# What makes a good light air boat?



## AndrewMac (Sep 11, 2009)

I'm in the process of researching an upgrade - looking to find something in the 28-32 ft range. One of the characteristics I've identified as being important is the ability to sail well in light air as we have a lot of 5-10 knot days in the waters I primarily sail. So, my question is: what makes a good light air boat? I assume it is fundamentally physics and relates to things like: sail area; rig; hull design; keel design; weight....I'm probably leaving something out. I am sure it is a complex answer - if it's easier to point me towards a book, that would be great too. Also, examples of boats known to be good in light air are much appreciated.

Thanks


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## Diva27 (Nov 2, 2007)

Couple things for starters:
1. Lots of sail, of course, but in a tall rig, to get sail as high as possible due to the wind gradient. The wind blows more strongly the farther you get from the friction of the water. On the Great Lakes it used to be common for boat builders to offer a "tall rig" version of a design, sometimes with pretty much the same overall sail area. In light air the gradient can mean almost no wind down at the boom but useful wind 30-50 feet up. I've had days on my 27 where it's a dead calm in the cockpit but my masthead wind sensor is showing 7 knots.
2. Low wetted surface to reduce parasitic drag. Light winds mean the boat isn't going to achieve hull speed, and at lower hull speeds, parasitic drag is proportionally more of a factor than wavemaking drag. The closer you get to hull speed, wavemaking drag soars in comparison.
Others can chip in.
cheers


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## JohnRPollard (Mar 26, 2007)

Good comments by Diva above. The wetted surface area of the hull really comes into play in light air. Once winds build, there is normally more than enough hp available to overcome the hull drag, but in light air it makes a big difference.

Plenty of sail area too -- in an efficient rig design -- relative to the vessel's displacement. Sail Area-to-Displacement (SA/D) ratios are a good place to start when comparing similar sized boats. Typical, relatively conservative cruising designs will show SA/D ratios in the 15.5-16.5 realm. Once you start seeing numbers approaching 17 and above you are getting into a more performance oriented design, which theoretically should offer better light air performance.

But those aren't the only issues, and you'd be surprised how some seemingly stodgy designs can move along well in light air. The Sa/D ratios are based on 100% foretriangle measurement, so don't reflect overlapping genoas or staysails or any of the other tricks that allow a boat to pile on sail area in light air. 

Also, there are things you can do to improve a run-of-the-mill design to help eek out light air performance: Use smooth racing bottom paint; keep the bottom clean of scum; install a folding/feathering propeller; get a spinnaker; purchase new working sails; don't pile the boat full of every convenience and sink it below its designed waterline; etc.

Having no idea what your budget is, or how you plan to sail the boat (family cruising, racing??), it's difficult to make suggestions. But in that size range I like the J-32, the Beneteau First 10R. They are a bit tight for family cruising, but definitely fall more on the performance (cruiser/racer, racer/cruiser) end of the spectrum.


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## tommays (Sep 9, 2008)

We race and old C&C 35 which as 35' boats go is on the light side compared to a lot of current boats that added all kinds of creature comforts and the weight that goes with them 

In are racing adventures we do really well in winds below 10 knots compared to some pretty modern boats like the first 36.7 and some J boats BUT as the wind speed gets higher say 15+ we will get beaten up pretty bad


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## Diva27 (Nov 2, 2007)

I mentioned my C&C 27. I have a Mk1 (1971), the rig is 33 ft. In the later versions C&C stretched it to 37 ft to improve light air performance. The 27 is a wonderful design, and the so-called Mk II which has a stretched stern is close to 28 ft loa. Even the mk 1 is a "big" 27, but still light and nimble.
Two C&C designs of the 1970s, the 26 and 29 (not the mk 2 of the 80s) are known for being capable in light air if a little tippy when the breeze comes up. A friend with a 29 was told by the broker to be prepared to reef the main when the wind got to 12 true.


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## AndrewMac (Sep 11, 2009)

Great responses - thanks. To give a little more background on the boat's intended use: I'd use primarily for daysailing, but have three small kids and would like to take them for short cruises - say 1-3 nights (main reason for the upgrade). This would be primarily in and around penobscot bay in Maine, so lots of islands and would probably camp out at least one night. All of which is to say, I would trade cabin comfort for cockpit comfort (ie. prefer a larger cockpit and can live w/ spartan accomodations). I would also like something that is reasonably fast. I'm upgrading from an Ensign, which I love but find a little sluggish at times. While I would not consider going over 32', I would consider going under 28...say 26? Reason being that I have an interest in a baba 40 with my father - problem with that is: seems to really be his boat and I don't particularly like sailing it unless I'm going for a longer cruise (find cutter rig is a pain, too heavy and cockpit too small). Max budget is 30k - had figured I wouldn't spend more than 20k on the boat and leave 10k cushion for work. 

