Crossposted on facebook
Time to cut the DS2 transom! (it is rotted sufficiently to the point where I do not feel comfortable mounting a ladder or a motor) I am excited to learn and need a list of materials before I begin.
I plan to do a write up on this project for other people to use at the end.
Gel coat part number? Quantity?
Paint part number? Quantity?
1708 fiberglass source? Quantity?
Resin part number? Quantity?
Hardener part number? Quantity?
Deck to hull adhesive part number? Quantity?
Transom wood/coosa board size? How to curve/bend (or shape) transom board?
Where to cut the deck?
I’m going to do this from the inside. The question is, where do I cut? I was planning on stepping back about a foot and cutting a straight line all the way across the deck from gunwale to gunwale. Strength is a concern after repair so where to cut is a concern. 
Update 09/08/2020
St Rudy suggested cutting as far aft as possible while leaving enough room to “tab-in” support from underneath. Plan is to cut just forward of the scupper drain in the lowest part of the pan.
Strength after repair?
Everything I hear says fiberglass work can end up being stronger than the original.… If it’s done correctly. My plan is to create tabs on a bench and let them cure. The cured tabs could be adhered to the underside of the untouched deck after sufficient prep. After they cure in place, multiple tabs could support the piece that was cut out before. Prep of the underside of the saved piece along the deck edge could create semi-interlocking tabs. (See pics on Facebook)
Update 09/08/2020
St Rudy alluded to this method in his suggestions
Transom board
This is an obstacle but not a dealbreaker. My effort is to reuse 99% of the original fiberglass with surgical cuts to preserve as much as possible. The transom board, however, is likely a total loss and in need of 100% replacement. While I have not found any instructional videos, I understand that there are ways to bend pressure treated plywood from Lowe’s. I have 5/8” thick marine grade plywood already with sufficient size to cut the shape of the transom twice or maybe thrice. I know it is probably easier to layer up several thinner portions of plywood. However, each layer would cost another $10-$15 in material. Stacking that much material would get very expensive very quickly. There is a solution that I just don’t know about for this.
Update 09/08/2020
St Rudy said The transom was kerfed somewhere between 10 and 12 times; vertically only. Fiberglassed over up against transom before deck/pan lowered into place.
Deck to hull
While the fiberglass patch should reconnect the farthest aft section of the deck (that was cut out) back to the original deck, cap will need to be glued back to the hull for the entire length of the transom plus about 1 foot wrapping around the back edges towards the bow. What type of adhesive should be used, what is its part number and how much should I get?
Gelcoat
Once I knock the high points off and get it smooth, I assume gelcoat comes next. What specific brand, quantity and part number should I expect to get?
Paint
Matching sun faded paint is nearly an impossibility. I have the yellow and brown sail pattern and most of the original marking still on it. I might only lose about a foot of pinstriping on the back. It will need paint to cover the patch line. What should I be looking for? What is the specific part number and quantity I should get?
What have I missed?
The fix a flat stop leak method
As we are all familiar with both of these products, they are a filthy and awful stopgap measures that only creates problems later. at the same time, there is a market for those products because sometimes it is appropriate to use them… albeit rarely. Seacast is a pour in transom repair product. A bunch of chopped up fiberglass mixed in a bucket of resin and Hardner is poured into the transom after removing the cap of the transom and hogging out all of the rotted wood. Only the cap comes off of the back of the transom. This means that the deck is not cut but only the cap on the back. The obvious problem is the question of what happens at the bottom. Does this product run back underneath the deck? Does it plug up holes that aren’t supposed to be plugged up? Has anybody here used this product before? It seems like it would cost about $500 for the sea cast repair and shooting from the hip, it looks like it’s going to be about $300 to cut the deck off, replace the entire transom board, and then re-fiberglass, fill, sand, gelcoat, and paint everything.
Update 09/08/2020
St Rudy did not immediately balk at this idea. He actually had good suggestions in how to make it work. We agreed that 6”-7” inspection ports as far aft as possible on the vertical face under the seat would allow access to work. A shop vac could be used with a copper pipe to remove old core. Then, build up a dam of bondo to catch the seacast where it would run out under the seat. The end result would be a transom core that follows the profile of the transom interior. The cap could be reused with VERY little fiberglass work being done.
If you made it this far, thanks in advance for all of your help and thank you for reading to the end!