Foam core polyester V's cedar plank/balsa epoxy

[Redreuben]

YesMaybe;
To address your original question there are millions of boats out there with gelcoat finishes that are still serviceable, gelcoat is very repairable with basic fibreglass skills epoxy and two pack is also durable but requires a slightly higher skill set and more labour time to repair.
Most production cats of a relatively modern vintage would have a vinyl ester tie layer behind the gelcoat under the waterline to prevent osmosis, again making them more repairable.
All epoxy builds are usually limited to one offs where high performance is the goal, engineered laminates to achieve an outcome v overbuilt and bulletproof.
And of course many variations in between, probably rare but an all vinyl ester production laminate would be a great middle ground.
I would be happy with a cedar/foam epoxy boat. I would be wary of a polyester boat without the vinyl ester back up unless the boat has been upgraded to an epoxy coating below the waterline at some point, or cost it in to the purchase.
Disclaimer; I have not owned a large yacht but have previously worked in fibreglass, yacht construction and repair for some 25 years.
Cheers.

[smj]

Originally Posted by Redreuben

Smj; the filler only has to be as strong as the Cedar or Kiri so it's a pretty lightweight mix not a heavy duty adhesive type mix.


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Thanks, didn't think of that.


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[UNCIVILIZED]

Originally Posted by Yes maybe

Hi,
Have searched on here and google.
The above title is in relation to purchasing a 38' to 43' cat for cruising (2 or more yrs). And longer ownership of boat.
1/ Trying to work out, the for and against for each construction method.
2/ Strength - cruising safety - hitting submerged objects.
3/ The boat may be 20+yrs old - Epoxy v Polyester Gelcoat - Osmosis and other longer term issues.
4/ Ongoing maintenance costs for polyester gelcoat v epoxy with painted top coat.
5/ The cedar plank epoxy will be heavier the foam core, by?%.

Thanks
Boris.

Big picture wise, given that you're looking at older boats, what really matters is finding one which was both well built, & also well cared for. As any cored boat of that vintage has a decent chance of having water intrusion issues, regardless of the type of core, construction method, or resin type.

Which leads to there being advantages to a foam cored boat, as it won't rot. Though if there is water intrusion, with both types, usually the core will need replacing when it's time to fix things.
Albeit, again, how much the water migrates from the original intrusion point depends almost entirely on the workmanship which went into the build. As if kerfed foam or balsa was used, & the kerfs weren't filled when she was built, then the water can travel quite extensively. And in a timber cored boat, the wood will tend to wick the water. More so than is commonly stated in the literatue in a lot of cases.

So you need a Really good survey prior to buying a boat in either case. One which preferably is done by a Surveyor well versed (certified) in the use of a Thermal Imager. As it'll pick up on whether or not cores are saturated better than will a moisture meter... if the operator knows their stuff. And there are some good posts on such topics here on the forums.

You might also want to do some reading of boatpoker's page (he's a Surveyor), as there's a lot of good info to soak up on what to look for when boat hunting. Including some great stuff on cores.
All about the boat systems and structure

Also, in boats of the stated age, the weight differences of the two types you're asking about will be fairly negligable. Well, unless you're looking at a racer or boat built to similar standards/tolerances.
But even then, in mid-sized boats & larger, the difference is pretty easy to adjust for or negate, by how you load the boat. Meaning that if you offload everything 2x+ a year. And leave off the non-essentials each time, she'll be lighter regardless. Plus, doing so is a good practice on any boat. With some racers, mono & multihull, even doing it daily.

And generally speaking, a well built foam cored boat will be more impact tolerant than will other types. But again, the quality of construction plays a big role. As does proper design & engineering. And of course, not all foams are equal; far from it.

[paxfish]

Uncivilized - I'm curious about your statement that foam cored boats will be more impact tolerant than cedar - Can you expand on that?

As interest.

So far I found one strip on my 15 year old boat that had water intrusion. It was on a horizontal surface around a fastener hole that hadn't been overdrilled, filled and drilled like the rest of them.

I removed that strip which was wet for maybe .5 meter fore and aft of the fastener. The two adjacent strips were dry. The wood was not rotten, and I found it with a simple tap test.

I layed in a fresh strip, layed some new DB glass and painted to match. I overdrilled the fastener hole, filled with thickened epoxy, drilled for the fitting and bedded it in butyl rubber.

[braveship]

Originally Posted by Redreuben

In a nutshell you plank the hull dry using double headed nails. Where the bilges turn the planks have a natural gap, on flatter areas cut the planks with a bevel to leave a gap. You'll find all the planks have no gap on the inside. Use thin ply or pallet strapping and staples to hold planks fair where necessary.
Screed the whole hull in thickened epoxy to fill the gaps, remove the double headed nails, a rough fair with a long plane and a 7'' pad then glass. DB on outside, uni on inside.

This post deserves an award.

Do you have more information on this? (like photos or youtube videos)

[Redreuben]

Lol, thanks. My time building boats predated internet by a couple of years so no digital. So sorry no records, just the memories [emoji11]