Princeton Sailwing

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

D

Dick M.

Guest
Beside the Zipper (Chris Heintz) and the PeeWee project (Dennis Harbin), are/were there other ultralights using the Princeton Sailwing principle?
Or, in other words: reading the NASA and the Princeton reports it seems, that the sailwing could be a interesting base for real ultralights.
Who knows more?

links:

NASA http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690009905_1969009905.pdf
PeeWee: http://www.oshkosh365.org/saarchive/eaa_articles/1983_03_05.pdf
Princeton: http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0275307
 

Inverted Vantage

Formerly Unknown Target
Joined
Jun 19, 2008
Messages
1,116
I know this is a super old thread but I've been fascinated by this planform for a long time. I've been trying to build a scale model to test out some ideas, but I have no way of attaching the wing to the fuselage, and was wondering if anyone had any ideas or thoughts concerning this problem?

What I have so far is this board with holes in it, and a bit of sailcloth with eyelets that would get "sewed" onto the board with string.

Just curious if anyone has any better/stronger ideas?
sailwing.jpg
 
D

Dick M.

Guest
I know this is a super old thread but I've been fascinated by this planform for a long time. I've been trying to build a scale model to test out some ideas, but I have no way of attaching the wing to the fuselage, and was wondering if anyone had any ideas or thoughts concerning this problem?....
Hi Inverted Vantage,

1. Why don't you use a root-rib?
2. Perhaps the NASA TN D-5047 can give you some ideas (chapter "Introduction" and chapter "model and tests" etc.):

NASA Technical Note D-5047: FULL- SCALE INVESTIGATION OF THE AERODYNAMIC CHARACTERISTICS OF A SAILWING OF ASPECT RATIO 5.9

"http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690009905.pdf" (search without ")

Introduction: "... This type of wing uses a single spar as the wing leading-edge and main load-carrying member, ribs only at the tip and root, a wire trailing edge stretched between the ribs, and a fabric envelope to form the wing surface....."

3. See also the ideas of Denis Harbins Pee Wee:

https://www.google.ch/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0ahUKEwiv_pnA_ojOAhXM2SwKHZ35CiIQFggxMAM&url=https://xa.yimg.com/kq/groups/1829523/1091464082/name/Peewee.pdf&usg=AFQjCNFLbPQJhgzaNLd9t3CAOdgDQZXidg&cad=rja

Dick
 

Inverted Vantage

Formerly Unknown Target
Joined
Jun 19, 2008
Messages
1,116
Hey Dick!

Thanks for the suggestions. :) I had forgotten about the root rib, I was hoping to do away with it since it was scale. I've taken a look at the PeeWee, but unfortunately the author never goes into detail on the way the wing fabric mounts. I'm thinking now that a sock with a zipper on the root side might be the best bet. Thanks for the tips!
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,524
Location
Corona CA
I have also been doodling with this concept and thinking it through for years. A few difficulties came to my mind:

Roll control. I thought about using a wing root rib and actuating that like the boom on a sailboat. Doesn't strike me as efficient, but maybe doable. Thought about adding a solid foam/glass tip section, maybe a couple of feet, long that would pivot on the spar, but running cables/rods/torque tubes out there ruins the simplicity of the idea. Two axis control would get around that, but I'm no fan of that.

The second difficulty I can foresee is getting the two sails exactly the same as far as shape and tension goes. Likely they will develop some sag and a means must exist to fine tune them.

One structural problem is that you need to brace the wing fore and aft; in their test models this was done using two lift struts in an inverted V configuration. Seems inelegant, but works. You can't really run a drag brace aft without going through the sail (a big hole perhaps, but again, inelegant).


The results they got with this whole concept seem so overwhelmingly positive that it really begs to be made into a workable ultralight.
 

Jon Ferguson

Well-Known Member
Joined
Dec 15, 2011
Messages
827
Location
Harpers Ferry, WV
If you apply an expansion element which creates tension in the web to flatten it alternatively each wing would create lift differently and could act as a roll mechanism.
 

ARP

Well-Known Member
Joined
Nov 24, 2009
Messages
309
Location
Darenth, Kent / England
Allow the sail to float across the keel with weight shift to change the billow gives the required roll. Flexwing hang gliders and trikes use this principle but also use wing ribs to better define the aerofoil section.
 

Riggerrob

Well-Known Member
Joined
Sep 9, 2014
Messages
1,410
Location
Canada
There was at least one ultralight airplane, single-tube fuselage with Sailwaings mounted on top .... open cockpit ... heck! It did not even have a cockpit, just a seat sitting out in the breeze.
A couple of seaplanes with Princeton Sailwings flew back during the 1970s. They had twin floats glued to a Brunelli-type lifting fuselage. The first version had the pilot's head protruding from the top of the wing center-section, with an inverted Y-tail on the end of a single boom. It was designed to tow behind a speed boat.
The second Flightsail was big enough to enclose a pilot and passenger inside the lifting-body fuselage and it had twin rudders mounted on the ends of twin booms. Two sets of wings were offered: Sailwaing or conventional strut-braced. Curvature of Sailwings matched the curvature of the top of the fuselage. It could still be towed behind a speed boat but plans also showed a Continental C-90 mounted on twin pylons similar to a Volmer Dportsman. Both Filghtsails were featured in Sport Aviation magazine and plans were even sold for a few years. Really wish that I had bought plans back then.
Does anyone have a set of Flightsail plans they would be willing to trade for dollars?

