Building a KARA Hummer Layout Duck Boat #6: Applying the Plywood Hull Panels

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Blog entry by DustyMark posted 05-19-2015 08:37 PM 9792 reads 0 times favorited 4 comments Add to Favorites Watch
« Part 5: Fitting the Plywood Hull Panels Part 6 of Building a KARA Hummer Layout Duck Boat series Part 7: Sealing the Hull Interior »

Fiberglass Experiment

I applied a layer of fiberglass cloth to the plywood hull panels before work, betting they would be “green” cured in the afternoon upon my return. Using Raka 127 Resin and Raka 350 hardener at 72 degrees and 48% humidity the fiberglass was set perfectly in about 8 hours. It was bonded, yet flexible enough to not restrict the plywood from curving around the hull ribs.

The epoxy is wet into the fiberglass cloth with a foam roller.

I never pay extra to ship the fiberglass on a roll, so there are wrinkles that need to be worked out with a spreader.

It doesn’t take much effort to work out the wrinkles.

Immediately before applying the plywood panels, I applied a second layer of epoxy to fill the weave on the fiberglass cloth.

Hull Plywood Application

I mixed up a 6 ounce batch of thickened epoxy and my wife and I each took half the batch and spread it on the ribs and gunnels. We then screwed the middle hull panel, we had fit earlier, into position. We followed the plan instructions and worked our way from the middle, down the ribs, and onto the gunnels to affix the panels with silicon bronze ring shank nails. It took more force than I anticipated to bend the plywood to the outer ribs, but we succeeded. We then applied each end panel in a similar manner.

Setting some nails with a punch.

The hull took a nice shape.

It’s definitely starting to look like a boat!

Upright view.


I forgot to make my alignment tool that helps mark the nail holes to assure they landed in the center of the 3/4” gunnel. I realized this after we had already spread the thickened epoxy on the ribs and gunnels. The epoxy would have set up if I had taken the extra time to make the tool, so we rolled with it.

Unfortunately, I missed the mark on six nails and busted through the gunnel on either the inside or outside edge.

I split the wood the rest of the way and used the chip to make the repair. Thickened epoxy is both gap filling and structural and makes these repairs easy. Here I am applying the chip to the bed of epoxy.

The chip fit well in the repair. I placed tape over it and then clamped it lightly in position. I did this for all six damaged areas.

Alignment Tool

This simple little tool would have saved me 6 small repair jobs and also prevented me from filing most of the heads off of quite a few nails when I rounded over the hull edge in preparation for fiberglassing.

This fits over the plywood that is extending from the edge of the gunnel and finds the center of the gunnel. I trim my plywood edges ahead of time, so the slot on the alignment tool doesn’t need to be crazy deep. I cut the edges of the jig to 15 degrees since the entire hull and deck meet the gunnels at about that angle.

Flushing the Edges

The hull panels needed to made flush with the gunnels.

A router with a flush trimming bit removed much of the excess wood, but since the hull is at an angle, there was at least 1/4’ of wood remaining to remove all the way around. NOTE: Later in the project, I decided to not chicken out when flush trimming the deck panels. I kept the router level to the ground for a finishing cut to allow the bearing to rub flat on the gunnel and it removed all the plywood flush to the gunnel. The reason I didn’t try that on the hull plywood was fear of going beyond level and removing some of the gunnel. However, removing the remaining 1/4” of hull plywood around the perimeter of the boat with hand tools was way too much work…that’s what drove me to take the chance on the deck plywood. It worked fine.

I settled on my aggressive cross-cut saw and an old file that has what looks like rows of hacksaw blades for teeth. Both of these worked well for the task.

Rounding the Edges

The hull and the deck receive fiberglass. The fiberglass needs to bend around the gunnel to provide a double layer of protection to the gunnel. However fiberglass can’t be applied around a sharp angle. That’s why the edges of the hull and the deck must be rounded where they meet the gunnel. The previously mentioned file was perfect for this since many of the nail heads were too close to the edge. Thankfully, I used silicon bronze nails to apply the hull and they were easy to file off when needed.

Rounded edge.

Another view.


Even with the challenges, I’m happy with the way the hull turned out. This is a duck boat that gets painted and nobody will see the mistakes! Fiberglassing the inside of the hull panels with 2.3 ounce cloth worked well and I will do it to the deck panels also. It’s an effective means of applying a light layer of waterproofing.


In the next installment, I’ll discuss sealing the hull interior for water protection.

-- Mark, Minnesota

4 comments so far

View SPalm's profile


5338 posts in 5165 days

#1 posted 05-19-2015 08:43 PM

It really is looking like a boat.
Nice recovery with the nails, and I agree that it will not be a problem once all the epoxy is done.

Fun to watch, especially from a sofa.

-- -- I'm no rocket surgeon

View DustyMark's profile


519 posts in 3353 days

#2 posted 05-19-2015 08:56 PM

Thanks Steve. Materials are arriving today to build flip blind doors for me and a dog blind for Copper. I plan to blog through the entire fitting out process and into the hunting season. I’ll also show the process of building a set of oars and a launching trailer. The boat is probably about 60% of the overall project.

-- Mark, Minnesota

View shipwright's profile


8760 posts in 4081 days

#3 posted 05-19-2015 10:33 PM

Looks like a nice piece of work.
If I might offer a tip, I find glass cloth much easier to apply if smoothed out flat on the dry wood and then wetted out by pouring a puddle of epoxy in the middle and spreading outwards with the bondo spreader that you finished with.
Rollers work well with polyester resin but with the stickier epoxy they tend to lift the cloth behind them and make extra work.

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

View DustyMark's profile


519 posts in 3353 days

#4 posted 05-20-2015 01:32 AM

Paul, good call. I’ve done it both ways. I had never used this 2.3 ounce cloth before and thought I might get better saturation starting with a roller.

-- Mark, Minnesota

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