Thanks again for the responses above.


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## zz4gta (Aug 15, 2007)

SA/D ratio would be where I would start. Check out this calc. it'll help you get started. Sail Calculator Pro v3.53 - 2000+ boats

My merit comes in just under 22 for SA/D. However I can't seem to find out how to calculate it. The numbers I'm getting don't make sense.


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## fud (Aug 13, 2009)

zz4gta,

SA/D = SA / (D/64)^2/3
The displacement needs to be in cubic feet, so:

Merit 25:
SA/D = 285 / (3000 / 64)^2/3 
= 285 / (46.875)^0.6667
= 285 / 13.002
= 21.9


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## sailingdog (Mar 19, 2006)

Of course, if light air performance is really important, it might be a good idea to look at catamarans and trimarans.  Multihulls do much better in light air, as they have far less wetted surface area.


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## bubb2 (Nov 9, 2002)

*What makes a good light air boat?*

A good light air sailor.

Have you ever been out on an a day when there is not even a ripple on the water? You look out over the bow and see a dozen sailboats stalled and the one or two boats that are moving. You think to yourself there must be some sort of breeze over there. Chances are there is not.

Light air sailing is work and patience. Sail trim is essential. Anyone can sail a boat when there is wind to waste. Pick a day when you don't think there is enough wind and go sailing. Get out there. Ease the out-haul on the main. Get some "bag" in the sail. Wait 2 min's to see if the boat responses. Ease the vang wait 2 min's to see if the boat responses. Do not make sail adjustments fast or in combination's. tweak a little and see what happens. Then tweak a little more. The more time you put into it, The more you will know how your boat responses. The BFS sailors will not spend the time to learn light air skills because it is not very exciting, but it is certainly a challenge.

The point I trying to made is light air sailing is a learned skill, the more you practice it the better you will become.


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## JohnRPollard (Mar 26, 2007)

AndrewMac said:


> Great responses - thanks. To give a little more background on the boat's intended use: I'd use primarily for daysailing, but have three small kids and would like to take them for short cruises - say 1-3 nights (main reason for the upgrade). This would be primarily in and around penobscot bay in Maine, so lots of islands and would probably camp out at least one night. All of which is to say, I would trade cabin comfort for cockpit comfort (ie. prefer a larger cockpit and can live w/ spartan accomodations). I would also like something that is reasonably fast. I'm upgrading from an Ensign, which I love but find a little sluggish at times. While I would not consider going over 32', I would consider going under 28...say 26? Reason being that I have an interest in a baba 40 with my father - problem with that is: seems to really be his boat and I don't particularly like sailing it unless I'm going for a longer cruise (find cutter rig is a pain, too heavy and cockpit too small). Max budget is 30k - had figured I wouldn't spend more than 20k on the boat and leave 10k cushion for work.
> 
> Thanks again for the responses above.


Okay, that helps some. J32 would be well out of range.

But soem of the older JBoats might be a possibility. Depending how you much "cruise" you want, you might look at mid-80s J28s (cruisier) and J29s (racier/daysailor).

Here are two examples:

J28

J29

Given that you seem to have access to a fairly serious cruising boat, I would probably focus more on the daysailor/overnighter variety, and as you sat, maybe drop the size range a bit. J27 or maybe even one of their smaller decimeter boats (J80?) would be another possibility.

Hopefully you'll hear other suggestions.


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## zz4gta (Aug 15, 2007)

bubb2 said:


> *What makes a good light air boat?*
> 
> A good light air sailor.
> 
> ...


I do agree with this, but sailing a boat with a rating of 130 or less in 4 knts of breeze is more exciting than one with a rating of 240+ in the same breeze. Keeps you sailing longer, and motoring less.


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## Jeff_H (Feb 26, 2000)

Nothing succeeds like efficient sail area with the operative word being efficient. While overlapping genoas help above really light air conditions, their high drag in the slot make a boat that depends on them a poor choice in the extremely light stuff. 

More ideally you want a boat with an SA/D above 22 with 24 or so being more ideal. 

Light displacement translates to low drag as well. You really want to look for an L/D well below 160 or so. I hear this hoey that heavy boats coast through the light stuff. In 45 years of sailing, I've never seen it....never... ever. 

You want a high ballast to displacement ratio so that you can stand up to the higher SA/D. Without that you have a one trick pony. 

