SF 37 / SO 37: a nervous boat?

[sf37]

Hello everybody.

I'm a proud owner of a Sun Fast 37 since last summer and started to make my experience. While the speed is really nice (she goes easily to 7 knots and above) I am still stuggling with the pointing caracteristics. I would like to explain my expressions:

At low wind speeds the handling is really easy. There is very little (too little?) force neccessary to turn the steering wheel. With increasing wind speed (more than 20 knots) it becomes more and more difficult to keep the boat on a strait course - even with a lot of trimming and if the sail area is reduced to two reefs in the main and a genoa III. This is the case for all cources (close to the wind to down wind). Standing at the steering wheel, there is only little reaction if the rudder has an angle below 10 degree. With higher rudder angles, the forces on the rudder are suddenly very high. It feels a little bit as if the steering cables have some slackness - but the don't have. Or if the shape of the rudder is ineffective.

Did any of you made similar experience? The SO 37 has the same hull, but a litte different rudder - so it would be very interesting, if the SO 37 sailes well ballanced even at strong winds.

Thanks for every comment!
Jochen

[davideso37]

Hi Jochen,

I think the SF37/SO37 is a very fine hull and these yachts behave as well as any. We do well in strong breeze races because we round up less than the other yachts in the fleet. The more the yacht heels the more the yacht will want to round up to windward and the harder it is to keep her tracking straight. We have to constantly dump mainsheet quickly to prevent heeling too far and rounding up but as I said we do better than most in the fleet.

Regards

David

[MalcolmP]

What are your sails like? If they are getting baggy that will introduce heel and make the whole rig unbalanced. Guess you have checked that mast is vertical and you have correct shroud tension etc?  Depending on your own experience and knowledge of rig tuning, (and if it is as limited as mine..) it might be well worth getting the skipper from one of the successful local similar sized race boats to come out with you to ensure that your rig and sails are all correctly set up

[sf37]

Jan 13, 2014 12:10:38 GMT davideso37 said:

Hi Jochen,

I think the SF37/SO37 is a very fine hull and these yachts behave as well as any. We do well in strong breeze races because we round up less than the other yachts in the fleet. The more the yacht heels the more the yacht will want to round up to windward and the harder it is to keep her tracking straight. We have to constantly dump mainsheet quickly to prevent heeling too far and rounding up but as I said we do better than most in the fleet.

Regards

David

Hello David,

Thanks for yor reply. To give you more details on the behaviour of my SF 37 it is not a problem that the yachts wants to turn to windward. The yacht wants to go left, a second later to the right, another second later to the left again. She simply doesn't want to follow the course I want to steer.

Do you know this feeling from your SO 37? Is it possible that the SO 37 is more ballanced compared to the SF 37?

Jochen

[sf37]

Jan 13, 2014 12:42:51 GMT MalcolmP said:

What are your sails like? If they are getting baggy that will introduce heel and make the whole rig unbalanced. Guess you have checked that mast is vertical and you have correct shroud tension etc?  Depending on your own experience and knowledge of rig tuning, (and if it is as limited as mine..) it might be well worth getting the skipper from one of the successful local similar sized race boats to come out with you to ensure that your rig and sails are all correctly set up

Hello Malcolm,

Yes, I checked the mast and the rigging. I'm definetely not an expert, but I think the trim is OK.
But: The fore sails are designed with a rather bulgy cut. It is not possible to trim them so that they are flat. This might be a reason for the unballenced behaviour.
On the other hand it is funny, that the unballanced behaviour is on all cources the same. This is why I think that the rudder blade might be not ideal???

Jochen

[MartyB]

Have a sailmaker look at the sails. That bulgy sail may be your issue. It might be recutable, or you may need a new one.

Also, have you literally checked the tension on all the stays/shrouds? if too loose, you can get some handling issues. Also look at the spreaders. Are they parallel upper to lower, and many times, slightly end pointed up to level to the horizon.

Not sure it will be as big an issue on an SF37, but where I put wt and crw on my Arcadia at 28' on deck, can change how my rudder feels as far as balanced vs major weather helm.

