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Re: steve's dragon 12 Dec 2013 23:47 #759

Composites are interesting. I work with them a lot in my day job. I know there are a lot of people who do their home construction with them. Wood has its advantages too. I wouldn’t say one is necessarily better than the other, but rather it depends on how the particular part is functioning and how it is loaded as well as the load magnitude. I have a friend who sometimes posts about his build (Mark Calder, who is building the Robin – he has a blog). I and a couple of others, as well as Mark himself have run quite a few numbers and he has followed that up with some structural testing (wing). He has used a combination of foam, glass, carbon rods, wood, plywood, and fabric, to build what I think is overall a very light-weight ultralight aircraft (maybe not exactly a motor-glider, but not so far from it) that will weigh under the 254 Lb FAR 103 limit. What I can say with some conviction is that the right material is the right material. And by that I also mean that there can be a lot of factors that go into that decision such as, manufacturing, cost, schedule, local weather conditions in the EU, or Asia, or in the deserts of Cali etc. These days there is a pretty big toolbox of material and processes out there. Naturally, one would expect some progress, whilst also realizing that there is nothing new under the sun and there have been some pretty cleaver things done in the past.

Yes, wood is great – nature’s little composite and all. For certain things it’s going to be tough to beat, but if the funds are available then it’s REALLY hard to beat advanced composite construction. It should be noted that those don’t come free, or even cheap -- in fact they generally cost a lot of time AND money.

Still, I really liked that on Steve’s CD he used carbon on the leading edge of the wing, and get the feeling that if he were to do it over he probably would have done the horizontal the same way. The graphite is very stable whereas in his video, he shows how the horizontal has had some warping of the plywood despite the covering (very nice covering I might add!). It may be that if you live in an extraordinarily wet climate that this would be something you want to do. It costs more and takes more time; so is it worth it? I guess everybody has to answer that on their own based on their circumstances.

For sure the thing we need to be aware of is that what eve one does that varies from the original plan, the thing they do it with should be at least as strong s the thing they took out. Steve replace the aluminum fitting with Ti – sweet, He should have (and probably did I’ll wager) saved a bit of weight as the Ti is nearly twice as strong [as good aluminum] and it’s better in fatigue.

Personally, I would love to buy a kit that had the D tube done in 45/0/45 graphite fabric AND had a slick composite body. I’d like to build it, but I think that is one area where there could be an improvement, but it’s sad to see everybody that wants graphite leading edges has to build separate tooling!

So, other than the leading edges (wing, vertical and horizontal, and a few carbon extruded rods), I don’t think I’d change too much…

Another interesting thing is these small turbine engines, which on a redesign, might be pretty slick as a self-launcher (with maybe even a winch to start it?).



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,

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