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Old 03-28-2011, 05:27 AM   #1
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Steading Sails / Get home propulsion

This was liftef from another forum, and may help folks contemplating weather there is any value in adding a mast & sail.

*



For a couple of decades I owned an older Willard Horizon motorsailer.
The Willard had a full keel displacement hull with gently rounded
chines, a high bow and a rounded stern. The design was similar to that
of small sail working boats of a century ago with all that that
implies. Power was supplied by a Perkins 4-107 driving an 18" x 14"
prop. It was easily driven below hull speeds and had good seakeeping
qualities but tended to roll in beam seas.

The boat carried 260 sq. ft. of sail on a low aspect rig, a large
foresail and a smaller main. This is only about half the sail that a
cruising sailboat of similar specifications would carry and the Willard
could be considered to be sailing under perpetually reefed conditions.

On a calm day and with a clean hull it required 22.6 hp. to drive
PUFFIN at its 7 kt. hull speed. This estimate was confirmed by careful
fuel consumption measurements kept over several years. The best speed I
had ever gotten under sail alone in a beam wind was 5 kts. It took
approximately 8.2 hp. to move the boat at this speed under power.
Sailboat designers estimate that sails can produce about 1 hp. for each
27 sq. ft. of area under good conditions. The 260 sq. ft. of sail on
the boat should generate about 9.6 hp. of propulsive effect. The 1.4
hp. difference between the 9.6 hp. generated and the 8.2 hp. required
to move the boat at a 5 kt. speed is undoubtedly due to the drag of the
large non-feathering prop. In essence, the prop drag costs 15% of the
generated sail power.

To make only 3 kts. in a get home sailing mode, the boat will
theoretically require approximately 1.8 hp. Allowing for prop drag the
sails will have to generate about 2 hp. Under good sailing conditions
this would require 54 sq. ft. of sail, about that of a small sailing
dinghy or Sunfish. Obviously this is for ideal conditions. To be on
the safe side, a minimal get home rig for the Willard would require at
least 100 sq. ft. of sail. And, since get home conditions are likely to
be in horrible weather, the mast and rigging should be strong and the
sail made in storm sail weight. A low aspect ratio 12' x 10' standing
lugsail would suffice.

Scaling this data up for a 45' LWL, 45,000 lb. displacement boat, 3 kt.
get home speed, allowing for prop drag, would require 2.75 directly
applied hp. under ideal conditions. This could be generated by about 75
sq. ft. of sail area. Using a safety factor of 2, the get home rig
should carry 150 sq. ft., about that of a small daysailer. This might
require a 20' mast and a 15' boom. As in the previous case, the rig
should be suitable for storm conditions. Low aspect ratio rigs, perhaps
a gaff, spritsail or lugsail would be best for carrying the maximum
amount of sail on an unballasted boat. This type of sail is more
efficient in beam and following winds anyway. Even a square sail would
do but these require more rigging and knowledge than most of us want to
burden ourselves with.

I would like to point out that either of these minimal get home rigs
will have very poor sailing performance by modern standards. They would
parallel those of ancient Greek and Egyptian vessels. Pointing ability
would be almost non existent. The boat could make progress only in beam
or following winds. That's exactly the way the ancient ships sailed.
They stayed at anchor or rowed until the wind was favorable. Still,
with patience, a boat could cross oceans with this type of rig.

Getting back to the main topic. Steadying sails are not for propulsion
and are effective in stopping roll in beam winds. I have found a reefed
mainsail minimizes roll when motoring in choppy conditions. For the
Willard that meant about 50 ft. of sail area. The sail is sheeted in
tight amidships and offers no propulsion power. The boat takes up a
slight angle of heel and and the roll is attenuated. It is far more
effective, of course, to actually sail using the full sail area. In
that case the roll disappears almost entirely. We did most of our
cruising along the Atlantic coast in a motorsailing mode, using both
power and sail whenever the wind was suitable. Fuel consumption dropped
to low levels and the sails stabilized the boat.

