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Hunter 30 Mast Rake and Mast prebend

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Oct 25, 2011
30
Hunter 37 Cutter Yankton SD
Hi - going to be replacing Fore and Aft stays, and setting mast prebend and rake. Not finding much info so far. I think it's a Kenyon mast, they're out of business. I think I need a bit of prebend to flatten the sail and match the cut made for the main with some prebend. Saw some article once from a Cherubini about his dad's rake, but nothing speciific for a Hunter 30, I've got a 1981. Will be putting on new Harken MKIV furler and new sails this spring. Any info would be appreciated. A rigger recently told me about 4" of rake sounded right.

Thanks,
Paul
 
Jun 2, 2004
5,802
Hunter 37-cutter, '79 41 23' 30"N 82 33' 20"W--------Huron, OH
Nov 8, 2007
1,237
Hunter 27_75-84 Lady Lillie Sandusky Harbor Marina, Ohio
In column

My understanding is that the masts on Cherubini Hunters were designed to tune in column. That is how we do it, and our sails are cut on this assumption.

I see nothing against adding rigging to bend the mast while under way, but think that you would be on your own as far as support from the original design is concerned.

I see no advantage to a permanent bend in the mast, since a sailmaker could flatten the cut of you sail for you, and you could leave your mast in column.
 
Oct 25, 2011
30
Hunter 37 Cutter Yankton SD
Makes a big difference if the mast should be tuned in column, or with some prebend. I think I will contact Chip at Hyde sails, see what their computer assumes that the mast profiile will be when he designs the sails. I'm likely going to order sails thru Hyde at this point.

Paul
 
May 31, 2007
716
Hunter 37 cutter Blind River
Generally speaking, fractional rigs are designed for bending to affect sail shape. This is usually done on high performance hulls and rigs. The Kenyon masts are extremely stiff and were designed to stay in column. The boats were designed to be safe and comfortable. While they are not dogs, they are far from light weight and high performance.
 
Oct 25, 2011
30
Hunter 37 Cutter Yankton SD
Mast Rake from JC II

I found John Cherubini's comments on mast rake and just pasted them below...... from JC II

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I accidentally made an egregious error in these boards about mast rake and have to clarify that I confused myself. I suggested 10-16 degrees of mast rake on about a 30-footer. This is WAY wrong– I meant 10-16 inches, measured at the masthead (about 5 degrees? –not doing trig here). Tie a plumb-bob to the topping lift, drop it to the deck, and measure how far back it lies from the aft edge of the mast (discard an inch or so for the masthead sheave). If the plumb-bob is bumping the back edge of the mast or even within about 4 inches you are WAY OFF. My dad's boats are all noted for mast rake. In fact some of them will look downright 'rakish' in profile. Our Cherubini 44 cutter had a J (foot of foretriangle) of about 20 feet from the end of the bowsprit and I swear you'd measure that mast rake in yards. It must have been about 6 ft on a 56-ft hoist. It resembled his 31-ft yawl of 1961 which has 1:16 rast rake– 2 ft for a 32-ft hoist. But no Hunter is going to be THAT raked. Mast rake is sort of a cheater way of inducing weather helm. The standard plain-Jane cruising boat will have its centre of effort (sail plan) about 15 percent of the waterline FORWARD of the centre of lateral resistance (underbody). This would suggest that the boat would have a severe lee helm. But the forward momentum as provided by the wind and the airfoil shape of the keel actually works to fool the design of the boat. That momentum sort of carries the boat straight through the forward difference between CE and CLR and it's like the boat becomes more interested in moving forward than bearing off. The CE is determined from the standing-still rig of the boat, what we should call the designed sail plan. Mast rake is already designed into that. The problem I belive many Hunter owners are having is that they have had their rigs tuned with the mast too vertical. If the mast rake specificaion is included in the forward justification of the CE, tuning the mast too vertical will actually spoil the boat's intended balance and further exaggerate that 15-percent-of-waterline difference. You will in effect have induced lee helm, sort of as if you've let the jib luff or not even put it up at all. There is logically no way you will be able to point well like that. Drawing the masthead aft will return these ill-tuned boats to a weatherish tendency and then all you'll have to worry about on the wind is keeping tell-tales parallel and jib lead position and leach tension and other fun stuff like that. Actually it is safe for all boats to have more weather helm than lee helm anyway. It is a sort of natural homing instinct that can help in emergencies, heavy weather, anchoring, and finding your bearings. If boats did not have a designed-in tendency to come into the wind you would never be able to come about! -or make your way home. I tend to suggest to people to lower their boom goosenecks and even have the mainsails recut to be 6-8 inches lower than I do to increase jib sizes. We get so rah-rah about headsails being leading edges and airfoils that we forget that the mainsail is the real power plant on most boats. Preserving mast rake will help the main do its real job fairly. JC II
 
Jun 5, 2010
990
Hunter 25 Burlington NJ
Not sure how clear I was in that older post, nor am I sure if I answered the guy's question.

