. Despite the extent of molding and preformed parts, the FAA
determined that the aircraft is 64.5% fabricated by the builder.
The wing consists of molded upper and lower shells of E-glass and foam, a spar using
unidirectional S-glass for the caps, and molded shear webs of glass and foam. The shells are held
together at the leading edge by J-joint, and at the trailing edge by the molded rear spar. The
elevators and ailerons are made from molded glass upper and lower surfaces over glass and foam
ribs. The wing halves attach internally at the centerline with pins. Additional wing panels of about
four foot length became available to increase the wing span and decrease the wing loading. These
extensions substantially improved gliding performance.
The fuselage is built in the same way as the wings, except there is no spar cap. The outer skin
carries the bending loads and the inner skin carries the torsional loads. Reinforcement is provided
in the area of the landing gear, tail skid, etc. Besides a J-joint on the outside, the fuselage is tied
together on the inside by the seat, armrests and keel.
The Þn and rudder are constructed like the ailerons and elevators Ñ glass skins are placed over
foam ribs.
I just read this thread again and noticed that he used sandwich construction consisting of E-glass with PVC cores. PVC foam is good core material but E-glass is not a great choice for the skins. S-glass is about 30% stronger than E-glass and a bit stiffer so a sandwich using S-glass will be a lot stronger and stiffer than one using E-glass for the same weight. The "E" in E-glass stands for "electronic", it was formulated to have better insulating properties than S-glass for fabrication of circuit boards and it should be left to that use. Of course, if you're not on a budget, you could use carbon fiber and end up with an even stiffer wing at a lower weight. Structural glass does have one advantage over carbon though: it is more impact resistant.

Apparently he used a naked block of foam for the webbing of the main spar. This is just weird. It may have been adequate but it just doesn't look good. A little bit of fiberglass would tie the spar caps together much more solidly than a big block of foam.

Be extremely careful with Liebeck airfoils. The turbulent rooftop theory that Liebeck was working on yielded shapes with very high lift and sometimes low drag at high lift but not very impressive performance at any other speed. Some of them were better than others but if you don't have wind tunnel data for the specific one that Haig used on the Minibat you can't draw any conclusions about the wing's flight properties.
 

renxxx1981

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Oy. It's been years since I made that post. My recollection is that the wing structure was overly reliant upon foam to transmit primary loads near the spars, and that at least the original shear web was nothing but unsupported foam. Both are no-no's in composite structural design, but you have to remember that the Minibat was born during the "Wild West" period of homebuilt composites, when it seemed like everyone was coming out with a new design every other week, and a lot of them were not really professionally engineered. I have a book from the period that has a cross-section view of the Minibat wing, but I moved a few months ago and that book is in a box here... "somewhere". :ponder: As I recall, the airfoil selection tended to stall prematurely if dirty or wet. It also wasn't much of a sailplane airfoil, in terms of drag.

The Minibat concept wasn't necessarily bad, it just needed better execution. An entirely new structural and airfoil design for the wings would be where I'd start. Given the structural deficiencies in the wing, taking a look at the fuselage structure wouldn't be out of line, either. The high trim drag from the low sweep, and induced drag penalty from it being tailless, mean it won't ever be a great thermalling sailplane, but it'd be a great little ridge soarer if the local geography is suitable.
Thanks for the Comprehensive replies to all, as Always here on the forum. My conclusion is that is better to put some effort in some other projects even though the Minibat still owns some attractive characteristics... If Topaz manages to find the picture of the wing' cross section would be great since nothing like that is available on the web and would be insiprational for some of us.
 

Topaz

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Thanks for the Comprehensive replies to all, as Always here on the forum. My conclusion is that is better to put some effort in some other projects even though the Minibat still owns some attractive characteristics... If Topaz manages to find the picture of the wing' cross section would be great since nothing like that is available on the web and would be insiprational for some of us.
Well, I dug through a couple of the moving boxes that weren't in storage and found the book for which I was looking, Michael Markowski's Ultralight Aircraft: The Basic Handbook of Ultralight Aviation. The book was published in 1981, at the very height of the Wild-West-like "Ultralight boom", before the '60 Minutes' exposé and the drafting of FAR Part 103. As such, and as was typical of the time, it's a pretty "optimistic" view of what ultralight aviation was then - basically anything that could be foot-launched. Since the Minibat can't be foot-launched, I'm not sure why it's included, but it is.

