Structural Moisture Remediation

 

The reinforcing structure (bulkheads, stringers, etc.) in many/most fiberglass boats is made of wood . . . plywood for the most part.  The tendency for wood to retain moisture and eventually rot, is a major concern as a fiberglass boat ages.  During the survey of my Formula 330SS, the surveyor noted higher than normal levels of moisture in the center section of the engine compartment bulkhead.  While the bulkhead was solid, the moisture would need to be monitored and corrective action taken as needed.  It was not a show stopper for the purchase of the boat, as many boats of this age would have similar issues, but something that would need a close watch.


Among the boat restoration community, there are those who say that nothing can be done to remedy high levels of moisture in a boat’s structure and eventual replacement of the structure will be needed.  This replacement process is often referred to as a ‘cut and gut’, and is a massive undertaking.  Performing a ‘cut and gut’ in a small runabout boat, is manageable, although time consuming, but in a larger boat is an overwhelming task.


The challenge with wood structures in fiberglass boats is that the wood is encapsulated in fiberglass, at least it should be.  The encapsulation is supposed to isolate the wood from moisture.  However, moisture does permeate fiberglass if exposed to water over long periods of time.  Additionally, any imperfections in the fiberglass encapsulation that are present or appear will provide a more direct path for moisture to enter the wood structure.  If a wood structure is allowed to attain moisture, the wood acts like a sponge and does not readily release the moisture due to the fact that it is encapsulated in fiberglass and has no way of evaporating.  This is the main reason why some say that you cannot do anything to remedy elevated moisture once it starts, and an eventual repair/replacement of the effected structure will be needed.


I am of the mindset that moisture can be addressed, and a fair amount of remediation can be done to a boat’s structure to avoid the massive undertaking of a ‘cut & gut’.  So, with the information from the survey, I set out to assess the moisture levels within the structure of my ‘new-to-me’ Formula 330 SS and apply some corrective action.  I have read some articles about using Ethylene Glycol (a.k.a. Automotive Antifreeze) as a rot treatment and preventer in wood.  I used some EG on my Formula 242 bulkhead repair to treat some of the structure that was wet, but still useable.


I purchased a wood moisture meter and drilled some test holes in various areas of the boat.  Prior to testing the boat, I also tested a few random pieces of wood for reference purposes.  Pictured below are the various readings from the test holes in the area where the high levels of moisture were noted.  This should give an idea of the severity and propagation of moisture throughout the structure.

Here are a couple of reference readings from samples of wood exposed to the air.  New and relatively dry wood was reading about 7% and older fairly moist wood was reading 23%.  Pictured below are readings from various parts of the structure in the engine bay.

The main source of the problem - center of the bulkhead 43% very wet.  Further away from center on the bulkhead 28%.  Port Engine Stringer 21%

Center Engine stringer - 33% (wet) Starboard engine stringer 17% and spacer 26% (where there is a crack in the fiberglass).  The crack was probably due to the wood swelling and freezing during the winter months.  Below are some images from the cabin/V-Berth.

Floor of the V-berth (fairly dry) at 15% (above left).  All of the readings in the forward area were under 20%, which seems to be fairly dry for 15+ year old encapsulated wood.  The forward bulkhead (above center), up near the anchor locker, had water trapped against it during the pre-purchase survey, due to the fact that there was no limber hole for drainage (see above).  The surveyor remarked that this bulkhead was ‘wet’.


I had removed all of the water from this compartment a few weeks prior to taking the moisture readings and it was surprisingly ‘dry’, giving a moisture reading under 20%.  I have also noticed some spider cracking on the outside of the hull in the area where this bulkhead has dried out (above right).  So, this would indicate that the water had been present for quite some time.

Based on the moisture readings throughout the engine bay, I was able to construct a diagram, showing the concentration and propagation of moisture (pic below right).  It appears that some immediate remediation is needed in the center of the bulkhead and that the center engine stringer is feeding from the high concentration in the center of the bulkhead.


So, based on these very high readings in the center area, I started the E.G. treatment immediately. (pic below).  This will feed ethylene glycol into the bulkhead over a few weeks time in order to stop the wood from rotting.

REMEDYING THE MOISTURE


I plan on performing a multiple step process to resolve the moisture problem in my boat and prevent future issues.


1) Drill - holes in areas where moisture needs to escape, add limber holes, etc as needed.. . . . use a shop vacuum to pull any excess water out of the worst areas.  This will give the moisture an escape route that it currently does not have.  The limber holes should prevent water build-up in the future.

2) Dry - heat those areas for an extended period, check the moisture content to see that they are dry.

3) Treat - Once dry, apply Ethylene Glycol to the areas, let soak in for several weeks.

4) Dry (again) - dry out the E. G. treated areas with heat, re-check moisture content.

5) Seal - all the holes while heat is still applied . . . this should ensure that the remaining moisture content is at its lowest.

6) Check - take some readings each year to see how things are doing.

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