Installing padeyes in FRP overhead
Good morning all. Here's a question to perhaps distract those of you not
here in chilly San Francisco from all the heat and humidity:
Our Nordhavn has solid FRP "ceilings" over the aft deck (cockpit) and
starboard side deck (walkway). These "ceilings" form the bottom of a hollow
structure whose top is the surface of the boat deck. The space between
"ceiling" and boat deck is perhaps six to eight inches. There are various
penetrations in the "ceiling" for things like lights and deck plates, but the
hollow space inside is not readily accessible.
I want to add three padeyes to the "ceiling": one over the boarding door on
the starboard side that can be rigged with a block for MOB emergencies, and
two over the aft deck for something a little more fun: a hammock.
The "ceiling" is 1/2" solid FRP so I (and the builder) think that with proper
backing plates the strength is there. However, given the limited access to the
overhead space I'm wondering how best to position and lock the backing plates
in place. This is of course connected to what hardware to use: lags/tapping
screws or machine screws with nuts.
I would very much appreciate any advice or suggestions from those who've
engineered solutions in similar circumstances.
Thanks!
How do you plan to gain access to the interior of this space? There are
stainless toggle bolts that are available and would certainly distribute the
load adequately for rare MOB use. The hammock might be a different story
although 1/2" fiberglass is impressive and 3 toggle bolts would distribute a
hammock's load.
Ron Rogers
hollow space inside is not readily accessible.
I want to add three padeyes to the "ceiling": one over the boarding door on
the starboard side that can be rigged with a block for MOB emergencies, and
two over the aft deck for something a little more fun: a hammock.
The "ceiling" is 1/2" solid FRP so I (and the builder) think that with proper
backing plates the strength is there. However, given the limited access to the
overhead space I'm wondering how best to position and lock the backing plates
Adam,
I had a similar situation on a former boat where I wanted to add
hardware with some beef to it, and limited access. I had access to the
space, I just couldn't reach the final destination of the hardware. What
I ended up doing was having a backing plate made from 3/16" stainless,
put holes on centers to mate with my hardware, then had stainless
nylock nuts tig welded to the plate, enough to affix them solidly but
not enough to melt out the nylon. (The welder had the hardware in hand
to insure perfect alignment.)
I then fished a strong piece of cord through the hole in the fiberglass
where my backer plate was to end up. I picked up the end of the string
with another fish line and got it to where I had access, put the cord
through the nut and tied it off to a piece of rod or whatever on the
back side, like a toggle. I applied some dabs of 5200 to the plate, then
pulled it to the hole. This was a vertical surface, so it made it a bit
tricky to align the hole, but I used the upper hole for my pull point,
then when the backer came close, I started a bolt in the lower hole to
grab the piece. Once that was started, I could control the position of
the piece, and was able to cut the pull string, and start the other
bolt. Once the 5200 cures, the backer plate is permanently attached, and
the nuts won't drop off if the hardware must be removed for any reason.
It was a bit tedious, but was very secure, and showed no other
penetrations other than those to attach the hardware. Perhaps you could
adapt that idea to your purposes.
I've also used stainless "Togglers", they'd probably be easier to
install, but I'd want to be sure of the weight if you're using it to
hang a body from. IMHO, a backing plate would be less likely to pull out
than togglers, which rely on a relatively small area of purchase to
support the load they're bearing.
--
Steve Sipe
Solo 4303 /"Maerin"/
On the "Down East Loop" 1175 nm so far
Gaspi Peninsula
On Jul 24, 2010, at 10:47 AM, Steve Sipe scs_maerin@maerin.net wrote:
I then fished a strong piece of cord through the hole in the fiberglass
where my backer plate was to end up. I picked up the end of the string
with another fish line and got it to where I had access, put the cord
through the nut and tied it off to a piece of rod or whatever on the
back side, like a toggle. I applied some dabs of 5200 to the plate, then
pulled it to the hole.
Steve: that's bloody brilliant! Thanks so much. Only one question: how did you
keep the 5200 from smearing off the backer plate as you dragged it into
position? I was thinking I could use a curved syringe tip inserted into the
hardware hole from below to inject a ring of 5200 around the inside of the
hole.
The "ceiling" is 1/2" solid FRP so I (and the builder)
think that with proper
backing plates the strength is there. However, given the
limited access to the
overhead space I'm wondering how best to position and lock
the backing plates
in place.
Hi Adam
A couple of thoughts come immediately to mind. First, you can install access plates adjacent to the location for the fasteners. Either on top or from underneath. If you are lucky, you may be able to locate access plates so that one can service two or more locataions. Might need to add a long handle, of some type, to a wrench to be able to hold the nuts, if you use this idea.
