Sail size for a light pulling boat?

[MushCreek]

Yes, I know adding a sail to a good rowboat spoils her for rowing. Bear with me a moment here. I'm building a Peregrine 18 rowboat. 47" beam, 135 lbs. or so empty, with a fairly round section to the hull. I see all sorts of sailing canoes that are much narrower, so I think I can pull it off. I plan to make a removable mast support and leeboard mount. All of it will be easy to remove except for a permanent mast step fastened to the keelson. I'll only rig it for sailing on ideal sailing days; the rest of the time, I'll row. Yes, I could end up rowing home when the wind quits, but I don't travel far from shore any more.

I'm thinking a low rig, either gaff, sprit, or lug. The question I have is on sail area. I'm thinking a 60-65 sq ft pram sail would work well, with the crew still being able to hold her up unless it's really blowing. I'm thinking more along the lines of a leisurely cruise, calm enough so that I could each lunch and still handle the boat. I'm not up for hiking straps any more!

My plan is to have two cross members that clamp to the gunwale (inwale?), connected by a sturdy piece running fore and aft. This piece would have a place for the mast to go through, with the aforementioned mast step at the bottom. The rear cross member would be built and reinforced for one (or two) leeboards. I know leeboards can have a LOT of force on them, and I don't want to have to have lower supports on the hull, so the leeboard mounts will have to be stout.

With all of the above removed and stowed, she goes back to being a mild-mannered rowboat. I'll probably do a mock-up at first, with a polytarp sail and common lumber spars for proof-of-concept.

I'm mostly interested in feedback on sail size and type. I'm gonna try it, critics be darned. If I fall on my face, well, it won't be the first time.

[Peerie Maa]

Yes, I know adding a sail to a good rowboat spoils her for rowing.

Not necessarily.
The type of skiff that my grandfather worked.
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Thanet werry.jpg

[johngsandusky]

I think you're in the ballpark. A lot of it depends on the sailor. Using your canoe comparison, some people want a 15 sq ft rig, others 100. I've used clamp on rigs on canoes, kayaks and dinghies, they work.

[timo4352]

My 15 foot gunning dory had 55 sq ft sail and it was plenty.

[swoody126]

my 16' Swampscott Dory carries 99sqft

sw

[Todd Bradshaw]

These are the basic dimensions for a standing lugsail for a Penobscot 14. When built to 90% of these dimensions you would end up with the exact same proportions, but 63 sq. ft.

!PENOBSC2 copy.jpg

Penobscot 14 copy.jpg

[Canoeyawl]

I have an 18' x3' 100 lb pulling boat to which I retrofitted sails...

A pair of class C canoe rigs seemed to be just right most of the time.
If it really breezed up, I had a separate mast step to use just one of them
Sailing a small boat is always about human ballast being able to suit the conditions.
(I think every boat I have has sails and oars)

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[MushCreek]

Yes, in a light boat, crew weight and ability plays a major role. I used to sail an 8' short board with a 6 sq meter sail in 20 kt winds, but that's a whole different animal. I'm thinking more of sliding along, smoking a pipe (if I smoked). IOW, more suited to a guy going on 70, who is not in that much of a hurry. Of course, I don't want it to be dull, either...

That Penobscot 14 sail at 90% should be enough. As I said, I'm going to build a cheap lash-up first to test it out. If it's too much, I can always scale it down more.

[Winter Hawk]

In the late 1970s, early 80s I had a two person Folbot with a sail rig. I don't remember what it had for a mast step, but the clamp on rig stretched across the hull and was clamped to the cockpit coamings. What I remember, there were a piece of angle steel at each end with a bolt and wing nut to hold the leeboards. No bracing fore and aft, and a lateen sail. I don't remember how the sheet was rigged.

Hope this helps.

[Ian McColgin]

A sailing rig will not "ruin" a great rowboat. It just won't sail as well as a boat designed to sail. What's really hard is to make a hull that's both a great rowboat and a great sailboat. Best I've seen is pretty good at each.

So if what you have is a great rowboat, then rationally you'll. use the sail off the wind and row to weather. A spritsail with a boom or a lug will be the thing.

Edited to add: From my observation (Where's Michael when we need him?) really great rowing boats have very fine waterlines at the stern. For a boat to sail well, she needs a bit more back there.

There are exceptions: The LFH dink for his Marco Polo rows incredibly well light or laden and sails surprisingly well if not overburdened.

