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View Full Version : Cedar Strip boat hull - Fiberglass sheathing or not?



ShoestringMariner
07-20-2014, 11:27 AM
I'm confused as to which way to go with my boat refinishing project. It seems there are two distinctly devided camps when it comes to cedar strip hulls. Some say fiberglass and some say epoxy(?) because the hull and glass sheathing expand and contract at different rates causing eventual delamination.

The boat I'm working on had a failing fiberglass skin up to the mid rail (unsure of the term - wooden strip at the waterline) which I'm in the midst of removing. It's new life will be stored on a trailer under a fitted cover and only used sporadically for outings. I don't plan on finding any rocky shoals, but it will be used for fishing, so some accidental, low speed scrapes or bumps with rocks could occur. The hull has small internal ribs (looks like oak half-rounds) spaced closely at about 3" apart, so would I be correct assuming this boat does not NEED sheathing like a cedar-strip canoe or kayak without ribs does? I've also noticed that the the original builder of these boats are now glassing theirs and using more closely spaced, more substantial ribs (appears to be 1" x 3/8" thick bands) in their builds...so I'm a bit concerned about the overall strength of this hull. On a side note, I will be adding small strip planks on the bottom to create a smooth foot surface. I might make a framework that runs fore-aft so that the flooring grate lifts out in sections. I'd think this could help strengthen the hull also(?)

My plan is/was to paint the bottom section and leave the transom and top half of the hull varnished. I don't want to epoxy paint this thing just to find that fiberglass was the best option all along (I'm assuming you can't fiberglass over epoxy?) If I can avoid glassing this thing, I'll be a happy man, but I want to be fully confident in the integral strength of this boat

photos to show differences;

My boat: http://i1372.photobucket.com/albums/ag337/ShoestringMariner/photo3_zps83ee940e.jpg
Original builder's new model: http://www.gieslerboats.ca/Images/cartop0.jpg

thanks in advance

GregH
07-20-2014, 03:32 PM
First, just to clarify: "fiberglass" is the cloth that is adhered to the hull (and filled/coated) with "epoxy". They are not two separate systems, but rather they are used TOGETHER to form the sheathing. My recommendation would be to remove the existing coatings-whatever it/they might be down to bare wood, and apply a new sheathing of fiberglass cloth AND epoxy. I would suggest that you go to the West Systems web site- there you will find a treasure trove of information and instructions regarding these materials. Good luck!

CundysHarbor
07-20-2014, 03:43 PM
I've built an unsheathed strip planked boat and I'm happy I didn't fiberglass her. On the other hand, for my current build, cold molded sloop, she is glassed to keep the diagonal WRC seams from telegraphing through the paint. As far as advice from West, remember they have an interest in people using their product. Where epoxy is a good option, West is a good source of information. I'm just sayin.
Dave

slug
07-20-2014, 04:46 PM
Hmmm...your boat is not a good candidate for fiberglass cloth sheathing.

To be effective the glass cloth must be on both sides with t he hull skin as the core. Not possible to skin the inside of your boat.

if your boat is in good shape I would use a more traditional approach with some kinda primer and paint on the outside and a sealer like Decks Ole on the inside

ShoestringMariner
07-20-2014, 07:04 PM
Thanks folks.
@GregH, Apologies, I suppose I should have been more specific. I meant epoxy paint only Vs fiberglass sheathing. I looked up the West system but discarded it when I couldn't find any North American distributors..so I really didn't look too deeply...I'll have a closer look

@Slug; I wonder if this is why I can rip sheets of it off in most places? Its as if the fiberglass resin did not adhere to the cedar well if at all

Todd Bradshaw
07-20-2014, 07:44 PM
Whether you can or can't eliminate some form of sheathing will depend on how the plank seams are done. Something has to prevent water from coming in between the planks. There are boats (like guideboats and some canoes) with clench-nailed,beveled plank laps that need nothing more than a coat of varnish to make the hull watertight. In other cases, there are visible gaps between planks and no overlaps at the plank edges (common wood/canvas canoe-style construction). These boats have to have some sort of outer skin (canvas, Dacron or epoxy/fiberglass). Paint is not enough to seal these hulls.


Hmmm...your boat is not a good candidate for fiberglass cloth sheathing.

To be effective the glass cloth must be on both sides with t he hull skin as the core.

