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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.  

Mal Smith

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About Mal Smith

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  1. DC Designs

    You can just laminate whole panels on a laminating table i.e. skinned both sides and then construct as you would in plywood, minus stringers. This can be a fairly quick method, no moulds required. This might require designing the layup so that the panels are not too stiff to bend to shape.
  2. DC Designs

    I don't think anyone would argue that composite is not stronger and lighter than plywood. However, wood is nicer to work with, is cheaper and is somewhat more environmentally friendly.
  3. DC Designs

    I didn't realise that the boat with the T foil rudder was yours Chris, although that figures. :-) I was also a bit surprised because I understood that your previous experiments with it a few years ago were not entirely successful? I've been interested in using a T-foil rudder in order to do away with the seat carriage, which saves a bit of weight and simplifies the construction a bit. However, my experiments with models have shown that T-foil rudders are slow, at least,up to the point where they help you to survive beyond where you would otherwise have crashed. Using the foil to provide lift upwind may cancel out the added drag, but then you still need the seat carriage to move your weight aft :-(
  4. DC Designs

    Did any notable technological advancements surface at the worlds? How did the big jibs go? Did Chris Mass' daggerboard flap work? I noticed some photos of a T-foil rudder, how did that go?
  5. D Zero

    I have to disagree. On an unstayed rig, whether you use the vang or the sheet will have little or no effect on how the mast bends (as opposed to a stayed rig where it does have a large effect due to the extra support points). What may change, however, is the way the rig responds to gusts. If using sheeting, the end of the boom is effectively pinned in position. When using the vang it isn't, so the rig is free to oscillate fore and aft. Also when using the vang the boom is free to bend in response to gusts as well. The combination of these two dynamic effects will change the way the rig behaves, but the average amount of mast bend and the shape of the bend will be much the same in both cases, for the same amount of leech tension.
  6. Lasers - Applying a Blow Torch

    If you don't travel, and if sails are durable, sailing is pretty inexpensive. But "updates" is a misnomer. I did not see anything in the 2001 kit that was not available when the Laser was introduced. It was a direction shift that put more clutter on the deck. Add a two year lag for people to recognize that the boat is not simple any more, what year was the peak participation? +1. I think that the simplistic original controls on the Laser were a major point of difference between the Laser and just about every other class. Sure, everybody grumbled about them, but it was a big part of the challenge, and it did help to keep the price down. Now, the Laser is just like every other racing class and has to compete with them on an equal footing for class numbers. The original concept of simple 'seat of the pants' sailing was lost.
  7. DC Designs

    So if the hull is flared at the BMS above the 1m tape end point, does the flared section have to remain above the 1m tape girth point for the extent of the 2m tape? If the flare was to start almost exactly at the end of the end of the 1m tape at the BMS, it would be easy to contravene this as shown in AndrewE's sketch in post no #3043. And perhaps it doesn't matter if the flare or spray chine drops down away from the BMS, but it is definitely not clear in the rule.
  8. DC Designs

    Arne, My interpretation: the BMS is just a transverse plane. "Centred on the BMS" simply means that the midpoint of the tape sits somewhere on the BMS plane. Because the tape also has to lie on the hull surface to check for hollows, by inference, the midpoint of the tape is constrained to the BMS/hull surface intersection line. In order to constrain the tape to a point, the rules would have to stipulate a third plane or surface to form that intersection point, but they don't, so the tape can be slid sideways to measure for hollows anywhere across the hull as far as the sheerline. Mal.
  9. DC Designs

    Sounds like a plan Jethrow.
  10. DC Designs

    Chris, Great to hear that you are getting your IC back together. Just let me know when you want to pick up the plank. Not so sure about your last statement. I've been soundly trounced by the Log in light stuff! Mal.
  11. DC Designs

    Chris, I've got an old plank and carriage you can have if you want. It's heavy, but solid and servicable. Needs hiking staps and i imagine the carriage may ned to be modified to suit your boat. But hey, it's free!
  12. DC Designs

    Amati, 1) With respect to the 2000mm tape, centred on the BMS means that there should be 1000mm of tape forward of the BMS and 1000mm aft of the BMS. I only mention this because your photos do not indicate that. 2) Not the radius theory. Interesting fact: If my maths is correct, the minimum possible girth at the BMS is 1126.2mm, so the 1m tape can never reach the sheerline. This means it will always be possible to flare at least 63mm of the topsides below the sponson line.
  13. DC Designs

    I have replied to AndrewE by PM, but I've copied the bulk of the PM below for general information: The spreadsheet grew out of a need I had to be able to ballpark some fast ferry hulls. I had noticed that for a range of hulls we had tested that there was a sweet spot (most efficient operating speed) for each hull which was dependent on the volume distribution/transom immersion. Initially I only wanted a method of estimating where the sweet spot was based on the shape of the curve of areas, however once I had developed a method for determining that it became apparent that I could use it to estimate the residual resistance. The key to it is the thing in the spreadsheet which I call the resonant velocity (Vr). The idea behind it is that a hull with an immersed transom has the same resistance characteristics as a longer hull in which the curve of areas has been extrapolated to the point of zero transom immersion, except that you then have to add in the transom effects. I developed the resistance formulas by trial and error, determined to use simple maths with no fudge factors. The residual resistance is broken down into a number of factors, bow resistance (the work required to part the waters, so to speak), stern resistance (pressure recovery), and a couple of components for the transom resistance. These are summed together to give the final residuary resistance value. There is an allowance for thickening of the boundary layer, but there is no form factor added so it's probably an underestimate, particularly for beamy hulls. The resistance formulas basically use mass flow based on the displaced volume of the bow half of the hull (Stem to Amax) and the velocity determined by the Vr calculation to get a resistance value at Vr, and then use scaling factors for other velocities. Frictional resistance is determined using the ITTC 1958 method. In the residuary resistance calculations the shape of the maximum cross sectional area (Amax) is approximated as a semicircular cross section of the same area. So for residuary resistance, the hull beam has no effect on the calculation. I had assumed that there would be an effect but after many attempts to include one, I had to conclude that if there is an effect, it is minor and largely indeterminate for the types of hulls I had data for. For the frictional resistance calculations I use the actual (approximated) wetted surface area and this is where hull beam comes into it, as for shallow hulls changing the hull beam has a large effect on the wetted surface area. I tried to set up the spreadsheet to use as few inputs as possible, so the hullshape used in the calculations is an approximation based on the key characteristics of the hull. The purpose of the spreadsheet is not to get exact resistance values, but to be able to quickly get approximate values for ball parking and investigation.
  14. DC Designs

    Which is sort of my point. The IC is not really a planing hull. It's a long narow hull which dose not rise a lot even at planing speeds. Generally you sail it utilising the full waterline length. The whole point of planing is to reduce wetted surface area. At high planing speeds, there is a thing called the waterskiers paradox whereby the reduction in wetted surface area due to lift cancels out the increase in frictional resistance and the drag becomes constant over the high speed range. Anyway, the IC doesn't operate in the high speed range, which is why I don't think you can apply planing theories to determine IC resistance.
  15. DC Designs

    FWIW, here's a link to my resistance calculation spreadsheet. It's based on Newtonian mass flow. Seems to work OK, but it's very general. Don't ask me to explain it . It was derived based on data for semi displacement hull forms. Maybe there are some useful ideas in it, maybe not. https://dl.dropboxusercontent.com/u/99666108/HullCalc5-120101.xlsx