Discussion in 'Tube and Fabric' started by cluttonfred, Feb 28, 2018.
You may want to check out the headwind. Its like a single seat cub
With a Rotax Rick 670(92hp@6400rpms) would be a nice setup. If you ran the 670 at 618UL 6750rpms it can make about 105hp. A 670 can also be Big Bored to a 748 that would put you over a 100hp@6400rpms.
Build a Standard 670(669cc) with a Turbo, Jetted to run 100LL, and run it Max 6000rpms, 750rpms less than the 618UL was rated from same engine family and it should make over a 105hp depending on Boost used.
669cc at 4000rpms @2lbs Boost = 72hp
669cc at 4000rpms @4lbs Boost = 80hp
669cc at 4000rpms @6lbs Boost = 89hp
669cc at 5000rpms @2lbs Boost = 89hp
669cc at 5000rpms @4lbs Boost = 100hp
669cc at 5000rpms @6lbs Boost = 111hp
669cc at 6000rpms @2lbs Boost = 107hp
669cc at 6000rpms @4lbs Boost = 120hp
669cc at 6000rpms @6lbs Boost = 133hp
Simonini, makes a 54hp Single.
Could a light tube and fabric two seater have any hope of survival let alone popularity? People in this thread are already mentioning a cockpit enclosure for the E-2 (which there was originally available), next comes flaps, tundra tires, long range fuel tanks, a big engine for STOL performance, and all the complaints about there being no useful load that come with all that junk. Look at any other simple-ish two seater for sale now.
I hear you, Tim, but I guess it comes down to what you define as success. Plans sellers rarely if ever make much more than beer money, but modest kits or component sales could be sustained on small numbers. Say a dozen complete kits a year to sustain a part-time business? Is this market niche likely to provide stiff competition to Vans, Sonex, Zenith, and various European slick microlight manufacturers? No, probably not. But a minimalist, traditional steel tube design with wood or aluminum wings would appeal not only to European microlight pilots but to anyone around the world looking for a modest, amateur-built two-seater including Part 103/SSDR flyers looking to move up to two seats.
Taking the traditional Cub layout of a light, tandem two-seater flown solo from the rear, I could see multiple versions of the same basic airframe offered: traditional (E-2 Cub) or modern (Raceair Skylite) looks, open or enclosed cockpit, taildragger or tricycle (like a Tri-Champ) gear. All that really means is two different options each for cowling, rudder, main gear, and possibly turtledeck treatment. Raise the rear seat a little higher than the front seat to ensure good visibility and make the cockpit width, legroom, and headroom generous enough for a big and tall pilot (say, up to 200 cm/6' 6" and 125 kg/276 lb). Deliberately stay away from the more powerful and more expensive engines (Rotax 912UL and up) and instead go with VW power to start and add options like the Verner 5VW, Pegasus O-100, or Aeromomentum AM10 over time.
Straight from the horse's mouth. Thanks!
That impression came from reading Engineering Aerodynamics by Walter S. Diehl, who quoted NACA research in his discussion of biplane wings. I don't have the book handy, but I recall the drag penalty being roughly 3x the drag of the unmodified airfoil. In the grand scheme of a draggy airplane, however, it's still a small contribution.
Thanks for that, I actually found that entire book online as a DTIC reference and pulled the text:
It looks like the drag penalty is not that important as long as the forward section of the wing is left untouched, there is just a loss of lift corresponding to the loss of wing area in that section. That still doesn't really explain why the E-2 Cub had the cutout in the first place unless is was just for aesthetics or tradition. It doesn't seem to do anything for cockpit entry or visibility. I am still stumped!
On a related note, I had an offline conversation with Tiger Tim that included a discussion of steel tube fuselage styles. While I do admire the simplicity of the old Aeronca-type fuselage with four longerons forward but only three aft, looking closely at Leonard Milhollands' Cabin Eagle plans has made me wonder if perhaps that's more trouble than it's worth.
