It just keeps going...

[Project_Mayhem]

I discovered that the wood in the middle of the transom is soaked. My boat is the inboard model and construction might be different than the outboard model. Anyways, I started cutting away the inner skin and rotten wood today. I discovered that there is some thin wood on the starboard side of the transom. Does anyone know if this wood extends all the way to the starboard corner of the hull?

I'm considering redoing the area around the gudgeon in heavy fiberglass without wood because it's constantly getting dipped under water. Can anyone find any reason not to?

I peeled away the wood layer by layer until I found some solid wood that was a normal color. Can I build on top of this or should I go to bare fiberglass? Does anyone know how thick the outer fiberglass skin is on the O'Days?

 

[Davidasailor26]

I'm considering redoing the area around the gudgeon in heavy fiberglass without wood because it's constantly getting dipped under water. Can anyone find any reason not to?

Rebuilding the full thickness with fiberglass will probably be more time consuming and much heavier than making a new sandwich. You could use something like Coosa that has more water resistance than wood. If you properly overdrill and epoxy fill all penetrations there should be limited chance for water to enter anyway. Boatworks Today has been doing a transom rebuild for several episodes. Probably more in-depth than yours but it might give some good ideas. The first episode where he starts digging into it is

 

[jssailem]

Water intrusion is a pain. Having started the project it is always a question where do I stop.

Does anyone know if this wood extends all the way to the starboard corner of the hull?

It is likely that I construction in 1978 was a plywood transom as an inner frame wrapped by fiberglass on out and inside. The plywood would connect to the hull on each side if you have found dry solid wood, that is sufficient destruction an removal.

Can anyone find any reason not to?

Yes, @Davidasailor26 stated it well “weight”. The combination of wood and fiberglass is lighter than solid fiberglass.

found some solid wood that was a normal color. Can I build on top of this or should I go to bare fiberglass? Does anyone know howt thick the outer fiberglass skin is on the O'Days?

If you have solid dry plywood then yes rebuild on top of it. Use a moisture meter to test the moisture content. It should be less than 8%.

You need to identify where/how the water soaked into the transom. Likely screw holes or a serious crack. Repair that along with the rebuild.

Coosa is expensive but a good material to use on a transom core. I’d follow the Boatworks Today repair process for transom repair. Andy produced a solid repair to his boat. Note he is probably much more than you need. He plans to hang big outboards on his transom. I suspect you do not.

 

[Ward H]

On my O’day 25 I could see the thickness outline of the areas with plywood.
I used some G10 board when adding strength for a ladder. Might be heavier than ply but the area your rebuilding is not that big, unless it is wider than on a model with OB.

 

[Project_Mayhem]

You need to identify where/how the water soaked into the transom. Likely screw holes or a serious crack. Repair that along with the rebuild.

Gudgeon had zero sealant on the three screw holes. It's really low on the transom so it sees a lot of water contact

On my O’day 25 I could see the thickness outline of the areas with plywood.
I used some G10 board when adding strength for a ladder. Might be heavier than ply but the area your rebuilding is not that big, unless it is wider than on a model with OB.

You are correct, the area in the middle of the transom has a 12" wide strip of 1/2 plywood. I was curious how far the thinner wood goes as I found some rotten at the edge of the 1/2" ply.
Three layers of 1708 builds up to 1/2" pretty quick and I have a large roll of it already. Seems like it could be more water resistant and stronger. It might actually be faster to lay it up than to get a piece of wood to fit in there perfectly

 

[jssailem]

Gudgeon

That would have been my assumption. I am trying not to ASS-U-ME too much this year.

 

[Davidasailor26]

Three layers of 1708 builds up to 1/2" pretty quick and I have a large roll of it already. Seems like it could be more water resistant and stronger. It might actually be faster to lay it up than to get a piece of wood to fit in there perfectly

17oz cloth with mat is 0.042” per layer according to Determining Laminate Thickness. That would put you in for 12 layers to get 1/2”. By that point it’d probably be pretty bullet proof, but also pretty heavy and expensive (in time and materials). I don’t know the break-even point in strength of 1/2” plywood sandwich vs solid laminate.

 

[Project_Mayhem]

I finished tearing this apart over the weekend. It turns out that O'Day used 1/4" plywood and a 1/4" of thickened epoxy followed by some fiberglass cloth.
I always use fast hardener but this is a lot of surface to cover with thickened epoxy and will probably kick before I'm done. Here are my options:

• Slow hardener - I just looked up the price of slow hardener and a pump and it's more expensive than thixo/six10. I'm thinking I could build it up and bond it all in one step. Probably pretty messy but not the end of the world
• Thixo/six10 - Sure sounds convenient. Is it thick enough?
• Fast Hardener - Build up 1/4" of thickened epoxy section by section and then bond the wood with epoxy and 404/406. This sounds slow, messy and painful

Was the filler I found used in such a thick manner to avoid having to conform the plywood to the slight curve of the transom, was it structural or both?

