Arto,
Those boats are so beautiful it almost hurts. I also like the
modern (currently vaporware) interpretations at Scandinavian
Cruisers:
http://www.scandinaviancruisers.com/Scandinavian-Cruiser-30_1_5.html
http://www.scandinaviancruisers.com/The-Scandinavian-Cruiser-40_1_2.html
Alas, I have a limited number of moorings available, and a 40'
daysailer won't cut it. Anything I get in the 40' to 50' range has
to be fast, seaworthy, with lots of deck/tramp space, and capable of
going somewhere with two double or queen bunks.
But it's nice to see people working with the old lines. The
modern high-windage 30' cruisers, with plumb bows and hulls designed
around their interiors, are neither fast nor beautiful. (of course,
the same goes for most modern condomarans as well...)
Thanks for the link.
- Mike
Arto Hakkarainen wrote:
From: Mike Crawford <mcrawf@nuomo.com>
Subject: [harryproa] Re: Moment of inertia
To: harryproa@yahoogroups.com.au
Date: Thursday, June 9, 2011, 12:02 AM
<<I mean if the design is made to go through the waves with as little resistance as possible is it better to dampen the pitching by having lot of inertia or not? >>
Yes. Both are better. ;-)
I'd have to break it down by goal. If you're shooting for a daysailer that you don't intend to have out in really hairy weather, maybe it's nicer to have a more stable boat that pitches less. If you think you might be running into the back end of waves in a big blow, it's probably good to give those bows every opportunity possible to pop back up, including reducing pitching moment.
---
Robert (may he rest in peace) and Rick have certainly sold me on the idea of wave-piercing bows.
I've always been a fan of salty lines with a big shear and large overhangs. It's not the most efficient design in terms of waterline, but it can be beautiful. Some, like Wharram, will argue that it's a good design for big weather because there's lots of reserve buoyancy up high. I think that works in certain weather. Perhaps you'll be both higher and drier for a given hull length, at low speeds, in many sea states.
But I think the argument falls apart at high speeds and/or really big seas (which lead to high speeds surfing down waves...). That's when the bows are going to want to drive into wave faces, and a big shear and flat deck are going to seriously get in the way of popping the bows back up. So if you're racing, and therefore going quickly, or making a passage, and therefore need to be prepared for really big weather, the wave-piercing design is both safer and faster.
In which case, it also makes sense to reduce pitching resistance where reasonable. Again, to help those bows raise as quickly as possible. Not by spending thousands of dollars to save just a pound or two by going to all titanium shackles, but perhaps by centering fuel, water, and motors/gensets as much as is reasonable.
Plus, it's really nice not to have the outboard on the extreme aft end, popping out of the water in seas over three feet. That will drive you crazy after a while.
For a daysailer, which isn't necessarily flying into wave faces at high speeds, I'd say it's harder to form a firm opinion. Maybe
- Mike
Arto Hakkarainen wrote:
From: Gardner Pomper <gardner@networknow.org>
Subject: Re: [harryproa] Span Efficiency - Another Harryproa Opportunity
To: harryproa@yahoogroups.com.au
Date: Wednesday, June 8, 2011, 4:35 PM
Arto,I am not saying that it doesn't make any difference, but it seems to me that fear of weight aloft has become a phobia in the sailing world. For a monohull, I can see arguments with rolling and capsize, but not for pitching. If you look at a 40' monohull, either the bow anchor (50 lbs?) or the dinghy (200+ lbs) are 20' away from the COG. Their moment arm is 1000+ ft-lbs, vs < 50 ft-lbs for a block on top of the mast.For a proa, the situation is even less critical. My masthead plate might be 40' high and weigh 4 lbs, but a gallon of water in the ww hull is 20' from the COG and weighs 8 lbs, so it is just as big an effect.I don't want to come across as saying that piling weight at the top of the mast is good, but I have a hard time seeing why the effects on a harryproa are not minimal, compared to traditional (read monohull) thinking. Maybe there is an opportunity here for the harryproas to take advantage of some options that are closed out to other designs. One more reason to get a harry!- Gardner
On Wed, Jun 8, 2011 at 2:43 AM, Arto Hakkarainen <ahakkara@yahoo.com> wrote:
From: Gardner Pomper <gardner@networknow.org>
Subject: Re: [harryproa] Span Efficiency - Another Harryproa Opportunity Date: Wednesday, June 8, 2011, 2:03 AM
Rob,
Yes, the discussions of upper winglets on monohull forums always hit the "weight in the wrong place" argument and quit. I can see that argument for multihulls, because of rolling, capsize, etc. I can even see it for racing multihulls, which may want to sail heeled over to fly a hull. I don't see the relevance for a cruising multihull that is never intended to fly a hull. If the hull ever lifts, even a little, you will do all you can to depower as quickly as possible, so your heel angle should not even exceed 10 degrees. (ToyyoT is heeled about 3 degrees when the ww hull flies).
So, it would seem that an extra 10 lbs at the top of a short mast should not make a significant difference. Am I just naive?
- Gardner
On Tue, Jun 7, 2011 at 6:16 PM, Rob Denney <harryproa@gmail.com> wrote:
Steve Dashew tried tarps under the boom on his 65' mono. Reckoned they made a huge difference. Loic Peyron tried a wing tip at the top of an ORMA 60 tri mainsail, took them off soon after. Top ones are a problem as they are weight in the wrong place and because they contribute to capsize when seriously heeled. I have some ideas for a masthead tip which stays horizontal which I intend to try on El when the new mast is built.
rob
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