There is something to be said for a simple four-longeron fuselage with the sides built flat, firewall to tailpost, then wrapped around a couple of temporary formers while you weld in the cross pieces. I also wonder about the need for a center section and think that maybe simple inverted V-style cabane struts and two wings panels taht meet in the middle is also easier and simpler. In essence, I keep coming back to something like the Heath Parasol (the one with the V-struts not parallel struts) or Ed Fisher's Skylite.
If you're seating two in tandem I question the inverted vee cabanes. The struts end up right where the occupants' heads need to be, just take a look at a picture of an American Eaglet in flight to see how uncomfortable it must be.
Innovation is really wonderful, but there is also a very large value to what has already been shown to work well and be easy to construct. On a simple low speed aircraft like we're talking about, there would have to be a pretty significant carrot dangling in front of us to justify deviation from a "standard" configuration.
I'm sure that there is some weight savings on a three longeron fuselage, especially in torsion, but is there a general rule of thumb for how much heavier a four longeron fuselage is for taking the same torsion and bending loads? Are 1937 Cub and Taylorcraft square fuselages 5, 10, 25 pounds heavier than the 1937 Aeronca three longeron fuselages?
I have personally seen and handled the plywood superstructure secondary bulkheads and spruce stringers removed form a pre-war Aeronca Chief. This pile of wood is as heavy as a few feet of steel tube, make no mistake.
The American Eaglet is probably a bad example as it has those odd forward struts right in the cockpit that other designs avoid by using one or two struts forward from the front cabane and/or aft from the rear cabane. Compare this Eaglet fuselage to the Skylite and Parasol above.
I am sure you're right VB that weight of the superstructure to fair out the cockpit will offset some or maybe all of the weight saved from the simplified steel truss. The cabane structure trade-offs are less obvious to me, though presumably two, three-strut "tripod" cabanes would be pretty efficient.
Ed Fisher, if you're reading this, why did you use a three-legged tripod in the front but a four-legged one in the back on the Skylite?
As awkward as the Eaglet arrangement is in terms of cockpit access, it does seem to be the absolute simplest way to support both front and rear spars with the fewest possible number of struts in the cabane. You can always move the cabane forward and sweep the wings aft to end up with something very French like a Morane Saulnier MS.341, fine for open cockpits but that doesn't really work for a cabin type. Maybe a big bubble canopy over both seats like some of the modern biplanes....?
GOOD MARKETING is your biggest problem to overcome. The is about 8 Billion People in the World today. Twice what there was in the hey days of Ultralights and Kitplanes. Design a Plane for Two 6'-6" 350lb Persons, then it will fit 98% of the World Population for Sales, not 35% that most Planes are designed for, a 5'-8" 160lbs.
Chalenger 4000+ built, T-Bird II 4000+ built, M-Square 8000+ built, etc. Check out Production Numbers on Kitpane Magazines web site. To Survive you have to build a Quality Airframe and use a Reasonably Priced Engine. For any Tube & Fabric - Two Seater, 65hp Minimun!
Rotax 503 with an R&D Tuned Pipe made 62.3hp@6500rpms, with a few improvements could make 65-70hp.
Rotax 582UL 65hp $7500 with Cooling, with a R&D Tuned pipe around 75-80hp
Rotax 618UL 73.4hp@6750rpms, with a R&D Tuned Pipe around 85-90hp
Rotax Rick 670 93hp@6400rpms
Hirth 3203 65hp
High Dollar Engines:
Rotax 912 80/100hp
Rotax 914 115hp
Bearhawk lsa 750lbs two seat tandem aluminum wings. Ultra pup folding wings tandem 450lbs. Acrolite 2m 600lbs aluminum wing.
I'm building an Ultra Pup, seems to fit your specs pretty well. 3/4 scale Cub, 2 seat tandem, 450-500lbs empty, 1000lb gross with 60hp VW. 35mph stall, 80-90mph cruise.
