Correct bolts in a thru-hull mounting
I First, I would like to thank everybody for their responses to the subject question I posted last month.
I decided to copy the yard’s management with your comments and subsequently received the following message:
Hans,
We use ABYC (American boat and yacht council) standards as a standard for building and service work. I have checked with ABYC and this is perfectly acceptable practice
Now, I would like very much to be able to confirm the above yard statement regarding ABYC’s view on this matter.
As I am not a ABYC member, what do you suggest on how II should proceed?
Thank you
Hans Knoepfel, Mischief, Hatteras 42’ LRC
Though I've not looked through the specific ABYC standard, no doubt that
high-grade stainless steel bolts are acceptable when through-bolting a
bronze seacock. My concern is with crevice corrosion occurs over time in
locations that have a lack of oxygen. Not a big deal, but the bolts will
need to be pulled periodically and examined. The good new is that should a
bolt fail, if the seacock is properly installed with its thru-hull, it is
the thru-hull that makes the secure-enough connection. The bolts are there
only to keep the seacock from turning with the opening or closing or a
recalcitrant handle. If a bolt fails, all that will probably happen is a
leak. They are approved seacocks I'd hope.
*Rudy & Jill Sechez *
*BRINEY BUG-a 34' Sail-Assisted Trawler *
*Anchoring Consultants @ trawlertrainingabc.com
http://trawlertrainingabc.com *
*850-832-7748 *
Vero FL
Hi,
The thru-hulls on all the boats I have worked on had no thru-bolts,
even on wooden boats. On steel boats, they just had a steel pipe welded
on. On wooden and fiberglass boats, they all had a flange on the outside
and were straight-threaded (not pipe thread) and a square wooden backing
block on the inside whose inside face was made parallel to the flange
base. I did see a few boats with round backing blocks, but it was
thought that they took too much time to make. Sealant was liberally
applied to the thru-hull, and the backing block. The thru-hull shut-off
valve was then screwed down onto the thru-hull. Care had to be taken to
be sure that there was enough thread - but not too much thread - for the
valve to tighten down onto the thru-hull. Most valves had 3 screw holes
so that short screws could be inserted into the backing block to keep
the valve from loosening up, but not extend into the hull, unless it,
too, was made of wood. The wooden backing blocks were usually made out
of 3/4" exterior grade plywood. Highly curved hulls usually had 2 layers
of plywood because the block had to be planed to match the curvature of
the hull. The edges of the plywood squares were cut at about a 45 degree
angle and were sized according to the size of the thru-hull. As I
recall, a 3/4" thru-hull had about a 6"x6" backing block. One boatyard
applied a coat of penetrating resin to the backing blocks and let the
resin harden before placing them into the boat. To tighten the
thru-hull, it was held on the outside with a wide stiff piece of metal -
like a strong putty knife - that rested against two lugs inside the
thru-hull. The thru-hulls were first tightened to "almost tight", and
the orientation checked, then loosened and the thru-hull twisted so that
when the valve was in the correct position, it was tight. It has been a
bunch of years since I worked on big boats, so my memory may be failing,
but the above is how I recall we did it.
--
Take care and be safe.
Wayne
Celestial - Destroyed by Hurricane Michael - 2019
Albin43 Sundeck
Near Panama City, FL
To re enforce what Rudy said here attached are pictures of a 25' center
consoled fishing boat's transom lifting eye that failed due to crevasse
corrosion. I witnessed it fall. Thankfully, no one was hurt
After witnessing that, it is Silicon Bronze for me in critical applications
especially below the waterline or fasteners that are difficult to remove,
inspect and re-bed.
Cheers,
Joe & Punk Pica
10031 Windward Dr.
New Bern, NC 28560
MTOA #3813, AGLCA #5485 Platinum
http://carolynann-n37.blogspot.com/
301-904-9122
Yacht Sales, Curtis Stokes & Associates
joseph.pica@gmail.com
Joe@CurtisStokes.net
w
ww.curtisstokes.net
On Wed, Feb 5, 2020 at 11:42 AM Rudy Sechez via Trawlers-and-Trawlering <
trawlers@lists.trawlering.com> wrote:
Though I've not looked through the specific ABYC standard, no doubt that
high-grade stainless steel bolts are acceptable when through-bolting a
bronze seacock. My concern is with crevice corrosion occurs over time in
locations that have a lack of oxygen. Not a big deal, but the bolts will
need to be pulled periodically and examined. The good new is that should a
bolt fail, if the seacock is properly installed with its thru-hull, it is
the thru-hull that makes the secure-enough connection. The bolts are there
only to keep the seacock from turning with the opening or closing or a
recalcitrant handle. If a bolt fails, all that will probably happen is a
leak. They are approved seacocks I'd hope.
*Rudy & Jill Sechez *
*BRINEY BUG-a 34' Sail-Assisted Trawler *
*Anchoring Consultants @ trawlertrainingabc.com
http://trawlertrainingabc.com *
*850-832-7748 *
Vero FL
http://lists.trawlering.com/mailman/listinfo/trawlers_lists.trawlering.com
To unsubscribe or modify your subscription options (get password, change
email address, etc) go to:
http://lists.trawlering.com/mailman/listinfo/trawlers_lists.trawlering.com
Trawlers & Trawlering and T&T are trademarks of Water World
Productions. Unauthorized use is prohibited.
Hans,
Your boat!
Your Money!
Your piece of mind!
In my book, minimally acceptable standards are absolutely unacceptable to
me.
What worked for 40 years will work for 40 more.
Stick to your guns. You will sleep better for doing so.
Lee
Levent Marina, Izmir Turkey
On Wed, Feb 5, 2020 at 6:39 PM Hans Knoepfel wrote:
I First, I would like to thank everybody for their responses to the
subject question I posted last month.
I decided to copy the yard’s management with your comments and
subsequently received the following message……