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K. Kergan
K. Kergan, Marine Mechanic
Category: Boat
Satisfied Customers: 1030
Experience:  24 yrs exp. Inboard/Outboard mechanic Mercury/ Mercruiser, Volvo Penta and OMC, Johnson/Evin.
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Fiberglass Work I'm redoing my transom on a 1989 Donzi and I

Customer Question

Fiberglass WorkI'm redoing my transom on a 1989 Donzi and I need some help related to repairing it. The questions I have are related to the process required to re-fiberglass the transom with coosa board. I have purchased the coosa board and now have a local business that can supply the fiberglass. I have watched several YouTube videos related to fiber glassing but still have uncertainty and questions.
I plan on putting two pieces of 3/4" coosa board in the transom. I'm assuming the fiberglass process should be something like this.
1. Place the first piece of coosa in the transom.
2. Use something called peanut butter to adhere the coosa to the gelcoat of the boat.
3. Place a piece of Biaxial fiberglass cloth over the coosa and apply the resin until the cloth is fully saturated.
4. Place the second piece of coosa into the transom.
5. Put more peanut butter around the coosa until it adheres to the first layer of Biaxial.
6. Place the second piece of Biaxial over the coosa and apply resin until the cloth is fully saturated.
7. Last apply another layer of Gelcoat or apply Woven.
I need advice from a professional on how to do this.
Submitted: 5 months ago.
Category: Boat
Expert:  K. Kergan replied 5 months ago.

Hi, my name is Kerry

Clean out all of the rotten wood down to the hull.

Make sure the area is clean and dry, you can use acetone to remove any traces of wax or oil.

Wet the area down with resin and apply a layer of fibreglass matt and saturate it with resin.

Apply the first layer of coosa board and press it firmly in place until the resin kicks.

Trim any sharp edges of matt that may be sticking out and fill any voids with fibreglass filler, the type with fibres in it.

Apply another layer of matt and the second coosa board.

After the second layer hardens, trim and fill again, then cover the whole works with another layer of matt overlapping onto the surrounding area.

I found this on a web site;

You do not have to encapsulate a Coosa panel in fiber-glass and resin, as would typically be the case with plywood, to prevent water absorption; however, glassing the panel adds stiffness and strength. Therefore, if the original equipment manufacturer encapsulated their plywood panel for structural reasons, you will want to do the same or find another method to use to compensate for the loss of external strength derived from the resin and fiberglass skins.

I'll be happy to answer any more questions you have about this process.

Expert:  K. Kergan replied 5 months ago.

I remove all of the wood down to the fibreglass of the transom using a small grinder with a flexible sanding disc.

Expert:  K. Kergan replied 5 months ago.

You will need to remove any wires that go through the transom and clean the bilge.

Grind the gel-coat off the bilge floor at the back and wash with acetone.

Overlap your layers of glass matt onto the hull at the bottom, each one an inch or two farther than the last.

Cover everything with gel-coat to seal it, bare glass is not totally impervious to water.

Expert:  K. Kergan replied 5 months ago.

I would normally go all the way across the transom with new wood, or in this case, coosa board.

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