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Cutting the Mast Foot


mikiek
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There's bound to be a simple way to do this. The MS Niagara plans say to cut an octagonal foot and a matching brace. I think all the pix I have ever seen show rectagonal foot as wide as the keel with the braces being just flat scrap glued on each side of the keel notch.

 

Either way, how do you get a nicely centered, even cut on the dowel?  Firstly how do you measure it out and secondly how do you cut it?  Inquiring newbie's want to know.

 

I imaging I'll just go for the rectagonal cut, but I'd like to know how one would get an even sided octagonal foot? If I am not mistaken, there are several parts that are called for being octagonal.

Edited by mikiek
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It's far easier to start with a square sectioned spar, then cut it octagonal, finally rounding off the areas where the spar is circular in section. That's the way real masts and spars are made, not turned. 

 

To mark out the four square to make it an octagon, each side is marked across 7-10-7 proportionately. That is to say, each face is divided across into 24 parts and lines set off 7 parts in from the edges. Place the four-square stick in a 45 degree holder or jig and plane or chisel down to the marked lines. From there it is easy to round off from octagonal. (In the shipyard, the mast was planed 16-sided first, then rounded, but for model work this step can be skipped.)

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You may be giving this more attention than it warrants.  I take it that this is a fully planked hull with the keelson essentially not really visible?

Saying keel notch - this is POB with no keelson at all? 

 

In POF there would be a mast step on top of the keelson - or assembly of sister keelsons - depending on ship size and how serious they were in resisting hogging.   Most mast heel tenons were square it seems.  The mortise in the mast step would be square. I can see where an octagonal tenon and mortise would be easier to allow side rake adjustments.  Your kit is not designed for this level of detail.

 

You imply that you are going to use the dowel that comes with the kit to make the mast.  If you were shaping the mast from split out straight grain stock, I could see maybe paying attention to what a hidden mast heel tenon might be.  In your situation, centering a hole in the heel and mounting a cut off 6 P or 8 P nail with the point out should be sufficient.

 

Just making a hole in the plywood center spine to receive the nail point may not be a stable support.  You can use a solid piece of wood on top of the keel spine to receive the nail.  Getting it square to the edge of the plywood is difficult , is too narrow and is not stable.  Make the mast step at least 3xs wider than the keel spine.  Either cut a mortise in a thicker step to slip over the spine or glue lateral supports on either side of the spine.

 

You will need to adjust the mast length to compensate for this assembly.  Either cut off a bit of the dowel, or notch the mast step assembly down into the keel spine.

Edited by Jaager
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Jaager - this is a POB kit. I am about to start on the deck and need to at least get the scrap wood glued to what I was calling the keel notch. The instructions actually call it the mast slot - my apologies if that was confusing.

 

I don't need to do the mast yet but I want to get the wood glued to the mast slots before I forget to do it. Due to that I need to decide whether to go with an octagonal foot (per the plans) or a rectangular foot (what most seem to be doing). If I go octagonal then the slot side pieces will be different to accomodate the additional sides.

 

You are right when you say it will end up hidden under the deck, and personally for the foot I couldn't care less which way I go. My biggest concern was how to cut a nicely centered and even sided octagon or rectangle in a dowel. As druxey states I really should start with a square beam rather than a round dowel. The plans call for the mast to start out octagonal, then round, then octagonal so learning to make this cut is something I need to do. At the moment I just don't know how so I am asking for help.

 

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There is a problem with using a dowel as starting stock:  it is hit or miss with the grain being straight,  luck mostly.  Over time, the wood will seek equilibrium. If the grain is not dead straight, the dowel will bend.

 

The way to avoid this - split out mast and yard stock from a board of a species of wood with straight grain and plane it down to shape the mast.  A lot of basic books on ship model construction have instructions for doing this. 

 

If you are not intending to immerse yourself in this ship modelling endeavor, you can cut a square tenon for the mast heel - close enough is good enough to start - you can always file away, or glue a scab when doing the final mast mount.

 

As for cutting the tenon,  micro saws, small back saws,  needle files , Xacto blade chisels, or if you want to invest: palm chisels will do the job.  When I started, I knew nothing about wood working or the tools involved.  This is a way to learn.

 

One factor to consider at this point:  The farther down in the hull is the heel of the mast,  the less profound will be the effect of mast wedge adjustments at the deck level when doing the final positioning of the mast. You will have more room for play.

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Mostly theory on my part. 

Beginning with old school/traditional :

I have more Pau marfim than I realized - and it is good that I got it while it was available, but most any reasonably hard straight grained species should do. 

When I first started, Yellow Pine was a suggested species, the thing is, Yellow Pine could be one of several species of pine.  I asked my grandfather for some ( he was home builder )  and what he gave me was a plank of what might be an all but extinct species of pine with distinct grain that is fairly wide and the summer wood is really hard. There was a species of pine that was widely used before WWII - very hard - too popular and all but lumbered to extinction.  What I have may be that - turned up, it looks like a made mast.

 

Now,  Birch is great, but the machines that punch out the dowels, do not place a high priority on being dead on with the grain, so starting with a plank is better. 

In working with it, I think Hard Maple is a good choice. 

It takes more work, but I am partial to species that are hard. 

In Texas, you may be able to find a Yellow Pine that is straight and hard.  I think that what is used for framing lumber is not going to be useful.  The flooring stock may be useful.

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I'll bet the pine your grandfather gave you was longleaf pine. It was a great wood for construction and it was all but decimated years ago. It was not replanted because loblolly and slash pine (what gets sold as yellow pine) grew a lot faster.

 

Birch or maple should be pretty easy to come by at the big box stores. I'll just inspect the grain and get what looks best. Definitely something I can rip down to a suitable square beam and start from there. I may actually have to pull out the table saw. :D

 

Thanks to all for your comments!

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Is there any rule of thumb regarding what size to start with? For instance the main is a 3/8 dowel. If I start with a square beam what size should that be? I realize just about anything bigger than 3/8 x 3/8 would work, but I'd rather not be whittling for the next month.

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Check your plans for the actual dimension of the finished mast, and then depending on how much 'slop' you think you need, get square stock appropriate to that size.  If the kit provides a 3/8" dowel, that doesn't meant that the largest part of the mast is actually 3/8".  It might be, but the only way to know for sure is to check your plans.

 

When I ordered my boxwood, I went about 1/16 or 1/8 over (depending on dimension of the final piece), but I was also using a lathe to shape the masts from the square stock, so step 1 was simply to turn the square stock into round stock just barely larger than the largest diameter of the mast piece according to the plans.  Doing it by hand I might have tried for a much closer starting size.

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Canute - this has been very helpful. Sadly I am not having an easy time pulling the mast measurements out of the plans. In general, is it possible that the diameter of a finished mast might be larger somewhere than the dimension of the mast slot in the keel?  Hope that made sense.

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If your plans are to scale (i.e. 1:1 with your model), then you pull the measurement off the plans by simply measuring off the plans.  Good plans will actually have a note on the max diameter point, but if not, just use your calipers and take a measurement.   

 

As Joel said, the widest point will be at the deck, but some masts don't begin to taper immediately, and may stay that diameter for a few feet above the deck.

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While the mast being thickest at deck level, is true for most ships, be careful, on smaller ones at least.

 

The plans for the Chesapeake Bay skipjack (a 30 to 60' sail powered oyster dredger) I am working on, and another in the wings, both are thickest a couple feet above the deck, then start the tapered octagonal shape as they go toward the foot. They are about 1" narrower when they enter the deck.

 

I don't know if there are any others where this happens, it might have been a regional thing.

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