|Topic Review (Newest First)|
|12-20-2006 02:54 PM|
|12-20-2006 02:45 PM|
Anybody else having trouble getting to the Arvel Gentry site (www.arvelgentry.com)? My browser times out.
|12-20-2006 02:13 PM|
Many things will prevent a boat from properly 'pointing up': rig tension, sail condition, sail SHAPE, rudder/helm balance, etc.
If the rigging isnt properly tuned/ttensioned, the forestay maybe too slack and will sag off to leeward with the result is that the boat will heel way over but not go 'anywhere' and you start to develop a LOT of 'weather helm' thus additionally 'putting on the brakes'.
All jibs/genoas are specially cut/curved on their luff so that the curve of the luff matches the *normal* sag of the forestay; most sailmakers 'assume' that the tension on the forestay is set up/tensioned to somewhere between 12-15% of the ultimate breaking strength of the wire. A rigging tension gage is needed to precisely get to those values ... but isnt needed unless you are racing, etc. .... You can use your *Mark-I eyeball* to get close to these 'sag' values with the following method: take your jib/genoa and lay it out on a CLEAN flat surface, make a 'double fold' (pleate) in the sail about 2ft back from and parallel to the luff (this will allow the sail to lay FLAT on the ground, etc.), remove any 'creases' etc. that inadvertantly form as you want the sail smooth and FLAT in the section 2ft aft the luff. Have an assistant hold the head connection firmly as you run a string from the head down to the tack connection .... observe (and remember) the 'curve' that the luff makes when its FLAT, then measure the point of 'greatest distance' between the string and the luff. Get some adhesive backed fabric (draft stripe material .... from a sail makers supply works best) and place a small strip at the *same* measurement BACK from the luff. This measurement and shape that you 'remember' will now allow you to get (SEE) the proper forestay tension, the amount of forestay 'sag' to MATCH the curve in the luff of the sail .... as a 'basic setting' for *12-15kts*. of apparent wind. You then adjust the backstay tension to change the tension in the forestay (while underway) to get the 'basic setting' (curve) that matches the sail (for 12-15kts.).
To point even higher (but slightly 'slower') you can increase the backstay tension so that the forestay 'sag' becomes even less.
Also remember that when beating, etc. the more you 'load' a sail by straining the sheet on a winch the more additional forestay sag will occur .... needing either MORE backstay tension or LESS sheet tension to keep that luff curve 'reasonable'. That little 'strip' that you put behind the luff will help you visualize how much or how little luff sag there is. The sail will be at its maximum/optimal luff shape when that 'curve' matches what the sailmaker originally put in there.
Other: to help point higher (or lower with speed) you should also consider to apply hard halyard tension which will change of the 'shape' of the sail so that the point of where the draft is the greatest will be more-forward in the sail. More halyard tension in higher wind ranges and less tension in lower winds.
Obviously, there are many other such 'adjustments' for proper "sail shaping" but from what you describe, the above may radically change the way your boat 'points'. There are many books and 'articles' on sail-trim and shaping. Probably the 'easiest' is a guide written by Don Guillette (forget the name of the book but his name will allow you to do a 'websearch'), probably the most definitive and 'technical' (also 'free') is an accumulation of magazine articles by the the famous aerodynamicist Arvel Gentry (www.arvelgentry.com) .... go to that website, then go to 'magazine articles' then download:
Checking Trim on the Wind, November 1973
Achieving Proper Balance, December 1973
Sailing to Windward, January 1974
Are You at Optimum Trim?, March 1974
... these are 'sequential' from one large single article .... that set the sailing world 'on its ear' in the early 1970s. He's the one who 'debunked' the 'slot-effect' and other incorrect and still popular 'mysticisms' of how sails really work, etc. If they seem too technical, just read them several times over and over ... until you say "holy ****, this is incredible".
Hope this helps. ;-)
|11-04-2006 04:10 PM|
I'd start with a book on sail trim, or calling a local loft and asking when you could stop by to talk to someone. (And if they offer to come visit your boat, by all means say yes!)
If your sails are 11 years old, I would expect that unless they were stored indoors for ten years, they're shot. When you lay hands on them, are they nice and smooth? Feel like commerical bed sheets? Smoother? Or do they have a shiny plastic coating still on them?
Usually by the time the plastic coating is gone, they have lost shape. Shortly after that, they will be blown out, usually around the same time they feel like you could use them if for bed sheets if you really had to.
But blown out sails alone may not be the problem. Assuming you have the original rudder on the boat (sometimes they get replaced incorrectly) and assuming the bottom is reasonably clean (not hauling around mussel farms), every boat still has a center of effort, a pivot point roughly around the center of the boat. The boat acts like a windvane. Apply pressure behind the pivot point, and it turns one way. Apply pressure in front of the pivot point, and it turns the other way.
