Mako 254 rebuild

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
Seabird254
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Re: Mako 254 rebuild

Post by Seabird254 » Fri Dec 06, 2019 9:38 pm

http://www.polyumac.com/upload/files/Ga ... 6+2019.pdf
http://www.coosacomposites.com/images/T ... a_0412.pdf


I hope I can post those here. I have only found one source of technical data for marine ply that somewhat compares the same units. From what I have read(probably wrong) marine ply is stronger than coosa, and coosa is a bit stronger than gator. Im no engineer, anyone on here make sense of the gator board specs? I assume a few extra layers of 1708 would be the only difference?



fallguy1000
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Re: Mako 254 rebuild

Post by fallguy1000 » Fri Dec 06, 2019 10:13 pm

You would need 26 pound density material.
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Fuzz
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Re: Mako 254 rebuild

Post by Fuzz » Sat Dec 07, 2019 12:16 am

I have never used either product so not much help. From all that I have read those that use coosa go with the 26 pound product and make it as thick as a plywood core would be. I know for myself I would go heavy on the glass if in doubt and good bracing. But then I am prone to over building :roll:

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Re: Mako 254 rebuild

Post by DAYTRIP » Sat Dec 07, 2019 9:32 pm

Plywood is going to be much stronger and require far less glass to develop the equivalent strength. That said it is twice as heavy but that might be 30 pounds in a transom. My general experience with polyumac is that it’s properties are not as good as the “main stream” products. Particularly the foam. That said I have built many things using their products including my current hardtop and seating.

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Re: Mako 254 rebuild

Post by DAYTRIP » Sat Dec 07, 2019 9:40 pm

So looking at the properties, the compressive strength of the gator board is 800 psi and coosa is 960-1100. That is the meadure of crushing strength. The coosa will take more to compress. The flexure strength of gator is 2900 psi and the coosa is 5200 psi. This is how strong it is in bending. Again coosa is much better. The gator will work but for equal loading you would need more skins of glass.
The shear strength is likewise significantly less. This is my main dislike about the polyumac. The glass can pull the polyumac apart almost with about half the force that it would take with coosa.

Fuzz
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Re: Mako 254 rebuild

Post by Fuzz » Sat Dec 07, 2019 11:22 pm

That is some great info to know. Thanks DayTrip.

fallguy1000
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Re: Mako 254 rebuild

Post by fallguy1000 » Sat Dec 07, 2019 11:33 pm

DAYTRIP wrote:
Sat Dec 07, 2019 9:40 pm
So looking at the properties, the compressive strength of the gator board is 800 psi and coosa is 960-1100. That is the meadure of crushing strength. The coosa will take more to compress. The flexure strength of gator is 2900 psi and the coosa is 5200 psi. This is how strong it is in bending. Again coosa is much better. The gator will work but for equal loading you would need more skins of glass.
The shear strength is likewise significantly less. This is my main dislike about the polyumac. The glass can pull the polyumac apart almost with about half the force that it would take with coosa.
I used corelite at 847 and 1800 and lotsa glass. Looks like flex is the big weakness for me. Fortunately, my transom is 3 feet wide only..
My boat build is here -------->

viewtopic.php?f=12&t=62495

boguesounder
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Re: Mako 254 rebuild

Post by boguesounder » Fri Dec 13, 2019 10:25 pm

No input on the gatorboard but wanted to tip my hat to a cool hull. Worthy project! Congrats.

Seabird254
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Re: Mako 254 rebuild

Post by Seabird254 » Sat Dec 21, 2019 5:41 pm

Thanks daytrip. Im leaning towards plywood mostly because Im more comfortable working with it and it is much easier to source. Not to mention the cost. If I like the boat enough to keep it 30 years ill pay my grandkids to rebuild it again :D

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Re: Mako 254 rebuild

Post by DAYTRIP » Sat Dec 21, 2019 9:38 pm

If you use epoxy and treat the penetrations right it will last forever.

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