Mast alignment in mast partner
 

I had my rig down all winter and it's been back up a month or so. I have a keel stepped mast.

I had a rigger come out and do the initial tensioning of the rig and the mast was just touching the partner on the forward edge. I loosened the rigging and worked the step back a bit and it all looked straight. I had the rigger come back out and now it looks a little to one side and still pretty close on the forward edge.

I wanted to use spartite on my mast but it seems like there so little clearance with the mast this way.

Should I be that worried about the mast being perfect spaces in the partner? I'm trying to figure out if I'm being too picky or if I should be loosening the whole thing up and going back to the crane to get this right.

Thanks,
-p

I live with wooden boats where sometimes things move and sometimes you want to move the rig about a little so:

You referr to 'mast step' but the place where the mast goes through the deck is the partners. The step is where the mast lands at the bottom. Many steps are absolutely where they are, period. But some have a little adjustment fore and aft via wedges or a screw.

Further complicating is that the scantilings for a deck stepped mast are usually a bit heftier than for keel stepped as the deck stepped lacks the support that comes from the partners.

Further, the partners give you a way to craft a bend in the mast that you can't do so interestingly.

We woodenboat types don't like poured wedges. We make wedges that fit the way we set the mast, which is sometimes a bit at varience with how the builder made the step to partners alignment.

I'm going to assume from your question that neither you nor your rigger has any interest or expertise in using the partners as part of bending the mast, so cutting to the chase: Brion has some excellent info on how to tune the rig. Do that on a nice day - breeze but not so much wave action that the mast pumps and you can do it with the wedges out. Get it right. Then wedge.

Gluck

G'luck

Ian thanks for the reply. Not sure what you're trying to say though.

Let's clarify some terms, maybe I'm using them incorrectly.
I have a fiberglass ketch with a keel stepped main and deck stepped mizzen.

The mast partner in the case of my fiberglass boat is just the whole in the deck. Maybe we should just call it the hole in the deck, but everyone calls it the partner. It is not adjustable. The maststep is adjustable it's aluminum sitting on a UHMW block and has four lag bolts into the keel.

For those playing along at home here's traditional wooden mast partner:
http://www.aandc.org/research/mast_partners.html

I'm talking about the fore/aft placement and twist of the mast as I can see it where it goes through the mast partner (AKA the whole in the deck). After the tensioning of the rig and measurement to make sure the masthead was centered the mast is pulled to one side in the partner, a tad twisted and is definitely pulled very far forward in the partner; 1/8" from touching.

I'm just trying to determine if I should be worried about the mast placement not being centered in the partner (aka hole in the deck) or is it not a big deal.
I also assume that if it does need adjusting it's not through the wires, but through getting the maststep into the right place.

Thanks,
-p

I don't worry much about fore and aft centering at the partners. But if you have an adjustable step, you ought to be able to reduce or eliminate any asymetry there as desired.

Failure to get athwartships centering there could well indicate a subtle bend to the mast. I've always taken that out by wedging. You can't do that with poured stuff, only real wedges made for the purpose.

Before deciding, I'd check the scantlings and the rig design - staying and all. On many boats no weight advantage is taken by having keel stepped and the mast walls are just as hefty as deck stepped masts need to be. This may be to achieve extra strength or because of what's out there on the extrusion market or builder indifference or rerigging along the way.

Do you have a mast and rig designed to take a bend, or is your main (I'll ignore the mizzen for now) really designed as a straight column? Even if the latter, I'd be inclined to force athwartships symetry at the partners if I was dead certain that the hole and step are both themselves perfectly centered. It'd hard to see a subtle curve but there have been columnar masts where I could sight from the step through the partners and see a curve. If it came out with a bit of creative wedging, that was nice. In other instances, the tune was right even though the mast leaned against the foreward side of the partners hole. If no adjustment in the step, I'd wedge it thus.

Part of my prejudice about poured wedges is the nightmare they cause in stepping and unstepping. Most boats with aluminum masts (parallel sided extrusions in that area) also have parallel sided partners. So getting things in an out is a royal pain. One boat that was a constant horror I finally solved by shaping a very subtle taper into the partners such that the poured wedge only got really firm when gently tap-seated after the mast was in the step. Comes out more nicely as well.

G'luck

Ignore the partners
 

The two important points when initially setting up a mast are the top and the bottom. You can't move the bottom side-to-side (generally), and you want the top centered. You want the rake where the designer intended, or somewhere different if you are curing a balance problem. Very few partners will be centered on the mast in either direction on a production glass boat, just don't worry about that. Most glass boats will have some taper at the partners (called "release" in mold making). Spartite is used all the time by folks that frequently step and unstep their masts.

The original question had to do with whether it is a problem if the mast is not centered in the partners. It may be that the mast is in the right position but the boat is not perfectly symmetrical--few boats are, particularly older boats. If the mast is positioned and tuned as well as you can get it, I wouldn't worry much about its position in the partners.

