Wooden Mast Partners

[dwkentsr]

The inside diameter of my bronze mast collar is 8 1/2 inches. The wooden mast OD is 6 1/2 inches. The mast step is 6 inches of mahogany glassed to the keel. I am ready to build the partners ( beef up the underside of the deck), cut the hole in the deck and install the collar but I am concerned that 1 inch of play all the way around between the mast and the partners is too much. Should the collar and matching hole in the deck perhaps be 7 1/2 inch? I plan on using soft wood wedges with a lip that rests on the collar perimeter to fill the gap

Mast step https://picasaweb.google.com/1037251...41543135555858

Mast Collar https://picasaweb.google.com/1037251...66947373755730

https://picasaweb.google.com/1037251...66949191698098

Thanks
David Kent
www.bccrebuild.blogspot.com

[Ian McColgin]

No! The collar must be larger so you can get the mast in. Once in, you wedge it.

A lot of folk are very sloppy about their wedges, using any old splits and pounded in not even touching each other and often at such a steep slope that they only touch the collar at a small point which, if above the deck level, will just distort the collar.

Others like the new pour-in-place cast collar substitutes. I despise these but you can make them work with a wooden mast after a fashion if you slightly taper the collar inside. If you don't, when you go to strike the mast it will bind and the crane operator will be pulling the whole boat out on her stick.

Before you step the mast, mark in the area of the partners dead center forward and dead center aft with lines from a nudge above the deck level to down below the partners so you'll see those lines from above and below.

For your first time, get the stick up and stayed but not too tightly so you can see if the mast really comes up the center of the hole or is off a little. It's not actually bad for a wooden mast to put a little stress here so unless things are way off due to the hole being places a bit wrong (YES! That happens, with holes off a half inch or more one side or the other.) you can make the wedges symetrical, at least side to side. It's quite normal for things to not be symetrical fore and aft.

Measure the gap at intervals of between 1" to 2" depending on the wedge size you'll be making at top and bottom to see if there's taper and how it works. Then you're ready to make the wedges which could be sloped from a nudge over 1/16" small at the bottom to a bit more wide at the top. The wedges can be most any not too crushable wood but something with a really tight endgrain, like black locust, is really finastkind.

You'll want to hollow curve the inside and outside faces to fit, make the widest (oversized) part of the slope about 1/2" higher than a full fit, and put a lip on the outside so the wedge can't fall through the hole. As you put wedges in, start with your keystones, as it were, fore and aft centerline and then athwartships centered. Just drop them in, no pounding yet. Fill in till all your wedges are in and you have a nice fit around, only little gaps between wedges. Now you can gently tap to get them all happily firm.

Now number the wedges so you can get them right next year.

Since they are tapered wedges, just a bit of a tap from under will ease them out when it's time to strike the stick.

First time's the right time to number the wedges so you can get them in right the next time.

Nicely made wedges are a sign that the woodenboat owner loves his wooden mast.

G'luck

[allene]

My mast is 1 inch off to starboard so it sure does happen. I am told that it happens because someone measures 37 inches and says, OK, cut at 1/2 inch off of 18 inches and gets the 1/2 inch the wrong way.

In any event, my mas partners are fairly tight which I have been told is wrong. I have been told that they should not be tight so that the mast can move with expansion without being restricted. A small amount of space isn't going to prevent the partners from supporting the mast. My mast is spruce.

I would suggest you get this point clarified before making the partners and wedging them in as I did. That said, I have seen no ill effects from the say I have it so I have not changed it.

By the way, after 20 years of trying everything out there, the best way to seal the mast off is with high quality duct tape covered over with sumbrella to keep the sun off it. Nothing else worked on my square cross section mast.

Allen

[Ian McColgin]

Duct tape makes sunbrella redundant at best and can, if you're unlucky, cause the condensation that leads to rot at the partners. It's dirt simple to make a proper canvass mast boot.

[allene]

Originally Posted by Ian McColgin

Duct tape makes sunbrella redundant at best and can, if you're unlucky, cause the condensation that leads to rot at the partners. It's dirt simple to make a proper canvass mast boot.

It is not simple to get anything to seal against a square mast and having had rain water rot my mast step, I think keeping the rain out is very important. The problem is that the canvas mast boot will not seal on the flat sections and rain water will just run down to the mast step.

