CD-10 - Transom Repair - Any advise?

[mashenden]

Does anyone have advise from having completed a successful transom repair on a CD-10?

On mine, the outer skin has delaminated from the board that is sandwiched between the outside skin and cockpit skin. This let rainwater get inside the transom, which in turn means the wood inside the transom got soft.

I plan to:

• 1) Remove the outer skin using a grinding wheel for a decent edge (straight or tapered - not sure yet).
  2) Replace any soft wood with epoxy coated good wood that will also be epoxied into place to get good adherence to the inside (cockpit) skin.
  3) Dry anything that does not need to be replaced.
  4) Apply a couple more coats of epoxy to seal it all.
  5) Lastly, reapply the outside skin (or put in new glass).

My main area of concern is how to tie the new edges of the skin or glass to the boat in order to maintain structural integrity. Overlapping a layer of glass seems likely to result in an unsightly bulge. Alternately sanding it flush will eliminate the intent of providing strength.

Also what type of resin do people use - polyester vs epoxy? Mainly looking for compatibility concerns to the existing materials rather than strength comparisons.

If anyone has input, I would love to hear it (other than hire a professional or read a book ).

[Oswego John]

Matt,

I've had pretty good luck using polyester resin when when working with fiberglass cloth.

I generally use epoxy to attach one thing to another or for tabbing.

Good luck with your project,
O J

[mashenden]

Thank you, John.

In doing some research it appears that epoxy resin sticks to anything but polyester resin will not stick to existing epoxy based materials. While most production boats are polyester based, repairs could be either. Does anyone know if CD-10s (assuming no epoxy repairs) are polyester based?

Assuming CD-10s are polyester based with no epoxy repairs in its past, this is not a deciding factor - I could use either.

Also it appears that the 2 part top paint that I am likely to use such as Imron, Awlgrip or Perfection will stick to polyester or epoxy based materials, so this is not a deciding factor.

While I hoped to avoid characteristical comparisons, epoxy resin as compared to polyester resin is stronger, has a tighter molecular structure (read: mo' watertight), and has greater adherence, meaning it will act better as a glue.

It appears to all come down to $$$ (isn't that always the case ). Epoxy resin is 3 - 5 times more expensive than polyester resin.

I suppose as a tender it will be in the water a fair amount so the extra $$$ will be worth the piece of mind knowing it will not have to be re-repaired - If only I knew the cheaper approach would outlast me then I would be good with it

[Stan W.]

Your basic plan is sound. I offer the following suggestions:

1. Use epoxy. Except for its reputed poor ability to take a polyester gelcoat finish (which does not apply to you) epoxy is better than polyester in every way.

2. Just replace the whole transom core. It's not that big on a CD 10.

3. If at all possible, attack the core by removing the inner skin and leave the outer skin intact.

The link below may give you some ideas or at least some reaffirmation.

http://boatbuildercentral.com/howto/tra ... /index.php

[Steve Laume]

I'll put a vote in for epoxy.

I use West System epoxy hardeners and fillers. They have a nice free users guide that gives a good description of their products and their uses.

Get a set of mini pumps for measuring and epoxy is pretty fool proof. I would use it for the lack of nasty smell if for no other reason.

You must have one of the CD-10s with the full liner. My very early one has a completely exposed mahogany board in the transom, Steve.

[Duncan]

This doesn't apply to my CD - 10, thank goodness, but we did redo the transoms on several of our (beat-up) club tenders last year, and learned a few things.

From that experience, I would say that your #2 item (replacing the wood) may be the toughest part.

One issue we had was that the wood was bad right out to the edges, and down to the bottom. Since we left a bit of the fiberglass skin to tab onto, we couldn't cut all the wood out, and ended up "chiselling out" about an inch of it all around. This was a pain. It also left us guesstimating on cutting replacement plywood without an exact template.

Lesson learned: If the wood is bad, cut right to the edges, then tab the replacement in with new fiberglass cloth around the edges

The other main thing was trying to get the old skin to adhere to the new plywood, without a lot of voids. Since these are workboats, we ended up just putting a lot of screws in to pull the skin down onto the plywood. This was ugly but effective, but I wouldn't recommend you mess up your nice CD 10 that way.

Lessons learned: a) Use balsa coring. It's flexible, so it will bend to attach to the old skin. b) Use new fiberglass cloth on the other side, instead of trying to re-use the old skin that you cut out. It will make a complete bond without voids, and you won't have to fuss with clamps or gravity trying to get the old skin to stick to the new coring.

One final comment - use epoxy, since it makes a much better repair, and this is not a repair you'll want to re-do.

[mashenden]

Also thank you, Stan W, Steve Laume, and Duncan. The advise on this board is second to none.

I believe epoxy will be the ticket... I was leaning in that direction.

Some tidbits I really appreciated:

The Grady White transom repair link - Not only was this link very relevant to what I am trying to do, but coincidentally I am constantly looking on Craigslist for a 22' 1984ish Grady White deal (I swing both ways - sail and power, but more toward sail). Perhaps if I follow this I'll be able to put a 225 on the CD-10 .

Also the idea of attacking from the inside was priceless. It never occurred to me but is clearly a better idea. Just because the outer skin detached does not mean it has to be the one to cut. I need to go look to see if cosmetically I would be able to avoid a repaint by doing it this way and accepting some smaller imperfections.

Again - thank you all.

