1979 O'Day 23 transom reinforcement repair questions

[Boom Zine]

Hi all,
I'm new to the forum, somewhat new to sailing, and very new to owning a sailboat. I'm a public school teacher and worked for months in a side gig as handyman to save for my dream of owning a sailboat. My wife and I found a somewhat local 1979 O'Day 23 in July this year, within my budget, and pulled the trigger. I gathered that owning a sailboat would be a lot of work, but I didn't think it would be to this extent so soon. We were at least able to get one sail in before the discovery of the problem!

I've been digging through old threads, doing my research on a repair project needed for a rotted transom. The situation seems to be somewhat common: water intrusion through motor mount/gudgeon bolt holes leading to rot of wooden transom reinforcement/coring that was glassed in.

I have the general idea on what needs to be done to fix it: squeeze myself through lazarette hatch and lay below cockpit, cut/grind/remove old material, sand down surface, shape three 1/4" ply layers to be epoxied in (with 1" oversized holes drilled and filled with thickened epoxy for new gudgeon/motor mount bolts), and finished with a couple layers of epoxy to seal it in.

I understand it's a crazy messy job and will require me to completely cover myself and use a good respirator...vacuuming often.

My questions:
- if any, how many additional layers of 1/4" plywood are needed for the "king plank"...the central, thicker reinforcement that the gudgeons will mount to? Is anything additional needed for this area?

- beyond the final coats of epoxy to seal everything in, should I glass over the entire surface? Glass just the perimeter? If any fiberglass is needed, what thickness should I use? Chopped strand seems to be the way to go if necessary.

Any other advice, or even any other pictures showing end results of similar projects would be greatly appreciated. I found a great deal of inspiration from this thread and this thread, but unfortunately didn't see any pics of the finished projects.

I really appreciate any help. I need all the inspiration I can get! Thank you.

 

[Hydro Therapy]

Hello Boom Zine and congrats on your purchase. That’s quite the job your taking on. I really can’t provide advise. It looks like you have done a lot of research on the subject. If I read your post correctly it looks like your rebuilding from the inside. If that’s the case would it be easier to cut out the wood and build it up with several layers of glass and cloth?

 

[Boom Zine]

Hello Boom Zine and congrats on your purchase. That’s quite the job your taking on. I really can’t provide advise. It looks like you have done a lot of research on the subject. If I read your post correctly it looks like your rebuilding from the inside. If that’s the case would it be easier to cut out the wood and build it up with several layers of glass and cloth?

I will be rebuilding from inside the lazarette/below the cockpit. Do you mean building up the area with fiberglass instead of wood? I'm curious if this is an option, and if so will it provide the proper amount of reinforcement while allowing enough flex?

 

[JRT]

I thought the accepted repair process was to use several thin sheets of plywood to epoxy to the outside fiberglass transom. As I recall from reading others have a solid plan to hold each of these new plywood pieces in and solidly to the curve of the transom. Each sheet will be coated in epoxy to bond to each other, Fiberglass is used to seal it all after. It will be a fair amount of epoxy so make sure to have very good ventilation and proper personnel protection equipment.

Are you replacing the whole transom wood or just around the gudgeons? Make sure to check the wood around the motor mount holes also.

I'd stick with just replacing what was there, it held up this long so just rebuilding it back should be good.

 

[Boom Zine]

I thought the accepted repair process was to use several thin sheets of plywood to epoxy to the outside fiberglass transom. As I recall from reading others have a solid plan to hold each of these new plywood pieces in and solidly to the curve of the transom. Each sheet will be coated in epoxy to bond to each other, Fiberglass is used to seal it all after. It will be a fair amount of epoxy so make sure to have very good ventilation and proper personnel protection equipment.

Are you replacing the whole transom wood or just around the gudgeons? Make sure to check the wood around the motor mount holes also.

I'd stick with just replacing what was there, it held up this long so just rebuilding it back should be good.

Thanks. Yeah, I'll be rebuilding the wood "core" on the inner side of the transom...all of it, including where the gudgeons mount as well as the motor mount. You mentioned glassing it all in afterwards. Sounds good. Any recommendations for thickness of fiberglass I should use?

 

[JRT]

I really don't have a recommendation. If I had this problem on my O'Day 25 I would use the removed glass as my guide for type and thickness and keep everything the same, depth wise, as designed. On my 25, my transom is very solid and the glass looks like layer cloth, not chopped. That is what I would do but others might try chopped, but I like sticking with the way it was originally built.

Also are you really sure the entire transom has to be replaced? This is a big job and nasty area to work in that. I'd check the integrity of the wood by drilling pilot holes in a grid, say every 6" to start, to see if the damage is every where or local and can be cut out and replaced in smaller areas. This approach is easier and also means you are less likely to have void issues trying to curve the plywood and bond it all back in.

 

[LeslieTroyer]

Boat works today shows repair of a rotten transom -power boat. He went for an outside repair. https://www.boatworkstoday.com/

Les

 

[Scott On Eagles Wings]

Before you go chopping your boat apart, consider CPES. I have used this product all over the place and makes for a permanent fix cheep and easy. http://www.smithandcompany.org/CPES/Cart/index.html They even have formula's for damp wood as well. I used it 13 years ago when I bought the boat and it is still holding firm. I highly recommend this product. Go to their web site to educate yourself and then you can purchase it from many sources.