I keep hearing about how great multihulls are in the light stuff. Below 3-5 knots they tend to be very sticky, especially catamarrans. 

I would suggest that you look at boats like a Laser 28, J-30, Farr 1020, Kirby 30, and the like. 

Jeff


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## bubb2 (Nov 9, 2002)

I would like to the 285 Beneteau to Jeff's list. Jeff's point on the large head sail is spot on when it comes to light air. Bigger is not better.


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## AndrewMac (Sep 11, 2009)

Thanks for all the responses. Very helpful. Bubb2, while i know you were being a little tongue in cheek with your initial response, it was actually quite helpful. I find that I frequently get impatient in lighter air and do not let each adjustment take hold as you suggest. And JeffH's comment about the high drag a large genoa creates in the slot is not something I had previously been attuned to - always assumed that, in fact, bigger was better in those conditions. Jeff/Bubb2, I'm assuming that you mean winds that are 5 and below? I guess I'm asking at what point do you think the incremental lift of the genoa becomes accretive (ie greater than the incremental drag)? I'm sure there is no hard and fast answer, but wondering if there are metrics you would use as a general guide...thanks!


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## Brucerobs2 (Feb 5, 2009)

*Sail Plan/Wind Range*

Not to hijack the thread but this is interesting to me. I discovered the same thoughts on larger headsails. Just for fun, I started Wednesday racing my old Hunter 27 this year in our cruising class. I learned a lot about boat speed, or lack therof. For much of the season we either had too much or too little wind so I experimented with sails a bit. I have two genny's that I use, a 155 and a 130 that are on a furler (yes its set up for cruising, and has a grill).

While this might seem elementary to some, in very light air, the 155 is actually harder to fill, especially off the wind (unless its poled out). Despite its larger size, its heavier and has more drag so its seems slower than the 130. At the upper end of the wind spectrum, its size makes it easy to get overpowered, and clearly the 130 is better there too. Obviously that's why those that race seriously have 4-5 staysails.

The 155 is a great sail on my boat, but in a narrower wind range ( maybe 5-15 kts) than its smaller cousin. Above and below, the smaller sail is faster, and easier to handle. Ive always considered my boat fairly good in light air, but racing it taught me a bunch about getting speed out of it in different conditions. Sailing in 10 knots is easy on any boat, Light air sailing takes skill and patience, and the right boat/sail selection. I got slaughtered in both very heavy and very light wind, but did quite well in the middle. Next year, we'll see if I can get faster at the ends of the spectrum.


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## AndrewMac (Sep 11, 2009)

No worries about hijacking the thread! I too am very interested in this turn....thanks for the input. Very curious about tactics, sail selection, trim that are best to manage lift/drag in lighter conditions...


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## RichH (Jul 10, 2000)

Any boat will not perform well in light air if the sail SHAPE isnt appropriate for the aerodynamic flow regimes (of less energy) that are present in light winds. Light winds with less energy are less able to make the turns around the leading edges of sails or you can easily experience a separation stall - where the air flow detaches from the leeward surface of the sail. Separation can also happen because the sail is set-up or shaped with *too much draft* and or the sail has too much cord length (BIG LP) and the energy in the wind is insufficient to keep the flow attached all the way from the luff to the leech. Such separations stalls are usually invisible to the eyeball ... unless you have lightweight tell tales at the luff, midchord and leech of the sail. 



NO, full draft wont perform very well in light winds as when the sail has too much draft of cord, too much 'fullness' at the luff ... the flow on the leeside is more subject 'bursting bubbles' of separation stalls. FULL draft in a sail or 'oversized' sails is a 'killer' in light winds because of ease at which they can 'burst the leeside bubble' and detach the leeside airflow, ..... yet most sailors mistakenly 'draft up' .... usually followed by turning on the engine.

So in addition to all the desirable boat hull characteristic mentioned by other posters ... choose a boat that has the proper, easy and convenient to use 'sail controls' and the proper sails for 'light winds'. You can make a heavyweight 'crab crusher' outperform 'cruising boats' in super light winds simply by sail SHAPE and FULL SET of telltales. 

Also, plain vanilla 'cruising cut sails' - sails cut with 'rounded luff entry shapes' so the sail is 'forgiving' for an inaccurate/inattentive helmsman - easily can have separation stalls due to this shape. A flat luff entry shape, requiring precise helm/steering, such as found in 'racing cut' sails, will be a strategic advantage in light winds as they are much less prone to a separation stall .... but the helmsman will need to be very precise with his steering and the boat will need a FULL set of telltales including a row of 'steering tell tales' (gentry tufts"!

