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Author Topic: Allegra 24  (Read 3330 times)
Adelie
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Boat Type: Dread Pirate ship RADIO FLYER

Ahrrrrrr!!!!

« on: May 16, 2011, 07:27:14 pm »

http://sailboatdata.com/viewrecord.asp?class_id=5434
I scaled various boat dimensions from the line drawing. I scaled both the depth and LOD to determine the multiplier to use.  Is this something that you would like done if the info is not available from primary sources, or do you only publish info from primary sources?

24.00   lod
27.17   loa
21.08   lwl
29.83   I
12.50   J
10.67   E
27.58   P
21.25   IY
9.50   JY
3.50   Draft
147   SA m
186   SA j
334   SA tot

If you are content with scaled dimensions I will provide them as the mood strikes me.
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sonosail
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Posts: 1865


« Reply #1 on: May 17, 2011, 09:16:44 am »

http://sailboatdata.com/viewrecord.asp?class_id=5434
I scaled various boat dimensions from the line drawing. I scaled both the depth and LOD to determine the multiplier to use.  Is this something that you would like done if the info is not available from primary sources, or do you only publish info from primary sources?

24.00   lod
27.17   loa
21.08   lwl
29.83   I
12.50   J
10.67   E
27.58   P
21.25   IY
9.50   JY
3.50   Draft
147   SA m
186   SA j
334   SA tot

If you are content with scaled dimensions I will provide them as the mood strikes me.

Wow!  Awfully kind of you.  There are a number of factors that MIGHT make this difficult.
1. Yes, I only publish rig dimensions that are read off of a sail plan or published in a brochure.
There are other sites where rig dimensions are published and I look them up occasionally when I don't have any for a specific boat. I never use them because I they are so full of obvious errors.
But I COULD just add a note saying "these rig dimensions are dervied form blah blah blah....."
2. It seems like you already know that every designer or builder has different definition of LOA. So one would need to be cautious when using this as a datum, (which I see you haven't done). This is further complicated with the presense of a bowprit etc.
3. I assume, in this case, that IY and IJ indicate dimensions for the staysail triangle. Currently I don't have fields in the database in which to put them, though they could be added in the notes section.
4. As you may have noticed, the quality and resolution of drawings that you see here vary widely in quality.

But when it comes down to it, ALL dimensions should be taken with a 'grain of salt'.  And as long as people are made aware of that, having a somewhat consistent way of calculating sail area would be very useful. Once basic rig dimensions have been entered, tot(calc)SA comes up, as does SA/disp. ratio.
As you may have noticed, there is a separate SA field that appears at the top.  This is used when only a total SA figure is available, but is not used in, nor derived from any calculations.

Just out of curiosity, what program are using to do this?
Sorry to be so long winded about this I just thought that it might be helpful to explain something about the basic setup.

So by all means. Be my guest. If your numbers seem to be in the ball park, I'd happy to use them with the aforementioned caveat.

Regards,
Randy Browning
Norwalk, CT
sailboatdata.com 
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Adelie
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Posts: 155
Boat Type: Dread Pirate ship RADIO FLYER

Ahrrrrrr!!!!

« Reply #2 on: May 17, 2011, 11:51:23 pm »

I checked both draft and LOD which were known quantities to determine the multiplier.  The agreed closely so I used the multiplier derived from LOD as it would be more accurate (longer base line to scale from).

The programs I used were Paint and Excel.
I saved your line drawing image to my computer, then opened it with Paint.  Paint works with bitmaps (though it can import or save Jpegs and whatever else, don't know or care much).  Paint has an x,y coordinate indicator at the bottom.  I used your rig dimension page to make sure I was getting coordinates for the dimensions as you defined them.

Coordinates were keyed into Excel.  A few formulas to back calculate the multipliers.  A few formulas to forward calculate missing dimensions and to round to the nearest 1/12th foot.

I have noticed others define the top of I as where the halyard meets mast rather than where forestay meets mast.  In the absence of a change in your definitions I will measure the way you define them in the rigging key page.

I would suggest that the remarks note that "Sail dimensions were scaled from above line drawing."  That is succinct and accurate and I will only use the drawing attached.

A
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A house is but a boat so poorly built and so firmly run aground that no one would think to try and refloat it.
Adelie
Member Emeritus
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Karma: +0/-0
Posts: 155
Boat Type: Dread Pirate ship RADIO FLYER

Ahrrrrrr!!!!

« Reply #3 on: May 18, 2011, 09:57:41 am »

If you would like I will send you the spreadsheet, I would have posted it here but .xls file extensions are not allowed.  I will need an email address to do so as pm's do not seem to allow attachments.
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A house is but a boat so poorly built and so firmly run aground that no one would think to try and refloat it.
sonosail
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Karma: +2/-0
Posts: 1865


« Reply #4 on: May 18, 2011, 01:18:39 pm »

If you would like I will send you the spreadsheet, I would have posted it here but .xls file extensions are not allowed.  I will need an email address to do so as pm's do not seem to allow attachments.
Very kind.
randy@sailboatdata.com
I certainly would like to see it. I just have to figure out the best way to use it. Once I see it, I may come up with an idea.
Very much appreciated.
Randy Browning
sailboatdata.com

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