The La Mouette Topless 2 on take off on tow
Longtime Cross Country contributor the hang gliding writer Dennis Pagen reviewed the Topless 2 in 1999
The very first hang glider to dare to go topless was the La Mouette Topless. Owner/designer Gérard Thévenot went all the way with a graphite crossbar and sprogs which have become the standard of all modern gliders without kingpost and upper rigging.
We reviewed that glider three years ago, but hundreds of production gliders with thousands of flight hours later have brought about some changes that offer improvements. Handling, performance, safety and convenience have been enhanced on the Topless II.
Let’s discover what this reworked wing has to offer.
I was fortunate to be loaned a new Topless II to fly in the back-to-back Florida tow meets last April: The Wallaby Open and the U.S. Nationals. I tallied up 41 hours in the two weeks there. I flew in all kinds of conditions, from strong winds/light lift to light winds/strong lift. I did about everything you can do with a glider. Here are my impressions.
The Topless is a kingpostless glider that spawned a generation of similar designs. It may thus appear generic at first, but it has a few interesting features that bear closer scrutiny. It has a long elliptical wing with a curved tip. The aspect ratio is 7.6 (comparison of span to chord) on the 13.5 model, 8.0 on the 12.8 model and 8.8 on the 11 metre. The model numbers refer to the area in square metres (see the spec chart for English units).
The airfoil is pretty standard-hang glider with about 12% camber and a forward high point. It should be noted that La Mouette pioneered the forward high point airfoil with their Atlas in 1980.
Now look inside. You’ll see a carbon graphite crossbar with an interesting dip on the outboard end. The purpose of this shape is to raise the crossbar up a bit to allow the under surface to camber upward. The idea is to improve sink rate by increasing the wing’s airfoil mean camber.
The curved tip wand has a slight departure from the conventional in that the attachment cam separates from the sail and is placed on the wand before any tension is applied. Then you bend the wand and slip the cam onto a pin through the sail and finish by swinging the cam lever forward. Detaching the tip wand is extremely easy once you know the trick: simply pull the cam in away from the sail.
In my estimation the attachment of the wands take the same amount of effort as other cam-equipped curved-tip gliders, but the detachment is easier with the Topless’ system. The tip cams have certainly made curved tip attachment much easier and they have enhanced the use of curved tips on a glider. It’s amazing that we struggled for over a decade without them.
Another point to note is the spring-loaded battens. Most pilots are familiar with these convenient items. A spring in the rear of the batten pushes back against the trailing edge of the sail through a tab that fits in a slot in the sail’s hem. In this way batten tension is maintained, all those messy (drag producing) battens ties are eliminated and setup is easier.
The Topless style rear batten ends have a tab that sticks down to help you put it in and out. I think this is unnecessarily draggy and would cut this tab off my personal glider if I were obsessed with drag (as most competition pilots are). I prefer the cleaner plug used on the Bautek Twister. Incidentally, La Mouette pioneered the production use of spring-loaded battens.
We’ll note two final facets of the design before we review the changes that rejuvenated the Topless II. First up we have the thin but adequately strong base bar. It is equivalent to about an inch (2.5 cm) in diameter. The bar is well padded for grip and is made thin to reduce drag. It attaches with a PIP pin for quick setup.
The other item is the extremely clean and simple crossbar haulback attachment point at the keel. A small, flat D ring slips over a little slotted cylinder. A spring-loaded detent pin secures the ring in place. The whole arrangement leaves nothing visible but the haulback strap and there is nothing to damage the sail during folding.
CHANGES IN THE AIR
Now we’ll detail what’s new. A couple of the items are structural: The control bar uprights are now attached directly under the keel so they fold easier and avoid damaging the sail during breakdown.
To accommodate this change the VG line is routed right through the keel providing a cleaner system and less friction. The VG line can also be routed in the front or rear part of the safe-edge airfoil upright. The rear is better for ease of VG working, but if you use an instrument clamp on the rear portion the upright rubber will compress and squeeze the VG line, so you can route it in the front of the upright.
The VG system is not the lightest available, but it’s not bad. It usually took me 3 pulls from full off to full on, but note that the crossbar has a lot of performance-providing travel.