[Michael Ellis]

By all means, replace all the wood. For one, it isn't that large of amount and any residual dry/wet rot is going to continue. Second, since you are already seeing delamination, getting the old core out won't be that hard. And finally, don't even consider removing the outside skin. Using a Dremel type high speed tool cut the inside skin and peel back. Chisel out the old wood and clean the inside surface of the outside skin with acetone. Lay in a couple of layers of roving and saturate with West System epoxy. Press the new wood core into place (you should see epoxy oozing out) and brace into place until the epoxy is cured. Sand the edges where the inside skin was removed and use boat cloth to fabricate a new inside skin. After the epoxy on the inside repair is cured sand out edges and try to match the paint/gelcoat of the inside of the boat. It will probably be easier to paint the whole inside instead of getting a good match. Also, any polyurethane, whether one part or two part, will absorb water if left immersed for enough time. I have tried Perfection and got blisters. I talked to an Awlgrip factory rep and he said it would also. Another reason for attacking the problem from the inside instead of the outside. I have done this repair on Minto's with good results and it is easier than you would think.

[mashenden]

Thank you, Michael Ellis. That confirms everything that I have come to believe to be the right approach. I am definitely going to go from the inside rather than the outside.

I may try to cut the skin using a grinder and after replacing the core, reapply the old skin with epoxy (and filler to hopefully address adhesion and void issues) and clamps. I know Duncan advised to not do this but it seems soooo tempting to try.

[mashenden]

In regards to approaching this from the inside, I took a look at the boat and have a few more questions to ask of anyone that has done this already.

As Steve Laume deduced, mine does have the full liner, which includes a rather notable enclosed space under the stern seat.

I am leaning toward not cutting the entire seat out as that means cutting 2.5' horizontally, which seems extreme. Instead cutting across about 8" in from the stern. In choosing that surgical incision, most of the scar would be hidden under the wood seat planks once done, except for the 8" or so vertical incisions in each corner. Thoughts?

What can I expect to find inside the cavity under the stern seat? Presumably foam. Will there be any problems in not cutting out the whole thing?

[sharkbait]

I have cut out the bad transom wood before using a router but it wasn't on a CD10. I set the depth to miss the outer skin then started at the center of the bad wood. Working my way out until I found good wood. Once I found good wood I trued up the void, cut a replacement board, bedded it in Epoxy thickened to almost peanut butter and clamped it in place. After the epoxy cured I applied new layers of fiberglass to the inner surface to create a new inner skin.

It didn't take long with the router and it left a very smooth surface to work with in applying the new wood.

[Steve Laume]

In regards to approaching this from the inside, I took a look at the boat and have a few more questions to ask of anyone that has done this already.

What can I expect to find inside the cavity under the stern seat? Presumably foam. Will there be any problems in not cutting out the whole thing?

Judging from a couple of CD-14s with built in flotation tanks, I would bet all you are going to find in there is smelly air and some gunk.

I cut an inspection port into the CD-14 to be able to clean things out and for some very minor storage. It is interesting to note that if the edges are not all sealed you slowly lose your flotation.

The older CD-10 has styrene foam under the seats. I replaced all of that with better fitting Dow, Blue Board.

You boat probably has more flotation but the foam in the old boats can't leak out, Steve.

[mashenden]

Judging from a couple of CD-14s with built in flotation tanks, I would bet all you are going to find in there is smelly air and some gunk.

I cut an inspection port into the CD-14 to be able to clean things out and for some very minor storage. It is interesting to note that if the edges are not all sealed you slowly lose your flotation.

The older CD-10 has styrene foam under the seats. I replaced all of that with better fitting Dow, Blue Board.

You boat probably has more flotation but the foam in the old boats can't leak out, Steve.

Ahhh, I am used to smelly air

Would the gaps that you reference in some CDs be where the seats meet the inside of the hull or where the liner comes up to the gunwale as in the case of a full liner?

I think I'll drill a hole or two to determine if it is an empty cavity or filled with foam.

If the latter I was worried about how easy it would be to separate 8" of seat and a little bit of transom skin from the foam that was presumably injected in and stuck to all it could as it expanded into place when built.

If not the latter, I will definitely be adding some foam (I have some left over 2 part foam mix) and some storage.

[mashenden]

The cavity under the stern seat on mine is very much empty (no foam), with the exception of a tiny bit of water. I did not need to drill holes to check the "foam vs no foam" issue because the holes for the seat screws go all the way through (hence the water). 3" bronze screws seem a bit overkill presumably not the original design.

So lessons learned: 1) no foam in the stern seat of CD-10s with a full liner and 2) it is a good idea to caulk the screwholes when installing the seat wood to stop water from getting into the floatation cavity.

While I have the cavity open, I probably will put some wood/epoxy strips under the screwholes as backing so water is less likely to get in.

I may fill the cavity with foam too - Any pros/cons that I am missing?

[Numbah134]

It's one I've been thinking about with the CD14 front/rear seats (which are air chambers with 1-inch or so holes for plugs to make them "sealed", so it's easy enough to poke around in there and find no foam).

Foam weighs more than air, so technically floatation is reduced - for ideal conditions. As Steve points out, that depends on everything staying tight - not the best assumption for "emergency" buoyancy, IMHO. If you got hit in the bow or stern you'd almost certainly lose all the air in there just when you'd really like to float...so I'm leaning towards foam + storage space (via adding some of those large watertight inspection ports). I'm debating polyurethane spray foam .vs. waterproof rigid styrene (blue or pink board - extruded rather than expanded). I think the latter may be less prone to waterlogging over time. Waterlogging (if it happens) and complicating future maintenance (what you were afraid of with finding foam already in place) would be two items on the negative side of the balance sheet. I guess boat weight is also increased.

On the other hand, the stock setup on the CD14's seems to invite gunk, and not provide a good way to clean it out (the plug holes are not low enough for all the water to drain out, nor big enough to clean effectively.)

A possible modification that would reduce floatation considerably (unless done as an add-on/expansion of the center seat) would be to use foam + fiberglass to make a cooler in the seat, where the foam serves as both floatation and insulation.