# Back Stay Adjustments



## downeast450 (Jan 16, 2008)

Well this is the year I start paying closer attention to all the trim adjustments my Islander 28 offers. I have been enjoying this boat just sailing it with the rig trimmed vertical. After reading quite a bit about the subtleties of adjusting sail trim I am anxious to play. One thing that bothers me is what happens to the hull when I increase the tension on the fore stay by tightening the back stay. I already notice a sticking head door when I have things tight. I have hank on head sails. Should I lessen the head stay tension in anticipation of making back stay adjustments? How do I have a slackened head stay and put some bend in the mast when I am tuning the rig? Do I slacken things while on the mooring and set the tension when heading out? I have never made any adjustments to the rig during the season once I was satisfied it was "safe". I have never raced the boat but would like to.


----------



## sailingdog (Mar 19, 2006)

You might want to inspect the deck very thoroughly, since if the backstay adjustment is causing the head door to bind, chances are you've got some weakness in the deck structure, or the interior structure of the boat. Tightening the backstay shouldn't be causing the head door to bind unless something is out of whack to begin with.

If the mast is deck-stepped, then the bulkhead or compression post that transfers the forces down to the keel could also be a problem.


----------



## Faster (Sep 13, 2005)

With a masthead rig the primary purpose of the backstay adjustment is to apply tension to the headstay. Mast bend control of such a rig is difficult without a very powerful (read hydraulic) backstay adjuster combined with checkstays.
The Islander 28 is deck stepped, I think, so it's possible that you're compressing the post/bulkhead enough to make the doors stick.... but generally it is not terribly unusual to be able to tell that the boat is flexing under the backstay/rig tension. Making it a habit to "relax" the boat between sails is good practice. This is where an adjustable backstay is a little "kinder" to the boat than a permanently cranked on fixed backstay, which cannot easily be eased.

Tuning some bend into the mast is possible if you have forward and aft lowers for more or less permanent bend, or a babystay with some power and inline shrouds. If you're trying to set this up, be sure your main is cut to take advantage of mast bend.


----------



## artbyjody (Jan 4, 2008)

I would have to ask that if a recent survey has been made. Considering your model of boat - it seems perhaps the compression and the fall out implications - indicate you have delaminiation / rot under the deck where the mast rests at or you have rot at the base where the cabin work meets the flooring (which acts as framing) may need to be addressed. 

A competent rigger should be the first call (if visual indications (meaning is there darker variations of wood in the cabin where it meets the area where the mast is located) and basic hammering around the deck to see if you get thuds...)... It is possible that you are over tensioning the backstay. Most hydraulic backstay labels do state only pump until 2-3 inches of the threads is exposed when doing the max tightening (error on the three). However, you could have an issue where the forestay is actually too tight. Common if you have it replaced or installed a new furler etc...

Just some thoughts...


----------



## paulk (Jun 2, 2000)

Islanders are not noted for the overly rigid layup schedules (pun intended) in their fiberglass. Cranking up the backstay so as to tighten the forestay for improved performance to windward will likely cause some "bananna-ing" in many boats. Our doors are surface mounted, so there's no frame for them to stick in, and so we perhaps simply don't notice it happening on our boat! Fiberglass skis bend too, many thousands of times, before they're considered too worn out to use. The trick is to not hit any trees or crank so hard on the backstay that the mast drives a hole in the bottom as the boat cracks in two.


----------



## Faster (Sep 13, 2005)

paulk said:


> ...Cranking up the backstay so as to tighten the forestay for improved performance to windward will likely cause some "bananna-ing" in many boats. .... The trick is to not hit any trees or crank so hard on the backstay that the mast drives a hole in the bottom as the boat cracks in two.


Indeed - as happened a few years back to Australia's AC boat...


