The weekend design concept

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Bart

Well-Known Member
Joined
Apr 13, 2007
Messages
311
How about a slick version of Al Backstrom's Plank? He, after all, got it right the first time, and has vastly better qualifications than most of us.

Picture this: Hershey Bar wing, one-piece spar, tip fins/rudders. ~8' pod fuselage along the lines of ASW-22 sailplane or Winton's Facet Opel. Centerline retractable tandem gear (like Strojnik S2 but retractable), wingtip outrigger wheels s hidden in the lower tip fins. ~40hp liquid cooled inline motorcycle engine, belt reduction, 48" prop. Empty wt. < ~250 lbs.
 

pie_row

Well-Known Member
Joined
Nov 9, 2009
Messages
710
Location
salt lake city Ut
I want the old star light by mark brown. but with a carbon fiber pulltrusion wing rib and fiberglass wing skins. Ya and e 4 stroke engine with a big prop. at the 250# emptyweight and 500# gross
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,686
Location
Corona CA
Geez, I can't believe I've never heard of the Guiberson diesel before - an apparently successful aviation diesel radial; I didn't think there was such a thing:
Yes, there was really nothing wrong with this engine. It was comparable to the Wright engine of the same power and was barely a couple of pounds heavier. Maintained its power to a far higher altitude than the Wright too. And its reliability was proven in thousands of tanks, the Stuart light tank of WW2 for example.

There are two of these sitting in an orchard not far from me and I am seriously tempted to get them, but it would cost me something to rent a crane to get them down from their towers; they were used as wind machines.
 

Dieselfume

Well-Known Member
Joined
Mar 30, 2004
Messages
102
Location
S36 Kent, WA
Thi s has been my weekend design project for about 20 years now. All composite, mostly moldless construction, flying yacht. Looks short and fat, to get decent interior room. there is standing headroom just behind the cockpit, bathroom at the back, galley and bunks for two. Span 40 ft. 2x 200-300 hp radials; Ideally I want a pair of Guibersons, run on diesel and get range enough to get to Hawaii. Ah, idle dreams...

Sounds almost like a Gweduck, except the gweduck is not moldless, and has IO-540's, and you can't quite stand up in back (but a lot more room in the aft fuselage than a Wigeon). It nearly has the range to make Hawaii, so wouldn't be that much extra fuel to make it.
 

Autodidact

Well-Known Member
Joined
Oct 21, 2009
Messages
4,513
Location
Oklahoma
There are two of these sitting in an orchard not far from me and I am seriously tempted to get them, but it would cost me something to rent a crane to get them down from their towers; they were used as wind machines.
Well, not to encourage somebody to spend more money than they should, but maybe you could rig a a "gin pole" arrangement or a tripod maybe? Just how high up are these things?
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,686
Location
Corona CA
Well, not to encourage somebody to spend more money than they should, but maybe you could rig a a "gin pole" arrangement or a tripod maybe? Just how high up are these things?
Not terribly high, I would guess about 15t or so. A friend of mine really had the first offer on these, but he may have far too much sense to get involved with something like this.

The Gweduck is very close to my design, I had a good look at it at Oskhosh and was quite impressed.

The reason for moldless construction is only because it would be a one-off and for an amphibian, composites as a material choice is a no-brainer. Not much opportunity for leaks and totally unsinkable. The fuselage would be built from the inside out - the interior space and walls and floor is built up from thin ply, then foam is glued onto that, carved to shape and then glassed over. makes it easy to get a nice shape for the outside and you're not faced with the unpleasant task of glassing, filling, sanding and finishing the inside of such a huge fuselage. Mahogany ply on the inside leaves a nice yacht-like finish too!
Wings would be almost completely wet, plus some fuel in the engine nacelles.

Really a fairly simple structure, with the exception of the landing gear; like all amphibs, it's a little awkward to fold it all up into a small space. In this case it folds up and slides into a tunnel that runs under the pilots seats. I'm thinking pneumatics for actuators for gear and flaps and possibly starter motors too. They are available for many industrial diesel engines and it would minimize dependence on electrics. Keep a small compressor on board for emergencies and you can use the the air for inflating your dinghy too. Not to mention the scuba tanks.

This idea started out substantially bigger, (50 ft span) but refinement and common sense eventually brought the size down to this; my ultimate dream, airplane, bar none.
 

Autodidact

Well-Known Member
Joined
Oct 21, 2009
Messages
4,513
Location
Oklahoma
Make it out of riveted boiler plate and put some spikey spines in the dorsal area, "20,000 Leagues Over the Sea...". Seriously though, it's like the old dream of building a sailboat and sailing away from the workaday world only your going to fly. Much cooler than the sailboat dream if you ask me.:) (You can run those Guibersons on coconut oil, eh?)
 
