How do I fix A dirty big star crack.
 

The advice given so far looks just fine to me, except for the use of the
dremel! Always sand these things back by hand and keep stopping to
check, you would be surprised at just how quickly you can take gel coat
off small areas with P400 wet and dry!

I am quite concerned that some of these cracks were right through the
hull (and not entirely convinced that this isn't just due to getting
carried away with the dremel :( ). If I have understood, you took enough
gel coat off in the end that you were able to apply cloth on the outside
of the hull but not over any gelcoat? This is quite a serious repair for
cracking!

At this stage my recommendation would be sand over the cloth with up to
P240 wet and dry, but use a sanding block, make it a small one and make
sure you don't overrun onto the surrounding gel. It takes a bit of
practice stopping your sanding strokes so you don't overrun, but just
remember that everytime you stray onto the surrounding gel you are
making it thinner.

To repair an area of the size I am now imagining with gel coat filler is
going to be difficult but not impossible. Spend some time getting the
filler as close to flush as possible whilst it's still wet. When
smoothing filler start with your spreader in the middle of the repair
and work out pulling towards the edges, if you go from one edge to the
other the filler always pulls away at the first edge! Someone questions
the waterproofness of fillers - I can't comment too much but it might be
worth remembering that gel coat is not completely waterproof anyway, it
is semipermeable which is why osmosis can occur. Personally I'd be happy
with an all epoxy boat without any gelcoat, but I can't afford one :)
An alternative to Gel coat is regular gel coat, but you will need to add
about 2% of liquid wax if you want it to actually go off in open air. It
is much easier to buy filler.

You could also do the same repair with epoxy, I would suggest thickening
it slightly with microballoons possibly also with some silica.
Microballoons give you a smooth filler paste that is easy to work, has
high mechanical strength and is expensive, silica thickens epoxy very
well but it gives a paste that is not great to work with has low
mechanical strength but is cheap, carefully mixing them can produce a
good filler! The only trouble using epoxy is that it is much harder to
fair afterwards than a gel coat filler.

Whichever filler you used, again using a small sanding block (literally
cut a 2" x 1" x 1" or less piece of wood to wrap the wet and dry round)
starting at P400 and being careful not to run over the edges you should
be able to get the filler nearly level. The secret here is to make
linear strokes all in the same direction. Now choose the next grade P600
probably and sand it at right angles to the direction you did before
until all the 400 scratches have disappeared and you can only see 600
scratches. Repeat this changing direction through the grades until you
get to the finest you can find (P1600 or superfine) at which point you
shouldn't be able to see the scratches. Continuing with polishing paste
is possible for purists, but this area is probably more shiny than the
rest of your hull now....

BUT, you had a problem. You went through the hull and have only used 1
layer of 10oz cloth to cover it. I would therefore recommend that you
take some P60 or P80 glasspaper to the inside of the hull in way of the
crack - you aren't making it smooth just getting a good deep rough key
for a further repair! This is especially important if your boat is made
of epoxy (and glass) because epoxy forms a waxy top layer as it sets
which you need to remove before laminating over the top. With a light
source outside you can probably see where the cracks were and can work
out what sort of size patches you need. Make them from the same cloth,
I'd say go for 2 or 3 layers as it's fairly lightweight and make them
different sizes. The idea is to put the smallest patch on first in the
right place, then a slightly large one, and then a final even larger one
- this allows you to increase the thickness in that area without getting
a noticeable step! It will probably be an awkward area to work in, so
use epoxy resin. Find an old but clean bit of plywood or something and
use a roller to "wet" the boar with epoxy, then put the last layer on to
it and roll epoxy into it, then the previous layer and roll epoxy into
it etc. If you do this carefully you could actually position all layers
on each other on the board and lift the lot off together, but I was
thinking about doing each separately! Next take a brush and wet the
sanded area that you are going to apply the patch to - it is really
important to wet the area with resin first, if not the patch just won't
stay on! Carefully manoeuvre the patch into position and starting from
the middle smooth it out with your hands (which should have at least a
pair of thick marigolds and preferably a pair of latex gloves and
barrier cream under them) - use the brush to help you position and
smooth the patch. you shouldn't need to put any more resin over it at
this stage but take some care to make sure it is down properly with no
strands hanging or anything, which might require you to wet the brush,
but try and avoid the urge to paint resin over as you will most likely
move the patch. When set check that the edges are smooth - you may need
to sand off spiky bits and stuff to make the inside nice, when happy if
there are roughish bits you might want to paint a bit of resin over, but
remember you need to key up the patch if it is going to stick!

Not sure what to do about the star at the skeg, I suggest you cut it
back with P400 and report your findings! If a gel repair is going to do
it, make sure you sand it so that you bevel the edges .

JIM

Mike Buckley wrote:

Ewan Scott wrote in message
...

Me Again.
This time I may proof read this.

