HiWind BunkEndCover Field Test: the pix First the pix, plain and simple. The first two show the king bunk's windward side under almost straight-on sustained winds of ~30mph _after_ I added numerous clips (see story below). The 2nd two pix show why I was there in the first place, and why this mod is vital to me. Most western windsurfing locations are absolutely shade-free and can be very windy. Here's what sailing looks like under ~30mph wind. This sailor is Don Pruitt of the Rocky MountainWindsurfing Association, on a maxxed out plane, probably sailing slightly under the windspeed. In the first pix he's sheeted out somewhat indicating he's probably been hit by a gust; perhaps he jumped just prior, judging from the wake. In the second pix he's pretty much dialed in. A heavy but very strong, expert sailor, he's probably on a ~6 sq. meter sail and a ~100 litre (floatation) board. Don's 6' tall; the mast is ~16'. The mast/boom/sail rig weighs ~15lbs; the board 15-20 depending upon what it is. I would be on a similar board and a somewhat smaller sail. Don's in the footstraps and hooked in to harness lines hanging off the boom, which carry his body weight against the sail's lift. He pushes that force through his legs/ankles/feet, controlling the hull's orientation on the water surface. This game is one of constant adjustment to variances in wind and water. And then: you have to turn around . . . Notice the whitecaps on the lake — which is totally placid and smooth sans wind. Wind of this strength agitates the entire water surface, resulting in jumpable swells and shore break which feels like the ocean on a moderate ocean day. Welcome to the Rocky Mountains :).

HiWind BunkEndCover Field Test: the report/phase 1 High WindProof Solar Bunk End Covers Field Test and Proof of Concept July 2003, Lake Hattie Wyoming (3 hours NW of Denver) This weekend proved to be one of the windiest experienced by Rocky Mountain Windsurfing Association members who frequent Lake Hattie -- meaning that winds ranged from zero to a sustained (for many hours) range of between 20-30mph w/ occasional slightly higher gusts. This lake has been known to "blow up", that is, offer (pelt) the local cows and cowering humans with much higher winds. The winds we did experience provided a solid proof-of-concept environment for this solar bunk end cover anchorage design. The design was a qualified success provided various conditions were met. I always knew that the essential design aspect was "anti-lift and anchor", that is, to limit any opportunity for wind to get under the cover and to securely anchor the cover in case it did. This is the reverse of what windsurfers want when the wind flows over the sail -- there we want lift and lots of it (same principle exactly as an airplane wing). Thus, a strong-wind lakeshore was bound to offer the exact real-world test I was looking for. The wind obliged. Ramping Up: Prelude I set sail one morning on a 9.6 square meter sail -- a large rig by recreational standards meant for use in winds of up to ~15-18mph max (pros sail up to 12M under much windier conditions; for reference a 9.6M rig uses a 17' mast). As it happened I experienced a rigging failure off the far shore, about 1.5 miles from my launch. I drifted back to that shore, beaching downwind about 1/2 mile from where I'd embarked, de- and re-rigged, and set sail back. Part way across the lake the wind suddenly grew and sustained to ~20-25mph (this is why Rocky Mountain sailing is so challenging), for which ~6-7M sails are suitable. Upon my delayed return, 3 hours after leaving, I rode ashore to the sight of my solar bunk end covers flapping around in this near-but-not-quite-malstrom. Both the short and long covers' windward edges (facing the wind) were completely unclipped from the tent edging; the covers were pushed about halfway over toward the shepard poles and were flapping wildly as the range allowed given their anchorage via the bonnet-end bungees. When this occurred the clips were spaced 12" apart on the windward and leeward sides and there were no clips on the bonnet ends. I can happily attest that: - the material used by Popup Gizmos is strong - the velcro join between the Jchannel and cover is strong - the bonnet-end bungee achorage scheme is strong (and is the sole reason the above two items were not subject to much more severe testing!) - the clips' grip is reasonably strong (only 1 clip ever disengaged entirely from the covers, even when flapping freely). NO structural damage whatsover accrued to any component of the system. The leeward side (away from the wind) is also totally prone to lift despite how well the windward side is anchored, although not as severely as is the windward side (more on this below) and so must be treated in like manner as the windward. In fact, all 3 exposed sides require heavy anchoring. The Facts in the Air: Anchors Not Aweigh 1. HWSBECs _require_ a full-width Jchannel or similar (awning bag) anchorage to the roof. The Jchannel must also tightly adhere; it's own gripping power is insufficient (more on this below). I velcro each end of the channel to the backside of the roof's bulb seal where the channel extends above the gasket and aligns with the U-channel that press-fits over the roof edge. 2. Minimum clip gap is 6" on all sides. On a Grand Tour Coleman camper this equals ~6 dozen clips. Clips should be applied to ALL THREE EXPOSED SIDES: windward, leeward, and bonnet (end). The goal is to give the wind nowhere to get a purchase between the cover and tent, for once it does lift occurs (and perhaps even venturi, where velocity increases as the volume of a moving mass is funneled