Erik and Evi Menzel Ivey wrote:

A quick (un)related question regarding QCad - how do you guys calculate the CE for your sails?  I am using Barry's Excel spreadsheet and transfer the coordinates to QCad.  Is there an easy way of doing it in or out of QCad? 

Erik

 

Not that I know about. My method is to add a few well-placed cris-crossing helping lines on the Q-CAD drawing, and then print it out to a known scale, say 1:50. Then I find CE the old-fashioned way, by cutting out the sail and cross-balance it on a ruler. Then I can just measure the position of the CE relative to those helping lines, and transfer the numbers to the Q-CAD drawing.

BTW, the horizontal position of the CE on my range of master sails sits only about 50mm forward of the middle of the boom, so I sometimes use that for simplicity.

Arne

Erik,

you are right that I use to have 10% as the default value of the balance in my sails. However, Paul J Thompson has shown that the balance may well be increased to 20% without any problem. My sails with 70° yard can easily be made to set with a balance between 5 and 15% if the mast has been made long enough for it (no problem in your case). If 20% balance (or more) is to be used, then I guess it is better to lower the yard angle, as Paul has done.

My guess was that David’s sailplan could just as well be implemented with baggy panels as with hinges. Just remember that with baggy panels, the rules about boom rise and batten stagger when reefing do not work anymore. I use half-short batten parrels to keep the sail from moving further forward after the first panel has been lowered.

Arne

Arne -  thank you sir! I understand your comment re only relying on camber from the cloth and in general the concept of KISS (ignoring it has been a downfall of mine so please feel free to remind me.  Often). Of concern is that if I  don't do any hinge(s), the 15% overlap increases the mast interference in comparison to your more moderate 10%.

David -    I've created a folder in the JRA Box  and uploaded the latest drawing.  

Sounds like the single/front hinge is similarly situated bssed on both your.  If there is a second one, is it at 60% from the luff since the camber profile is straight aft of there? Or is the idea to position it where there is still a large  of changes in curvature?

Erik

Erik and Evi Menzel Ivey wrote:

David/Arne - do you have some rules of thumb as to hinge locations with respect to max camber?

 

Erik,

Now I had to look up newsletter 24 to check the position of the fore hinge on my Malena. It sat 27% aft of the luff. Most of the time that hinge worked well, but sometimes it flicked the wrong way. I solved the problem by adding a throat hauling parrel to shift the top of the sail aft. You should be all right if you fit your (one and only) hinge to 30-35% aft of the luff, and I guess that will put the max camber point in a good position as well.

However, the cambered panel sails have worked well for me, so I have never felt any need for bothering with hinged battens again.

Arne

ueli lüthi wrote:

hi annie

i see why it's better to store the files 'on site', and i do this for my stuff. but as the files are not from me, i won't upload them anywhere.

i just said that there's no need for an own account to download files from a dropbox – even if it looks so…

ueli

Sorry, Ueli, I was writing in haste - wanting to get to work, and got myself mixed up in the thread. I was actually asking Erik if he could put his files on our site.  It would be great if we could just upload things directly to the website and I do realise it's a bit of a bind having to join Box, but unfortunately,  Wild Apricot doesn't give us unlimited storage on the website, so using Box is the only way around it.

I think it's fantastic the way we share our knowledge and information and have been incredibly grateful for it myself, many times.  I guess that's why I'm so pedantic about trying to organise it in an accessible way for future members.