CS20 sails - vertical clearance?

[wkisting]

Hi all,

On our CS20, each sail hangs low enough that we have to duck very low when tacking and we find it hard to see boat traffic on the lee side. In pictures, it is obvious that other CS20 owners have much more head clerance. To fix this, I will likely need to add an extension to the top of each mast. I discussed this briefly with Graham, but he's in Mystic right now so I don't want to bother him with more questions.

Can any CS20 owner who has sails with the roach and battens tell me...

How much vertical clearance (above the deck) do you have at the main sail tack?

How much vertical clearance (above the thwart/seat tops) do you have at the mizzen sail tack?

How long/tall are your masts?

Here's the specs on our current setup:

MAIN mast is 21'3" tall. Main sail luff measures 17'11" (relaxed, not tensioned), so I end up with only about 7-9" clearance above the deck at the main sail tack.

MIZZEN mast is 20'1" tall. Mizzen sail luff is 16'3" (relaxed, not tensioned), so I end up with only about 16" clearance above the thwart at the mizzen sail tack--although I can add a small piece of sail track and get an additional 4" of height without extending the mast (I ran out of track and never bought more). That will still only be 20" clearance though.

What I find strange is that my masts are already 8" longer than originally spec'd in the plan sheet Graham sent me in 2007, but the luffs of my sails are only about 5" longer than spec'd in those same plans. Maybe my plan sheet (dated 11-20-07) never had the appropriate vertical clearance factored in? It shows approximately 2'8" below each sail tack, which I think is nearly how much I have now.

[Hirilonde]

I have no significant experience with a Core Sound but the lower the sails the more efficient and obviously higher is more comfortable. This is but another of the many compromises to be made. The boom on a Spindrift is really low, but it sails so well I doubt I will lengthen my mast.

[Ray Frechette Jr]

As drawn the CS series typically has more hoist on the mast than luff.

In light airs you hosit the sail to the masthead and as such your sprit angle is lessened.

by hosting higher you have clearer air and witha shallower sprit angle you will have less vanging force on the sail allowing the leach to twist off some. Twisty leaches are typically good in light air as the vector of wind from water to masthead changes appreciably at low wind speeds given the ffrictional losses of air with water slowing the wind speed at lower elevetions.

As wind speed increases first reef is to simply drop sail to bottom of track. this also steepens sprit angle which in turn increases vanging effect of the snotter giving you a flatter leach which is prefered in higher windspeed in order to better match apparent wind direction form water to masthead..

[wkisting]

Well, my sails were cut slightly oversized, so the spec sheet isn't quite right for them. I also made my masts slightly taller than spec originally, but apparently not enough. I'm hoping that someone can measure and tell me the actual vertical clearance for their sails on a CS20, which will help me determine just how low mine are. Graham confirmed that mine are definitely low and could be raised, and we discussed ways to lengthen the masts, but he never quite said what the "appropriate" clearance ought to be. I didn't want to pester him with questions while he was getting ready for Mystic.

I know for sure the sails on Dawn Patrol are much higher than mine because they clear the cabin, whereas the foot of my main sail will not even quite clear a barely-head-height dodger. I've also noticed in pictures of other CS20s and CS17s that the sails appear to have almost twice as much clearance as mine do.

[Peter HK]

Hi Wes

I can't reply with exact figures as I am not near the boat and my copy of the plans is still in a box after moving house. I made my masts about a foot longer than the plans to allow for halyard turning blocks, room under the sails etc. They are a little too long and I don't hoist the sails all the way...perhaps 6 inches from the top. You can get some idea of the clearance under the sails from the accompanying photos. The foot of the mizzen is about at eye height so it is easy to see under it. The main has about 15 inches clearance from the foredeck and my crew has never complained of difficulty getting under it while tacking.

PS Forgot to mention this is a CS17 not a 20.

[wkisting]

Thanks Peter. Yours is one of the boats I saw that made me realize how low my sails are. Your comment about the luff being at or near eye height really helps.

FYI, here's a picture from the very first time we launched our boat after completing the build. I later figured out how to alter the the uphaul slightly to gain another 2" of height out of each sail. Nonetheless, my sails still hang almost as low as shown here... By the way, that's my tiny, foot-long Chihuahua standing up under the foot of the main at the front of the cockpit. There's only about 9-11" of clearance above the leading edge of the cockpit rim.

[Howard]

Wes:

Do a YouTube search for "core sound". Several videos, including one of a B&B messabout that has photos of several boats. Yours is different. Wonder why. Not enough mast or too much sail?

If too much sail, that would raise another issue and that would be one of balance. Relation of CE of the sails and CB of the boat. I would think too much sail might shift CE too far aft, affecting pointing ability, amount of leeway, etc.

[wkisting]

Well, when I finished the boat in 2007 and bought a rigging kit from Graham, he gave me a discount on these sails. To the best of my memory, he said they were accidentally cut "slightly oversized" for another client. (I think he said the luff was cut 10" longer than usual.) He said they would work fine if I made the masts a little taller than spec'd, and sent me an updated sheet for the most recent (standard) mast dimensions at that time.

I took all the measurements for my hardware off the bottom of the mast on the spec sheet thinking that would preserve the appropriate clearance, then I cut off any extra I had at the tops once the sail was fully raised (only the mizzen got cut down; the main mast was as large as I could make with the materials Graham sent). This left my masts about 8-9" taller than spec'd. But I didn't realize that other builders had already found the standard masts too short even for the standard sails. Ironically, if I had standard sails, my mast heights would probably be perfect. I could order a new set of sails, but mine have plenty of life left so I'll just add a top section to each mast to make up the difference. Graham says there should be almost no stress on the masts at the very top anyway. I certainly won't add more than 12", possibly less.

