20 foot seacraft deck

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
Fuzz
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Re: 20 foot seacraft deck

Post by Fuzz » Fri Jun 01, 2018 9:41 pm

I have heard folks say short first. Their reason is if they were a bonding issue with the earlier layer the next one would help keep it in place. With that said I am not sure it makes all that big of difference what way you go. Others may feel different and have good reasons for it.



TomW1
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Re: 20 foot seacraft deck

Post by TomW1 » Sat Jun 02, 2018 1:40 pm

For structural reasons always start with short. Then each succeeding layer will have some of the old beam to hold on to as well as the new fiberglass.

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Re: 20 foot seacraft deck

Post by fallguy1000 » Fri Jun 08, 2018 4:55 am

The theory on overlaps is largely about subsequent sanding.

If you are glassing an exterior transom; you glass the longest join first, and follow with shorter. That way, when fairing, you would struggle to sand through the most beneficial layer. And if you look at a diagram of layers; you see how this make sense. If you sand through the long layer laid last; it is weakest on the strongest join. But if you sand layers laid long first; you sand only the edges of each layer in fairing.

The times this would vary is if you are not sanding, but if sanding would affect the longest join; the long join need be protected.

I was told by a professional boat builder and I expect there are some rules on it somewhere; although rules dna for most of us; only good building practice.

I doubt you'll be sanding those stringer areas; so you'd be able to go the other way.

Another reason to consider long first is if you think you'll have air in the layup short first, but for 1708; air ought not be a consideration. For a heavier fabric like a 36 oz; it might...
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Re: 20 foot seacraft deck

Post by fallguy1000 » Fri Jun 08, 2018 5:03 am

Intuitively, what Tom said makes a lot of sense, but the builder told me that the stacked laminates in a join are considered as a single unit and the strength is not from each next layer holding a bit more, but laminate thickness. I don't want to argue with Tom on this subject. I had a real hard time with what the builder told me, but it was reinforced by a few other professionals later.

In Mertens foam sandwich handbook; for stringers; he shows long join first.
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Re: 20 foot seacraft deck

Post by topwater » Fri Jun 08, 2018 7:15 am

They also stagger the layers so you don't get point loading at the end of the stack. It spreads the load out .
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Re: 20 foot seacraft deck

Post by lelandtampa » Fri Jun 08, 2018 8:53 am

Thanks guys for the Intel. Have a bunch of glass to cut and layout first.

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Re: 20 foot seacraft deck

Post by lelandtampa » Fri Jun 08, 2018 8:55 am

Probably going to go long tab first so I dont get an airbubble at the edges of the lower layers.

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Re: 20 foot seacraft deck

Post by fallguy1000 » Sat Jun 09, 2018 8:34 am

topwater wrote:
Fri Jun 08, 2018 7:15 am
They also stagger the layers so you don't get point loading at the end of the stack. It spreads the load out .
Yes. Stacking layers atop each other creates a location that varies structurally from its neighbors.

When possible, avoid ending all layers in the same place.
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Re: 20 foot seacraft deck

Post by fallguy1000 » Sat Jun 09, 2018 8:39 am

lelandtampa wrote:
Fri Jun 08, 2018 8:55 am
Probably going to go long tab first so I dont get an airbubble at the edges of the lower layers.
You should be using some type of laminating roller that would avoid air on layers. Paint rollers are great for moving epoxy early, bit at the end of the process they tend to lift fabric.

An ultra cheap roller can be made from pvc tubing. Avoid cleaning in acetone. We simply wipe ours with paper towel.

Otherwise, a laminating roller does not lift the fabric.

I use a 6" bubble buster with a 1/2" or 3/4" circumference. It doesn't lift wetted glass and allows the bubbles to collapse without moving.
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