Cabin sole repairs

I’m going to be looking at an older Corbin 39 that has soft spots in the cabin sole. I’d like to know how the boat was built to determine how serious the damage is. Could you please tell me, if in your opinion, if soft spots in the cabin sole are structural problems related to rotted thwarts (knees) or a cosmetic problem? I was “told” the boat was a factory boat, but the owner is dead and his widow may not really know. If the boat has structural problems I probably won’t buy it, if all I have to do is replace some flooring, I’ll try to buy it. Thanks & Sincerely, Tom Hally.

a. I don’t know how the factory-built boats dealt with the cabin sole. In my boat the supports, or floors, are like vertical mini bulkheads made from 2 layers of 3/4″ mahogany ply that were bonded [together] with epoxy and then covered with fibreglass. Then a piece of solid mahogany, about 3″x3″, was attached to the top to span the hull. I made most of my cabin sole consist of removeable panels so that the bilge and hull could be inspected. This is particularly important in the event of external hull damage. If you are keen on buying the boat I suggest you ask the owner if you can cut out a section of the sole. This is fairly drastic but I can’t think of another way to resolve the question. You should be able to advise the owner that other potential customers will have similar concerns. The cutout panel should obviously be in a position that would allow it to be used as a future keel access hatch [and for storage]. Regards, David Salter (#050, Opportunity).

b. Don’t know what to make of this ! Certainly it’s nothing structural, just an underfloor issue. maybe ?? the plywood got soft somehow … ? or maybe it was too thin in the first place ? My sole is on 3/4 plywood. Sorry I could not contribute much. Cheers, Frank B. (#186, Visitant).

c. Recommend that he take a look below the floor boards to see if there is an obvious reason for the soft spots. If he is still interested in the boat after that then a surveyor can help him determine whether this is a big or little issue. Stephen L. (#187, Toboggan).

d. Our 1984 Corbin #153 also has soft spots and one place where you can see the sole was replaced. Getting a closer look, it seems to just be some sole lamination deterioration and not structural (a future project I’m sure). In one spot it looks like some penetrating epoxy was used with limited success and some discoloration. Gene & Patti S., (#158, Swell Dish).

e. Many people say their boat is factory built but it is not always the case. The flooring is built with 3/4″ mahogany plywood, covered with 1/4″ teak and holly floor. It could be that one of these two parts has separated or is rotten. I would doubt very much it is structural. There are openings in the floor that will allow you to check for rot from under the floor. Have a wonderful day. Marius Corbin.

f. It’s going to be difficult to tell what the issue is and how extensive it is without taking a good look. Then there’s the question of differences in how each boat was built. When we purchased our Corbin, we had the sole factory-installed. In this case, the knees and stringers below the sole were well encased in fiberglass but the sole itself was just raw marine plywood without any sealant applied to the underside, allowing for the potential for rot. We didn’t have issues during our time owning her, but who knows now. Chris Reynolds, Formerly (#083, Tamalmar).

g. If factory finished, the supporting floors should be of substantially thick solid mahogany beams and thick marine mahogany plywood bulkheads. Because most of the boats were sold in various kit plans it is impossible for me to answer your question. However, if the joinery inside looks professionally done then the boat was probably factory finished. If the boat was kit finished only a careful inspection of the supporting flooring (the supporters of the sole) will tell if the problem is structural or cosmetic. The entire interior of my boat was finished by the previous owner and is still very solid despite the intrusion of fresh water on at least two occasions when the hull up to the salon sole was immersed in fresh water. Your problem is probably cosmetic. Inspect the flooring. Also, smell for rot. Lester H. (#010, Insouciance).

h. Attached are two pictures (I thought that I had more) of my boat under construction at the factory in 1984. The first picture shows the forward bulkhead in the main salon. Looking closely, you will see just aft of the main bulkhead, a stringer glassed to the hull; there will be one glassed to the starboard side also. Salon Sole Support Stringer Fwd There is also a bilge bulkhead glassed into place a few feet behind the main bulkhead. The second picture shows the underlayment plywood (appx 3/4″ marine grade) sole resting on the above-mentioned stringer and bilge bulkheads and glassed into place with tabs on the outboard edges. Salon Sole Plywood The underlayment plywood sole was secured to the bilge bulkheads, I believe, with Morebond and screwed down with SS screws. There would be another bilge bulkhead between the two tanks seen in the picture. All of this created a solid floor, covered with an appx 1/4″ teak and holly plywood which was secured with Morebond. I would suspect that water, perhaps from a leaking tank, may have somehow collected onto the plywood underlayment between the top covering teak and holly and the underlayment. This, over time, would cause punkiness and softness. Just a wild guess. Doug Archibald S/V #158, CHAOS !! (ex) [Ed. Note: The two pictures show a very solid substructure that not only supports the cabin sole but makes the hull more solid and rigid.]

i. I have hull #025 and have been installing new sole for awhile now. Thing is on my Corbin the sole is not structural but can add support to the overall stiffness. I would inspect the soft spots to see if it is in the stringers or supports. More than likely the sole is the issue. I am using an African rosewood that can be submerged in water for long periods without ill affect with only teak oil applied. Even if it were a small amount of rot due to poor sole installation it would not scare me from the purchase. These Corbin’s are literal tanks of the oceans and if water intrusion is caught early and repaired properly the boat has many more oceans to cross…….Fair winds, Keith Boettger (#025, Agape).