Original transom material

[Bushwacker]

Check out Okume plywood . . . more/thinner plies, but much stronger and lighter than conventional plywood! Not sure about cost but Skip's using it on his 21 and I was impressed with how light it is. If well sealed with epoxy, it would be a big improvement over conventional plywood!

[flyingfrizzle]

Most people just use Douglas Fir marine grade plywood for transoms and bulk heads. A lot of people use the Fir in transoms due to lower cost and it is stiffer. Douglas fir is stiffer than meranti and meranti is stiffer than okoume. (modulus of elasticity: fir = 1,560,000 to 1,950,000, meranti = 1,500,000 to 1,630,000, okoume = 1,140,000) Okoume and Meranti can be a better choice for marine applications but at a higher cost. Each has its place. On the down side Okoume is less resistant to rot than fir or meranti. Meranti is less resistant to rot than fir so the Fir would be the best far as rot resistance. Okoume and Meranti have a much better finish that wont check with less flaws. Doing a transom the ply wont be seen so it's not a big deal but places that are seen Okoume or Meranti is much easier to do a finish quality surface on. My Master Angler hull has a Okoume transom in it (3 layers of aquateck) and it was not sealed up well at the top. Two years in the weather it was rotted away near completely. Seems like the Fir transom weather the water much better but if it correctly sealed up with epoxy it dosent matter and you should be fine no matter what you use. I have done transoms with ac grade exterior pine and had them last but they were sealed 100%.

[shine]

On my 23 I used fir for the transom and OKoume on some bulk heads, and meranti for the sole. At the time I had access to a warehouse full of marine plywood and I chose what I like best for each application. Okoume and Meranti finish very well with just a light cloth, fir needs more glass to keep it from printing through (or checking). I prefer fir for a transom, it has great properties, it get covered with plenty of glass (no concern with printing), and it happens to be about half the cost of Okoume.

[afterhours]

Thanks Shine and Frizzle for the input. I think I'll go with Fir ply when I get around to redoing the transom this winter.

[FAS]

shine is spot on,go marine ply for strength,figure how much glass to use to reinforce the transom to be tough as you need it to be.Frizzle has the correct spects.
make it at least 2.25" thick,you will be happy....

[linesider36]

FAS Knows transoms!