mast rake and weather helm

  I've heard different things about mast rake aft.  Doesn't raking the mast aft (eg with forestay extender) decrease your weather helm?  Does tightening the shrouds (shortening them) also decrease weather helm?  I have  snug rig cut sails and seem to have more forward rake on the mast than I want. 28'7'' with no forward tension on the mast.  My shrouds also have more than 6" play and I seem to have more weather helm than I would like going to windward, all things being adjusted with sails, crew weight and position and main eased some if need,etc., to decrease weather helm.  Would shortening my shrouds take care of all of this and get better rake aft and more shroud tension? I appreciate any insights and experiences.

For the snug rig, according to the tuning guide, you should be at 28'4-5" with a forestay tension of about 90 lbs.  You achieve this by adjusting the forestay tang turnbuckle and changing the position of the chainplate shroud attachment.
You should not need to actually shorten the shouds but you may need to add a forestay extension.

I second the advice from Glenn, it may take a few iterations but get the rake and tension as close to the guide as possible and then mark the settings with a sharpie.  You shouldn’t have to readjust very often, just check the rake each time you set up the rig.  Also, when you experience weather helm going up wind try pulling up the centerboard a bit (a few inches at a time).  This does not actually raise the board but shifts it aft changing balance of the boat in favor of less helm.
Mike Mandell
FS #5010

The one question I have pertaining to that is what is the sequence in setting up your boat which you follow to arrive at the proper rake distance(mast head to mid stern edge of deck eg. 28'4'') and getting the other numbers?  Is this the  distance  you have with the mast pushed back with little tension initially on the forestay and the shrouds where you think they should be set in their fittings?  When do you adjust the forestay tension with the toggle and/or an extension adjuster plate which I have, and when are the shrouds with their fittings adjusted in this process?  I know that I'm supposed to have about 1-1.5" of mast play fore and aft with a snug rig with that amount of rake 28'4-5.5" and about 6" of shroud play.  What kind of tension guage do you use to measure the forestay tension.  I've heard one doesn't use the Loos guages.  Thanks again.

This is a good question and for many new Scot owners a puzzling problem. I hope that my answer will help you get close to the ideal setting. It does not have to be exact. There maybe others who have different ideas or a different procedure so dont think there is only one way, per se.
To achieve the ideal setting of 28' 4.5  for a snugg rig takes a bit of trial and error, give and take. There are several potential variables at play that make getting the correct setting different from boat to boat.  The first variable is the toggle which holds the wire in place and which is located under the bow. No two boats have the exact toogle "setting."  You have to play with it. Tighten it up or let it out but once you get it right then you will be in good shape going forward. It helps to have an assistant to help you do this. You may have to adjust the side stays, the forestay etc... Keep at it,  keep measuring and keep adjusting until you get there. 
Other factors that may effect your measurement. If you have new running rigging, the rigging will stretch with use; the rigging will strentch or expand due to heat so you have to adjust something to take up this "new" slack. This could be done at the forestay, to me the easiest one to adjust or it could result in changing the toogle under the bow. You may have to do a little of both.
Also make sure that you measure your boat, that is measure the rake on level ground. That 1.5 inches of play in the mast will make a difference if you dont measure the rake on a level surface. Also take into account the clip distance used on your measuring tape.
I use the Loos gauge and shoot for around 100 to 120 lbs of weight tension on the forestay; some sailors may shoot for more and others a little less.  I think 6 inches of play in the side stays is too much for a snug rigg. I think it should be around 3.
Dont be afraid to expertiment. Sometimes you may want more tension and more rake on the mast and others less.
Finally, dont forget what the object of all the tuning is. A neutral helm that powers up when necessary and points well too. Other factors like crew weight, crew placement and sail trim will also effect your boats performance.
Best of luck