BTW - catamarans sometimes do better in light winds .... not because of the reduced amount of parasitic drag because of less underwater surface, etc. NO not at all !!!! The reason is that because they are SO DAMN UGLY, the earth/ocean is physically rejecting them because of their extreme ugliness hence they sometimes tend to be less IN the water .... its the earth going "Oh puke, its a catamaran, get away from me".


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## blt2ski (May 5, 2005)

I got which a few of us in my club use, a 130 nylon drifter. it is about 130% of my fortraiangle area, higher cut on the clew. catches zephyrs of air very well vs my 155 string Fiberpath sail. 0-6 the drifter works well, 6-8 either, above 8 the 155 is best. Some have a really light 155, but I'm not as positive they work as well as the 110-140 ish nylon sails. Mine is a heavy spin cloth. I use 3/16" sheets too.

Marty


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## AndrewMac (Sep 11, 2009)

Hi all - so after getting people's feedback on my initial question on this thread, I have been busily calculating SA/D ratios (want to thank fud for supplying the equation) on different boats that I am looking at. I then started trying to figure out how to calculate the Wetted Surface Area as a number of people referenced that criterea as another critical determinant. For what it's worth, I came across this link which delves into methods for making the calculation in some detail (actually, a lot of detail - still trying to decipher it ) - thought I'd post it here in case it's useful to anyone else. 
Wetted surface area - approximate formulas - Boat Design Forums


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## Brucerobs2 (Feb 5, 2009)

I have also used this one to compare various boats, which might also help answer your original question. I think its been posted here before but scroll down to use the calculator. More info than you probably care to know. Have fun.

Sail Calculator Pro v3.53 - 2000+ boats


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## bubb2 (Nov 9, 2002)

AndrewMac said:


> Thanks for all the responses. Very helpful. Bubb2, while i know you were being a little tongue in cheek with your initial response, it was actually quite helpful. I find that I frequently get impatient in lighter air and do not let each adjustment take hold as you suggest. And JeffH's comment about the high drag a large genoa creates in the slot is not something I had previously been attuned to - always assumed that, in fact, bigger was better in those conditions. Jeff/Bubb2, I'm assuming that you mean winds that are 5 and below? I guess I'm asking at what point do you think the incremental lift of the genoa becomes accretive (ie greater than the incremental drag)? I'm sure there is no hard and fast answer, but wondering if there are metrics you would use as a general guide...thanks!


IN 5 or less a large genoa will curl. Looking more like a spinnaker than a head sail. You are trying to get as much airflow across the back side of the main as you can with the headsail. A headsail with curled leach, that is not going to happen. If you use a smaller head sail not as much curl will occur and thereby the slot opens up.

I not going to get into boat numbers because a well sailed slow boat will beat a poorly sailed fast boat every day.


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## AndrewMac (Sep 11, 2009)

bubb2 - thanks for the input. Reading the different comments here, it seems that, if one were in 3 knots of wind with a 130 headsail on roller furling and noticed that the leech was curling, it may well make sense to take in some of the head sail in order to reduce drag in the slot and create better airflow across the back of the main. 

Btw - I hope you don't misunderstand my questions to mean that I think a different boat will compensate for the (rather considerable) holes in my sailing skills! I am very much hoping to build those skills in order to have more fun in whatever I boat I find myself in.

Thanks again! 
Andrew

reading some of the comments along


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## bubb2 (Nov 9, 2002)

AndrewMac said:


> bubb2 - thanks for the input. Reading the different comments here, it seems that, if one were in 3 knots of wind with a 130 headsail on roller furling and noticed that the leech was curling, it may well make sense to take in some of the head sail in order to reduce drag in the slot and create better airflow across the back of the main.
> 
> Btw - I hope you don't misunderstand my questions to mean that I think a different boat will compensate for the (rather considerable) holes in my sailing skills! I am very much hoping to build those skills in order to have more fun in whatever I boat I find myself in.
> 
> ...


Andrew, I run a 110% jib on my boat. It does well in light air and does well in heavy air. It will out point a larger sail. For the in between days is what a Asymmetrical is for.

I am not trying to say boat numbers are not important. However, what you might give in light air performance may give you stability when it gets snotty.


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## mccary (Feb 24, 2002)

The answer is simple: The skipper & crew! Some boats seem to spring forward while other identical hulls appear to be anchored. Of course a clean bottom and a modern fin keel and loads of sail will all help.


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## DrB (Mar 29, 2007)

*One more boat that does well in Light Air*

To the OP,

I know that you said that you didn't want to go over 32", but with a bunch of kids and wanting to do the occasional weekender, you will need the room.