Another structural change is the arrangement of the sprogs (the inboard minimum twist struts). They have been moved out to the leading edge from their original crossbar position. Now they attach to a pivot below the leading edge and are held at the proper tilt with a cable from the top of the leading edge.
The cable’s relative length can be easily adjusted with a screw for proper sprog setting (stretch and wear can alter sprog settings). The new sprog setup is stronger and more effective than that of the previous model.
Long zippers at the sprog and the outboard minimum twist strut (defined tip) allow easy access to the interior of the sail. This feature is a boon if you ever have to perform maintenance or repairs.
The next items are sail changes. A new leading edge luff curve, wider Mylar inserts and an additional batten has been added to the glider. The different luff cut is responsible for improved handling and the batten cleans up the tip for ostensibly better glide performance. Furthermore, a new airfoil at the tips has improved handling and performance (we’ll discuss both of these matters later).
The final new item is the tail. You’ve probably seen them by now, rendering our flying wings more of an appearance like sailplanes. The tails used on kingpostless gliders are small, light affairs that swivel at their leading edge so they don’t affect flare, but they stop at a minimum angle of attack to greatly dampen a pitchover excursion. In this way they work the same as and add to the effectiveness of the defined tips (washout struts) on our gliders.
The Topless tail attaches to the keel with a pin that holds it to a U-shaped bracket. The bracket itself attaches to the keel with another (easily removed) pin.
La Mouette states the tails weighs 650 grams (1.4 lbs) and claims it offers an improved pitch-up coefficient, better pitch dampening and a gain in performance. Hmmm… let’s look at this performance factor.
With the addition of a tail, the sprogs on a topless glider may be lowered, because the tail takes over some of the sprog’s job. The tail is way behind the center of mass (and pressure) of the system, so it can do its job with less drag producing effects at higher speeds.
That’s why sailplanes use small tails set far back from the wings. Lowering of the sprogs, however, is an inexact science and I have yet to see a manufacturer publish a separate setting for use with a tail.
In view of the above, my take on the tail is as follows: If you set your sprogs properly (lowered from the tailless factory setting, but not unfunctioning) you will achieve a better glider at the higher interthermal or wind penetrating airspeeds.
Sprogs rob this upper end performance by holding twist in the wing. On the other hand there is likely a very little small detriment to your maximum glide which occurs at a much slower speed (around 27 mph or 43 km/h).
Finally, there are a few competition pilots who believe the Topless II with a tail achieves a better rate of climb in thermals than without it. The reason for this is that they feel they can push way out (slow down) without worrying about the pitchover problem. During the Florida meets, a couple of pilots experimented with and without the tail and ended up sticking with it.
Sure, the tail adds a bit of weight and a bit of hassle -you have to carry it separately- but if it gives an increment of performance advantage, pilots will want it. My recommendation for the Topless II is to use the tail in competition but not for recreational flying.
TOPLESS II PERFORMANCE AND HANDLING
Let’s segue right into performance since that’s what attracts most people to a new glider. At the low end, the Topless seems to excel. I have witnessed a good pilot flying a Topless climb through one of the world’s top pilots flying another design. I certainly didn’t feel outclassed in climb except by my own limitations.
One of the secrets to good climb is to be able to slow down in thermals so as to fly as small a circle as possible at a given at a given bank angle. Curved tip gliders with their flexible twist outboard seem to do this exceptionally well.
The Topless II can be pushed way out in a normal 30E bank if the thermal isn’t too rough. There is no tendency to stall the inside wing and drop. Slight imperfections in the thermal merely wobble the wings. Of course, if the thermal is nasty or traffic nasty you have to carry a little more speed, but the potential for great climb performance is there.
In glide the Topless equals the other hot ships out there that were set up in a similar manner (that is, within the manufacturer’s production specs). At best glide there isn’t a lot of difference in the current gliders, but at higher speeds, some differences do appear. Again the Topless holds its own in this regime. I felt I was gliding on the upwind struggles like other pilots in similar category gliders.
The factory claims a 6% improvement in glide over the original Topless. Factory claims are always open to debate, but I have watched Gérard test his gliders by towing them very high side by side then gliding for a 1000 m (3000 ft) loss and measuring the difference in height. Repeated trials such as this give as accurate comparisons as possible. So if he said 6%, I believe 6%.
