Building the "Swiss Army Knife" of Small Boats...Wood Duck Double #18: Filleting and Fiberglassing the Hull-to-Deck Seams

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Blog entry by DustyMark posted 07-04-2020 06:06 AM 1194 reads 0 times favorited 4 comments Add to Favorites Watch
« Part 17: Stitching the Hull and Deck Together Part 18 of Building the "Swiss Army Knife" of Small Boats...Wood Duck Double series Part 19: Rounding the Edges of Hull and Deck »

I Hate This Step!
I had planned to wait until morning, but I noticed the epoxy was cured late in the evening and decided to go ahead with it…bad call. I didn’t get done until midnight. This is the worst step in the whole build for me, since these seams are the least accessible. The front hatch is pretty small and I have a size 7 3/4” melon…not a good combination. I gave up trying to work the final passes of the fillets with a mirror and just put on an old hat and my reading glasses and squeezed my head into each hatch. I had to wash my hair and beard with white distilled vinegar to get out the uncured epoxy! That stuff works works well if you don’t wait too long.

The fillets are quite important on these seams since the panels meet at a sharp angle and the fiberglass tape would never make the corner without the easing of the radius provided by the epoxy fillets. The fillets also provide structural strength to the seams.

The following photos are taken with the boat upside down after I’ve completed the task. This is a view of the bow bulkhead, from the cockpit. It shows all seven panel seams meeting at the bulkhead. The hull-to-deck seams are the outermost.

Closeup of the seams at the stern bulkhead from inside the hatch

Closeup of the seams at the bow bulkhead from inside the hatch. NOTE: The bulkhead to deck seams receive no fiberglass tape, only the epoxy fillet. The top of the bow bulkhead had a 1/2” gap below the deck. Apparently this is how they cut the bulkhead to avoid any interference with the final shape. That results in a pretty thick fillet!

Fiberglass Tape
It’s too difficult to wet the fiberglass tape in the boat.

The plans suggest pre-cutting, rolling the tape loosely, and then soaking it in epoxy in a disposable pan. This step is done after all the fillets are complete. I mixed 9 ounces of epoxy to fill the pan enough to soak the tape. This method worked well, except I was too slow with applying the tape in the bow and stern and the epoxy began to cook off on the the long strip for the cockpit. That would have been a waste of epoxy and fiberglass tape. I quickly unrolled them to dissipate the heat and they appeared to bond well. I added an extra coat of epoxy to the tape to be sure there were no adhesion problems.

I’m happy with the way the hull-to-deck seams turned out. Yes, it was a struggle, but it worked out fine.

Shape and sand the hull seams for fiberglass prep.

-- Mark, Minnesota

4 comments so far

View Redoak49's profile


5271 posts in 3101 days

#1 posted 07-04-2020 10:46 AM

Great job and interesting. I will never build a boat but enjoy watching your build.

View DustyMark's profile


518 posts in 3183 days

#2 posted 07-04-2020 02:40 PM

Yeah, it’s not for everyone. It does show another way wood can be formed in a 3-D fashion. As my house became full of furniture, I’ve transitioned to these type of projects. Either way…wood is good!

-- Mark, Minnesota

View shipwright's profile


8726 posts in 3911 days

#3 posted 07-04-2020 05:10 PM

Just my opinion but that is terrible advice for application of the tape. It uses way more (expensive) glue than necessary and must make one unholy mess.
Give this method a try. You shouldn’t even get any on your gloves if you do it right.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese!

View DustyMark's profile


518 posts in 3183 days

#4 posted 07-04-2020 06:29 PM

I agree. I was just blindly following the build instructions. I could have certainly laid the cloth on dry in the main compartment. It actually didn’t drip too bad since I squeezed out the excess before removing it from the pan. I liked your method. I’m still making mistakes and learning on my 10th build…

-- Mark, Minnesota

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