Re: navigator bird's mouth mast
5" is a tiny bit more than you need. I calculate that if the equivalent
wall thickness (as if the inside was round) is 15% of the diameter on a
birdsmouth mast, then the strength is about 76% of a solid mast, and
you have to add less than 10% to the diameter, to about 4.93" in dia. I
think if you just use some nicer (or at least stronger) wood (doug fir?)
you could just forget about it and keep it at 4.5". I saw some nice
clear doug fir, 1 X 4, in my local lumberyard when I was looking for
oar material. A bit too heavy for my purposes, but I wasn't looking to
make hollow oars. If you go to 5", I think your mast will be something
like 16% stiffer (if using same wood) than the 4.5" mast. The strength
goes up with the cube of diameter, and the stiffness with the fourth
power. It's possible that I might have fumbled the above, but the
results seem reasonable. I don't know what the wall thickness of the
birdsmouth mast works out to and have never even seen one, let alone
made one.
wall thickness (as if the inside was round) is 15% of the diameter on a
birdsmouth mast, then the strength is about 76% of a solid mast, and
you have to add less than 10% to the diameter, to about 4.93" in dia. I
think if you just use some nicer (or at least stronger) wood (doug fir?)
you could just forget about it and keep it at 4.5". I saw some nice
clear doug fir, 1 X 4, in my local lumberyard when I was looking for
oar material. A bit too heavy for my purposes, but I wasn't looking to
make hollow oars. If you go to 5", I think your mast will be something
like 16% stiffer (if using same wood) than the 4.5" mast. The strength
goes up with the cube of diameter, and the stiffness with the fourth
power. It's possible that I might have fumbled the above, but the
results seem reasonable. I don't know what the wall thickness of the
birdsmouth mast works out to and have never even seen one, let alone
made one.
>Jason Stancil wrote:
>snipBruces mast is 4.5"
>round will a birdsmouth of that dimension be strong enough? Or
>should i go to 5"......I'd rather err on the side of strengh. I'm a
>young guy and i'm not too worried about being able to step a 20'
>mast unless it gets over say 80lbs.
>
>5 staves at 2" width and 1" thick should be 5" round when assembled?
>i'll do a test run on a 2 footer before i go full size.
>
>Thanks
>
Jason said:>
(1) cutting tapers. take planks of correct length and width for
starters; mark taper tip + 1/8" on each end; connect the dots with a
straight line; cut 90 degrees on the line. Voila: two staves.
(2) cutting bird's mouth: on table saw, CAREFULLY set up first angle
of cut of bird's mouth out from under of bottom edge auxiliary fence,
testing for depth so that a 90-degree divot is removed. cut all
staves on first pass. Set up second angle similarly, cut staves
also. Will take half or less the time of using a router, no expensive
bits, all on tablesaw.
(3) assembling pieces: cut out 10" squares of scrap 1/4" sheet goods
(thinner is OK), one less in number than the mast is long. Draw
descending-diameter circles on these squares, from maximum diameter
of mast to minimum. Inscribe the shape (octagon for 8, hexagon for 6,
etc.) to match your mast in each of these circles, with the bottom
edge on the flat. Cut out the shapes from the squares, cutting to
the inside of the line. You now have a series of "clamps" that will
hold your mast together in one piece, level, on a flat surface during
glue-up.
(4) glue-up: after dry-fitting and adjusting as required, use
polyurethane (gorilla-type) glue for assembly; spray one surface of
each joint with a water mister (windex bottle), then glue up the
other, spreading glue quickly, but fully on both surfaces; assemble
using "clamps"; wrap the whole thing with bungi cords, elastic tape,
nylon cord or heavy fishline to apply local pressure to the surfaces.
Lay down flat and let set up.
(5) tomorrow: peel off the fishline, slide off the clamps, and start
planing off the dried PU glue and the sharp corners.
You can do the whole thing in one day, maybe two.
> > Thanks for the info, guys.Tips for:
> > $225 if i drive a couple of hours to pick up the aluminum
> > tubing....think i'll end up building a bird's mast. I ran the
> > numbers and i fugure i'll save $150 if i build my own.
> > Jason
(1) cutting tapers. take planks of correct length and width for
starters; mark taper tip + 1/8" on each end; connect the dots with a
straight line; cut 90 degrees on the line. Voila: two staves.