Here is the relevant page, showing a representative cross-section of the wing. Note the exclusive use of Kevlar as the reinforcement part of the composite structure (not the best choice of material, by a country mile), the extensive no-core section at the leading edge, and the foam-only shear web. The latter gives me the willies just thinking about it. The airfoil is clearly one of the Liebeck low-speed series as Norman was saying, and his points there are right on. Best to consider this image as a good example of how NOT to do it right. The page also contains manufacturer-claimed performance numbers for the glider.

Scanned_20171023-1422.jpg

EDIT: For those who don't know the Minibat, here's a three-view from the same source. You may be cool, but you're not as cooooool as Cool Late-Seventies Dude! :gig:

IMG_20171023_144604.jpg

IMHO, it's not a bad concept, just poor execution, born out of all the misinformation and over-enthusiasm of the period. I think the actual molds are useless at this point in time, especially those for the wings. With a professional redesign, the Minibat is probably salvageable, I think, if it's something you really want.
 
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Norman

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The spar web call-out on the drawing does say "foam core" so apparently the rumor of the simple foam web was overstated but then it shows that core-less leading edge. I don't see the point in dropping the thickness down like that. It doesn't save much weight but it sacrifices some stiffness and impact resistance. The airfoil looks like it might have been the L1003 which has a fairly wide laminar bucket above CL=0.4 at Reynolds numbers above 500,000 but at lower Re it gets pretty draggy. Not the best choice for a tiny glider.
 

Topaz

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The spar web call-out on the drawing does say "foam core" so apparently the rumor of the simple foam web was overstated...
Possibly but, since the face sheeting material is specifically called out everywhere else in the diagram and there's none here, and since I've been told the shear web was foam-only, I interpret that as meaning "foam only" despite the use of the word "core". Perhaps I'm wrong, but this interpretation matches what I've heard elsewhere.

Completely agree on everything else.
 

Victor Bravo

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Ahhh... I didn't realize we were talking about the powered sustainer version of the Minibat. Yes it did have an interesting propeller installation. But the concept that it could get off of a low tow and then manage to get into lift is based on the presence of that engine, to compensate for the poor soaring performance. The Monarch and ATOS can get off of a 300 foot car tow and do that type of flying without an engine. Hell, I'd bet that the Sparrowhawk can do that, and I have heard stories about guys routinely doing that in a Ka-6 for that matter.

A Minibat fuselage, hung under a Carbon Monarch wing... now that would be a very worthwhile concept to pursue.
 

renxxx1981

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Thank guys , that's fantastic! I guess there is nothing like that published on the web.. That's a great research work! As a completion of the topic here you get a couple of pics with extended wing tipsminibat--extensions-dj.jpgminibat--extensions-dj-.jpg
 

b7gwap

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Aft sweep gives natural yaw damping, does forward sweep do the opposite? It does have a pretty big vertical tail.
 

Hot Wings

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Condolences to the purchaser. :confused:
I've discovered how much work just the plans for a proven and certified flying wing have been. One would have to be crazy or a certified masochist to go down that path.:eek:

The basic concept is sound but it needs a full development program to make it viable.

If the molds are still usable they might make interesting yard art for aviation related places/businesses?
 

Topaz

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About the only thing "viable" on the Minibat is the fuselage and vertical tail outer mold line. The wing airfoil and structure would need to be entirely redesigned from scratch. It's a neat little design, but reviving it is going to be a lot of work, even compared to the AV-36.
 

Topaz

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proppastie

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the molds for the outer mold line of the pod could be adapted to any design.....lot of work saved if you like the shape.
 

jedi

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the molds for the outer mold line of the pod could be adapted to any design.....lot of work saved if you like the shape.
There appears to be reasonable interest in a small, light, simple, (as in fast build) flying wing. As a design exercise and a configuration study, what would it take to convert the Mini Bat design into an ultralight flying wing.
 
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