Last thing I read was circa 2000 when Sport Aviation magazine featured a conventional floatplane by the same designer. Does anyone have a copy of that issue?
 
D

Dick M.

Guest
Roll control. I thought about using a wing root rib and actuating that like the boom on a sailboat. Doesn't strike me as efficient, but maybe doable.
Good idea. And don't forget: with a typical Princeton-sailwing shape (see below) you will move a fairly great surface with that system!

The second difficulty I can foresee is getting the two sails exactly the same as far as shape and tension goes. Likely they will develop some sag and a means must exist to fine tune them.
Why don't you connect the trailing-edge cables with a pulley guided spring

lateral_movements_004.jpg

Dick
 
Last edited by a moderator:

Inverted Vantage

Formerly Unknown Target
Joined
Jun 19, 2008
Messages
1,116
For those that are interested, here's the scale R/C model I'm building to test the concept with an actuating wing root:
wingroot.jpg
 

Jay Kempf

Curmudgeon in Training (CIT)
Lifetime Supporter
Joined
Apr 13, 2009
Messages
3,907
Location
Warren, VT USA
Seems the tip rib needs to move for aileron. Is this concept supposed to both elevator and aileron functions from the root with a fixed tail position?
 

Inverted Vantage

Formerly Unknown Target
Joined
Jun 19, 2008
Messages
1,116
Just the aileron, though this does provide for some interesting flap concepts. Getting the tip to move is a lot harder than moving the root, so I'm testing to see if the latter can perform the function. Once that's done I can try and get the tip to move, but I don't know a simple mechanical linkage to allow that to happen, without mounting the servo on the wingtip - which might actually be fine, minus the extra long cable. I've already started assembling this, so that will probably be in V2 along with anything else I learn. :)
 

Inverted Vantage

Formerly Unknown Target
Joined
Jun 19, 2008
Messages
1,116
The tail just came out of the printer today. The different colors are due to different resins used - the dark blue is v1 of Formlabs Tough (ABS-like) resin, the lighter green is v3. The tail had to be split to fit into the print area. The spots all over the surface are support marks that I haven't taken the time to sand down. The joint is a 2mm through-hole with a piece of FDM filament (basically weed whacker wire) stuck through it.
16106868_10154313665921647_825862347_o.jpg

I'll attach it to the tail boom today and finish putting together the fuselage probably this weekend. After that we just have to make the wings and wing tips and we're good to go! :)

If you guys are interested in the design you can check out the link to the Onshape document here. I'm pretty happy with how the tail structure turned out. I will be using the principle elsewhere. A friend of mine came up with it for composite wing construction: rather than making ribs, a "corrugated" internal extrusion (made up of alternating angled pieces to form a spanwise triangular structure) provides bending resistance. If I ever design a hard wing I will use this technique, and will probably use it for the next version of this aircraft which will include an enclosed fuselage (as opposed to the balsa/foam sandwich plate this one has).
 
Last edited:

Topaz

Super Moderator
Staff member
Log Member
Joined
Jul 29, 2005
Messages
14,109
Location
Orange County, California
... The second difficulty I can foresee is getting the two sails exactly the same as far as shape and tension goes. Likely they will develop some sag and a means must exist to fine tune them....
I believe this was the issue that sunk the EAA's little Princeton Sailwing biplane effort back in the '80's. Even letting the sun shine on one set of wings and not the other was enough to induce a roll trim issue, since the entire wing on each side is affected.

You'd need some way to constantly keep the tension the same on both sides. Automatically.
 
D

Dick M.

Guest
..... I'll attach it to the tail boom today and finish putting together the fuselage probably this weekend. After that we just have to make the wings and wing tips and we're good to go! :)
Do you have news for us ? ;-)

PS here one more link to the "Princeton sailwing theme": https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790015726.pdf
".... Because of its light weight, simple construction, and good aerodynamic performance, the Princeton sailwing may be a competitive alternative to conventional wings for many lowspeed applications such as ultralight sailplanes, man-powered aircraft and high-performance hang gliders. The operational characteristics of the sailwing are discussed with some emphasis placed on the importance of the trailing-edge cable tension as it controls several aerodynamic
properties
....."
 

danmoser

Well-Known Member
Joined
Feb 1, 2010
Messages
641
Location
Sandy, Utah, USA
I've been intrigued by the Princeton sailwing for many years.
The technical papers on it are very interesting, but I would really like to find out the results of it's implementation in aircraft.
There was briefly a sailwing hang glider produced and offered for sale in the mid-70s, but I never heard how it flew, or why the company and aircraft disappeared so quickly.. it was all flexwings and rigid wings on the hang gliding scene after that.
Same situation with the Zenair Zipper.. it arrived on the ultralight scene with great fanfare in the early 80's, then seemed to quickly disappear without any information as to why.
The Zipper used external airfoil ailerons hang off the trailing edge cable for roll control, but many were claiming that differential tension actually worked better..

