# layup schedule over corecell for interior parts? Is my math good?

Discussion in 'Boatbuilding' started by leaky, Sep 12, 2017.

1. Joined: Sep 2008
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### leakySenior Member

Hi,

For interior parts in a new boat build I'm using 5/8 corecell in a 5 lb density. I've been working with VE & PE so have both on hand; I'm thinking if something is likely to be under stress, since I am going to keep things just strong enough but not overbuilt, I'll use VE otherwise PE.

At the moment I'm thinking for a light duty part (ie bathroom wall) I'll use a single layer of 1.5 ounce mat and PE resin, for a part which is semi structural (ie bunk for instance) I'll use a layer of 1708 with a layer of 3/4 ouce mat on top and will do it with VE resin so it resists fatigue better. Is this sane?

My math what I'm figuring is like this for weight of the wet glass per yard, are these good estimates?

3/4 ounce mat: 6.75 ounces per yard, 20.25 ounces wet (glass weight X 3)
17 ounce roving: 34 ounces wet (glass weight X 2)

1708 plus a layer of 3/4 ounce mat on top, both sides of a piece of core = (34 ounces roving + 40.5 ounces mat) X 2 = 149 ounces or 9.3 lbs

1.5 ounce mat, both sides of a piece of core = 40.5 ounces X 2 = 81 ounces or 5 lbs

Thanks!

Jon

2. Joined: Sep 2011
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### TANSLSenior Member

I can not tell you anything about the weight of your compounds because it will depend in great measure on the amount of resin you put. What I can tell you is that the inner layers will work, normally at compression, not at tension and that the outer and inner laminate should be very similar so that the distribution of stress is as symmetrical as possible with respect to the neutral axis of the resulting panel .

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