If you have too much sail area on the wrong side of the pivot point, you will always be turning away from the wind, or at least, not pointing well into it.
This can come from having the wrong rake (tilt angle) on the mast. That can come from the rigging (forestay/backstay) not being tensioned or sized correctly. Or having the mast located in the wrong position, if there's no fixed plate to secure the bottom of it. Or, having the wrong sails (too much, too little, too blown out) as well as having the sheets led to the wrong position.
If that sounds awfully vague and complicated...yeah, it can be.
So really...getting someone from the loft out on your boat might be the fastest way to go over this all. That's easier now in the slack season, and with 11 year old sails...I think you'll be AMAZED at how much better the boat does with new ones. The extra teaching that the loft can do, is often worth the extra cost of dealing locally.
Otherwise, ask around, maybe your dockmaster or someone at your local chandlery can connect you to someone more experienced locally, who'll gladly come out and take a look for the price of lunch or a couple of hours on the water.
|11-04-2006 01:23 PM|
Originally Posted by wumhenry
Secondly, how close do you trim the jib and in particular the main? A common guideline for trimming a jib with an inboard track is 2 inches off the spreader tip, I'm not sure how that translates for toerail trim- never trimmed a closehauled jib to a toerail in 30 years,,,. The main needs to be trimmed to just before the leech telltails break, the top one should be lifting. Mainsail trim is a bit of an art, you need to use the traveller (if you don't have one, thats another couple of degrees you lose) and sheet together, a lengthy subject you should find in available tuning guides.
If your rigging is holding the mast straight, it ain't part of your problem. You can judge that by whether there's much slack in the leeward rigging when closehauled in a moderate breeze. If there is noticable slack, tighten 'em up. Theres no way tired rigging should contribute to poor performance (up until it drops the mast on you.)
If I were you, I'd try to get an expereinced 29.9 owner to go out with you once.
|11-04-2006 01:20 PM|
|captlar||The reference to rigging refers to how well the boat is "tuned". Example - look to see if the forestay has a sag when going upwind. If the rig is too loose, performance will suffer. Get someone in the know to go for a sail. I am surprised there are no inner tracks or fixed blocks to allow you to bring the jib in. Best guess - new sails make a HUGE difference (10 degrees). Have a local sailmaker take a look at your existing. If money is tight, get the jib first.|
|11-04-2006 10:55 AM|
Re: Yahoo forum
Wunhenry! Good to see a freindly name. I have been unable to reply or post on the Yahoo forum. Perhaps you can post a message for me telling all that I have been unable to reply to their messages, (one was a lengthy reply to Hillbridge re: the cabin sole refinshing job that he had inquried about. I typed 4 paragraphs, the message went off to oblivion). I appreciate your letting everyone know why I have dissapeared. Also, I would strongly suggest that we consider moving the forum d/t the high degree of unreliablity on Yahoo.
|11-04-2006 10:04 AM|
Thanks for answering, dog.
The fairleads are on a track on the toerail. I don't see any evidence that they were ever located inboard.
Standing rigging has not been inspected since I bought the boat but will be sometime this winter.
AFAIK, the boat wasn't raced, but the PO put a lot of cruising miles on it.
AFAIK, the sails were covered when furled. The headsail is roller-furled with a sunbrella strip on the leech.
The boat was built in 1981.
I don't know how old the standing rigging is.
Originally Posted by sailingdog
|11-04-2006 06:58 AM|
The sails could definitely be the problem. Other things that could be part of the problem—where are your genoa/jib fairleads located. The further outboard they are, the less high you can point as a general rule. Has the standing rigging been inspected and adjusted since you bought the boat. A badly adjusted rig can have a lot to do with pointing problems.
I'd look at those three areas first, before doing anything else. The sails may be shot, depending on how hard the boat was sailed, and how the sails were stored and used. 11 summers under the Chesapeake sun without a sail cover could definitely cause some UV damage to the sails. If the boat was raced, the sails could definitely be stretched out of shape—same with the rigging. You don't say how old the boat is, or how old the rigging is. The fairleads, IMHO, are probably the least likely and least expensive cause to fix, unless a PO moved the jib fairlead tracks.
|11-04-2006 01:39 AM|
Problem pointing up
The Bristol 29.9 that I bought this July doesn't point up very well. I haven't measured the angle exactly, but it is certainly more than 45 degrees off the wind when close-hauled, which becomes evident when tacking -- I have to turn through 100 degrees or more.
What could cause this? I'm sure it's not an inherent design flaw, because other owners of 29.9 have assured me they don't have the same problem.
Could it be due to blownout sails? The set that came with the boat are 11 years old.