Just a few other things to check out before going after the rudder itself. Altho if you have a wheel vs the std tiller, I suppose it could be with in the steering mechanism too.

Marty

[j]

It just sounds like the boat is overpowered when you are experiencing difficulty steering.

Are you twisting off the main and jibs leech to depower when the windspeed increases (moving the jib lead block aft)?

Baggy sails would not be helping the situation as it increases the heeling power in the sail and makes the sails shape unpredictable and difficult to trim.

Is the leech hooking in on the headsail? This can make steering difficult.

Rig tension is also very important.

This article is really good if you need to improve your trimming: ianshortsails.com.au/sail.trim/

[rene460]

Hi Jochen,

I suggest the issue is sail shape and stability, not hull or rudder.  I have an SO 30i, not a 37, but I can relate to your comments on not being able to keep a straight course.  We needed nearly half a turn of the wheel in each direction to keep a straight course and did not seem to point very well.  The issue turned out to be not just the baggy sail shape, but the location of the deepest draft, which was too far aft.  In addition, the sail cloth was too stretchy, resulting in shape changing with wind strength.  After two different sail makers gave us the same precise diagnosis of our handling problems, and similar opinions on the sail shape, we tried a luff recut to see if the problem could be solved easily, but not expecting too much.  Not expensive and a bit of help, but still could not trim sails to more than one set of tell tails, I suggest you skip that step.  Talked to the sailmakers about cut and cloth and durability and using furlers etc. and chose one for new sails - main and genoa.  It was like magic.  Now requires small movements with one finger on the wheel, and can sail a mile on each tack with no hands on wheel - no auto pilot, no steering wheel lock, just good balance.  All indications are that we are much faster, and able to sail closer to the wind even in very light conditions.   My wife and I are both delighted with the result and sincerely recommend the advice above to show a sail maker your sails.  Preferably show some pictures from under sail straight up from about mid boom position on the main and from deck level on the genoa then take the sails in to the ones you feel you can talk to.  And be prepared to pay a little more for the best cloth and cut recommended for your type of sailing.
rene460

[sf37]

Marty, j and rene,

Your comments really calm me down. I more confident
that I did not purchase a catastrophical boat and that I have good chances to get it more ballanced.

When the season starts in April I will pay more attention on the rigg.

Additionally, I will get in contact with a sailmaker an show him some pictures of the sails.

Acctually, the sails are really "high tec". They are made by UK Sailmakers, the cloth is of type "tape drive". Nevertheless the genoa III has the tendency that the leach flutters. I need to shift the sheet rope block forward. As a result, the sail becomes very bulgy.


Jochen

[MartyB]

THere should be a leach line on the back that you can tighten to stop this flutter. Most GOOD to excellent sail makers will include this. Even some of the cheap cheap ones include a leach line.

Bulgy as you describe is good in light winds. But the car back in heavier winds is better.

Now just because you have a UK Tape drive, my main is this material, does not mean it is not worn out, stretched or equal, or plain shot if you will. ALL sails, being as they are our motors, will wear out, and when they do, they will not power you up as well, cause heeling, wrong/incorrect helm issues, premature furling to stay level.....

You are on a better track than where you started. IF you really do not want that boat, I have an 85 Arcadia that does steer straight, If I can get it from where you are from the US pacific NW.....I'll trade you! no questions asked. ALtho I would really prefer the SF35 for various and sundry reasons, but the SF37 would be 2nd on the list........

marty

[electricmonk]

Without sailing with you its always going to be difficult to know exactly what is going on here. I had the SO37 with a shoal keel and in-mast mainsail. It was a very easy boat to sail well, nervous? no - but it would give clear signals that you were "out side its envelope" - signals similar to those you describe. I quickly came to the conclusion that it is a 20/20 boat - defy that at your own risk. If you want to sail with the side decks awash you will have your hands full. We regularly sailed it to windward in over 30 knots with no issues, perfectly balances and no weather helm.

Rig set-up is critical and the genoa driven sailplan needs careful reefing to produce rudder balance and speed but once you have found the sweet spot its OK.

