Wet Transom Too

[Rich]

Time to tear up the Transom. I've decided to tackle it from the outside. I'm going to follow Dunk's procedure. Here is what he has to say:
(got this off of www.wmi.org)

The easiest way to do it is to cut the outer glass skin off the transom and save it. With a pencil mark a line around the perimeter of the transom about 1 1/2"-2" from inside the edge. Do this just around the bottom and sides, the top comes off all the way up. If the wood is wet or rotted you won't have any trouble getting the glass skin off. Dig out all the wood. Now you are left with and empty transom with 2" deep border around the bottom and sides. Doing this retains the strenght around the outer edge and you don't have to worry about tieing the transom to the rest of the boat.
I don't recommend building the transom off the boat because if the transom has any curve to it you'll never bend it to match. Clean the inner transom with a grinder to expose fresh clean glass and coat it with epoxy resin. I like to use 1/4" luan plywood then a layer of roven woven(RW) between each layer of ply. 1/4" luan plywood will just about soak through with epoxy, it's bone dry when you buy it. Cut as many layers as you'll need to fit the transom pocket before you start. Leave the section where the engine bolts higher than it needs to be, you cut that to the right height at the end of the job. You'll also need the layers of RW cut to size. 4 layers of each will give you about 1 3/8" thickness, figure what you need from that. Start with RW against the inner transom, then ply then RW then ply. You want to soak all the plywood a couple times before you start laying it up. Dry unsoaked plywood will pull the resin out of the RW before it sets up. If you are cutting the plywood to fit tight at the sides you may want to bed it later by layer with a putty mix of epoxy and cabosil. This will fill the side pockets full. The bottom will fill with excess runoff resin. Once you have as many layers as you need drill holes and bolt the whole transom together though the inner existing transom. 1/4-20 nuts and bolts with washers. You don't need to over tightem then either, that would just squeeze the epoxy out from between the layers. Most plywood you buy has a curve to it. Cut your transom sections so when put in place the ends curve toward the bow of the boat. This way most of the bolting you do is in the center on the transom. You should be using the slowest setting epoxy you can find. It soaks into the wood better and gives you plenty of working time. Once it starts to set pull the bolts and fill the holes with epoxy/cabosil putty. Don't over build the transom so you can't fit the outter skin back on flush. Fill all corner and edge voids with the putty. Grind the inside of it for a good bite. Mix up more cabosil and epoxy putty and layer it accross the entire transom and put the skin back on. This is where you have to figure out how to hold it in place. I've use 2 x 3's across the transom with ropes tied to the ends up thru the bow eye and back the other side. 2 x2's or 2 x 3's will bend around the transom allot easier than 2 x 4's. After that fill the crack around the planel as flush as you can and walk away from it and let it set as one big lump. After that it's not a bad idea to run some figerglass tape around that seam with epoxy resin. Sand and paint to match. Cut your transom then cap it with a couple layers of glass tape and epoxy resin.

Keep you posted.

[ May 29, 2002, 03:20 PM: Message edited by: Rich ]

[timd]

Rich, check out my pictures under the 20 footers. I did the whole transom over a weeks vacation. Hardest part is all the sanding and fairing after the glass work is finished. Check out raka.com for your epoxy and glass cloth, I was very happy with their products. I bought a six gallon kit, and have about 1.5 gallons left.

[Reel Smoker]

Rich or anyone redoin the transom. When Mike at Wildfire Marine replaced my transom he suggested on running the drain holes on the 2 rear compartments out the sides (solid glass) instead of the original way out the rear,or thru the transom. He mentioned these was one of the reasons the transoms would rot. Just a suggestion.RS.

[white hawk]

Rich, I'm sorry to have to disagree with your N.J. advisor but I think he's wrong on two points. I believe the transom rebuild is better approached from the inside. It is a little harder to access from the inside but the completed job is invisible, and with a lot less grinding work. The old inside layer can be cut away with a 4" grinder and diamond blade. It fits right up against the hull sides for a clean cut. Also the clamping process is made easier by making cauls to fit the outside curvature of the transom and through bolting to pads on the inside which are insulated from the wetted structure with plastic wrap. The laminations are done much the same except that concurrent with general practice the resin is allowed to drain off, owing to the generally accepted fact that resin contributes no strength to the transom, only the wetted glass laminations do that. This is why boat-builders use the vacuum bagging process, to remove excess resin (weight) and leave only the wetted glass. Through hull penetrations are now made using the plug technique, preventing any future water migration into the wood laminations. Briefly this technique is accomplished by using a hole saw with a very long pilot bit. After marking the finished transom on the outside for through-hull locations, pilot holes are drilled from the outside. From the inside the hole saw pilot is inserted into these holes and the saw (rule of thumb size of saw is 4 times that of pilot) is advanced as far as the outside skin. Everything is removed as far as the skin, but the skin is left undisturbed. You now have a small hole on the outside and a large hole on the inside. The large hole is filled with FG putty (cabosil,glass fiber,etc.)a piece of plastic wrap and thin ply patch screwed to the transom keep it in place till it cures. When cured patch is removed and hole is re-drilled from outside. Water will not migrate through this plug into wood. Insofar as removing inner well is concerned, something to think about is that those inner wells also served to stiffen the transom, acting as a defacto knee brace to dampen transom flex. If your power selection will be within original design parameters you should have no problems, but if you are considering bumping those numbers up you may want to re-think that step.

[Rich]

Too Late to change plans now....

I thought long and hard about this, and decided it was too much work to tackle from the inside. The deck and the well areas are in great shape and to rip them out would be a pain and a shame. I feel confident that the method I chose will work. Actually, I'm almost done. Everything goes back together this weekend. I have been working on this Transom (on the weekends) for over a month now. I have all sorts of pictures of my progress which I will post on seacraft.snetsol.com after I'm done.

Thanks for the suggestion,

Rich

[hermco]

I agree that the transom replacement should be done from the "outside".I am currently doing a 20' transom rebuild and will post pics of the job.Going in to the job from the "inside " is creating a lot of work for no gain.The idea is to get the desired result with the least ammount of damage to the existing structural glasswork and rely on the strength of the original material that got the boat thru this many years.
d.h.

[white hawk]

Did not realize you had begun work already. Also did not realize you were leaving inside undisturbed. You made the right choice insofar as which side to work from, however the other points are worth consideration. A lot of resin goop serves no purpose running out all over your work, and the F.G. plug penetration procedure stands on its own merit.

[Rich]

I took some time tonight to throw up some more pictures of the beast. You can see them at http://seacraft.snetsol.com I'm starting to put the transom back together this weekend. I'll follow up with more pictures as I make my way thruogh.

[ July 12, 2002, 12:07 AM: Message edited by: Rich ]

[Briguy]

Rich, Great pictures! Good luck with the final product. Just a quick question for the board. Why would we still use plywood when so many new non wood products exist. My local fiberglass supply shop has many different foam/honeycomb transom materials such as divinycell or corecell. Why not use these and save hundred pounds and never have to worry about the rot. Any thoughts?

[John R]

I haven't done it yet, but this boards running theme and that of other boards is that a properly prepared and soaked layers of wood in the transom are stronger and will last just as long as their synthetic counterparts. Wood is good [img]images/icons/grin.gif[/img]