Page 1 of 1

sail measurements, please

PostPosted: Wed Aug 16, 2006 12:23 pm
by calden
Hey all:

In acquiring new sails from an independent maker, I'm wondering about their specificed measurements. I pointed them to the DS Handbook on this site and the accompanying drawing, but the measurements in the buyers agreement don't seem to be what the boom band and mast band indicate for "allowable" luff and foot lengths. Are sails ever made to those "maximum" luff, leach, and foot lengths, or are these figures to account for stretching the sail, and in fact a regulation mainsail has slightly smaller dimensions?

I'd appreciate it greatly if someone could take a few minutes and measure your Jotz or North or other "stock" DS mainsail and give me those figures.


PostPosted: Wed Aug 16, 2006 5:58 pm
by KaiB

Iff'n you can wait till Sat AM, I'll get you my (orig O'Day sails) numbers.

It will be interesting to see the range of numbers as you get them.


Re: sail measurements, please

PostPosted: Sat Mar 30, 2019 11:47 am
by DesertRat
This is an old thread but...

I was just looking at adding reef points to my old DS I sail, so I wanted to measure to get proportions. Everything online says that the mainsail should have a foot of 10' and a luff of 20'.5. As my sail lays out on the floor it has a foot of 9' and a luff of 18.5. When I raise it on the mast, I have to stretch it pretty hard. I'm imagining that with all that stretch it might eek out to the standard dimensions.

Standard dimensions say SA for the main is 102. So looking at putting in reefs at 25% and 50%. I saw someone else here who suggested the first reef would go in at about 28" above the tack. Sounds about right. Another reef 13' down from the head would put it at about 50%.

I'm a rather novice sailor. I've never used a reef in actual practice. But I've taken a capsize in a dinghy once because I should have used a reef but didn't. Two reefs sounds like an awfully lot of adventure for me. Not sure I can handle that much adventure.

Re: sail measurements, please

PostPosted: Sat Mar 30, 2019 1:17 pm
by GreenLake
@DesertRat. The Zombie thread exhumation business has been quite thriving of late ;)

You are right, the sail measurements you give are for when the sail is set, because they are taken on the mast and boom and limit the maximum distance of head and tack, tack and clew respectively.

As for reef placement - there are other practical details that you should take into consideration. We have had a recent thread on putting in reef points titled "Sailrite Reefing Kit". It's in the "Rigging" section. Reefing is on of those topics that require both modifications to the sail as well as to the running rigging. I wonder whether we should not merge those to sections of the forum . . .

I've put an answer to your other questions there.

Re: sail measurements, please

PostPosted: Mon Oct 21, 2019 2:27 pm
by RobH912
So I was looking at the Day Sailer Sail Inventory Measurement Certificate page of the DSA Measurement Certificate, looking for the "official" main, jib, & spinnaker sail measurements, and found the attached measurements which I captured with a screen shot.

Wanted to measure the sails I already own to see if they would meet DS rules.

Thought that Main sail would have a luff, foot, and leach measurement like the jib does; but don't see that here. Spinnaker measurements are pretty straight forward also. I don't really understand the measurement categories provided for the main sail. Going to have to look for a picture of those items and then try to sketch them out

Are there main sail measurements (luff, foot, leach) in addition to those listed on the certificate?

Re: sail measurements, please

PostPosted: Mon Oct 21, 2019 6:55 pm
by GreenLake

what you posted is just a form that the class measurer fills out (with enough reminders to be able to spot a measurement out of range). It does not give the actual definition of what is being measured, nor the measurement procedure. For that you need to consult the class bylaws on measurements.

Here's a drawing from that document giving the dimensions for the main:

Drawing 8.1 from DS Class Bylaws
Drawing-8.1.JPG (77.69 KiB) Viewed 2651 times

Re: sail measurements, please

PostPosted: Mon Oct 21, 2019 10:48 pm
by RobH912
GL - thanks for sending through the link to the class by laws on sail measurement which is exactly what I was looking for. Includes pictures... always helpful :D

Didn’t understand mast bands / measurements on the bands either, see that picture also.

Good info!

Re: sail measurements, please

PostPosted: Mon Oct 21, 2019 11:01 pm
by GreenLake
Bands: rather than defining the size of the cloth, the rules define how far you are allowed to stretch it along mast and boom, that is, it has to be kept inside the bands. By marking the bands, competitors can be assured that nobody uses a larger sail (if they did, it could not be stretched flat, which isn't fast).

