Re: Build again!
Taper is easy. There are two methods: a 'shooting board' jig using a
hand plane or belt sander, or a taper jig on the tablesaw. Both jigs
are similiar.
The shooting board I made is from strips of 1/8 ply butted together
and nailed to the side of a long bench (a well braced and supported
4x4, with one flat face, would probably do), and as long as the
taper. Mark off a baseline and station points on the jig as per
plans, figure the width the stave needs to be at those points
(circumference/2.5 for eight stave spars) spring a batten through the
points, and trim the jig to the line. With the jig nailed to the
side of the bench, and the basline level with the top of the bench,
slip a stave up next to it, and trim it to the shape of the jig.
The staves are so narrow, the wood is clear and the grain is
straight, that trimming them one at a time is a snap. Any block
plane with a reasonably sharp blade will do the trick. I made a 12
stave birdsmouth mast and trimmed 4 staves at a time. It was still a
snap. There was 10 foot of taper on my masts and with the jig set up
it took about an hour and a half for all 12 staves.
The tablesaw taper jig is essentially the same. The stave is laid
against the tapered jig, and the whole 15' thing, if that is the
length of your taper, is slid through the saw. The difference is
that if you want curved taper in the mast, the jig has to be cut with
the taper concave to the blade. The easiest way to do this is to
start out with two exactly parallel faces on the jig, and use the
baseline, for measuring out taper, as the edge nearest the blade.
Now you have to figure out a way to hold your stave flat against the
curved face of the jig as you push it through! Most taper is so
slight, especially when divided between all the staves, that a long
stip of tape might do the job. Alternatively, you could just
cut the taper straight.
As an aside, birdsmouth staves are so narrow in width that you can
cut the scarf joints using the table saw with a taper jig
Is that any help? If you have spruce, you are lucky man. Use it.
Finding quality clear stock is half the battle. You will be amazed
at how little of it you will actually need for this mast, and how
easy the mast will go together. And when you are finished, you will
have a spar that will last a lifetime, no fear of delaminating, no
wondering if it's as strong as it needs to be. You have to go to some
pretty expensive, high tech laminates before you approach the
strength/weight quality of good wood. Wood is a while lot stronger
for its weight than you might think it is. Read Dave Gerr's 'The
Nature of Boats'. It'll open your eyes.
John O'Neill
PS, you'll want to cut your staves so the grain runs vertically to
what will end up the outside of the mast. Not for any engineering
reason, but just so it'll be easier to trim off the excess wood after
glup up, and will look better to boot.
hand plane or belt sander, or a taper jig on the tablesaw. Both jigs
are similiar.
The shooting board I made is from strips of 1/8 ply butted together
and nailed to the side of a long bench (a well braced and supported
4x4, with one flat face, would probably do), and as long as the
taper. Mark off a baseline and station points on the jig as per
plans, figure the width the stave needs to be at those points
(circumference/2.5 for eight stave spars) spring a batten through the
points, and trim the jig to the line. With the jig nailed to the
side of the bench, and the basline level with the top of the bench,
slip a stave up next to it, and trim it to the shape of the jig.
The staves are so narrow, the wood is clear and the grain is
straight, that trimming them one at a time is a snap. Any block
plane with a reasonably sharp blade will do the trick. I made a 12
stave birdsmouth mast and trimmed 4 staves at a time. It was still a
snap. There was 10 foot of taper on my masts and with the jig set up
it took about an hour and a half for all 12 staves.
The tablesaw taper jig is essentially the same. The stave is laid
against the tapered jig, and the whole 15' thing, if that is the
length of your taper, is slid through the saw. The difference is
that if you want curved taper in the mast, the jig has to be cut with
the taper concave to the blade. The easiest way to do this is to
start out with two exactly parallel faces on the jig, and use the
baseline, for measuring out taper, as the edge nearest the blade.
Now you have to figure out a way to hold your stave flat against the
curved face of the jig as you push it through! Most taper is so
slight, especially when divided between all the staves, that a long
stip of tape might do the job. Alternatively, you could just
cut the taper straight.
As an aside, birdsmouth staves are so narrow in width that you can
cut the scarf joints using the table saw with a taper jig
Is that any help? If you have spruce, you are lucky man. Use it.
Finding quality clear stock is half the battle. You will be amazed
at how little of it you will actually need for this mast, and how
easy the mast will go together. And when you are finished, you will
have a spar that will last a lifetime, no fear of delaminating, no
wondering if it's as strong as it needs to be. You have to go to some
pretty expensive, high tech laminates before you approach the
strength/weight quality of good wood. Wood is a while lot stronger
for its weight than you might think it is. Read Dave Gerr's 'The
Nature of Boats'. It'll open your eyes.
John O'Neill
PS, you'll want to cut your staves so the grain runs vertically to
what will end up the outside of the mast. Not for any engineering
reason, but just so it'll be easier to trim off the excess wood after
glup up, and will look better to boot.
--- In bolger@y..., "Harry W. James" <welshman@p...> wrote:
> John
>
> I missed earlier that you had made birds mouth masts for your
cartoppers. I
> have a lot of dry, fairly clear spruce and have given it a lot of
thought.
>
> The biggest problem is I haven't figured out how to do a 15' taper.
>
> I would appreciate your thoughts on this and a picture of your
round mast
> step as well.
>
> HJ
>
>
> jboatguy@c... wrote:
>
> > Bill,
> >
> > Have you considered birdsmouth? If you have a tablesaw it's easy
and
> > straightforward, and results in a superior hollow spar.
> > Alternatively, check out this site:
> >
> >http://catalog.com/bobpone/coldmoulded.htm
> >
> > It's PVC based as well.
> >
> > John O'Neill
> >
>
> _ _ _ _ _
> % Harry welshman@p...
John
I missed earlier that you had made birds mouth masts for your cartoppers. I
have a lot of dry, fairly clear spruce and have given it a lot of thought.
The biggest problem is I haven't figured out how to do a 15' taper.
I would appreciate your thoughts on this and a picture of your round mast
step as well.
HJ
jboatguy@...wrote:
% Harrywelshman@...
I missed earlier that you had made birds mouth masts for your cartoppers. I
have a lot of dry, fairly clear spruce and have given it a lot of thought.
The biggest problem is I haven't figured out how to do a 15' taper.
I would appreciate your thoughts on this and a picture of your round mast
step as well.
HJ
jboatguy@...wrote:
> Bill,_ _ _ _ _
>
> Have you considered birdsmouth? If you have a tablesaw it's easy and
> straightforward, and results in a superior hollow spar.
> Alternatively, check out this site:
>
>http://catalog.com/bobpone/coldmoulded.htm
>
> It's PVC based as well.
>
> John O'Neill
>
% Harrywelshman@...
Bill,
I am currently procrastinating about building my first boat. Your query
about fiberglassing PVC is of interest to me because I have been
thinking about laying a piece of pvc next to the chine before
fiberglassing in order to have a chase-way for wiring.
Mike Laird in the Pacific North WET!
Bill Wallace wrote:
... have any of you experimented with covering PVC pipe with fiberglass,
to get something stiff enough for a mast?
I am currently procrastinating about building my first boat. Your query
about fiberglassing PVC is of interest to me because I have been
thinking about laying a piece of pvc next to the chine before
fiberglassing in order to have a chase-way for wiring.
Mike Laird in the Pacific North WET!
Bill Wallace wrote:
... have any of you experimented with covering PVC pipe with fiberglass,
to get something stiff enough for a mast?