Look at a Pearson 10M (33'). On paper it looks like a slow, fat boat. It's 33' long, has a 11' beam, displaces almost 12,500 lbs, skeg rudder, but...... the thing is pretty quick. If you get the tall rig (can find one) your NE-PHRF is around 135 *AND* you can get it for under $25K. The standard rig is 140ish as a PHRF. It's got pretty good creature comforts and is roomy below.

Yes, you can find a quicker boat in this length range, but all aorund it won't have everything the 10M has for the price.

Disclaimer - I own one (Tall Rig) and routinely kick ass on boats much larger than ours. I crew on J105, and while it is faster than the P10M in light air, it is spartan below, very low head room and tight even though it is 2 ft longer and the same beam. I imagine the J32 will be similar.


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## LyleRussell (May 3, 2006)

Getting the crew weight to leeward hasn't been mentioned as a technique on any boat. 

I like a J/30 for your purposes. They have lots of room ,bunks for 5 adults and the rig is easily handled. You can get a good one for less than 25k and have money left over for fresh sails and a DIY bottom job.


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## SiXeVeN (Jul 7, 2007)

> Once you start seeing numbers approaching 17 and above you are getting into a more performance oriented design


My Stiletto has a sail area to displacement (SA/D) of 48.86! If I fly the spinnaker it soars to 112.2!!! 

How's that for a wild ride!

Don't ignore the power of the dark side


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## funcrew (Sep 28, 2015)

Pardon the thread bump; I don't like starting a new thread if I can recycle. I'm looking for an ultralight displacement boat for lake use where the wind is very light most of the time. If money fell from trees, I'd like a vintage model like an Express 27, Capri 30, or Olson 30. Those boats tend to cost 15K to 20K for the best, cleanest examples with lots of recent restoration work and a good sail inventory. I'd like something a bit cheaper, for day sailing only, and for no more than 4 people. Cruising acommodations are not important. I'd be keeping it in a slip, so ease of setup is not a major factor. I recently sailed on a Capri 30 in very light air and was very impressed by it's speed. We had a very experienced skipper though, which I'm sure helped. Any ideas of possible vintage ULDB designs of 24 to 28 feet or so? Perhaps other boats not officially ULDB but that still move well in light air? Multihulls are not very practical in my location due to a lack of wide slips where I would be keeping it. It would be nice if the boat was good for single handing, but I would have 2 plus guys most of the time. Any thoughts or input would be appreciated.


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## rckfd (Dec 3, 2015)

Okay first most important is skipper hands down to get the boat to go.

I just briefly read this noticed j/30 and j/32 mentioned and seeing I owned a 30 for like 20 years and have had a 32 for 15 I'll give you all my thoughts.
J/30 you had 3 head sails the biggest a 168% you could sail at around 3 knots into the wind with a 4knot breeze I know nothing about drag and was never passed with someone with a 110%.
The 32 I haven't found the right sail combo yet the first head sail was to small went to a bigger sail and wasn't happy with either light or big air.
I've been researching sails all winter because I need a whole new set. Right now what I think I'm going to do is get a code 0 figure out how high a wind I can sail it and then figure out how big a jib I can get away with.
Down wind I'm thinking code 0 and a a3. 
We'll see....


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## Stumble (Feb 2, 2012)

Frankly an Olson 30 is almost impossible to beat for its size in light air. But they are no where near $20k. I sold mine in very good condition for $10, there is one in New Orleans right now asking $12k, and it has some really fun go fast bits (asymmetric rigged).


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## Zarathu (May 26, 2014)

You really need to be much much more specific as to how much you will pay, how old you will accept, how many people aboard, what you want to use it for, how much experience you have, how much experience your crew has, etc. Without lots more data, everyone will give you their own favorite boat. The problem is that few people ever own more than 2 boats in their life, and thus they only have experience with one or two boats.

And so, sailors are like electricians. They leave the innovation to the America's Cup since innovation can be expensive, dangerous, or both. I once asked in a small boat forum about using screw clamps to tighten the roller furling in a blow. I put one above the center and one below and put tubing on the metal of the clamp. I was told online by a revered member of my boat community that the clamps would rip the sail apart. In fact, they worked amazingly well, and the jib had no issue on a steady 50 mph wind and 65 mph gusts. Other people had their roller furling jibs suffer severe damage.

So while everyone in forums is conscientious, they only know about their boat, and your boat and you situation is often very very different. I can tell numerous stories like this.


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## Scotty C-M (Aug 14, 2013)

Funcrew,
Lots of good boats have been mentioned. Another classic is a Santa Cruz 27.


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