into a reducing area -- something's got to give so it's velocity -- and velocity probably equals more lift in this zone). Once the wind does get a purchase its force inexorably works against the join, that is, each clip. Thus, the wind pries the cover loose clip by clip. When the leeward side gets unclipped it won't flap around but I believe that in a loose state it contriubtes to the instability of the entire system. On the bonnet ends the clip fingers orient over/behind the bulge of the bungee cord inside its fabric channel. Although the cover does not fold over the tent seam like it does to windward and leeward, the clips hold the two layers firmly together since a) the webbing provides good bite and b) the bungee bulge fills up the void in the center of each clip. 3. Interestingly, the cover/clip is bkown off of the tent seam as a unit; all but one clip out of 3 dozen remained clipped to the cover). Some number of rubber clip tips came off; I don't know if the exposed metal edges will have a detrimental effect on the cover into the future. 4. Thus the need for clips spaced every 6" -- even around the bonnet. I know this will perform in 30mph winds; I do not know if the spacing would need further reduction in higher winds. The accompanying picture shows the tenting deformed under a ~25-30mph wind load with the cover securely anchored every 6". I did not have enough clips to go around, but the several showing on the windward bonnet edge were vital in reducing the wind's prying force. 5. The windward/bonnnet and leeward/bonnet edges are critical. If the roofline is well-achored the system can better withstand a gap along the windward/leeward lines back by the roof; it cannot withstand any such gap at the bonnet corners. 6. Cover fit to tenting is critical...and mine could be better. I could use another half-inch all around. The system requires a very snug, but not taut, fit. Mine's taut. Tautness by definition pulls; this pulling force works against anchorage and as a partner to the wind. I believe tightly spaced clips tend to ameliorate, but not overcome, tautness. 7. Bonnet bungee tension should be a little harder than you think necessary. I increased my bungee tension by adding a knot behind each hook (my hooks, Coleman OEMs, are permanently attached; knots are a fine way to shorten the line). I have not discerned any adverse effect to the material -- which is being amply stetched anyway by the clipping force. 8. All this tautness pulls against the roof anchorage, hence the need for velcroing the Jchannel to the backside of the roof...even so, a corner of my king bunk end channel was pulling off and required manual intervention to reseat it. 9. The entire system may require manual intervention at any time depending upon conditions. I had enough clips to space 6" intervals on the windward sides, about halfway on the leeward sides, with just several clips remaining for the bonnet. So this field test stops short of anchoring the system in a manner which I believe may well practically eliminate the introduction of (significant) lift under the fabric. I do know that 6"-spaced clips endured on the windward side and that the leeward sides would still come loose despite 6" spacing windward. Still, every several hours I would happen to glance around and see a clip here or there loose, and so I reclipped them. In no case, after tightly spacing, did the scheme again grossly fail -- under the wind limits of this test. 10. These are strong little clips. Provided they don't damage the fabric after their rubber tips fall off (and they will), they seem to provide enough grab, if only just. Of course, the tighter the grip the more it can combat lift. But the primary goal must be to deny lift, and applying counterforce ought to be a backup design strategy. 11. I'm no engineer, but it seems that to the extent the weather allows, opening all interior tent flaps, allowing air to flow through the bunk ends, can only help lessen the force exerted against the system. Doing so also depends upon whether or not the camper is inhabited; in my case it was not (I was sailing) or it didn't matter to me. As an example of windforce do this test: try opening your camper door face into the wind with the storm panel fully up. Then lower it just one notch and open it again; notice how much easier it is to do. Previously I advised that devising this system was heavy on trips between the sewing room and the deployed camper, measuring tape in hand. A little extra fabric (but not much) is better than a totally taut fit; you'll be pulling to the snugness you desire rather than to a tautness required to fold the cover ends completely over the tent seams. The king bunk end is the wilier of the two since its length offers a much greater void eager to accept lift (it compares to the double bunk as does the 9.6M sail to a 7M sail). Several alternatives have come to mind: - stronger clips - zippers along the bunk edges - battens along the bunk edges, and I'm leaning toward experimenting with this. Battens are flexible fiberglass rods that stiff and shape windsurfing sails. Were I to sew batten sleeves along the edges and insert battens I suspect I'd need very few clips to prevent lift. Battens would be very quick to insert and remove and the sleeves would add very little thickness, so the covers could still roll up easily, battens inside, for stowage. Stay tuned. HiWind BunkEndCover Field Test: the report/phase umpteen Phase umpteen proceeded with battens. I'll also replace almost all the bonnet bungee with no- or low-stretch line. See this page for the result.

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