Sail Area Specifications

[slode]

I've always been skeptical of Hutchins' specified sail area for the Eclipse of 200 sq. ft.  It seems high.  I just did the math and it proves my skepticism is justified.

From multiple sources I've found the same sail plan dimensions I= 19.5 J = 7.25 P = 19.67 E = 8.83

The main sail is simple PE/2, and I've seen that rating for the Eclipse at 86.84 sq. ft. which is 19.67x8.83/2

If you use these rig dimensions to figure out the maximum luff of the headsail = sqrt (I squared + J squared) = 20.8'
and the luff perpendicular using the standard 115% genoa that comes with the boat LP = 1.15 x J = 8.34'
the headsail is 8.34x20.8/2=86.73 sq. ft.  86.73+86.84 = 173.57  Quite a bit lower than the 200 figure. 
You'd have to put a 150% genoa on this boat to get to 200 sq. ft. 

Compare this to the CP23 MK3 with a specified 250 sq. ft. sail area.  I= 26 J = 9.42 P = 22.75 E = 8.5  Using the same math it would only take a 120% genoa to get to 250 sq. ft.

Or a CP27 with a specified 380 sq. ft. sail area.  I= 31.33 J = 11 P = 25.67 E = 12  Again it would only take just over a 120% genoa to get to the reported total sail area.

I've tried this with many other boats from other manufactures too.  And none of them take over a 125% genoa to get to their reported sail area, and many are rated with a 100% headsail.  What gives? 

[Vectordirector]

Sails are not flat but are cut in flat pieces and then sewn or laminated into an air-foil shape ( they are not perfect flat triangles).   Gotta think in 3 dimensions. 

Vectordirector

[philb Junkie19]

While planning my junk sail for my 1983 cp19 I needed to know the sail area of my existing Bermuda sails. The given cp sail dimensions and geometry seemed to show the sail areas to be less than listed so I measured them. Racing associations have a prescribed method for measuring sail area. For the main it involves taking a measure from luff to leach at four designated points. This is to allow for the curve of the roach. Camber isn't calculared. I measured differently. On the main I stretched out my sails on a new (still uncluttered) large attic plywood floor. I was able to use nails to hold the corners.  I measured the triangle and then the roach, separately. For the jib I divided it into one large right triangle and a smaller one by the foot.  I was very surprised to find the square footage of each well below what is listed. I just looked back through my design worksheets and didn't find the measurements. While maybe not quite as accurate as the associations' method it had to be very close. Calculating by dimensions showed similar results.

Looking at just the main, for the sail area to be the listed 98 ft2 the roach would have to be 30% of the sail.  I think it is around 10% which is pretty standard and would give it area of 83 ft2.  A15% roach would still only calculate to 86 feet.

When I was considering the converting my old cp16 I found similar results.

[Vectordirector]

Still not allowing for the body or depth of the sail.  Look at your main from the stern or the bow when the sail is full.  It takes a lot more fabric than the calculated triangle including the roach.  The sailmakers and naval architects use computer simulation to derive the measurements for boats and sails now.  It involves some serious math that is way beyond anything I understand. 

The measurements used for ages for sail square footage (and a lot of other things) were educated guesses at best.  Until computers were programmed to do the calculations on an air foil the sf numbers were not entirely accurate, even using a slide rule.  IPJE does not include a measurement of the curve of the foil which could easily account for the 15% differences seen in the measurements.

I'm not an expert but I can see the difference just looking at the sails when they are full.  YMMV.

Fair Winds,

Vectordirector

[slode]

I realize the numbers I used aren't the actual area of the actual sails and don't account for roach, or camber, or the actual luff of the headsail which is usually shorter than the forestay.  I was trying to compare boats and the IJPE numbers are the only reliable dimensions to use for that.  And they are what is used to compare performance aspects like sail area/displacement ratio.    I guess my question is more to the point why the Eclipse is so grossly over rated when compared to other boats even from the same manufacture.  At most it should have a reported sail area of about 175.  That would have a big impact on the reported numbers.  Not like speed and performance are on the top of the list for anyone looking at this boat, but it is a consideration that warrants being more accurate that this.

[slode]

Here's a good example of what I mean.  https://sailboatdata.com/sailboat/com-pac-eclipse  If you look at the SA/Disp ratio it's reported at 18.96, that's using the reported sail area.  If you look down further at the calculated SA/Disp ratio it's 14.94, that's using the IJPE numbers.  The reported number puts the Eclipse as a performance cruiser.  The calculated figure puts it at the pretty sluggish heavy displacement boat it is.

Now look at a comparable boat in the Compac lineup https://sailboatdata.com/sailboat/com-pac-19  You can see the discrepancy between the reported number and calculated number is much less.  And the 19 and Eclipse are about an even match using the calculated figures, which one would expect.