(2) cutting bird's mouth: on table saw, CAREFULLY set up first angle
of cut of bird's mouth out from under of bottom edge auxiliary fence,
testing for depth so that a 90-degree divot is removed. cut all
staves on first pass. Set up second angle similarly, cut staves
also. Will take half or less the time of using a router, no expensive
bits, all on tablesaw.
(3) assembling pieces: cut out 10" squares of scrap 1/4" sheet goods
(thinner is OK), one less in number than the mast is long. Draw
descending-diameter circles on these squares, from maximum diameter
of mast to minimum. Inscribe the shape (octagon for 8, hexagon for 6,
etc.) to match your mast in each of these circles, with the bottom
edge on the flat. Cut out the shapes from the squares, cutting to
the inside of the line. You now have a series of "clamps" that will
hold your mast together in one piece, level, on a flat surface during
glue-up.
(4) glue-up: after dry-fitting and adjusting as required, use
polyurethane (gorilla-type) glue for assembly; spray one surface of
each joint with a water mister (windex bottle), then glue up the
other, spreading glue quickly, but fully on both surfaces; assemble
using "clamps"; wrap the whole thing with bungi cords, elastic tape,
nylon cord or heavy fishline to apply local pressure to the surfaces.
Lay down flat and let set up.
(5) tomorrow: peel off the fishline, slide off the clamps, and start
planing off the dried PU glue and the sharp corners.
You can do the whole thing in one day, maybe two.
Your birdsmouth mast will be a lot lighter than the aluminium, easier
to handle, and nicer to handle too. Also good to have less weight up
in the bow.
DonB
http://oink.kiwiwebhost.biz/
to handle, and nicer to handle too. Also good to have less weight up
in the bow.
DonB
http://oink.kiwiwebhost.biz/
> Thanks for the info, guys.
> $225 if i drive a couple of hours to pick up the aluminum
> tubing....think i'll end up building a bird's mast. I ran the
> numbers and i fugure i'll save $150 if i build my own.
> Jason
--- Jason Stancil wrote:
than a year to finish
the hull], I wouldn't
want the masts sitting
around to 'age' and trip
over until I need them.
I made a similar mistake
with my rudder, building
it in Nov'2002, and kicking
it around until Feb'2004 .
When I finally needed
to mount it to the hull,
it was already greyed from
weathering. :)
The lesson I learned was"
Build [and buy] first things
first and last things last.
Heck, I bought some navigation
lights early, lost them, and
ended buying another set again!
When you finally launch your
boat, you will have 'year old'
wood masts instead of new ones.
Some of the varnish on my boat
shows a need for another coat
due to weathering, and it is
still sitting in my driveway. :/
> I need to get my mastsIn my case, [taking more
> built before
> i fill my garage
> with my hull.
than a year to finish
the hull], I wouldn't
want the masts sitting
around to 'age' and trip
over until I need them.
I made a similar mistake
with my rudder, building
it in Nov'2002, and kicking
it around until Feb'2004 .
When I finally needed
to mount it to the hull,
it was already greyed from
weathering. :)
The lesson I learned was"
Build [and buy] first things
first and last things last.
Heck, I bought some navigation
lights early, lost them, and
ended buying another set again!
When you finally launch your
boat, you will have 'year old'
wood masts instead of new ones.
Some of the varnish on my boat
shows a need for another coat
due to weathering, and it is
still sitting in my driveway. :/
Thanks for the info, guys.
$225 if i drive a couple of hours to pick up the aluminum
tubing....think i'll end up building a bird's mast. I ran the
numbers and i fugure i'll save $150 if i build my own.
Jason
$225 if i drive a couple of hours to pick up the aluminum
tubing....think i'll end up building a bird's mast. I ran the
numbers and i fugure i'll save $150 if i build my own.
Jason
--- Inbolger@yahoogroups.com, "Jason Stancil" <jasonstancil@h...>
wrote:
If you to Bolger2 mesg#154, you will see a thread about building a
birdsmouth for MICRO NAV. I believe Derek Waters is the only person
who has actually built this rig and sailed it so far. He answered a
lot of questions for me on that list.
The mast for the NAV rig is more easy than most, as it is not tapered
so that the gaffs can run and down freely. Also it does not require
the built in flex like the sprit mast since the sheetlets control the
twist in the sail. So I plan to build mine exactly as Derek has. I
believe it will be strong enough even for a LONG MICRO.