I followed Richard Hayes instructions pretty much to the letter.
I ground the beast out with a Dremmel and found the cracks much deaper
that I previously thought. I ground through the boat in two spots.
I put some packing tape inside he hull to keep things in order as I
worked the ourside and got the gouges filled.
It is not going to be perfect but it is not bad.
I had about 10 yards of 10 Oz Fibre Glass cloth left over from a canoe
I built a long time ago. I used a little of that to reinforce the hull
under the repair.
Seems to work.
I am wondering how you get a reasonable gell coat back on there or do
I just paint it.

Right now I am not sure but I should just have reinforced the inside
and painted the begger. I am told I shuold have just left it because
it can last that way for years and only requires that level or repair
when it actually starts to break down

During my efforts I found another less pronounced star crack around
the skeg box.
That one I likely deserve as I remember one drop os some consiquence.

Are the NDK boats prone to star cracks?? I have one other glass boat,
It has one well deserved crunch but no star cracks. It is much more
flexable all over. The NDK has been babied.

Star cracks are gebnerally quite small and IIRC occur when the surface
has had a good dunt. The substrate matting flexes and the top coat gel
cracks.

By th sounds of your first patch you needed to repair the hull anyway.

These smaller ones - I'd just rough sand them, and paint with gelcoat.



You'll not like this, having "done" your repair, but the next time round I
suggest you do all your prep work and then use packing tape to cover the
OUTSIDE of the hole. Now apply your gel coat (colored as necessary) from the
inside and leave o/night. Now build up your repair from the inside using
your chosen glass material. When you remove the packing tape you'll have a
nice smooth external finish.

I've done substantial repairs with this method with extremely good results,
including rebuilding the foredeck of a general-purpose boat to the extent
that the job was done in 3 stages to cope with all the different angles.

If you have a rummage in the forum/community on the ukriversguidbook site
you'll find an excellent summary from one Jim Wallis on the subject of the
appropriate materials to use. He sometimes looks in on what remains of this
group so maybe he'll post a summary.

The packing tape trick can also be used to good effect on simpler external
repairs using gel coat or gel coat filler (chandlers will have it) by
applying it on top of the gel coat and leaving it until the gel has set.

Mike.

How do I fix A dirty big star crack.
 

Jim Wallis wrote in message news:9fti1c.b16.ln@Eskdale...
The advice given so far looks just fine to me, except for the use of the
dremel! Always sand these things back by hand and keep stopping to
check, you would be surprised at just how quickly you can take gel coat
off small areas with P400 wet and dry!

I am quite concerned that some of these cracks were right through the
hull (and not entirely convinced that this isn't just due to getting
carried away with the dremel :( ). If I have understood, you took enough
gel coat off in the end that you were able to apply cloth on the outside
of the hull but not over any gelcoat? This is quite a serious repair for
cracking!

At this stage my recommendation would be sand over the cloth with up to
P240 wet and dry, but use a sanding block, make it a small one and make
sure you don't overrun onto the surrounding gel. It takes a bit of
practice stopping your sanding strokes so you don't overrun, but just
remember that everytime you stray onto the surrounding gel you are
making it thinner.

To repair an area of the size I am now imagining with gel coat filler is
going to be difficult but not impossible. Spend some time getting the
filler as close to flush as possible whilst it's still wet. When
smoothing filler start with your spreader in the middle of the repair
and work out pulling towards the edges, if you go from one edge to the
other the filler always pulls away at the first edge! Someone questions
the waterproofness of fillers - I can't comment too much but it might be
worth remembering that gel coat is not completely waterproof anyway, it
is semipermeable which is why osmosis can occur. Personally I'd be happy
with an all epoxy boat without any gelcoat, but I can't afford one :)
An alternative to Gel coat is regular gel coat, but you will need to add
about 2% of liquid wax if you want it to actually go off in open air. It
is much easier to buy filler.

You could also do the same repair with epoxy, I would suggest thickening
it slightly with microballoons possibly also with some silica.
Microballoons give you a smooth filler paste that is easy to work, has
high mechanical strength and is expensive, silica thickens epoxy very
well but it gives a paste that is not great to work with has low
mechanical strength but is cheap, carefully mixing them can produce a
good filler! The only trouble using epoxy is that it is much harder to
fair afterwards than a gel coat filler.

Whichever filler you used, again using a small sanding block (literally
cut a 2" x 1" x 1" or less piece of wood to wrap the wet and dry round)
starting at P400 and being careful not to run over the edges you should
be able to get the filler nearly level. The secret here is to make
linear strokes all in the same direction. Now choose the next grade P600
probably and sand it at right angles to the direction you did before
until all the 400 scratches have disappeared and you can only see 600
scratches. Repeat this changing direction through the grades until you
get to the finest you can find (P1600 or superfine) at which point you
shouldn't be able to see the scratches. Continuing with polishing paste
is possible for purists, but this area is probably more shiny than the
rest of your hull now....

