J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Core Help!

Ok guys I need your help. I have been looking at old forums and I need to know what to do about my wet core. Velocity Girl has fairly high levels of moisture in the bottom aft of the keel. I have drilled test holes and found health yellow balsa. I don't have any signs of delam, but I am concerned enough. Do I have to replace the core or can I get it dried out. I have two boat builders here who have two ideas. Boat builder A says that vacuum bagging (drying out the hull) is no good. Builder A says that drying it out should do the trick. My concern is I can't really have the work done until the fall. The boat has to go in the water this year as it will be my home for the months of July and August. Thanks for all your help guys.

Velocity Girl
#278

I have the exact same problem as you can see from my recent post in this thread: https://j30.us/ubbthreads/ubbthreads.php/topics/5859/Draining_boat_by_drilling_a_ho.html

After drilling to drain, I've reglassed the hole and faired it. I sprayed the bottom with VC Offshore last night and am working towards launching next week.

I'll be speaking to a friend of mine who is a marine surveyor this weekend on what my options are and the long term impact, then post the results here.

[This message has been edited by Rhapsody #348 (edited 04-17-2008).]

Obviously, wet core is bad. I think, though, that it's easy to exaggerate the problem. If the core is bright, then it isn't rotted. Once balsa starts to rot, it will darken considerably.

How did you determine the moisture level? If you're using a moisture reading, there are a number of things that will artificially peg the meter, such as metal or interior bulkheads/furniture.

If the core is dry I would suspect the meter or, as IT folks say, it could be a U.S.E.R. error.

If the core is damp, then water is coming in from somewhere. As this is the hull, check through the through hulls and anywhere else water may ingress.

Once that's done, you can expose the core and dry it out. That can be as simple as tenting the area with plastic sheeting and aiming some heat lamps (at a safe distance) at the affected area. It will take some time so my advice would be to mitigate the problem, go sailing this season, and dry it out over next winter (if it really is wet).

Forget the vacuum bagging. It'll work, but it's expensive. For minor issues, tenting will work fine and for more serious core problems, vacuum bagging won't fix it (the core needs to be replaced).


[This message has been edited by Jason King (edited 04-17-2008).]

Thanks guys...I know the core is wet because I drilled holes in the bottom of the boat and the core came out wet. I know that the initial point in intrusion on the port side was the exhaust. The last owner repaired the lower half of the transom on the port side to correct the leak. He did not fix the bottom core though. the Starboard side seems localized to the a section about 4 feet in from the trasom to about even with the keel. All the Balsa I drilled was yellow except for a a small patch in the starboard side in the storage locker. My initial plan is to button her up for the season, fair the bottom, keel and rudder, and put down a new layer of barrier coat and VC offshore and go sailing this summer. Next fall I plan on finding inside storage and exposing the core and putting heat and a fan on it for the winter and see where that gets me. Long term I may consider re-coring because I love Velocity Girl and eventually want my ashed splashed in lake ontario off her transom! Ha ha ha. Keep me posted on ideas.

Did anybody ever hear about that guy who used the industrial house drying unit to suck out the water? Did it work? I would like to avoid re-coring if the balsa isn't rotten.

HHSA
Velocity Girl #278

Checkout the pictures on my blog phatom364.blogspot.com I recored about 9feet from the transom forward. I went from the water line to the center. Even core that is yellow is soft. It my opnion that even drying it won't return it to its orginal strenght. Recoring isn't hard, it's the fairing afterwards that labor intensive. I"m doing almost all the work myself. If you can find friends with free time, it will be a lot easier. Sail it this summer so you have memories to keep you motivated next winter.
John

In order for a barrier coat to be effective the boat, including the laminate, needs to be bone dry. Skip that step until you fix the wet core.

Jason & John - for areas where you need to recore from the outside, can you cut out sections of the outer skin with a dremel tool or router and pull the skin off? Once the skin is off, then is it possible to recore and reuse the cleaned up skin sections to minimize the amount of fairing you have to do? How do you get the original hull form and keep it symmetrical port / stbd?

On removing the sole - how do you do this so it can be reused with minimum damage?

I'm so close to getting in the water and the bottom looks awesome after spraying VC Offshore last night. I started wet sanding tonight. What a bummer if I need to rip open this baby next fall.....

I used a skill saw and a roto-zip with a ceramic blade to cut the outer skin. I then used a pry bar to remove the skin and a chisel and hammer for the core. The skin does not always come off whole. It depends on the degree of lamination or delimination. I think you have stronger hull if you use new biaxial cloth to replace the outer skin. I use 2 layers of 3/4oz cloth with mat attached. In hind site I problaby should have use a light cloth for the second layer. It on the verge of being to thick. The inner hull maintains the shape, I should have made a few templates before I began to make the fairing job easier.
The cabin floor is screwed and glued to the fiberglass, making it virtually impossible to remove in one piece. I ended up cutting, through the first layer of glass and taking the whole section out.

Last Spring when I had a large section on the Starboard side re-cored, they used a skill saw and cut a 3' x 3' section into a grid of about 4 inch squares. Then used a hammer and pry bar to remove the skin and core. It was not easy so I don't see how getting off a large section of skin whole and reusing would work. I actually had about 12 feet for and aft to replace. They did a 3 foot section, skipped 3 feet and did the next 3 feet. When those 2 sections were pretty well repaired, they moved the jack stands and did the other 2 sections. When all four sections were re-glassed, they used a long board to fair the sections together. It was a lot of work, but it turned out quite well.

Here is a link to where I described the process; https://j30.us/ubbthreads/ubbthreads.php/topics/1864/Hot_Vac_Hull_Drying_Anyone_tri.html

AC Rauzer II #448

"Did anybody ever hear about that guy who used the industrial house drying unit to suck out the water? Did it work? I would like to avoid re-coring if the balsa isn't rotten."

Yes, this approach worked. The boat that was dried had wet core throughout the entire bottom (when test holes were drilled, water came out in some areas). Holes were drilled over the entire bottom and rotten areas of core were removed. We were able to take the boat from a virtually saturated state, to acceptably dry in about 3 weeks. The down side is that this equipment is extremely expensive to operate. Had the owner not been a friend of ours the cost of drying the boat would have exceeded its value. When the boat was dry, it was left with thousands of small holes into the core. The only way to fix this was to fill them all and vacuum bag a layer of thin fiberglass cloth over the entire bottom. This turned into a pretty major project and although it only took 6 weeks or so if you have the ability to keep your boat out of the water all winter, it could be done without the drying equipment.
It sounds like people are looking for a simple solution to dealing with core moisture. The reality is that all of the solutions are pretty huge projects, and its just that some of the people doing them are willing to take on jobs of this scale. If you can put your boat inside a heated shop for the winter and drill holes (1/8" or so) on a 1" pattern over the wet areas you will be able to remove the moisture, then you will have the task of filling all the holes and fairing the bottom. If you are looking to do it quickly the easiest way to deal with it is to map out the wet areas and remove them and replace the wet core. It;s been said before, but its worth repeating. The most important step is to definitively stop the ingress of water.

my $.02