105 pound HAIG Minibat

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BDD

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The airfoil does not create stability in a flying wing or any other type of airplane. Stability comes from the relative placement of the neutral point (mostly due to planform) and the CG. The whole "stable airfoil" thing you see on all the R/C sites is a complete myth, reflecting a poor understanding of what's really going on. It's the difference between stability and trim.

Designing a flying wing is absolutely no different than designing any other kind of airplane. Just harder, because you have to get the wing to also do all the functions that would've been performed by the tail that's not there. Airplanes are a bunch of compromises flying in formation. Flying wings just require more - and harder - compromises.
The way I've always seen it is that for a practical tailless arrangement that is stable, an airfoil with a positive pitching moment (1), or a wing with enough washout for a net positive pitching moment (2) or a swept wing arrangement with either a reflex airfoil (as in the first option above) or enough (less this time because of the moment arm from the wing sweep) washout to achieve a net positive pitching moment (3)......is a prerequisite, along with the proper relationship of center of gravity and neutral point (to balance the positive pitching moment) for a stable flying wing in pitch.

As a prerequisite I see it as a rather important part of the total. Without it, the wing doesn't respond to pitch changes the way you need it to for pitch stability.

Calling it a "stable airfoil" is probably a misnomer when viewed literally. By itself, positive pitching moment is unstable too but it is a prerequisite for pitch stability in combination with the C.G./N.A. relationship.
 
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topspeed100

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Yeah, sorry, I'm not usually such a bad influence.



That's for sure. Sweep in either direction demands a heavier spar but forward sweep is worse than aft sweep because torsion due to sweep tends to be self amplifying in FSW whereas in aft swept wings the torsion tends to damp itself. The designer can work with this twisting tendency of aft swept wings to make the spar more effective at resisting trosion without adding more material by proper positioning. It's called "desweeping".
I tought so.
 

WonderousMountain

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I think larry's personal unmotorized version may have weighed that. One had used alternative structure. There were wingtip extensions that may have gotten into the 105 weight. Homebuilts rarely hit their mark.
 

Aircar

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I wonder why he didn't use struts and allow himself some more span and some decent performance? The basic formula is similar to the Genesis and a couple of very early sailplanes.
The Quo Vadis of Akaflieg Darmstadt -I think - was more strongly swept forward than current(tailed) two seat gliders to get the second pilot near enough to the CG --forward sweep is not conducive to directional stability but that is not neccesarily a problem when thermalling a glider (requiring the pilot to fight it to make rapid changes of turn rate ) They named it Quo Vadis (lat, whither goest thou ? as the medieval English translation but in modern English more like "TURN YOU BLOODY**##%$## " since it would not apparently "answer the controls" to everyone's satisfaction.

There seems to be a lack of data and rules of thumb in regard to lateral directional control and stability in "tailless" aircraft --or rather those having at least vertical tails but very short centre bodies --the Marske and Fauvel as the best examples . There was a reference to a paper in the mid 1960s presented at a Euromech conference by a Spanish designer (I can look up the name in old OSTIV papers where he did papers on modifying the mean lines of laminar airfoils for tailless or shorttailed aircraft ) who asked whether there might be an optimum layout with a very short fuselage and tail rather than the 'all or nothing' of the extremely long tailboomed conventional sailplane or the one with no tail at all --seems sensible to think it might . He presented several speculative designs now appearing in the likes of the Genesis and SGS1 (NZ Gregg Mapheson -wrong spelling but close ) --the trials and tribulations of the only two really unconventional Akaflieg designs of more recent times --the SB 13 and the FS 26 -tailless and "semi tailess" respectively stand in contrast to the apparent success of the Genesis but none have made a mark in soaring at large.

I saw a Haig Eaglet under construction and it was doll like in fragility and the Gliding federation would not approve the design --not that that was a conclusive judgement but it would have been too delicate for outlanding or flying off some of the rough barely grassed strips we use and gravel damage to the prop would be instant .

Focussing on getting the lowest weight belongs in the Guiness book of records (as I said elsewhere) and is an unhealthy 'metric' with very little relevance. --if it is gotten by carbon fibre and autoclaving then it has nothing to do with cheap for example.
 

WonderousMountain

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I was able to view a Genesis i? at the sailplane meetup. Very attractive design, with the trim wing. However finish was fairly wavy, which wasn't a structural issue due to marske's focus on strong spars. Somewhat disappointing but it was said to be stable and fun to fly, with good performance on low lift days. Would have asked more questions if I understood it's far reaching philosophy.

The Haig wasn't cheap with kevlar, carbon fiber, and other specialty fabrics and weaves ect. The 6g structure remains an accomplishment. The tips had extensions for greater soaring performance. What it lacked was logic. Especially in the airfoil, but also other parts that weren't thought out. The engine was an afterthought, and weight shift without weight shift systems is suspect. Pilot weight could drastically affect control.

Topspeed, The Fauvel designs represent a great start for flying wing and Marskes has mode over thirty flyable planes, with good flight structures.
Forward sweep is creates a positive feedback system, but can be aero-elastically tailored for performance, and flown safely as long as critical speed is not approached. This sounds bad but it's not much different than aileron divergence. However, I would design for stiffness primarily.

