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      Abbreviated rules   07/28/2017

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hump101

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About hump101

  • Rank
    Anarchist

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  • Location
    Brittany, France
  • Interests
    Naval Architecture structural engineering, speedsailing, offshore racing
  1. DIY Wing Mast Questions

    Having the sail cut flat does not mean it has to set flat, it can still curve conically or cylindrically, and this, combines with a rotating wing mast, allows a lovely range of shapes to be achieved with variable maximum draft location by adjusting down and out hauls, and sheets. This is particularly effective for high aspect ratio rigs.
  2. Recommendations for first time boat build.

    I built a 12m x 5m power catamaran back when I was young and single. It took 6 months to build the hulls, but 2.5 years to finish, with a total of 8 man-years of labour in it. I bought my second yacht.
  3. Picked up my first cat

    I would spend as little as possible on the boat and get out sailing. Once you've sailed it a bit you'll know better where to invest your money. Borrow some standing rigging off something a bit shorter, and lash the missing length, and just sail it first. You don't want to buy new synthetic rigging and have the beam collapse first sail. It is an old boat, remember.
  4. Picked up my first cat

    The bows are fine but they are also long and relatively high freeboard, so you'll find it more forgiving than you would expect compared to a H16 or similar. Because it is light and fine it accelerates rapidly, so again can be pushed harder than you might expect. Obviously in a big blow you'll need to depower downwind, but you'll quickly get the measure of when and how much.
  5. Picked up my first cat

    The hulls are more pitch sensitive than a modern hull, which has less rocker and a flatter, wider bottom at the stern, so can be pushed harder downwind. We buried the bows up to the beams regularly on the Unicorn, especially 3-up, and never pitchpoled or capsized, but once the foredeck is under it slams the brakes on whereas a modern hull with curved deck will drive on through and keep trucking. Sailing 1-up, the bow burying is easy to control and not a problem, unlike the Hobies of that era. The beauty of the Unicorn is that it is so much lighter than other contemporary cats (Hobies, etc.). This equals weaker, but mine was stiff enough and never had any structural issues, despite being overloaded most of the time. The light weight meant we could transport it on the roofrack of our 4x4 fully assembled, and getting it up there was a two person lift, whereas the Hobie that replaced it needed rollers to do the same, and a double hernia!
  6. Picked up my first cat

    I had Unicorn K35 back in the late 70's/early 80's. They don't sail like a modern cat, at that vintage, but perfectly respectable and will beat a H16 or H18 around a race course, as a comparison, but not an F18 or A cat. Mine had the original 5 batten main and a sliding seat, which was great fun but slow compared to the trapeze in transitions. We regularly fun-sailed with 3 on it, and it can just about cope, so a good boat to have fun with others.
  7. Making leeway

    Easy check for current is to tack and look at the numbers.
  8. Making leeway

    Looks like you had 1 kt of current at 303 degrees? Are there local current eddies in the area?
  9. F18 Worlds/ deck sweeper

    I'd be cautious claiming Cd is proportional to V. It generally isn't, especially for foil shapes which are more 2D flow, and where there is a clear dependency it is usually inverse and highly non-linear.
  10. F18 Worlds/ deck sweeper

    Not wanting to sidetrack this interesting discussion (I'm considering a decksweeper on my F40), but increasing speed from 20-30 kts is 900/400 times the drag, i.e. 2.25 times, not 100 times.
  11. Flying Dutchman - GE 9 - Restoration Project

    It was 30 years ago, we used a vacuum pump out of a plastic vac-forming machine, and big plastic bags that took the entire board, having tried stapling and waterbags with limited success. I don't have any photos, but I think one of the boards still exists at my parents house, though I'm not sure in what state. An eductor vacuum pump is cheap if you have an air supply already, and a roll of bag tape and some plastic would cost less than the epoxy you would save by vacuuming the veneers down.
  12. Flying Dutchman - GE 9 - Restoration Project

    Staple through nylon packaging strap. The epoxy doesn't stick to the strap, and the strap spreads the staple load so reduces damage to the veneer. Once you have a sealed hull you can vacuum the final layer on, which gives a better bond and no damage at all to the surface. Needs care when applying the vacuum, but a few staples on the keel line is usually enough to keep the veneers in place. I've built windsurfers like this, and laid teak decks onto curved surfaces, it should work for your hull?
  13. Team NZ

    Hoy and a few others have been measured at 2.7kW peak output, so 1450 is a bit low.
  14. Proa experience

    Just adding to Groucho's comments, another benefit of the wing mast is that, by cranking it to windward instead of leeward, you can rapidly depower the sail, very useful in a blow.
  15. Stolen Designs

    One of our alloy powerboat hulls was being displayed in a Middle East boat show. I was there to press the flesh, and one evening a man asked me to hold the end of his tape measure whilst he measured the hull. When I asked him what he was doing he was quite open that he was going to copy it, as he owned a GRP boat shop locally. When I pointed out that he didn't have the right to do so he just laughed and said I couldn't stop him. He made his copy, but in GRP and far too heavy, so the performance was terrible, and then had the cheek to ask me to try and fix it. He didn't sell any as far as I am aware, but soon we were getting people telling us our design was flawed because the performance wasn't as stated, and when we investigated we found they were referring to this copy, not our originals. Not a nice situation.