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      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  

CaptainAhab

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About CaptainAhab

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    South Australia
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  1. I'm making a rudder

    There are also huge twisting loads. The 45 degree fibers take all of those. Another load not typically talked about is when the boat is sticking half way over a wave and has to support itself. One of my good friends built a very high end IOR boat in 1982. It was a bit before its time in many regards. Other than the mat(poly resin) to bond the Airex foam, the boat was made entirely of unidirectional S-glass. Bow to stern on the bottom and then at 45 degrees to the waterline. He was a structural engineer back then, then moved on to be the lead composites engineer for one of the major defense contrators.
  2. I'm making a rudder

    I'd be surprised if many people are aware of how far the Gougeon Bros have gone with the wood/epoxy composites and when. My favorite is pages 31 & 32. Lead weights for testing Page 82 serious Boeing style testing http://www.weti.fh-flensburg.de/fileadmin/dokumente/Aktuelle_Meldungen/141216_Hancock_-_Wooden_Blades.pdf I just fond this online. I already knew a bit about the windmill blades. Goegeon had 95% of the US market until the early 90's. This stuff makes our little boats look like toys.
  3. I'm making a rudder

    I am not saying that a hull is a rudder. Simply that it is possible to mix carbon/glass/wood in a very complicated package. In one of the original posts, I gave the link to the Gougeon design for wood composite rudders. They are the ones encouraging the carbon reinforcement. You could use a thick band of uni S-glass instead if it makes you feel better. They do the math & have the experience...
  4. I'm making a rudder

    Perhaps the most experienced people that reinforced wood with composite would be the Gougeon Brothers(West System Epoxy). They have reinforced many projects with carbon, glass, kevlar. The first example that comes to mind is their skiff. They have been building the Swift Solo skiff for 15+ years. They tested many different composite panels. Different skin layups inner and outer. They ended up with S-glass outer skin/cedar strip core/carbon inner skin. I think it would be a fair assumption that a high performance skiff hulls sees more diverse loading than most other composite structures I fully understand the engineering principals of stiffness, Young's Modulus ... They do not take into account the unusual aspects of timber construction. It is a very unique material when bonded to other materials. It is not a metal or fibre which can be so accurately engineered. https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=0ahUKEwiZpPjMgebXAhUEjpQKHa0pCAQQFgg3MAU&url=http%3A%2F%2Fwww.single-handedskiffs.com%2F&usg=AOvVaw1noPlQzNIjyLKbTrPdnBMJ They are using the wood as a core. In the same way foam is used. Nothing really magical happening there. Fibreglass structures are often reinforced locally with carbon. So that's not a problem. Fastnet could certainly be caused by improper load sharing. But that was a poor design problem.
  5. I'm making a rudder

    Those bowl cutters wear out fast. you just need a good sharp 3/4" dado bit. It exactly what they are design for. The wider the bit, less lines and it's more stable. Table saw would not be accurate. It would need a ton of clean up. Expecting perfection is a false expectation in this case. Too much glue too many joints. clamping it together is a pain in the ass. Hard to keep it perfectly straight. Which in all honestly is the most important part. Bow or twist ruins rudders.
  6. I'm making a rudder

    Its fine to use the non structural foams as a form. As long as you honestly know how much glass/carbon to put on the outside. There is a much higher safety factor using a structural foam because it creates a reliable composite panel. The stiffness goes up by orders of magnitude. The money you save on inexpensive foam is spent on more fibre & resin. I prefer cedar cores myself. Beautiful material to work with and it kills a couple of birds with one stone(core and fiber) He's cutting across the grain. Whatever bit he is using its not the appropriate one. Milling bits are designed for metal and will cut fiberglass as well. Personally I would have tried a planer router bit or a 3/4" wide mortising bit. There is a fair amount of sanding after a rough router job The last rudder I did was a Naca 0012 profile. vertical grain western red cedar core. epoxy/ glass. I used a power plane and a straight edge. fastened my templates to the end of the blank. I took light licks from one end to the other. I was done in an 1-1.5 hrs ready for glass. I'm a true craftsman with a power plane. Not for newbies. I made up some 10mm G10 like flat stock on a sheet of melamine and bonded them to the top and bottom of the blade. I used high density filler for the leading 1/2 inch and 1 inch for the trailing edge. carbon inlay at max chord . 1st coat of resin soaked in for a couple of hours. Then 12 oz double bias. Followed by 4 oz cloth to get a smoother finish and less print thru. I'm not concerned about water intrusion unless its damaged. At least the cedar won't rot. I like making foils. They are time consuming and finicky. If done right they rewards justify the efforts. People also try using plywood cores. I find them brutal to shape compared to solid wood. apparently thye have found some of the older plywood rudders on bigger boats that suffered core sheer. The veneers kind of roll over and disturb the whole laminate.
  7. I'm making a rudder

