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Re: steve's dragon 12 Dec 2013 23:55 #764

hi kenny
when you do talk to an aero dynamist,run this by him

no horizontal stabiliser..stubby boom with fin/rudder...raise the flaperons up to create a reflex air foil.

id love a faviel plank type... under 70 kg...a constant cord one.

iv tried a lot of test pices...wood is a winner.....becaus of thickness to weight to compression to cost ratio...even when you take cost out its still a winner in relation to this glider.

give me an example of a modern core material and or a laminate you would use to replace any part in the dragon?
we will close the text books and i will tell you what the real world test results were.

the part in my last message i perhaps did not explain properly....in relation to spar caps,what the plans call for is in my opinion superior to extruded rods becaus of the fact that there is a join in our wings.....are you also aware that the standard spar caps are tapered?

just out of intrest i have a full size modern pod plug for my dragon on the bench.

russ,


On Mon, Jun 27, 2011 at 1:17 AM, Kenny <This email address is being protected from spambots. You need JavaScript enabled to view it.> wrote:


Russ, Thanks for the response,
I am temporarily out of the country working, so I don't have access to an aero-dynamist right this minute due to that (plenty of aeronautical engineers running around, but I would prefer a specialist). I do have access to probably all of the above when I'm home in the US (exact location will be a temporary mystery due to home security issues). Also, I know a pretty good dynamics guy who could probably help with the flutter issues (or at least check for that). Additionally, I could build a detailed FEM of the CD and also a reduced stiffness model for the dynamist to use.

This would be something I would do in the long-term anyway, not something I'm super hot on, only because 1) I understand the time commitment and 2) I have several projects lined up that I would like to do first (build a 3-wheeled Morgan-type vehicle, a cabin scooter, make a rocking chair for the wife etc.). I have admired the CD for a long time though, and have often thought of building one. I know that the pilot weight issue is a big one for a lot of people – some like me who like food a little too much, and some just because they are naturally big (as a side note I've thought it interesting that I'm 3 inches taller than my father and both my boys are taller than me – I see a trend!). Anyway, I think it would be nice to tweak the CD a bit to get something that had just a little more payload capacity without changing the design significantly. Additionally, there have been a lot of improvement in materials since the original dragon was made, so as I've said there might be some improvement in that regard.

I like Steve's Ti fittings, and what he has done on the leading edges and cockpit – he added a lot of nice details, so those are all something to keep in mind.

Personally, I would envision this as a small evolution, not a new aircraft. As an engineer, I understand that if you don't vary from a proven design too much, you shouldn't get in too much trouble. That's why I was suggesting maybe a simple scale-up rather than a configuration change (like sweeping the wing). The CD weight is in the neighborhood of 150 with a pilot weight [originally] of 150, but I see a lot are talking about flying at 175 or so. That's a gross of 325 on the high end. If we wanted to bump the pilot weight up to 200 plus just a bit of gear and a BRS shoot, let's say the gross would need to be 150 + 200 +25 = 375 Lb. That would be a 15% increase in weight. I think I agree that you can't get all of that back with span. Also note I didn't change the overall weight of the airframe as I think 150 Lbs is enough.

If you scaled up by 7% the wing-span would go to 47' the tip to 23.5 and the root to 64.25 -- that would give nearly the same wing loading which I calculate as:

original, 325 Lb /150 ft^2 = 2.16 Lb/ft^2
scaled 7% = 375 Lb / 172 ft^2= 2.18 Lb/ft^2

Looking at the lighthawk, it has an empty weight of 230 Lb and a wing loading of around 3.1 Lb/ft^2 with a flying weight of 395. The wing area is 126 ft^2

It's an interesting comparison, but I imagine with the larger wing the CD would have a lower stall speed, but would be slower (not a bad thing) and have a deeper spar (which also wouldn't be a bad thing). It seems like one would be in the ballpark anyway…?

I think keeping the wings in 2 pieces is really the only way to go (storage and all) – I'm not sure what you mean buy the plan being superior – I wasn't suggesting anything different.
Kenny



hi kenny
steve reflected my thaughts on sweeping the wing forward.

is there an aronautical engineer and aero dinamist in your area?were do you live?
what you are talking about is an entirely new aircraft.

dont forget the wings are made in two pices..the carbon rods have to be joined in the middle.it is my amator opinion that what the standard plans call for is superior.

building the wing in one pice may give you extra strenth and slightly less weight.
having said that id like to share some information i recived third hand..from the builder of my dragon.he had a conversation with the disigner and this is what i was told he said...the wood alone in the spare caps was strong enough.

steve is the most experianced pilot in the dragon....steve have you ever flown heavy,with balast?.....will kenny enjoy seeking micro lift in a standard dragon?

kenny reserch flutter....as far as how much balast you will need,you wont know untill its built.

hope i dont sound negative..love your enthusiasm.

russ.

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