I have two questions:- 1) Please define precisely prebend (as opposed to rake) and how is it measured and set to the 1" quoted in the manual. 2) I want to know just how to get the forestay on the 33.5 really taught. From memory the manual refers to half bottlescrew on the forestay and backstays just taught before tightening the shrouds. Tuning mauals on fractional rigs with swept spreaders talk of high tension on the backstays before tightening the shrouds and thereafter easing off on the backstays whereby the caps tighten. This worked better and perhaps I could tighten the caps further without resorting to extension levers but the result wasn't perfect. Perhaps I should now tighten the forestay turnbuckle? I presume it's possible to get the forestay really tight? - How ?
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Steve O.
rigging
I think Jim may be cruising and since I have a 33.5 I'll answer. Mast rake is the degree to which the mast is tuned out of plumb. This involves the masthead being moved forward or aft from vertical (assume your mast is straight for the sake of discussion.) Pre-bend is how much the mast is tuned to bend by the spreaders and stays. Hunters with B&R rigging have a lot of pre-bend. I can see the bend in my 33.5 mast by looking up at the mast with my head at the base, and its a lot more than 1", I can tell you that. I've never touched my rigging but I'll guess that there is nearly 8" of bend in the mast, most of it in the topmost 1/3 to 1/4 of the mast. I don't know the specs for the 33.5 and I don't have the manual in front of me, so I guess I'm no help there. As for getting your forestay tighter, you may have to install a backstay tensioner/adjuster. You can buy one or make your own, but you'll probably have to remove your backstays to install it. You can probably use an existing halyard for a temporary backstay while you install the tensioner. If you're not comfortable I'd get a rigger to do it.
I think Jim may be cruising and since I have a 33.5 I'll answer. Mast rake is the degree to which the mast is tuned out of plumb. This involves the masthead being moved forward or aft from vertical (assume your mast is straight for the sake of discussion.) Pre-bend is how much the mast is tuned to bend by the spreaders and stays. Hunters with B&R rigging have a lot of pre-bend. I can see the bend in my 33.5 mast by looking up at the mast with my head at the base, and its a lot more than 1", I can tell you that. I've never touched my rigging but I'll guess that there is nearly 8" of bend in the mast, most of it in the topmost 1/3 to 1/4 of the mast. I don't know the specs for the 33.5 and I don't have the manual in front of me, so I guess I'm no help there. As for getting your forestay tighter, you may have to install a backstay tensioner/adjuster. You can buy one or make your own, but you'll probably have to remove your backstays to install it. You can probably use an existing halyard for a temporary backstay while you install the tensioner. If you're not comfortable I'd get a rigger to do it.
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David
33.5 tuning
I am also somewhat confused about the "science " of rig tuning on the 33.5. My 1988 H33.5 was in the yard for replacement of the compression post and the the rig should be tuned at this time. The yard simply marked the previous settings on the turnbuckles and retensioned to previous settings. According to my owner's manual, my rig is a conventional fractional rig; it is not a B&R rig--there is quite a difference. The manual has two different sets of instructions depending on the specific rig type, conventional fractional or B&R. The manual suggests setting the headstay turnbuckle half open and tightening the backstay to medium tension. The forward / aft position of the mast should be set with about an 8" rake.(halyard should drop to 8" behind the mast step) The upper shrouds should be adjusted until the mast is plumb athwartships and appx, 1" of prebend is induced in the mast. The lower shrouds should be tightened evenly ensuring that the mast remains straight. ( sight up the luff groove) The three shrouds should be tightened progressively with the uppers being tightest of all. Tighten the backstay to taught position, 8-10 turns past original position. Check the tuning sailing in 10-12 knot winds by sighting up the luff groove and ensuring that the shroulds are taut on the leeward side on both tacks. I purchased two Loos guages and plan to set the tension at appx 10% of breaking strength. I hope this works and I hope it helps to prevent my furling drum from binding inside the recessed housing. I have really procrastinated on this because I have never tuned the rig and everyone at the marina seems to have different ideas about tuning. I think that I will stick with the Hunter manual on this one. Let me know if you have any other suggestions. Thanks.