    Its fine to use the non structural foams as a form. As long as you honestly know how much glass/carbon to put on the outside. There is a much higher safety factor using a structural foam because it creates a reliable composite panel. The stiffness goes up by orders of magnitude. The money you save on inexpensive foam is spent on more fibre & resin. I prefer cedar cores myself. Beautiful material to work with and it kills a couple of birds with one stone(core and fiber)
  8. I'm making a rudder

    https://www.westsystem.com/the-105-system/reinforcing-materials/biaxial-fabrics-tapes/ There you go. Even the Gougeon Brothers at West System made the same mistake. Next time you are in the States looking for some reinforcing fibers. Ask for Uni, Biax, Triax, or Quad. Interesting cultural phenomenon. Australian English is based on slang and shortenings. An exception being the highly educated and posh fibreglass tossers use double bias to refer to +-45 fabric.
  9. I'm making a rudder

    It might help if you read my post. The example I gave is real not fake. Its on the label. It has nothing to do with the mat. The mat is simply part of that product. technically biaxial means opposing 90 degrees. In the US the opposing "axial" fibers are unidirectionals are layed on top of another. 0/90 is a woven cloth. No one calls 0/90 biaxial in the US. They call it cloth. Its nomenclature. There is a product of uni fibers in the 0/90 format. Its essentially modern woven roving. Because double bias is so much easier to use its hard to even buy it in the US. I'm from the US and live in AU. Stop arguing with me.
  10. I'm making a rudder

    There is a simple specific reason that boats or other structural composite objects are not made out of blue/pink construction foam sheet. core shear
  11. I'm making a rudder

    Biaxial cloth is +-45(US) Double bias cloth is +-45(AU) Same thing ... different hemisphere https://www.jamestowndistributors.com/userportal/show_product.do?pid=1470
  12. Stainless vs Aluminum - the struggle is real...

    They did an engineering study of lock washers. They are totally ineffective. http://hillcountryengineering.com/wp-content/uploads/2011/10/Split-Lockwashers-Separating-Myth-from-Truth.pdf I like NASA. I believe NASA. Yes, they landed on the moon six times. They also have had a couple of rovers on Mars. If they don't use split washers, then I won't either. Its Nylock nutz or some toxic goop made by Loctite for me. We used standard lithium grease on a racing boat mast in 82. Repainted her in 96. Did not have any problems. All the fasteners were tapped. They came out like they were installed yesterday. Owner/Builder is a composites/structural engineer. He would have used something better if it existed.
  13. I'm making a rudder

    https://www.jamestowndistributors.com/userportal/pdfs/WestSystem/Rudder_Blades_and_Centerboards_000_448.pdf Read this. Build it this way. Ideally you should do the carbon fiber inlay and wrap it with a continuous layer of 12oz biax. If you don't do the carbon. Do a continuous layer of triaxial glass. Continuous meaning you support the whole rudder on edge. leading edge up. drape the cloth over both side. Its a good idea to make the first 10mm and last 10mm of solid glass/resin filler. 10 oz regular cloth will waterproof it. Not much strength happening there.
  14. Degassing Epoxy

    Use a propane torch after you have spread the resin. That's how you do a table top epoxy finish
  15. Refinishing a very ugly aluminum mast

    He wants What this guy said. With that actual deep corrosion pitting. I would grind it with the narly discs. Remove all the pitting. Like others have said, wipe it and prime it with any decent 2 part epoxy primer. Interlux is available and ok price. Fill those defects with west system epoxy filler sand the whole beast with 240 and paint it with 2 part poly or 1 part if you can't afford it. Do not go cheap on the primer. Avoid your body parts especially all appendages with those grinding discs. As usual no drinking and no holding hands when using power tools.