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  1. #1
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    Default Curved Transom Rebuild

    I decided that the Glasspar Tacoma I just bought is a keeper, the transom was redone but only the lower part. Who ever did the floor only replaced the transom part way up, about mid way on the motor. The tie down loops and upper corners were only supported with two small blocks of wood and not connected to the main transom wood.
    The biggest concern is that this is a very curved transom, the rear of the boat curves about 4 to 5 inches outward from a straight line. It looks like the original transom was made or 4 layers of 3/8" plywood, most of the original wood is still good, but there's a rotted section down the left rear side, between the corner of the splashwell and the motor. It looks like the aluminum corner trim sort of funnels the water that way, so after the new transom, I'll have to seal that area up as well.
    The original transom is made up a many pieces of 3/8" plywood, not just four sheets, they overlap in various sized sections.

    Has anyone ever had to do a transom with such a curve?
    I considered Seacast, but the inner skin is only a single layer of glass, and I would have to do as much work to form up a temporary inner liner just to make the pour as I would have to do simply making a new wood transom.

    Is it acceptable to make the transom out of several vertical strips as they have done?
    I think I would use glass inbetween the layers, the original doesn't even look bonded in any way. The marina that did the floor cut away only the outer skin of the lower transom and attached a single new sheet of 3/8" ply across the bottom below the splashwell. The floor repair looks great, but it looks like they never bothered to go any higher to check the transom.
    The transom didn't show any signs of flex, but I noticed the rotted wood when I was tightening a few loose screws in the aluminum cap.

    I think I will most likely have to cut away even some of the new floor, but I hate to destroy all that nice work. The floor is made of 3/4" thick marine ply and from what I can see through the bilge hole with a bore scope, it looks like they epoxied or sprayed the entire underside as well. The top surface of the floor is finished with a heavy gelcoat and painted with a non skid paint. It looks better than factory. The transom is skinned on the inside with only one layer of woven glass and resin, it's pretty thin. I pulled out most of the soft wood, and the inner skin is like a sheet of paper. I did consider building up the inner skin to make it self supporting and then using the Seacast, but I figured that since the transom is so thin and curved, it would be nearly impossible to get all the rotted wood out. The curve is such that I would have trouble getting the chainsaw in and out without hitting or cutting through either side.
    The outer glass is thin too, the outer hull is only 1/8" thick. I will have to add lots of support braces when doing this one.

  2. #2
    Honorary Moderator Emeritus tashasdaddy's Avatar
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    Default Re: Curved Transom Rebuild

    suggestion cut some horizonal 3/4 ply braces with the curve in it them, with some interlocking vertical braces. and glass them in.
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  3. #3
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    Default Re: Curved Transom Rebuild

    The problem I am going to run into is that the inner wall of the transom is no thicker than a piece of paper, it's got no strength at all. The outer layer is only an 1/8" thick as well. I am afraid that if I try to do a Seacast pour, the walls will just bulge.
    The problem I will have doing it with wood will be keeping the curve, the outer wall is so thin that even 14" plywood will tend to try to straighten it or push out the sides. I started pulling out the rest of the wood that's not rotted and its all made out of strips with each layer run in a different direction. They cut the plywood into 3" x 20" strips and glued them all together forming the curve. It's bonded well to the thin inner skin, but not at all to the outer wall. The outer wall looks like it may have been gel coated on both sides when new? (As if the wood was added after this came out of the mold? The 'wing' areas are separate on each side, they are not part of the lower transom and are separately installed. They are cut to fit the shape but not very close. They do not go to the top of the hull at the sides.
    Whoever did the floor, cut back the lower inside transom skin, or peeled it upwards and cut away an 8" lower strip of the second inner most layer of the transom wood, then a 4' wide strip of the lower innermost layer, then replaced that with two fitted strips of new 3/8" plywood and re glassed it all back in.
    The floor in this sits only about 2" above the lowest part of the bilge and this has no access to the bilge area other than a 3/4" drain hole at the rear. The floor is super solid and don't flex with even me on it, so I don't want to disturb all that work if I don't have to. The way I see it, the lower bilge area is so small, that even if it were to fill up with water at sea, its such a small area that it cant sink the boat. I would guess that at best the underfloor area might be able to hold about 8 or 10 gallons of water tops, probably way less. I have a bore scope for engine work that I used to look around through the bilge hole and it all looks clean and shiny and freshly glassed. I did notice that there are no gussets or direct connection from the transom to the floor, the "stringers" are only 2" tall or less, and look more like shims to level the floor than true stringers. I get the impression that they were trying to make an airtight compartment for flotation? The rear drain is the only way in. I've seen other older boats like this as well, but most were either foam filled or had the floor set higher. The floor follows only the flatter part of the hull, it ends at the dash and steps up to a shelf like area under the forward deck. All floor and under dash surfaces are heavily glassed and gel coated. The floor is probably the heaviest part of the hull, the outer skin is super thin.
    I am planning on adding a pair of diagonal gussets down to the floor at each side of the motor mounting area below the splashwell for added support too, I think it will make a huge difference in the overall strength of this boat. The splash well in this is only screwed into the tow side deck extensions, and secured to the top of the transom with a few screws, it doesn't give much added strength at all.

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