Perhaps some 1.5 chord tail arm experiments are in order. You have in RC's handy?
 

topspeed100

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I saw a Haig Eaglet under construction and it was doll like in fragility and the Gliding federation would not approve the design --not that that was a conclusive judgement but it would have been too delicate for outlanding or flying off some of the rough barely grassed strips we use and gravel damage to the prop would be instant .

Focussing on getting the lowest weight belongs in the Guiness book of records (as I said elsewhere) and is an unhealthy 'metric' with very little relevance. --if it is gotten by carbon fibre and autoclaving then it has nothing to do with cheap for example.
I also think the biggest dangers in making a very efficient affordable aeroplane is the suspicion that this will not be safe. It will also be used by any competitor to hammer it down as no good.

I had totally forgotten Haig reached 36 kilos...Whing Ding II was 45 kilos with 10 hp McCulloch. Elfe was 43 kilos but was a normal looking glider. Twin engine Cri Cri proto was a heavy with 64 kilos weight.
 

WonderousMountain

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Well, it could be that those who came before you have frequently failed. Sure, there's a half dozen or so successful birds under 50-60Kg, but there's a good dozen or so that flew up but didn't come down in the same piece.

Oddly if we had never gotten away from wood structures planes would likely be half the weight. The reason being the density of wood is more conducive to lighter structures. Sandwich panels and optimal stressed skin designs can meet it, but it's far easier to add some layers and make a heavier plane overall. Also, aluminum adds up quick, and hyper thin structure isn't dent resistant or easy to assemble.

Your 50Kg mark can be done, but know that what you're doing is a deliberate act of forward engineering, and not just another afford-a-plane attempt.
 

topspeed100

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Anything at 45-65 kg is doable..it all depends of the details and chosen G load limits and engine ( anything from 3-40 kilos !! ).

The other fact is that the plane will be small. There lies another trap...if it ( when it is ) short it is always blamed to be short coupled...even all mathematical and known factors were met in aeroplane stability.
 

ultralajt

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:) Al flying wings are "short coupled".. flying planks the most.

Regarding engine at MiniBat, it was chainsaw engine intended as "sustained"... No start was possible with that engine. It was there just to provide some help to prolong glide.

Mitja
 

WonderousMountain

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Yes, small planes are accused of being short. That they are. Really big planes hand differently, extra small ones do also. Some are just more comfortable with larger size-their loss.

Build your plane!
 

topspeed100

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:) Al flying wings are "short coupled".. flying planks the most.

Regarding engine at MiniBat, it was chainsaw engine intended as "sustained"... No start was possible with that engine. It was there just to provide some help to prolong glide.

Mitja
Swift at 46 kg weight still looks very well balanced and not so short coupled as it looks short.
 

topspeed100

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Yes, small planes are accused of being short. That they are. Really big planes hand differently, extra small ones do also. Some are just more comfortable with larger size-their loss.

Build your plane!
Since you cannot see my plane I can inform that it is 100 mm shorter than a BD-5...but it has 1 metre ( 3,4 ft ) more moment arm between wing and elevator mac 25% chord point. It is 41 % more ! Now when you do proper control geometrics...you will never know you are flying a smaller plane.
 

Roy

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Althrough I've never flown the HAIG Minibat I own the crashed factory demo and all the vacuum molds to produce it. I purchased the molds and rights from Larry Haig in the late 70's with the intent of redesigning it with a canard wing. I ran into the same problems as all fiberglas kit manufacturers "politics" concerning fiberglas manufacturing facility. I'm considering selling the molds to an amusement rides company. I also own Haig's AmEagle factory flagship (not airworthy) which would make a great amusement ride as well. I could design and program the ride. I've designed and built precision manufacturing equipment all over the world.
 

ultralajt

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Althrough I've never flown the HAIG Minibat I own the crashed factory demo and all the vacuum molds to produce it. I purchased the molds and rights from Larry Haig in the late 70's with the intent of redesigning it with a canard wing. I ran into the same problems as all fiberglas kit manufacturers "politics" concerning fiberglas manufacturing facility. I'm considering selling the molds to an amusement rides company. I also own Haig's AmEagle factory flagship (not airworthy) which would make a great amusement ride as well. I could design and program the ride. I've designed and built precision manufacturing equipment all over the world.
Hey Roy, welcome to HBA forum!

I was researching the AM Eaglet developement history from various sources found on the Internet.

I would be very happy if you could share with me(us) photos of your AM Eaglet sample. I am very interested in technical details.

With best regards!

Mitja
 

plncraze

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On the subject of an "amusement ride" find the picture of the Minibat mounted on the front of the Dodge Charger so a neophyte pilot could get a feel for the airplane before going in the air alone.
 

renxxx1981

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Corrections and updates indeed. The Minibat was a neat little thing, but the airfoil was just bad and the wing construction was just horrific. Didn't last on the market very long.
Topaz , I really trust your verdict but could you please give me an insight about wing contruction and some other details you are aware of? I'm attracted by this little sailplane?
 

Topaz

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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.
 
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