 

[JRT]

Before you go chopping your boat apart, consider CPES. I have used this product all over the place and makes for a permanent fix cheep and easy. http://www.smithandcompany.org/CPES/Cart/index.html They even have formula's for damp wood as well. I used it 13 years ago when I bought the boat and it is still holding firm. I highly recommend this product. Go to their web site to educate yourself and then you can purchase it from many sources.

Actually this makes a lot of sense, I used a similar product, Git-Rot, but the wood had to be dry. It has held up very well and the dry product is hard and solid for a year plus now.

 

[Ritdog]

Hi--am curious as to how you are making out. You are doing what I did with my 25, and it seems that you read both of my posts on the subject.....your king plank has the same problem as the motor mount panel , I did mine separately just because of the bending of the wood.

Reference : " beyond the final coats of epoxy to seal everything in, should I glass over the entire surface? Glass just the perimeter? If any fiberglass is needed, what thickness should I use? Chopped strand seems to be the way to go if necessary."

Remember that epoxy and resin do NOT get along- the resin will never dry over epoxy. I learned that the hard way..... If you are using epoxy for everything, then you will have to use cloth for the final cover of the wood as chopped mat has a binder in it that does not get along with epoxy. I finished up my panels and then just put two coats of resin right on the wood for sealer. The three sets of panels will also shift a little as you install them, so watch for that.
I put the first one in, as I said, having drilled holes here and there through the transom, using sheet rock screws to suck the first panel up against the inside (made up thickened resin with microfibers and smeared that all over first ) , let that harden, then did the last two wetted out , mat, panel, wetted, mat, panel, resin coat. Finish the outside with thickened resin for the holes, then gelcoated those spots.

If you'd like to talk to me about this send me a text at two zero seven three oh three five three nine three, with YOUR number, and I will call you back! ...good luck anyway!

 

[mwpaul]

Boom Zine and I have been PMing each other, but considering we're in the same boat literally and figuratively I thought I would post here. I also bought a 1979 O'day 23 this past year. She had a loose lower gudgeon and when I checked it out the core was also rotten. I started tearing it out this weekend. My main question is... What do I do with the fiberglass rail (unsure of the name) running aft along the bottom of the boat? It attaches to the transom, but the wooden core was apart of that.
My plan is to replace the core with marine grade ply 1/4" same as what was in there. There appears to be slots cut to allow for easier contouring of the ply to the curvature of the transom (pictured below).
Remove all rot down to the fiberglass hull, Sand and wipe clean, epoxy the new wood core to the fiberglass, lay fiberglass on the other side of the wooden core, gelcoat. reinstall all hardware with stainless backing plates

 

[Ritdog]

That's interesting. My 25 has something similar but is just an L-shaped stiffener which does not go back all the way to the transom.
It would seem to me that you could cut that close to the transom, replace the wood, then tab it back in with some biax or a few layers of cloth . (Remember, you can't use epoxy with mat).

 

[ebsail]

I also had some rot in the transom of my Oday 25 which I discoverd when adding a new motor bracket. Noticed the flexing when pulling on the outboard bracket. Not wanting to go through all the work that's being discussed here, I drilled many, many 3/8" holes from the inside of the transom without going through the outside glass of the transom. A flat tipped bit helps here (Forstner?)/ Then I inserted 3/8" hardwood dowel, with the tips dipped in thickened epoxy, in all the holes with the tips dipped in thickend epoxy. The tips will epoxy to the outer skin and some will be scraped off and glue to the inner skin. The transom is now solid as a rock with a new bracket mounted and tested by hanging a 200 pound person on it. Zero flex in the transom.

 

[CharlieSea]

Good advice on the epoxy resin, nothing sticks to it and it's expensive and nasty. Don't use it. Regular ortho or iso polyester resin is fine; iso is better. No silver bullet. Dig out what's there with a sharp chisel, grinder, carbide tip or whatever and replace it. Don't imagine it's more than a couple of mats, plywood, one woven roving and a couple of mats to finish. Mat is like the peanut butter that holds the slices of bread together. So use one or two layers to stick the first ply and in between plys if you use two. You might have to cut reliefs in the ply wood to get it to conform to the transom shape; find a way to hold it in place against the transom while the resin goes off; think under catalyze. Doesn't seem like more than 1/2" in total of ply is needed. If you know where the hardware goes then make the hole in the ply a lot bigger and fill with chopped strand putty before the woven and the final mats. You can also use foam core or balsa if you wish but make sure to reinforce where the hardware goes with solid glass or aluminum glassed in. To attach to the original boat grind out about a couple/three inches. That rail is just the original laminations. As suggested, grind out fill with chopped strand putty or what ever and then grind and tab over with the woven and mats. What you are trying to do is separate the outer and inner skins like an I-beam. Oh, you will itch.

 

[Boom Zine]

Just wanted to say thanks to everyone for the replies and help. I had some tragedies hit my family in November, and obviously a lot of things went on pause.

Thanks to all of the great info on this message board and an old copy of "This Old Boat", I have a solid plan for the transom repair, and have started some work on getting it ready. However, I found significant core damage in the deck below the mast tabernacle, and repairing that has taken priority...but progress has been good and I'm feeling confident, so it's all good!

Thanks again!