Possible Mod Question

dlochner · Nov 19, 2023

Lowering the boom will not improve boat speed unless you also increase the sail area. Increasing the sail area will have other effects on the boat's performance, including increasing heeling and needing to reef earlier.

The tried and true speed improvements are:

New sails
Clean and fair bottom
Reduce unnecessary weight
Folding or feathering prop if an inboard
Proper rig tuning
Proper sail trim

Light air sailing requires a deft hand at the helm. It is a much more difficult condition to sail in than heavy air as any little movement of the tiller or crew weight will affect the boat's speed, often not for the better. There is no room for error in light air if performance is the goal. This is why we have auxiliary engines.

dlochner · Nov 19, 2023

JohnK Austin TX said:
If this mod could add about 2 kts speed gain, in 5-8 kts tws on the lake, I am sold and will buy one

What kind of speed are you getting now? What kind of speed are you expecting? Where did you get the polars?

If you are racing OD, this will not be an acceptable modification. If you are racing PHRF or another handicap, your handicap will be adjusted for the increased sail area. In either case any potential speed gains will be mitigated by changes in the handicap or being disallowed.

Stu Jackson · Nov 19, 2023

JohnK Austin TX said:
If you think, it may work, can you “guesstimate” what kind of speed gain this mod may bring?

From a purely mathematical point of view, as asked it is impossible to answer because while you said how much you'd add you didn't say what the original size is.

That assumes that there is any relationship between mainsail area added and potential additional boat speed.
From a sailing pov I don't know if there is any way to determine how much additional boat speed "could" be added by xyz % to a mainsail. That said, it appears completely unrealistic to add the amount of boat speed you desire to a boat where its theoretical max hull speed is say around 5. Adding 25% or more speed (2/5 = 40%!!!) by adding way less than that area at the bottom of the sail just "does not compute" or another way to say it does not compare favorably. Additionally, the main is as you said just one of two sails. I forget whether or not the C275 is a masthead rigged sloop. If so, you'd probably get more bang for your sail buck by dealing with the jib/genoa.
I sailed my C22 and C25 on San Francisco Bay for 15 years, so rarely had too little wind.

But during the winter there often were drifting days. Any boat with the short waterlines of a C25 or C275 will be slow in light air. I don't have any idea of what your point(s) of comparison or desire actually could be. Good luck in that regard. [That's a polite way to say "Compared to what?!?"

] You had already mentioned the polars as a starting point. Had you been reading them properly? IIRC, there are groups of them based on windspeed. What is your source for them?
Dave's points are all extremely valid and on point.
Overall, my recommendation is: Don't do it. Not worth the $$ or the unknown unforeseen consequences or any potential enhancements.

dlochner · Nov 19, 2023

It is your money and your boat, however, I think you will be disappointed in how little the speed will improve. Also, with a wing keel you will not get the same upwind speed as you can get with a fin keel.

Adding 2 feet of sail will give you about 20 ft2 more sail area, a tad more than a 10% increase in sail area. Assuming a direct correlation between sail area increase and boats speed, then you could expect an increase of about .3-.4 knots, a far cry from the increase you are looking for. I think a 10% increase would be pretty optimistic. In light air the fastest boats will have the tallest masts and the longest waterlines, because surface drag on the wind reduces wind speed the closer you are to the ground. Increasing sail area aloft is the key, the air is stronger and more consistent. This can be done by using a taller mast or increasing the roach of the sail. That was the promise of the B&R rig Hunter used for a while, get rid of the back stay and use a big roach main. The current trend towards flat top sails is also an attempt to reap the benefit of stronger and more consistent winds. Your plan places the increase sail area close to the water and in air that is disturbed by the crew and the boat itself as well as the surface drag.

As for the PHRF rating that is more reflective of your boat, good luck with that. PHRF ratings are not at all scientific or data based and politics plays an outsized role in assigning ratings to one-off boats.

Well made and well designed new sails will be the best bet you have for improving speed. But hey, its your boat and money, I wouldn't go there.

Stu Jackson · Nov 19, 2023

JohnK Austin TX said:
except it is in deed a low-powered, slow boat....

Something doesn't sound right, even with a wing keel.
The brochure for the C275 (https://www.catalinayachts.com/sport-series/275-sport/) says this:
"...hull is coupled with a powerful rig with large main and selftacking jib, which makes the 275 not only fast, but also super-easy to sail. "
Catalina rarely gets it wrong.
A one day sail on OPB often doesn't exhibit the experience you would get after owning one and getting the most out of it.