I am also somewhat confused about the "science " of rig tuning on the 33.5. My 1988 H33.5 was in the yard for replacement of the compression post and the the rig should be tuned at this time. The yard simply marked the previous settings on the turnbuckles and retensioned to previous settings. According to my owner's manual, my rig is a conventional fractional rig; it is not a B&R rig--there is quite a difference. The manual has two different sets of instructions depending on the specific rig type, conventional fractional or B&R. The manual suggests setting the headstay turnbuckle half open and tightening the backstay to medium tension. The forward / aft position of the mast should be set with about an 8" rake.(halyard should drop to 8" behind the mast step) The upper shrouds should be adjusted until the mast is plumb athwartships and appx, 1" of prebend is induced in the mast. The lower shrouds should be tightened evenly ensuring that the mast remains straight. ( sight up the luff groove) The three shrouds should be tightened progressively with the uppers being tightest of all. Tighten the backstay to taught position, 8-10 turns past original position. Check the tuning sailing in 10-12 knot winds by sighting up the luff groove and ensuring that the shroulds are taut on the leeward side on both tacks. I purchased two Loos guages and plan to set the tension at appx 10% of breaking strength. I hope this works and I hope it helps to prevent my furling drum from binding inside the recessed housing. I have really procrastinated on this because I have never tuned the rig and everyone at the marina seems to have different ideas about tuning. I think that I will stick with the Hunter manual on this one. Let me know if you have any other suggestions. Thanks.
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Denis Embleton
Response from David & Steve : Tuning 33.5 rig
Didn't know how to correspond other than by this method. Thanks for your responses. David, I've tried the approach of the manual and it does not achieve a v.taut forestay for me (maybe my fault). Steve, I suspect that tightening the backstay is not the answer as it applies tension to the top of the rig not the point of forestay attachement. Ref' my original note backstay tension does allow greater tension be applied to the cap shrouds which become even tighter when the backstay is then eased. This tightens the forestay but not enough - hence the question how to get the stay really tight. Finally the prebend per manual is 1" whilst the rake I agree is much greater (vertical from mast head away from gooseneck?), hence seeking clarity of just how prebend is measured.
Didn't know how to correspond other than by this method. Thanks for your responses. David, I've tried the approach of the manual and it does not achieve a v.taut forestay for me (maybe my fault). Steve, I suspect that tightening the backstay is not the answer as it applies tension to the top of the rig not the point of forestay attachement. Ref' my original note backstay tension does allow greater tension be applied to the cap shrouds which become even tighter when the backstay is then eased. This tightens the forestay but not enough - hence the question how to get the stay really tight. Finally the prebend per manual is 1" whilst the rake I agree is much greater (vertical from mast head away from gooseneck?), hence seeking clarity of just how prebend is measured.
J
Jim Bohart
some good replies.
Dennis it's right to follow the manual and the other answers were good, use them. To answer your other question. Pre-bend is measured near the center of the spar (it's tapered so it will be closer to the skinneir end) where the gretest amound of bend has been induced. It should be about 2% of the length of the spar (6-8 inches or more is good). The origional mainsail was luff cut with this in mind so you could flatten the main with just outhaul, cunningham, and vang. The luff sag in the jib can be more than you think and the jib if cut properly to that sag (again it's 2-3% of the luff length) then the boat is set up the best you can and your windward performance will be as good as you can make it. JB
Dennis it's right to follow the manual and the other answers were good, use them. To answer your other question. Pre-bend is measured near the center of the spar (it's tapered so it will be closer to the skinneir end) where the gretest amound of bend has been induced. It should be about 2% of the length of the spar (6-8 inches or more is good). The origional mainsail was luff cut with this in mind so you could flatten the main with just outhaul, cunningham, and vang. The luff sag in the jib can be more than you think and the jib if cut properly to that sag (again it's 2-3% of the luff length) then the boat is set up the best you can and your windward performance will be as good as you can make it. JB
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