03-28-2008, 04:47 AM
Greetings everyone.
Got good news and bad news.
First the good news. Iâve put away my silly righting moment spreadsheet for good.
Now for the bad news. Iâve found the open-source based DelfShip (formerly FreeShip) and now have a virtual Weekender on my desktop. :wink:
It was painful to get past the learning curve of how to use the software, but now that I have I can generate some really cool pictures. Entering the virtual dimensions of the Weekender was a little difficult. The software is designed to work from plans and lines-drawings with traditional offsets based on stations, waterlines, buttocks, and diagonals. However, the Weekender plans are really just a set of dimensions of individual parts. So station #1 on the deck has no relationship to station #1 on the hull bottom. Worse yet, the stations do not line up at all on any vertical plane. But, I got past all of that (mostly) and now have a VERY accurate model of the hull. I did make a mistake placing the rear cabin bulkhead, so the cabin is about 4 inches too short and the cockpit about 4 inches too long, but I know that some would deem this an improvement anyway. I might fix this later.
We were talking earlier about the head-banging nature of the horizontal Weekender boom and I suggested that simply inclining the boom by about ten degrees would solve the problem without changing anything but the shape of the main sail. So I was curious to know exactly how much you would need to incline the boom to clear my big head.
hock:
I am six feet tall and sitting here at the dining room table I require 38 inches of headroom which I will round up to 40 inches to account for any cushion I might be sitting on. So by placing a virtual crewman in the forward cockpit and allowing for 40 inches of clearance, we find that the end of the boom has to be raised by 14 inches. This reduces the area of the sail by about 4 square feet from 88.5 to 84.65, or about 4.5%, and moves the total center of effort of the rig forward by 1.85 inches and upwards by 2.69 inches, which I doubt will be noticeable.
Perhaps a picture would suffice â¦
![[Image: weekender_alternate_rig.gif]](http://tomsweekender.home.comcast.net/~tomsweekender/img/weekender_alternate_rig.gif)
So now the dimensions of the sail would change to luff=118in, head=68in, foot=127, leech=158, with the luff-foot angle changing from 80 degrees to 73.8 degrees. Again, an alternative to re-cutting the mainsail would be to install a set of reef points along this line to trice up the boom as required by crew constraints.
As to the aesthetics of the raised or inclined boom, I'll let you decide ... raised or lowered?
![[Image: weekender_rotating.gif]](http://tomsweekender.home.comcast.net/~tomsweekender/img/weekender_rotating.gif)
Ain't technology wonderful ???
Oh, by the way, for Paul Riccelli, Delfship thinks that transverse GM=5.3 feet about CG. But that is subject to some tinkering with plate thicknesses and densitites (55 lbs/ft3) that may or may not be entirely accurate, as the boat comes out to 550 lbs, (light) and I am not sure if the rig has been properly accounted for in the hydrostatics.
Got good news and bad news.
First the good news. Iâve put away my silly righting moment spreadsheet for good.
Now for the bad news. Iâve found the open-source based DelfShip (formerly FreeShip) and now have a virtual Weekender on my desktop. :wink:
It was painful to get past the learning curve of how to use the software, but now that I have I can generate some really cool pictures. Entering the virtual dimensions of the Weekender was a little difficult. The software is designed to work from plans and lines-drawings with traditional offsets based on stations, waterlines, buttocks, and diagonals. However, the Weekender plans are really just a set of dimensions of individual parts. So station #1 on the deck has no relationship to station #1 on the hull bottom. Worse yet, the stations do not line up at all on any vertical plane. But, I got past all of that (mostly) and now have a VERY accurate model of the hull. I did make a mistake placing the rear cabin bulkhead, so the cabin is about 4 inches too short and the cockpit about 4 inches too long, but I know that some would deem this an improvement anyway. I might fix this later.
We were talking earlier about the head-banging nature of the horizontal Weekender boom and I suggested that simply inclining the boom by about ten degrees would solve the problem without changing anything but the shape of the main sail. So I was curious to know exactly how much you would need to incline the boom to clear my big head.
hock:I am six feet tall and sitting here at the dining room table I require 38 inches of headroom which I will round up to 40 inches to account for any cushion I might be sitting on. So by placing a virtual crewman in the forward cockpit and allowing for 40 inches of clearance, we find that the end of the boom has to be raised by 14 inches. This reduces the area of the sail by about 4 square feet from 88.5 to 84.65, or about 4.5%, and moves the total center of effort of the rig forward by 1.85 inches and upwards by 2.69 inches, which I doubt will be noticeable.
Perhaps a picture would suffice â¦
So now the dimensions of the sail would change to luff=118in, head=68in, foot=127, leech=158, with the luff-foot angle changing from 80 degrees to 73.8 degrees. Again, an alternative to re-cutting the mainsail would be to install a set of reef points along this line to trice up the boom as required by crew constraints.
As to the aesthetics of the raised or inclined boom, I'll let you decide ... raised or lowered?
Ain't technology wonderful ???
Oh, by the way, for Paul Riccelli, Delfship thinks that transverse GM=5.3 feet about CG. But that is subject to some tinkering with plate thicknesses and densitites (55 lbs/ft3) that may or may not be entirely accurate, as the boat comes out to 550 lbs, (light) and I am not sure if the rig has been properly accounted for in the hydrostatics.