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Discussion in 'Composites' started by pequeajim, Jan 31, 2007.
I agree with others that timber is OK, it may be just a web filler, considering most fiberglass spar webs are just glass over foam with hard points. The glass caps may be S glass(usually are) which is 20% stronger than E glass, with Carbon being 30% lighter than glass - therefore 50% stronger than E glass. Carbon is very stiff and is used where extra strength is required (the wing root) or as a replacement for the lot as a weight reducer.
Carbon fiber also has much better fatigue characteristics than glass and when you compare materials by strength it's cheaper than aircraft grade spruce
this poor Guy can't catch a Break!! please explain!! and Why not use Kevlar? bulletproof airplanes!! very roadable!!
Kevlar needs a special epoxy resin that will hold the strands other wise they are simply able to pull out of the resin that is holding them.
Carbon also needs good quality resin be it Vinylester specially manufactured for carbon construction epoxy !!
And carbon snaps like a carrot when it does break !,
GLASS used with a good quality Vinylester resin in a life threatening situation will win hands down every time !the biggest problem with what people class as hi tech layups and laminates is loading materials to work at there absolute max all the time without any thought of a safety limit ! Weight saving and skimping on resin and poor understanding of fibre orientation in so many cases are just some of the known reasons for products having a very limited life expectancy!! Another contributing factor is using dissimilar material's that have completely different characteristics and are not compatible with each other and so stress is happening within the product its self what ever it may happen to be . All these things were found out during Americas cup yacht racing over long periods of time !!
mr NoStealth you and your comments you just sound like "APEX" from boat design.net a few years back ! he was a one of them as well
Tunnels, you keep asking why you can't get straight answers to your very general questions. But then you come back with these diatribes full of misinformation and half-truths that are by and large not relevant to the established composite practices used in aircraft construction. I think I can understand why some doubt your sincerity.
Thanks, Bob K.
We're kind of an odd bunch here Tunnels because we're sticklers for correct information- our lives depend on it. Seriously, you might have better conversations in the boating forums.
Yeah your right its a waste of time !
Aircraft composites is a nothing place and really is pretty backward in its thinking compared with Marine composites that is streets ahead !!
As far as amphibious and new designs im sure there are dinosaurs' in the back ground of some of the photos !!
If it sounds the same, perhaps you should consider what boat design.net a few years back and HBA today have in common. Hint: it involves a member who uses lots of double exclamation points.
P.S. You say you were born in New Zealand. As it's an English speaking country, you should have learned proper grammar and punctuation.
We're kind of an odd bunch here Tunnels because we're sticklers for correct information- our lives depend on it. Seriously,
Odd bunch that's an understatement or sure !! sticklers for correct information HAH that's a joke !!
There's a reason that standard airplane building techniques look flimsy and outdated to you. Water is 200 times denser than air. People have tried building airplanes with boat building techniques and ended up with something that looked like an airplane but wasn't because it was too heavy to fly.
I'm tempted to try to help this guy but feeding trolls is counterproductive
There's a name for those. We call them "boats."
Yep, one wing is the keel, the other is the sail and the H-stab becomes a rudder
That's the Harbor Freight engine discussed in another thread recently...
Always the same blah blah from the same people all over this forum ! armchair experts and all they have to give is bad breath and hot air !
On the other side of the coin
There are some really helpful and informative people that I have managed to glean a lot from ! Norman is one such person and I respect his posts greatly , always filled with good useful information , no frills or compost .
Like most forums they have there share of no-hopers that just like to see there name's up on the screen, this one has more than it fair share !
In all the many years I have worked in composites I have made some huge long list of things ! including extremely light weight racing Yachts ! These are built to absolute extreme and very gram of weight must be accounted for !! IS it really necessary ? during racing even crew were sacrificed and thrown overboard at some point where they had to swim for shore or be picked up. All this in the quest to win at any cost !!.so using thin light weight flimsy lay ups i have done !
My job has been the constant search to make things strong , robust and safe yet light weight for life saving equipment ! I embarked on my own testing program because of all the bull **** that gets printed and spread around of how good things really arnt !!
I chose the mighty 3 !!, carbon , Kevlar and glass with of the shelf marine grade polyester resins were used to make the same 3 items and all subjected to the same tests to complete destruction carrying wired on lead the weight of a person !! tests included dragging over sharp rocks and dropping down a 50 foot cliff to rocks at the bottom and dragging along a wet sandy beach for 1 kilometre and finally dumped at sea and left to get washed ashore through huge pounding crashing surf ! The end results most people could not comprehend !!
Carbon crapped out in the first test and never got to the drop down the cliff test! so that just left Kevlar and glass ! the Kevlar material held up well naturally but the resin was the weakness (so if you use a strong material then you have to use the best resin possible with it !makes sense ?? ) these two made it to the wash up on the beach after being pummelled in the waves and surf the glass was amazingly resilient and even torn and a big surprise!!! the really damaged Kevlar had become soft and bendy as the resin has broken and wasn't able to hold the much stronger Kevlar fibres and the resin had pulled out and crumbed. Last the drag on the wet sand yes the glass wore way but not as much as was expected .
Figures and pages of laboratory tests done in perfectly controlled conditions are pretty pointless and have little meaning when it comes to dealing with mother nature !
So end of this is I would still always trust my life with glass fibre products and possibly Kevlar MAYBE!!
The reason you get some of those replies is that you refuse to put in any effort yourself and are very outspoken about some of your pet-ideas that have no relevance for aircraft or are even downright nonsense.
Take a few steps back and start behaving. If you don't like doing that, you can leave HBA one way or the other.
The contrary. Tests like you describe are useless, just like anecdotal info from accidents. Outcomes could be shear luck, shear bad luck, but usually tell little if anything about the material/part in question.
Dropping an airplane on rocks is called a crash and is expected to destroy it. Carbon fiber is used for exactly the reasons you don't like it: because it's stiff but also it has the highest strength to weight ratio of any of the materials we can afford. Yes, it fails catastrophically but if you design with appropriate safety margins the point of failure will be outside the operating envelop. As far as I know boat hulls don't suffer from flutter but airframes can. The stiffness to mass ratio of a spar is a significant parameter in determining when the wing will flutter and carbon makes a lighter spar for the stiffness than any other material except boron. Have you ever seen boron fiber? It's amazing stuff but a bit out of the average homebuilder's price range
To test only a few properties of a material and be sure of which properties you test there is not other ways than have controlled conditions. And make the test on multiple items at more than one instance. When it comes to complete prototypes, testing one may not be enough either. At lest three, and better closer to then does it most of the time I have learnt from mine trade.
Separate names with a comma.