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TOPIC: Coosa for transoms?

Coosa for transoms? 1 week 5 days ago #141153

What are the opinions of using Coosa board in transom replacement?
I watched the video link:
www.bing.com/videos/search?q=coosa+board&view=detail&mid=3FFD595C80AAFD8F2EEB3FFD595C80AAFD8F2EEB&FORM=VIRE

I really like what I see, but my question is: Is compression of the Coosa dependent on the fiberglass outer surfaces strength?
I put some plain Coosa in a vise and it compressed about 1/3 thickness.
Would I want to do anything special to the areas that an outboard motor is bolted through the transom to keep the Coosa from compressing?
doc

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Coosa for transoms? 1 week 4 days ago #141156

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This doesn’t directly address your question, but may be helpful. I am very interested in your questions. Depending on how compressive it might be, could lead me to think about fabricating a bent metal 3 side transom saver to cover inside , top, and outside. I liked your video and had seen parts of it, but had not seen the whole thing before this one you listed. I have to look at a different video I saw quite some time ago to answer one question that arose for me when watching. I will reply again when I find that information.

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Coosa for transoms? 1 week 4 days ago #141157

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Here is one of the other videos that helps explain my question regarding the video in your link. I saw where they decided to use epoxy resin instead of polyester resin because they wanted more adhesive strength. I am ok with that thinking. However, they show their layup starting with Chopped Strand Mat CSM because they wanted more tooth to bite to... likely more tooth than just a 24 to 50 grit grinding sandpaper wheel would provide on the original fiberglass skin. The problem I was remembering was that it has been shown on many videos that CSM has. Styrene binder that will Chemically dissolve when using polyester resin, but will NOT dissolve when using epoxy resin. When they then layer with 1708, it uses thread to bind the glass and is supposed to work well with epoxy resin. I had seen a different ship shape TV video that showed them only using 1708 against original transom skin and transom board putting the CSM side against transom skin using the same wet epoxy resin on skin, on board to smooth side of 1708... then thickened epoxy over wet epoxy on skin and then install transom board that already had the 1708 on it with the CSM side facing transom skin and clamp. I will try to find that video as well. I am truly not a fiberglass expert nor do I run a repair shop. I have just been trying to learn everything I can over the last couple of years so that I can do my best the first time around. I really would also like to learn from the experts and please correct me if I am wrong or have misinterpreted things. I am a high horse power guy and want the strongest transoms I can make. That big boat appeared to have twin outboards. Don’t know their size, but if it were my boat, I would be laminating another layer and adding some knees. I see big rigs taking a pounding on big water and would want piece of mind. In that first video, I wondered why they wouldn’t have wanted to use a straight 2x4 on edge on the inside top for all clamps to ensure a straight edge rather than risk a bow with the weight of the clamps hanging and trying to pull it out. I could see it on an arched G3, but wondered about a straight transom.

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Coosa for transoms? 1 week 4 days ago #141160

When I did the Lake n Sea Transom I used Seacast and was told to build a inner and outer "skin" of 1708 using 6 layers for each, 1/4" + in & 1/4"+ out then filled with composite. In video 1, Andy uses 3 layers of 1708 on each side of the 1/2" Coosa adding 1/4" to the thickness. So perhaps using Coosa for a 1-1/2" composite transom; 4 layers 1708 - 1/2" coosa - 4 layers 1708 - 1/2" coosa - 4 layers 1708 (12 layers 1708 = 1/2" + 1/2" Coosa + 1/2" Coosa) and use the epoxy. 1 outer layer to have extended 1708 to assist in tabbing in to the hull. Just a thought.....

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