sail footage questions.

[merlinron]

when deciding on sail footage for boat intended for inland waters, easy relaxed sailing, in an area where winds can vary from a zephyr to 10-15 at any time of the day, how do you decided how much canvas to give it?.
17' LOA.
15.3' LWL.
7.02' BM.
6.42" WLB.
L DISP. 1420 #(two crew will be most common)
430# int. ballast.
i have used john welsford's method of sail area calculation and can put a sailplan on it that will need a first reef in about 14kph. winds( 126' sq., to facilitate the easy, no-hassle sailing), but i am wondering if that's going to give enough drive in really light winds.
i can power that up to about 140' sq. that will require a reef at about 10 kph.
i have drawn plans that are up to 160' sq. but don't want to bother with that kind of busy sailing for short afternoons on a local lake.
as drawn the the boat carries a ridiculously small standard gaff or bermuda plan that measures out to 107' sq. and is listed in the specs as 10mkw.(meter/kilowhatt?). i suspect this is because the boat is designed in a coastal area of very gusty conditions. it also shows an optional plan of 15mkw., which is physically about 127'sq. when measured, but is burmuda and i want gaff. regurdless of bermuda or gaff, i have manged to come up with a plan (126') that keeps the same center of effort.
i am sure the boat can carry a bit more sail than what is on the print, considering inland sailing....any advice besides the obvious, "talk to the designer"....... extreme language barriers have caused difficulty there.

[George Ray]

I think the question to ask is "what if I had to depend on sail power alone" and did NOT have the option of starting a motor. Thinking like that you might look at "American Small Sailing Craft" by Howard Chapplle and see what was used in the 'pre-motor' era. Having the means to reef quickly and easily is of course a requirement.

[merlinron]

hi george, thanks for the reply,
there is no provision made on th plan for aux. power, although i had thought of adding a trolling motor for getting off/ approaching the dock .
reefing is a given as the original drawings are inteded for coastal cruising in areas of high wind fluctuation. a reef or two on my sails will be fine and expected.... to be used in extreme conditions.... remember though, my intended use of inland protected waters( small local lakes) and easy afternoons of dry sailing.....the boat will live on a trailor. if the wind is blowing too hard, i don't go out.
my question concerns deciding if i should go with enough sail for the light airs in my region and reef down at say 10 or so kph., or canvas it to be good at 15kph figured at about a 20-25 degree heel and loose some light air push for the sake of not having to deal with reefing. covering a wider range of conditions sounds to me like it would make it a little more easy to enjoy an afternoon of puttering around the local lake, but i don't know at what point i would be unhappy with light air performance for the sake of not having to reef if the wind picks up a bit for a few hours and turning an enjoyable sail into a balancing excersize in a light boat.
i made no mention of aux. power and fully intend to be able to reef in if necessary, but is it customary to put reefs in a small craft at every 10 or so kph of wind load?

[Bruce Hooke]

To some degee it may depend on your attitude towards sailing. If there is so little wind that I am constantly tweaking things and hoping for another puff to keep the boat moving, I'd rather be paddling a nice canoe or rowing a good boat than messing around with a sailboat. However, if you enjoy "playing" the wind and trying to work every puff then light air performance may be more important to you.

That said, knowing how light the wind often is on inland lakes, I'd lean towards the larger sail plan and figuring that reefing, if it becomes necessary, will not be hard and will, most of the time, probably be taken care of on shore anyway.

One thing I would watch out for is how much you are raising the center of gravity by increasing the sail area. This especially applies to mast height since when you reef the mast stays the same height whereas the gaff comes down a bit, bringing its center of gravity down as well.

