The boat featured in this rebuild is a 1984 Grady White. The boats owner is a local customer who purchased all his materials through our store and followed all of our technical advice, making this rebuild a great basis for the tutorial. The entire rebuild was documented by the owner of e-boat inc. at our message board. (This is a link to the rebuild thread). We provide technical help for all sorts of repair/rebuild projects through our forum. To receive the technical support for your project, please register and read this thread detailing what information we need to be able to help you. All materials in this rebuild were purchased through boatbuildercentral.com
Step 1: Prep Work:
In our example boat, you can see the transom core is soaked and it has lost nearly all of its stiffness.
Step 2: Gain access to the transom
The next step in the rebuild is the removal of the old plywood core and inside fiberglass transom skin. You will need access to the entire transom plus at least 12" up the side and bottom of the boat. Depending on the boat's construction, you may be able to remove the deck cap, or you may need to make a cut through the deck and sole. If you post pictures at our forum we can advise you on the best places to make these cuts to avoid time consuming fairing work (hiding seams).
Step 3: Removal of old plywood core
You can see in the pictures below that the liner is cut away and the old plywood has been removed. Any bonding putty in the corners should be ground out. The new core needs to be bonded directly to the old outside skin. NOTE: We recommend the last 8"-10" of the stringers be completely removed, in this case the stringer was not cut back far enough to be ideal.
Once the old plywood and putty are removed, make a template of the transom using cardboard or cheap plywood (or anything else handy). You will use this template to cut your transom core and also to draw/cut the wide fiberglass pieces that will make up the new inside transom skin.
Step 4: Install new plywood core
Plywood selection is another topic covered in other tutorials, please read this for more information
The new core can be either made in one piece, then bonded into the hull, or you may laminate one layer at a time into the hull. It is generally easier to laminate the core outside the boat and bond it into the hull once, but on very large transoms this may not be possible due to weight and difficultly in handling.
To laminate two pieces of plywood, first coat the faces of the plywood that will be glued together with un-thickened (neat) epoxy resin. This is a thin coat of epoxy, just enough to let the face of the wood soak up a little epoxy. While this epoxy is wet, mix a batch of epoxy glue. Epoxy glue is made from same epoxy with wood flour mixed in to reach a "ketchup" consistency . Using a notched spreader, apply even amounts of epoxy glue to each plywood face. Now clamp the two layers together using weights, clamps, or dry wall screws (temporary, removed after glue cures). Do not apply too much pressure! Epoxy is gap filling and extremely strong, you want the epoxy to remain between the plywood layers. Once the epoxy begins to squeeze out the sides evenly it is time to stop the clamping pressure
We have videos and tutorials on mixing epoxy and making epoxy glue here.
In the example boat the customer decided to laminate each layer one by one into the hull. The method is the same as if the laminations were made outside the boat: apply epoxy, then glue, then clamp.
In picture 1 you can see the first layer clamped into place (plywood is Meranti BS1088).
After 3 layers total, we have the total core thickness epoxied into place. (picture 2)
Step 5: Fill Gaps
Below is the core with a fillet of epoxy putty all around (Note: the stringer should have been cut off at least 10" forward of the transom).
Step 6: Tab transom core to hull
Here is the core tabbed into the hull (again, the stringer should not have been tabbed back in yet as in this picture).
Step 7: Laminate
A little more about Biaxial Cloth: Biaxial Cloth is available in several weights. In general the lighter the cloth the easier it will be to wet out and work with, but this will also mean many more layers to build up a desired thickness. The heaviest biaxial cloth we normally recommend for amateurs is 1708. 1708 consists of 17 oz of biaxial cloth with an 8 oz matt stitched to the back side for a total of 25 oz. It is important to only use biaxial/matt which is epoxy compatible. Not all cloths are epoxy compatible! Read more on wetting out 1708 if this is your first experience. Here are some important tutorials to understand
From our howto section: Howtos
Below is a picture of the Grady White transom with the new biaxial glass inside skin. Notice the overlaps up the side and bottom, also wrapped over the top of the motor cut out.
Step 8: Finishing up
The boat is now ready to be put back together. While the structural aspects of the rebuild are the same from boat to boat: marine plywood, epoxy, tabbing, cloth, etc..., each boat design will be a little different in how it should be taken apart and put back together. You do not necessary have to follow the same procedure as the example in this tutorial. In the case of our example boat, the owner simply epoxied into place the cut out portion of his motor well. Butt blocks epoxied to the underside of the parts were used to make a lip for gluing the two edges of fiberglass. Using epoxy fairing compound the joint was then faired out smooth.