Hang'em High Booms

[Andy]

I have noticed some of the the larger racing boats have booms that angle up (dramatically) on the aft end .In some pictures it looks as if the foot of the sail must be cut at an upward angle significantly. I am a bimini/bar-b-q sailer and I want good sail shape and and clearance . I put a flattening reef in the main to slightly angle the boom under sail. (As opposed to raising the gooseneck.1. Does a boom that is not parallel with the deck change trim, sail shape, dynamics, etc dramatically?2. Would you recut the sail and do away with the flattening reef or just live with it?

 

[Alex]

I did it

I had same problem on my 95' 29.5 ; in order to enable a high bimini', I gave to sailmaker to cut diaginally about 10 inch from the main leech . What happened , is that there is more pull on the leech , which makes for more curve -and lees flat- in the upper sail section, not such a good thing overall. I was told by the sailmaker - afterwards..- that same result would be acheaved with flattening reef...If you dont mind the estetics , and are still able to tune the outhaule , it doesn't matter. Regarding the boom diagonale angle of big recers, the goosneck is actually very low positioned, almost at deck level , so they have to take it higher going back to clear the cockpit.This is done both for structural reason and to 'close the gap' between the sail and the deck, for smooth air flow. The new Hunter 50 has integrated this to some degree ,( I think more for structural intergrity reason) in a very interesting and good looking way.

 

[Justin Wolfe]

You're a bit confused

I'll assume when you say racing boats you mean Around Alone / BOC boats. Yes their booms are angled up, but not because they want them to be. As Alex was mentioning it is not the aft end of the boom that is high, but the forward end that is low. This adds sail area down low and creates a stronger attachment point. Now unless you can live without a dodger and your boat is 18' wide (eliminating the need for a boom vang) copying this isn't going to help the performance of your Hunter. Angling you boom up with a flattening reef or sail recut will only depower the sail. That might be fine in heavy air, but in light air you will be losing out. Don't put the flattener in unless the boat is heeling more than it should. In light air you want all the sail are you can get.If your current boom height is hitting your bimini then you should go ahead a recut the sail. The trim of main won't change any due to the angled boom.

 

[Bill Colombo]

Bomm angles etc.

Andy, The angle of the mainsail tack determines the height of the boom at the other end. Usually this angle is 90 degrees, although it can vary from boat to boat. Different tack angles do not directly impact sail performance. A mainsail built with a shelf foot and flattening reef is designed with a bit of "droop" so the boom is near level when the flattener is "on". The flattening reef works because it pulls on the cloth above the designed curvature that returns the sail to the boom groove. The trend in mainsails today is to forego the flattener and design mains with a 90 degree tack and a loose foot. On your current sail, if you like the boom a bit higher I would suggest shortening the leech to your flattening ring, and consider a loose foot so that you can still "round up" the lower part of the sail in lighter winds.Good Sailing, Bill Colombo, Doyle SF