Again scaling up to bigger boat size, a 75 to 100 sq. ft. sail would be
effective as a steadying sail. But, if you are going to rig a sail
anyway, why not go whole hog and make it a get home sail.

Riding sails are useful for high bowed or forward pilothouse trawlers
that sheer back and forth at anchor. These are small sails mounted at
the stern of the boat that serve as feathers on an arrow, keeping the
bow pointed toward the wind. A small 20 or 30 sq. ft. sail will usually
suffice. Recent research at MIT shows that a small riding sail will
substantially reduce anchor loads by minimizing sheering.

Finally, under the windy conditions in which get home and steadying
sails are used, there is a lot of stress on the mast and stays. The
rigging should be sized primarily for the stiffness of the boat not for
the sail area. While a 150 sq. ft. sail area daysailer may get by with
1/8" wire rope for mast stays, a trawler using the same sail might need
to upgrade the stays to 1/4". Most of the force on the sail is
translated to downward pressure on the mast and upward pull on the
windward stay. Typically trawlers are not constructed to resist deck
compression forces and the structure under the mast may have to be
reinforced or a compression post installed to transfer load to the
keel. Using sails as roll dampers is even harder on the rig than steady
sailing and the chainplates, the places where the mast side stays are
attached, must be firmly fixed to the hull structure and not just the
cabin sides. The ultimate disclaimer, of course, is to have your get
home or steadying rig designed by a good naval architect.

Larry Z
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Old 03-28-2011, 07:42 AM   #2
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RE: Steading Sails / Get home propulsion

Nice find FF. Good information.
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Old 03-28-2011, 09:05 AM   #3
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RE: Steading Sails / Get home propulsion

That is great info, Fred, thank you.* That is my plan for Delfin when and if we get free to head way south.* I know I won't be clawing my way off any lee shores, but I will be able to get somewhere.* Somewhere more or less downwind.

Thanks again.
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Old 03-28-2011, 10:21 AM   #4
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RE: Steading Sails / Get home propulsion

FF,

I didn't know you owned a Willard or that you are on WBO or did you get Zetlin's post from another forum? The Willard cruises around 20hp and it takes about 40 to make "hull speed". Our man Dan Peace now owns the boat previously owned by Larry Zetlin and is fully involved in a refit/rebuild. Much work was/is needed. Larry frequently made posts like this and most of the time he was passing good information. My problem w steading sails is that they work fairly well (depending on rig and size) but in really strong winds it would seem they just help capsize the boat. Of course as the boat heels the sail spills air and in calm seas that would'nt be a problem but what if you were a-beam to a 15' breaking sea w steading sail/sails up? Of course one would want to take in the sails before seas got to 15' * * ....I think. So I'm say'in the're a fair weather device whereas paravanes increase the seaworthy-ness of a boat. Anybody agree or disagree with this?
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Old 03-28-2011, 11:32 AM   #5
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RE: Steading Sails / Get home propulsion

My Coot is to come with a two-sail, fore-and-aft steadying rig.* Message from SH to sailmakers:
*
*
"Coot 35#06 Sail dimensions:
*
Main,
*Luff wire, pin to pin-480CM
*Leach-506CM
*Foot-272CM
*
Jib,
Luff wire, pin to pin-765CM *Leach-470CM
Foot-510CM"
*
I don't know how many square feet that translates to (can anyone calculate that?); however, I'd only expect the sails to provide minimal propulsion but noticeable*reduction of rolling under the right conditions.
*
Virtually all other*vessels with steadying sails have "handkerchief"-sized ones*which would seem to be of very limited usefulness.* If one is serious,*more sail area is*needed.
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Old 03-28-2011, 11:48 AM   #6
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RE: Steading Sails / Get home propulsion

Quote:
Nomadwilly wrote:*Of course as the boat heels the sail spills air and in calm seas that would'nt be a problem but what if you were a-beam to a 15' breaking sea w steading sail/sails up?
*

*The only time I would ever think one would be a-beam to a 15' breaking sea would be running some nightmare of an inlet.