Few boats will not benefit from imposing (via the standing rigging) about 1-1/2 to 3 degrees of mast rake. The great problem so many people have is that they fail to properly tension the headstay after the furler is installed. Furler extrusions are heavy! --and all of them require additional tension to keep the headstay tight. Sometimes this added tension can be enough to break something else; and it is not uncommon to break stemhead fittings or mast cranes, especially on older boats when the headstay itself is far older than the newer furler. Worrying about this, many people tension the headstay to only where it was specified to be without the furler; and they sail around with sagging headsails and complain that the boat won't go to windward as well as they'd expected.

Perhaps worse is when the forestay is replaced with the furler and comes up, for whatever reason, a little too short. I saw a Raider 33 like this and the boat actually had forward mast rake. I wonder how those people ever tacked the boat at all.

By 'prebend' I assume you mean a progressive rake angle, more above the spreaders than below. I would not impose 'prebend' on a cruising boat with a masthead rig. What would be the purpose for this? A 30-year-old Hunter 30 is not a racing Star. Few people would realize much benefit from a move that inordinately stresses the 30-year-old mast, mast step and deck structure. If anything I would add a backstay adjuster, however-- especially if you have added a furler. I put one on Diana and I don't even have a furler. Keeping the headstay properly taut can never hurt; and allowing it to sag is like robbing your car of fuel mileage.

I would not, however, add more purchase than necessary to the backstay adjuster. I have 4:1 purchase and just got the idea (though have not yet installed it) to loop the line over a block at the bottom of the adjuster car and take it down to the other side rail, thus yielding about 8:1 (take away some for the slight angle to the legs; call it 7.5:1). But I would not advise using some kind of power advantage, an electric motor or, worse, hydraulic gear, on a boat that's not designed expressly for it. Some of those hydraulic systems could pull the transom right off the boat or shove the mast through the keel.

I agree with Ed and would tune the rig at the dock to include about 4-6" of standing mast rake. Measure by hanging a plumb-bob from the halyard and see where it lands on the deck. I see no reason for more than this; and having less (mast tuned in column) probably won't hurt but would allow forward rake if you haven't got the headstay, under the burden of its furler, tight enough. Remember to keep the lower shrouds taut as well, and to fine-tune the forward ones last.
 
Oct 25, 2011
30
Hunter 37 Cutter Yankton SD
JC - thanks for your reply. Quick question... do you think it makes a big difference with different sizes genoas 120 vs 150? Most of the added sail is behind the mast, and I have read a lot about matching your rake to boat handling, or weather helm. On Hobies we adjusted our rudders forward or back to compansate for different rakes, not so on the Hunter 30.

Am still in process of determing current rake so I can order my new furler and and a new forstay of appropriate lenth. Wish my boat was in the water so it would be easier. I added the Harken MKIV unit one toggle to the bottom of the forstay, adds about 3" length. Rake now is about 6" but not sure my boat is level as it would be on the water. A level on the settees show that Im still bow up, even though the waterline on the outside looks level. If I'm bow up, then in the water that mast rake will dissapear. So if anyone has their Hunter 30 in the water, put a level on your settee and let me know if that's a good indicator of level. Another 6 weeks and the boat will be in the water, but would like to get the furler on now, and order a sail.

Paul
 
Jun 5, 2010
990
Hunter 25 Burlington NJ
Paul, I like your choice of about 6" of rake and, for now, would leave it so. I'm glad to see you even considered adding a toggle; so many don't think of it. Also, you added it to the bottom, which is good. Remember that unless it is all the way out a roller-furling headsail is absolutely terrible for pointing; and because they have to roll up they are usually cut a little funny along the bottom. Adding the height to the bottom may actually help you get more out of the sail than if you added it to the top (not to mention that it would not help with added weight aloft).

I am not sure the settees are even level-- my vee berth certainly isn't! Renting a transit for a few hours might be a good answer. But you can always add another toggle when you are in the water. And definitely consult your friendly neighborhood sailmaker.

It is true that long-in-the-foot headsails actually add to weather helm. For some reason, though they are hung from the headstay, they do add sail area abaft the mast and sort of help the boat weathervane around into the wind more. Anything over a 150 is just unnecessary unless you have it poled out downwind in the trade winds.

In Olin Stephens' wonderful book All This And Sailing Too he shows a photo of one of his 1930s designs sporting a '210' headsail-- sheeted to the very corner of the transom with the clew actually aft of the mainsail's. For some reason they actually liked this idea then (though OS didn't seem to agree).

I like only those headsail furlers that allow you to change headsails. I don't have one now but I'm thinking of getting a Schaefer Tuff Luff which amounts to a furler with no drum. My headsail complement will include a 130/135 and a 150. These can be of different weights to make more use of them both. The very worst thing is to be stuck with a genny that is more trouble that it's worth-- and remember the Sunbrella cuff along the leech really destroys much of its light-air abilities anyway. So take that into consideration.
 
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