Rick,

 

I will have to wait till this evening to d/l the linesplan. I will be very interested.

 

In terms of the sail plan, I think I only mentioned in passing that the masts are teh same height (40' long, 34' luff) with a boom 9', so each mast has a sail area of 245 ft^2, so the total sail area is essentially identical to the single mast, but the AR of each sail is 4.7 now, instead of the total AR of 2.x for the sloop rig.

 

It would be great if I could reduce the size of the leeboard. I am all in favor of any reduction in force.

 

What don't you like about the leeboard up against the hull? One of the nice things about a proa is that the leeboard always has its force in the same direction, so it seems particularly appropriate. If your concern is just a scraping issue, I could certainly add rub-rails.

 

- Gardner

On Tue, May 24, 2011 at 7:24 AM, Rick Willoughby <rickwill@bigpond.net.au> wrote:

 

Gardner

I have uploaded a file showing the linesplan I am using for the wider hull.  There is also a curve showing the trim at full displacement with CoE at 6m.

As you can see this hull has much better trim at higher speed.  Around your speed of interest it will trim level or a bit bow up.  

It is time consuming to iterate these shapes to look at trim so I have only looked at this one shape.  I think the initial bow down is due to the flat sides.  I expect there will be a trough aft of the curve from the bow to the sides that will move further aft as the speed increases.  However at first it causes the bow to sink.  I cannot say if the slight rocker in the ends actually improves the trim in displacement mode.  At higher speed it will certainly help.  With full displacement on this hull the KMl is 50m compared with 40m with the narrower hull.  So improvement essentially from larger waterplane.  

I have not done drag at identical loads with the original lw but the difference looks to be small.

I don't think you have mentioned the proposed height of the new masts and the sail area.

I expect your board will have much greater area than needed.  It may be possible to reduce the depth.  This would reduce the bending in the board.  I like the pivot idea but I do not like the idea of the board working against the hull.    

Rick

I will probably not do much more till the 

On 24/05/2011, at 11:38 AM, Gardner Pomper wrote:

 

Rick,

I don't have any quantitative data. I think I picked it up from reading an old designer (might have been one of the hereschoffs) talk about shallow draft boats and say that so long as you kept the chine rounded at least with a 4" radius, the boat would not be slowed down. I have generally stayed away from hard chines because of that, and because of the plywood proa that I built and it didn't turn out well. Anyway, I am partial to Rob's make as much as possible out of one piece ideas; in the design I just uploaded, the lw hull can be made from a single 8' wide panel.

As mentioned, I uploaded top and side plan views of the modifications from all our discussions. It is in the files->gardner's layouts->toyyot folder of this group. Let me know what you think, even if you don't have time to calculate it.

- Gardner

Rick Willoughby