Cheers, Nels
wrote:
> I need to get my masts built before i fill my garage with my hull.Hi Jason,
> I'm trying to figure out what route to take. Bolger specifies AL
> tubing for the masts but has OK'd wood.
If you to Bolger2 mesg#154, you will see a thread about building a
birdsmouth for MICRO NAV. I believe Derek Waters is the only person
who has actually built this rig and sailed it so far. He answered a
lot of questions for me on that list.
The mast for the NAV rig is more easy than most, as it is not tapered
so that the gaffs can run and down freely. Also it does not require
the built in flex like the sprit mast since the sheetlets control the
twist in the sail. So I plan to build mine exactly as Derek has. I
believe it will be strong enough even for a LONG MICRO.
Cheers, Nels
Jason --
Check out the birdsmouth calculators on Greg Carlson's site:
http://www.carlsondesign.com/#Fun_Shareware
(You might need to scroll down a ways if the bookmark doesn't
automatically take you to the boat design shareware section.)
Download one (or more) of the birdmouth calculators and you can play
with all the stave widths and thickness you could ever dream of.
Oddly, one calculator gave me a stave-width value of 2.071 for a 5"
diameter mast. The other calc gave 1.896". The stave thickness should
be 20% of the mast diameter, which for a 5" mast would be 1". But you
can vary it up or down depending on your desire for strenght vs.
desire for weight savings.
I recently cut staves for a 5" mast (tapering to 2.5"). I used 2x10s
to rip out my staves, and just left the thickness at 1.5". I may
plane that down a bit before glue-up, though.
Good luck! Keep us updated on your progress.
All best,
garth
Check out the birdsmouth calculators on Greg Carlson's site:
http://www.carlsondesign.com/#Fun_Shareware
(You might need to scroll down a ways if the bookmark doesn't
automatically take you to the boat design shareware section.)
Download one (or more) of the birdmouth calculators and you can play
with all the stave widths and thickness you could ever dream of.
Oddly, one calculator gave me a stave-width value of 2.071 for a 5"
diameter mast. The other calc gave 1.896". The stave thickness should
be 20% of the mast diameter, which for a 5" mast would be 1". But you
can vary it up or down depending on your desire for strenght vs.
desire for weight savings.
I recently cut staves for a 5" mast (tapering to 2.5"). I used 2x10s
to rip out my staves, and just left the thickness at 1.5". I may
plane that down a bit before glue-up, though.
Good luck! Keep us updated on your progress.
All best,
garth
I meant 8 staves not 5
Jason
Jason
I need to get my masts built before i fill my garage with my hull.
I'm trying to figure out what route to take. Bolger specifies AL
tubing for the masts but has OK'd wood. I think i'm going to do wood
to save my money for finishing touches on the boat. Bruce made his
navigator mast from 20' doug fir 2x4s and i'm thinking about doing a
birds mouth just to try it. From what i've read he staves are
suppose to be 1/2 as thick as they are wide?.....can i beef up that
thickness for aditional strength or will that screw something up? I
have'nt got my navigator sheet yet so i'd like to hear what the
plans call for dimension wise.....20' Long?. Bruces mast is 4.5"
round will a birdsmouth of that dimension be strong enough? Or
should i go to 5"......I'd rather err on the side of strengh. I'm a
young guy and i'm not too worried about being able to step a 20'
mast unless it gets over say 80lbs.
5 staves at 2" width and 1" thick should be 5" round when assembled?
i'll do a test run on a 2 footer before i go full size.
Thanks
Jason Stancil
I'm trying to figure out what route to take. Bolger specifies AL
tubing for the masts but has OK'd wood. I think i'm going to do wood
to save my money for finishing touches on the boat. Bruce made his
navigator mast from 20' doug fir 2x4s and i'm thinking about doing a
birds mouth just to try it. From what i've read he staves are
suppose to be 1/2 as thick as they are wide?.....can i beef up that
thickness for aditional strength or will that screw something up? I
have'nt got my navigator sheet yet so i'd like to hear what the
plans call for dimension wise.....20' Long?. Bruces mast is 4.5"
round will a birdsmouth of that dimension be strong enough? Or
should i go to 5"......I'd rather err on the side of strengh. I'm a
young guy and i'm not too worried about being able to step a 20'
mast unless it gets over say 80lbs.
5 staves at 2" width and 1" thick should be 5" round when assembled?
i'll do a test run on a 2 footer before i go full size.
Thanks
Jason Stancil