Can anyone describe the problems that arose in actual flight testing of these old sailwing-based aircraft?
Was it a lack of performance, sail longevity, control problems, accidents ??? :para:

A lot has changed since those early days.
We now have modern composites materials, much better sailcloth materials, electric propulsion, and powerful & accessable computer simulation tools.
As we all know, the current ultralight market could benefit from designs with better portability, lighter weight, and lower cost.
Maybe, just maybe, the sailwing concept could be successfully revived and find a niche there.
 

Victor Bravo

Well-Known Member
Joined
Jul 30, 2014
Messages
7,291
Location
KWHP, Los Angeles CA, USA
Bugs the crap out of me that the people at Princeton didn't even mention the Platz glider, not even briefly in their "introduction" page. Not to say that they based the Princeton glider on Platz' sailwing, obviously they didn't, but my issue is that they did not see fit to even address what had come before in this type of wing.

FWIW, I don't believe that a pure rib-less sailwing would represent a significant alternative to what is available in the current hang glider world. Yes there will be a small cost reduction (by not having the aluminum tube ribs that the HG's have), but IMHO the weight and cost benefit of a rib-less sailwing would not outweigh the aerodynamic benefit that the ribs/battens provide on a modern HG wing.
 

Aesquire

Well-Known Member
Joined
Jul 28, 2014
Messages
2,402
Location
Rochester, NY, USA
One of the reasons the sail wing concept didn't take off :) was the tendency to get cusps in the sail at the trailing edge cable. This produced high pitching moments, somewhat unpredictably.

A modern interpretation with flexible and rigid battens as well as sewn fabric ribs would be quite workable. ... and that's what modern ( 1980's on ) hang glider & trike flex wings evolved into.

The Princeton design didn't so much fail, as was a moment in the evolution of modern "sail wings". Consider it to be an early and flawed winged dinosaur that passed on some characteristics but was left behind for a reason.

Several features were ahead of it's time. The double surface airfoil, truncated wing tips establishing washout, several design elements are in use today, if not readily apparent.

Even the bowsprit design had a period of success, briefly, in hang glider evolution. Like a Sopwith Camel, the many bracing cables gave light but draggy strength and have passed from the mainstream of aviation. I will say they were feather weight compared to the more cantilever wings that replaced them. I've kept an eye out for old ones but they are almost never sold, because they don't meet modern stability standards. So they rot in attic and garage corners like many obsolete gliders.
 

danmoser

Well-Known Member
Joined
Feb 1, 2010
Messages
641
Location
Sandy, Utah, USA
One of the reasons the sail wing concept didn't take off :) was the tendency to get cusps in the sail at the trailing edge cable. This produced high pitching moments, somewhat unpredictably.

A modern interpretation with flexible and rigid battens as well as sewn fabric ribs would be quite workable. ... and that's what modern ( 1980's on ) hang glider & trike flex wings evolved into.

The Princeton design didn't so much fail, as was a moment in the evolution of modern "sail wings". Consider it to be an early and flawed winged dinosaur that passed on some characteristics but was left behind for a reason.

Several features were ahead of it's time. The double surface airfoil, truncated wing tips establishing washout, several design elements are in use today, if not readily apparent.

Even the bowsprit design had a period of success, briefly, in hang glider evolution. Like a Sopwith Camel, the many bracing cables gave light but draggy strength and have passed from the mainstream of aviation. I will say they were feather weight compared to the more cantilever wings that replaced them. I've kept an eye out for old ones but they are almost never sold, because they don't meet modern stability standards. So they rot in attic and garage corners like many obsolete gliders.
Thanks for the reply, Aesquire.
Can you share any reference documents on the "tendency to get cusps in the sail at the trailing edge cable" phenomenon that "produced high pitching moments, somewhat unpredictably" ??
I'd be very interested in learning exactly how, when and why that phenomenon occurred .. whether it was inadequate sail tension control, stretchy sailcloth, etc.

I generally agree with you and Victor Bravo that the Princeton Sailwing as is would not be competitive with modern hang gliders & ultralights on a pure performance basis...
Battens (AKA ribs) provide excellent airfoil shaping for higher L/D..
However, a battenless sailwing may be advantageous if applied to a quick-folding ultralight that stores in a small fraction of a hangar, and could be unfurled and ready-to-fly in about a minute.
Flexwing trikes require a lot more time for batten stuffing & securing.

My interest in a battenless sailwing is mainly for an in-flight wing deployment system, where batten stuffing wouldn't be possible, and high airfoil L/D not necessary.
 
2
Top