Custom 19' all weather, minimalist, strip plank composite 'go fast'

Sorry, only just seeing this...

The wood had no moisture in it, it was all pretty high grade air dried or kiln dried but stored outside covered for months. The blisters were all on the chine edge and because our vacuum schedule was--in light of knowledge since gained--absurdly ambitious, something that a team of 4 experienced vacuum techs might contemplate in 55F weather but probably still decide is too risky. The epoxy was setting and if the vacuum had pulled perfectly on the first go it would have likely worked and pressed the bubbles on the chine edge out just fine but the bag was just gushing leaks--there was no vacuum happening whatsoever--and it was obvious I was never going to fix it in the 20 minutes I felt like I had left so I ripped all the vacuum material off and hand smoothed the flat surfaces before the epoxy set. Then I spent a week with a dremel and syringe of thickened epoxy and lots of sanding grinding and filling blisters, then just massive wet sanding and more fairing to remove about 30% - 60% of those two layers of glass to make sure I chased all the voids out. I lost a lot of glass in that process but the hull faired out beautifully. Then, I did it right and broke it into sections as shown the video... carbon fiber over the hull to within a few inches of the sheerline with a good solid vacuum going but broken into 5 parts, then S-glass vacuumed over that for abrasion protection, done in two halves.

I saw pics of your catamaran, congrats, she looks lovely.

 

Part three of the timelapse... Painting the hull to about 80% (in our kitchen!), then starting to build out the inside including deck, most of her plumbing, and building the cowl.

 

So, not blisters, but air pockets.

 

I suppose.. I don't work with fiberglass or gel coat so in my mind they were the same thing but I know for boat rehab there's a little difference. This isn't intended to be a trailered boat. She's intended to live at least initially for many years in the water so any voids in her hull layers I went to great lengths to avoid. That's the main reason I did on the vacuum processing on her.

 

Now I'm dealing with insurance and agreed on value... I ended up getting a marine survey done yesterday. Thankfully, the surveyor came from racing and had a good bit of experience with higher end strip-plank and cold mold composite construction. I don't know a lot of boat builders outside of guys that do some fiberglass, so I assumed for most of the last three and a half years of construction that I was making any other backyard 'hammer to fit, paint to match' strip-plank boat, but now after a few professionals have examined her, we can certainly say she didn't end up that way.

After watching some of the timelapse footage and examining the boat the surveyor said he'd describe her much more as 'cold molded composite', which I suppose she is since bow, stern, deck, cowling, transom, bulkheads, and knees eneded up as multiple layers of wood plus s-glass and CF. I've just been vaguely thinking of that as 'composite.' Once insurance is in place I can drive her to the Suzuki mechanic for final touches and sea trial her. When she was just a hull with no fittings or installations at all she was 625lbs. Now with all the offshore electronics, 60hp engine, 18 gallons of gas, batteries, and fancy shoxs seat she oughta be about 1200lbs, so still crazy light for a run swamped vessel that displaces about 5000lbs.

 

Looks great

 

Got more timelapse footage edited. This is filling out her insides and cold molding various small curved structures--her aft hatches, inwales, and finishing her cowling. And her deck. Most of these parts were 1/4" WRC plank with 1/4" white oak sandwiched in S-glass or carbon fiber. Generally anything I considered a potential wear point is capped with white oak and 6oz s-glass: deck, cowling, verticals on her aft hatches, edges of the inwales, etc. This video basically picks up from part 3 and takes her to paint ready...

 

How u get 5000 pounds displacement?

Boat looks great.

How do you get back on out of the water?

 

Since I modeled the vessel entirely in Fusion 360 and built to those exact dimensions it's very easy to slice the model into different portions to get volume numbers and from that compute displacement and actual volume of foam, bilgeable volume, etc.

For exit and boarding on the port aft side there's a gap in the railing and handholds built into her inwales. You can see it towards the end of the video. It's not in this video but I even did rubberized (SoftSand in LPU) grips there. Her freeboard is low so it's about a 12" lift over the side, like hauling out of a competition swimming pool. For a beginner freediver in longfins, it's even easier than that because they can kick themselves up at the same time and then sit on the inwale and remove their fins. If they don't have that minimum fitness/competency they won't even make it through the open water portion of the first level classes (which are all sandy beach entries, no boats).

Ladders aren't my favorite in socal, they cannot be used with longfins and in our swells even experienced people lose gear and get slammed around. A huge swim step is nice but for the swim step to be safe and usable for my application it is not very realistic for an outboard powered vessel.

 

If I was 15-20 years younger and in so cal, I'd sign up just for a ride, I suspect the boat will fulfill its' mission statement well.
Nice work.

 

I'm guessing the 5000lb displacement is when the boat would start to flood? Or when it's swamped and starts to sink?

The BRP rotax might be close to what you are explaining for a swim platform with an "outboard," but it hasn't caught on much, in my opinion, and it has much more horsepower than you would need.

https://www.boattrader.com/boat/2025-alumacraft-competitor-185x-sport-max-9580470/

 

17x5x1 = 85 cuft @ 64 = 5400

I guess close. Somehow, I thought narrower and less below wl.

 

I actually looked at the Rotax engines recently. My wife is a pilot and her flight school has exclusively Rotax engines in their planes. The submerged marine outboards certainly seem cool but I didn't want to experiment there and am not an engine guy so I kept it simple.

5000lbs is basically the displacement of her hull to sheerline. USCG has a more precise definition but that's basically what it is. She would be virtually impossible to sink unless she were piled with steel/lead because she has so much reserve buoyancy and foam. She needs sea trials but she is engineered to run swamped to within a three or four inches of her sheerline before her bilge even starts to get wet.

She has open scuppers so if loaded with more than I think about 800 pounds (again need to sea trial) her aft deck might be at the waterline if she's not underway. To swamp her to sheerline would a good deal more weight and continuously breaking waves to keep her swamped.

I'm actually updating my CG model to reflect where and how much foam she has so I can document officially.

 

I wanted to send the attached sheet (re a quick and easy way of assessing stability) to Socal in a PM, but this forum does not allow attachments in PMs, hence why I am posting it here instead now.
I am sure that other folk might find it useful as well.
Although it is primarily aimed at fishing boats, the same principle can be applied to Socal's boat.

 

This is interesting... Most stability tests I have been looking at are concerned with off centered loads (transversal shift). When I built the scale model before starting construction I loaded the model with an improbably high boat weight COG and then stacked weight on the gunwale to see what it would take to submerge the freeboard edge, which is more or less what the USCG tests are checking.

The roll test adds an interesting metric and is a pretty good illustration of why so many people conflate initial stability with ultimate stability. A fast rolling boat is alarming to casual boaters (ie she's dangerously tippy!!). If we raise COG the same boat likely rights more slowly off heel, perhaps feeling gentle, but it takes ultimately less to actually flip it. The most stable 'feeling' you could create with the roll test would be achieved by raising the COG as high as possible but this would be the most dangerous loading situation.