I read the first line and skipped the rest
Clearly a challenge to me direct in the form of a thread. Unfortunate. I can't
believe I need to defend my opinion composites suck, but let me be clear
composites are not deficient in strength. I never said that.
If you want a dialog on what I think, than write direct. I am not going to get
into the Joy of composites on a RV related site. I am NOT anti-composites,
but frankly much prefer working with metal.
If you want to talk structures I would be glad to, write me. However to start
a thread as challenge to me personally, awww shucks NO! That's not going to
cut it, but I will make general comments.
----------------------------------------
Yes I have analyzed advanced aerospace stuff, both aluminum and
composites for the military and commercial aircraft in a previous life. I'm may
be a little more than familiar with composite primary structure. It is great
stuff. It did not usually save weight or cost,
but we could say we had a
composite tail like Airbus. (
Aren't the composite tails falling off Airbus
and AD's issued? The last on that came off was blaimed on the pilots. )
There are material properties of an all composite plane that makes it
tough to design a safe structure for occupants, because its TOO strong.
The "bending" of a steel welded cage or monocoque aluminum structure is
what absorbs energy. To be honest I have never designed an all composite
plane, but I am familiar with the re-wing of old Navy A6's, with a carbon fiber
wing. It was not successful. It was too heavy and so stiff it beat the
hell out of the crew and fuselage.
The B2 could not me made with metal. go composites, but one of the most
awesome planes to fly, the SR71, was (titanium), go metals. In general any
plane can be made out of either material. Metal can be stretched formed.
Most jet wings are machined out of huge solid aluminum plate. Composites
have the advantage in complex shape tooling, but they are not cheap, easy
to make, inspect or repair if a mistake is made. Every thing has to be perfect
in the process or it is junk.
You don't really need super fancy complex compound curves to make a fast
plane. P-51 and many modern jet fighters are made (whittled) mostly from
solid metal. The latest Gen fighters, like the F22 are more composites, but
most of the primary substructure is still metal I believe. Clearly for stealth
composites skins are best. However not sure how that applies to a little kit
plane.
So I am comfortable with both metal and composite construction, but the
latter for a small kit plane for myself, not so much. That's all. However, did I
say composites suck and metal rules.
Nothing wrong with composites, however they are usually incorporated in
little aircraft with high wing loadings, like the Lancair IV, thus have high stall
speeds, thus more landing energy, which is a Big-Ol-negative IF an off field
(crash) landing is needed. That is significant energy. All these are factors
in crash worthiness. Add a stiff composite airframe that will NOT absorb
energy, you have an issue. It is an issue than can be solved with engineering
but
most kit planes do not have energy absorbing seats, especially the
composite ones that need it the most.
RV's stall in the low low 50's (mph) for gosh sakes. That's pretty awesome.
Now NASA did some test on composite fuselages, aka Cirrus, and you need
high energy absorbing restraint systems.
Is a RV safer? Probably a little.
Mostly from the advantage of it's low low stall speed, slower than C152.
As far as Lancair "speeds", they are just fiberglass RV's with REAL big
engines. Well why do they have higher Vne? Well because they are over built
and designed that way. Van's control surfaces are made for handling, not
extream high speed cruise. There's no secret, no free lunch. If you want a
high speed cruiser with big engine and little wing than you will sacrifice,
landing, handling and aerobatics. Look composites has nothing to do with it.
The SX-300 is all metal and is even "hotter" than the Lancair. Would I like a
SX-300, heck yea.
It's not Rocket Science:
Big engine, little airframe, little wing, smooth
streamlined surface. The formula has not changed. It can be done in
metal or composites. You want fast metal get a SX-300/Questair Venture.
You want plastic, clearly the lancair is the main game in town, unless you go
with the new NXT- (single seater from John Sharp- nemesis).
NXT or
Wow NXT
Here is an example, the Lancair Legacy FG with 200HP cruises at 210 mph at
8,000 ft. That is the same (slightly less) as a RV-4/6/7/8 with the same size
engine.
There's no BETTER, just differnt.
You can make a metal plane smooth and fast. However the cowl, cowl and
fairings would be hard to make from metal. When it comes to compound
curves composites have a clear advantage. (There, I said it. That's the only
nice thing I will say about glue and string ever again, ha ha.)
I hope that settles it. You would think I drew a funny cartoon of someones
mother or deity. Its just my opinion.
I just prefer a plane I can safely make
a forced landing in, at min speed, that bends and protects my bee-hind. I
also like saving lots of money.
I love the Swearingen SX-300.
SX-300 . That little hot rod is sexxxxxy.
It is all metal and has a hot stall speed (75 Kts.), like a Lancair IV (claimed 75
mph stall, cafe foundation 76.3 mph). I would consider one, but God help you
with either in an off field landing. With a composite Lancair, you better have
16 g seats that absorb energy because the airframe will not do it.
For a general over-all fun plane the RV is best for me in every way. Cost,
construction ease, handling, safety and just because.
Can't believe I am
defending I like RV's here, but I am. I am sorry to all composite/Lancair
fans I am not validating your choice. I'll respect you in the morning, but don't
have to like it, do I?
There is a reason RV's sell the most and Lancair almost went bankrupt.
If you want to convince me of the superiority of Lancair's or composites
Don't. However if you feel you must write me to tell me how wounderful your
glue and string soul less flying hot tub is, write me email direct. Save the
threads in my honor.
Cheers George
