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TOPIC:
Re: CDII -fuselage 09 Dec 2013 00:46 #401
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Don't get your hopes too high
--- In This email address is being protected from spambots. You need JavaScript enabled to view it., "Jan & Dan Armstrong" > > 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 > > > > <Yes I agree 155 is to heavy to foot launch. However the ULF-1 is foot > launch able. I think a steady wind to help lift the aircraft is what makes > it possible. To do it <once classifies it as footlaunchable. > <I'm just saying to do it just to do it. Once. The pilot has to be on the cg > like the Archaeopteryx then. I'm all for roll launching. > > <A 100 % composite under 155 is going to be tough. I agree. I have a lot of > samples of different layups. I measure my sample in 6" by 6" squares. 14 to > 16 grams <for a 6x6 is pretty light for composite sandwich layups. Do we > have the sq ft surface area of the CD? Multiply that by 60 grams and you > have a composite skin <weight. That's without load carrying spars, etc. > > <Karl |
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