Association Forum - Speed vs. Distance

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Speed vs. Distance

New Topic

Topic Locked

Printer Friendly

Author

Topic

bbriner
Captain

Member Avatar

349 Posts

Initially Posted - 07/16/2006 : 16:21:36

I was out the other day playing around with different points of sail to see the effect on speed. What I did was I went close-hauled on both tacks then pinched up until I was just starting to luff then noted boat speed, which was about ~5kts. Falling off 20 degrees increased boat speed (SOG) to about 6 kts (Wind speed was about 20kts). This held true on both tacks. (Note - pinching allowed me to tack through 90 degrees).

Now we normally race a 2nm upwind leg (sometimes twice) on Friday night beer can races. Naturally, being rookies, we usually just try to go 'as fast as we can' which probably means we are sailing off on a close reach (or worse). We have lots of fun (we are the only boat in the fleet with a magma grill on the rail :)) but we usually come in last. Guess why?

What is the difference in distance and time between these two courses? On a 2nm course, sailing 20 degrees off a close hauled course at 6kts vs close hauled at 5kts means sailing 4.7 nm instead of 2.8 nm - a difference of 14 minutes!! Yikes!! No wonder we're coming in last.

Of course pinching up makes the boat feel sooo slllooowww. It doesn't heel as much and you're going 15-20% slower so it is doesn't seem like the right thing to do but the numbers don't lie. It's also a wetter course - lot's more bouncing in the waves since it's more head on but I didn't notice great loss of speed (it's nice having a heavy boat when the waves are big).

What do you expert (or non-expert) racers think? What has been your experience??

Bill B
Wind Dancer
#4036 84 SR/FK
San Francisco Bay

Edited by - on

ClamBeach
Master Marine Consultant

Members Avatar

3072 Posts

Response Posted - 07/16/2006 : 16:36:22

Enter a dead upwind waypoint a mile or two out on your GPS and note the VMG as you try different points of sail.

Better yet, (assuming the upwind mark is a permanent feature) enter it's coordinates on the GPS and use the VMG as a guide for finding your best point of sail during the race.

Edited by - on

Steve Milby
Past Commodore

Members Avatar

USA
5908 Posts

Response Posted - 07/17/2006 : 09:06:30

When you're beating to windward, the object is to sail as close to the wind as you can at the maximum possible speed. In doing so, you sail the shortest possible distance at the highest average speed.

On a C25, the sail trim will largely dictate how close the boat can sail to the wind. If you're using a 110% jib, the leech of the jib should be trimmed to within 1" of the spreader. If you're using a 150% jib, the leech should be trimmed to within about 6-8" of the spreader. If either sail is trimmed any closer, it will be too flat, and lose power. If it is too far from the spreader, the boat won't point to windward - it'll bear off a few degrees, requiring you to sail a longer distance.

The other important factor in beating to windward is helmsmanship. If you steer the boat just a degree or so too close to windward, the boat will "pinch" and lose speed drastically. The objective is to steer the boat just far enough off the wind so that the luff of the sail (the leading edge) just lays down, and the telltales on both sides of the sail are streaming aft.

I've heard it said that, if you want to maximize the boat's ability to point you should bear off. That sounds counter-intuitive, but there's a logic to it. When you bear off very slightly (about a degree), the boat's speed is maximized. When the boat's speed increases, the apparent wind speed is increased, and that increases the power generated by the sails. In short, increasing your boatspeed increases your ability to point to windward. Therefore, to sail to windward at the highest speed while pointing closest to windward, you should sail a scalloping course - bearing off slightly to increase your speed, and then steering up to windward briefly by a couple of degrees to take a little bite to windward, at which time the boat loses speed slightly, and then you bear off slightly again to regain maximum speed.

Edited by - Steve Milby on 07/17/2006 09:10:56

Champipple
Master Marine Consultant

Members Avatar

USA
6855 Posts

Response Posted - 07/17/2006 : 10:04:37

What he said…most of it anyway. If you are truly pinching you would be going slower than 1 knot difference. In 20 knots of air, everything should be really tight, with the Jib all the way in, ours almost touches the spreaders, weight on the High side to reduce heel, main up on the traveler and in on the sheet. You will probably only use the first third of the main, the rest will be backwinded. Steve is right about the scalloping, real good helmsman can hold that groove for an entire leg…. It is almost impossible to do in our boat, but still can be done. If your sails are trimmed correctly you should be making 6+ knots in that breeze.

If you have a GPS, go find a spot on your pond with a mark or tie the anchor to your fender and mark that spot. (make the spot upwind) Set your GPS to show VMG and Speed at the same time. Sail downwind about a mile and then turn around and head back to your mark. As you do the same exercise that you did above, compare your VMG to your speed and point of sail. You won’t have to do the math, the VMG should go higher as you sail higher, until you luff from pinching.

Edited by - on

bbriner
Captain

Members Avatar

349 Posts

Response Posted - 07/17/2006 : 13:50:23

I'll definitely use the VMG on the GPS for the next race (this coming Friday). That sounds perfectly logical (doh!). Since we sail around fixed bouys so they are all in there already - I just have to change the display to include that metric. I should have said that instead of **really** pinching, I was really measuring speed while trying as much as possible to stay 'in the groove'. Of course what this is all about is that since speed continues to increase as you bear away it is tempting to keep bearing away!! I've got to stop doing that!!

Thx Guys..

Edited by - on

Heartbeat
Navigator

Members Avatar

USA
161 Posts

Response Posted - 07/18/2006 : 19:32:50

Steve and Duane covered most of the points. Good stuff, there.

I do have one point to add, though. This is mostly a lighter air thing, but it always applies. The C25 foils are much thicker than some of the more competitive boats - think Express 27, J24, etc. The C25 has great waterline length, but needs to breathe. I sail the boat to windward really fat because the foils don't get any lift unless there is a good amount of flow across them. I sheet my (pentex or kevlar) 155 into about 1 - 4 inches off the spreader. (4" in light air, less when it blows.) Then I watch the tails. (Oh, and put at least 3 sets of tails on the sail.) Get them all flying back and keep them flying back - you will be a rocket to windward.

Oh, one last note. Don't get in a pointing fight with anybody - you will lose. (Ok, you will beat a full keel boat.) The waterline length is your strong point - lay off and use it, just don't lay off too much.

-Matt Q.

Edit: clarified sheeting distance.

Edited by - Heartbeat on 07/19/2006 10:31:55

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 07/18/2006 : 22:28:38

Good advice--find the highest groove where the sails are working well for you, but don't try to point with a J-24--it can't be done. Downwind is a different story--staying a little off the wind can increase your speed enough that it more than makes up for the increased distance. Here again, VMG on the GPS can tell the story, and can help you find the lay-line.

Edited by - on

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.