Facetmobile

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Dart

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To me the brilliance of the Facetmobile is that it makes us check our assumptions about the importance of curvy streamlined flight structures. As I understand things, the Reynolds number of a very deep wing like this is so low that making it smooth is much less important than our intuition may tell us. The issue that the Faucetmobile faces is the very high frontal area and sectional area. It's my understanding that the newer designs along the same lines are made with thinner wings to help reduce frontal and sectional area. The fact that it had a simple engine, and was puller rather than pusher, is easily explained by the fact that it was an experiment, and like any good experimenter, the inventor chose to use as much simple and known technology as possible, and reduce the number of variables. It's difficult to see how bound the experimental aircraft community is to the conventional cruciform layout, however a lot of people have died trying to fly, so it's not surprising that only a few people have the vision, and the knowledge to go outside the conventional box.

My understanding is that most airfoils are as thick as they are, to allow the spar to be tall, and therefor stiffer and lighter. This of course has the downside of increased frontal area and sectional area. I'm wondering if a few sheets of aluminum, carefully cut like the origami boats, could create a very stiff upper wing structure, with no conventional spar, but with the loads carried in the wings skin.
 
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Riggerrob

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Good questions urquiola,

The Facetmobile prototype had a small, 2-stroke engine because that was all that was needed for an ultra-light proof-of-concept.
Later Facetmobile variants are all planned with 4-stroke piston engines.

Wankels are a no-go in Canada because they offer few advantages over pistons and wankel automobile sales quit years ago .....

Most small deltas have tractor propellers for balance reasons. Their centre of gravity needs to be in the forward 1/3 of wing root chord to gain stability in pitch. Hanging an engine in the nose is the easiest way to balance.
Hanging a propeller off the nose also allows for short landing gear legs. Some deltas (Dyke and VerHees) fix undercarriage at the perfect - nose angle - for take off .... simplifying pilots’s work load.
Deltas are fussy about precise angles of attack during landing and take off.

A few people have tried pusher deltas, but often find that they need extension shafts (Heuberger) to mount the prop aft of the trailing edge while keeping the engine close to the C.ofG.

Dean crashed his pusher delta - on its maiden flight because the idling propeller blanketed the elevens.
If you listen to Paul Bettorelli’s latest report from Aero 2019 Friedrickshaven (AvWeb), he explains that Pipistrel has sold 50 proof-of-concepts to private owners, and electric airplanes are almost ready for flying schools ....
Internal fans require sophisticated understanding of internal airflow.
To better understand internal airflow, we are encouraging www.frasertechnologies.www to reprint their book about Rohr’s 2-175.
Hint!
Hint!
Another alternate power source are the jet engines currently powering the larger RC model airplanes. Any day now, a row of model new will power a Victor-style small delta. ......

Personally, I want a cross between Facetmobile and Rohr’s 2-175.

Barnaby Wainfain did suggest aluminum honeycomb because he was using honeycomb to build satellites while sketching the PAV for NASA. We definitely want homebuilder plans to include CNC cut files (ala. Verner’s Delta 2) because CNC files both reduce labour and improve precision.
 

vhhjr

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As one who has helped with the EAA 292 build from the beginning of the project I can say that everything mentioned in this forum has been discussed at one time or other. Propulsion schemes such as buried or trailing edge ducted fans were considered and rejected for the simplicity of a conventional more mounted engine and prop. There's a great advantage to controlling the number of new technologies in a project like this. To date there have been very few successful manned aircraft powered by a ducted fan. Other possibilities such as retractable gear have also been looked at. All were rejected to keep it simple.

We also looked at honey comb panels instead of fabric with a sleight weight penalty. A 1/3 RC model of a two place version has been built, but not yet flown. It was built using the same techniques one would use to build a full size with composite panels. A nose mounted engine was again chosen for simplicity.

Once the current FMX project flies then other improvements for next versions can be considered.

Vince Homer
 

bmcj

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Did your engine studies include electric motors? Electric motors (by themselves) can be very light and compact compared to internal combustion engines, and the systems allow for easier distribution of component weights.
 

vhhjr

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Electric motors are very light, but batteries and hybrid systems are heavy so there's no magic solution. It would be an interesting concept to use a centrally mounted hybrid and strategically located electric motor driven props or maybe ducted fans. Once again we talked about such systems, but went conventional to keep it simple.

