C&C 34 mainsail shape problem - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > Boat Builders Row > C & C
 Not a Member? 


Reply
 
LinkBack Thread Tools
  #1  
Old 02-17-2011
Junior Member
 
Join Date: Feb 2011
Posts: 12
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
ondinesail is on a distinguished road
C&C 34 mainsail shape problem

I race aboard a friend's C&C 34 (1978 vintage) and handle the mainsail. We are having a good deal of difficulty getting good mainsail shape. Both genoas severely backwind the first 4-5 feet of the mainsail in just about any wind speed. The backwind runs pretty much from tack to head. We get good flow over the aft half of the sail and the leach tell tales look right. The sail does not look blown out and the material is in good shape. The genoa carts are located conventionally. If we run the mainsail cart well to windward the sail eventually fills out a bit more but we just heel the boat and reduce drive. I can never get a decent looking luff when we are on the wind. Frustrating to sail with bad trim when the boat responds to trim so nicely. I feel there must be something we are missing in the rig set up or sail handling, but I am out of ideas. Perhaps these rigs were meant to be sailed with mast bend and the sail was cut anticipating that? Anyway. would welcome any experience others may have.
Reply With Quote Share with Facebook
  #2  
Old 02-18-2011
ASA and PSIA Instructor
 
Join Date: Apr 2000
Posts: 3,374
Thanks: 6
Thanked 14 Times in 14 Posts
Rep Power: 15
sailingfool will become famous soon enough
I'll throw in 10 cents here.

If the breeze is up, say 12 apparent or more, partial backwind of the main is a go fast trim condition and not a concern. There is too much wind coming thru the slot not to affect the main.

I lighter winds, if your main is being backwinded, somenthing is off. Assuming the genoa turning block is in the right location
- Is the boom on centerline.
- Is the genoa draft at 50% or further forward.
- Is the jib sheet eased several inches

Thos are my guesses.
__________________
Certified...in several regards...
Reply With Quote Share with Facebook
  #3  
Old 02-18-2011
jackdale's Avatar
Senior Member
 
Join Date: Dec 2008
Location: Calgary, AB, Canada
Posts: 8,549
Thanks: 24
Thanked 20 Times in 19 Posts
Rep Power: 6
jackdale will become famous soon enough
More questions

Is the genoa fairlead car in the correct position? Not enough folks pay attention to this.
  • Does the genoa sheet "point" toward the middle of the luff? There may also be a longer strap to use as a guide.
  • Do all genoa tell tales break together?
  • Is the curve on the foot and leech of the sail similar?

As SF mentioned some backwinding is a go fast position.

Bottom line for racing - what is happening to your boat speed?
__________________
__________________
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
As I sail, I praise God, and care not. (Luke Foxe)
Reply With Quote Share with Facebook
  #4  
Old 02-18-2011
Faster's Avatar
Just another Moderator
 
Join Date: Sep 2005
Location: New Westminster, BC
Posts: 14,390
Thanks: 63
Thanked 160 Times in 157 Posts
Rep Power: 10
Faster has a spectacular aura about Faster has a spectacular aura about Faster has a spectacular aura about
Agree with these two.. sounds like perhaps the genoa cars are too far forward for the sail and the leech might be choked off?

As always, though, these kinds of things are tough to diagnose with being there or at least some pictures!
__________________
Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
Reply With Quote Share with Facebook
  #5  
Old 02-18-2011
zz4gta's Avatar
I don't discuss my member
 
Join Date: Aug 2007
Location: Chesapeake Bay
Posts: 2,396
Thanks: 0
Thanked 15 Times in 15 Posts
Rep Power: 7
zz4gta is on a distinguished road
Need some pictures. How much of the main is back winded percentage wise? If it gets to the 50% 'line', move the jib car back, sheet on the main, and drop the traveler a bit. This is after you've shortened the forestay, have applied max backstay and outhaul. This should be in moderate to heavy air. How far away is the leech and the foot of the genoa from the spreader tip and chainplate respectively?

If it's happening in light air, then either something is definitely wrong trim wise, or the sail is blown out. It's better to have a flatter main and a fuller headsail instead of the other way around.