[merlinron]

that's the stuff i needed to hear bruce, thanks!
i can maintain the same 17' mast height all the way out to about 150 ft. of sail, so for all but the most extreme fottage i, personally, would be brave enough to put up mast length won't be an issue. i've got one drawing with 161 ft on it, but the peak wind load per sq. ft. of sail indicates a blow over at about 8 or 9 kph!( i certainly don't want that)so the cg of the mast more or less doesn't change in the range i'd use. the height of the gaff (just under 4 lbs) will certainly move the cg up as the sail footage increases, that's tollerable, but more importantly the center of effort goes up along with it, and that's what you have to look at with a shallow draft and 430 lb. of internal ballast. as the CE goes up it chops away at the righting moment fast in terms of how huch footage at a given wind speed the righting moment can resist, i don't want to come in from a sail with combing rail divits in my arse all the time!!. i don't want a boat that looks rediculously under canvassed for fear of blow overs, but i don't want to put so much on her that i have worry about what the wind is doing every second, that's just not enjoyable to me. i was kind of hoping i could come to happy medium with maybe one reef for days when the winds do blow 15 or so, but with keeping the sail plan down to a footage that will handle more than 10 but less than 15. i don't have a good idea of what kind of light wind drive i'll have. i'm sure that what won't handle 15kph will be entirely happy at 5kph on a warm saturday afternoon. is it a reasonable assumtion to set the unreefed plan at a max of say...12-14 kph mathamaticaly, and a at reef at about 15. anyone have a boat about my same size and displacement? how are the hartelys or the glen-l's set up, i have looked at thier specs, but there's no info on reef footage on them. bob smalser has a hartely doesn't he?

[Bruce Hooke]

Hopefully others will come along who can give you more definitive guidance than I can. I will just throw out a couple more points to consider:

1. When it is blowing 10 knots the gusts could quite easily be hitting 15 knots. In other words, there is a limit to how far you can take the analysis of "I'll do this when the wind is blowing 12 knots and that when it is blowing 16 knots."

2. Especially on inland lakes (at least east of the prairies), it is my quess that steady winds of over 15 knots are relatively rare. Even on the coast of Maine, where I have done most of my sailing, there are plenty of summer days when the wind never breaks 15 knots and whenever I am around small lakes and ponds in the summer it seems like much of the time the wind is barely blowing. This is less true on bigger lakes. I've certainly seen it blowing pretty effectively on big lakes like Lake George in New York. In the fall and the spring you are probably more likely to encounter windy days...

[merlinron]

your first point is just exactly what is causing the problem.....where do you draw the happy workable line????
i've been watching the wind speeds here just for that reason (#2), and to get a good idea of what 10 mph. feels like. two days ago we had a fairly steady 8-10 mph day..... that's actually a good amount of wind, even at ground zero, for a small light boat! ya, when i think about it, 15 mph isn't very common here, either, maybe that's a bit high for a first reduction .
maybe i'm getting a little anal about it, i just want to get it right the first time. maybe a couple of smaller reefs on a light wind sail will be the way to go. i realize, as you pointed out earlier, it's not that hard to do and it will most likely be taken care of at the dock.
your points are well taken...thanks.

[Thorne]

No interest in a foresail? Using a jib/genny would vastly increase your flexibility for light wind conditions, plus allow you to vary sails for varying conditions.

What boat design -- is this a catboat?

[merlinron]