[Howard]

That being the case, sounds like you need more mast. I'd allow enough extra to be able to rig it as Ray suggests. With the higher hoist and additional sail area, you could wind up with a light air bomb that blows by everything in sight.

[W. Micawber]

I was thinking about this yesterday. After 12 hours on the boat and a crick in my next from peering under the lee side sails, I wonder why the foot of the sail was not cut on more of a diagonal toward the clew and the spritboom rigged horizontally as on some sharpie sails I have seen.

[hokeyhydro]

Wes - ever thought about having the sails trimmed down?

[Dale Niemann]

Wes,

Can't help you with a 20 but here is 'Lively' my CS17. I am 5'8" and the mizzen sail goes completely over my head on tacks. I like this arrangement. I have a couple of times done as Ray suggested just lower both sails when contemplating reefing and it does help.

[Terry Dunn]

I made my masts 22'. Standard sails. Sleeved at first (2003). Converted to sail tracks later (2007). Looks to me you could add 18". Perhaps 2' to the mizzen. Get some serious clearance.

[Howard]

I was thinking about this yesterday. After 12 hours on the boat and a crick in my next from peering under the lee side sails, I wonder why the foot of the sail was not cut on more of a diagonal toward the clew and the spritboom rigged horizontally as on some sharpie sails I have seen.

As I understand it, the Leg of Mutton type sprit sails generally had a lower tack point, and the clew was kept higher so when the boat was heeled over, the sail didn't trip on the water. The horizontal foot doesn't allow the air to leak out the bottom, so in addition to having more sail area down lower, it is more powerful. Hard core racers like to have their jibs and gennys sweeping the deck, whereas cruisers sometimes opt for a higher tack, so they can see under the sail and what's beyond.

If being able to see past the sail is a continuous problem, you might consider having a clear panel installed.

[wkisting]

Thanks for all the input.

I did think about having my sails trimmed down, but they're great in light air. Also if I have them trimmed down, it would probably require me to move the reef points too, or else the first reef would only take in a very small amount of sail. I thought about windows, too, but I'd lose the window as soon as I reef, and I've had a lot of other sailors tell me that window panels don't wear as long/well as the rest of the sail due to stretching or yellowing.

I think I'll probably add 12" - 14" to each mast, which would give me considerably more clearance and visibility, and make it MUCH easier to fit the boat with a comfortable dodger. I'm sheepish about adding more because I don't really understand how much it may affect the stability of the boat.

For the extensions, I'll likely use 2" O.D. 6061-T6 aluminum (same diameter as the top sections of each mast). I'll make a 6" long aluminum spline milled out of solid bar to match the I.D. of the tubing snugly (then bored through the center to leave 1/8" wall thickness on the spline, which should be quite strong and light). It will fit 3" into the extension and 3" into the top of the existing mast. The mizzen extension will bolt on permanently, but the main extension will have to be removable or I won't be able to close my garage door. (Presently, my main mast clears the garage door by only 1/2"!). I need to keep the added weight aloft to a bare minimum, since the main mast is already close to the limit of what I can comfortably step alone without straining myself. I think the only significant force on the extensions will be straight down (in parallel with the mast), when the luff of the sail is tensioned.

Graham recommended I use wood, but since the main extension needs to be removable, I'm worried wood may swell and get stuck. Aluminum won't do that and may come out slightly lighter. Thank goodness I have a dad who is a steel fabricator with a fully equipped welding/metal shop...

[hokeyhydro]

If the tubing is sized right it should telescope to the next size down. Get a short piece and save all the fancy machine work.

Actually I was thinking a top trim on the sail. Less area lost, and less sewing. Insert a nice wide headboard and roll the roach in to fit - stitch - stitch - whammer a new grommet in and you're done.

[wkisting]

Actually I was thinking a top trim on the sail. Less area lost, and less sewing. Insert a nice wide headboard and roll the roach in to fit - stitch - stitch - whammer a new grommet in and you're done.

Hmmm... wouldn't that affect the shape, tension, and twist of the roach? I'm a little concerned about fiddling with the sails myself, and I don't think it would be cheap to have a sailmaker adjust them (?).

The next size down on tubing would need the epoxy bushing and a wedge to fair the sailtrack again. I don't know that I would save any weight, but I was especially worried about having the sail track on the removable extension (on the wedged part) line up perfectly with the sail track on the rest of the mast. If it was even slightly off, I think the sail would get stuck as the slides reach the edge of the extension, which would be horribly frustrating. If both extensions were going to be permanent, I could just run the sail track right across the seam and it would create a smooth transition, but that's not really an option on my main mast.

[Mike Vacanti]

Would it perhaps be easier to add the extension to the base of the mast? The additional weight would be much less of a concern and it could be made removable without any accomodation for the sail track.

[wkisting]

Would it perhaps be easier to add the extension to the base of the mast?

I had that idea, too, but Graham talked me out of it. As he put it, "diameter is everything" when it comes to strength, and the most stressed portion of the mast is the part right at the bottom. In order to keep my mast steps as-is, I would therefore need to use a smaller diameter spline to join on another 3" diameter extension section. But that spline, being smaller diameter, would be weaker as a result. I suppose I could've gone to a much heavier material, such as steel tubing for the spline, but then you're talking serious added weight also. In aluminum or wood, though, it did not seem like a good idea. But yes, if Graham had thought it was a good idea, that would've been the easiest fix indeed, with no need for more sail track/hardware/etc.

[Mike Vacanti]

The spline would only be weaker if you made it from a smaller diameter aluminum tube. If you made it of solid Douglas Fir and extended the plug a foot or so up the existing mast it seems like that would be stronger than the existing mast. But if Graham has considered that and dismissed it I would take his word for it over my specualtion.