Speed difference between Port and starboard tack

[msc1212]

This is going to yet again illustrate my novice status but today I went for a beautiful sail on Lake Ontario. It was a rare fall day- there was a 10-12 knot wind from the southwest with absolutely no waves- the lake was virtually dead calm except for a terrific wind. On my starboard tack I sailed at 6.4 to 6.9 knots with a 150 genoa 45 degrees to the wind. When I tacked to port the best I could get was 5.1 knots at the same angle and wind speed. The wind was consistent between the two tacks, the waves were non-existent. I trimmed and trimmed and couldn't find any more speed on port so I tacked back to starboard- the speed jumped back to 6.4-6.9 knots. I tacked back to port and the speed dropped again.

I've been sailing this boat for two years on Lake Ontario and this was the first time I had consistent and sustained conditions that would allow me to observe this. Why the difference? Is this a rigging issue? Does my boat just not like port?

As always, any advice would be greatly appreciated.

Michael

 

[Morgan Stinemetz]

Michael,
My bet is that it would be a rigging issue. Boats have to be "tuned" like a piano, and that is best done under way. If you are asking the questions you are asking, it is better to get a professional sailor to help you do it. There are a number of steps that have to be done in chronological order to be effective. This entails being certain the mast is in column, etc. Messing about with it yourself will put you up against the learning curve, and that is the slow way. Paying someone who REALLY knows his stuff, as opposed to someone you picked up at the marina who SAYS he is good, will save you a ton of time and heartache. Good luck.
Morgan Stinemetz

 

[sleather]

Twaaang!

Having spent many hours "tuning" E-Scow masts(as well as my own) there are a few simple things I can recommend before you call for help. First thing is to determine "if" your mast is vertical. Simply attach a tape measure to the main halyard and raise it until it's snug @ the masthead. Then measure the distance to the same spot on both chainplates. Any difference will tell you if its out of plumb(good chance) Adjust the "upper turnbuckles" until you get equal values. The tension for your boat is better answered by a "higher power", but a good "rule of thumb" is not having any slop in the leeward stay while underway.

With the mast "in column" you can then lay on the cabin top while underway & sight up the mast to see if the mast bends to windward or leeward @ the lower shrouds. Again specifics are better left to someone that knows the boat, but if it's straight on both tacks you'll be in the ballpark.

I hate to ask this question(you never know), are your "jib" lead blocks in the same position on the tracks?

This may be a moot point as sailing on Lake Ontario is about to become history for the season! Good Luck!

 

[Brian K]

Me Too!

Michael, this is very interesting to me since I have observed the same phenomenon, not only in my Ericson 32-200, but in my previous boat. I also sail on Lake Ontario maybe it's the lake? I carefully tune my rig each year, but next year I will take the extra step and measure to be sure the mast is in column.

 

[e38 owner]

How did you check your speed

Some varience can be due to the placment of the tranducer and water flow.

 

[tenders]

Weight distribution could also make a difference.

Were you measuring by GPS or by hull-mounted speed wheel? If by GPS, set and drift could easily account for a knot of speed. There is some current in Lake Ontario, I'm told, and the interaction between wave direction and windspeed can make a difference even if the waves aren't large.

If by speed wheel...those things are notorously inaccurate. An extra zebra mussel and gravity pulling from a different direction could easily explain the difference.

 

[sleather]

Sea Monsters?

Any current would be a SW-NE flow, wait for a SW wind!
E38's response is "very" likely, do all your testing on GPS! I seem to remember a similar issue w/ mine.
After addressing ALL of the ABOVE & you still have a differential speed, you must have a "sea monster" stalking your boat!

 

[Seth]

2 reasons

Assuming you are using a knotmeter and not a GPS (a knotmeter is the only way to do this-a GPS gives you groundspeed-not speed through the water. That means the GPS speed will include current and leeway effects-none of which relate to your boat speed), the 2 primary reasons for speed differential from tack to tack, and assuming the trim is the same and the leads are in roughly the same spot on each side, are: A). Rig tune-your mast is significantly off to one side. Of course if this were true, you would notice the clew of the headsail much higher off the deck on one tack than on the other at the same trim point, or B). Speedo head placement. On many cruising boats, the speedo is off on one side of the centerline, and this will definitely produce a difference from one tack to the other, and the greater the heel angle, the greater the difference.

Given the large difference in speeds and the fact that you were well heeled over, my bet is B.

Check it out and let us know!

S

 

[NateHanson]

5.1 versus 6.9 is a really big difference, and certainly one you could feel and see (without looking at any instruments). Ignoring the GPS or speedo, did the boat feel much slower to you? If not, it's likely the paddlewheel placement, as others have said.

If you really felt like you were going 2 knots slower, then I guess the next thing to do would be to tune the rig.

 

[Loren Beach]

One basic assumption that perhaps needs a second look is the stated angles on each tack, reading from the opening message in this thread.
If these were taken from a wind instrument transducer at the masthead, it is just possible that the information was not true... Or the cockpit readout is not accurate.
The position of the transducer relative to one side or the other or relative to any disturbed air off the main could make a difference.
I guess that what I am wondering is if the boat is being steered to the angle on the instrument face, and if that angle is not correctly displayed, then one tack is being sailed slightly stalled compared to the other.


One would want to be sure that the main and genny are actually trimmed and led the same on both tacks, and that the tell-tales on the luff (and leach of the main) are flowing the same, and that the sparfly looks the same to the ol' Mk One Eyeball...