Re: sail measurements, please

PostPosted: Tue Oct 22, 2019 8:41 am
by RobH912
GL - OK more good information and I now understand the bands and see how bands would be necessary to establish the one design sail measurement standards.

To apply bands & to measure the main sail off the boat would I mark out the bands' measurement points (foot, luff, leach) on the floor and stretch the sail to those points? If longer than the marked points then the sail is not legal? If shorter than band measurement point sail is OK but just not as competitive ?

Do sails stretch as they get older / softer?

I headed down this path as I have been thinking about swapping out sails between the two DS before I sell one and wanted to check on measurement standards.

Re: sail measurements, please

PostPosted: Tue Oct 22, 2019 7:45 pm
by GreenLake
If you are worried whether a sail is too large, you could, of course stretch the luff and foot for your measurement. (If the sail can be stretched a bit more, it means it can't be completely tight under race conditions. If a bit less, you might lose some area, but, those are old sails).

Overall, I'm worried that you are overthinking things.

If your goal is to be competitive in sanctioned races (those for which you will have to have a valid measurement) you will need to purchase a new set of sails to order from whichever supplier is currently seen as "competitive". Whatever set you keep can be your "practice" sails and you would pick that set based on which sets better on your boat. (Or you may be able to tell some difference based on overall impression).

About every couple of years, you would invest in a new set. At that point, your previous racing sails become the practice set.

If you compete in non-sanctioned races, who cares. Pick whatever sail looks best and use that one until you feel you need a new set.

I sailed with a set of sails that may have been original to the boat until the evidence became overwhelming that they were blown out (my skills had improved to the point that I could tell the difference and therefore justify the expense). That set of sails I used for a number of years until the jib in particular couldn't be set properly. I added a leech line (as a stop-gap measure that allowed the jib to be set again) and, because I had started racing the boat, if only in non-sanctioned events, I eventually sprang for a replacement.

Re: sail measurements, please

PostPosted: Wed Oct 23, 2019 8:03 am
by RobH912
Overall, I'm worried that you are overthinking things.

GL - I laughed out loud when I read this comment last night, because I was thinking that all of this just seems much harder than it should be. :lol:

My original post on this thread I was just looking for 3 measurement numbers...

Are there main sail measurements (luff, foot, leach) in addition to those listed on the certificate?

If you and I were sitting around a table, or on a phone having a conversation on this topic it would have taken less than a minute to resolve, maybe two minutes. On an Internet forum questions and answers sometimes are hard to interpret in context or the questions / answers seem to take a life of their own... the answer was in the diagram you posted... Luff 20' 6", Leech Chord 21' 9", Foot 10'

From several previous posts this summer I've mentioned that the sails (main & jib) on the SLI boat seemed too big for the mast & boom, maybe a result of the tabernacle conversion (??), but not sure. They are North Racing sails plus a spinnaker, they are in pretty good condition, and sail well. Sails for #2444 seem to be newer (but not sure), Intensity brand sails, but no spinnaker. Now that I have the main sail measurements I can measure both main sails and see if that information provides me with any new insight, e.g. maybe the main sail is actually too big, helping me make the decision on do I swap sails when I sell one of the boats. Just going to roll them out on the lawn and take measurements.

GL - you have helped me a great deal with all of your forum replies / sharing your deep DS knowledge base this summer to my still occasionally newbie type questions, and I really do appreciate all the information very much.

Thank you!

Re: sail measurements, please

PostPosted: Wed Oct 23, 2019 5:35 pm
by GreenLake
@Rob, glad I can be the source of some innocent levity!

Yes, some simple things don't come through on a forum -- sometimes because the framework of the people in the communication isn't aligned in some way that's not really obvious.

If your mast and boom have the proper measurements between bands, I would expect the North Sail to fit; being in the business for selling sails to racers, anything to the contrary would astonish. Like for like, I would prefer a set of North over Intensity, but a well-worn set of the former may no longer have any advantage. That's the kind of thing that you can't diagnose remotely.

Whichever set you retain, there may be wind conditions where the other set might have worked better: we have so many really light wind days here that when I got my new sails, one of the first things I noticed was that they were too stiff to set properly in a drifter. The old, original, and worn out sails however, had been coping with those conditions quite well - they were soft and required little wind to coax them into some semblance of a shape.

Still, overall, I'm glad I did the upgrade.

Anyway, that's what I was after with my comment about overthinking: you may be chasing imponderables at some point.

Make your choice, and live with it - go sailing.