On Wed, May 19, 2010 at 7:04 AM, Gardner Pomper <gardner@networknow.org > wrote:
Hi,
I apologize for asking this, because I think I have asked before, but I can't find the answers in the old posts.What is the height of the Harryproa mast (Aroha or similar)?
14m from the keel.
The design I have been settled on for the last few months is very similar to Harry in length, weight and displacement, but I want 2 things that are seemingly very difficult:1) I want to sail at wind speed up to 15 kts, which means I want to be able to sail 5kts in 5 kts of breeze.
This means a tall rig as there is much more wind up high in less than 6 knots
2) I want to be able to fit all the pieces into a 40' shipping container.With a 40' mast, with 4' of bury and a 9' boom, the best sail area I can get is 35x9x0.8 = 252 sq ft main + 6x30x0.5=90 sq ft jib, and that might be pushing it. Total sail area of 342 sq ft, which is 110 sq ft (25%) less than harry.
Depends on the weight as well. Suspect you will need a Bruce Number fully loaded of more than 1.7 to sail at windspeed.
Questions:1) Is a Harryproa that fast at low wind speeds, or do I need even more sail area in light winds?
Suspect you will need more sail.
2) Can I make up the difference by using a wing mast?
Some, but not all.
3) What about a gaff or lug rig to increase the sail area without increasing the mast height?
A lug or gunter would do it, but they are draggier when reefed.
4) What about a stub mast, so that I can get a full 40' luff? Would that be the "best" (cheapest, easiest, fastest) method? I could make the stub 7' tall and have the ballestron boom all moulded in as a single piece.Stub masts make it hard to access the top bearing, is heavier than a single mast and bigger diameter, which is maybe not a problem with a wing mast. They are also harder to step. None of these are insurmountable, but I think if you are going to have a join in the mast, it is easier and lighter to have it up high, with no bearings required. Cheapest, but not very pretty is probably a top mast with a bonded on external sleeve which slides over the lower mast. Or telescoping, if/when it works.
Do any of you computer geniuses know how to get videos from You Tube into a form that can be used on Powerpoint? I am giving a talk in NZ next week and would like to show the Rare Bird video. The venue may not have internet access. If anyone can download it and send it to me, i would be very grateful.
rob
Thanks!- GardnerYork, PA
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