Under-Surface Battens

[Ward Odenwald]

Last Wednesday at the Pulpit, I flew a new Sport 2 155 for the first time and I noticed a sail fluttering/flapping noise when I flew fast but was unable to visually locate the region of the sail that was creating the noise. The wing tips looked okay (no flapping) as did the outer half of the trailing edges but I was unable to get a good look at the sail directly above me. The wing tip photos also did not reveal any significant issues to my untrained eye and the upper surface cambered battens were okay too - no issues detected during the preflight.

Yesterday evening, I assembled the glider and noticed something that may, or may not, have been the cause of the flapping but I realized that other pilots may benefit from what was found concerning the glider’s undersurface battens. On this Sport 2, if the undersurface battens are inserted so that the aft end of the batten is tucked in the end of the pocket and not projecting out of the pocket (first photo), their forward ends do not extend far enough to reach the undersurface of the leading edge at any VG setting, however if they are pushed deep into the pocket using a pencil or other instrument the forward tips are positioned under the leading edge (second photo). On most or all gliders, undersurface batten pockets are open at the forward end to allow the forward batten end to project beneath the leading edge to keep the forward undersurface from curling up during flight. Without leading edge contact, there is no resistance/leverage for the batten to maintain optimal airfoil shape. The next series of photos show the aft ends of the inboard battens just before and during my flight and, as indicated by the hanging batten strings (arrows), their positions in the pockets are not deep enough to allow contact with the leading edges. Although the outboard undersurface battens are not in the photos they also do not extend to the leading edges as their position in the pockets is the same as the inboard battens and looking at the glider last evening, there is no batten - leading edge contact with these guys either. I’m guessing that this issue is the cause for the rippled undersurface shape that is evident in the in-flight photos. The only way I can get the battens to extend to the leading edges, as mentioned above, is by using the eraser end of a pencil or other blunt end tool to push the battens deeper in their pockets. The Sport 2 manual is not clear about how the undersurface battens should be inserted nor is there ANY mention of how they should be pre-flight inspected. In fact, the only comment about pre-flight inspection of battens (any batten) in the entire manual is the rather brief statement on page 19 “Check that all battens are properly secured.” My guess is that either the battens for my glider were cut to short or WW shipped undersurface battens for a smaller version of the Sport 2. Whatever the cause, my hope is that everyone confirms either visually or by pushing up on the undersurface where the batten should meet the leading edge during preflight to insure that the batten tips are making contact with the leading edge. If you have to push the batten deep into the pocket to reach the leading edge, there is no guarantee that they won’t move aft and away from the leading edge during flight. I’ve contacted John M and hopefully soon either he or WW will advise. Ward

PS – if I’m wrong about the necessity of the batten reaching the leading edge, please post.

[FlyingFelix]

I would think undersurface battens don't need to go all the way into the Mylar cover of the leading edge, as long as they are still seated under the leading edge tubing when they are pushed all the way back in the end pocket. If they don't reach the leading edge there may be a problem.
That said, I noticed my old Sport 2 would sometimes have the undersurface battens pulled (fallen) a good bit out after a long, rough mountain flight (before WW finally changed their designing for the undersurface battens) and I can't say it fluttered or that I noticed a difference in handling.
I did appreciate the "new" feature of batten end pockets on my Discus glider (made in '04)

[Matthew]

Ward,

Is this just a ploy so that you can show us more photos of your glider?

Matthew

[Ward Odenwald]

Insightful Matthew, I was hoping that you would have also critiqued my color coordination as it’s got to be better than your previous assessment of the other harness/glider combo. I have to admit that I could have accomplished airing my concerns about the battens without the flight photos. To my credit, I only padded the post with three. On a more serious note, correspondence with WW via John Middleton about the undersurface battens is not yet settled. WW admits that their Sport 2 manual is outdated and their instructions for the undersurface battens (in both the hardcopy that arrived with the glider and the PDF currently online) are for an earlier version of the glider that had different undersurface batten configurations - what else is outdated? They also indicated that the aft-end of the undersurface batten position for the current glider (shown in my first photo) is the correct position. Of interest and somewhat curious, WW states that the flight performance of the Sport 2 is not affected if the undersurface batten length is changed “+/- one inch”. If the inboard undersurface battens for my Sport 2 were increased by one inch, the battens would extend under both the crossbar and the leading edge. So far, there’s no clarification on the flight characteristics of the glider when both the crossbar and the leading edge support the undersurface battens. I have to believe that if the undersurface battens are supported by both - the shape of the undersurface and its flexibility is significantly different than if the battens are only supported by the crossbar. Could be a trivial concern but could also make the difference between making a distant LZ or the trees. Ward

[Ward Odenwald]

WW (via John) replied, that since ~1982 the undersurface battens on ~20,000 Sport 2s have never had any direct support for the front of the undersurface batten from the leading edge tube and that the solution to improving the cleanliness of the bottom surface is to tighten the keel pocket strap and adjust the upper surface root batten tension. Twenty thousand, that’s a remarkably impressive stat/accomplishment. Thanks for your help John.
Ward

[theflyingdude]

WW (via John) replied, that since ~1982 the undersurface battens on ~20,000 Sport 2s have never had any direct support for the front of the undersurface batten from the leading edge tube and that the solution to improving the cleanliness of the bottom surface is to tighten the keel pocket strap and adjust the upper surface root batten tension. Twenty thousand, that’s a remarkably impressive stat/accomplishment. Thanks for your help John.
Ward

I doubt they were referring specifically to the Sport 2 as they didn't exist in 1982. While I love my Sport 2 155 and they're a very popular glider, if they'd made 20,000 of them, the delivery time would have been a lot longer.

JR

[krryerson]

Ward,
I do fly Felix old WW Sport 2, made in 2007 and did check the under surface batten pockets on my wing today. It turns out that on my Sport 2, the surface batten pockets are not open at the forward end. This does not allow the forward batten end to project fare, fare beneath the leading edge like on your wing.
(I wish I had a picture of it... .)
Knut