PMK · Nov 19, 2023

Hi John,
I have been sailing and racing my C275 for 7 years and here are my thoughts:
1. The boat is slow upwind primarily because of the small jib (106%) and wide transom (slow in tacks).
2. The main is plenty big, no need to lower the boom. I had my current sail made with a large head and roach which adds quite a bit of power. Disadvantage is that in light wind, it will get hung up on the backstay, even with the flicker. I spray the leech with sailkote to facilitate tacking. You may want to opt for a more robust flicker and/or a lighter (rope instead of wire) backstay.
3. If you have not done so already, get a folding prop. This makes a notable difference at low boat speeds.
4. Obtain polars and ORC rating from US sailing. These polars are accurate and allow you to input sail/boat changes to see effects on boat performance.
5. If handicap racing, you will be slow and at a disadvantage at the start/upwind leg because of slow speed. Everyone will pass you. Seek clear air and expect to catch up and pass on the downwind legs. The C275 is fast off the wind.
6. The stock Doyle spin is a good reaching sail. Get another spin for deeper angles.
7. If you feel you must have greater upwind speed, add a pair of aft winches and a 155% genoa. You will not be able to sail close to the wind because of the spreaders, but the increased speed may be worth the gain and the investment.

Paul

dlochner · Nov 19, 2023

JohnK Austin TX said:
if the boat was what the manufacturer advertised.

And when has that ever happened?

What the numbers say and what the boat actually does can be worlds apart. A velocity prediction program is based on the boat's measurements, not the actual shape. For example, the oft quoted theoretical hull speed formula was initially developed several centuries ago and it was accurate for the blunt nosed sailing vessels of its time. Recently, there has been more research on hull speeds and the effect of hull shape on the actual hull speed. If I recall the term correctly the new factor is wave splitting ability or water splitting ability. Essentially it is the ease at which the water parts as the hull moves through it. I doubt the the VPPs actually take this into account. If the VPP model is tuned towards high performance boats, like the J27, then the prediction algorithm will not apply to boats that have different hull shapes and characteristics.

Catalina has long tried to break into the racing market without much success. The Capri 22 was probably one of their better efforts, however others have simply not done well. From your description it sounds like the 275 wasn't very successful either.

If you are interested in a 27 foot boat that sails well and is comfortable off the race course, take a look at the Precision 27 or 28. These are Jim Taylor designs. Taylor knew how to design a fast comfortable boat. My Jim Taylor designed boat does really well in light airs, going up wind with a wing keel, new triradial 135, and new triradial main, I can approach wind speed, reaching 5 to 6 knots in 6-8 knots of breeze.

Precision: Small, Fast, and Fun by Jim Taylor Yacht Designs

Codybear · Nov 20, 2023

Hi John,

I think the biggest problem you are up against is the weight of the C275. I have the heavier wing keel, which still tracks reasonably well upwind, and it weighs a little over 6k lbs when I weighed it at a truck stop (I subtracted the weight of the empty trailer). Also, the fat stern is sticky in the light winds. I found I'm most competitive in 15+ kts. Fortunately, we typically have more wind in Chicago than you have in Austin. The furling asym, while not good for deep downwind, is a lot easier and faster to deploy and roll up, so you will benefit there. If your races are not all up/down wind, I would consider a code 0 sail. Possibly a cableless, which will have less tension on the sprint.

The PHRF you get assigned will play a big part. The word "Sport" in the name has really been a disservice causing clubs to give lower numbers. But I have seen 255 from a club in Connecticut, so you may want to check with your club and get a feel of what they would initially assign. The Capri 22 is a faster boat, especially in light winds. But the C275 is a more enjoyable boat to be on and is great for daysailing and swimming.

A 2 kt increase is a lot to ask for with the C275. A folding prop is a must, which will ding your PHRF. You may want to research a C275 in Chicago who has upgraded his sails to North 3di sails and is racing distance races, including the 600 mile Super Mac. I don't know who it is, but North Sails in Chicago mentioned him when I was inquiring about 3di sails for a new boat I expect to be upgrading to. The 33' boat I'm looking at will give me a 2 kt increase because of the longer LWL, reduced weight (5.3k lbs) and about 60% more sail than the C275 (both configured with self-tacking jibs). This upgrade means my C275 will be coming on the market soon.