Moni Motorglider

[Little Scrapper]

Anyone here know anything about these? Did they fly well? Why didn't this model succeed?

According to Wikipedia they made less than 400 of these kits. Usually there's one for sale on barnstormers for what seems to be pretty reasonable. Curious is all.

 

[Topaz]

One of my favorite little airplanes. This is a bit on the way-back meter, but my recollection of the time was that the Moni suffered the fate of nearly all motorgliders: Not fast enough for power-plane pilots, not "pure" enough for sailplane pilots, and in its original form it was really best at ridge-soaring. If you don't have a ridge nearby, well.... For a short time at the beginning it was offered only with the mono-wheel main gear, which put off a lot of the pilots who were looking at it anyway. There was a "short wing" version for power-plane pilots that had conventional gear that came out later in the production run for the kits, and while I believe that ended up being the best-selling model, it never did make a big splash. The weight of the gear cut strongly into the useful load, and added enough drag to reduce the performance. If Wiki is correct, the original version useful load was only 240 lbs to begin with. I dimly recollect a long-wing "enhanced soaring" model, but I'm not sure that got beyond the prototype stage.

I think there may have been some issue with the KFM engine, late in the game. I don't recall what it was. May have been that it was discontinued?

Pireps I read of the airplane said it was typical of small single-seat homebuilts, with light controls and simplifications compared to type-certificated aircraft, but that it flew well for what it was, and got decent performance out of the original 30hp engine. I remember one power-pilot complaint about the seating position - sailplane-like and too "laid back" for his taste. A lot of people liked the kit. Very simple, especially for the time.

Another factor is that this was full-bloom "Rutan-time", and the Quickie 1 was considered a direct competitor by most, even though it couldn't soar at all. The Quickie, by virtue of its looks and association with Rutan, got a lot more press.

The Moni is the figurative and literal ancestor of the Sonex family. John Monnett designed both.

 

[Victor Bravo]

If Topaz will not be offended by the correction, Pete Buck designed the Sonex, intentionally keeping the lines and styling of the earlier Moni. Monnett was the designer of record on the Moni, but Pete told me he had built a lot of the first Moni while he was an apprentice or shop hand. So both airplanes have DNA in them from Pete Buck and John Monnett.

The KFM engines had a habit of twisting the front of the crankshaft off in flight. They eventually came out with a little belt drive that solved that as well as allowing a decent size prop. The original Moni had a 25HP KFM engine with something like a 27 inch propeller diameter!

Performance was excellent for an efficient sport airplane but a poor sailplane.

 

[Little Scrapper]

What made it a poor sailplane?

You'll have to excuse my ignorance I have zero experience with this part of aviation. I find it really interesting though.

 

[Turd Ferguson]

The Moni is a sibling of the monex racer, which I believe came first (where is Ed F.?) The lineage is obvious.

 

[Topaz]

If Topaz will not be offended by the correction, Pete Buck designed the Sonex, ...

Really? I take it Pete Buck is an employee of the Sonex company, started by John Monnett? The Wikipedia article implies that Monnett designed the Sonex in response to a customer request, and that has always been my understanding as well. If Pete was the in-house designer, working under Monnett, then that's understandable.

What made it a poor sailplane? ...

Not really enough span, wing loading rather high. Whole whack of draggy things on the nose, including the big wooden plank someone bolted cross-wise there, that neither feathers nor folds. Sharp corners on the fuselage bottom, meaning vortices shed all over the place at low speeds, as are used in thermaling.

My understanding is, from someone that owned one, that if you've got a nice breezy day it's a great ridge-soaring ship. Light and nimble. A little fast if there's a lot of other traffic on the ridge, but okay if you keep ahead of the airplane and your eyes ahead.

Ridge soaring in a conventional sailplane (jump to 1:45 for the better, in-cockpit, view):

[video=youtube;4livnFiVhWE]https://www.youtube.com/watch?v=4livnFiVhWE[/video]

 

[Victor Bravo]

Really? I take it Pete Buck is an employee of the Sonex company, started by John Monnett?

Pete is the guy with the yellow Sonex Xenos motorized glider I ithink I ntroduced you to up in Tehachapi. I believe he started as a shop hand or underling at Monnett's shop years ago. Then he went off to engineering school, became a really good aero engineer, and reporteedly worked at some strange place with a picture of a skunk on the building. Somewhere in the middle of all this, John Monnett's old idea of a two-place Moni became a viable project, and I believe Pete did the engineering on it. The Sonex is more or less that airplane, a wider Moni with Monnett's VW engine conversion. I remember reading somewhere that Monnett wanted to do the long wing version first but the market dictated a clip-wing sportplane version first. The Sonex is the clip wing version, and the Xenos is the "soaring" long wing version.

This work may have been done under contract to Monnett/Sonex, or as a quick "side job" during a time when he was not busy doing the design work on the (redacted) for (redacted).

When the Sonex was just coming out, since he lived and worked near Los Angeles at (redacted) Pete came and made a presentation about the new Sonex at our LA area EAA chapter meeting.

I am not sure what the current official relationship is between Pete and Sonex, since I believe he is now retired from (redacted). But I also do believe that there is a close personal connection between Pete and Monnett/Sonex. All of this may very well be explained better and more accurately in the book about Monnett/Sonex history, but I have not yet read that book. Someone familiar with the book might chime in here and verify/correct any of this.

