Mast rake & bend

o2go2c · **Joined:** 03 Jun 2007 06:26 **Posts:** 1

Hello everyone. We're new to the site but not to the T37. This is our 4th year with Night Music, hull #157. We are members of TONE. Looking forward to participating in this forum !! Lots of knowledge & experience out there with all of you & this is a great way to share that.

We're in the process of having a professional rigging inspection completed. One of the first things he noted was that the mast was too straight. The rigger was not sure what the factory spec is for the T37C so we both agreed to do some research. Does anyone know what the specification is for degree (inches?) of rake for the 37C? We're going to have to add several inches to the fore stay to gain any degree of rake. I have not called Tartan yet but I plan to this week.

Bend is another question but as we're not racing , I'm not sure that I want to stress everything with those levels of force. Thanks & looking forward to your thoughts.

Steve

Down2TheC · **Posted:** 03 Jun 2007 07:28

Welcom to the forum! Can't help you with the rake issue since we have furling main. But I'm sure one of the racers is well versed on the stock rigging.
Tartan

Tortuga's Lie · **Joined:** 27 Oct 2006 10:32 **Posts:** 827

We have about a 5 to 6" total rake in our mast but the mast section is quite stiff and meant to be beefy. I don't believe you'll be able to get much bend out of it. There is a sleeved-joint near the spreaders, which won't flex and I don't think you would want to stress it anyway. Just my two cents worth.

redvette · **Joined:** 14 Dec 2006 22:13 **Posts:** 59

I dealt with the issue also, and had to add a toggle at the base of the roller furling to allow for a little rake. I cruise, don't race, but still like a good performing boat. I had the marina down the road (sailboat specialists) tune the rig for me. I have about 5-6 inches of rake also I believe. As was stated, it's a beefy mast and does not give like newer masts do.

Mark

Jay · **Joined:** 22 Oct 2006 19:25 **Posts:** 61

I probably also have 5 to 6 inches of aft rake, but I believe that to be excessive. Indeed, I'll probably adjust the mast for no rake in the future. The T37 was designed in the 1970s with IOR racing in mind. The then rules favored small mains and large genoas, ie the T37 was designed for a 155 genoa, and I believe many of the PHRF ratings assume that is the size of the T37 headsail. With 5 to 6 inches of aft rake and a 155 (the larger the genoa the further aft the center of effort), excessive weather helm can develop when close hauled or reaching in winds over 10 knots true. While to an extent the excessive weather helm can be controlled by depowering the main, this may reduce speed. Moreover, controlling weather helm with the rudder may also reduce speed due to rudder drag. Decreasing rake decreases weather helm. Thus, if your headsail is as designed, ie a 155, and you often sail in winds in excess of 10 knots true with the 155 unfurled, then my recomendation is at most a couple of inches of rake. I concur that the mast on the T37 is quite robust and probably not built with an adjustable backstay in mind. Bending the top of the mast back bows the mid section forward thereby flattening both sails, reducing and moving the draft aft, de-powering the sails, reducing heal, and reducing weather helm to the extent its caused by too much heel. Beacuse a backstay adjuster's primary purpose is to enable more sail to be carried in higher winds, the mast rake is not a function of weather you have a backstay adjuster or not. Incidentally, on a T37, a backstay adjuster seems to have more effect on the headsail than the mainsail. Jay.

Tortuga's Lie · **Joined:** 27 Oct 2006 10:32 **Posts:** 827

Jay, Is your boat a C/B or a deep keel version? That could make a big difference on weather helm as well. I usually have a 150 genoa up with no noticable weather helm, in fact she'll balance right out and sail for twenty minutes w/o touching the wheel, but that could be a bad thing if I were to be knocked overboard Shocked

Jay · **Joined:** 22 Oct 2006 19:25 **Posts:** 61

My 1979 T37 has a centerboard. Initially, I thought the T37 weather helm when close hauled in 15 knots true with the 155 unfurled and the CB fully extended was a case of faulty standing rigging, running rigging, or sailor ineptness. Apparently, the weather helm is normal on a CB boat with the cure being to drop the traveler to leeward even if it causes the main to backwind from air in the slot between the genoa and main. Reducing the rake to a few inches may also enable better mainsail trim. And raising the centerboard somewhat should also reduce the weather helm. Jay.

Tortuga's Lie · **Joined:** 27 Oct 2006 10:32 **Posts:** 827

Jay, looks like you have more sail area up in that wind condition which would be the reason for the weather helm. Are you racing her? My wife would make me furl in a bit or put up the 135 in 15 knots of wind........but your having more fun!!!!

Jay · **Joined:** 22 Oct 2006 19:25 **Posts:** 61

Actually, furling the headsail may create more weather helm. Although furling the 155 moves the headsail's center of effort forward, it also reduces the magnitude of the effort. Weather helm is caused by the combined center of effort of the main and head sail being aft of the hull's center of lateral resistance. The most direct way of moving the sails' combined center of effort forward is to luff the mainsail, or furl/reef the mainsail. And yes, I race the T37. Jay.

Down2TheC · **Posted:** 24 Jun 2007 23:02

Even with the full keel and a furling main, we get weather helm when close hauled in light winds. Jay's solution works for us. We get the best speed and balance with a "bubble" in the main. Just getting the luff to back wind a bit really optimizes "the slot" for us. Hard core racers that have raced with us tell us to trim up and we have to prove to them that we lose a few tenths without that bubble.

Tartan37.com

Mast rake & bend

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