An odd sailing situation

Stu Jackson · Jul 18, 2011

Unless you tell us what you did with your sail trim, there's not much we can discuss.

Stu Jackson · Jul 18, 2011

Apparent wind died.

Bill Roosa · Jul 18, 2011

think of riding a bike in a circle at 5 knots forward speed and the wind coming from the north at 5 knots
then you are going north the wind is dead ahead at 10 (beating) when you are going east or west the wind is 45 degrees from your dead ahead and at 0.707*5 knots when you are going south you have not wind at all.
As your boat speed and true wind speed get close all you can do is beat or go real slow. Kinda the opposit of an ice boat that can only beat due to its high speed.
the only solution for this is a lightweight and really big foresail. something in the 1 oz weight.

Alan · Jul 18, 2011

Did you move the genoa cars forward? Did you ease mainsheet? traveler? ..how did you adjust the vang as you bore off?

It's all in the trim!! Sailing theory doesn't change much in the boat sizes we are dealing with. If you don't correct the trim as the angle of attack changes then of course you'll slow the boat down. If your sail trim is good for a beat then it can't be right for a broad or beam reach.

OldCat · Jul 18, 2011

Mike 1 said:
I changed to a beam reach and slowed to about 1 kt. tried all different sail trims, went to a broad reach, stopped more or less except for drifting I moved back over to close and took off. The boat is a shoal draft which I know can play with how it sails on different point but is it that dramatic normally? Mike

Hmmmm... methinks that perhaps the only point of sail where "shoal draft" would cause a performance issue is close hauled where you need lift underwater from the keel.

I guess the next question is - do you have telltales near the luff of the Genoa?

OC

Bill Roosa · Jul 19, 2011

Hey Alan
How do you trim a sail made for 15 knots when you only have 2 knots of wind?
I've found that no matter how I do it the heavy fabric just will not fill with air.
My 1 oz asymmetrical however fills nicely in only 1.5 knots of wind and while it is not a rocket at that speed the boat does move much faster than with the jib.
But if there is something I'm missing I'm interested. Just don't see how you can trim a sail outside the range of wind it was designed for.

OldCat · Jul 19, 2011

Bill Roosa said:
Hey Alan
How do you trim a sail made for 15 knots when you only have 2 knots of wind?
I've found that no matter how I do it the heavy fabric just will not fill with air.
My 1 oz asymmetrical however fills nicely in only 1.5 knots of wind and while it is not a rocket at that speed the boat does move much faster than with the jib.
But if there is something I'm missing I'm interested. Just don't see how you can trim a sail outside the range of wind it was designed for.

Can I add to this question? It appears that when the wind dies that fully battened mains do better - they hold a shape when the mains go limp. The racers here all use fully battened mains. Also the high tech laminate head sails appear to hold shape better. I see this comparing many boats.

Is a fully battened main better in very light wind that won't fill the sail? Do high-tech head sails hold shape better, or am I looking at the result of more trim expertise?

OC

Alan · Jul 19, 2011

That's a very valid question, Bill. The answer is you use the sail that is designed for the conditions it was made for. I have a sail inventory to handle light air all the way up to 35+. In 2 knots an asymmetrical chute or light air reacher will work better than a heavy jib/genoa. Reaching off in ultra light air with a light air sail will of course out perform a heavy sail. Also moving crew weight to the leeward rail to induce heel and minimize the use of rudder will help.
You can trim the sail outside its designed range but the further it is from that range the less effective it will be. This is the fallacy that sailors with roller furling headsails are prone to fall to. There is no such thing as a one size fits all sail. It's like trying to drive your car in only one gear.

Bill Roosa · Jul 19, 2011

So no amount of trimming is going to help in 5 knots of wind trying to go downwind at 3+ knots boat speed. you need tochange sails. the best your can hope for is 5 knots of boat speed unless you can sail faster than the wind. While mathmaticaly possible i've never heard of a displacement boat going faster than the wind. Heck, if I can get to half wind speed Im happy.

Alan · Jul 19, 2011

In 5 knots true wind and sailing down wind you would need to sail an angle of 105 or there about to produce any real boat speed. Using good trim adjustments is the difference between standing still and moving at a respectable speed. That would be your optimum boat angle for best VMG. Some of the large sleds can easily sail faster than the wind.
The whole point though is to match your sails and trim for the conditions to get the most out of your boat.