For another comparison of a similar size boat https://sailboatdata.com/sailboat/precision-21 Now I'm sure All would agree a P21 would completely smoke an Eclipse, but looking at the reported numbers the eclipse is at just a slight disadvantage.

[Vectordirector]

Com-Pac has a reputation of under canvassed boats.  It goes all the way back to the 16.  Perhaps it is a bit of marketing fluff to make the boat appear faster than it really is to compete with the P-21 which has, supposedly, amazingly, 200 sq ft of sail and seems to weigh about 300 lbs less than the Eclipse.  Strange that........

Here is the other only real competition to the Eclipse in my view:  http://www.catalinayachts.com/sport-series/22-sport/   New Catalina 22 CB, 2400 lbs, 205 sq. ft. of sail.  SA/Disp of 19.75.  LWL 19.3 ft, Hull speed 5.9 kts.  Someone is lying as this boat will smoke an Eclipse for sure.   

I hope AL Santini chimes in as he has quite a bit of time on the P-21.  I think they are closer than you imagine as far as max speed with similar LWL of ~18 ft.  The P-21 should do better in light air if it really has 200 sq. ft. of sail area.  As should the Catalina 22 sport.  Does it really play out that way?  Which boat is easier to get to hull speed?  Which boat is easier to maintain speed in steep chop like I get here in Charlotte Harbor?  It may come down to the sailor proficiency and time in each boat. 

The manufacturers all lie about boat displacement so I take SA/Disp. numbers with a bit of scepticism.  Useful to somewhat compare similar boats as tender or stiff.  I would agree that ultimate performance matters little to someone looking at buying an Eclipse.  Certainly was down the list after easy to sail, factory support, ability to trailer with my Wrangler, to name a few, when I bought mine. 

Just some thoughts on a wind free day in Punta Gorda. 

Vectordirector

[philb Junkie19]

I needed to know my 19's square footage to design my junk sail. Often junk sails are made a little larger than the original as reefing is quick and easy. The more recent western junk rig sails are most often built with camber. Maximum camber in my sail, in most panels, is about 7% of the measurement in a line from luff to leach and is 35% aft of the luff. It is flatter in the upper 3 panels to allow for some twist and to be flatter when in conditions call for the sail to be reefed down to just 2 or 3 of the seven panels. Adding camber required planning for the additional sail fabric. That additional fabric used to build camber is not included in the square footage by those junk sail designers I have communicated wiith. From the descriptions I read on measuring footage by racing associations, sails are measured at different points straight from luff to leach.

Of course when out sailing the difference between stated and actual square footage doesn't change anything. When I first found that difference I was a little bit irritated that compac would exaggerate but that's lost among the other small stuff and whatever the footage it didn't make my great little 16 or 19 go any faster or slower or me to enjoy them any less. Don't worry be happy.

[slode]

My main reason for looking into this in the first place is I plan on racing at Leech Lake next year.  It's a casual regatta but with any racing of course things get competitive.  There is a "race committee" but they aren't out measuring sail area, or anything else for that matter.  It's pretty much pull PHRF from published numbers, for which the Eclipse has none anywhere I've found.  When comparing against other boats I noticed the reported sail area of the CP19-2 and knew the Eclipse couldn't be that far over being a fractional rig that's just a foot longer with about the same mast height.

I wouldn't trade my Eclipse for any other boat out there, it does what we want her to do better than any other boat I've found.  And the 10th of a knot here or there when cruising I could care less about.  I just want to be fair for me and the other competitors if we take her out on the course. 

And I do believe the serious exaggeration by Compac is crossing the line a bit to false advertising. 

http://www.sailboatrichlands.com/ has a great database on performance specs of a bunch of boats.

[mattman]

This is the place to start. http://www.phrfne.org/page/

I have done a lot of phrf racing, take the number they give you and go racing. It will be a reasonably fair number which will allow you to win races.  Just guessing I would think maybe about possibly 270ish  to  275ish, though I think 270 may be a bit high. Remember you are talking seconds per mile time differential. If you believe your number is unfair then make sure that number is reflected in your race plan, or choose to not race with that group. When you do race, your skill at setting up the boat,  smooth execution of boat maneuvers, starting technique, race plan,  and overall seamanship is everything.  I have seen inexperienced or poor sailors on a low phrf boat and never sail it to it's potential failing to place in a race. I have seen experienced sailors take a dog onto the course and compete handily. Fairness comes from good sportsmanship of your competitors, if you are consistently fast accept a few points shaved off , it will make you a better sailor. If you are always in the back of the pack make sure your competitors go sailing with you. If they can't get your boat moving better, they will likely assign you a few points to help make the boat competitive or they will give you some hints to bring your skippership up to the rating. Remember they don't get better by winning all the time!  Also you have to PRACTICE! This means hours and hours of boat handling, timed runs, vmg analysis, etc...trust me the guys winning are doing this and if you want to win you will too. Best of luck and have fun out there!