Embedded Reinforcement Material

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
LGJTTU
Posts: 2
Joined: Sun Jul 16, 2017 7:21 am

Embedded Reinforcement Material

Postby LGJTTU » Tue Nov 14, 2017 8:11 am

I am in the middle of a complete restoration of a 1965 Boston Whaler 13. I have the gel coat completely stripped off and am down to the fiberglass. There are a couple of areas where I need to attach equipment with screws into the fiberglass: two handrail mounts; and the combined sidelights navigation lamp. I have opened up the fiberglass in these areas with the intention of installing material behind that will allow me to screw into it. I will then go back over with new glass on top and encase it all.

I have two options in mind:

--install some type of backer board. If I choose wood, I am concerned that water penetration could be a problem in the future. Also, will it hold the hand rail mount well. I considered [Whalerboard] or some composite, but I don't know if the screws could have a tendency to strip out with this method;

--fill the cavity about 1 inch deep or so with Marine Tex or some other reinforced epoxy.

What are your thoughts on these? Do you have any other recommendations?

jimh
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Location: Michigan, Lower Peninsula
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Re: Embedded Reinforcement Material

Postby jimh » Tue Nov 14, 2017 9:25 am

I would be guided by the experience of Boston Whaler. They typically used wood for embedded reinforcement points where self-tapping screws would be used as fasteners. Often the wood was plywood.

They also used a material called Whaleboard for reinforcement when the material was to be threaded to receive a machine screw. See

http://www.whalelite.com/products.asp
http://www.whalelite.com/applications.asp
http://continuouswave.com/ubb/Forum8/HTML/000878.html

You can also use a thermoset plastic laminate like a grade G10 material. See
http://www.sdplastics.com/phenolic.html

As for making an embedded area of epoxy resin mixed with fillers, this is usually done only when trying to avoid removal of the surface laminate structure. Embedded pools of epoxy resin and fillers are usually introduced into a below deck area through a small hole, and they fill a cavity around the hole intentionally created in the foam to receive the epoxy resin and filler mix. I do not recall anyone ever describing a method of removing the upper laminate, then creating a region of epoxy and filler material below the surface level of the laminate, then rebuilding the laminate.

For securing the combined sidelights lamp at the bow, I suspect you may also have the particular lamp used in Boston Whaler boats that also serves as a chock or guide for mooring lines. My understanding of the method used by Boston Whaler to fasten that lamp-chock assembly was through-bolting. If you have only a lamp housing to mount, then the strength of the mount can be less than if the lamp is also a chock.

For securing rail bases, use of epoxy resin with filler has been suggested and tried with good outcomes. See the FAQ answer at

http://continuouswave.com/whaler/reference/FAQ/#Q7

dtmackey
Posts: 37
Joined: Thu Sep 28, 2017 9:29 pm

Re: Embedded Reinforcement Material

Postby dtmackey » Tue Nov 14, 2017 10:48 pm

If the areas you need a backer are not in a wet location (below waterline) or flat deck areas where water can get trapped or into the screw hole, I would use wood. I say this and detest wood in transoms and replaced one in my Mako several years ago (see pics, was soaking wet rotted). I went poured ceramic (NidaPour) and think it was the best option to this day. The biggest problem is sealing holes and if the screw is a railing fitting or something simple, I would not question using wood and make sure you seal with bedding compound or 4200, but below waterline or a deck area constantly getting wet, I would consider something else.

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LGJTTU
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Joined: Sun Jul 16, 2017 7:21 am

Re: Embedded Reinforcement Material

Postby LGJTTU » Wed Nov 15, 2017 1:33 pm

Thank you very much for the suggestions; I will let you know how it goes.