You will find other comments I have made about the shoal keel/in-mast combination on the forum somewhere - in my opinion it makes the boat slower but if you keep within the envelope its a great boat.

[sf37]

Jan 15, 2014 3:36:17 GMT MartyB said:

IF you really do not want that boat, I have an 85 Arcadia that does steer straight, If I can get it from where you are from the US pacific NW.....I'll trade you! no questions asked. ALtho I would really prefer the SF35 for various and sundry reasons, but the SF37 would be 2nd on the list........

marty

Sorry Marty,

But there are too many nice features of the SF 37 to sell:
Fast, especially if sailing close to the wind, a large cockpit, good access to all ropes and to the dingy, nice interiour, many very well-thought-out details, ...

This is why I'm really interested to get the boat ballanced.

Jochen

[sf37]

Jan 15, 2014 7:30:26 GMT electricmonk said:

Without sailing with you its always going to be difficult to know exactly what is going on here. I had the SO37 with a shoal keel and in-mast mainsail. It was a very easy boat to sail well, nervous? no - but it would give clear signals that you were "out side its envelope" - signals similar to those you describe. I quickly came to the conclusion that it is a 20/20 boat - defy that at your own risk. If you want to sail with the side decks awash you will have your hands full. We regularly sailed it to windward in over 30 knots with no issues, perfectly balances and no weather helm.

Rig set-up is critical and the genoa driven sailplan needs careful reefing to produce rudder balance and speed but once you have found the sweet spot its OK.

You will find other comments I have made about the shoal keel/in-mast combination on the forum somewhere - in my opinion it makes the boat slower but if you keep within the envelope its a great boat.

Hello electricmonk,

I really like your comment that really encourages me that is not the boat that is nervous but that it is more a handling or outfitting problem.

Just one question: What do you mean with 20/20 boat?

Jochen

[electricmonk]

It will be fastest if you reef at either 20 knots of wind or 20 deg of heel which ever occurs first, in other words it likes to be sailed "upright" (ish) with well set and trimmed sails. We found the hull to be so slippery that we did nt take too much notice of tides - its a quick boat make no mistake.

[sf37]

Jan 16, 2014 20:36:32 GMT electricmonk said:

It will be fastest if you reef at either 20 knots of wind or 20 deg of heel which ever occurs first, in other words it likes to be sailed "upright" (ish) with well set and trimmed sails. We found the hull to be so slippery that we did nt take too much notice of tides - its a quick boat make no mistake.

Thanks for you explanation!

[twinco]

I purchsed a 10 years SF43 last year. She came direct out of the yard from an authorized Jeanneau dealer.
On the transfer leg from Italy to Spain in Medsea, we noticed a very strange rudder feeling with always a great dead bearing. The ship was very hard to keep on heading. 
When arrived I controlled in the rear hull departement where the Autopilot and Quadrants are and found that nearly all the screws and nuts were detached off or loose.
After fasten and renewing. The problem is gone. The ship keeps on heading and has exact helm control. I put this screw + nuts control on my yearly control list.
Saludos Klaus

[sf37]

Jan 18, 2014 22:30:51 GMT twinco said:

I purchsed a 10 years SF43 last year. She came direct out of the yard from an authorized Jeanneau dealer.
On the transfer leg from Italy to Spain in Medsea, we noticed a very strange rudder feeling with always a great dead bearing. The ship was very hard to keep on heading. 
When arrived I controlled in the rear hull departement where the Autopilot and Quadrants are and found that nearly all the screws and nuts were detached off or loose.
After fasten and renewing. The problem is gone. The ship keeps on heading and has exact helm control. I put this screw + nuts control on my yearly control list.
Saludos Klaus

Hello Klaus,

Actally, the steering in strong wind feels exactly like loose steering cables. Keeping your post in mind, I just visited my boat to check the clearance.
If I lock the steering wheel, I can turn the rudder only little (the rear edge of the rudder moves by approx. 10 mm) And I can shift the lowest point of the rudder by approx. 10 mm due to clearance of the bearing.

I guess that this clearance is OK?

Jochen