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Old 24-09-2013, 21:27   #1
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Deck hatch installation - which type of sealant?

I am installing a replacement large foredeck hatch (80cm x 80cm or 32" x 32") on a 52' sailing yacht.

This is a big hatch and will be held in place by self tapping screws into GRP and adhesive/sealant. I am worried that using an adhesive/sealant like 3M 4200 will not be structural enough given the slight flexing in a GRP deck. Should I consider using a polyurethane 5200 type bonding sealant?
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Old 24-09-2013, 23:43   #2
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I am installing a replacement large foredeck hatch (80cm x 80cm or 32" x 32") on a 52' sailing yacht.

This is a big hatch and will be held in place by self tapping screws into GRP and adhesive/sealant. I am worried that using an adhesive/sealant like 3M 4200 will not be structural enough given the slight flexing in a GRP deck. Should I consider using a polyurethane 5200 type bonding sealant?
My understanding is that Dow 795 is the sealant of choice for this job.
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Old 27-09-2013, 14:50   #3
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Re: Deck hatch installation - which type of sealant?

Dow 795 is for sealing deadlights not a movable hatch. I'm guessing you're installing a framed (stainless or aluminum) hatch like Bomar or Lewmar makes? If so, simple butyl tape is all that is needed. The screws are enough to adhere the hatch.
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Old 29-09-2013, 17:45   #4
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Re: Deck hatch installation - which type of sealant?

Thanks guys. The hatch is a Goiot traditional hatch (heavy duty and heavy weight) with an aluminum frame like the Lewmar version.

Not familiar with Dow 795 and have never used butyl tape (but it looks good). Neither of these are available here in Fiji so I am going to use a Sikaflex 291 which seem to have the right balance between adhesive and sealant.
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Old 29-09-2013, 17:53   #5
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Thanks guys. The hatch is a Goiot traditional hatch (heavy duty and heavy weight) with an aluminum frame like the Lewmar version.

Not familiar with Dow 795 and have never used butyl tape (but it looks good). Neither of these are available here in Fiji so I am going to use a Sikaflex 291 which seem to have the right balance between adhesive and sealant.
4200 and 291 are very similar products. ( both are polyurethane adhesive/ sealants) Both are suitable for what you want

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Old 29-09-2013, 18:52   #6
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Re: Deck hatch installation - which type of sealant?

Quote:
Originally Posted by Streetcar View Post
...This is a big hatch and will be held in place by self tapping screws into GRP and adhesive/sealant. I am worried that using an adhesive/sealant like 3M 4200 will not be structural enough given the slight flexing in a GRP deck. Should I consider using a polyurethane 5200 type bonding sealant?
You are right. If you are using self-tapping screws into GRP you better use epoxy on the screws and 4200 under the frame - do not use butyl. If you can thru-bolt with a nut under the deck, then you are not only better off, but then you wouldn't need to rely on the "glue" to keep the hatch in place.
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