Probably power or sail I would have no sail up. Without a ballasted keel I think one would be asking for trouble a-beam to breaking seas.

Bow on or stern to you* might stand a chance.* JohnP
*

*
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Old 03-28-2011, 12:00 PM   #7
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RE: Steading Sails / Get home propulsion

Quote:
nomadwilly wrote:
would'nt be a problem but what if you were a-beam to a 15' breaking sea w steading sail/sails up? Of course one would want to take in the sails before seas got to 15'****
*Vessels of some posters on this forum are three and four decks high (and remind of NCL's mega-cruise ship Epic).* Seems those boats would have their own stability problems in high winds, but unlike sails, cannot be taken down.

*
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Old 03-28-2011, 12:45 PM   #8
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RE: Steading Sails / Get home propulsion

FF - Thanks for posting the interesting power boat sail-detail information... I copied it into my "info" folder. I've been contemplating designing and installing dual mast (forward and rear deck) sail rigs aboard my Tolly. Figure I could get her to ply along at around 4 to 5 knts with the correct rigs up and their sheets wind filled. Each mast's base steps would be heavy duty and would span entire boat width with many points of fastening/securing/mast-stabilization. Both masts would be aluminum composite and maybe bi-folding at 7' center height of about 14' total height with maybe an additional fold joint at the base (so each could be fully dropped to go under bridges) Each having about a 7 to 8' main sail boom. The forward rig may even enable a skinny jib sail... All depending on final calculations. Re sailing in rough weather or odd wave/current conditions... NOT for me. Under those conditions, sales would be furled and both engines would be running! If/when I move forward into this endeavor I'm sure I will have many questions. - Happy sailing.... errrr boating! Art
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Old 03-28-2011, 02:47 PM   #9
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Steading Sails / Get home propulsion

A*picture of the Dorothy June, 58 ft Roughwater.** With the sails only they could make 3 to 5 knots.* When out in open water they motored and sail at the same time.* They installed fish stabilizers which had to be used when the sails where up. *The last I heard she was in thePanamaarea.* That was 2+ years ago.*****

Unless you are planning on doing long range coastal and/or crossing oceans it would be hard to justify the cost vs. the benefit.***


-- Edited by Phil Fill on Monday 28th of March 2011 02:48:34 PM
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Old 03-28-2011, 02:51 PM   #10
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Steading Sails / Get home propulsion

Power boats with rigs and also paravane stabilisers. This is a fairly common concept here in Aus especially on the older prawn trawler based displacement boats. I will attach a few photos of same. These boats are all in the 45 to 52 ft range. One of them I know paticularly well (Waverly with yellow sail covers) sails fairly well with enough wind. Has been known to have a huge MPS up at times. I was originally going to stick a rig on Tidahapah, even put in the chain plates and mast post but so far have not got around to it. have a lot of faith in the single engine concept.


*



-- Edited by Tidahapah on Monday 28th of March 2011 02:58:08 PM


-- Edited by Tidahapah on Monday 28th of March 2011 02:58:58 PM
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Old 03-28-2011, 03:54 PM   #11
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RE: Steading Sails / Get home propulsion

Benn . I have supreme faith in your "new" Gardner "sail package".
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Old 03-28-2011, 05:22 PM   #12
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RE: Steading Sails / Get home propulsion

Quote:
Phil Fill wrote:
A*picture of the Dorothy June, 58 ft Roughwater.** With the sails only they could make 3 to 5 knots.* When out in open water they motored and sail at the same time.* They installed fish stabilizers which had to be used when the sails where up. *The last I heard she was in thePanamaarea.* That was 2+ years ago.*****

Unless you are planning on doing long range coastal and/or crossing oceans it would be hard to justify the cost vs. the benefit.***