Handling is part of performance, so let’s review that here. The Topless does not initiate as effortlessly as the Laminar or CSX, but it has a very positive and predictable feel to it. After all the airtime in the Topless II I went home and flew my Klassic on some XC flights. I have always liked the feel of the Klassic (predictable and reasonably light) but must confess I liked the Topless II better.
The main difference was that the Topless wouldn’t catch a wing as much in varying air. Also, as mentioned previously, you can push way out on the Topless without getting surprised. Try that on the Klassic and you stall a wing and get spit out of the thermal. Once you’ve established your thermal circle the Topless II coordinates nicely and only requires little inputs to adjust to elusive cores.
With the VG on, the Topless II doesn’t handle any better than a trolley car. That’s fine by me because I want the maximum glide performance I can get between thermals which means a very tight, stiff wing. I learned to back the VG off to about half when approaching a thermal as indicated by other climbing gliders or bubbling air. Then by keeping my finger on the line I could pop it off the rest of the way when I hit a core I wanted to claim as my own.
I found that I could keep the VG on if I wanted to do a couple of turns in light stuff to top out. In addition, I would often put some VG on at the top of a climb in preparation to leave through the sink. Sometimes the thermal would turn on again and warrant some more circling. As long as it wasn’t rowdy, the glider behaved well with VG up to 3/4 on.
My conclusions in performance matters: the Topless II is second to none in circling sink rate. It is one of the top 2 or 3 all-around best performing gliders. The handling is reasonable good. It has a very comfortable feel and you don’t get surprised even if you are stretching to wring out the last shred of lift in a thermal.
It is significant that the Topless won the last World Meet (piloted by Guido Gehrman) and 42 of the competitors at last summer’s Pre-world meet flew La Mouette’s Topless.
TAKE-OFF AND LANDING
The Topless II takes off similarly to other gliders of its type and weight. There are no tricks or special techniques. The side cables are slack as with most gliders like this. As soon as you start moving the wings lift and the glider seeks the proper pitch. Accelerate and you’re airborne, ready for a climb.
Landing is likewise straightforward. I had 16 flights (and landings) and dropped the nose twice. One of these was in a slight tail wind on a switchy day. The Topless loosens up considerably with the VG off, so it doesn’t retain speed excessively. A gentle early flare works fine except in a tail wind or when landing downhill. I also landed the glider with the VG nearly full on a couple of times and had no problems.
Conclusions: the takeoff and landings are conventional and easy for a glider of this type provided a pilot is used to high performance gliders. Incidentally the glider behaves very predictably in diving (slipping) turns which helps you land in smaller areas.
SETUP AND BREAKDOWN
The Topless II sets up just as easily and similarly to other gliders of its class. There are several points I will mention. The sprogs are held in position by Velcro tabs that take two hands to place properly. I would prefer a loop or snap that would be quicker.
The lower battens have bungees which aren’t really effective (they are loose) and probably not necessary. I quit fiddling with them after the first couple of flights. I hope some manufacturers pick up on Airwave’s method of sewing the lower surface pocket tight at the end to hold the battens without ties or Velcros.
Finally, the washout struts could use some Velcro in their ends to hold them to the leading edge when you are rolling the sail. They have the bad habit of springing themselves open into position (they are held with bungees) and then they are hard to get out with the sail detensioned.
But these are minor points. What I like about breakdown and setup is the keel kickstand. The keel end pops out to hold the rear up which greatly eases the placement and pulling of battens. If you’re old enough to remember Elvis, your back will appreciate this feature. Of course, the spring batten fixtures makes the whole batten hassle a bit easier.
The Topless hardware is convenient for the ground mechanics of flight. PIP pins hold the nose cables and basetube. The side cables are 1×19 wire which doesn’t need coating and tangles less than the more supple 7×7.
OPTIONS AND PRICE
There are three options that are worth mentioning. The tail which retails for $350, the Matrix Mylar sail cloth ($300 retail) and the carbon faired (streamlined) speed bar ($300 retail). The speed bar promises less drag and the Matrix sail promises better glide performance.
One test pilot of a competing manufacturer even claims better handling with the Matrix sail, although I doubt if this is true across the board since the material is stiffer than conventional Dacron. A new Topless II will cost you $5,600.
Updated January 2011
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