On a side note, I found what appears to be the outline of some plywood on the starboard side which is where most outboards are mounted on O'Day 25's. Perhaps the inboard and outboard transoms were built in the same manner. If memory serves me correctly, my port side does not have any wood built into it

 

[Ward H]

On a side note, I found what appears to be the outline of some plywood on the starboard side which is where most outboards are mounted on O'Day 25's. Perhaps the inboard and outboard transoms were built in the same manner. If memory serves me correctly, my port side does not have any wood built into it

Interesting. Sounds probable. I know I've seen outboards on both sides. Mine had the OB on the port side. Plywood reinforced transom on that side and the wedge for the OB mount, which looked like it was part of the molded hull. Maybe they added that on?

As for thickened epoxy to fill the gap of the hull curve, I used fiberglass kitty hair, short strands of fiberglass, to thicken the epoxy and 105/205 epoxy. I'd probably use the G Flex epoxy if I was doing a similar project again.
Consider cutting or sand the inside corners of the plywood so there is not a hard edge.

 

[Davidasailor26]

I finished tearing this apart over the weekend. It turns out that O'Day used 1/4" plywood and a 1/4" of thickened epoxy followed by some fiberglass cloth.

Are you sure it was thickened epoxy and not some kind of thickened polyester? Most production boat builders avoid epoxy due to cost and because it’s more work to add gelcoat or more layers of laminate. Guess it doesn’t make much difference going forward with the repair though; you can fix it up with epoxy in any case.

I always use fast hardener but this is a lot of surface to cover with thickened epoxy and will probably kick before I'm done. Here are my options:

• Slow hardener - I just looked up the price of slow hardener and a pump and it's more expensive than thixo/six10. I'm thinking I could build it up and bond it all in one step. Probably pretty messy but not the end of the world
• Thixo/six10 - Sure sounds convenient. Is it thick enough?
• Fast Hardener - Build up 1/4" of thickened epoxy section by section and then bond the wood with epoxy and 404/406. This sounds slow, messy and painful

Incidentally BoatWorks Today just did a video this weekend of tips for getting the right epoxy thickness and working time.

 

[jssailem]

For Boatworks Today. Just watched that video. He provides insight into working with thickened epoxy.

 

[Project_Mayhem]

I've worked with using thickened epoxy many times. What technique would you use in this application? I will be using 1/2" marine plywood since I have it on hand already

• Slow hardener - I just looked up the price of slow hardener and a pump and it's more expensive than thixo/six10. I'm thinking I could build it up and bond it all in one step. Probably pretty messy but not the end of the world
• Thixo/six10 - Sure sounds convenient. Is it thick enough?
• Fast Hardener - Build up 1/4" of thickened epoxy section by section and then bond the wood with epoxy and 404/406. This sounds slow, messy and painful

 

[Ward H]

I used Six10 to fill old holes under the rub rail. It would sag a bit out of the hole so I put a piece of tape over it.
I wouldn't think it would be thick enough for your purpose, as a bit of a gap filler.

I have thickened Six10 further when I have a mixing nozzle on a tube and a project requires it to be thicker to prevent sagging.

 

[Project_Mayhem]

I used Six10 to fill old holes under the rub rail. It would sag a bit out of the hole so I put a piece of tape over it.
I wouldn't think it would be thick enough for your purpose, as a bit of a gap filler.

I have thickened Six10 further when I have a mixing nozzle on a tube and a project requires it to be thicker to prevent sagging.

I was pretty skeptical when I read that it's thin enough to wet out fabric. Thanks for confirming!

I ended up buying some slow hardener. There's a ridge of filler on either side of the repair area. I plan on grinding that down to 1/4" and using that as a guide for filler depth. I will also put a few small pieces of 1/4" wood on the plywood so I don't push it too far into the uncured filler

 

[Project_Mayhem]

This project is coming along nicely. I've gone over to the yard a few times to remove all the filler, cut and fit the plywood, apply filler and glass over the new plywood. I did make one mistake - I forgot to coat the end grain before installing it. So, I cut the bottom of the plywood at an angle to gain access and then put some cloth over it. The top and sides of the plywood had a generous amount of filler all around.

I also cut the hole for the cockpit drain. I was very happy to see that there were no voids in the filler.

 

[racenmotorsports]

Was that just reopening the cockpit drain or putting in a new one?

 

[Project_Mayhem]

Was that just reopening the cockpit drain or putting in a new one?

I destroyed the thru hull fitting on the transom because of the amount of sealant used at the factory. It wasn't worth the amount of work it would take to save a $10 part. The replacement part I ordered was "Five Oceans White Straight Thru-Hull Fitting Connection for Hose, 1-1/2 inches, FO-1867". You may have to bore out the hole a little larger and cut off the nipple. The factory one has the nipple cut off at a 45 degree angle so you can take the hose on/off