Single-seat ultralight puddlejumper: the "Carbonmax"

[TFF]

My thought is the concept should be moved up to the two seat LSA size plane. It has nothing to do with not liking the smaller plane. It’s more about market; there is more money where the mouth is, the next tier up. Also more will for building there too. More will to finish what is started. The only other thought is if you are self molding the tail, why not the nose? Maybe supply the top part in front of the cockpit if shape is complex and the forward sides built with the supplied top as the base for the forward mold.

I have been thinking of how to do legacy wood wings in composite. Mostly mold less like spars and standard ribs. Your D section with aft ribs would be a good solution to this.

 

[lr27]

Boku:
How much do you think this aircraft would weigh?

I wonder if it would be easier to bag the whole wing and then cut lightening holes to create "ribs". I suppose the shear web might require a two piece core.

 

[Victor Bravo]

Man I hope he's not the Ken Rand of the new millennium, Rand died shortly after the KR airplanes began to get popular. I want Bob to be around and innovating for many years

I'm not nearly as much in favor of the design configuration in his sketch as I have been about several other design exercises. No prejudice againt this configuration or against Bob whatsoever. I'm thinking that putting the advantages of carbon to the fullest use (in the E-AB world) is best done by allowing very small minimalist aircraft to be built that are so light and small that they achieve really significant performance on low power.

Small airplanes cost less because they use less material. Small airplanes require less storage space. They use smaller, cheaper engines that use less fuel.

So at the risk of re-railing Bob's thread, I'd like to see this general concept (carbon used for a minimalist homebui lt) "redirected" towards something the size of a CriCri, BD-5, the Debreyer Peican, the DePischoff biplane, the Whing Ding, the Davis DA-11, the J-5 Marco...

Really really small, car-toppable, a "suitcase" ultralight, somewhere along that direction.

 

[cheapracer]

As a business Bob, and you are a businessman, Iove the concept, but 2 seats for sales.

 

[sming]

I feel like it's just a "marketing" problem.
For example, I come from an european country where non-profit aeroclub is the way to learn to fly because its just the cheapest... the problem after that is flying ! When weather is nice on the week-end, every pilot in the club want to fly at the same time and that doesn't go well.
The way I see it, single seater should be marketed like sport motorbike (my country is also the first european market...). I don't see bikers complaining very much about the lack of second seat (its actually disappearing fast on recent motorbikes) because the girlfriend will ride once but not twice

Motorcycles cost between 10k€ and 40k€ and they have quite a market. So a single seater with racy looks in that price braket, marketed to pilots that want to fly at the same time as/with other pilots, with all the social aspects of a group, in my mind that could work.
And if your club has a few 4-6 seaters shared between all the members to fly your friends when you need it, everything is covered.

Going back to the topic: great effort BoKu, you are on to something! Just something sportier looking than a minimax?
I feel like you are describing a composite version of that : http://mag.01.pagesperso-orange.fr/
i like the way they do the styrofoam ribs taped with one continous fiberglass cut:

 

[Staggermania]

Although I prefer a high wing along the lines of the Ranger, one that you "starddle", rather than sit on or in, I think that sming is correct that an inexpensive and attractive(sexy),easy to assemble single place could find a decent market. Carbonmax is a good name. Maybe 2 x's on the end

 

[billyvray]

I love it. MOAR please !
I like the idea of covering the large carbon or glass areas with peel ply (Dacron). The result isn't glass smooth but does not have to be for an ultralight or light plane. Go right to paint. Neat textured surface like a fabric covered surface.

 

[harrisonaero]

Fun design Bob. One of the tips I've learned from Burt is NEVER wet layup (contact layup) carbon- always vacuum bag. You can't tell when the air is out like you can with glass. I won't say which project he learned the hard way on this one

 

[Hot Wings]

My thought is the concept should be moved up to the two seat LSA size plane

Small airplanes cost less because they use less material. Small airplanes require less storage space. They use smaller, cheaper engines that use less fuel.

Really really small, car-toppable, a "suitcase" ultralight, somewhere along that direction.

Maybe not that small, but I keep hearing there is no market for single place planes. Yes, there is. And it is a big one that is untapped. The people buying the planes haven't figured this out yet - thus no perceived market.

