It is great to see the theoretical stuff, expecially when it supports the actual results. Thanks Björn and Rick.
On Wed, May 30, 2018 at 12:48 AM, Björn bjornmail@gmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:
The original Bucketlist would have been an extremely light boat. My formula says 12^3 = 1700kg. According to Robs measurements, Bucketlist was on target to have around 500kg lightship, 700kg with crew. So less than half of my formula. Which means between the red and blue curves above. So it looks like it would have been completely without a "hump" at hull speed, it would just go linearly faster with windspeed until it runs out of righting moment. But would it have been too light? Too much wetted surface for the sail it could carry? I guess we will never know.Rob, I think it was very sad to see Bucketlist shopped into pieces! Now we can't see how it would have performed! It would also have been interesting to see if it would plane on the lee hull! I think Bucketlist would have been the lightest boat in the world for its length, so I think there exists no real world data with regards to planing on that kind of narrow, flat bottom, very light hull. If it would plane, it would get rid of some of that extra wetted surface area, and sail even faster. Was it because of all new foiling boats getting popular, that you stopped development?Will the new one (triscarph) be as fast? I don't really understand the Triscarph configuration. Will the waves cancel out in some way? Or will it be as draggy as two very short hulls with bad length to displacement ratio until it foils?
I agree about chopping up Bucket List, but there were sound reasons for doing so. Not least was that it was basically a scaled up Elementarry so apart from the planing (mostly of academic interest), it was not going to tell us much. It was more interesting (and practical) to me to see how triscarphs and foilers work
as they
look like a much better solution to big race multis than long narrow hulls with lots of wetted surface and weight. On this subject, BL is on the back burner as i am experimenting with mast and rudder builds and 'safe', cheap
wing sails. These are
cheaper, quicker and easier on 7.5m/25' El than on 11m/38' BL. Mast method looks good and will be in future plans, although yesterday's effort was a shortcut too far and is in the rubbish.
First rudder blades were easy to build, but did not steer well. Second ones are happening now. L
atest rudder mounts are a treat to build and use, but might have other limitations. Pictures of all of these on the web page when i get round to taking them. Dougwrote:
What would be wrong with the Bucket having ww hull of say 12m, but stiil similar minimal accomod's?
The wetted surface and weight goes up, the twist in the beams increases and the ends are pretty much unusable. As the hulls get longer and skinnier, the benefits reduce. There is a crossover at between 8:1 and 10:1, which is why harry windward hulls are 10:1 or skinnier.
Just as a guess, it looks like it might. I think Rob said he could see something. Or that the bows were not pushing down on Bucket. A very light and long boat like bucket may not go bows down as much anyway.
Correct, although it was hardly a conclusive test with the small sail/light wind.
On Wed, May 30, 2018 at 12:48 AM, Björnwrote:
But if the boat is standstill, and the sails are sheeted in fast, or the boat turns by itself (you can't steer a standstill boat with the rudders) into a position where the wind is creating a strong force in the sails, there is no dynamic lift from the hulls, and the inertia of the standstill hulls when trying to accelerate increases the pitching moment. This has happened to me on my Hobie many times in rough weather. Doesn't help to sit in the very back, and lean backwards as far as possible. The trick is to slowly accelerate the boat so the pitching moment is not increased by the acceleration/hull inertia, and then you can very carefully turn into the direction you want to sail. But the bows are just cm above the surface, and the waves are flooding them all the time, slowing the boat, and making things more difficult.
Absolutely. What does help is schooner rigs and fore and aft rudders. Sheet on the front sail and steer to leeward with the front rudder and the boat moves forwards far sooner than it can with daggerboards and a rig where the main usually powers up before the headsail, made worse if there is no headsail.
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Posted by: Rob Denney <harryproa@gmail.com>
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