Dan,

I’ve been thinking that perhaps the cockpit structure could consist of a couple of box beams on either side of the cockpit that converge and get shorter and narrower at the nose. This might support a diverging design for either a couple of wheels like the Axel or a single keelbeam that could be straddled at launch and then slid on during landing, like the ULF-1 (or maybe with a couple of small wheels attached by an axle that goes through the keelbeam). Either way, if the structure is on the sides, then the center could be flexible for whether you intend to foot launch or not. Who-ee though -- 155 Lb to foot launch would seem mighty ambitious! I’m 53 and run, cycle, weight train and swim, and I’m thinking that’s something that I wouldn’t even think about. You got bigger cajones than me!

The cockpit structure would of course be made compatible with the current wing, since I really don’t have the expertise to redo it. I’m guessing a few degree forward sweep from where it is at now would have a low impact on the handling, but should help a lot with the weight distribution. Ever seen winglets on a forward swept wing?




The flaps sound interesting, but all that complexity would be guaranteed to add some weight a system complexity. Did the model you flew in have the air brake like the magic dragon? Wouldn’t that be enough? I know it doesn’t seem as flexible or as sophisticated, but it would appear to be WAY simpler. There may be a difference on say a record-breaking version vs. the one everybody wants to flay around in…




I really like the Archaeopteryx too, but no way would the significant-other let me pop that much for a toy! She’d much rather I putzed around in the garage for a decade building one. Sill, what we are talking about here really is pretty much a deluxe hang glider…




As always, we appreciate and welcome your input.

Kenny


--- On Sun, 3/11/12, Jan & Dan Armstrong <This email address is being protected from spambots. You need JavaScript enabled to view it.> wrote:


From: Jan & Dan Armstrong <This email address is being protected from spambots. You need JavaScript enabled to view it.>
Subject: RE: [Carbondragonbuildersandpilots] Re: CDII -fuselage
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Date: Sunday, March 11, 2012, 10:56 PM




Karl and crew,



I have been following your interchange with great interest and would like to add a few comments:



The prototype Carbon Dragon was designed to set world records in the FAI Class O-2 (rigid wing hang glider) category. Jim thought that we would foot launch it once or twice, take photos or video in ideal conditions for documentation and normally ground tow it. During the flight testing, I never foot launched it, because it would have been very easy to damage the doors and aft pod structure. I didn’t want to have to repair it and it was very easy to launch in other ways. Gary Osoba described foot launching it a couple of times for short flights to support his world record claims. The issue was that you couldn’t even put the glider down by yourself without damaging it. Gary mentioned that it was pretty easy to foot launch and land in winds of 10 mph or more. After Gary submitted documentation to the FAI Hang Gliding Commission (CIVL), CIVL made a new category for hang gliders that could not demonstrate launch and landing in nil wind conditions (Class O-4). So far, the only world record in O-4 is for Nick Chitty flying a Super Floater in England . I believe Gary was awarded a few records in Class O-2 before the rules were changed, but can’t look up old records on the FAI site. None now survive, having been overtaken by Swifts and other rigids.



My main interest for a follow on glider to the Carbon Dragon is to meet both Class O-4 (foot launch and land in nil wind) and Part 103 unpowered ultralight requirements (155 lb maximum empty weight). I think this category of glider would be great fun to build and fly and allow setting world records. I also think the performance would be similar to the Archaeopteryx, but wouldn’t cost over $100,000 (or even $10,000) if built from plans.



I currently fly hang gliders and sailplanes and own a 195 Falcon 3 hang glider, a Schweizer 2-22EK for giving rides and an ASW-27 for cross-country flying. I like all of these gliders for various reasons, but still think that a good foot launchable ultralight sailplane would often be more fun and definitely more cost effective in many conditions.



I really like the pilot position of the ASW-27. It is roomy, very comfortable and offers excellent visibility (except for having to look through the canopy). All of the controls are easy to reach and adjust and the placement and tactile feel has been developed to a high level. I like the arrangement better than the PW-5 (and probably the Axel) because I can see better over the lower wing and back when circling. The PW-5 wing is a little too high and obscures more of your view. I would place the wing on an ultralight glider about like current racing sailplanes. This will require some forward sweep as you all have discussed to minimize weight and balance properly. There are many disadvantages to a forward swept wing. They are much more complicated and have some load cases that can be significant, such as structural divergence at both positive and negative loading. However, if properly designed, they can also have a little more taper without experiencing tip stalls than a straight or aft swept wing. This allows the wing to be thicker at the root and may allow reducing the spar weight and improving the roll response and roll rate.



The Carbon Dragon had poor glide path control for most of the flights that I flew it. On the last flight, I tested the spoiler and the glide path control could be called adequate. Most sailplanes have quite a bit better glide path control than the Carbon Dragon with spoiler. I think it is mandatory to have really excellent glide path control for a glider that you will fly cross country. I like the idea of having half span ailerons and half span flaps that can be camber controlled and will also go into crow configuration (ailerons up a little and flaps down a lot). My old HP-18 homebuilt sailplane had a mixer that allowed the flap handle to schedule the camber of the flaps and ailerons and it could be modified for crow configuration. The HP-18 could come down a one to one glide path without speeding up more than 60 kts and could touch down at a very low stall speed. I think something similar could be used on an ultralight sailplane.



As you have been discussing in this thread, the biggest problem is keeping the weight under control. With lots of attention to detail and good engineering and development, I believe the 155 lb maximum empty weight can be met, but will be tough. It may require more than one prototype to meet.



I really like the on going discussions and look forward to some flying ultralight sailplanes from those in this group.



Dan Armstrong