Look at motorcycles. How many of them are only practical single seat and of the ones that are practical 2 place how many get ridden that way. Most of the riders I know, if they ride as a couple, own 2 bikes.

All the 2 place planes in the 172 and down class*, at my airport, are flown solo almost exclusively except when they are used for training or to actually go somewhere - which happens maybe twice a year.

As a business Bob, and you are a businessman, Iove the concept, but 2 seats for sales.

2 seats is just raising the costs for another smallish plane aimed at the cheap market ..........that won't be all that much cheaper.........or cheaper to store.......or cheaper to fly.


Just my opinion.........


* a 172 is a 2 place plane here and a 150 is a single.

 

[Staggermania]

I think Hot Wings is right. There seems to be a large contingent of stol aircraft owners that do a lot of group flying, and quite a bit of the time it seems that they are flying one up.
So perhaps a small, inexpensive single place would do well.

 

[Pops]

I really like the idea. The cradle for the aluminum mold could be made up and used and then passed along to other builders in the area. Would fit in a mini-van or a pickup truck.

 

[plncraze]

The motorcycle analogy is a good one. Cheap, fun and entertaining. A couple rolls of $20 a roll carbon, a cheap core and the engine from your neighbors riding lawn mower and you are set.

 

[Hephaestus]

I think it's the cycle of life... How many people have started a 4 seater in their 20/30s, then got sucked into the family life - sports tournaments on weekends, events 2-3 nights a week... they hit their 40's, kids have left - soon to leave... They've got about a thousand hours into a 4000+hr build... But if they started today they'd realize their wives want 737 travel... So who's to fly with them.

I'm a ramp rat so to speak, 85%+ of what comes and goes from my field, pilot is the only occupant... Maybe 10% are student/instructor... So maybe 5% are grandpa introducing their grandkids, or husband/wife off for a hamburger/visit somewhere...

I've said it before, a quicker build single place - seems reasonable. Keeping it mostly a single technique/single material makes good sense. So you're not sitting waiting on the brown truck to deliver more materials for your next step.

I'll be following along, I'm curious how boku will handle the structure

 

[TFF]

I own a single seat project almost done. The kids will not be happy they can’t try it.

Single seat first says, you are not invited. That is a put off for a regular person. Pilots don’t care because they can get in something else. Your paying all this money to store and no room to share. The second seat is a peace offering for the people who can’t. Doesn’t mean they will, but it says your not selfish.

Second, singles are small. Some people’s brains can’t wrap their heads around by your self and response of something small. A few feed on it, but not many. Bigger is better is always the way we are taught. It’s like motorcycles. Single seat is like a sport bike. Really only fun by yourself. Unless a rider herself, a wife wants to be on the back of a Harley or Goldwing if she is coming, not a sport bike. If she is a rider, she is rare.

 

[BoKu]

Fun design Bob. One of the tips I've learned from Burt is NEVER wet layup (contact layup) carbon- always vacuum bag. You can't tell when the air is out like you can with glass. I won't say which project he learned the hard way on this one

Never is a long long time. One of the things I learned in rock climbing is that sometimes, every once in a while, the thing they told you never ever to do is the one thing that saves your neck--if you do it with respect for its inherent limitations. When we do ambient wet layups in carbon, we have so much margin that any entrapped air bubbles are irrelevant--if we're careful and keep it all down to a dull roar. One of the things we do when we're adding bits of ambient carbon is to use splotches of flox-thickened resin in corners and anywhere air bubbles are likely to form. We are also very careful about using peel ply that prevents air from sucking down through the carbon to fill bubbles. We've sawed several of these things open and they are pretty much black all the way down.

 

[gtae07]

I think the biggest obstacle for the single-seat market is that single-seat airplanes may have half the seats of two-seaters, but they generally don't weigh half as much, and almost never cost half as much, or take half the time to build, for comparable performance.

Second seat is also extra baggage and/or stretching room if flying solo.

TFF just beat me to the punch of what else I was going to say. Most of the potential market has other people (spouse/kids) they're answerable to in some way or another, and two-seaters go over better with those people.

