Mast rake

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R

red coles

Hello John: I was reading your response post to Walt,and noticed your statement about mast rake. I have a '78 h27 which I enjoy very much. My only gripe is with weather helm in medium breeze. If I heel over 15 deg. it's almost impossible to hold course. I have done the sail and running rigging, twitching and tweaking and have progressed to mast rake. On my previous boat ( Coronado 25 ) I eliminated almost all my weather helm,by adjusting mast rake, finally ended up in almost vertical position. On my h27, I am now almost vertical also. Your response said, all your Dad's boats had mast rake. Would you recommend I return to this and continue flattening or reducing sail as a remedy? BTW, we're really fortunate to have you on this board (a little flattery never hurt :eek:) Good luck red
 
S

steven f.

shorten sail

After about 15 degrees of heel your boat is loosing its efficiency, it's simply heeled over too far. Obviouslly it will still sail but you would probably find that your speed and handling abilities will improve if you shorten sail or flatten your jib and/or main. Raking the mast may also improve your helm but start with the simple things, proper sail trim.
 
R

red coles

Mast rake 2

Hi Steven: Thanks for the reply. While I realize sail trim is basic to boat control and I have a pretty good working knowledge of same, my basic question for John was, should X amount of mast rake be a hard rule on the cherubini's. While it's true my main is cut a little full ( for our light predominate SW FL wind) I can flatten it with vang,halyard,outhaul and traveler. Jib is roller furl and can only be shaped slightly ( it's a 110). I do feel the center of effort may be too far back. Case in point,when under jib only in heavier winds and 20 deg heel, helm is easily controlled. Yes, I've heard the arguements against jib only in heavier air, but I'm a cruiser and it works for me. Anyway thanks again for reply, and keep smiling, it confuses them. Good luck red
 
Jan 22, 2003
744
Hunter 25_73-83 Burlington NJ
Mast rake (and my typo)

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
 
Jan 22, 2003
744
Hunter 25_73-83 Burlington NJ
Hunter 27 heel angle.

Now for Red's problem. The H-27 gets a reputation for being really roly-poly in any weather over about 20 knots, and some of this is sort of due to the design. For one the shoal-draft keel makes it really hard to hold the boat anywhere close to level. This is not unsafe– most of my dad's boats are noted for what I call 'dizzying' heel angle. It's a factor of having typically high sail-area-to-weight ratios. I noticed that Red does not mention that the boat ever goes much farther than 15 degrees– I have never heard anyone else say so either. My dad's boats are never unsafe- they typically tend to find a goroove and then stay in it come what may. However Red's point about having to deal with sail trim at these nosebleed heel angles is the next issue. The H-27 also has the boom too high. The sail area itself is fine and the boat is not too light, but wth the CE so high in the rig it takes less wind to get it going over (more arm for the same moment). The high boom is once again a factor of – you guessed it - marketing, who insisted that since the H-27 was a 'big' boat now, you should be able to stand under the boom in the cockpit. The rude fact is that my dad could not have cared a whit for that. He also did not care for shoal-draft keels to avoid bumping bottom either (who else would design an ultralight plywood bay boat perfect for a centreboard but with a fixed 4-ft keel instead? As a pilot of B-24s with that LONG leading edge and dinner-knife airfoil he knew deeper keels are better-handling). The recommendations I would make include, as Steven suggested, reducing sail. This is easiest. Be sure however that your jib leads are correct and that you are using whatever purchase you can on the main boom to keep it DOWN. As soon as you reef you lose sail shape and then there goes the whole argument. I think a tighter leach line on the main would help too. Do not attempt to DRIVE the boat to weather with the jib– this will plow the bow down which gets really hairy. The main is the real power plant anyway. Further I have suggested that the H-27 needs a proper traveller, not on top of the cabin but across the front of the cockpit, where it can grab the end of the boom and really yank it DOWN. Once this is installed you can lower the boom gooseneck and really make a difference. The late John Eggers from Perth Amboy, one of our early sailmakers, used to winch everything home till it was as flat as a sheet of plywood– he would break stuff on your boat insisting that flat sails pull strongest. But these hardware changes aside, I really think that prudence as a sailor, and knowledge of sail trim and rigging tuning, will help a lot, at least at first. I would very much like to hear from H-27 sailors with deep keels to see if they have the same sort of trouble. And let's hear from people who have improved their rigs a litle, like I may have suggested, or otherwise. But I caution anyone to refrain from making drastic changes till you know for sure you have got the rigging tuned to factory spec, including the mast rake (maybe try about 10-12 inches to start). Hope some of this drivel helps. JC
 
R

red coles

Thanks John

Hi John First, thanks for the quick response. I appreciate the info and will do as you reccomend. I feel quite a few people on this board will gain from your comments. Just by coincidence I had already lowered my boom 3", mainly so that when I tensioned the luff, my halyard (wire/rope) thimble wouldn't wind up on the winch. Again, thanks for the info, and the stories about your Dad Good luck red
 
Jan 22, 2003
744
Hunter 25_73-83 Burlington NJ
Mast rake, or whatever.

Actually this weekend I was just looking over the sail plan to the ORIGINAL Hunter 54 cruising ketch (did you know there WAS one?) of 1979 and he has got the masts just about vertical (no angle specified for mast rake). So it may have depended on the boat. For myself I would definitely impose some rake on that boat, for looks if nothing else– which by the way ought to be considered typical of my dad. He was a self-taught engineer and really did know his stuff, but he was also a consummate aesthete (definitely RARE in engineering fields). If he did or did not specify mast rake you can bet the primary rationale was for looks– but then he would have known the physics issues it implied and been able to cope with those successfully too. So I apologise if I gave the impression that ALL his boats had mast rake (although I am quite sure the earliest Hunters did). Maybe I'm just a twit. JC
 
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