 

[Topaz]

Awesome. I learned something new today. Thanks!

 

[Turd Ferguson]

Someone familiar with the book might chime in here and verify/correct any of this.

If you are referring to the Jim Cunningham book I have read it and believe your account is fairly accurate. I seem to recall Pete going to work for Lockheed before he was an engineer. Also from memory recall the Sonex being a collaborative effort with Pete handling engineering support.

 

[Derswede]

I had two for sale for awhile for a friend. Interesting design, a couple did have some failures, the spar was an extruded piece, and one means to lighten the bird was to cut several holes in the spar to drop some weight. I do know that two airplanes, so modified, suffered spar failures. I would have bought the two I had for sale, but I did not fit it (I'm 6'2", long legs) and the engine seemed to be a sore point in the design. The birds were sold to a guy with the $$ to do what I wanted to try...electric conversion, solar panels on the wings (some new lightweight design which looked more like a plastic film) and a small hybrid powerplant. Performance as a sailplane was OK, as some were built as true sailplanes, and the /P was the bird with the engine.

Derswede

 

[Topaz]

...Performance as a sailplane was OK, as some were built as true sailplanes, and the /P was the bird with the engine.

Sure you're not thinking of the Monerai? I've only heard of one Moni built without an engine, and it wasn't a factory-designed conversion.

 

[Little Scrapper]

I just looked up that Monerai, that's pretty cool.

 

[bmcj]

Was it the Moni that had a bonded wing skin without rivets, and some builders added rivets in the trailing edge later in response to an actual separation or concern of that possibility?

 

[Derswede]

No, it was a Moni, my mistype, by the way, the two birds here were Monerai's. The sail Moni was up in the Newport News area of Virginia, only one I had ever seen. The owner (Ralph Hinson??? Henson or maybe Henderson)) told me that several were built with a longer wing, sans engine, but that the Monerai was a better sailplane. His bird had what looked like a Monerai wing on it, quite a bit longer than the stock Moni wing. It may have been a local mod, don't know. He wanted something he could sail in, was going to convert it to a /P later. I heard that he had passed some years back, do not know what happened to it or the Quickie he was building.

Been awhile, memories don't float back to the top as fast anymore. Apologies on any confusion.

Derswede

 

[Derswede]

The Monerai definitively had that problem, the one here had been riveted and had the spar plates added. It only had about 100 hrs on it. De lamination was a real problem, everything had to be just about perfect to get everything to bond properly and hold.Derswede

 

[Turd Ferguson]

The Monerai had bonded wing skins but I don't recall any problems with that process

 

[mcrae0104]

Someone familiar with the book might chime in here and verify/correct any of this.

It's a good read. Highly recommended. I admire Monnett because he has managed to get a lot of things done. Very few of us can say that. Also I think he's a great example of taking an unconventional course (he was a teacher) and finding success doing what he loves.

 

[Turd Ferguson]

It's a good read. Highly recommended. I admire Monnett because he has managed to get a lot of things done. Very few of us can say that. Also I think he's a great example of taking an unconventional course (he was a teacher) and finding success doing what he loves.

Rags to riches to rags to riches story.

 

[Victor Bravo]

There had been an article by a highly qualified engineer about the mistake of cutting the lightening holes in the Moni spars. I had posted about it here, and I had mistakenly believed that engineer was Bruce Carmichael... and I recall that someone pointed out that it was Stan Hall who had written that???

But the article was definitely written in response to the Moni spar failures event hough it did not mention the Moni by name. The clear take-away was that it is a bad bargain to cut lightening holes in the spar, at least the way it was shown on the OEM Moni drawings.

The Moni and Monerai also had some structural failures due to the fact that the original instructions called for epoxy bonding the skins to the ribs and spars. As we have all discussed on HBA more than once already, bonded aluminum structures are do-able under controlled conditions in a professional aerospace environment, but bonded aluminum construction is generally NOT reliable when you leave it to garage homebuilders.

There are apparently chemical conversion processes that would allow homebuilders to achieve reasonable bond strengths (70-75% of material strength) but these have not been incorporated into mainstream homebuilding. The sad, harsh truth is that flush rivets are still a better and safer bet for homebuilders than gluing aluminum, which is why Sonex has used blind rivets successfully ever since the Monerai / oni failures back in the 1980's.

In response to Little Scrapper's initial attraction to the Moni, which many of us had already fallen in love with... The Moni airframe could be an ideal economical sportplane now because there are now far better engine options in the 30-40HP range than the KFM. The little Simonini and Polini 33-36 HP engines would make a 20 or 24 foot span Moni variant into a tremendous performer. But Monnett invested heavily in the Sonex series, and now the Onex single seater, and he has a strong business model for them (which includes selling Aero-Vee engines). So Monnett has no reason to re-visit the Moni despite how good of a little cheapskate cross country cruiser it would be.

 

[Pops]

My old close friend and flight instructor since 1937 and powered, sailplane and float plane instructor built the Moni. I believe he scraped it. He wouldn't anyone else fly it. Wanted to spin if stalled in either direction.
I bought Monnett VW engines items when I was building my KR-2 in the 70's. I made a promise to myself to never buy from them again. I have lived up to that promise.