Advice on fixing screws pulled out of GRP?
Henry Law
"track" on either side of the cockpit for the footplate to bolt onto.
The tracks are held down by countersunk screws which go vertically down
into the fiberglass of the hull.
Well, they were so held. Now the screws are pulling out and the port
track is well on its way to flapping in the breeze.
It's not the first time it's happened and both sides have been affected.
Earlier attempts to fix the problem involved trying to push epoxy into
the stripped screw holes to give the screws proper purchase again; more
screws were also installed so that we now have six or seven instead of
four; all to no avail.
Does anyone have experience of this kind of screws-pulled-out-of-GRP
problem, and what would you advise? We're kicking around ideas of
drilling the holes out much larger than the screws so we can get good
amounts of epoxy into them. A variant of this has us gluing plugs (of
what?) into those enlarged holes and then re-drilling for the screws.
All suggestions would be welcome (other than sending it off for repair:
we have the usual small-club reasons for not wanting to do that, quite
yet at least).
--
Henry Law Manchester, England
Henry Law
> The Burgashell club single...
I realise I've been a bit loose with my terminology. This is a standard
Burgashell boat so isn't just "GRP" but is carbon-fiber reinforced.
ng...@aol.com
Not tried it, but I'm picturing something like a piece from an old
meccano set that would go under the decking, pass the full length of
the track, and take a bolted nut* at both ends. The downside is of
course that if that goes, you'll lose an entire strip of decking, but
I'd have thought it should be fairly robust.
*If you can get a flat-headed bolt, of course. Otherwise you'll lose
some adjusting positions on the track...
Tink
When I fiited my last ones I used epoxy to glue the notched plastic
bit onto the boat as well as screw it in. Held so far.
Henry Law
> Not tried it, but I'm picturing something like a piece from an old
> meccano set that would go under the decking, pass the full length of
> the track, and take a bolted nut* at both ends.
I probably didn't make myself sufficiently clear. The horizontal
surfaces on which these stretcher-mounting tracks sit are moulded into
the cockpit edge and there's no access to the underside, where the nuts
would go. I should have taken a photo, really: it would have been much
easier.
edgar
The notched tracks provide a means of adjustment over quite a wide range so
all you have to do is shift them along a bit and carefully drill new holes
of the correct size for the self tapping screws.
Of course blockup the old holes first so water does not get into the
structure and maybe cause problems.
Edgar
"Henry Law" <ne...@lawshouse.org> wrote in message
news:J9WdndD37OIYAo3T...@giganews.com...
Henry Law
> Why try and fix holes that have already given up gripping the screws?
> The notched tracks provide a means of adjustment over quite a wide range so
> all you have to do is shift them along a bit and carefully drill new holes
> of the correct size for the self tapping screws.
Unfortunately we've done that, except that we've left the screws in the
old holes, jammed with as much epoxy as we could force in. So we have
new screws /and/ whatever holding ability the epoxied old holes are
capable of, and the track is still lifting.
Andrew Hunt
Maybe try fill the old holes with epoxy, then add wood to the holes,
i.e. push in a matchstick or two into the epoxy. Once this has dried
you can screw the track back on. This worked on a Weitnauer single I
use (the boatman did the repair) for the bottom track - although the
setup there is rather different and the rail is probably subjected to
much less force than in the case of the two top rails which you are
trying to fix.
Walter Martindale
If it was me:
I'd try removing the old screws if they're not already out, carefully
drilling into the existing holes, and using a dremel or other rotary
tool to flare the inside of the hole so it's larger than the outside
of the hole. Also consider extending the sides of the holes fore and
aft so that if what you bond in there to hold does break loose of the
original matrix it won't be able to turn or pull out.
Make sure the hole and everything surrounding it are DRY. I'd suggest
putting a 40 W trouble light in the foot-well with the boat "guts up",
and leaving the light on in the foot well for a week. Or in the hot
sun (oh, sorry, you're in England ;-).
Get a product such as West System 105 resin and 206 (slow) hardener.
