Bad Transom?

[qboat]

I got Runt a few weeks ago, and this weekend put trim tabs on her. The interior of the transom was pretty soft down at the bottom where the tabs go. Where I installed the top bracket, above the waterline, it was downright punky. I could use some advice. The motor mount bolts are not pulled into the gel coat, so I must have relatively good wood there. The transom passes the "leg" test--that is, there is no flexing when I tilt it up and drape my 220 lbs across the lower unit. So I think it is ok--that is, safe--to use at present. Has anyone opened up a transom on these boats? She is a 1993 22' CDory. Is the transom core balsa, or marine ply, or a combination? Thoughts on preserving the useful life of the transom? I would be grateful for any insights or advice. Happy New Year! Sam

[thataway]

What I have seen happen in a boat where the transom is suspect, is that with a strike of the lower unit, the transom cracks--and then you are really in a compromised position. The "bounce on he lower unit" is one test. If there is known degradation of the transom core (which will be plywood--may or may not be marine grade--it might be AB or Even AC, exterior grade.) The other risk is that if the splash well glass is not right against the transom glass (void between hull and deck), that the splash well glass will crack and indent from the bolt / washer pressure on upper bolts. Some boats come from the factory or dealer with an aluminum bar across this area. That spreads out the load more. The top of the transom is where the hull to deck joint is. This should be well glassed together, but that is not always the case (under the black plastic strip, or in some brands an aluminum strip.

One other factor is where the boat was/is kept. This may be in the boat's past 30 years, when it was exposed to freeze thaw cycles. The expansion and contraction begins delimitation.

From what you describe, I would pull the motor, check the bolt holes. If there is rot there (which I suspect there will be); spend a week or so in the evenings/winter and put a new core--properly sealed off with thickened epoxy--in place now, rather than loosing time next "season". I know that you can do some winter boating in your area, but it is far from ideal, even with a pilot house boat. (Spent 2 years in the Richmond, Va area, and a winter in Norfolk aboard my 62' boat.)

[clayhubler]

qboat, sorry to learn about Runt.

Hammerhead is a 2003, and the transom was 1" balsa. Your boat may be different, as Dr. Bob described.



If you have wet core in the transom, you will likely have wet core in the hull also. There was no barrier keeping water from migrating either direction in my boat. If you want, you can look at my photo album here: http://www.c-brats.com/modules.php?set_albumName=Core-rot-repair&op=modload&name=gallery&file=index&include=view_album.php&page=4

I would describe the rot in my boat as pretty bad. However, there were no soft spots and no delamination anywhere on the hull or transom. I feel the boat would have been 'safe' to use for quite a long time still. I had a vacation planned before I tore into the boat, and was hard pressed to get it finished in time for the trip. If you choose to move forward with the repairs, make certain you have plenty of time and a good place to do the work. Indoors and heated, preferably. You may find that you are able to dry some of the core instead of replace. The benefit is that it is less work, but it does take a lot of time and still a lot of effort.

Get one of these:


Use it to assess the potential damage. Keep in mind that the surface needs to be completely dry and also don't use near metal fasteners. This will give you relative readings. Find some dry core to use as a baseline. The dash/ helm station is also cored, at least on my boat, and was dry, so I used that.

Good luck. I feel that many c-dories have these issues. That being said, they are so well built that many owners never have problems.

[qboat]

Thanks, Dr. Bob and Clay. What a job on Hammerhead! Makes me afraid of what I am getting into. I am not sure I want to know what is under the deck, which feels 100% solid. I was hoping to address the transom from the outside, to avoid removing tanks and other gear. I would love to get this job done over the winter but it is going to have to wait for better weather--I don't have a place to work on her inside, just a tarp shelter open on the sides. I am sure I will have a number of questions going forward, but Bob is right, I need to address this. The glass layup on the transom is thicker than I would have thought--that may be largely what is masking the problem. I really hope this can be rectified by going in through the outer skin.

[thataway]

Remember that on the inner part of the transom is two emoluments. One is the hull, the other is the deck, which includes the splash well.

I prefer that any repairs to the transom be done with epoxy or vinyl ester resin. Both of these have primary adhesion better than polyester. Plywood would be my material of choice, with saturation with epoxy, and every hole drilled out and then epoxy plug put in place to prevent any future migration of water.

I have done two transoms from the outside, but it is necessary to pull the tanks etc usually. That is not that big a job, and when put back in, any floor of the cockpit is addressed.

[qboat]

I would use epoxy--I have pretty extensive experience with glass over ply construction and it is easy, if not cheap, to use. The well/transom joint seems tight, so hopefully the outside approach is OK. I am hoping to avoid Clay's Homeric exercise. Given that the core of the transom of the bottom was soft but not running wet, I can hope that any water intrusion below the deck is limited. Won't know till I get in there, I geuss! The deck seems largely unmoleseted, unlike the transom, which has had a number of holes drilled in it in the past thirty years.

[thataway]

The issue with epoxy is the gel coat as a finish. Although gel coat can be put over epoxy, either after fully cured, cleaned and dry, often folks use a tie coat, for the gelcoat or paint.

Although I owned a 1993, 22, I never looked at the hull to deck joint over the transom. I know that in some of the early 2000 boats there was a lack of glass fiber, just mostly filler. when we did the top of the 2003 25, we added more glass to this area, and also addd several layers of 1708 with epoxy to the under side of the splash well. The way that boat was built, the plywood did not go all of the way across the transom, and I felt that some of the load transmission was taken by the splash well--thus I beefed it up.

[qboat]

Bob, that is interesting. what was inside the hull on the sides of the transom, if the ply did not run all the way across? Balsa? Foam? I am wondering if that is what I have hit with the trim tab installation.

[thataway]

[qboat]

On Runt, the screws at the bottom of the transom for the tabs went into something woody--maybe balsa, maybe soft ply, but the top brackets of the tab went into a void. As I pushed down into it with a coathanger, it felt like there was foam below the hole, not rotten ply. I am wondering if the wood in the transom ended short of the sides as it did in the 25' boat you describe. Before I pull the motor and start cutting skin, I think I should put in some test holes closer to the motor mounts, which feel solid. Thanks, Dr. Bob. Sam

[thataway]

Unless someone put foam in the core on a rebuild there should not be foam in the 1993 C Dory22 transom... (that I know of). On the plywood insert transom (a Grady White 20' Adventurer) the plywood was just like toothpicks.

[qboat]

Thanks for all the help. I will report beck this spring once I have the weather to open the transom, via a new thread, if there is any interest in what I find. Sam