Jim Fulton

Thank everyone... I tend to be a bit of a perfectionist especially when I'm writing checks. I'm more foregiving of my own work.

I'm hopeful that in a couple years I'll be able to answer a few questions instead of just asking. ;-)

Thanks again!
-p

Euler
 

Hello,
Great discussion. I would just like to back up a bit, maybe fill things in.
First, the whole reason that you have a keel-stepped main is so that you can have a lighter mast than if it were deck-stepped. With the mast firmly secured (wedged) at the partners your mast can be at least 40% stiffer than a deck-stepped mast of the same dimensions and material. This also means that if you put a real tune on the rig before the wedges (or Spartite) are in, the mast, if it is of proper size, will want to buckle from the compression loads, and you won't be able to keep it steady at the partners. As always, I recommend that you run the numbers on mast scantlings, but the very fact that the mast wants to bump up against the partners is a good sign.
That adjustable step is a great thing, since it means, as someone else pointed out, that you can get a fair curve right from the bottom of the mast. Ideally, you should be able to set your rake, get the mast centered laterally, move the butt aft an inch or so, wedge the partners, and then put a real tune on.
The partners might indeed not be centered in the hull, something you can discover with measurements. Or the mast step itself might be off-center. What matters is that the mast comes up vertically, whether or not it and/or the partners are centered.
It might seem that the partners aren't big enough to give much adjustment room, but remember that a little move at the partners can translate to a big move at the masthead. It can also make a big difference in the amount of bend you can get. We typically put the mast well forward in the partners, for the sake of easy bending. Whether using wedges or Spartite, you'll need enough space forward of the mast that the wedge or rubber isn't too thin.
As you can see, this stage of things is quite fussy, at least if you want to get the most out of your rig. Be in touch if you'd like a visit.
Fair leads,
Brion Toss

Spartite sequence for keel stepped
 

Brian.

The spartite I removed from the single inline spreader, keel stepped, mast head, cutter rigged aluminum 52' spar was a mere 1/8" thick at the leading edge and 1" at the aft end. I moved the maststep aft 1/4" with the idea that would help to provide slightly more thickness and now in the process of replacing spartite. Having read your post about keeping the "butt" as far fwd as possible, perhaps that wasn't such a good idea but 1/8" just seemed so thin. Of course, now the teak and holly boards in the cabin sole don't fit (1/4" gap - no surprise there). Clearly I didn't think that one through!

Is it really possible, or recommended, to drive (or to quote Hall Spars, "finesse") the butt forward without a crane if the rig is slackened off?

Q. When preparing to spartite, here are the steps I understood from your post?

1. Lateral tune to center mast in boat with an effort not to bend the rig. So commence with a loose (hand tight?) rig. Adjust using uppers (caps) to center mast head with respect to top of chainplate or gunwale on each side?
2. Adjust rake using forestay and backstay without adding bend( are lower shrouds used at this point?)
3. Don't stress about being centered in the partners. Hard one for me to adhere to but I'll try.
4. Spartite or wedge and allow to cure.
5. As you stated above, now put "a real tune on the rig".

So if i understand correctly, the compressive loading and pre bending is not added until after the spartite is set in the partners?

Thanks for the help.

James

Details
 

Either I misspoke at the time, or you misunderstood -- or both -- but here's some clarification:
Moving the butt of the mast aft at the step is done either to change rake,or, as in this case, to help induce bend by starting it at the keel. For bend, the butt at the mast is moved aft, and the mast at the partners is kept forward. By moving the butt aft, if that is what you did, and also moving the mast aft the same distance at the partners, you have preserved the previous shape, while providing more bearing thickness in front of the mast at the partners. Nothing wrong with that.

Yes. Asterisk. Some masts are more reluctant to move than others, because of step stickiness and/or a shortage of places to brace against or pull on for the finessing. But again, if better bend is your aim, you want to finesse the butt aft.

Yes, lateral tune, but start by using the lowers, not the uppers. Once the mast is centered down low, you can sight your way up to the top, using the uppers (and intermediates if any) as you go.

Yes, to set rake. Later, you will use the stays and shrouds to set bend.

Rather, don't stress about the partners if your measurements show that the partners are off-center. Get the mast on-center, and if the partners are, too, it's gravy.

Not quite yet. This is where you induce some desirable basic bend; the Spartite or wedges will confirm and keep that bend. Whether or not the bend will be adjusted under way, go for a median shape.
5. As you stated above, now put "a real tune on the rig".

If you add too much compression before securing the mast at the partners, it will get squirelly; just tune sufficient to get the shape you want, then wedge. Later, you can add tension without changing the shape.

Thanks for the help.

James[/quote]

I have far exceeded my "too short to charge for" rule here, so if you need more details, let's set up a consultation. Meanwhile I hope this all helps.
Fair leads,
Brion Toss