Mix a small batch. Use a small brush and wipe the insides of the
holes down so that there's contact and leave it for an hour or so to
start the curing. (this coats the inside surfaces and seals them)
Then, while the first batch of epoxy is still "gel" stage (not
hardened) mix another batch of epoxy, and mix in "mini-fibers" which
will thicken and reinforce the epoxy. Make it relatively thin so you
can still almost pour it, and use a cheap big-bore syringe to shove it
in to fill the hole.
While this is wet, put the plastic tracks in place and push the screws
into the mixed epoxy/fibers. It probably wouldn't hurt to scuff the
screws with some kind of emery paper in the hopes of roughening the
surface for better grip when the epoxy cures.
Make sure it's all lined up where you want it, tape or clamp it all in
place (making sure the screw heads are all flush in their
countersinks) and leave it for a day to cure.
The idea of brushing it in first is to get a good coating. Then
putting the next epoxy in while the first application is still softish
is to ensure a chemical bond between the first epoxy and second epoxy,
rather than having to sand/abrade the stuff after it cures so that the
new stuff will have a mechanical bond to the first stuff.
If you leave it for a day to cure, West system is around 90% strength
(IIRC) and reaches full strength in 4-6 days. You can row at 90%
strength - 90% of a few tons of tensile strength is sufficient for
most humans.
HTH
Walter
Walter Martindale
> If it was me:
>
> I'd try removing the old screws if they're not already out, carefully
> drilling into the existing holes, and using a dremel or other rotary
> tool to flare the inside of the hole so it's larger than the outside
> of the hole.
Oops... to clarify... enlarge the hole inside so it's smaller than the
opening. Might be challenging to get all the dust/bits out.
W
Henry Law
> (IIRC) and reaches full strength in 4-6 days. You can row at 90%
> strength - 90% of a few tons of tensile strength is sufficient for
> most humans.
Wonderful reply, thank you very much. I'll even forgive the crack about
the weather (I'm feeling generous because the sky has been clear blue
for several days now, with light winds and temperatures in the high 20s C).
Richard du P
> On Jul 4, 8:54 am, Walter Martindale <wmart...@gmail.com> wrote:
>
> > If it was me:
>
> > I'd try removing the old screws if they're not already out, carefully
> > drilling into the existing holes, and using a dremel or other rotary
> > tool to flare the inside of the hole so it's larger than the outside
> > of the hole.
>
> opening. Might be challenging to get all the dust/bits out.
> W
* ?"larger"?
You might find a dentist on the UK Thames Region umpire list. Forgot
to ask him while we were lunching at some upper Thames regatta on
Saturday, but I wonder whether he'd be good at some of that .....
Drills might be wrong gauge
Richard du P
Walter Martindale
Yup... larger... must have been tired, in a hurry, or both when I
wrote that.. Oh. Yes... I was.
Dremel burrs are like dental burrs only bigger. give the fang fixer a
dremel and let him or her at it.
8-)
Walter
Walter Martindale
Yer welcome - Richard caught my boo-boo about smaller/larger.
I probably shouldn't need to mention but will... Nitrile rubber gloves
when handling the epoxies. Dust masks (at least) when sanding the
stuff.
Dust mask (a good one) when handling/mixing the mini-fiber powder in
the epoxy.
Try to make sure you're doing it someplace well ventilated with a
light breeze blowing the epoxy fumes sideways relative to you and the
epoxy - don't want the fumes blown onto you by a wind from in front or
'eddied' into your face by a wind from behind.
edgar
especially indoors although the dust mask is essential if you are sanding or
drilling GRP at any time..
But this thread started because about six holes maybe 1/8 inch diameter
needed to be blocked and redrilled and there is no need for full biohazard
kit to do that..
All you need is one of those double tubes, resin one side and hardener the
other that are sold in hardware stores. Squeezes them out in the correct
proportion and you only need to stir them with a sliver of wood with a
flattened end, add a pinch of microfibrs if necessary and then use the same
sliver of wod to fill the mixture into the holes. We are only taking about a
thimblefull of mixture so fumes are not an issue here as your face is going
to be about 3 feet away from the work so there is no way you are going to
make contact with the mixture or sniff up the microfibres unless you are
exceedingly clumsy.