BUT, you had a problem. You went through the hull and have only used 1
layer of 10oz cloth to cover it. I would therefore recommend that you
take some P60 or P80 glasspaper to the inside of the hull in way of the
crack - you aren't making it smooth just getting a good deep rough key
for a further repair! This is especially important if your boat is made
of epoxy (and glass) because epoxy forms a waxy top layer as it sets
which you need to remove before laminating over the top. With a light
source outside you can probably see where the cracks were and can work
out what sort of size patches you need. Make them from the same cloth,
I'd say go for 2 or 3 layers as it's fairly lightweight and make them
different sizes. The idea is to put the smallest patch on first in the
right place, then a slightly large one, and then a final even larger one
- this allows you to increase the thickness in that area without getting
a noticeable step! It will probably be an awkward area to work in, so
use epoxy resin. Find an old but clean bit of plywood or something and
use a roller to "wet" the boar with epoxy, then put the last layer on to
it and roll epoxy into it, then the previous layer and roll epoxy into
it etc. If you do this carefully you could actually position all layers
on each other on the board and lift the lot off together, but I was
thinking about doing each separately! Next take a brush and wet the
sanded area that you are going to apply the patch to - it is really
important to wet the area with resin first, if not the patch just won't
stay on! Carefully manoeuvre the patch into position and starting from
the middle smooth it out with your hands (which should have at least a
pair of thick marigolds and preferably a pair of latex gloves and
barrier cream under them) - use the brush to help you position and
smooth the patch. you shouldn't need to put any more resin over it at
this stage but take some care to make sure it is down properly with no
strands hanging or anything, which might require you to wet the brush,
but try and avoid the urge to paint resin over as you will most likely
move the patch. When set check that the edges are smooth - you may need
to sand off spiky bits and stuff to make the inside nice, when happy if
there are roughish bits you might want to paint a bit of resin over, but
remember you need to key up the patch if it is going to stick!

Not sure what to do about the star at the skeg, I suggest you cut it
back with P400 and report your findings! If a gel repair is going to do
it, make sure you sand it so that you bevel the edges .

JIM

Mike Buckley wrote:

Ewan Scott wrote in message
...

Me Again.
This time I may proof read this.

I followed Richard Hayes instructions pretty much to the letter.
I ground the beast out with a Dremmel and found the cracks much deaper
that I previously thought. I ground through the boat in two spots.
I put some packing tape inside he hull to keep things in order as I
worked the ourside and got the gouges filled.
It is not going to be perfect but it is not bad.
I had about 10 yards of 10 Oz Fibre Glass cloth left over from a canoe
I built a long time ago. I used a little of that to reinforce the hull
under the repair.
Seems to work.
I am wondering how you get a reasonable gell coat back on there or do
I just paint it.

Right now I am not sure but I should just have reinforced the inside
and painted the begger. I am told I shuold have just left it because
it can last that way for years and only requires that level or repair
when it actually starts to break down

During my efforts I found another less pronounced star crack around
the skeg box.
That one I likely deserve as I remember one drop os some consiquence.

Are the NDK boats prone to star cracks?? I have one other glass boat,
It has one well deserved crunch but no star cracks. It is much more
flexable all over. The NDK has been babied.

Star cracks are gebnerally quite small and IIRC occur when the surface
has had a good dunt. The substrate matting flexes and the top coat gel
cracks.

By th sounds of your first patch you needed to repair the hull anyway.

These smaller ones - I'd just rough sand them, and paint with gelcoat.



You'll not like this, having "done" your repair, but the next time round I
suggest you do all your prep work and then use packing tape to cover the
OUTSIDE of the hole. Now apply your gel coat (colored as necessary) from the
inside and leave o/night. Now build up your repair from the inside using
your chosen glass material. When you remove the packing tape you'll have a
nice smooth external finish.

I've done substantial repairs with this method with extremely good results,
including rebuilding the foredeck of a general-purpose boat to the extent
that the job was done in 3 stages to cope with all the different angles.

If you have a rummage in the forum/community on the ukriversguidbook site
you'll find an excellent summary from one Jim Wallis on the subject of the
appropriate materials to use. He sometimes looks in on what remains of this
group so maybe he'll post a summary.

The packing tape trick can also be used to good effect on simpler external
repairs using gel coat or gel coat filler (chandlers will have it) by
applying it on top of the gel coat and leaving it until the gel has set.

Mike.



Thanks guys.
The cloth I put on the boat was in the inside, The repair is looking
OK. I don't have the facility to do the job I would like to do.
The boat is back in the water, cutting through a skim of ice in
brackish water in Conception Harbour.
A little more work needs done on the gell coat but that will wait till
I have a place to lay up the boat for a week or the weather clears up.
We had 8 inches of snow last night and my car was drifted in . I had a
lot of snow to shovel.
Thank you very much all of the replies were helpefull and VERY
knowlegeable.
THanks again
Alex