When I was sanding the daggerboard for my NE Dory after putting on a coat of glass cloth soaked in epoxy, I was frustrated because by the time I got it smooth I'd cut through the cloth onto bare wood in several places. I'm wondering if applying several coats of Penetrating Epoxy might eliminate worries about doing this, since it won't be bare wood I've sanded down to, but rather wood soaked in Penetrating Epoxy. Anybody have experience with this?
I'm not sure sure why you would even need to cover the board with cloth, unless to strenghten it or provide some protection. That being said, I personally wouldn't worry too much about protecting a daggerboard as you are always removing it from the case and can inspect it easily The inside of the case is the area, that in my opinion, should get the extra protection as it will likely never see a paint/ epoxy brush again...
A couple of thoughts:
First, I would probably want to perfect sanding a fiberglassed part while being careful to not sand through. This is important. We often turn to the random orbital sander when in fact we should be hand sanding because power tools, although soothing to use, can be too aggressive in certain applications. There's an inherent nobility in using hand tools when building wooden boats.
Second, if you're not going to somehow patch or recover the fiberglassed area/part, then soaking it with penetrating epoxy would have some benefit, but let's look at why you're glassing the daggerboard. It's primarily to give it lateral stability/strength so it doesn't break off at the bottom of the daggerboard slot when it's keeping you from sailing sideways. It's also to help fight all the wear and tear from dropping the daggerboard into the case and pulling it out a gazillion times over the life of the boat. Penetrating epoxy won't help with wear and tear like fiberglass will. With that being said, most of the daggerboard is underwater while underway, so penetrating epoxy will definitely help with intrusion, delamination, etc. especially where wear and tear breaches the glass/epoxy surface.
Finally, fiberglass will also help with the fact that the leading edge/bottom of the daggerboard takes a lot of abuse during the beaching process if you're not quick enough. Here in the PNW, we have rocky beaches that are very hard on daggerboards and rudders if you're not careful and nobody can be 100% crunch free. I usually state "We're here!" when that happens...
As a side note, I used graphite epoxy as the top coat(s) for my daggerboard to help resist abrasion. I didn't think about doing the inside of the daggerboard case until it was too late.
Hello All
Thank you so much for all your kind replies on this thread - it is invaluable for a first-time builder like me.
On the balance of things I'm probably going to get some. There is, as far as I can make out, only one supplier here in the UK - selling only 2 sizes (0.95 ltr & 1.9ltr) in either warm or cold
My boat is a lapstrake Sassafras 14 (yep, the discontinued one), so I'll be routing rebates into 4mm ply. My plan is to use the CPES on the edges & joints (rebates) first, then assemble the boat loosely - then once it is square & true CPES the rest of the boat.
My plan is that every side/edge of every panel (even the bulkheads, gunwales & decks) are treated with CPES prior to epoxying.
WEST system is available here but I'm going to be using Petram Epoxy which has been used successfully by many boat builders here in the UK, both with fibreglass as well as more exotic materials
From all your replies, I know that CPES isn't very friendly, so I'll be using a full face respirator with VOC cartridges and disposable clothing (paper suits), and gloves, obviously.
As far as possible, application will be outdoors for the CPES using the Cold mix
Once treated, the boat will be sheathed in 6oz (163 gram) plain weave fabric externally on boards 1 & 2. I am still playing with the idea of sheathing boards 3 & 4 with 1.5oz (44 gram) fabric.
My chosen finish (until I change my mind again ....) is a cream painted exterior and varnished interior
For anyone who has built a Sassafras (or similar) I'd be very interested to know how much resin you used in your build - metric or imperial measurements, I'm 'fluent' in both
Thank you again for sharing your experience with me
Kind regards, Tony
Update on an old thread:
I used West Marine's Penetrating Epoxy on various parts of my PMD boat hull. I discovered much to my dismay that for some reason it doesn't "play well" with regular epoxy.
After I stitched my hull together and filled the lap V's with thickened epoxy, I sanded all of the exposed corners with a roundover to reduce issues with impact on a sharp corners. This exposed some of the core layers of the marine grade plywood and edge/end grain, so I soaked all of those seams with CPES.
Upon curing, it did a weird "beading" up on the previously epoxied planks. Upon further application of additional layers of epoxy, the "beading" continued to show through, even after sanding previous layers. It's as if there's some sort of wax or something that keeps subsequent layers from adhering properly.
With the only slightly comforting thought that "No good deed goes unpunished", I can categorically state based on empirical evidence that at least that brand of CPES is not a good idea to use in your boat building process.
Yeah, I’m not surprised . CPES has or had a high percentage of solvent. I tried it on deteriorated wood and was unimpressed.