I will await the flames from'health and safety' minded people but I have
been doing jobs like that or years and never a sniff of fumes has bothered
me.
Edgar.
"Walter Martindale" <wmar...@gmail.com> wrote in message
news:96ea0c53-bedc-445a...@gv8g2000vbb.googlegroups.com...
Walter Martindale
> I cannot disagree with any of that if you are doing a fairly big layup job,
> especially indoors although the dust mask is essential if you are sanding or
> drilling GRP at any time..
> But this thread started because about six holes maybe 1/8 inch diameter
> needed to be blocked and redrilled and there is no need for full biohazard
> kit to do that..
> All you need is one of those double tubes, resin one side and hardener the
> other that are sold in hardware stores. Squeezes them out in the correct
> proportion and you only need to stir them with a sliver of wood with a
> flattened end, add a pinch of microfibrs if necessary and then use the same
> sliver of wod to fill the mixture into the holes. We are only taking about a
> thimblefull of mixture so fumes are not an issue here as your face is going
> to be about 3 feet away from the work so there is no way you are going to
> make contact with the mixture or sniff up the microfibres unless you are
> exceedingly clumsy.
> I will await the flames from'health and safety' minded people but I have
> been doing jobs like that or years and never a sniff of fumes has bothered
> me.
> Edgar.
>
>
> news:96ea0c53-bedc-445a...@gv8g2000vbb.googlegroups.com...
> I probably shouldn't need to mention but will... Nitrile rubber gloves
> when handling the epoxies. Dust masks (at least) when sanding the
> stuff.
> Dust mask (a good one) when handling/mixing the mini-fiber powder in
> the epoxy.
> Try to make sure you're doing it someplace well ventilated with a
> light breeze blowing the epoxy fumes sideways relative to you and the
> epoxy - don't want the fumes blown onto you by a wind from in front or
> 'eddied' into your face by a wind from behind.
Hi Edgar,
I won't "flame" on this but... My understanding is that the exposure
to epoxy resins and hardeners is cumulative, so whatever you can do to
delay problems, the better. A pair of nitrile gloves is cheeeeep,
keeps the goo off your fingers in case anything happens, and is
tougher than latex.
I suggested West System or similar because if 'your' boat is in a
rowing club with lots of boats, there's probably a lot of repair work
takes place. Most places I've visited or coached have a supply of
'industrial' grade epoxy floating around, and frequently someone who
knows how to use it also hangs around the club.
West system epoxies are usually not the 5-minute ones. A lot of
people will go to the hardware and grab the first two-tube kit hanging
on the display, which frequently turns out to be 5-minute epoxy.
5-minute epoxies tend (for reasons I don't understand) to absorb water
over time. "slow cure" epoxies don't. Even the "fast" west system is
not a 5-minute doodad.
If there isn't a supply of West System, or System Three or similar
around the boathouse, sure, a couple of tubes or even one of those two-
barrel syringe things will be fine, but the user has to make sure that
they get the 'slow' curing stuff. 5- minute will not last. IME it
will do in a pinch if you have to get the thing back on the water for
a race in an hour, but then about a year later the epoxy will expand
and/or break down.
W
edgar
The 2-tube stuff I buy for a variety of small jobs has a 30 minute cure
time. I do not use it on boat work- always West system but I think it the 30
min stuff is OK just to block some small screw holes to take fresh screws.
The 5 minute stuff does have its uses. I once repaired a severely cracked
plastic car bumper (fender) with it where it was impossible to hold the lot
together for a proper repair. My solution was to fix each piece in position
one at a time by bridging the gap with aluminium mesh and manually holding
it in position for the 5 minute period while the resin set. Then I had a
properly shaped rigid structure that I could glass over with proper stuff
Edgar
"Walter Martindale" <wmar...@gmail.com> wrote in message
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