Bill,
I was looking at the pictures on your blog; the ones of the blisters in your hull. I have had blisters on the port side of wildcat for several years. I drilled out the blisteres to drain them. And then, using a dremmel with a bone drill, drilled thru the fiber glass into the core. There was no water in the core. My point is that before you start cutting into the core from inside, you may want to see if there is water in the core at few of the blisters.

Hey Bill,

Just took a look at your blog. That is a lot of marker on your boat. Do you plan on completing all the work before spring next year?

Jason

Russ - I did drill a couple of pilot holes into the core where the blisters were. I was expecting to get brown mush, instead I found firm yellow, but wet core. The moisture meter is pegged high in this area (as it is on almost the entire stbd side below the waterline).

This weekend I'll be going over the boat with a friend who makes heaters for drying out core and before I make any cuts, will wait to see what he suggests for areas like that. In any case, the transom is delaminated with a hollow sound, so it will get cut open for repairs no matter what.

Jason - I want to splash next spring and if I delay a month (go in late May instead of the normal late April), I'll do that.

Bill

[This message has been edited by Rhapsody #348 (edited 10-21-2008).]

I've update my Blog with the latest progress. Grinding out the transom from the inside is taking longer than expected.

Question - The transom chainplates and rudder are strengthened with 1/2" plywood glassed over the balsa. When others did a transom rebuild, what did you use to replace the plywood? I was thinking it may be better to glass in a piece of similar sized G10 both for strength and guaranteed no moisture absorption.

Blog link: http://j30rhapsody348.blogspot.com/

I replaced the starboard chainplate doubler with 3/4" cabinet-grade ply, glassed over it. Although I'm finding a good bit of my transom to be rotted, the area around the chainplate was OK when I did the repair last Spring.
It's been about 3 weeks since I cut several openings in the inner hull in the transom and forward to the front end of the quarterberth. Using a small heater, the core seems to be drying out quite well. The balsa was absolutely saturated when I first opened up.
This past weekend, I drilled into some blisters located under the cooler - the balsa is yellow but wet, as you described.
Still trying to find a warehouse to move into for more thorough drying.

Peter - thanks for the info. I showed the buildup on the chainplate and behind the rudder gudgeons to a friend of mine who used to build boats. He was amazed that the boat was built with plywood over balsa core for areas that have through bolts. The reason is the balsa core does not offer strength against compression when the bolts are tightened. He recommended that for the areas where strength are needed, glass in some flat fiberglass sheet and build it up with biaxial cloth & resin so it is the same thickness as the balsa around it. Here is the material he recommends for the fiberglass plate: http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=63414585

This is the recommendation he made:
Make up the difference with wet laminate - 3 layers beneath the Fiberglass block plus 3 on top for strength. These layers will be just extra reinforcement on top of the 2 layers across the transom prior to balsa and the blocks plus the 2 layers over the top of the balsa and blocks. Hope this makes sense but this approach will be the simplest and will be stronger by far than what was there.

Note that he recommended that I add a couple of layers of 17 oz biaxial mat/cloth over the inside of the exterior skin since it is so thin.

I'm still in the grind out the old stuff phase :-(

Brief progress report. Together with Breezin' (#454), Blue J has been moved to a warehouse where we can work on them. We were supposed to have heat, but that is another issue.
I've cut more inner hull and exposed more wet balsa. A larger cut inside the transom exposed some more rot and just wet balsa. I'm surprised that the balsa at the top of the transom was very wet -- I still think there must be other sources of water which must be sealed or this effort will be all for nought. I also removed the propane locker drain from the transom -- rotted all around, so there's another source, anyway. Note -- the outer skin appears to be thicker than the inner.
We were attempting to map the hulls with a moisture meter, and just for "calibration", put the meter next to the drain hole -- it showed green (OK). It also showed green in areas where I got very wet core samples, and red on Breezin' in a couple areas near the centerline which are solid glass. We concluded that core samples are the only reliable indicator.
Continuing to try to dry things out with a small cabin heater and trouble light, stategically placed. Using a probe-type moisture meter, the areas I exposed last month are completely dry, and those opened last weekend still show some moisture.
Looks like drying will take a long time.

Peter - I found the moisture meter readings to be very reliable on locating the "boundaries" of moisture. The one I'm using is a JRC with traditional analog meter that I borrowed from a friend who is a Marine Surveyor. Like you I found the only good way to see if the balsa is rotted is core samples.

I also found rotted core at the top of the transom on stbd side. My plan is to inject the upper inch or so with thickened epoxy to isolate the new balsa I'm bonding in. The seem between the transom and rest of the boat will also be setup so the balsa is isolated on both sides.

It's interesting that your outer skin was thicker. Mine was like paper, so before bonding new core I've bonded two layers of 17oz biaxial fabric to strengthen the outer skin. Take pictures - you can see some on my blog at this link: http://j30rhapsody348.blogspot.com/ although I haven't done any work in a couple of weeks. I wish I had the inside work area you had! Mine is being done outside and I will tape fiberglass insulation to a section on the outside, then heat from the inside before doing any bonding work.

On a different note, I just got my rebuilt prop back from Martec. They rewelded the stops, overdrilled the pivot pin hole, machined new edges and polished it like a mirror.

Bill, thanks for sharing this information. What a project! Good luck and keep us posted.

That prop looks friggin sweet. On a side note, I still have water seeping from the cracks in the doghouse seam that I have mentioned before. When I probed it looked like glass/no balsa however, I have dark water seeping from it. Does anyone know if the vertical doghouse striped portion of the cabintop is cored?