New owner of 84 Hunter 34 and am currently having a new main sail made. The mast is down at this time with shrouds and spreaders all removed. Sailmaker has asked me what the pre-bend of the mast is. Can anyone help me with this question? Randy
Mast pre-bend
- Thread starter Randy Church
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Try...
...searching the archives for B&R rigs. The amount of prebend is probably related how tall your mast is. For me I have about 4-5" of bend. If you have an in-mast furling like I do, then the amount of bend is less than normal. I found this most helpful: http://home.att.net/~radars/ownersman.html Also see here: http://www.hunterowners.com/ref/br.html http://www.ayesail.net/sailing/MAST_TENSIONING_PROCEDURE.htm
...searching the archives for B&R rigs. The amount of prebend is probably related how tall your mast is. For me I have about 4-5" of bend. If you have an in-mast furling like I do, then the amount of bend is less than normal. I found this most helpful: http://home.att.net/~radars/ownersman.html Also see here: http://www.hunterowners.com/ref/br.html http://www.ayesail.net/sailing/MAST_TENSIONING_PROCEDURE.htm
Believe the specs say
I beleiev the spec say 5" for the H34 mast. I normally set mine for more like 4 as I find I have too much weather helm ( probably baggy sails!) At any rate you can set for anything up to 5 - probably 6 if you wanted as there is quite a bit of thread left in the turnbuckles at 5"
I beleiev the spec say 5" for the H34 mast. I normally set mine for more like 4 as I find I have too much weather helm ( probably baggy sails!) At any rate you can set for anything up to 5 - probably 6 if you wanted as there is quite a bit of thread left in the turnbuckles at 5"
Have the mast rigged first.
Randy: I would suggest that you have the mast rigged now and have the sailmaker make some exact measurements. It is supposed to be setup on the bench and then stepped anyway. This will ensure that proper fit. You are spending $2500-3500 for a sail, so it should fit properly. The exact instructions are available under the Resource tab.
Randy: I would suggest that you have the mast rigged now and have the sailmaker make some exact measurements. It is supposed to be setup on the bench and then stepped anyway. This will ensure that proper fit. You are spending $2500-3500 for a sail, so it should fit properly. The exact instructions are available under the Resource tab.
Measure the mast in its horizontal...
and provide the measurements to your sailmaker. Explain that the mast is down and there is no pre-set mast bend so you would have the flexibility of adjusting pre-bend to his recommendation for the sail. Provide him fore and aft diameter of mast, height from deck to forestay fitting and heigth from deck to boom goose neck. This will allow him to calculate pre-bend and maximum bend for your boat. This will also give you an opportunity to determine how competent the sailmaker is. 4-5 inches sounds reasonable for your boat specs. Anything to far away from that get a 2nd opinion with a rigger.
and provide the measurements to your sailmaker. Explain that the mast is down and there is no pre-set mast bend so you would have the flexibility of adjusting pre-bend to his recommendation for the sail. Provide him fore and aft diameter of mast, height from deck to forestay fitting and heigth from deck to boom goose neck. This will allow him to calculate pre-bend and maximum bend for your boat. This will also give you an opportunity to determine how competent the sailmaker is. 4-5 inches sounds reasonable for your boat specs. Anything to far away from that get a 2nd opinion with a rigger.
You are obviously going to have to have the mast steppeda nd rigged sometime soon; why not have it done now and get the rig correct 1st. Then have the sailmaker measure the prebend, the boom height and exact length; including the mast bend measuremaent with the backstay adjuster full 'on' if you have one; and with the Bimini up if you have one as well. You will save a lot of second guessing and finger pointing and have the best shot at getting the sail right. I completely agree with Steve Dion and it's exactly what I did myself and my sailmaker was used to Hunters and B&R rigs.
This is set with the mast off the boat. Prebend is supposed to correspond the the built in luff curve of your main. As the main gets a little baggy over time you need to INCREASE the mast bend to compensate for the additional draft. Increasing mast bend DECREASES draft and therefore gives a flatter main NOT the other way round. A flatter main will minimize weather helm which the 34 is pron to.
Hunter provides sailmaker info. on request
I don't know if they keep such info going back to 1984, but Hunter provided me (on request) with sailmaker specs for my (newer and different) boat. I'd at least ask, as you'd get the real specs, rather than an approximation. Pre-bend is usually specified as a % of the "P" measurement (distance from gooseneck to halyard sheave, or mainsail luff length). Many boats seem to be designed for a 1% pre-bend, though certainly not all. (My mainsail has a very large positive roach, which is counterbalanced by a 2% pre-bend - 10.8" in the case of my 45ft P dimension.) Pre-bend in roller furling masts is like bend in a window shade - not conducive to rolling-up. Since most newer Hunters seem to be bought with in-mast furling, my dealer's commisioning guys set mine up (much easier before stepping the mast, as Alan said) with about 3" of pre-bend. When Doyle delivered my nice new all-full-batten mainsail with 3 reef points, it looked more like a sail-bag than a sail, until I got out my Top Climber and adjusted the upper and lower "reverse-diamond" stays to get the 11" prebend. With the 2% prebend, the sail shape is gorgeous - even triple-reefed. It is an important thing to get right. Ask Hunter.
I don't know if they keep such info going back to 1984, but Hunter provided me (on request) with sailmaker specs for my (newer and different) boat. I'd at least ask, as you'd get the real specs, rather than an approximation. Pre-bend is usually specified as a % of the "P" measurement (distance from gooseneck to halyard sheave, or mainsail luff length). Many boats seem to be designed for a 1% pre-bend, though certainly not all. (My mainsail has a very large positive roach, which is counterbalanced by a 2% pre-bend - 10.8" in the case of my 45ft P dimension.) Pre-bend in roller furling masts is like bend in a window shade - not conducive to rolling-up. Since most newer Hunters seem to be bought with in-mast furling, my dealer's commisioning guys set mine up (much easier before stepping the mast, as Alan said) with about 3" of pre-bend. When Doyle delivered my nice new all-full-batten mainsail with 3 reef points, it looked more like a sail-bag than a sail, until I got out my Top Climber and adjusted the upper and lower "reverse-diamond" stays to get the 11" prebend. With the 2% prebend, the sail shape is gorgeous - even triple-reefed. It is an important thing to get right. Ask Hunter.
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