Hi Karl and company,
I helped perform the wing static bending test along with Gitas Tamulaitas, Jim Maupin and some others whose names I can’t come up with right now. Jim used 150 pounds for the pilot weight and 5 g’s for the high AOA limit load test. The wing deflected about 1.5 feet at the tip and the upper skin had elastic buckles about 2 inches deep from crest to trough in between the nose ribs. I don’t remember any pops or other noises and the wing came back to the same position as close as we could measure it.
The prototype Carbon Dragon was designed to set records as a class O-2 rigid wing hang glider. The pilot was going to be Rich Pfeiffer, who actually weighed slightly more than 150 with a chute. Since the glider flew so well (and because many of us have gotten so big), this decision to limit the useful load has had long lasting effects for a series built design. I weighed 210 pounds before clothes and a parachute when I was flying it, so the margin of safety was pretty darn thin. I think what you guys have been doing with increasing the spar strength using carbon rods is an outstanding idea. Steve Arndt probably hasn’t had to worry as much as I did when I was testing the prototype.
I really don’t think the wing needs to be made any larger in span or area. The wing carries the weight very very well. Steve’s Magic Dragon has a slightly larger span, but it is very hard to keep the weight under 155 pounds for a Part 103 unpowered ultralight. If you increase the load limit to CS-22 type requirements (5.3 g limit and 242 lb min useful load), you will be doing very well to keep the current span and area. If you don’t plan on foot launch and landing, the wing area could easily be made smaller, which will help with the weight.
Best of luck with these interesting developments,
Dan Armstrong
From: This email address is being protected from spambots. You need JavaScript enabled to view it. [This email address is being protected from spambots. You need JavaScript enabled to view it.] On Behalf Of KarlS
Sent: Sunday, February 05, 2012 5:46 PM
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Subject: [Carbondragonbuildersandpilots] Re: Carbon Dragon structural limits
Hi Kenny and all,
In the article it states the design has been proof loaded to 5g and has a 7.5 g ultimate design. It does not mention pilot weight but it does say the pilot that did a lot of the initial testing weighed 210 lbs with parachute. Dan Armstrong was his name. I'll scan the article and upload it for you guys.
Karl
--- In This email address is being protected from spambots. You need JavaScript enabled to view it., Kenny Andersen wrote:
>
> Karl,If the old construction method could be loaded to 5gs, then the rods should have no problem boosting that up significantly. The other problem is that 5gs at what pilot weight? So, that's why Phil and I were working on the calculations for using the rods. I'll probably never be below about 185 and often float upwards of 200. Using a pilot weight of 200-220 really doesn't make much difference with regard to the structural weight, especially with the carbon rods, so why not? It would be interesting to look at the original test though... I think with the increased pilot weight, the tail boom ought to be a little longer to give it a bit more authority... That;'s why I didn't want to change the design so much. If you sale the wing dimension up about 7% (*which isn't so much) the area goes up around 14%, which will increase payload significantly. Also, the root gets a little deeper, so the increased moment doesn't mean SO much to the spar
> cap and attach fitting loads. I don't think it should bee too big a deal to do, and I would do that if I built one (since I'd want to actually fly it!).