[robm]

A buddy of mine who used to commute to work at a boat shop, from his sloop anchored in Vancouver harbour, in a 13 foot salmon handliner he had rebuilt from scratch used to say: "Sailing upwind is a waste of time. Rowing downwind is waste of wind." His sail was about 55 sq. ft, and sprit rigged.

[Clinton B Chase]

A buddy of mine who used to commute to work at a boat shop, from his sloop anchored in Vancouver harbour, in a 13 foot salmon handliner he had rebuilt from scratch used to say: "Sailing upwind is a waste of time. Rowing downwind is waste of wind." His sail was about 55 sq. ft, and sprit rigged.

I'm going to use that quote - it is a bif belief of mine!

[Ian McColgin]

Great saying. Making it mine own . . .

[Dryfeet]

Ian's comment prompted a thought on something I've experienced. Those fine waterlines aft mean that when sailing you still need to keep your weight centered similar to when rowing. Consequently, steering needs to be considered, I.e. reaching the rudder when 8' forward of the transom. A push pull tiller is likely the best solution but rigging and unrigging it once out on the water could have it's own challenges.

As for sail area for the type of sailing you describe, I've enjoyed my Joel White Poohduck design with only the lug of 67 sq ft and would have been comfortable often with less. I vote for Timo's recommendation of around 55 sq ft sail area as you are 7" narrower and with a softer turn of bilge than my Poohduck.

[rgthom]

I will be the contrarian here and argue for keeping a rowboat a rowboat. I have tried a couple of downwind rigs on my camp cruising rowboat. They work, but in practice carrying all the rig, and frequently setting and striking mast and sail, is not worth the fuss. Upwind, only rowing works. Downwind, the rowing is easy! In the typical summer wind of the Sacramento Delta, my downwind speed is about 3 kts doing nothing, 4 kts rowing easy, and 5 kts raising sail. I prefer to keep it simple, just a pair of oars.
- Rick

[robm]

If people are going to start using that quote, I better attribute it to the guy that first made it: Brian Genn. I knew him when he sublet space at Alder Bay Boats on Granville Island. I am not sure where he is these days.

One reason for the sprit rig was the very short spars, so it took up little room when struck. I believe he used an oar in a dedicated rowlock near the aft end of his double-ended handliner to steer.

[john welsford]

it really depends upon your intended use, or your ambitions as the case may be. If you want to just sit quietly in the bottom of the boat and let her slide along gently, a second hand Optimist rig would do that for you, ( cheaply) but if you're serious about sailing the boat, about 85 or 90 sq ft would be about as much as you'd want, or need.

John Welsford

[overland]

I had similar thoughts. But how does one know or figure out where to place the mast and the leeboard?

[john welsford]

I had similar thoughts. But how does one know or figure out where to place the mast and the leeboard?

A very rough suggestion, without a lines drawing to give the definitive answer, would be to put the trailing edge of the leeboard at 50% of the distance from bow to stern, and the mast so positioned that the geometric centre of the sail is 10% of the waterline forward of the 50% mark.
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But, its hard to be really accurate without that drawing.

John Welsford

[MushCreek]

Working out the locations for the various components can get complicated, and sometimes inaccurate. That's a big part of the reason that Phase 1 will be clamp-on parts made of 'disposable' lumber and a polytarp sail. In addition to the lateral resistance of the leeboard/centerboard/daggerboard, there's the lateral resistance of the hull itself. Throw in the fact that the Center of Effort of the sail moves around depending upon trim and wind velocity, and it's a tough call. Since I have no formal training, I'll simply review similar designs and use them to get a starting point. I've designed and built a few small sailboats over the years, and none of them had excessive helm bias or other annoying habits. Dumb luck, or educated guesses.

[jpatrick]

Have you asked John Brooks about adding a sail? He was quite approachable when I built my Somes Sound. I always contacted him by email.

Jeff

[overland]

A very rough suggestion, without a lines drawing to give the definitive answer, would be to put the trailing edge of the leeboard at 50% of the distance from bow to stern, and the mast so positioned that the geometric centre of the sail is 10% of the waterline forward of the 50% mark.
.
But, its hard to be really accurate without that drawing.

John Welsford

I have a drawing--of the Chester Yawl by John Harris--with a sprit rig and a daggerboard. If I know the position of the daggerboard, does that tell me the position of the leeboard, too?

[johngsandusky]

Somewhat. A leeboard can swing, changing it's angle. When I rig a boat to sail, I do look at drawings and pictures, take measurements, and make my best guess. Leeboards can be moved too, if you don't bolt them on.