Actually, this is false. Some of the canoe companies (like Old Town) have offered their wooden canoes with fiberglass outer skins instead of canvas for better than 40 years. This is my 1972 Old Town, skinned outside with WEST Epoxy and six ounce fiberglass. The inside has nothing more than varnish. Looks rather possible to me, though like any construction method, it has it's good points and its compromizes. If you do a good job of interior maintenance, it holds up pretty well.

http://webpages.charter.net/tbradshaw/Sails%20and%20Plans/guide2-a01.jpg

If the planks do have gaps, an epoxy/fiberglass or filled canvas or Dacron skin up to the rubrail would be one way to close them. The reason your original skin failed is likely because it was done using polyester resin, not epoxy resin. This is quite common on early hulls with polyester/fiberglass skins. The stuff just never stuck to wood very well, and still doesn't. Epoxy resin has taken over that job and works drastically better.

There are also boats with thick enough planking that they can be traditionally calked between planks, and even some with glued overlapping plank rabbits on the edges (most of the old Star sailboats were built this way - with everything glued-up tight, the planking tended to check frequently and fixing paint or wood cracks on the topsides and decks was a weekly endeavor.

Without knowing more about how your boat is planked, it's impossible to say what methods of sealing it up might work well.

ShoestringMariner
07-20-2014, 09:03 PM
Thanks Todd. The joints are the rabbit type. A double rabbit if you will...both edges have a square notch cut in, like a boxed Z, though ever so slightly. The strips might be about 1/4" to 3/8" thick, the overlap perhaps 1/16" thick x 3/16" to 1/4" deep. There seems to be a visible hairline crack between joints, assuming from the wood drying out. Wondering if epoxy paint might flow in well.


The Iphone photos are not great, but you might be able to make out the overlap joint details - (Planning on moving the transom forward a few inches and shaving off the punky wood)
http://i1372.photobucket.com/albums/ag337/ShoestringMariner/photo31_zps841c7173.jpg
http://i1372.photobucket.com/albums/ag337/ShoestringMariner/photo11_zps99f5a901.jpg

Todd Bradshaw
07-20-2014, 10:41 PM
First of all, lose the concept of "Epoxy Paint". Paint isn't epoxy, and epoxy isn't paint. "Epoxy Paint" is primarily marketing hype to make people believe that the paint they are buying is tougher than regular enamel or urethanes. It generally is not (at least not enough to matter) and the fact that it may actually contain some epoxy doesn't give it the adhesion, hardness, characteristics or sealing power of real epoxy resins. Nothing that air-dries or contains evaporating solvents will seal like genuine, two-part, 100% solids epoxy resin. If all you're seeing are hairline cracks on lapped joint edges though, I'd be tempted to strip the old fiberglass, do some sanding to clean things up, and follow that with primer and a good marine enamel.

ShoestringMariner
07-21-2014, 04:48 PM
First of all, lose the concept of "Epoxy Paint". Paint isn't epoxy, and epoxy isn't paint. "Epoxy Paint" is primarily marketing hype to make people believe that the paint they are buying is tougher than regular enamel or urethanes. It generally is not (at least not enough to matter) and the fact that it may actually contain some epoxy doesn't give it the adhesion, hardness, characteristics or sealing power of real epoxy resins. Nothing that air-dries or contains evaporating solvents will seal like genuine, two-part, 100% solids epoxy resin. If all you're seeing are hairline cracks on lapped joint edges though, I'd be tempted to strip the old fiberglass, do some sanding to clean things up, and follow that with primer and a good marine enamel.

Thank you. I was referring to a 2 part epoxy, not an air dry enamel, however I did not know there was that misconception. I've sprayed 2 part epoxies a few times, sometimes 50/50, some 75/25. I *thought* that it was still considered a "paint" or coating, even if it flowed on like glue. As for the technical properties of what I was using or how they stood up in the field..not a clue.

I think I'm going to give the marine enamel a shake and see how that works.

Todd Bradshaw
07-22-2014, 02:16 PM
If the cracking is minimal, it's probably worth a try. If it continues to be an annoyance or you plan to get a lot of abrasion it wouldn't be too tough to sand it off later and add a layer or two of epoxy/fiberglass between the wood up to the rubrail and then repaint.

slug
07-22-2014, 02:30 PM
First of all, lose the concept of "Epoxy Paint". Paint isn't epoxy, and epoxy isn't paint. "Epoxy Paint" is primarily marketing hype to make people believe that the paint they are buying is tougher than regular enamel or urethanes. It generally is not (at least not enough to matter) and the fact that it may actually contain some epoxy doesn't give it the adhesion, hardness, characteristics or sealing power of real epoxy resins. Nothing that air-dries or contains evaporating solvents will seal like genuine, two-part, 100% solids epoxy resin. If all you're seeing are hairline cracks on lapped joint edges though, I'd be tempted to strip the old fiberglass, do some sanding to clean things up, and follow that with primer and a good marine enamel.


Huh ?