Pictures...
__________________
Merit 25 # 764 "Audrey"
Reply With Quote Share with Facebook
  #6  
Old 02-20-2011
Junior Member
 
Join Date: Feb 2011
Posts: 12
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
ondinesail is on a distinguished road
Follow-up on the trim problem

Ok. A lot of questions. We have tried moving the genoa carts. Naturally, it gets worse if we move the cart forward, though we tried this too. When it is properly positioned on the break of the genoa (on line from clew to centerline of luff) we still see about 30% of the main backwinded. Cart tracks are in what appears to be the original location for this boat - pretty well inboard near the cabin top. So I'm guessing location of the track is not the issue.

Do the tell tales break evenly. On the genoa, I believe so, but I will get back to you after next weekends race. I hadn't thought to look. What would that indicate re: backwinded main? The mainsail leech telltales all flow evenly.

This week we agreed to prebend with the baby stay and then backstay tension - again no wind to try this idea.

Last week we released tension in the genoa leach to add curvature. Had no noticeable impact on main shape.

We are probably trimming the genoa to about 3-4" off the spreader. I haven't noted where the foot falls relative to the chainplate - likely pretty tight when we are trying to point. I am not certain where max draft on the genoa is falling. Assuming we are not over trimming (and I think we are some but lets assume) what are the impacts of these items on the mainsail luffing?

Outhaul has been futzed with - full flat in anything over about 10kn. I would prefer the main be trimmed midships, but to fill luffing, my friend asks me to trim main to windward. I feel this creates more heel than drive but I am the trimmer - right.

I just noticed that the aft end of the boom droops below parallel. I was told this is normal for the boat as it adds sail area that isn't counted in the PHRF rating. Can this be? I'm thinking the boom weight may be distorting the sail shape some. Was the boat designed to have the mast canted forward then backstay tensioned to level boom?

Pictures - its not my boat and I really like sailing with these guys. I don't want to make myself unwelcome. But if I am gonna be on the main, I'd like to quietly solve this problem. So don't get frustrated if there are no pictures.

Boat speed is competitive. We are coming in second consistently. But to get a first we need to shave 2.5 minutes a mile on the number 1 boat.

No one has addressed the crux of this question though. Did the 1978 C&C 34 sail with a big back wind in its mainsail luff in most conditions? Is there something about this boat's intended set up that we don't know.
Reply With Quote Share with Facebook
  #7  
Old 02-20-2011
Faster's Avatar
Just another Moderator
 
Join Date: Sep 2005
Location: New Westminster, BC
Posts: 14,390
Thanks: 63
Thanked 160 Times in 157 Posts
Rep Power: 10
Faster has a spectacular aura about Faster has a spectacular aura about Faster has a spectacular aura about
From your descriptions (eg distance from spreaders, experimenting with lead car positions, etc) it sounds like you're not doing anything terribly wrong...

Some mast bend should help.. is the mast inverted now? ie reverse bend? or is it dead straight? Are the symptoms the same on either tack?

I think you're right that it's a mistake to be overtrimming the main to try to deal with this backwinding. It's sounding more and more like the main's simply toast.

And you're still competitive! That's great... I think for now I'd just trim to boat speed, grind on the cunningham, keep the leech driving and doing the best you can with the genoa. With subtlety, lean on your skipper to check out a new main....
__________________
Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
Reply With Quote Share with Facebook
  #8  
Old 02-21-2011
zz4gta's Avatar
I don't discuss my member
 
Join Date: Aug 2007
Location: Chesapeake Bay
Posts: 2,396
Thanks: 0
Thanked 15 Times in 15 Posts
Rep Power: 7
zz4gta is on a distinguished road
30% backwind is no big deal. Add some halyard, add cunni, and live with it. 30% backwinded is fast, but much more than that, and it's added drag.

2.5 minutes a mile is a lot. Are you playing follow the leader still? Or are you splitting tacks w/ the ringer? How competative is your fleet?

And the more important thing than the main sail, is that you don't have a relationship with skipper that allows open conversation and critizism to help make the boat faster. For instance, I posted pictures online from a regatta where I couldn't point, 5 pages of specific suggestions later, the boats points great and we're racing a lot better.

Explain to him/her that you want to take some pics and post them on a sailing forum to help with your trim. Tell him it's to make you better (not b/c you think his sail is crap). Also, start to ask questions like "the sail looks pretty good, how old is it?" If he comes back with >5 years.... you know the reality he doesn't want to accept.

