Plascore bottoms

In a post below I mentioned poking and patching a hole in a 5 or 6 year old boat. The sides are plywood but the bottom is Plascore.

Plascore does make the best not-aluminum bottom for a driftboat. For me there is no doubt. I used to think Plascore made a lighter boat and that turns out to be wrong. You can make a light boat with Plascore but it's not a good idea.

Plascore itself doesn't weight much, but by the time you put enough fiberglass on it to make a good bottom panel you're right back up to stitch and glue plywood weight.

So then is it better? Because it is. Plascore doesn't soak up moisture. I'm fixing this boat now after 5 or 6 years of hard use. There are some chine ding and bottom wacks that would have cause major damage to a plywood stitch and glue layup, if they hadn't been fixed almost immediately.

With the Plascore I was able to be lazy for half a decade. And now I'm finally fixing it and it's no big deal.

My next boat will have a Plascore bottom and chine and Plascore for 8" up the side of the boat. Then I'll switch to oiled plywood, with no glass on it at all. No ribs. 3/8" Meranti Hydrotech sides and 1/2" Meranti Hydrotech deck. The deck will be removable. It will bolt down onto a 1/2" inch thick closed cell foam gasket. So it could be an open boat if you want it that way. Or a decked white water boat.

I don't expect to ever use it as an open boat however. I'm going to rig a 17' foot decked white water boat so it works well for day trip fishing too. 64" inch bottom. 17' feet long. That's a wide boat. I've already built to 58" inches wide and that was good. Wider is better. For a lot of reasons.

I know from experience Plascore makes the best bottom. No-ribs oiled plywood above is an unproven experiment. Yet to happen. I've been out of the shop for a half a year now because of health issues. But now all that's out of the way.

I'm a new poster with a lot of respect for the opinions and knowledge that I've found on this forum so I hope this doesn't come across as a challenge, but I've read over and over again about the benefits of Plascore and still I can't figure out what advantage it has over Core-cell. I assume there is something to it since it is so highly endorsed. Can somebody elaborate upon, or correct my summary below?
I'm slowly putting together a plan in my head for the ideal boat to build once I get the courage to commit the time. And material selection is of course the first (or second) question that I need to answer...

Wood - easy to form, high inherent stiffness, easy to source. Generally limited to 4x8 without scarfing, subject to water absorbtion.
Plascore - high moisture resistance, maybe lighter weight, easier to join or buy in larger sizes. The down-side being the labor involved in the hollow edge and its inherent lack of stiffness.
Core-cell (or other foam product) - best of both worlds? High cost? (I haven't actually shopped for Plascore or Core-cell yet).

Thanks for the feedback.

Ah Corecell. I've never used it so it might be just as good or even better. I forgot about Corecell when I said Plascore was the best. The last I heard Corecell was expensive. What does it cost? 3/4" inch Plascore is about 40-50 bucks a sheet before shipping I think. I bought 12 sheets quite a few years ago so I'm not sure the current price. I'm retired and don't build much anymore. Well I've got one project going now. But that's it.

I've also heard rumors foam can soak up some moisture. I do not know if that is true or not. Plascore does not soak up moisture at all.

My guess (although I don't know because I've never used Corecell) is that they're both good.

I used end grain balsa for a few boats back in the late 1980s. Balsa layups are OK on sailboats but not on drift boats. Balsa soaks up way too much moisture. Even worse than plywood.

Boy, you are right about the cost difference. I'm sure you can get better pricing in bulk or by calling direct, but here are the costs that I found doing a quick online search.
All for 4x8x3/4" panels (or equivalent)
Nidacore: $65
Plascore: $120 (4 sheets of 2'x4' - I'm sure you can find it cheaper)
Divinycell H-80 5lb: $247
Core-cell A-550: $306

If the foam provides better strength or durability I could see it being worth three hundred extra dollars to do just the floor... sounds like people have had good luck with Plascore though so maybe it isn't worth it.

