checking core in transom

wanna-be

New member
hopefully wanna-be will soon be havea-be but first how do you check the transom for core damage, or any other fault in structure of c-dory Thankyou
 
The biggest concern with regards to the core is water intrusion in the core due to a breach in the fiberglass epoxy layer. The breach could be due to a crack or a hole drilled for some other purpose (mounting something etc). In many cases, a small, poorly sealed hole doesn't cause too much damage as the balsa core is "end grain" - e.g. the grain of the wood is perpendicular to the surface and hence water doesn't wick too far. However, holes that permit the entry of water over a long period of time will eventually allow the core to get wet farther away from the hole. Also, in surfaces that are curved (like the floor) the core is siped (slots are cut in it) to allow it to bend. Generally these slots are well filled with epoxy during layup but sometimes a channel remains that can carry water far away from the hole. For the most part, we haven't seen that issue in C-Dory's.

However, to answer your question about how to detect damage, the best way is with a moisture meter that measures the amount of moisture within a solid. A good surveyor will have a moisture meter and should check the transom and other cored areas of the boat (especially those with penetrations).
 
And here's a good selection of Moisture Meters. As you can see, some of them can be very pricey. The less expensive ones actually have pins on them that penetrate beyond the fiberglass and into the core. Those minute holes then need to be plugged up themselves or you've created a new way for water to get in.

Some say you can detect wet core by tapping with a small hammer but my ears aren't that good!

Charlie
 
Various cores on the Transom--some plywood and some foam. None I have had so far have had Balsa, but it is entirely possible that some do.

I would look at any transducer mounting holes--remove the screws and look for moisture. Another place is the drain plug. That is the most likely place to find moisture. The other place is if there are any cracks in the cap--or where the hull to deck joint is. Generally the transoms have not had major issues.

Moisture meters will read high with metallic bottom paint or near metal fittings, so this can be falsely high....I have not tried any of the cheap meters--but they may work fine....
 
thataway":3jxxbydb said:
Various cores on the Transom--some plywood and some foam. None I have had so far have had Balsa, but it is entirely possible that some do.

Just as a data point, since it just so happens I've been over-boring and filling holes in the (thankfully dry) transom of my 2002 22 Cruiser this week. Between the transducer holes, the kicker-mount holes, and the swim-step mount holes, I've covered a good bit of area side-to-side and top-to-bottom, and so far I'm pretty sure it's all been balsa core. As Bob pointed out though, it can vary.

I say "pretty sure" because I've never actually drilled into plywood core (but have worked with balsa). Actually, I was somewhat apprehensive about how easy/hard it was going to be to ream out dry plywood around the holes (whereas I'm familiar with balsa and don't find it too difficult). I presume plywood would seem like plywood whereas what I've got seems just like balsa (comes out in vertical-grain "bits").

One more note: I think typically the pin-style meters aren't used on fiberglass boats, but rather the ones that you just place on the boat's surface. Moisture meters alone aren't a guarantee, but they are a great tool and I think it's worth considering buying one when boat shopping.
 
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