mast step

[Marshall Tonner]

I have an 89 C34 with keel stepped mast. Will moving the mast step forward offset weather helm? It is now set all the way aft. Thanks, Marsh.

[PAUL T.]

Marshall....... I have never heard of anybody changing the position of the Mays step on a CAT 34.    How would the mast line up with the hole in the deck?   The Catalina 34 is a beautifully balanced boat. If you have a problem with weather helm you should check to see if your mast is tuned properly, or maybe you have sail trim issues........ GOOD LUCK......PAUL

[Ron Hill]

Marsh : I don't think you can move the mast that far forward that you could appreciably change the weather helm.  
You say "all the way aft".  You want to make sure that there is a little space between the mast and the deck hole.  It's not good to have the mast exerting pressure against that deck.  Close and touching is OK, just not pressure.
If you want to get the weather helm under control you should install a back stay adjuster or convert your existing rudder to an elliptical rudder.  The simplest is a back stay adjuster.  The one I made is in Projects on this site.  Easy to do, low cost and works great.  
The rudder extension is something you can do later.  You'll see my rudder "overhaul" in an up coming issue of the Mainsheet.  

[Stu Jackson]

Marshall

It won't make any difference.  Our masts are basically telephone poles.  There has been much discussion over the years about mast rake and bend, which is, to me, all nonsense (for our boats - does apply on other boats).

The cause of weather helm on Catalina 34s is too much wind with too much mainsail.  I personally believe that is the ONLY reason.  Too many people reef their jibs first and mainsails second, which is backwards.

Moving your mast won't make a difference.

Moving to reef your mainsail will make that difference.

[Ted Pounds]

Moving the mast step forward will rake the mast aft unless you want to do all the structural work to move the partners (the hole where it goes through the deck) forward.  Raking the mast aft increases weather helm.  Stu is right on, the best thing to do is reef.   Changing the rudder will help  (though I guess that's a $2000 mod these days), but above about 17 knots wind you should still reef to keep the boat on her feet.  Too much heel means too much side slip and leeway.  Also keep in mind you always want some weather helm going up wind. You should have about 3 to 5 degrees of weather rudder angle (per Dennis Conner).  That allows the rudder to provide positive (upwind) lift in addition to the keel.  If you have weather helm while reaching or running you need to ease the main (likely with the traveler) till it goes away.  As I recall there was a previous discussion on this board (try a search) about tightening the forestay to change the rake slightly forward.  That may be something to look into.

[Ted Pounds]

Try this reference:

http://c34ia.org/phpbb/viewtopic.php?t=1162&highlight=mast+rake

I got it by searching on "mast rake"

[ross99]

Seeing this post raised a similar question with me.   I bought my  1988 C-34 about a year ago, and constantly experience weather helm in even moderate winds.  I have about 6-8 inches of "rake" when I hang a weight on the main halyard, and assumed that there is too much rake causing the weather helm.

I have tried loosening the backstay and tightening the forestay and similarly adjust the lower shrouds.  Still, the mast touches the aft end of the hole where it passes thru the cabin top, and I have only slightly reduced the amount of rake.  I have assumed that getting it "centered"  is the right place for the mast to be, but I can't figure how it'll ever get there with the existing rig.  The backstay turnbuckle is out about as far as it will go!  

I believe the rig is original to the boat, but can't imagine the mast has been riding against the aft end of the mast hole all these years...   any ideas out there??

[mike lofstrom]

Stu's Right.  Changing the rake of the mast will not change the amount of weather helm you are experiencing, but there are a number of other things you can do to keep the boat under control.  The first thing is heeling angle.  When a sailboat sits in the water without any heeling at all, the water is distributed symmetrically around the hull.  As the boat heels, this symmetry is disturbed.  The Symmetrical shape becomes a banana.  The further the boat heels, the more the banana shape.  The Boat is not flexing into this shape, It presents this shape to the water as a result of the heeling.  This is particularly true of fin keel designs like Catalina's.  The banana shape then tries to drive the boat to weather.  The other factor here is the rudder's effectiveness becomes muted by the fact the rudder is no longer vertical.  As the boat heels, the rudder does less and less to counter the weather helm and steer the boat, and instead works to lift the transom.  This then makes the problem worse.  (This usually results in a rudder stall and subsequent roundup!)

