Straightening keel stepped mast

[Kabunza]

I need to tune my mast which includes straightening it athwartships. My mast is keel stepped with a chock wedge at the deck providing little play. What’s everyone’s opinion regarding straightening the mast, whilst leaving the mast chock in place?

[chrisr]

you should remove any / all deck chocks before adjusting mast

there should be free movement around the mast at deck level, so that the mast maintains a straight line in both planes (F&A and athwartships) from the heel to the masthead.

once the mast is where you want it, replace the chocks (nb : such may need modifying if the mast has moved at deck level)

OOPPS EDIT : just re-read your post wherein you say "My mast is deck stepped with a chock wedge at the deck"

this doesn't add up ! deck-stepped masts don't have deck chocks - is the mast is stepped on deck or on keel ??

cheers,

[Kabunza]

Oops. Thx chrisr. Just corrected my post from deck to keel stepped.
I was afraid you’d say that about the chocks. I recently paid a rigging guy to step and tune my mast and rigging and I’ve come to learn what a lazy job he did. Hard to think about starting over just when I have all my leaks fixed to.

[chrisr]

Originally Posted by Kabunza

Oops. Thx chrisr. Just corrected my post from deck to keel stepped.
I was afraid you’d say that about the chocks. I recently paid a rigging guy to step and tune my mast and rigging and I’ve come to learn what a lazy job he did. Hard to think about starting over just when I have all my leaks fixed to.

sorry about that

but you shouldn't be relying on your deck chocks to keep out the water. should be a rubber boot around the mast and attached to the deck.

something like this



cheers,

[Kabunza]

I do have a mast boot. Leaks were from old mast boot.

[Sherpa17]

What kind of boat and what type mainsail do you have? I ask because some boats sail better with a little pre-bend in the mast so the position of the mast step alon with the wedge becomes a factor.

I've rigged a lot of boats and the wedges are the first thing you want to fit, particularly If it's a spar tite collar (blue urethane).

If you have a sail plan, you can get the rake and pre-bend measurements using a framing square. A sail plan shows the designed waterline as a horizontal line. Put one side of the square on the waterline and the other side tangent to the aft side of the masthead. Note the distance from the gooseneck to the vertical side of the square. Hang a tool bag on the main halyard as a plumb bob and adjust fore and aft.

I attach a fishing scale to the main halyard to get athwartship measurements. I put a mark a couple of feet from the end as an index mark. I attach the scale to the chainplate and pull equal pressure on the halyard side to side and measure from the index mark to the deck. It's pretty accurate.

[Kabunza]

Hi Sherpa17
I have a Pearson 36-2 with a mast head rig and Dacron sails.
After using my halyard to see how straight my mast is, I'm finding I'm about an inch off on a mast that's 52' from the water, or about ~47' or so from the deck. I'm referring to a port to starboard measurement. I'm not looking to change my rake.

[MJH]

Originally Posted by Kabunza

I need to tune my mast which includes straightening it athwartships. My mast is keel stepped with a chock wedge at the deck providing little play. What’s everyone’s opinion regarding straightening the mast, whilst leaving the mast chock in place?

Remove the chock wedges (these are called "mast partners") at the deck then tune your mast. Replace the "partners' when you get the mast where you want it. Use a mast boot over/around everything to prevent leaks.

~ ~ _/) ~ ~ MJH

[Kabunza]

Thanks Guys!

[BillKny]

I hate to be a spoil-sport, but the advice you have gotten so far is NOT correct.

The chocks NEED to be in place while you tune the mast. They act as a fixed point and the mast bends both above and below them. The chocks set the RAKE of the mast, while the bend (if any) is set with the tension of the stays.

Since you have already confused the issue of PRE-BEND with RAKE, I strongly suggest that you get a book on the subject and read it carefully so you actually unserstand what is happening and why. Either that or find a professional rigger who knows what they are doing.

It is very likely that your boat would be best with a bit of pre-bend aft, which is separate from rake. Talking to people very familiar with your boat is a good start, or your sailmaker. Your sails were cut for a particular amount of bend in the mast, and you need to duplicate that for the best sail shape.

For books, if you really want a deep dive into the topic, you can't beat the late Brion Toss' Rigger's Apprentice. Truly comprehensive, but probably more than most sailors need to know.

If you'd prefer something a bit lighter and quicker but still excellent, Ivar Dedekam's Illustrated Guide to Sail and Rig Tuning is a great choice. It is one of the best how-to guides for sailing ever written.

[George DuBose]

Skylark, a 1973 Pearson 36-1has a mast that has walls that are so thick I can't even think of trying to bend it. One of my sisterships installed a hydraulic back stay adjuster and wound up ripping his bow fitting off the deck while trying to bend his telephone pole, I mean mast.

I once couldn't get the four 1/2" pieces of rubber that were the mast partners that came with the boat all in, so I used wooden wedges. They made a cracking racket all summer. Out they went and I went with SparTite.

There are rubber mast partners that are stepped wedges to simplify installation, if one doesn't want to use SparTite.

Hall Spars has a .pdf that has good instructions about tuning the rigging.

[Kabunza]

Thanks George.
I've read a number of rig tuning docs and it's amazing how many mention stepping, but leave out that the partners/chocks/wedges shouldn't be inserted at this stage...hence my post.
I'll need to deal with this next Spring when I have more time and better weather, since I'll need a full weekend and another hand.
While I'm at it, I should check the spreaders.
Really disappointed in the rigger I used. Just another reason why I've learned to work on all the other 'systems' my self, ie: diesel, electrical, etc.

[Scaramanga F25]

BILLKny is correct.
Hard rubber or soft wood tapered chocks must be around the mast at deck level. if mast is leaning to port side you will need to ease the port shrouds and tighten the starboard shrouds. To do this vertical centering of the mast make sure your boat is level at the waterline when you are by the mast verifying its verticality. Use a plumb bob attached to a thin line hoisted to the top of the mast. Use the main halyard for this.
You will then see the bend and/or off the vertical so adjust your shrouds accordingly.

[Manateeman]

Bill K is spot on. Brian Toss was a great guy and if you read these two books you will understand rigging. I’ve seen people actually bend the spar permanently so just be careful. Make sure the boat is level...just your weight can change things.
Stores, tanks, anchor chain, dinghy. People forget heavy items. Mr. wind too.
Happy trails to you
Mark and his pine tree mast manatees.

[Kabunza]

Thanks To those of you who read my initial post and stayed on topic. Sounds like the general opinion it to remove the chocks when straightening the most post/starboard. (I'm not looking to adjust rake. Yes, I know what rake is. LOL.)
It's a shame to start over since it was only a few months ago I paid for a 'recommended' rigger only to discover, as I learned more about rigging, that he did a poor job. The only good thing about that rigging job is that I have a new mast boot which fixed all my leaks. I think I'll wait for more dependable weather.
Thanks again.