J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Brass Monkey Recoring Update

As I consider recoring around the keel and under the floor of hull #62, I contacted Rich, the owner of hull #294 for an update on his recoring work. His blog ends with the tear out but gives no details on the rebuild. I was worried that there was no rebuild, but happily it is complete.

http://j30.us/J30%20Rebuild/Inner%20Laminate.html

Rich also offered some advice and I asked if I could post it for him. Says he is too busy to update the blog. He asked me to include this disclaimer:

"Feel free to share it. It's rough, but may be useful to some.

Please also include a short disclaimer indicating that 'results may
vary' and 'attempt at your own risk'. It was a hairy job and I'm a
skilled fabricator.


Rich"

Then the details:

"Hey Mark,

Here's the short version:

Prep:

1) Rip out the cabin sole
2) Chip out the vermiculite
3) Use a circular saw and pneumatic chisel to cut out the inner
laminate and stringers in the sump
4) Sand the hydrolyzed resin and glass from the outer laminate

(you'll probably want to do this in smaller sections. I did the entire
sump on one side, then the other so I had support for the keel
(critical!)

Layup:
- This layup works in two cure cycles. You want to do the least number
of cure cycles possible so that you aren't bonding to cured epoxy more
than you have to. You are replicating the original structure, and on
changing things that provide more strength - better glass (biax
instead of roving), more glass (thicker), epoxy only, corecell instead
of balsa (so you never do this again), etc.

Cycle1:
1) Cut a shitload of corecell squares using a band saw. I believe they
are 1.5x1.5 square
2) Laminate a layer of biax onto the inside of the outer laminate.
This outer laminate is very thin and if your core has been wet, it is
partially hydrolyzed and not strong. The Biax is way stronger than the
original chopstrand and weaved glass.
3) Coat each corecell block with thickened epoxy (milled fiber or even
lightweight filler). This will make sure that your core doesn't suck
the resin out of the biax and will give you a strong bond to the outer
laminate
4) Around the keel sump, you will take the core right up to the edge
of the sump per the original structure
5) Allow to cure

Prep2:
1) Chamfer the core at the edge of the keel sump. You want a nice
round transition for the inner laminate to lay over. Hard edges create
weak spots that don't bond well.
2) Sand prep every thing and get it really clean

Cycle2:

1) Lay layers of pre-wetout biax into the keel sump, you want to put
the smallest pieces of glass on first, with successive larger pieces.
The idea is that you want to have each piece of glass have its own
bonding surface to the outer laminate so the loads are distributed
through all of the layers of glass, not just a single layer from the
bottom of the sump to the edge of your repair.
2) Allow to cure

Once you do this on both sides, your keel sump will be VERY strong and
built more heavily than the original. Don't be stingy with the glass
and don't worry about wetting out the glass *too much*. It is ALWAYS
better for the layup to be a little resin heavy than to be too dry.
You want every piece of glass to be beautifully clarified before you
lay it down. (it should appear completely saturated and clear)

For the stringers, I made more stringers than the original. My
stringers were also taller and therefore reached out to the settees on
either side. You want this shit strong! I fabricated the stringers out
of roving and epoxy using simple forms I made out of MDF. I used
cardboard to template them and cut the final shape on a band saw (get
a few blades). To put them in make a VERY thick batch of epoxy with
milled fiber and use this gunk to glue them into place. Use extra
filler and draw fillets along the stringers so that you can laminate
glass over them (with a nice filled radius). I used roving to
reinforce the stringers. They are VERY strong. I also did the gluing
and the laminating in a single cure cycle so it was all bonded
together fiercely.

The stringers also were extended back to the engine (instead of the vermiculite). With a little work I got them leveled and they now support my floor nicely. The best part is that you can take up the floor and clean the shit out of the bilge. My boat smells like 'nothing'; not something that can be said about many j/30s."

An update. We have decided to try to get the boat back in next year. Much to do and have begun the recoring work around the keel. The rest of the boat's dry now, deck, hull, transome, cabin top, ..., but I can't get around the keel to dry out. Gravity I suppose.

Plan to follow the steps used on Brass Monkey above. Half the floor is up. The floor's balsa core is the consistency of cardboard at best on down through mush, all the way to dust. Am trashing the floor and will build a new one. Been carving into the innner skin and balsa around the keel. Hard work, but it's coming along.

Will recore with Core-Cell. Expensive, but I won't have to do this again. It's not as strong as balsa so I dug into the Scantlings calculations. See if I needed to beef anything up to compensate.

The keel sump is bonded in with enough glass to meet open ocean Scantlings without the core. The thick inner skin is a lot wider than required. Guess that's why my keel is solid even though much of the core around it's about as strong as oatmeal. Suppose I also have a good idea where some of the missing weight came from in a J29.

So, I plan to replace the thicknesses that were there with biax, epoxy and Core-Cell. The verm is all headed for the trash. Not as bad as some I've seen in J24s, seems like more resin less verm, but nasty just the same. Will replace it with stringers to set the new floor on.

Will post some pics of my boat's "basement" in a short while.

My floor is out and I'm cutting and removing balsa.



I don't think you'll like what I've found in the "second bilge" area. The vermiculite under the floor in front of the step was nasty. Black and smelled like disel fuel. Some was well attached to the hull and some wasn't. Looks like this:



The inner skin by my sink appears to be made of a single layer of 8 once matt with a single layer of 24 ounce woven roving on top. That's it. Looks like this:



There are small black spots on the inside (the balsa side) of the skin. They're at the places where the edges of the glass ribons meet in the roving. A little hard to see but looks like this:



Some of the core was black ad nasty just like the vermiculite. Right here in this area, the core smells like disel fuel, just like the vermiculite. You can see a bit of that still attached to the inside of the inner skin above.

Most of the balsa is actually OK. Dry and structurally sound, but it has a stain pattern. Black spots that match the spots on the inner skin:



I disected one of the black spots in a sound and dry piece of balsa. The black stain runs from the inside face of the balsa toward the outer hull.



Concusion? The inner skin is so thin it has allowed water, and some disel fuel, to soak through from the saturated vermiculite.

I warned you that you wouldn't like this.

I will be removing every cubic inch of vermiculite from my boat.