One of the neatest Airplanes that could be made for Part 103 or Light Sport, that was Designed by an Aerospace Engineer out in California, but only about 30-40 got made before he died, was the Sparrow Hawk. It was only made as a 2 Seater that I know of, but the Wide Cabin Design could be narrowed for a Single Seater. I believe the Cabin was made of Fiberglass, Wings were metal. If I remember right, the Plans & Tooling were sold to someone in England, but they didn't get it put into Production. That would be nice today with the new light weight O-200(100hp) or Rotax Rick 670(92hp).
Today, with Carbon Fiber and Aluminum, Tube & Fabric, Lithium Batties, more Engines to pick from, etc., you could make one pretty light to meet Part 103, using a Simonini Single-Cylinder, in 44hp, 48hp, 54hp Victor Super Engines.
There are lots of great 103 designs out there. I'm 6'6" 225lb and won't fit in all of them. I'll likely design for 6'8, 250lb, gives me a bit more space! 350lb people need to reconsider whether they would rather fly or drink soda by the pint IMHO.
Or they can use two seats...
If you look at the Phienox 103 that use's the Hirth 50hp and has the Highest Useful Load of any Part 103's of 396lbs. 396-30= 366lbs for Pilot & Bags. Set's the Bar. It would be Better, if the Cabin Hoop was made Wider. I believe a Simonini Victor 1 Super, 54hp Single Weighs less than a 277UL with a Gear Drive. A Kawasaki/Suzuki 440(40hp@6500rpms with a Muffler) probably Weighs less than the Hirth 50hp. Does a Part 103, really need 50hp, NO. If you Designed a Good Tuned Pipe for them 440 Engines still made today they could easly make 50hp also. Tall, Wide, Atheletic People in the World like to Fly also, their not all Chubby Couch People. 95% of the World, 8 Billion Population fit's in 6'- 6" 370lbs envelope. So you decide if you want to Sell to just 10%, 20%, 30%, etc., of the World Population. You have to look at Who can even Afford a Plane today. The Average World meridan Wage was $14 an hour. 40hr x $14 = $560 a week x 52 weeks = $29,120 a year. A Phienox 103 was around $16,000. The Hirth 50hp Motor is around $4,959. With all Big ticket items, Doubling if not Tripling in the last 15 years, Cars, Trucks, Guns, Boats, Planes, Bikes, Food, Gas, Homes, etc., People just don't have the extra spendable income.
There was some Brand New Suzuki 440's(Arctic Cat), basically same as Kawsaki 440's on eBay a few months back for $950 minus Carbs. Part 103's have a Max Speed, so 35-40hp is all you would realy need even for a Big Person. Today, you can Source just about every part to build a New Rotax Engine, except the Case, Cylinder, Head. A 277(25-35hp) and 377/380(35-50hp) Based Engines would handle all your HP needs for any Part 103. There are Companies in China that make Engines and Engine Parts Cheap. I inquire a couple of years ago to make a Billet Head for a Skidoo 670 with Inserts, $400 for Design Work, and $400 to make just a one off. The more you had made the cheaper they got. So a 277 or 377 Solid Billet Head would cost any more. A Foundry quoted me, $1,500 to make the Molds for a 503UL Dual plug Head, and then charge a Small Fee for each Bare Casting, again the more you had made the cheaper they get. One Pair of 503UL Heads from Rotax is $950, a 582UL Head is $820. The thing about making your own Core Parts is you pick what CR the Heads are, you can Add Material where thin, or need more Cooling Mass. You can pick either Piston Port vs Reed Fed. Hot Rods makes Rods & Cranks. The Crank Shop makes some Cylinders, Case's, etc. But you can have them made much cheaper.
Indeed, I would see the Raceair Skylite design reviewn towards a Pietenpol SkyScout look, but with a 3 piece wing.
A center section which would remain with the aircraft and two detachable or foldable outer panels.
If the Race design is to remain, the changes would more less be limited to make the stern less swept back.
In fact, the skylite would give an excellent base for an ultralight version of the SkyScout.
Today I remembered this post, browsing my hard drive I found two photos of the only two-seater Pober Pixie.
The Pober Pixie II I think it shares many of the features that you are looking for in this post. It's not like that?
The one which is always forgotten.
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