Vince Homer
 

Urquiola

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Hi!: thanks for the interest. This is the Pladur gypsum link: https://www.pladur.com/en
https://www.pladur.es/en/systems/special-systems
Pladur is house building material, upon request, they provide you with weight and resistance data
https://homefixcos.com/difference-sheetrock-drywall/
About ducted fans, well, I still have a copy of Hovey booklet, but there are others in the web.
The idea is airplanes require 100% power for takeoff, climbing, but at cruise, power needs are lower, let's say 50 to 75% of top power. https://axteraerospace.com
This allows having an electric propulsion, lighter, more reliable, more efficient, with a battery of enough size to supply added Amp in this extreme flight envelope, and a generator sized for the cruise needs, thus batery doesn't need being very big nor heavy.
Wankels are much lighter, compact than reciprocating engines; at constant speed, and with load above 33%, fuel economy is acceptable, even more, faults are rarely total, Wankel can deliver some power for a while, allowing a safer emergency landing. See corresponding article in Wikipedia
Besides the converted Mazdas, you have several Rotary Engines, for the 30-50 HP, the Aixro:
https://woelfle-engineering.com , then https://www.wankelsupertec.de , the Austro: http://austroengine.at/en/home1 the UK AIE: https://www.aieuk.com or several German and other makers: http://www.wankel-ag.de
http://3w-international.com
https://skypower.online/produkt/sp-480-hybrid-twin-rotary-engine/
https://www.nwuav.com/engines-rotron.html
https://uavenginesltd.co.uk/products/
https://freedom-motors.com
For sure, exhausts and engine heat can be added inside the propulsive duct behind fan and engine to add some thrust, an energy that otherwise will be lost, this worked with the Mustang P-51 engine cooling radiator.
As with everything in design, the issue is calculate, calculate, calculate, then-> Wind tunnel, models,....
Another change I'd consider in the Facetmobile is a single central rudder, double rudders always have an assimetry danger if one side fails, the current facetmobile rudders, if fixed, could make the job of wingtip vortex control, drag reducers, you could watch:
Patents US1848578 Roy Scroggs, US 1887411 R B Johnson are nice designs looking at (Espacenet)
Have a nice time. Salut +
 
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rv7charlie

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Is this the kind of product you're talking about (commonly used in the USA for yard signs, etc)?
https://www.google.com/search?q=coroplast&rlz=1C1CHBF_enUS843US843&oq=coroplast&aqs=chrome..69i57j69i60l3j69i59j69i65.2322j0j4&sourceid=chrome&ie=UTF-8

I've often wondered about using it for rapid construction of something with light wing loading, but never explored whether any adhesive can even bond to it.

BTW, the P-51 didn't add exhaust flow to the radiator cooling air exit (note the 6 stacks on each side of the cowl); it was simple heat gain through the radiator that supplied the extra heat.
 

vhhjr

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Ref. Urquoila's comments:

All very possible, unfortunately, no one sells an extremely lightweight generator in the power range required. One could build one from brushless motors and an IC engine, but that's another major development project. Those working away in their hangars or garages have to keep the number of development projects to a minimum in order to ever get something finished.

One advantage of double rudders is to be able to use them as speed brakes. It also reduces the size and structure to have double rudders rather than a single one. Many models have been built with singles and they fly just fine. It's really a matter of choice.
 

Urquiola

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Ref. Urquoila's comments:

All very possible, unfortunately, no one sells an extremely lightweight generator in the power range required. One could build one from brushless motors and an IC engine, but that's another major development project. Those working away in their hangars or garages have to keep the number of development projects to a minimum in order to ever get something finished.

One advantage of double rudders is to be able to use them as speed brakes. It also reduces the size and structure to have double rudders rather than a single one. Many models have been built with singles and they fly just fine. It's really a matter of choice.
Finding a generator light enough may be solved by adding a lightweight ICE, as Wankel is, to a known generator, this may require calculations, adaptations, tests, but it's not impossible, Aixro considered for a while a 294 cc per chamber Wankel-Generator unit, but discontinued development, other RCE makers may have one. In eBay, you find sometimes turbine-generator units in the 130 HP range for acceptable prices. Good luck! Salut +
 

rv7charlie

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Still wishing Barnaby would do a 4 (or 6) seat version, or at least the PAV 2 seater he postulated. I got to see the original when he flew it to OSH, and have always been very interested in the concept, but cannot justify building a single seat a/c. I could be completely wrong, but it 'feels' like the concept should scale up in capacity with even more improvement in structural efficiency.

Charlie
 

bwainfan

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Original airplane was aluminum just like the Oregon build. The outer mold line shape is the same as the original airplane. Its not scaled up or down.

There have been detail updates and changes but the overall approach is the same as N117WD.

The Facetmobile itself was always built to be single-seat. Only 46HP from the Rotax 503 and intended to be a concept-explorer.

My personal intention has always been to do a 2-seat follow-on airplane and I am still working towards that goal. I have done occasional looks at bigger designs in response to inquiries, but at the moment at least, a larger airplane is not where my personal needs/resources lead me.

As far as designation goes: My convention when developing configurations is to assign an FMX- number to each basic "hull" shape and then use letters to designate detail changes. The original airplane was FMX-4D. In my configuration nomenclature the Oregon airplane would be an FMX-4E. Of course, its Bob's airplane so he can designate it any way that pleases him.




Always an intriguing design. Interesting the chapter is going with Graham Lee / Airdrome Aeroplanes style construction. The original was welded steel I believe.

Will be interested to see how they handle entry/egress. The original had a trap door in the floor you had to crawl up in to. A kit would benefit (at a weight penalty) of a hard backbone to walk up the spine of the ship and sit down into the seat. The pics don't show them heading that way however. So getting in and out may still be a chore.

I think the original, while flown solo, was intended to be a three-seater (or maybe I'm recalling that it was a single-seat proof of concept for a later three-seater, I'm not sure.) I wonder how much the EAA chapter scaled it down as it looks as though theirs in intended for on seat.

If scaled down, and with the change in construction materials, I wonder if they will keep the designation FMX-4. It seems like a derivative that needs a new designation.
 
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