 

[Riggerrob]

Instead of using aluminum to mold rear fuselage skins, how about vacuum-infusing them on a large, flat table, then wrapping them around ... along the lines of fold-a-plane or American Vision.

 

[Riggerrob]

If you continue using “black aluminum” thinking, then look at the beautiful flat-wrapped engine cowlings made by Thorp and Davis.

 

[BoKu]

Wow, this thread really blew up! Based on the last simple glider design I posted, I didn't expect anything like this response.

I did a preliminary loft of the fuselage and a side and top view based on the loft and a guess at the wing:



Some notes and comments:

* The span and length are the same as the Mini Max, but the wing area is a bit less; 89 versus 112.5. However, on the Mini Max a lot of that area is out at the tip and isn't working very hard because of inherent tip losses. So I'm not particularly worried about the takeoff and landing speeds.

* Observe that the wing spar carrythrough takes up considerable cockpit volume. This is just one of the packaging realities of a cantilever single-seater. To place the spar under the pilot's knees I had to move the wing about 7" further forward than on the Mini Max. To compensate, the engine is moved forward a little, and the aft fuselage would have to be a bit lighter than on the Mini Max. I think that there is enough flexibility in the design of the engine mount and the location of ancillary components to make the CG come out in a reasonable spot. This might also make the airframe more amenable to a heavier powerplant like one of the B&S clones with a redrive.

* The pilot is the standard Darryl Stinton model scaled to 6'2". For a tiny airplane like this, I wouldn't want to try to design it for any larger pilot.

* The fuselage encloses a lot more volume than the Mini Max. However, there will be a lot less parasitic drag from struts, wires, and other protuberances. So the overall cruise drag is probably a lot lower.

* As sleek as this thing looks, it would be very lightly built, basically a carbon fiber bubble in the shape of an airplane. When the engine is running you'd see the lighter parts of it shimmer like a soap bubble in the wind. The VNE would not be very high, probably 100 - 115 mph. Rule zero is never let epoxy resin touch your bare skin. Rule one is, don't crash.

* As I proposed earlier, the wing is a combination of moldless foam core (MFC) D-tube and fabric covered ribs. My reasoning is that air is lighter than styrofoam even if it is partitioned by the occasional web of carbon fiber. However, you'd have to be careful about fully encapsulating the foam core of the D-tube to protect it from attack by chemicals used in later finishing processes. Plenty of LongEZs survive being painted, so it's probably not that much a problem.

* The aileron/flaperon is MFC and goes pretty much full span. It is driven at the inboard end and hinged on four sections of extruded piano hinge. The hinge pop-rivets to inclusions of Garolite under the composite skin. The aileron is constant section for simplicity.

* The wing section is an RIFPIB (round in front, pointy in back) loosely based on the 23000 series, and jiggered as necessary to accommodate the constant section aileron and drag spar. It probably sets a real aero engineer's teeth on edge, but it's not nearly as bad as what passes for a wing on many ultralights.

* The tail surfaces are MFC, and probably semi-permanently attached. The tail span is 90" which is probably okay to trailer if you're careful.

* No, this isn't a real FAR 103 ultralight. You could probably bring it in near the Mini Max's 280 lbs, but I doubt you could make it lighter. But you could probably get it within range of a strategic game of liar's dice. The FAA would probably only check if you crashed it, and it's doubtful they'd bother even then if they weren't certain they'd found all the pieces.

* If you squint your eyes a bit, you see that one wing is about 7/8" further forward of the other. That lets the wings be mirror images of each other but still allows the wing spars to overlap inside the fuselage. Do not confuse symmetry for balance.

* The configuration I've drawn is a razorback, but a lower fuselage top and a bubble canopy would not be beyond reason.

* If you really wanted to make this thing into a subscale warbird replica, it wouldn't be that hard to customize the wingtips and flaperon trailing edges to achieve something like the desired effect. P40, Hellcat, and Spitfire would take only minor tweaks. For a P51 you could put a little scoop and oil cooler under the belly, but a real engine coolant radiator is probably out of the question.

 

[BJC]

Here’s the aluminum version: http://www.greatplainsas.com/bk1.html


BJC