Calif. Ted · Jul 19, 2011

Your situation is odd Mike because it's doesn't appear normal, I must admit to some difficulty in understanding exactly what happened. I think the polar diagram for a Cat 34 which I'll attach will be helpful in comparing sail trim with speed and wind direction. As a rough rule of thumb these relationships exhibited on the diagram are true of most keelboats.
http://www.c34.org/faq-pages/images/polarDiag.gif
I'm surprised Stu didn't already point you here, he must be distracted

Regarding full batten mains, I've sailed the same boat using all full, 1 full, 2 full and my answer about light air shape is "Maybe, some" seems like the difference between 2 full and all full is minimal and either works about as well.
High tech sails do hold shape better because they are lighter and they are made with the shape built in, kind of. They use a 3 dimensional mold and lay the sail out over it.

RichH · Jul 19, 2011

Do you have TELL TALES affixed to your sails??????

If not, and more so in 'light' winds, there is absolutely NO way you will be able to even come close to 'trimming' the sails ... so that the flow of wind is *across* the sails which generate the needed 'lift' (and in accordance of sound aerodynamic principals).

If not, suggest you get a simple manual or instruction book which explains the mechanics of sail trim via the use of tell-tales. A good starter would be Don
Guillettes "Sail Trim Users Guide" http://shop.sailboatowners.com/cat.php?18381/Books/Games. Apply the tell tales to the luff, midcord and LEECHES of the sails ... and simply follow what the these tell tales are 'telling you'. If the tell tales are not 'flying' correctly, there will be NO aerodynamic flow across the sails and the boat will either slow down or stop. You can only sail well 'watching the tell tales' and trimming the sails based on what the tales are showing. You cant trim based on some 'preconceived notion', you can only trim correctly based on what the tell tales are showing you ... a FULL set of tell tales: at the luff, at the midcord and at the leeches!!!!!!!

Joe · Jul 19, 2011

Tell tales are very important, but not very usefull on downwind legs.

Jon Bastien · Jul 20, 2011

Hello all,

I didn't see it addressed in previous replies-- What are you using to track your speed? A GPS and a knotmeter are tracking your speed relative to different things- The GPS is tracking speed over ground, and the knotmeter is tracking speed through the water.

I'm not familiar with the sailing conditions in Sandusky, but in most large bodies of water where I've sailed there were currents to be factored.

Consider:
If you're moving at 3 knots into a 1-knot current, a knotmeter will indicate 3 knots (through water) but a GPS will indicate 2 (over ground).

If you're moving at 3 knots in the same direction as a 1-knot current, a knotmeter will say 3 knots (through water) but a GPS will say 4 (over ground).

So, Is it possible that Mike is using GPS to take his readings, and:
- Beating upwind/down current at 7 kts SOG (5 kts speed + 2 kt current),
- Running downwind/upcurrent at 2 kts SOG (4 kts speed - 2 kt current), and
- Reaching across both wind and current at 3 kts?

--Jon

OldCat · Jul 20, 2011

Joe said:
Tell tales are very important, but not very usefull on downwind legs.

With a spinnaker? Or:

You and Rich appear to be in disagreement on this, at least to some degree, or the terms used, or wind speeds intended.

~DDW, w/o spinnaker, OK, tell tales don't matter. W/O Spinnaker:

Rich ran a post a while back challenging sailors to reach downwind for faster VMG downwind. I will take a stab here and define a reach as off the wind but still sailing with flow over the sails and telltales flowing, and ~DDW as too deep to get the flow attached.

My efforts to put Rich's words into action resulted in me finding out that I could go deep enough on Genoa and Main to achieve ~105* apparent wind and still have Genoa telltales flow and main leech tales flow. I need to mount a GPS and measure VMG to determine in what winds reaching down beats ~DDW sailing, but the concept of reaching DW as opposed to a 'barn door' sail trim DW does seem to work.

Also, the OP only mentioned sailing down only as far as a broad reach in the original post, hence the tell tale questions.

OC
*approximate, no electronic gauges.

Alan · Jul 20, 2011

Jon a good question. With respect to sail trim I always you the knotmeter. Its response time is faster and reads in the hundredths of a knot. For piloting and navigation the GPS is more appropriate.
It is important to point out the many boats have their knotlog located off the centerline of the boat. This causes a built in variation from one tack to the other. I moved my log to the centerline to eliminate this issue.