The key to all of this is to limit the amount of heeling that the boat does.  If you have a properly designed Cunningham, it should be pulled in when going to weather in a stiff breeze.  The will work to pull the draft of the main forward and move the center of effort forward.  If your Boat has an adjustable back stay, this can be tightened as well to allow twist in the top of the main.  ( These boats have a pretty stiff mast though.)As the wind builds, the next thing is to pull in the first Reef.  Again, the key is to flatten the foot of the main.  If the reef is sloppy and allows to much draft, the center of effort can actually move aft and is some cases can make the problem worse.  A well designed reefing system will really work to flatten the main as it reduces sail area.  Easing the main sheet will also allow the top of the main to twist off to leeward, and will ease some of the heeling force in the upper part of the rig.  Incidentally, there is nothing wrong with having some amount of back winding in the main from the close hauled jib while working to weather.  The boat is actually faster if it is standing up and the jib and main are really driving than it is heeled over and dragging the rudder through the water sideways.  ( you can verify this on your Knot meter)

Sail condition is also a big factor.  If your main is old, it is probably getting pretty baggy.  It may look fine and have good stitching, but it will probably stretch way to much in a stiff breeze.  As it stretches, the draft will increase, and the CE will invariably move aft.  You would be amazed at how much difference a well cut main can do for weather helm on one of these boats.  

I'm sure there are plenty of other opinions on this subject, these are  mine based on 15 or so years of sailing on SF bay. (Sometimes very overpowered for the conditions!)  

FYI, An excellent book on the subject is Sail Power by Wallace Ross.  It covers all of these items in great detail.

Mike

[Ted Pounds]

Mike,

I agree with all you said except your first statement that rake will not affect weather helm.  Rake, especially in the amound Ross is talking about, will affect weather helm.  As the main is rotated aft (through rake) the center of effort moves aft and weather helm increases.

Ross,

You may be able to add some sort of "link" to your backstay to increase its length.  Then you need to shorten your forestay by a similar amount.  That may require a new forestay.   Your mast shouldn't be on the aft end of the partners.  Mine is basically centered in the partners and I suspect most other keel steped masts are too.

[mike lofstrom]

Ted:  I probably should not have said that there would be no impact on weather helm due to mast rake.  ( Too much coffee yesterday! ) It will definitely have an impact, but it is probably not going to be the silver bullet that Ross is looking for.  Here is a little mathematical rationale to explain:

The mast on the c34 is about 50 ft from the step to the top of the rig.  The partners are about 7 feet up from the step.  Ross stated that he has 6-8 inches of rake in the mast, but I'm not sure how his boat sits in the water.  ( He could have a 12 foot Boston whaler in davits on the transom )  Anyway, assuming the mast is sitting against the aft partner, and it needs to move  1/2 inch forward to get it centered, this would translate to a change of about 3.5 inches at the mast head.  Since the CE of the main is about 1/3 of the way up from the foot of the main, and the foot of the main is up about 11 feet from the step, the CE ends up about 24 feet from the step when the main is not reefed.  

Where am I going with all of this?  Centering the mast in the partners is only going to move the CE of the Main about 1-2 inches forward.  it will be noticeable, but it will not be huge.  

I agree though,  The mast should be moved forward so it is not sitting on the aft partner, and it will have some effect on the weather helm if it is raked to far aft.

[ross99]

Mike, Ted, this has been really helpful.  The one piece of the math I still can't figure is -- were I to try to get that 1/2 inch forward movement at the partners, how much increase in the backstay/decrease in forestay length would be required?  If I'd kept my my High School trig book maybe I could figure it out, but it's long gone!.

[Stu Jackson]

Ross

That 1/2 inch wouldn't make a difference in the length of your fore or back stays, regardless of trig, simply because you could easily make up the difference with your turnbuckles.

If you move the base of the mast at the keel and/or at the partners that 1/2 inch, EITHER the top of the mast will stay the same (so you get the rake - big deal, right?) OR you adjust the turnbuckles so that the top of the mast also moves forward: loosen the backstay, tighten the forestay.  The amount you have to loosen and tighten them is simply one of those forgettable things like the sin, tan or cos of the angle (of dangle :)  )  !!!!

No need to make it any harder than it is.  (Which is why I've avoided cosec, cotan and all the rest...)

[Ted Pounds]

Stu,

Ross said further up in this thread he is 'at the end of his rope' as far as backstay adjustment goes.  Thats why he needs to figure out how much to extend it.

Ross,
If Mike is right about moving the masthead 3.5 inches then I wwould guess about 3 more inches on the backstay would do it and give you some adjustment to play with.  I'm in Maui right now (it's a tough job, but someone has to do it   ) but when I get home I'll try to work out the math.  Or maybe I'll have my daughter do it.  She got an A+ in honors trig last year.

[Marshall Tonner]

Thanks for all the response.My understanding is that some forward movement of the mast will be a little help which was all I'm after. I always reef fairly early and generally fly only a 110 jib. Now that the Canadian dollar is worth a little something I'll be replacing the rudder next spring.

[John Gardner]

Movement of of the top of the mast forward will translate into a much smaller amount of additional backstay length.  Regardless, you can always get some additional length by adding an appropriate turnbuckle toggle, or even two, between the stay and the turnbuckle.

John