Deck/Core Repair - with pictures
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Aaron
Jul 11, 2016, 4:32:56 PM7/11/16
to J/92 Owners
Just thought I'd share the work I'm doing on my J/92 in case others have silly ideas to try it also.
This winter the two soft spots in the deck pushed their way up the work list as it became apparent that they needed attention. In both places (ahead of the chain plate and the cockpit floor) the water was getting inside the core in an area where there was no deck mounted hardware. The water got in via some spider cracks that I think were caused in the manufacturing process - too much gel coat and too little glass. In both cases the moisture meter (an electrophysics) was pegged around one area, and then you could follow the water as it moved through the cuts in the balsa core. It really is amazing how far the water will go in one direction and not in any other.
In an attempt to control the job scope I didn't want to add replacing large areas of non-skid to the list. So I tried two different methods of attacking a core replacement - one to cut the bottom layer off (to save the top layer and non skid) and to cut the top layer off and reattach it. Working from the top is obviously easier, but working underneath against gravity wasn't that much harder.
Process pretty much went something like this - cut out a section of skin, remove the wet core, put down a layer of glass with the new core to ensure a good bond, vacuum bag until it sets up, then build up the new outer layer (reusing the old section for the deck) and vacuum bag everything together. Any new glass that was added was biaxial fiberglass and it appears super strong and easily wets out. If you've never used a vacuum bag for fiberglass, you're missing out. The results are amazing with no voids and a great surface. Yes, it does add to the repair cost and slows things down as you have to use slow hardeners. But the repaired sections feel stronger than the other deck sections using conventional layups.
Here's a photo album along with a video of a small core section I pulled out. https://goo.gl/photos/8dkHRSKbrwMcHGuH8
I know I'm not the first one to do this, but wanted to share with everyone that while we're all concerned about the holes for the deck hardware, to also monitor those seemingly innocuous small cracks in the deck. They can really let the water in!
This winter the two soft spots in the deck pushed their way up the work list as it became apparent that they needed attention. In both places (ahead of the chain plate and the cockpit floor) the water was getting inside the core in an area where there was no deck mounted hardware. The water got in via some spider cracks that I think were caused in the manufacturing process - too much gel coat and too little glass. In both cases the moisture meter (an electrophysics) was pegged around one area, and then you could follow the water as it moved through the cuts in the balsa core. It really is amazing how far the water will go in one direction and not in any other.
In an attempt to control the job scope I didn't want to add replacing large areas of non-skid to the list. So I tried two different methods of attacking a core replacement - one to cut the bottom layer off (to save the top layer and non skid) and to cut the top layer off and reattach it. Working from the top is obviously easier, but working underneath against gravity wasn't that much harder.
Process pretty much went something like this - cut out a section of skin, remove the wet core, put down a layer of glass with the new core to ensure a good bond, vacuum bag until it sets up, then build up the new outer layer (reusing the old section for the deck) and vacuum bag everything together. Any new glass that was added was biaxial fiberglass and it appears super strong and easily wets out. If you've never used a vacuum bag for fiberglass, you're missing out. The results are amazing with no voids and a great surface. Yes, it does add to the repair cost and slows things down as you have to use slow hardeners. But the repaired sections feel stronger than the other deck sections using conventional layups.
Here's a photo album along with a video of a small core section I pulled out. https://goo.gl/photos/8dkHRSKbrwMcHGuH8
I know I'm not the first one to do this, but wanted to share with everyone that while we're all concerned about the holes for the deck hardware, to also monitor those seemingly innocuous small cracks in the deck. They can really let the water in!
Joe Cooper
Jul 11, 2016, 4:55:06 PM7/11/16
to j92o...@googlegroups.com
Good looking work mate.
Interesting the use of the chopped strand glass, used I am told to give a tooth to the subsequent composite layers.
In the video the bit you are squishing is Balsa? Yikes.
Dead right on the vacuum bagging approach, makes for a much nicer stronger job and makes finishing and surfacing soon much easier.
Jamestown dist. has a pretty serviceable vacuum pump $400 (price 18 months ago) that I have and use on the refit if my mini.
I could use just the regular WEST hardener but I was working in the winter in a shed outside so 50 degrees with the heater was a sunny day.
It makes the work look like it was done by someone who know what they were doing….
Well done Aaron.
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Michael...@aol.com
Jul 12, 2016, 7:52:07 PM7/12/16
to j92o...@googlegroups.com
Nice job Aaron!
Here is a link to a portfolio of Vixen's repairs. We
first removed the moisture before performing any surgery. It was
easier to handle dry core rather than wet. When free of moisture we found that
the soft core was not necessarily rotted. That which was is easily
removed. Water evaporates at about 100 deg F in a partial vacuum, so using a
vacuum pump on every opening in the deck while sealing and applying heat on
the underside , it took about 24 hrs to dry the boat. You know it is dry when
the condensate in the tubing stops flowing. You can see just some the
plumbing in the photos.
Every piece of hardware was removed and every penetration in the deck was
excised used a die grinder: the hole in the top glass was opened to a larger
diameter, the bottom glass layer remained small so it could be sealed easily.
The result was a cavity in the form of an annulus, a much larger diameter seal
in the opening than just drilling a straight hole.
The previous owner(s) fornicated up when installing a fill pipe for a
new fuel tank. The installer just cut a hole in the deck. The result was a
soft and partially rotted core the extent of which you can see from the
surgery.
We didn't have vacuum bag equipment, so instead applied pressure using the
technique shown in the photos. Solid as a rock she is now. Aaron 's boat and
Vixen rock side-by-side.
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