How fast can a Sun Cat sail

[Peter Dubé]

I am new to my Sun Cat.  Getting used to her and her to me ...

Just wondering how fast you can sail them.  I got mine going pretty good the other day.  Set a personal speed record. 

[Catawampus]

Did you push her over a cliff?  Hull speed is 5.3 knots which converts to 6.1 mph.  I've seen 5.5 knots in 15 knot winds (or 6.3 mph). Didn't think I would ever see over 6 knots. (6.2 knots is 7.1 mph)
Of course, I sail on an inland lake. A displacement boat can easily exceed her hull speed when she is surfing. A condition that I'm not likely to see.

[Peter Dubé]

Wind forecast was calling for 10 to 15, I suspect it was blowing harder. I was in the ICW, no waves, slight chop. Broad reaching, full sail. I also did not expect to see speeds like this on a small cat boat.

I was fun!. I got home quickly!

Peter

[nicktulloh]

Tide ... current?

[Craig]

Since it is a GPS speed reading the SOG could easily be 7.1 if the current was favorable. Fun isn't it? By the way it is a myth that catboats are "slow". They may be under-canvassed in really light air but when the wind pipes up on a reach or a run they can be quite fast. The fishing boats they are derived from could not be garbage scows. The fishermen needed to get their catch to market ASAP. The old timers also often flew a jib under really light conditions. If you look at current modern hulls you will see that that they share some  characteristics with catboat hulls........Lots of beam, flatish hull form carried well aft and plumb bows.

[hoddinr]

That's funny!  I also got my SunCat up to 7.1 MPH this past weekend!

Most of the time it was 5.7 - 6.1 MPH but after passing the opening of Boca Grande Pass I began to get a bit of a shove from the current. 

7.1 MPH is equal to 6.2 knots.  Faster than I thought a SunCat could go.  Sailing off the wind (broad reach) in 18 MPH of wind.

Ron Hoddinott

[Tom Ray]

I saw over 6 knots several times. I never saw 7 knots or anything very close to it.

The hull speed limit is a "soft" limit.

My aluminum skiff goes from displacement mode to planing mode and back all the time. There's this mode in between: getting on plane. It requires a lot of power.

You have to climb up the bow wave, reach the summit, and get over it. Displacement boats can do the first part, just not the last two.

If you are going "hull speed" and you add power, you will begin to climb the bow wave. It's a steep climb and gets steeper as you go. Adding a bit of power will get you a bit of the way up the slope. Most any sailboat can do this. You just have to have more power than is needed to achieve hull speed. Add enough sail area and/or enough wind to any sailboat and you'll get more power than is needed to achieve hull speed.

[Peter Dubé]

Tides/current. The Indian River Lagoon is pretty stagnant with little tidal change. However, I did check the tide table for the day I set my speed record. I WAS sailing with the tide. So that DID increase my speed. I'll try to find a current table.

Peter

[Tom Ray]

Current tables show averages but you were probably seldom in the exact average current for long.

A better way to check is to go the other way and note the speed difference on a day when the wind is perpendicular to that channel.

[nicktulloh]

I'm no expert, and I don't want to be argumentative or picayune, but I don't believe that a true displacement hull can ever exceed hull speed. When I got my marine degree 40 years ago, things were a lot simpler - displacement hulls, semi-displacement hulss and planing hulls. Now there's variants and foils and who knows what else.

The Suncat and Horizoncat type hulls are, I believe, semi-displacement and so can be forced over hull speed. The others, like my old CP19/2, are displacement hulls and you could hang a 454 off the transom and it still wouldn't go above 1.34 x the sqrt of the LWL.

I saw over 6 knots several times. I never saw 7 knots or anything very close to it.

The hull speed limit is a "soft" limit.

My aluminum skiff goes from displacement mode to planing mode and back all the time. There's this mode in between: getting on plane. It requires a lot of power.

You have to climb up the bow wave, reach the summit, and get over it. Displacement boats can do the first part, just not the last two.

If you are going "hull speed" and you add power, you will begin to climb the bow wave. It's a steep climb and gets steeper as you go. Adding a bit of power will get you a bit of the way up the slope. Most any sailboat can do this. You just have to have more power than is needed to achieve hull speed. Add enough sail area and/or enough wind to any sailboat and you'll get more power than is needed to achieve hull speed.

[Craig]

Exactly Nick! The theoretical hull speed of a semi-displacement hull is, as Tom said, "soft" and is thus somewhat indeterminate vis a vis existing conditions.

[nicktulloh]

I know this is a little old but I dragged out an old textbook and stand corrected. At massive amounts of additional power, it is possible for a displacement hull to exceed the theoretical maximum hull speed. Massive amounts.

I think that full displacement sailboats exceeding hull speed are actually not technically full displacement and are doing so with hull design tricks that make them semi-displacement.

[Salty19]

A few years ago I recorded about 7.5knots on our CP19 on a lake with only a small amount of current from the underlying river. Handheld GPS.

I didn't believe the figure and decided what had happened.    I moved the GPS unit from aft near the gas tank to forward near the cabin. The additional speed was simply the quick forward movement of the GPS itself combined with the forward speed of the boat (at that point less than 5knots actual boat speed).

I've sailed (raced) against several Suncats in the infamous CLR race in our CP19 and found them quicker than expected.   I beat the fastest Suncat upwind and down (PHRF corrected start), but I was flying a huge drifter most of the race (until the marker was moved mid-race during which time I dropped it and unfurled a 140% genoa),  use a foiled rudder and a loose footed, fully battened main which all increase performance.  We both are good sailors.   If I had stuck with the standard 110% jib and stock rudder,  I would predict the Suncat would either beat me or be VERY close.  Upwind I was much quicker, but downwind the Suncat really flew. 

I wouldn't doubt that a Suncat could hang with displacement boats larger than her size.