I conducted some tests a while back, and found that the Plascore panel took a lot more damage before any failing point as apposed to the NidaCore which broke on the first impact. In my opinion the Plascore appears to be much better. The Plascore uses much smaller cells which increases the stiffness through the sheet. I used a whole 1/4" thinner plascore and still got better results. The Plascore panels are also seamless, unlike the Nidacore panels, a lot of the fracturing occurred along the seams of the NIdacore.

Jeremy Christensen

Interesting comment from Tungsten about foam and peeling. I have not used Core cell. I have built a few seat top panels with foundation foam. Foundation foam has a slick surface resin does not adhere to much at all. You can lightly sand foundation foam with 220 paper and then use it in a layup. Which works well enough for seat top panels but not much else. After the layup cures you can grab a corner of glass with pliers and peel it right off the foam, without much effort. That's not at all easy to do with Plascore.

I think Corecell has fibers built into the foam, perhaps in order to enhance bonding between foam core and surface layups. Plascore has A layer of fiberglass mat half heat melted into the plastic core (polypropylene I think). That layer of mat is very well bonded to the plastic, which ultimately makes a very secure bond between the core and the surface layup. It is good stuff.

Foam has little shape memory too, so if you lightly ding a foam layup and dent the skin, thereby compressing the foam underneath, that ding usually stays concave. Plascore layups are far more likley to recover their shape. Severe impacts are going to damage both.

I'm probably repeating myself with this post but I finally got this boat into the shop today. There wasn't enough room last few weeks because I had a 4' foot by 19' foot layup table assembled. I took the layup table down because my panels are now built, and because rain is on its way and I need to get this old boat fixed before it gets wet.

This (photograph below) was the second boat I built with a Plascore bottom, finished up in the Spring of 2007. Nine and half years ago not seven years. I looked at the date stamp on a photo taken just as it was first finished.

I didn't put enough glass on the chine back then but that's the point. Here this boat is almost 10 years later and the glass is beaten all the way to the quick on the chine. And it doesn't matter. No big deal. Turn it over. Dry it out for a day or two and patch it up. This is, for what it's worth, already ground down some, with a 60 grit disk on a right angle grinder. 9 years of river damage didn't grind it down quite this far.

If this had been a plywood/fiberglass bottom moisture would have wicked sideways a half a mile from the damage points and caused all kinds of trouble. With Plascore I used to say you could be lazy for a few months. Truth is you can be lazy for ten years. I'll grind the finish off the whole chine and patch it up soon. Next few days.

And then back to the bigger decked 17 footer. Which is now ready for its own Plascore bottom panel. It's going to be a busy winter for me. I've built two all Plascore boats in recent years. Now I'm back to Plascore bottoms with plywood tops.

Hi folks, I'm putting together a plan for a boat here in Australia (!) and about to order the materials. I expect most of the drifts will be on rivers which have few boulders, but lots of willows. There is one river I might have a crack at which has some Grade 2 rapids, but I will need to do some hours on the oars first!

We don't have Plascore here but I have found another supplier
https://trojanfibreglass.com.au/product/pp-honeycomb-panel/
... the Plascore rep in the USA said this stuff looked equivalent.

In terms of materials thickness I'm thinking:
bottom ~20mm honeycomb i.e. 3/4"
sides - leaning towards 3/8" ply for greater impact resistance on trees

Does that sound right? Thanks in advance

I've used 3/4" inch Plascore with good success. Jeremy who sometimes posts here has used 1" inch which I'll probably buy the next time around.

Stressed skin panel stiffness increases as the square of it's diameter. And 1" inch does not weigh much more than 3/4" inch. So 1" would be substantially stiffer without adding (hardly any more) weight.

Australia! I have a buddy who lives in Bateman's Bay. We bought plane tickets to Sydney, so we could visit him, two months before the pandemic hit. We had trip insurance so we got our money back. I still want to visit. Patrick--my buddy over there--fishes all over New South Wales, Tasmania and (occasionally) South Island NZ. He fishes the salt water rocks at Bateman's Bay 2 or 3 times a week.