The wood is like a wick and the wood will suck the water up like a spong all the way to the front of the boat if it stays wet long enough. This what my boat is made out of now no wood in the transom or stringers
http://transomrepair.com/zk/

Not to worry, the stringers will be looked at real close when I cut them back to get the new wood in. May even drill a couple holes for a look, down low & somewhat forward. That rotten wood in that pic was actually the middle layer of plywood. The outer sheet was good for the most part throughout. The ends of the stringers were isolated from the transom by the FG matting and had good wood when I cut through them to separate from the transom.

All wood is now out and down to the filler. The wood was really black were the problems originated. There were very small pin head size bugs crawling in the wet wood.
Would have been nice if Baja would have used as much resin to seal all the exposed wood, as they did in staples to fasten the 3 sheets together!

I think that filler your talking about may just be light weight expandable foam? I would try to find and use something else to level out the surface if the foam is in bad condition.

Also, when you go to insert the new piece of wood in, how are you bonding one to the other? (Resin? or a higher grade marine adhesive). What else you may want to try is w/e surfaces your not glassing, paint with DTM paint..(Direct to metal, bonds like crazy). Especially the edges of the plywood, it will suck that paint in and seal it off from any water going threw. (Thats how the rot really starts, is from the play wood edges, and the drain holes..ive just learned to seal them with an oil based paint)

Going to bond the wood together with resin and a layer of 1708 mat. The mat might be overkill, but I have alot of it. The ends and all holes will be sealed with resin and maybe even a layer of matting. I was thinking of removing the filler and using the 1708 biax to buildup the transom to the approx thickness it is now with the filler by layering it on, then doing a finish sand to level it out.
How many layers of FG can be put on in at 1 time? Have read where no more than 3 at a time, and then read where it was ok to do 6 as long as it's a wet on wet layup. The issue being the heat buildup during the cure. I recall reading too much heat with more than 3 layers can cause issues?
Also, is it best to apply the 6" tape around the edges after the wood is in, then extend the 1st biax matt 2-3" past the tape, then extend the 2nd biax matt 2-3" past the the 1st? Or do I run the out 1st biax 8" out onto the sides/bottom, 2nd layer 2" shorter, then finish it off with the 6" tape which would be just a 3"/side coverage? Seen/ told it could be done either way, just curious which way to run the overlaps is best/strongest.
Thanks for the input!

Sorry to chime in to your thread so late but I have been out of town. Regalman has a thread covering most of the install of this same project..."what-wood-use-do-i-really-need-marine-grade" it is a few threads down in this same form.

I replaced my complete transom and sections of stringers too. I think the filler you are talking about is kind of a pinkish color (or at least mine was). I think they call it cabasall or something like that (not sure how to spell it). You are correct, it is a filler but I am not 100% sure why its there but it appears to be used in all transom applications. I did a complete transom replacement and Glass Dave told me to leave it on and DO NOT take it off. It looks like you have some gauges in it (and I did to from trying to remove the stupid plywood). Glass Dave told me just to fill in the gauges and voids with new filler and a puddy knife or a yellow plastic body filler spreader deal. Then once you have it all filled in, scuff the whole transom up with a 2x4 and a piece of sandpaper and you are ready for the install!

If I am not mistaking, the cabasal stuff comes in a bucket and is kind of fluffy. You mix the fluffy powder with resin and it works like "bondo" or automotive body filler but is different I guess? Glass Dave told me to call "US Composites" to order the cabasal, resin and glass. They are good people to work with and I recommend them as well.

As for the stringers Glass Dave told me to come back off of the transom a couple inched and cut them back on a 45 degree angle. I posted a couple pics on the other thread if you want to see them) Once I did this I found that part of my stringers were rotten to. This is why the hammer tapping method doesn’t work / or didn’t for me :( The stringers sounded good and looked good but ends of them where they connect to the transom were rotten as a result to the water leaking down the transom and then worked into the ends of the stringers. Big bummer but not that big of deal in the big picture.

I would strongly recommend looking at the thread I referenced above (what wood use do I really need marine grade). It should help a bunch. Please let me know if I an be of any more help, but go with whatever Glass Dave says, he knows his stuff!! I would have been lost with out him. On a scale of 1 to 10, Glass Dave is about a 15++

Brian

That ngle that Dave told you to cut on the stringers is called a scarf joint .

Yeah, I have that thread memorized and resort to it several times a day. Even have it bookmarked for faster access. ;)

I talked with Dave at length last week. Just keep on running into more questions.
I'm ordering from US also. Going with the Vinylester resin. Figure if the boat was originally done in poly, this will be a step up w/o going too crazy with epoxy.

Did the filler seem to accept the resin and make for a strong bond? That's what I'm concerned about. Not really knowing what it is. Did you use a thickened mixture with your 1st piece of mat/wood, or just mat with with straight resin? The filler issue is giving me the most fits. I'd prefer to remove it and build up the transom with more glass since it looks like there is just 2, MAYBE 3 layers. Either way, it's paper thin. But the filler varies quite abit in thickness, from nothing to 3/16" in spots. Surprising, the outside is really straight. The gouges don't worry me as they are an easy fill. Which way did you do the overlap? Less overlap with each following piece or more overlapping?



Thanks

Unless you went crazy with hammers and chisels the filler wont let loose and you will get a good bond. If it's not smooth enough just sand it or grind it. You can blast it with an air nozzle to see if any of it flakes off. On a transom that's going to be over 2" thick you can use polyester resin. Epoxy might be a better choice if you have not done a few transoms, because you can give yourself hours of working time with epoxy compared to 45 minutes with polyester. I've run a kerosine heater in my shop off and on for 12 years and it's never been a problem. If you get Kerosine on your hands that's a problem so always use some disposable gloves when handling the fuel.


www.bowkersfiberglass.com

How thick will this yield?

Currently the transom is 1/8".
Adding 3 layers of 1708 to build it up and make it flat.
1 layer 1 1/2oz matting
3/4" wood,
1 1/2 oz matt
3/4" wood,
Finished off with 2 layers of 1708.

I'm shooting for right at 2" to match original thickness. Just not sure how thick the 1708 and 1 1/2oz mat add up to. Will 5 layers of 1708 and the 2 layers of 1 1/2 oz yield at least 3/8"?
I'm thinking I'm going to come up short and may need to substitute 1 of the 3/4" for 2 layers of 1/2"

Thanks

that sounds like a good layup and should get you pretty close to desired thickness. The coupler does have the ability to compensate for the slight difference its the excessive deviations in or out that you want to avoid.