Mast rake

bffatcat · Nov 14, 2009

depends on the boat beam has something to do with it

shemandr · Nov 14, 2009

Maybe you need to think of it like a balance point. The center of effort of the sail plan vs. the center of resistance of the hull. If its design is balanced than a small change can exert a notable difference. I'm not a Navel Architect so please don't kill me on the terms like last time I stepped into this arena.

rardiH36 · Nov 14, 2009

If it might be of help, the following is from the Mast Tuning section of Hunter's instruction manual for their early 1980's "Cherubini" Hunter line (seven models 22 - 37 ft):

"If your boat exhibits either lee helm or excessive weather helm, additional adjustments are indicated. A slight degree of weather helm (the tendency for the boat to round up into the wind when steering is released) is considered desirable. If weather helm is excessive, it can usually be corrected by raking the mast forward until proper balance is reached. If this does not quite achieve the balance you want, try storing additional weight aft (under the cockpit seat).

Lee helm (the tendency to fall off when steering is released) can usually be corrected by following procedures opposite those outlined for weather helm."

Recently I did rake my mast somewhat more forward from where it was. Since this was a "wonder if?" type of project, I wasn't assiduous enough to record before/after data like wind speed and point-of-sail and amount of sail flying vs how much effort to counter the weather helm. So I only have a perception of the change in performance which is in up to moderate wind, I seem to be able have less weather helm for the amount of sail out than I did before.

In strong wind however, my boat still has significant weather helm that sometimes needs almost full counter-rudder to maintain a heading when the wind is ripping and the boat is strongly healing because I have too much sail out ... (A situation which is frequent for me in SF Bay where winds can change from virtually nothing to almost gale force and then back again depending on location that happens by transitting as little as several hundred yard distance. Sometimes its just too much hassle to take in a reef only to shake it out again a few minutes later.)

Anyway, I'll leave the mast rake in its new position. Weather helm seems to be less and the adjustment didn't have any adverse affects that I have noticed.

Eventually, a new mainsail with its point of draft further forward than my existing weather-worn stretched out sail might also help weather helm a bit.

Ken13559 · Nov 14, 2009

Quoddy said:
When the mast is raked the CEO of the main being about 1/3 the way up the mast ...... ?

I suggest you hang those CEO :cussing:right up the mast top i.s.o. 1/3 way especially those from Wall Street.

Sam Salter · Nov 14, 2009

Not quite sure what the question is!
sam

Ray Bowles · Nov 14, 2009

If you are sailing a H260 water ballasted boat then it will exhibit a greater tenderness than a standard keeled sailboat. My 95 H26 was poor in all areas until we got very serious with mast tuning tensions and improved the headsail line lead system. This was solved with a 18" jib car system. Also if your roller furling (if equiped)is not foam equiped then when it is reefed it quickly becomes of little assistance when rolled in more than about 15 to 20%.
We used 2" of rake on our H26 after tuning the mast spec's to Hunters spec's with a Loos gauge. It was a totally different boat! Huge improvement in handling and speed! I ran 2" on my C22 and am presently running 8"s on my SJ23. Go figure. All these are factory suggested starting points in combination with mast tunning. You then modify from there.
I doubt my H26 would have shown any measureable difference with mast rake when reefed. Once the H26 was reefed and if the wind was above 18 to 20 knots you were simply a plastic stone skipping accross the waves. Throw in some wave size like an honest 3 foot and it was time for the boat show and uprading.
Just my experence, enjoy yours. Ray

Ted · Nov 14, 2009

Quoddy, keep in mind that the center of effort is a combination of the main and headsail assuming you are flying both sail. Simply speaking, you can calculate the center of effort of each sail by drawing a line from each corner of the sail to the center of the opposite side. For instance, from the clew to the midway point of the luff, from the head to the midway point of the foot and from the tack to the midway point of the leech. Where these three lines intersect is the center of effort of one sail. Do the same for the other sail. Once you have found the center of effort of each sail, connect them with a line. The center of effort of the entire sailplan is a point somewhere along that adjoining line proportionate to the sail area of each sail. If your main was the same square footage as your headsail, the COE would be at the midpoint of the connecting line. When you rake your mast, you are moving the COE of the entire combined sailplan not just the forces acting on the main sail. Raking the mast a couple of inches should have a noticeable effect on your helm. Now if you reef your main, the combined COE changes for two reasons. The center of effort of the main is different because the physical size has been reduced and the proportion of sail area between the main and headsail also changes. The main sail COE has less area and therefore the COE point on the line connecting both sails will move forward which will decrease weather helm (or increase lee helm)

Ted · Nov 18, 2009

Quoddy, the short answer to your question is yes. To induce twist you would move the jib lead aft of the present location for the unfurled jib. It's better to add a track with a movable car rather than another fixed block so that you can vary the amount of twist as the conditions change.