-- Edited by Phil Fill on Monday 28th of March 2011 02:48:34 PM
*Phil, I think you're right that the only justification a dude boat could come up with to offset the hassle factor and cost is offshore fuel savings and enhanced stability, coupled with a practical 'get somewhere' engine.* Some kind of keel is needed, but many boats have this - Delfin draws 7.5 feet which is pretty deep for a 55' boat.* My experience with years of sailing is that to weather, having a sail up when motoring increases speed at low power settings.* On a trawler, I think something similar would be true - a small sail added to the engine power will also increase speed and efficiency.* The most effect would be on a beam to broad reach where the wind power would simply augment speed, and range.* Off the wind, you'd get a nice effect, but it would have to be howling to be as effective as other points of sail.

We have active fins, that can be set to reduce roll along a less than vertical axis, in other words if on a beam reach you have 10 degress of heel, the system will reduce roll off that 10 degrees and not try to right the boat.

Haven't had the sails built yet, but I can't wait.....

*
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Old 03-29-2011, 04:20 AM   #13
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RE: Steading Sails / Get home propulsion

"I didn't know you owned a Willard"

I don't , just passing on some info.
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Old 03-29-2011, 10:13 AM   #14
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RE: Steading Sails / Get home propulsion

The couple that bought the Dorothy June where sailors and they got a really great deal as she had sunk up to the floor boards, the previous owner had the 671 rebuilt so at least it ran.* We are 43 ton when ready to cruise will approach 45+ tons and *5 6 drafts at the stern keel, so has a deep keel and heavy.* The 58 originally came with a forward mast, which that 58 still had.** So on our 58 the footing and chain stays are sill there.* Well, not actually as I took them off and filled them in, but I know where they were located.*

*

I talked to a local sail boat rigger about adding masts and sails,* However the cost is like 20K, so fuel saving would not be the main factor.* Having another get home means would be my primary reason for adding sails.* With the get home off the gen we can make head way, 3+ knots, so with the sail might be able to due 5+ knots.*

Our bow thrust has a forward thrust which was meant as a get home but the hydraulic chain drive to the main shaft works better. If we replace the main gen I will replace it with a bigger HP engine, not based the KW. The bow thrust, hoses and hydraulic pump are rated for 3000 psi, but with the present gen can on get about 1500 psi max.* The main gen as about 3,000 hours on it.*

Decisions Decisions Decisions!* If only I had a extra 50K!* **I might be able to get my wife to work full time again!* Then again hell might freeze over.*****
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Old 03-30-2011, 04:32 AM   #15
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RE: Steading Sails / Get home propulsion

For a couple of bucks you can get a pill for "Bestitis" and simply get underway.

No extra $50k required .

And with your fear of leaving the dock , I am sure an extra $500K would still find more to do.

You don't need the best boat in the world to untie, just good enough to enjoy the trip.

Youre there already.
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Old 03-31-2011, 01:51 PM   #16
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RE: Steading Sails / Get home propulsion

Like FF said we could probable throw of the lines and I already have the pills. The Eagle is our home, we use 24/7 365 days/year and we both still have jobs. So it not like we do not use the boat, and we have other land and water toys to play with.* Now 500,00.00 might get me to leave the dock!
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Old 04-04-2011, 11:04 AM   #17
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RE: Steading Sails / Get home propulsion

Just received this photo of my Coot with the steadying sails unfurled.

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Old 04-04-2011, 11:31 AM   #18
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RE: Steading Sails / Get home propulsion

Mark:

She's a terrific looking trawler! You will have fun on that boat.
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Old 04-04-2011, 11:39 AM   #19
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RE: Steading Sails / Get home propulsion

Mark,

Wish I had them on my Willy!
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Old 04-04-2011, 12:10 PM   #20
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RE: Steading Sails / Get home propulsion

Thanks, guys.* Time will tell whether I make effective use of the sails.* If nothing else, they provide a distinctive appearance.
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