----------



## downeast450 (Jan 16, 2008)

Thanks for all the good advice and observations. My boat came to me a year ago, on a mooring, in December, in Maine, by chance, for taking responsibility for it. It had been in storage, outside for 20 years and does have significant gell coat crazing on deck. It is a 1977 hull. I have done some work in it. I like to work on boats. I have never raced one. The floor frames are glass encapsulated wood and when I drilled into them they were definitely soft so there may be a degree of compression under the mast's compression post but not enough to show any deformation that is obvious. I did notice that the head door was binding a little in the corner closest to the mast step. The deck is sound.

As I play with this boat's rig adjustments I am wondering about where the "slack" comes from as any of the shrouds get tightened. Deforming the hull is certainly one possibility. Where would the changes in the length of the stays come from if the mast were sitting on an absolutely rigid surface? Is it all stretch in the stays? Does it force a bow into the mast as the stays get shorter? I do understand that there is quite a range of tension that will keep the mast in place. Is it that range that gets shifted as a trimmer changes tensions to gain an advantage by tightening the backstay?

This boat came with a whisker pole, a spinnaker pole, two head sails and a symmetrical spinnaker, and the main. The sails are nearly new looking I think what use this boat got was primarily motoring with its A-4. I replaced that last March along with the control cables, the head, all the hoses and clamps and a halyard winch. It is a very responsive boat. It seems fast but I am not much of a judge of that. It jibes easily and seems to accelerate quickly. I am using it to teach my wife about sailing and adding some rig adjustments to gain a little performance this year will be fun.

Thanks again,

George


----------



## Faster (Sep 13, 2005)

Ideally, on most masthead rigs tensioning a standing rigging adjustment will mostly just transfer forces and tighten things up, eg preventing excessive sag of the headstay when you pull on an adjustable backstay. In some racing rigs, backstay tension can also compress the rig, causing mast bend (hopefully in the right direction) - but this takes some power and some adjustment of checkstays and/or runners to control and limit the bend - far beyond what you'll have on your Islander.

On a fractional rig, generally there's enough give in the rig that when the backstay is pulled on the mast bends - aft above the hounds (top of shrouds) and forward below, causing a smooth curve in the mast that helps flatten the main by pulling material forward. Also not applicable to your boat, of course.

Sounds like your boat's well set up for casual racing - you should have some fun with it. Enjoy!


----------



## downeast450 (Jan 16, 2008)

Faster,

Thank you for the explanation. That is what I surmised. I will take another look at the floor under the compression post and add a ss brace to the Keel if I find a reason for concern.

I like the term "casual racing". Ha! My lifetime sport has been marathon canoe racing and regardless of which venue two boats are competing in there is nothing "casual" about the focus. I do understand what you mean. I am blown away by the focus given to sailing to win. I hope that doesn't become important to me. I was a recreational canoeist before my first Nationals 40 years ago.. We will have fun.

George


----------



## Faster (Sep 13, 2005)

No worries, George

Anything you do to improve your situation re the compression post/mast step area should really be done with the rig removed... trying to shore something like this up under load is difficult to do properly.

Chances are, if there's not any visible problem on deck (no low spot, excessive stress cracking, etc) then what you're noticing on the sticky door is not of great concern, esp if it clears up when you release the load. Nevertheless it's something to keep an eye on, and to keep in mind the next time you haul out, and you might want to drop the stick (you'll need to inspect it at some point anyhow) and attend to any problems then.

In the meantime, tweak, trim, tension, and casually sail your way to the front of the fleet!


----------



## downeast450 (Jan 16, 2008)

Will Do!

Thanks again!

George


----------



## paulk (Jun 2, 2000)

P.S.
The fact that they might look relatively new or in good condition doesn't mean that dacron (or other) sails aren't blown out of shape. If you've been focused on powerboat racing (paddling), think of all the details that go into a top-performing paddle, and apply that to a surface area 500 times as big. Imagine a paddle that stretched and changed shape when you used it a few times, and which you could stretch and change to suit different conditions, and you start to get the idea.


----------