Another idea is to fill the space with an appropriate filler and through bolt. What could be an acceptable filler, you might ask? Got alot of choices there, but whatever you choose, install it in such a manner that when water gets in, it can get out and get out without doing damage to the coring or travel inside this hollow space to somewhere where it can cause damage.
In one installation, we drilled a hole in the top, pumped in thickened epoxy until a column was made and when hard, went back and drilled the appropriate sized through holes. This made a compression post, sealed against water going anywhere, when if the water were to get through the sealant, it would drip out past the nuts on the inside where it could be seen and addressed. This made through bolting possible. Granted the space wasn't as deep as yours, but it is an example that might stimulate an idea.
Another idea is to cut open the top, in the areas where the fasteners will go, allowing access that could allow you to fill the space with wood, foam or another pick of your choice. Repair the cut fiberglass and drill enlarged holes, fill with resin and redrill for the through bolts.
You could always drill a hole large enough in diameter (from the top) to accommodate a brass, bronze, stainless steel or fiberglass pipe/tube whose ID can allow the size fastener that you want to use to pass through it. Epoxy that to the inside of the bottom layer and flush to the top of the deck. Smooth off and paint. Drill for through bolts.
A simple idea would be to use expanding "nuts" on the underside of the top plate, but to find something strong enough and rust resistant is up to you; I haven't the faintest idea where to look except to Google fasteners.
Hang in there, I'm sure someone will come up with even a simpler way of doing it.
Rudy
Briney Bug, Panama City, Fl
Hi Adam,
Just thinking out loud...
I want to add three padeyes to the "ceiling": one over the boarding door on
the starboard side that can be rigged with a block for MOB emergencies, and
two over the aft deck for something a little more fun: a hammock.
Make up a thick rectangular shaped backing plate and match drill
pad-eye holes that will be later threaded. Make it as narrow as
possible, but strong and long enough to spread out the load. Cut a
slot at the location of the padeye, just large enough so that the
backing plate will pass through the FRP ceiling. Match drill the
ceiling so that the slot will be in the middle of the pad-eye. Make a
larger square/rectangular/round plate (cover plate) and match drill
it. This plate is to cover the slot. It can be made of any suitable
and aesthetic material. Be sure to mark everything so that the
orientation can be kept correct, just in case everything is not
symmetrical. Thread the backing plate, drill the ceiling and cover
plate holes a little larger than the size of the bolt shanks. Tie a
string to the backing plate and insert the plate though the ceiling.
Pull, push, and rotate the plate into position and screw in one
threaded stud or all-thread (not a bolt) at each end to hold it in
place. I would probably use a little adhesive on the backing plate
after it was installed (just around the slot to keep it in place if I
ever had to redo anything - but not so much that I couldn't remove
it). Apply sealant to the top of the cover plate and the top of the
padeye and place them over the studs. Screw in two bolts - liberally
coated with sealant. Remove the studs and screw in the other two
bolts that have also been liberally coated with sealant. Tighten all
bolts evenly, but not really tight. Clean off any excess sealant. Let
the sealant cure, then tighten the bolts.
I know, thinking out loud can be dangerous.....
Take care and be safe.
Wayne
Celestial
Albin 43 Sundeck
Near Panama City, FL
Gee, if all my ideas would only come before I hit the send button!
Adam, 1/2 fiberglass is thich enough where you can consider drilling and tapping for machine screws. Coupled with fine threaded screws, epoxying the threads into the fiberglass (clean the threads appropriately first) and using a polyurethane sealant (5200), this could be strong enough for your purpose.
If more strength is required, you could consider drilling out the padeyes for larger diameter screws, or have padeyes made up by a welder that will accommodate bigger screws.
The only thing about this approach that concerns me is if water should start getting past the sealant. You might want to consider drilling an appropriately placed drain hole or two.
Rudy
Briney Bug, Panama City, Fl
Hmm, I inadvertently sent this to Rudy. So here for Adam and the list is
another copy :-)
Hi Adam,
Have you spoken to James Knight. It may be that you are re-inventing the
wheel here. If someone has done it before on a Nordy, it will be James, or
he knows how they did it.
I think his cell phone number is 1-561-262-4279
FWIW.
Paige
It is worth allot before messing-up a Nordhavn with untried ideas for this
specific situation. You might want to tell Mr. Knight which Nordhavn you
own.
< http://www.nordhavnonly.com/id4.html >
Ron Rogers
-----Original Message-----
From: Paige Reeves
Sent: Saturday, July 24, 2010 5:05 PM
Have you spoken to James Knight. It may be that you are re-inventing the
wheel here. If someone has done it before on a Nordy, it will be James, or
he knows how they did it.
I think his cell phone number is 1-561-262-4279
FWIW.
Paige