Re: [PSUBS-MAILIST] thru hull fittings

["Dan H." <jmachine@adelphia.net>]

Brian,

You sound like your on the right track with your through hulls.  One thing
to consider with your drop weight through hulls is, how your going to attach
the handle inside the sub.  If your going to drill through the shaft you may
want to consider a shaft larger then a half inch since it's holding the drop
weight and will get yanked through the hull if it breaks or of the bolt
shears.  When making mine, I was visualizing the drop banging up and down on
it's shaft while tailoring down the road.  Then I want to depend it to hold
the weight when diving.

I had a bit of trouble with the through hulls necking down in the weld area
but cured the problem with a hand reamer after welding.  Use two O-rings,
one near each end, for double protection and then you won't be welding or
reaming where they will be.

Dan H.


----- Original Message -----
From: "Brian Cox" <ojaibees@ojai.net>
To: <personal_submersibles@psubs.org>
Sent: Saturday, February 28, 2004 1:00 AM
Subject: Re: [PSUBS-MAILIST] thru hull fittings


> Alec,   If I'm envisioning that piece correctly it started out as a 1.5"
dia shaft and a portion was machined down to 1" , then the part is inserted
from the outside of the sub where the  lip keeps the part from blowing into
the sub under pressure.  I probably don't have your dimensions quite right
but I think I see the part.  Are the shaft and hole 1"  +/-  2 thousandths?
>
> Brian
> ----- Original Message -----
> From: "Alec Smyth" <Asmyth@changepoint.com>
> To: <personal_submersibles@psubs.org>
> Sent: Friday, February 27, 2004 4:28 PM
> Subject: RE: [PSUBS-MAILIST] thru hull fittings
>
>
> > Yes, there's a reason. Because the sub is hydrobatic, when the sub is at
a 90 degree roll the drop weight will exert a bending moment. So I made it
stubby. The maximum diameter is 1.5", and its set in an insert that is 3" in
diameter. The difference between the diameters of the shaft and the hole is
only 2 thousandths of an inch, so that the O rings cannot extrude and so the
insert will help the shaft resist the bending moment. And the reason I said
"maximum diameter" is that there is a 1" section on the shaft too, to
prevent the ambient pressure from shooting it into the boat after releasing
the drop weight, or when the sub is inverted.
> >
> > Sorry for writing a book on such a small topic...
> >
> > Alec
> >
> > -----Original Message-----
> > From: Brian Cox [mailto:ojaibees@ojai.net]
> > Sent: Fri 2/27/2004 5:40 PM
> > To: personal_submersibles@psubs.org
> > Cc:
> > Subject: Re: [PSUBS-MAILIST] thru hull fittings
> >
> >
> >
> > Thanks Alec,   I read a few posts back that your drop weight shaft was
like 2" or something,  it seamed rather large was there some reason for
that?
> >
> > Brian
> > ----- Original Message -----
> > From: "Alec Smyth" <Asmyth@changepoint.com>
> > To: <personal_submersibles@psubs.org>
> > Sent: Friday, February 27, 2004 1:28 PM
> > Subject: RE: [PSUBS-MAILIST] thru hull fittings
> >
> >
> > > With a 1.25" insert, you have added much more reinforcement than the
material you removed with a 0.5" shaft hole. If I remember right, the rule
of thumb is that you should add twice as much as the hole removed. So it
should be sufficient.
> > >
> > > Alec
> > >
> > > -----Original Message-----
> > > From: Brian Cox [mailto:ojaibees@ojai.net]
> > > Sent: Fri 2/27/2004 3:51 PM
> > > To: Personal_Submersibles@psubs.org
> > > Cc:
> > > Subject: [PSUBS-MAILIST] thru hull fittings
> > >
> > >
> > > Hi All,    I am in the process of machining thru hull fittings (316L
ss) that will have 1/2" shafts running through them to turn valves, turn
rudders, and other functions as well, drop weight, and possibly move trim
ballast ;-)     .  The fittings that I am machining at the moment are 1 1/4"
od  with the 1/2" id ( for the shaft)  is that 1 1/4"  a big enough chunk of
steel to be welded through 1/4" A516 70   or should that OD be larger for
some reason?
> > >
> > > Thank You
> > >
> > > Brian Cox
> > >
> > >
> >
> >
> >
> >
>
>