For that matter, are the genny tracks installed identically on both sides of the deck? (I am sure they are, but basic trouble-shooting protocol is to assume nothing...)
Anyway, best of luck on solving this mystery.
Loren in PDX

 

[Kevin Johnston]

Heel

The degree of heel must also be considered. The boat moving through the water with even a slight variation of heel could be pretty significant. Movement and placement of the crew will affect the speed of the boat through the water.

 

[msc1212]

Thanks for all the advice. The boat was trimmed the same on port and starboard including the cars. I used my Raymarine wind speed transducer to establish the angle although I also used a windex. I used the GPS for speed. I have a speed transducer which I find mostly useless except to monitor small trim adjustments. There really isn't a current where I was sailing. I was single handing the boat from the centre of the cockpit. I was sailing next to the dreaded Beneteau that I have raced all summer. He and I were 100 feet apart and travelling at the same speed on the starboard tack. When we both tacked onto port, he left me like I was dragging an anchor.

I think I need to measure my rigging. That is the one variable that I can't account for. I figure with global warming and a good sweater I might just be able to squeeze a few more weeks out of the season. Thanks

 

[sleather]

I think I need to measure my rigging. That is the one variable that I can't account for. I figure with global warming and a good sweater I might just be able to squeeze a few more weeks out of the season. Thanks

Good Luck, You've got us all confused! You may even have a month left, who knows. Catch that "October--Lake Michigan----" Thread!

 

[msc1212]

I spent this evening measuring my mast rigging. From the top of the mast to the starboard toe rail I measured 42'10". On the port side the measurement was 43'. There was also a bend in my mast that I had never noticed before. The mast was bowing out to starboard. I spent about two hours adjusting all the shrouds to straighten it up and centre it. I thought I had done this in the spring and had taped and cotter pinned the turnbuckles. I do know that I beat up my boat last month in a race. I had an accidental jibe and a knock down in a single handed race with winds from 25-35 knots. Ater this I thought I had cracked a chain plate although after very close inspection all I had done was shifted the caulking around the chain plate. I think the loads from this race may have actually shifted the shrouds/turnbuckles. I didn't think this was possible but its the only thing I can think off that would have thrown the mast rigging so far out.

I'll sail this weekend and see if there's an improvement.

For the past two years I've hauled out the second week of November. I'm the last one to go: both times it was snowing and there was ice on the deck.

Thanks for the advice.

Michael

 

[sleather]

Major Issues!

I had an accidental jibe and a knock down in a single handed race with winds from 25-35 knots. After this I thought I had cracked a chain plate although after very close inspection all I had done was shifted the caulking around the chain plate. I think the loads from this race may have actually shifted the shrouds/turnbuckles. I didn't think this was possible but its the only thing I can think off that would have thrown the mast rigging so far out.

Michael, I didn't make the connection until now! You're the "New Chain Plate" guy! Reread that description you gave us! I had made a comment, in that thread, that you might have some "major issues"(see the P.S.). I should have been a bit more persistent at the time! Chain plates SHOULD NOT move! Explains her weird behaviour, the mast was all screwed up.

I strongly recommend that you have the "structural integrity" of the entire chain plate and anchorage system below inspected by a qualified expert! Better safe than sorry!

I almost lost my mast in '01 because I neglected to notice deterioration in the bulkhead below. I came in from a 30+blow and the whole rig was "loose". The port chain plate had moved vertically approx. 3/4" and the only thing that was holding the mast up was the top anchor bolt being lodged against the cabin liner. Granted it would have taken awhile to chew thru the liner & deck before it failed, but it would have only been a matter of time!

Good Luck, You made it through the season!

 

[msc1212]

issues

Thanks very much for the post. I agree that I have some serious issues with the chainplates. The starboard plate has moved upwards about 3/16" from where it was at the beginning of the season. It happened after the knock down and jibe that I mentioned. Originally it looked like a crack in the plate but when we looked closely what we realized is the chainplate had lifted out of the bedding compound on the deck. It looked like a crack but was actually just the shoulder of the chainplate which had been pulled out of the bedding compound. . I've exposed the chainplate below deck and am trying to find any faults in the bulkhead. The chainplate was rebedded several years ago. The bulkhead is newer plywood than the surrounding material. I think I will need to get a surveyor in to help me because i can't see anything wrong except for the fact that the chainplate did move. The movement of the chainplate and the shift in the mast are likely related and came from the same source. Thanks for you advice.

 

[NateHanson]

I'd pull that chainplate out completely. See what condition the bulkhead is in where it was attached. Make sure there isn't a crack in the chainplate that is hidden inside the deck. Also, check the tabbing all the way around that bulkhead. If the chainplate is intact, and it's firmly attached to the bulkhead, but the chainplate went up a quarter inch, then the bulkhead must have gone up with it. Check the tabbing to the hull.

Good luck!

 

[msc1212]

Thanks for the response. What do you mean by tabbing? The bulkhead is fibreglassed to the hull. The chain plate is bolted through this bulkhead. I need to look for signs that the fibreglassing failed along the seam between the bulkhead and the hull. Also, any distortions in the bulkhead itself. Is this correct?

Thanks

 

[NateHanson]

Yes. By "tabbing" I mean the fiberglass strips that connect the bulkhead to the hull.

 

[sleather]

Wounded, but not Dead!

Michael, My guess, based on the amount of movement, is that the holes in the bulkhead(under the chain plates) have elongated due either to the stress of the "event" or deterioration of the bulkhead! If the connection has been redone, perhaps the anchor bolts were not tightened sufficiently!

Just take'r apart yourself when you "pull" and have the chain plate and bulkhead examined. There should be any number of "fixes" to bring her back to "good as new"!

Good Luck