mast wedge?

[nobby]

goodday all,recently bought my 1st wooden boat a 27 foot king billy pine(tasmanian native) am unsure as how to repair 1 inch gap between mast and roof where mast passes through,should it be wedged,round or square etc.etc.have been trying to find stuff on net but no luck as yet,any ideas.also need to know the basics of marine ply,ie need to fit a new section of roof as well with a small radius maybe up to 3 inches over 4 feet, what should i use 5/ply 7/ply etc,also paints/sealers it seems to be a pretty wet boat but we are just finishing winter .thanks

[ 09-11-2005, 02:05 AM: Message edited by: nobby ]

[westinghouse]

"1 inch circular hole on coachroof where mast passes through"

That can't be right, it'd have to be port or starboard, fore or aft. D'you mean plug a hole in your coach roof?

[nobby]

sorry should of said 1 inch gap around mast and roof

[ 09-11-2005, 02:07 AM: Message edited by: nobby ]

[paladin]

normally use wedges to adjust mast and then boot to seal.....

[nobby]

so it should be a square hole it is currently circular? and what size sould wedges be,i may have to beef up the roof as well

[ 09-11-2005, 02:18 AM: Message edited by: nobby ]

[Hwyl]

The hole should be roughly the same shape as your mast, just larger dimensions.

Set up the rigging to where you think your mast should be (don't worry if the mast is upright and square but not concentric in the hole, that's often normal. Wedges can be strips of hard rubber banged in there or literally softwood wedges. They should protrude about an inch or so vertically. Again, don't sweat this, the (by far) most important thing, is to have the mast in the right place.

As Paladin says, when you're satisfied that everything is set up right, make a boot to go over the lot. I usually make one out of inner tube rubber, fastened on with hose clamps/jubilee clips. Then make a fancy canvas one to hide the monstrosity I created.

This is kind of an important set up. You might want to ask some of your neighbours to give you advice or even a hand.

[lagspiller]

You can use anything that doesn't damage the mast to wedge it. Blocks of soft wood are fine. Just trim them to shape so there are no edges to cut the mast or cabin top.

It is important to wedge the mast. It makes it much stronger against breakage - gives the mast a double torsion (like an S) instead of a single bend (like a banana) under sail pressue. So slight you obviously cannot see it, but that is how it works.

There is other good info about tuning your mast at this site. It is for a Dragon mast, but most of it applies to any through-cabin mast.
Mast tuning by North Sails (http://www.northsailsod.co.uk/tuning/dragon-tuning.html)
tom

[Ian McColgin]

A mast designed to be keel stepped and properly wedged at the partners (structure on the inside under that hole in the deck or coach roof) are a bit lighter than masts designed to be deck stepped. So it always horrifies me when people have a couple of wedges or use approxomatly fitting untapered rubber bits.

It it's rubber, it will not tap in properly. Wood is the choise. It matters little whether it's hardwood or softwood in the biological sense but you want wood that won't crush too much and/or radicaly expand with water, like some cedars, and you'd not want something so tough that it will hopelessly dent the mast if you over-tap a little.

I think it worth the time to make nicely fitted wedges. This means on a round mast, you'll want to concave round the inside surface and convex the outside. Obviously, the more wedges you have, the less work on any individual wedge.

Prior to stepping the first time, have a bunch of blanks that are tapered from maybe 1/4" smaller than the average gap to 1/4" larger. This is a tad extreme unless you make them really long - like about 2x as long as the verticle space deck top to partner bottom.

The mast should be centered athwartships when you get first tune but is probably not centered fore and aft. No sweat, Start at the front and drop, not tap, wedges all the way around, nicely cheek by jowel.

Go below and look up to see if any wedges are just grabbing at the deck level and not making contact more along the whole depth of the partners. These might be tapped out one at a time and planed a bit flatter for a nicer fit.

Now go around and gently tap each wedge in turn to get them down where they want to be.

Now, starting with dead forward wedge and running around clockwise as you look down (unless you live in the Southern Hemisphere) use an indelible marker to put the number of each wedge on the outside surface just above the deck rim.

The wedges may be very uneven at the tops and bottoms. Mark a line for cutting maybe an inch or so above the deck ring (don't cut off the numbers!) and below the partners to trim it up. Only the upper line is really important and only then if the boot you'll be making is not tall enough to clear the highest wedge.

There are rubber step shaped boots that can be bandclamped in place. Quite lovely on a tupperware vessel. On a wooden boat, they allow vapor to condense inside, trailing back down into the partners and wedges getting rot started if at all possible.

Make a nice canvass boot and you'll be looking cool. It will really shed water if it has a nice smooth and steep form, and will even keep deck sweeping wave-water out. We will chime in with much gratuitious advice when you are ready.

G'luck

Edited to add: When I made new wedges for Goblin's two sticks, after repairing rot in the masts at the partners in part caused by improper wedging in years before I had her) I gave each wedge a lip on the outside just above where the wedge would set down to. That way after the crane got the mast into the step, I could just drop the wedges in in order and the mast would be in place. No need to tie up costly crane time with getting some rigging up before going on to the other mast and then releasing the crane.

