Video analysis

Disclaimer: The catamaran in the video is not a Hobie Cat, however I would like some opinion on what is happening at a specific point in the video. At 59 secs in the boat appears to be sideslipping. Around 1:15 the helmsman steers to port and the boat takes off.

The boat is a Supercat 17.

Here's the link:https://www.youtube.com/watch?v=uFTTrReXWNc&feature=youtu.be

Thanks.

It appears to be perspective / camera angle. From the front it looks slower. Once the boat turns up and more sideways to the camera, you can see motion easier.

Some of the side slip look is from a video fade... overlay.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Adding to the effect is the wave blown water to leeward. I bet if you could draw a course line, it would be straight. The lee hull and rudder are the primary wake and spray makers, which are getting blown by the wind, giving the effect that the boat is slipping to windward. But we know the boat is slipping some to leeward. If not, I would not want to race against this boat.

He definitely steers an "S" course . . .

At 00:59, he is heading on a beam/broad reach, yet his sails are over trimmed for it, so he's not going as fast.

Shortly thereafter, he's hit by a gust (barely visible on the water), he sheets in, heads up and takes off.

However, his sail trim in almost all cases is pretty sad - there's too much twist in the main with that big square-top.

Great Drone shot btw...

While the drone is over water and compensating for the wind to stabilize, I wonder where the "pilot" is? If on the boat then that was outstanding. Must be a concern to risk drone and camera getting out of range with 15K breeze over water.

I'm jealous ;-]

_________________
HH the Great Ham
Bravo Owner

Agreed his trim could be better, but I don't know what you have against twist. Twist is important. The actual as well as apparent wind is different from one level to another as you go up the mast. Your sailmaker builds twist into the sail. If you remove all the twist with traveler and sheet, you will usually stall part of the sail. Of course there are exceptional days where the windflow is laminar...but that's the exception. I suspect you have read "High Performance Sailing" by Frank Bethwaite...he has a really nice photo showing the wind at different levels on a mast.

_________________
R/Thom
SeaRail 19
Triak
BMW C600
Formerly Getaway with Custom Spinnakers
Formerly raced F24 Mk II

I don't have anything against twist. As you say, twist is important to accommodate the vertical velocity shear / gradient so that the upper part of the sail creates more lift than drag.

However, a Supercat 15 was originally designed with a pin-head main and a boomless rig. Those are aftermarket sails in the video.

Sails with big square-tops like these require a lot of vertical sheet component to remove excessive twist from the top of the sail. (That's why the mainsheets on F18s have a 10:1 purchase.) You can't get that kind of vertical sheet component on a boomless rig and especially without using the traveler.

Looking at the video again, the mainsheet never moves far from the middle of the rear crossbeam - he's not using the traveler. Also, at about 01:20, when he heads up in the puff, you can clearly see the upper part of the sail luff (look at the red panel). There's too much twist.

The bottom line is that there are two guys out having fun on a catamaran - and it's a fairly well put together video. They're not racing and we shouldn't judge them as if they were.

Hi folks, that is me and my boat in the video - I found this by accident... while searching for this video somewhere else!

Since I am sitting in a hotel with nothing to do today... here is some info.

I started sailing with a Hobie 14 and then moved up to a 16 which I owned and raced for a number of years - to modest success. Then a bunch of us in Minnesota bought Supercat 17s in the 1980s and 90s. I sailed my 17 all over including a one month solo trip from Chicago to Mackinac Island and then to Green Bay in 1990. In 2010 I fulfilled a life-long dream of sailing across an ocean when a friend and I went from Duluth to Portugal and back on a Dufour 41.

Enough about me and on to the video.

A friend at the lake is a professional videographer and wanted to try out his new drone. He ran it from shore and asked me to stay close to shore as much as I could. Everything would have worked better if he could have run it from an anchored boat in the middle of the lake. But, if anything goes wrong with the drone it will go back to where it took off from and if the base (or boat in this case) has swung at anchor or moved, the drone ends up in the lake.

My crew was his friend who had never been on a sailboat before! You guys will appreciate what a good job he did out there on his first day sailing AND trapezing. It really was a blast.

The sails are aftermarket sails - per the earlier post. Even the boat’s designer, as he bought new sails, went to square-top sails. I don’t have anyone to race against so I can’t say anything about a head to head comparison. This boat will beat a Hobie 16 but not an 18. The Portsmouth numbers bear that out the last I checked. It also will not pitch pole except in the most dire circumstances. It still amazes me that I can bury a bow, pucker up, and watch it pop out of the water!

As to the part of the video that was discussed, I came in close to shore - too close as the wind starts to lift to go over the trees. I overtrimmed the main so that when I turned - as noted - the boat really took off. I knew I wouldn’t have time to do much adjusting after the turn so in effect, I set the sails up for the new course and then turned. I posted this video to our Supercat forum and those guys also commented on the apparent slide slipping and the seemingly odd way the wind and waves made it look.

I have gotten a bit lazy and don’t use the traveler much unless it is really windy. Although if it gets really windy, I just roll up the jib and use my old Hobie 14 skills and sail that way and have to try and tack without going into irons...

And since we are all part of the same community here are a couple photos, if I can get them in. I’m not sure if your forum allows photos. One is me and my sister pulling my brother on water skis behind my Hobie 16 and the other is two friends and I triple trapezing on my Supercat 17. We brought one wire over from the other side and got him to climb out on our shoulders. I posted that one to our Supercat forum and got roundly spanked by the boat’s designer. His post included “someone is going to get hurt.”

Photos need to be hosted on a public site. You can link them here.

FAQ: https://www.hobie.com/forums/viewtopic.php?f=18&t=8574

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)