View Full Version : mast building questions
08-05-2001, 11:29 AM
I've finally made the mast(10'8") for my 14' John Gardner skiff. I did the birds-mouth thing and, wow, was that slick! About an hour to mill the staves. Another half hour to do the tapers, a coat of cpes, then next day my wife helped me with the glue-up. I was kind of dreading this but it was a breeze. Then I planed it to almost round -- that was actually fun. Now my question -- what's the best way to do the final sanding. my brief attempt at the inside-out beltsander belt and drill with drum sander did not work. Bad technique? Sanding by hand works fine but is slow!
Next question -- What is the technique to put a sheave in the top of the mast. I don't think I've ever read a detailed procedure for that.
I made the mast from a green(not kiln dried) spruce staging plank that was carefully selected from a big pile then kept indoors for seveal years.(I inherited two sixteen footers from a friend). It came out straight and strong and beautiful.
Thanks for any help, Steven
08-05-2001, 12:11 PM
When I sanded the spars for my Nutshell I ripped off a strip of something like 80 or 100 grit crocus cloth, and went at it like a shoeshine boy. I didn't trust myself to the McIntosh power method, and it's good for the arms. It also lets your see your high spots while you're working on it. The crocus cloth is strong like a sanding belt, but more flexible.
08-05-2001, 03:04 PM
I can't describe the inside out sanding belt on a drum technique but perhaps you just didn't hold your mouth right. There is a trick and it takes a while to figure out how to get the belt to spin and then to move along the mast without running the belt off the drum. Once you pucker just right, dust flys and the mast gets sanded. Last time I did this I thought a bigger belt would be better. It isn't. A 3" x 24" worked just fine.
08-05-2001, 03:23 PM
Nice hat norm, we didnt get enough sun to wear such attire here this year, you still got both your hands, that thing looks damn dangerous? Still looks like a fine mast though!
08-05-2001, 06:17 PM
It's a lot easier to use if you build it in a bit more detail.
Mount the drum on a through-shaft. One end fits into the drill-chuck, while over the other (obviously a fair bit longer) you slide a loose handle. This lets you hold both ends of the tool while you operate it, relieving the load on one wrist and allowing you to keep the belt running in the right plane.
On the drum itself put quite a few large rubber bands, or alternatively glue on a soft rubber mat, to provide extra friction to grip the belt when starting. (And start off slowly, too.)
At each end of the drum, fit an angled collar made from sheet steel, cut and pop-riveted in a shallow cone-shape (like a rat-hitchhiker-stopper on a mooring line) to keep the belt running on the drum instead of sliding itself off as it rotates.
This sort of gadget povides by far the best way of finishing off a spar, I think, and gets used here for masts, flagpoles, boathooks, jackstaffs, and just about anything else with a circular or elliptical cross-section.
08-05-2001, 06:44 PM
Thanks Norm and Mike. I've got the mast about half sanded with Rich's shoe shine method but my arms are getting sore!
Any hints on the sheave at the mast-top. it's for the gunter halyard. Just drill some holes, connect the dots with the jigsaw and finish with a rasp or file? Or is there a better way. What do you pin the pully with? Can I buy the parts as a kit or just figure them out separatly?
08-05-2001, 08:04 PM
Well, I wasn't gonna tell you how I rigged for the sheave on the end of the boom and gaff 'cause I have no idea if it is good or not. But since you asked nice twice...
I bored a series of holes the diameter of the thickness of the sheave and sawed out the rest. Took a course rasp and smoothed the sides and finished with a finer rasp. Then drilled a hole for the sheave shaft, tight fit and tapped it in. Friction fit after all the googue and varnish was added. I sort of wonder if there shouldn't be some metal reinforcement of the shaft hole. Guess time will tell.
Trouble with Mike's scheme of running the shaft all the way through the sanding drum is it takes most of the work out of the job. Keeping the pressure on the way I did it is a chore.
08-05-2001, 09:59 PM
For a skiff you should probably go with a "dumb shive" Cut a slot in the mast and epoxy in a block of wood to simulate the upper half of a shive. Line it with a strip of stainless steel.
08-06-2001, 04:07 AM
Steven, I think Syd's probably got the right idea. You don't really need a proper sheave there. Just cut the slot they way you and Norm have suggested, and round the bottom half of it into a semi-circle for the halyard to run round. (It wouldn't really matter if you didn't line it, even.)
But if you wanted a proper sheave, then as Norm says, make it a nice snug fit in the mortise. You need to be quite sure that the halyard can't jump off the sheave and jam down alongside it.
I must confess that Aileen Louisa came with a dumb sheave for the main halyard (which was quite satisfactory,) but I put a little bronze sheave up there myself, just the same. Or you could turn up a hardwood one, or buy a tufnol one or even (dare I say it) a plastic one, I suppose.
For the pin, you could use a bit of 1/4" copper, or bronze, or ss, and either thread it each end for a nut, or rivet it on top of a washer/rove. If there's enough timber left in the mast, you could drill from one side almost right through (stopping just short of the far side,) make the pin shorter than the full width of the mast and insert it from the other side, then plug the hole so that nothing shows on the masts's surface. Being a lazy sort of chap myself, I just used a brass through-bolt.
The mortise should run side-to-side if you're using a gaff, yard, or sprit (I've forgotten what rig you've got, if I ever knew.) I found a spade-bit took out the bulk of the timber nice and fast.
Of course, all this assumes the existence of a nice solid plug in the right place of your birdsmouth mast...
[This message has been edited by Mike Field (edited 08-06-2001).]
08-06-2001, 12:00 PM
I sanded my Nutshell spars by hand. The key is to use the right grit paper. If you start with 60 or 80 grit of a good quality paper, it will cut very fast and you will take the mast down to round in no time. Move on to 120 and you'll be all set. You can't beat the feel of hand sanding for getting it perfectly round with no high spots.
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