[ 09-11-2005, 08:32 AM: Message edited by: Ian McColgin ]

[lagspiller]

Best advice I seen yet.
I was going to mention the problem with boot-tops and rot also. From experience, unfortunately. Luckily I understood what was developing and completely dropped it to get max air circulation. The little water that came in was better than the chance of rot.
Of course, that is on my boat - stripped down internal. Nothing to get soggy.

[kc8pql]

Ian et. al. How much bigger should the partner hole be than the mast on a larger boat? Mast is 71/2" dia. at partners.

[Hwyl]

I politely disagree almost totally with Ian. I wish i could do it over a cup of coffee(I do like his politics however). The time to make fancy wedges is when your boat is laid up and you are certain the mast is in the right place. In the meantime, just make any old wedges, I agree surface area is important. The chances are that once the mast is up, you'll wnat to adjust the rake, to correct weather or lee helm. Pull all the wedges, adjust the turnbuckles/bottlescews. Take your old wedges to the bandsaw and refine them to where the mast is now. When you're certain it's right, anfd you have a few spare hours, by all means take Ian's advice and make fancy wedges. By the way, rubber is fine and some movement is O.K. too. I've sailed many boats with wooden masts and rubber boots, worked just fine. I hate it when rain leaks inside a boat.

[ 09-11-2005, 07:47 PM: Message edited by: Hwyl ]

[nobby]

thanks all,now i know where im going,chainplates is 2x 3/8 bolts enough ?they go thru timber where deck meets top of hull which is called?????? it appears to be 2x2 and all ribs join into it.any sites which explain and show correct terminology would be appreciated "partners",and i dont mean the wooden mast bracing types.

[Ian McColgin]

If you mean chainplates are just eye bolts, you may have a real problem on all but the very smallest rig. Send particulars or pix or check local smart folk. Generally the ring in ring bolts is not strong enough for rigging strains and the depth you can burry them is definatly not enough. Chain plates are indeed plates going at least a few planks down and are bolted in so the bolts take a shere, not pull. Sounds like you have bolts let into either the "shelf" or "clamp." Some boats have one or the other and some both. There are lots of good building texts available through our sponsor's WoodenBoat Store that will give details.

Hwyl and I do not really disagree. Lots of wedges reduces the need for hugely hollowing and rounding fewer wedges. It all can go quickly and extra long parts can be trimmed even in situ. I think the difference in emphasis is from two places. I was trying to describe the whole process to the very cool labled wedges you'll use year after year, hand down with the boat to grandkids, and all that. Also and more to the point, I got in the habit of planting the sticks and wedging them before setting up the rigging. This was partly because I often worked alone but even with help it's nice to get the masts to stop slatting about and get the crane on its way or clear the gin pole or whatever as quickly as possible.

There can be quite a difference between the for and aft parts of the gap which may require different sized wedges. You'll learn by making which is why I recommend the first set be way too long, allowing them to be either higher or lower depending on whether the gap at that spot is narrower or thicker respectivly.

I made the sholders because Goblin's mast could really slat about before at least the cardinal wedges were in and I got tired of going below to fish the fallen wedges from the bilge. But that's a grace note, not a necessity.

If the gap aft is only a little smaller (unlikely to be larger) than the gap forward, you could actually want to have even wedges and induce a little arc in the mast down there. It depends on what you're doing to shape the rest of the mast. But most of us on traditional boats like to keep that luff line straight and do the sail shape tweeking without torquing the mast.

Quick on a canvass boot. Hopefully the deck around the mast slot has a raised lip that's got a little rim at its top, even a little concavity of the verticle face will do and this you can put in with a round file in about a minute if the thing is flat.

You want an exact measure of that circle and an exact measure of the mast at the height of the boot top. If you call the mast diameter "one" unit, the boot height should start at one also, adjust to suit your eye.

Make a template by striking a line on your paper and swing two arcs from the same point on that line across the line "one" unit apart. Measure out the deck ring circumferance on the arc further from the arc's center, and the mast circumferance along the closer. Draw a line from the cars' center through each end. Cut along the arcs and the lines where they connect the arcs. Locate this around the mast and deck ring and fiddle with more templates till it suits you.

To make the semi-final pattern, add about 1/2" to the upper part of the template, not following the end lines but running parallel to the center line.

You can make the boot out of one piece but it's wasteful of material and the weave of the fabrick will not lie correctly. Fold the template in half such that the two straight lines line up. Cut on the fold and do that again with each half.

Now you have four pieces that can be laid on the fabric with the warp nicley verticle. Before you cut, remember to allow fabric for your sewing.

A lot of traditional round masts taper from the partners down to the heel. If this is the case, you may be able to fit the boot with only minimal top sewing before stepping.

If doing in situ or no taper, sew the pieces together but do not finish the last seam. Put the boot around the mast pointed up, inside out. Make sure that the place where the side seams go from converging to paralell (about last 1/2" or so) is right where you want the boot top.

Stitch her up.

Sieze from that convergance point down to the end of the boot. Now fold it down so the siezing is hidden and work the bottom of the boot over the deck ring. Sieze it and sail.

Some varnish the boot, but this deterrs evaporation. Spray some silicon water proof goo at it or shellack it.

G'luck.