thorne,
yes, there is a fore sail, a non-overlapping working jib on a sliding club, included in the footage. all the sail layouts i've been looking at have between 35 and 40 % ratio, so the jib is relatively small. i know i can play the jib size to balance when it blows, but as it is on a club, i would prefer to be able to work with main footage first and most likely leave the jib alone, i'm just out sailing for an afternoon mostly, with very occasional overnighter on some of the bigger lakes. if the wind blows hard enough to consider a small jib needing a reduction on a small inland lake, one might consider not going out. there won't be any situations where i need to reduce sail to get out of a storm out in the middle of no-where. the boat is a raised flush deck light disp. cruiser. as mentioned designed for coastal cruising, with fairly high freeboard , as many of that type have, to increase stability numbers. in my use the coastal abilitiy means nothing to me, i live in the middle of wisconsin, but i've always liked the flush deck look, so i have knocked 4 inches of freeboard off it's profile stretched the station intervals 5% to get 17 ft.( adding 8 inches of length to the boat). it's all only on paper, at this point. the underwater volume gained 1-3/4 cu. ft. of disp so i added 100#'s of ballast to put it back on it's water line. i did a simpsons rule calculation to arrive at the new dispment, the boat is hard chined and straight between chines, so area was real easy and accurate to find, just a bunch of triangle shaped areas at each station. the result is a very nice, classic looking narrow sterned day sailor with overnight accomidations and 34 inches above the birth under the flush deck, maybe not quite enough to sit totally upright, but if you're in the cabin you're most likes asleep. the reduction in free board did not change the sheer's line, it simply brought it closer to the waterline and the profile looks allot less chunky for a 17 ft. boat. point of vanishing stability is still well above 100 degrees and the change did absolutely nothing below the waterline beyond making it drive just a tiny bit easier. actually the POVS. went up abit between after modifications due to the increase in ballast and keeping the same waterline beam. the cg did drop about an bit with lowering the deck structure, but that's a good thing. i have done all the pertinent stability math that i can do and non of the changes i made added up to hill of beens as compared to how it was originally drawn.
which boat is it, you ask.....ahhh, i'm almost afraid to let you know. i've been on here before with it and got a ton of advise to abandon it because it was a free design, unproven, etc, etc,. appearantly, to some, free means no good at all,i just don't think that way. there are a couple of free plans in this sites design forum that those same people complimented, yet this one they scoffed at. as stated before, i picked it because i liked it, not because it was free, although ,free is a good thing.....sztrandek..
there have been a few built overseas and comments on them are all good, so free don't always mean no good. i have a proflie sail plan drawing done now and in good condition, but it is 16 x 22 and won't fit in my scanner. i'll get it reduced and put it on here if i can figure how to. i think most everyone will like what they see.

[Thorne]

Good luck with your design and build -- sounds like quite a project.

Don't know about winds in your area, but out West we certainly can't rely on judging the wind at the dock -- they come up, they go down, and they gust, but they aren't predicatable. So any sail rig I consider needs flexibility on the water, either reefing or rolling up the main, and dousing or changing the jib.

[merlinron]

do you sail coastal, in the bay, or inland? i have read that the bay winds are unpredictable as can be. winds are quite different 1000 mi from a sea coast,heck, thery're entirely different 10 mi. out on lake michigan than they are 10 inland, much more predictable and steady state, unless it's an abnormal day with a predicted storm approaching, then, obviously some flexibility is called for. i'm talking about comming home from work and dragging the boat down the local lake for few hours, the wind you have is most likely going to be the wind you'll get all evening, a call can be made at splash, with a good amount of confidence. i realize that coastal winds can be unsettled for no appearant reason at all and most of the advice i'm getting is comming from coastal areas. if i were to be there, i don't think i'd have the questions i do, it would be taken for granted that flexibility is paramount. most everything you read about the matter is based on coastal experience and as well, so it's kind of hard to compile a base of information to work with.

[Thorne]

Well in a 14' dory I sure don't do much coastal sailing! Did a bit in my SJ 21 years ago, but sailing protected waters in the Bay, California Delta, and various mountain lakes is more suitable for smaller boats.

Winds here are very complex, but the main factor is the Central Valley (old inland sea) getting VERY hot (it will be 107 degrees this weekend in Sacramento) and creating a partial vaccuum as the hot air rises.

The cold air is drawn from 10 miles offshore where the currents make things cold and foggy, and pulled over 60 miles inland along the SF Bay and rivers and any low gaps in the coastal hills.

This means that on hot summer afternoons you had better be off the Bay by 2pm unless you are ready for 30knot+ winds and swell -- which can combine with outgoing tides to make some really fun rips at times. Nothing to compare with the Pacific Northwest and Puget Sound tides and rips, mind you, but still plenty bumpy.

Yes, when I look at the boat plans from back East and elsewhere showing tall masts and big sails on small boats -- you can tell they are 'not from here'...

;0 )