shortening thru hull fittings?

On Mon, 20 Aug 2007 05:11:28 GMT, Evan Gatehouse
<ceilydh***NO_SPAM***@shaw.ca> wrote:

>I've got to put in some new thru hulls and of course the stem length
>of the fitting is about 3" long. The hull is ~3/4" thick, the portion
>that sits in the seacock is perhaps 1" which leaves 1-1/4" or so to be
>made up with backing pads. This is a bit excessive to me and probably
>dates back to wooden boats with 2" thick planking!
>
>Anybody ever cut their thru hull fitting before installing it? I'd
>leave the nut on to chase the threads after cutting, and cut it with a
>hacksaw or cut off wheel on an angle grinder.
>
>Thanks,
>
>Evan Gatehouse


Normally throu hulls that mate with a flange mounted sea-cocks will
require cutting to length, depending on the thickness of the hull
reinforcement plate(if any) that is fitted.

My experience that the easiest method is to push the through-hull into
place and measure the free length inside the hull.

From this measurement you can calculate the required overall length,
measured from the bottom of the head. Then take them to the machine
shop and let them cut and face them to length on a lathe.

Of course, you can cut them with a hacksaw/cutoff wheel and file or
grind to fit but the machine shop route always seemed to me to end up
with a nicer fit.




Bruce in Bangkok
(brucepaigeATgmailDOTcom)
 >> Stay informed about: shortening thru hull fittings? 

Lew Hodgett wrote:

> "Evan Gatehouse" wrote:
>
>> I've got to put in some new thru hulls and of course the stem length of
>> the fitting is about 3" long. The hull is ~3/4" thick, the portion that
>> sits in the seacock is perhaps 1" which leaves 1-1/4" or so to be made up
>> with backing pads. This is a bit excessive to me and probably dates back
>> to wooden boats with 2" thick planking!
> <snip>
>
> I'd want at least a 3/4 backing pad to allow for hull curvature, so based on
> your estimates above,
> you want to go thru all that work to save 1/2"(1-1/4 - 3/4")?

No hull curvature; it's a hard chined catamaran.

> What's the benefit?

Excess weight - every little bit counts for me...

Evan
 >> Stay informed about: shortening thru hull fittings? 

Make up a V block jig to hold them properly and cut them with a band saw.
File the cut end true and back the nut off. Do not force the nut. If you can
find a proper die for the thread put that in place before cutting and use it
to clean the thread.



"Evan Gatehouse" <ceilydh***NO_SPAM***@shaw.ca> wrote in message
news:4o9yi.73998$rX4.72949@pd7urf2no...
> I've got to put in some new thru hulls and of course the stem length of
> the fitting is about 3" long. The hull is ~3/4" thick, the portion that
> sits in the seacock is perhaps 1" which leaves 1-1/4" or so to be made up
> with backing pads. This is a bit excessive to me and probably dates back
> to wooden boats with 2" thick planking!
>
> Anybody ever cut their thru hull fitting before installing it? I'd leave
> the nut on to chase the threads after cutting, and cut it with a hacksaw
> or cut off wheel on an angle grinder.
>
> Thanks,
>
> Evan Gatehouse
 >> Stay informed about: shortening thru hull fittings?