Boom and traveler relationship. Assuming a close hauled course, the boom should be on centerline. Trim so the tell tails all flow aft except for the top one. That should break about 50% of the time. After you get that, check the position of the boom! Is it on center? If not, move the traveler up to windward to put the boom on c/l. In lighter air the trav will be to windward most of the time. The sheet will be very eased. Moderate air the sheet will be hard on and the traveler will be centered. Heavy air, the traveler drops down below center as does the boom, losing pointing and adding drag from a luffing sail.

If the boom end 'sags' (points down instead of horizontal) no big deal. You see that a lot on boats.
__________________
Merit 25 # 764 "Audrey"
Reply With Quote Share with Facebook
  #9  
Old 02-21-2011
ASA and PSIA Instructor
 
Join Date: Apr 2000
Posts: 3,374
Thanks: 6
Thanked 14 Times in 14 Posts
Rep Power: 15
sailingfool will become famous soon enough
Do the tell tales break evenly. On the genoa, I believe so, but I will get back to you after next weekends race.
You should monitor for an even break frequently and evenly, how the teeltales bereak is the proper way to judge your genoa car position.

This week we agreed to prebend with the baby stay and then backstay tension - again no wind to try this idea.
The baby stay is to prevent pumping in a heavy sea...take it off and put it away. Setup pre-bend without it. You might get another see of eyes to look over your rig setup.

Last week we released tension in the genoa leach to add curvature. Had no noticeable impact on main shape.
Are you talking about the leech line or the genoa sheet? This seems a pretty confused statement

We are probably trimming the genoa to about 3-4" off the spreader. I haven't noted where the foot falls relative to the chainplate - likely pretty tight when we are trying to point. I am not certain where max draft on the genoa is falling. Assuming we are not over trimming (and I think we are some but lets assume) what are the impacts of these items on the mainsail luffing?
Overtimming will increase backwind in the main, as you make the slot narrower. Your spreader sounds not two tight, 2" off was my target on a similar boat. That you dont know the location of the genoa draft is bad, as draft aft will do a numbe rof negative things including increasing backwind in the main.

Outhaul has been futzed with - full flat in anything over about 10kn. I would prefer the main be trimmed midships, but to fill luffing, my friend asks me to trim main to windward. I feel this creates more heel than drive but I am the trimmer - right.
Boom should never be above centerline.

I just noticed that the aft end of the boom droops below parallel. I was told this is normal for the boat as it adds sail area that isn't counted in the PHRF rating. Can this be?
yes, but the main halyard not being full hoist is also a likely explanation.
I'm thinking the boom weight may be distorting the sail shape some.
Only if the sail has no shape to begin with...

Was the boat designed to have the mast canted forward then backstay tensioned to level boom?
No.

Pictures - its not my boat and I really like sailing with these guys. I don't want to make myself unwelcome. But if I am gonna be on the main, I'd like to quietly solve this problem. So don't get frustrated if there are no pictures.

Boat speed is competitive. We are coming in second consistently. But to get a first we need to shave 2.5 minutes a mile on the number 1 boat.
Sounds like most of the other boats have greater trim problems..

No one has addressed the crux of this question though. Did the 1978 C&C 34 sail with a big back wind in its mainsail luff in most conditions? Is there something about this boat's intended set up that we don't know.
Posters have told you no. You should try this subject ont he C&C discussion group where other 34 owners can give you comparable info. Happy trimming...
__________________
Certified...in several regards...

Last edited by sailingfool; 02-21-2011 at 08:38 AM.
Reply With Quote Share with Facebook
  #10  
Old 02-21-2011
Junior Member
 
Join Date: Feb 2011
Posts: 12
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
ondinesail is on a distinguished road
Thanks

Thank you. Looks like I have plenty to think about for this weekends race. Appreciate you all looking at my problem.
Cheers
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Topping Lift and Sail Shape NCC320 General Discussion (sailing related) 13 02-24-2011 10:25 AM
Full Keel Rudder's Shape? Beetle General Discussion (sailing related) 3 11-24-2010 10:16 AM
Mainsail shape Gorlog Gear & Maintenance 11 06-25-2010 12:26 PM
Main Sail Shape newuser Learning to Sail 5 10-30-2004 03:45 PM
Reading the Shape of the Wind Carol Cronin Racing Articles 0 07-18-2002 08:00 PM


All times are GMT -4. The time now is 09:54 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012