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Re: how to ....

David Hyman wrote:
> Hello from Oklahoma.  I've got a mechanical question for you.  I
> suspect you Canadians will welcome the opportunity to think sailing,
> since  your ponds have frozen over by now, haven't they?.  Here
> goes....
>     I need to attach a couple of "t" tracks to my aluminum spars to
> mount a rigid vang -- one to the underside of the boom and one to the
> aft side of the mast. A couple of questions:
>     First, what is the appropriate fastners to use, machine screws or
> self-tapping screws? If I should use machine screws, will I have to
> tap threads into the spar, or will the machine screws create their own
> threads in the drilled hole?
>     Second, the track for the mast will attach over the luff groove;
> should I just screw the track into the back of the luff groove, or is
> there available some sort of tapped slug available that I can insert
> into the groove and then screw the track into?
>     Suggestions, please. Thanks a lot.  By the way, the rigid vang is
> made/sold by Garhauer Marine.  It's a very good piece of equipment at
> about 1/3 the cost of comparable Harken, Shaefer, etc. equipment.
> David Hyman
> Tulsa,
> SJ7.7 #161/SJ21 #1684 (I know, lots of 'em)
Hello David;

The pros usually drill, tap and use machine screws to attach fittings to
a mast.  I used aluminum pop rivits to mount the T track to the
underside of the boom.  A rivet in every hole.  The track is also glued
in place with Sikaflex to minimize shear movement and keep water out. 
Mine has NOT moved.  I hate self tapping screws because I have twisted
off way too many heads.  They are not very usefull then!  If you have
internal lines, ensure that the screws protrude only 1/8" inside the
mast.  Any longer is waste. 

The best way to mount something against the mast is to insert a solid
rod of aluminum of the correct diameter to fill the luff groove. (If you
can't find solid rod, use the leg of an axle kickstand from a bicycle). 
Drill screw holes into the rod and tap them for machine thread.  (You
might want to add an extra hole at the bottom of the rod to insert an
extra screw to act as a tiller.  This makes installing the support
screws child play.  The fitting that rests against the mast must fit
snug without gaps.  You want full support.  Be especially concerned
about side loading the mast as when the boom is out over the water. 
This mounting MUST be solid and very strong. If this assembly comes
loose while you are sailing, it will gouge the deck and you may loose
half the vang. 

HINT - If you make the support screws a little longer, so they protrude
into the mast, they will also prevent the bottom mount from sliding
along the mast.  Double duty.  

Good luck.  Let us know how you make out.  

PS: The pond may be frozen, but so are the mosquitoes!  The bonus is
that the rum is hot with butter floating on top. 

Bob Schimmel
Spruce Grove, Alberta

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