Last edited:

lr27

Well-Known Member
Joined
Nov 3, 2007
Messages
3,822
A concept I've thought about before is a low aspect ratio delta wing for an alternative to the "airchair" glider. One might start with the general proportions of the Pibros slope glider. A picture of a Pibros is shown at the following URL:
http://www.rc-soar.com/pibros/pibros_ready.jpg
More info on the Pibros here: Pibros

To continue with the concept, the fin would obviously have to be enlarged and have a rudder. Perhaps tip fins would have to be used, although I have a delta wing model which responds to a central rudder even at very high angles of attack, and Wainfan shows a central rudder in his proposal for NASA. AR for the Pibros is around 3.2. Span for this might be 31 feet.

Because drag would be prohibitive at higher Cl's, you can get away with a symmetrical airfoil. If I can believe Xfoil, then with a bit of fudging it seems a glider version that was made cleanly might get an L/D of 12 to 15 at a bit over 30mph, and a sink rate of 150 to 200 fpm. This, I think, is in the region of airchair performance. You'd probably have a semi reclining pilot position, maybe an 15 to 18 percent airfoil at center, and thinner further out. Covering to be transparent(!) although possibly with some kind of rip stop grid. A canopy is probably a bad idea because of high angles of attack at times. The pilot would have perhaps 4 or 5 feet of aircraft between his feet and the tip of the nose, and in general quite a bit of crush space forward, to the sides, and even more backward. (which might influence where the chute goes). Handling ought to be pretty gentle, pretty insenstive in pitch with benign stall, a mush at most, and at a very slow speed. (At Cl of 1, we're talking 23mph!), and a higher Cl should be attainable.

One would have to confirm that the gentle stall was still applicable at this aspect ratio. I'm not quite sure how one would do this, since it would be Reynolds number dependent. On a powered version, one could use a sharp leading edge, but I think there would be a large performance penalty. On the other hand, this thing could be VERY slow if it had vortex lift and a good amount of thrust. Perhaps on the glider version some inner bar might press out on the covering to create a sharp spot when vortex lift is wanted.

It seems possible that this could be made with nesting sections (because of the taper) so that it might store compactly. Some hang glider guy might even make it so that all the ribs collapse toward each other, collapsing the covering and maybe even making it cartoppable, though I admit that root rib is going to be awfully long. Plus I'm not sure transparent covering would hold up to that.

Structural issues ought to be easily dealt with when the spar depth is maybe 16 percent of half span!

If there was a powered version, the motor probably ought to go in the nose, to keep the pilot near the center for crashworthiness. Power requirements might be quite low if the power plant could swing a big propellor slowly. 500 fpm might be available with 15hp! Forward visibility might be compromised, though, by the presence of the engine and cowling.

This seems like it might be easy to design and build, though I'm not sure it's an aircraft I'd want.

If it turns out a thicker center section works, a much smaller version might be made with a similar glide ratio, but the sink rate would go up.

If it turns out that the nice handling stays with a somewhat higher aspect ratio, perhaps the sink rate doesn't have to go up all that much.
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,686
Location
Corona CA
Make it out of riveted boiler plate and put some spikey spines in the dorsal area, &quot;20,000 Leagues Over the Sea...&quot;. Seriously though, it's like the old dream of building a sailboat and sailing away from the workaday world only your going to fly. Much cooler than the sailboat dream if you ask me.:) (You can run those Guibersons on coconut oil, eh?)
I have always had the dilemma of boats vs airplanes; it would be nice to combine the two. If for some reason I could not mess around with airplanes, I'd be living on a boat by now. Yes, coconut oil - I guess I could fly from one Caribbean resort to the next, taking their used cooking oil off their hands and have an onboard refining system or set up the engines for SVO operation! Until I get to Venezuela and I can fill up for 7 cents a gallon.
 

Norman

Well-Known Member
Joined
Nov 28, 2003
Messages
3,187
Location
Grand Junction, Colorado
Coconut oil is weird stuff. Great for cooking because it has a higher ignition point than any other oil and you can get with or without the flavor of coconuts. It's good for dieters too because it has a 1/3 less calories than other oils. Probably not a good stock for biodiesel
 

bmcj

Well-Known Member
Joined
Apr 10, 2007
Messages
14,105
Location
Fresno, California
I have always had the dilemma of boats vs airplanes; it would be nice to combine the two. If for some reason I could not mess around with airplanes, I'd be living on a boat by now. Yes, coconut oil - I guess I could fly from one Caribbean resort to the next, taking their used cooking oil off their hands and have an onboard refining system or set up the engines for SVO operation! Until I get to Venezuela and I can fill up for 7 cents a gallon.
Do you remember an old, short-lived TV show called Tales of the Gold Monkey? That one gave me similar thoughts of a gallivanting South Seas lifestyle.
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,686
Location
Corona CA
Do you remember an old, short-lived TV show called Tales of the Gold Monkey? That one gave me similar thoughts of a gallivanting South Seas lifestyle.
Ah yes, I remember it well - and doesn't it make real life seem a little dull?
 
Top