J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Wooden blocks at the partners

I am curious as to what others do, if anything, with blocks or wedges at the partners in order to support the mast.
All I do is put a thin (1/8") pad of rubber behind the mast where it rests against the partners. I use no other blocks, wedges or materials such as Spartight.
Any opinions as to whether this is good, bad or indifferent?

I recently went through this and found that the previous owner used small rectangular pieces of starboard.

On the sides, the pieces run horizontally, and at the fore/aft, they are smaller bits that run up and down.

I cant tell if he planed them down, or just used different thicknesses, but the end result is really nice. Since the starboard bends, the mast is supported at the partners by a wide surface area instead of smaller shims; could prolly do the same with wood, but starboard isn't going to rot.

As it turned out, he got the mast to the prescribed location, and nice and straight, so I didn't have to change anything.

This may be a bit of overkill, but is definitely a slick way of doing it.

-dan

I used surplus cedar shingles I had in the garage. They have a slide angle that allowed shimming between the mast and sides from the bottom. The I broke them off level with the deck where they protruded through the top. They are held in place with 1 wrap of white tape. Inexpensive and easy to work with.

Thanks,
My real question though is; do I need any shims at all? Right now there are none. I've had this set up for most of the 26 years I've owned the boat. Is there risk to the mast by not having any shims at the partners? Is there any effect on boat speed and performance by not using shims.
What do they help or as in my case, what do they hurt by not being there?

Russ - I don't know if it is "good" or "bad", but do know that I center the mast before starting the adjustment of uppers and lowers. This from the UK Tuning Guide

.....
2) Remove partner blocks and center mast with upper shrouds. Use the main halyard to equi-distant points on either rail as a guide. Take-up on the lowers just enough to keep the lower mast in column with the top (hand tight).

3) The mast step should be maximum forward (so that the forward edge of the mast is 25mm aft of the forward vertical face of the molded step in the sole liner. Block mast in front, pushing it as far aft as possible in the partners. This will reduce prebend in the lower mast sections.

4) Adjust wooden blocks so as to fit snugly on either side of the mast partners. Shimming and/or planning may be necessary, as there is a good chance that the mast will not be perfectly centered in the partners.
......

I tune the mast the same way:
1) Mast step forward, forestay at max length, center the mast tip using a halyard, etc
We do not however, block the mast in front pushing it aft as far as possible. But my guess is that if you crank down on the uppers before you block the mast from the front, the pre-bend is already in the mast from mast tip to step and you won't take it out from the partners down to the mast step by blocking in front of the mast. By blocking the mast from the front after tuning, one might reduce mast bend below the partners when applying backstay tension. Is my thinking wrong?

General setup we start with is the same as Russ with J at 11.5' per class rules, though I don't often measure this. At one time we had to pound blocks into one side to get the tip centered, but I'll have to admit lately most of our blocks have gone missing and it has not seemed to matter. Blocking forward may push the bend up the rig as you tighten the uppers or apply backstay. Blocking sides may help keep the stick in column, though some of the current ideas on light air tuning want the stick to sag to leeward. We're also tightening the headstay along with the rest of the rig as breeze increases. In theory this only reduces headstay sag without pulling the mast tip forward.

The J is actually 11' 6" +/-1/2" (3505mm +/- 13mm) I recommend setting this at Max which will give you max rake in the rig thus better up wind performance. I set mine up 10 years ago with Spartite it was well worth the money rig has been in and out at least four times with no damage to the spartite plus almost no leaks at the deck when it rains !

Charlie Stoddard
fleet 13 measurer

I have a question on the mast partners... I have hull #4 and by the looks of things, the partners were changed at some point between my hull and more recent hulls. My partners are very large and I have layered plywood carved out in the shape of the mast in place of wedges.

If you haven't seen it, there's literally 2" forward and aft and probably an inch on either side. I've been trying to tune the rig to reduce some of the wicked weather helm, but "block the mast as far aft as possible in the partners" is a useless statement. I have the mast nearly centered in the larger, rectangular partners.

I have the step plate set around 1" aft of the vertical in the head, making the mast closer to 2" aft. If anything, moving the foot of the mast further aft, thus moving the head of the mast forward, would reduce weather helm right?

I have a roller furling on the boat, but the headstay without the sail is snug, but not real tight. The backstay is tight when the turnbuckles are almost all the way down, and cap shrouds are around 45, lowers around 44.

I will take some measurements, but the mast is raked probably 2" with maybe 1-2" of pre-bend.

Any thoughts? Thanks.

Kyle

The early hulls have a much larger hole in the deck for the mast. I figure J/Boats had not yet figured out how they were going to set the rig up. Most of the racing tune suggestions have to do with reducing lee helm by having more rake, inducing more weather helm, thus step forward, headstay max. Your rig sounds plenty tight, the question is do you have enough weight on the rail for the amount of sail area you have up. Several times over the past month we have raced Wed nights with five people and well under 1000 lbs. Keeping the boat flat makes a big difference beating and can help reaching. If you don't have max weight then you must drop the traveler down, put backstay on, or use less sail area.