15-footer Bow Hatch Cover Fabrication

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
dyoung16611
Posts: 12
Joined: Wed May 12, 2021 12:01 pm

15-footer Bow Hatch Cover Fabrication

Postby dyoung16611 » Wed May 12, 2021 12:43 pm

Please give me advice on how to properly fabricate a bow hatch cover that will not warp over time for a 1983 STRIPER 15.

Given that I'll be fabricating this from several mahogany planks that I will plane and joint, I want to avoid the fate of my last one purchased online. Despite having cross boards on the underside, it warped and split. Instead of simply joining a few boards on their long edges, I am considering adding two boards perpendicular to the fore and aft edges in an attempt to prevent warping. In addition, my (unproven) plan is to glue them with epoxy, then lay down a few coats of West Systems epoxy with 207 clear hardener, then a bunch of coats of Epifanes varnish. While this seems like a great process for single boards used elsewhere on the boat, I'm concerned that using epoxy on a fabricated piece containing several boards may cause cracks if or when those boards expand or contract over time.

Q: Is my worry about board cracking over time valid?

I would like to know how others have solved warping of the bow hatch.
1983 15' Striper

dtmackey
Posts: 504
Joined: Thu Sep 28, 2017 9:29 pm

Re: 15-footer Bow Hatch Cover Fabrication

Postby dtmackey » Wed May 12, 2021 1:32 pm

I cut all my pieces from soft maple and Sipo mahogany and then glued them up with West Epoxy into large pieces and then cut them to fit my interior. I'm sure your not going to the length I did with the number of wood pieces to build the hatch, but I would plan on using 4 - 6 pieces as this helps prevent the grain pattern from cupping. Also be alert to the grain curve and alternate them when glueing up.

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On the bottom I installed backer pieces to add strength and prevent warping. These are also epoxied in place and use flat head screws.

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As for strength, I tested the epoxy interface and a failure happens in the wood grain before the epoxy interface.

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Make sure you seal both sides with plenty of vanish or another good material since wood loves to cup when one side is sealed and the other left without.

D-

dyoung16611
Posts: 12
Joined: Wed May 12, 2021 12:01 pm

Re: 15-footer Bow Hatch Cover Fabrication

Postby dyoung16611 » Wed May 12, 2021 3:29 pm

Dtmackie, thanks for your reply. Impressive that the wood grain fails before the epoxy bond.

Q: will three coats of epoxy applied to the entire piece prevent cupping?

Q: are the backing board for strength rather than to prevent cupping?

Also - Your chronicles (and results) are what inspired me to tackle this in the first place. Thanks for the inspiration.
1983 15' Striper

dtmackey
Posts: 504
Joined: Thu Sep 28, 2017 9:29 pm

Re: 15-footer Bow Hatch Cover Fabrication

Postby dtmackey » Wed May 12, 2021 3:50 pm

I find that epoxy can be a challenge to apply to the wood, but when done right, it really provide a nice sealed surface.

If using epoxy, make sure you use the UV hardener or you could be doing it over as the sun tears up epoxy that is not designed for outdoor exposure.

Also, it's best to put a couple coats of varnish over the epoxy.

I only used Epifanes varnish on my wood.

D-

dyoung16611
Posts: 12
Joined: Wed May 12, 2021 12:01 pm

Re: 15-footer Bow Hatch Cover Fabrication

Postby dyoung16611 » Wed May 19, 2021 7:10 am

@DTMackie - when gluing the boards together with West System 105/207, did you add a filler? If so, which one? I don't want to see seams and I'm wondering if filler will enlarge the seams.
1983 15' Striper

dtmackey
Posts: 504
Joined: Thu Sep 28, 2017 9:29 pm

Re: 15-footer Bow Hatch Cover Fabrication

Postby dtmackey » Fri May 21, 2021 9:06 am

dyoung16611 wrote:@DTMackie - when gluing the boards together with West System 105/207, did you add a filler? If so, which one? I don't want to see seams and I'm wondering if filler will enlarge the seams.


Sorry, missed your question when I visited here the past couple days.

If you are using epoxy to glue or laminate pieces of wood together you should NOT be using any filler as the bond is between the wood and epoxy, filler only decreases the bond strength and prevents the epoxy from wicking into the wood grain. The only place to use filler is if you are looking to thicken the epoxy for filling or making a peaut butter consistancy for bonding to vertical surfaces where plain epoxy would just ooze out.

D-

dyoung16611
Posts: 12
Joined: Wed May 12, 2021 12:01 pm

Re: 15-footer Bow Hatch Cover Fabrication

Postby dyoung16611 » Sat May 22, 2021 12:27 pm

D - Thanks again for the help.
1983 15' Striper