I am not understanding the condensation issue. If you have something that is water proof, how can it differ from another method that is water proof. Is that expensive silicon self adhesive tape, that doesn't keep the rain out going to be better for condensation than cheap duct tape?

I probably should have clarified that I formed a tapered boot out of sheet plastic then duct taped over that so there was only 1/2 inch or so of tape on the mast and that was about 5 inches off the cabin top. The tape did not contact the partners. I covered the plastic with tape then covered all of that with sumbrella which was keeping the sun off the tape. The tape degrades rapidly in the sun so the sumbrella is not redundant.

[Brion Toss]

[quote=allene;6099
In any event, my mas partners are fairly tight which I have been told is wrong. I have been told that they should not be tight so that the mast can move with expansion without being restricted. A small amount of space isn't going to prevent the partners from supporting the mast. My mast is spruce.
Allen[/QUOTE]

The partners don't support the mast; the mast, wedged, should be unified with the partners, in order to create an effective couple with the step. If it isn't, what you have is, to some degree, a deck-stepped-keel-stepped mast, which is to say one that might be 40% or so more limber than it could be. So you either need a heavier mast -- which is the case for actual deck-stepped masts -- or you have one that won't hold its shape.
Fair leads,
Brion Toss

[allene]

Originally Posted by Brion Toss

The partners don't support the mast; the mast, wedged, should be unified with the partners, in order to create an effective couple with the step. If it isn't, what you have is, to some degree, a deck-stepped-keel-stepped mast, which is to say one that might be 40% or so more limber than it could be. So you either need a heavier mast -- which is the case for actual deck-stepped masts -- or you have one that won't hold its shape.
Fair leads,
Brion Toss

So you are saying that what I have is correct in that the partners are snug with the mast and that what I was told is wrong?

[Ian McColgin]

To clarify terminology, partners refers to the whole structure of bracing around the deck or coachroof hole the mast goes through, collar, wedges and all. The hole needs to be large enough to get the mast in and out easily. The mast is then wedged nice and snug. As Brion explained, a keel stepped mast can be of lighter sections because it's held in two places.

On the boot, there are overpriced rubber boots that are nice for plastic boats with tin sticks. It's acutally easier to make a boot for a square or rectangular section mast - just four pieces - than for a round section that really works best with a six piece boot. That's the basic pieces, not counting a top and bottom bands.

G'luck

[allene]

Originally Posted by Ian McColgin

To clarify terminology, partners refers to the whole structure of bracing around the deck or coachroof hole the mast goes through, collar, wedges and all. The hole needs to be large enough to get the mast in and out easily. The mast is then wedged nice and snug. As Brion explained, a keel stepped mast can be of lighter sections because it's held in two places.

On the boot, there are overpriced rubber boots that are nice for plastic boats with tin sticks. It's acutally easier to make a boot for a square or rectangular section mast - just four pieces - than for a round section that really works best with a six piece boot. That's the basic pieces, not counting a top and bottom bands.

G'luck

OK, I found a nice picture showing what you said.


As for the boot, I agree that it is easy to make a boot for a square mast but I still assert it is more difficult to make one that keeps the rain out just because there is not a natural tension holding the sides tight against the mast. With a round mast, there is equal force all around the mast. With a square one, there is only tension at the corners. In other words, you can easily pinch the center edge of a square boot and pull it away from the mast. My bronze ring is rectangular as well, which doesn't help. The picture below still used some of that fancy self adhering silicon tape which I used before turning to duct tape in desperation. It leaked.

[Ian McColgin]

Especially for square section, I use a little "Shoe Goo" or their marine variation since it can be gotten off after a decade or so if the cloth wears out.

I have the boot inverted pointed up a bit higher than it will actually go - pays to practice and mark before any gooing. Pick up a bit of the edge against the mast and squeeze a bead of goo all the way around. Then start frapping from above (on the mast) the goo bead down so your squeeze out will be inside. Once that's completed, fold the bood down and into place to frap around the collar. The goo bead will keep the water from running in on the flats. Even on a round mast it's nice because with the boot folded down you have a cloth ring that tends to hold rain water against the mast and let it dribble unless sealed. Once running down the outside, it will be fine. Modern fabrics might be treated with silicon but natural cotton will swell.

G'luck