This guy Frank Hagan has a good illustration of the "proper" birdsmouth
set up, as well as a number of tips in building.
http://users2.ev1.net/~fshagan/bm.htm
In the horror show I created by not thinking to count my pieces, I got
frustrated enough to overlook one of his other caveats, which was to
have the screw part of the hose clamps in various parts of the mast
instead of aligning them. If you inadvertently align them, you seem to
put enough pressure on *one* strip that induces a slight bow in the mast.
I plan to set the spar so that the bow is bowing aft and I will explain
that in an unstayed rig I wanted to "pre-bend" for sail shape, as there
is no backstay to shape the mast with.
I'm not sure I can sell that to my 12 year old, she's pretty good at
sniffing my BS
but, it's worth a shot
Jonathan
Brian Whatcott wrote:
Ah yes: that explains it.
I was interested in the fishmouth approach - I hadn't run across
this method before.
I started by asking myself: Why wouldn't I saw on a 22.5 degree
angle? This would be economical in the spar material: only the kerf
would be lost. But visualizing the clamp up, it would be a nightmare,
I'm su the fishtail approach is largely self aligning I'd think.
And your approach ought to be very warp resistant.
I recall that the 2 part sandwich approach that I used allowed a
little bowing to show up after a year or two.
I also recall that a hollow shaft loses 5% of its strength (in torque)
while losing 25% of its weight, for a 50% of radius, hole.
Brian Whatcott Altus OK
On Sun, 15 Aug 2004 06:54:41 -0400, Jonathan
wrote:
No, it uses 8. I used 1x4 fir decking and got 3 strips per board, and I
inadvertently used all nine instead of discarding one
In the process of clearing a space to lay out the mast for gluing,
checking all of the 45 degree cuts for full cut through (my saw depth
changed without my input after the first 4 cuts, and two strips had to
be cleaned up with a Sandvick scraper)
I forgot to discard one of the lengths I was wondering why the hose
clamps I used to glue it up were suddenly too short when they had plenty
of room on my test, a 2 foot spar.....
*Fortunately*?, my epoxy mix was thick enough to fill most of the gaps.
There are a few places I will use the West syringes to fill some
hairline spaces.
I was wondering if anyone would catch that goof
Jonathan
Brian Whatcott wrote:
On Sat, 14 Aug 2004 22:16:33 -0400, Jonathan
wrote:
Took a detour to work on Ocean Planet for two weeks and to make a mast.
Interior is painted. Almost there !
http://home.comcast.net/~jonsailr
Nicely illustrated! But the mast uses 9 45 degree segments?
you have a gap or two, I reckon.
Brian Whatcott
--
I am building a Dudley Dix, Argie 10, for my daughter. Check it out:
http://home.comcast.net/~jonsailr