Ask Lemmy

Forgot this stuff, sorry:

Aviation:

• you need ALL of Mike Busch's books!
• Barnaby Wainfan, at Kitplanes: read ALL of his stuff. I disagree with some points of his ( & consider his faceted lifting-body aircraft to have been needlessly unsmooth: I like Mike Arnold's ultra-low-drag paradigm! ), but he gives you sooo much understanding, that you simply aren't competent in this domain if you aren't understanding the stuff he's giving.
• S-Glass is nearly as stiff as carbon, but MUCH tougher: consider it for your wings.
• E-Glass is radar-transparent, the other composites generally aren't: make any radome of it.
• Turbine-engines cost about 10x as much as piston-engines, to buy, but maintenance-intervals can be MUCH greater, which is why commercial operations like them.
• All aircraft NEED redundant angle-of-attack indicators: fly that indicator, & you're safe: nearly-all the final-approach-crashes due to stall would have been prevented with AoA-indicators on the flightdeck. ( the McDonnell Douglas 737Max fiasco is because McDonnell Douglas, now falsely-labeled as "Boeing", they did a reverse-takeover from the inside, after the merger, allowed only 1 AoA-sensor on the airframe, & if that reading went wrong, the avionics highjack the aircraft from the pilots. People died. IN AVIATION, REDUNDANCY SAVES LIVES, for critical-avionics! )

Boats:

• there is the Kelvin Wake Angle that you need to understand: it is the angle from the longitudinal-centerline of your boat, out at an angle, along-which your wake's peak lies. It is 19.5-ish degrees ( 19.47, iirc ). For multihulls, you NEED to make-certain that that angle doesn't go from the bow of 1 hull to touch or get too-close to any other hull: it NEEDS to have space, xor you're creating needless drag. Also, for slenderness, you need to be able to create that angle from your bow, & NOT have your bow's bluntness violate that angle.
• the LWL:BWL ratios ( Length or Beam, WL means WaterLine ) of interest for multihulls are between 8:1 & 12:1. Going longer than that, as Gerr pointed-out, gives you too-much skin-drag. People who've studied aircraft-design know that you want the skin-drag to equal the other kinds of drag, because that's your minimum-drag. Making a hull 18:1 means you've got less bluff-drag, but you've got waaay-more skin-drag, so you're losing, in the displacement regime. Hydroplaning boats are different. Wave-piercing speedboats are different. The multihull designers generally target 9:1 because it really is an optimum LWL:BWL.
• Silicone-Silane is the ONLY anti-fouling that people ought be considering, nowadays ( "Silic One" is 1 brand of that kind of stuff ). NOTHING else works as well, or is as slippery for reducing drag.
• After you've earned you real-competence, & now you want to instantiate a business, you're going to need ABYC membership, & if you're wanting to sell into the EU, you're going to need the ISO/DIN standards, which will cost you .. about $30k, so you can make your designs compliant with their regulations. They intentionally constructed their standards to enforce as much buying-of-other-components-of-their-standards as possible. To me that is anti-economic-flourishing: putting needless barrier-to-entry, but they're the ruling institution, so they get to make their economy obey their authority.
• The 1st implimentation of a boat, that vessel's name, becomes the model's name, so if you want to control your boat-names, then you can't have your customers deciding on the name of the 1st implimentation of a design, can you?
• NOLO press makes books on intellectual-property, including Patent It Yourself, which includes a section on getting EU patent protection. Give yourself perhaps a year to get through that book: it's technical stuff, and there is one hell of alot of stuff to know, in patent-applications, in order to not need to hire ( for $10k+ ) a patent-lawyer for your single application. EU patents are covered in a section of that book, but EU patents cost WAAAY more than North American patents, per point-of-application, or search, etc.
• look at the designs of Cape Falcon Kayaks: they're elegant in ways that nearly-no boat-designers would do.
• look at the designs of Dave Gerr, if his site is still up, & see how solidly good his work is, compared with normal
• BoatDesign.net is the primary place for boat-design discussion, though .. I think it was called "sailing anarchy" was a competitor to it, don't know if they still exist ( don't know if either still exists, actually )
• you need to study & understand composites, if you're doing that, & I'd recommend studying some of the stuff from the aircraft-domain, too ( I got Niu's composite-airframes textbook ), so you get much-better-than-DIY-"information" about what's proper. 2" radius minimum for composite-carbon, & that may be pushing it, & you CAN'T mix reinforcement-fibers & get the benefits-of-both: you get the disadvantages of both, not the benefits.. this one's important & non-obvious, so I'm breaking it out into a discussion, not just this little list-point..

Say one has reinforcement-fabric with graphite fiber going east-west & kevlar going north-south.

Then the next layer is with the graphite going north-south & the kevlar going east-west.

Now vacuum-infuse it, so resin spreads forces between all the fibers..

What happens when the temperature rises, in hot sun?

The kevlar SHRINKS. Kevlar has a NEGATIVE Coefficient-of-Thermal-Expansion ( CTE ), but graphite's is close to zero, & epoxy's is positive..

So, now your layup is stressing, because some fibers are shrinking, & others are not, & the matrix is expanding.

Worse, when you try flexing it, kevlar isn't stiff, so NO flexing-force is going onto those fibers, ALL of the flexing-force is going onto the graphite.

But did you calculate your layup so the graphite fibers would be able to take all the flexing that your piece needs to bear?

If not, now it'll break.

In composites, the stiffest fibers resisting flexing, are taking ALL of the stress of that flexing, until they break, then the next-stiffest are taking all the load.

Mixed reinforcement-fibers is IDIOCY, but you can buy many brands of differently colored aramid+carbon reinforcement-fabric, from many vendors.

It is Niu's composite-airframes textbook that caused me to know that, & the industry is pushing snake-oil bling, instead.

The only 2 cases where mixed-reinforcement-fibers makes sense, are

1. entirely-cosmetic pieces, which bear no structural load, &
2. pieces where you're orienting all the stiffest fibers in 1 particular direction for stiffness in that direction, & you want flex in the other direction, so you use e-glass or something in the bendy-required direction.

Oh, & graphite-fiber's just thinner, stiffer carbon, generally. Processed at a higher temperature.

There: hopefully I've given you enough so that you can compete against me better, in the future.

Salut, Namaste, & Kaizen, eh?

_ /\ _

I feel like there's some amount of this in every hobby, which sounds like I'm downplaying this take and racing but that's not that case I promise you.

I can imagine how this would be amplified big time in a pretty expensive hobby/semi-pro/pro? I assume there must exist some amount of pros

But yeah as a collector of a couple to many more likely expensive hobbies, it's crazy how much shit you see designed to just separate people from their money efficiently