To encapsulate or not

[tonydezoc]

As part of the preparations for building a Caledonia yawl in the new year I decided to buy a couple of books on clinker ply boatbuilding to “bone up” on any new developments in the field, Clinker Plywood Boatbuilding Manual by Iain Oughtred and Glued-Lapstrake Wooden Boats by John Brooks and Ruth Ann Hill. I was surprised to read that while both books deal with epoxy as a structural glue neither book advocates epoxy encapsulation . I started using epoxy in the late 80’s and bought the Gougeon brothers book at the time and have followed the path of encapsulation ever since without any mishap (that I know of anyway) and although most boatbuilding that I have done has been traditional this still calls for epoxy work occasionally, coachroofs decks etc. Oughtred says that he has never coated a boat with epoxy and Brooks/Hill say they don’t recommend it, and as they build boats that way professionally and their book is published through Woodenboat this gives a lot of credence to their opinions and I’m certainly not going to argue with Oughtred on this matter, but this method does run contrary to what I have believed and done for over 20 years. I have heard people say how encapsulation can trap water in planks and lead to rot but I used to put that down to poor workmanship and I could cite plenty of examples of shoddy work leading to problems in traditional boatbuilding aswell. Having only recently joined the forum and being impressed with the range of advice I have read on boatbuilding I would be interested in hearing any opinions/experiences people might have on this matter.
Since I’m posting this I thought I might post another, hypothetical, question at the same time. Over the years I have used brown sikaflex as an adhesive for exterior work, fixing cabinsides, cockpit furniture etc. along with mechanical fastenings, on the understanding that it would be able to flex and move with the wood and maintain its bond, and I have often wondered if Sika or a similar product could be used instead of epoxy for clinker ply construction, does anyone know of any examples of this or reasons why it wouldn’t work.
Tony.

[Bruce Hooke]

This has come up before and you may be able to find some of the past threads using the search function. I think you'll find that there are two camps on the encapsulation issue, and both camps can claim extremely knowledgeable and experienced boatbuilders on their side. Both sides can also show you boats built their way that have lasted for decades. So, you are probably best off just trying to understand as much as you can about the advantages of each method and then make your own choice. I said just "advantages" because it my opinion it is very hard to get honest input about the disadvantages. Each side will try to tell you that the other way is a guaranteed road to disaster, which is, of course, balderdash given the history of good boats both sides can point to.

[Ian McColgin]

Hello. My name is Ian and I am an epoxyholic.

In my experience over the last thirty three years the encapsulizations I've seen fail were caused by too thick as in viscous an application. If the epoxy starts traveling in, the wood, whether ply or dimensional, will last longer. When I started, WEST did that best of things I found. But WEST is basicly a glue. CPES is not a glue, but a sealer and it really travels, even across grain.

Two identical gloster gulls made in the mid-80's offer some evidence. One was sealed inside and out with CPES and then painted with regular topside paint. The other was primed and painted the normal way. Both boats live on the beach winter and summer. The latter was maintained with far more labor, and needed it, but for the past few years has show signs of plywood deterioration at the chines. The CPES'd boat continues strong.

Leeward, the dory I built in the early '70's, was WEST sealed. She withstood hard use, abuse, occasional neglect, damage that was repaired, and lived outdoors all her life. The useful life in her ended three years ago when water intrusion around the centerboard trunk swelled when it froze and rot in the bottom at last became more trouble to fix than building a whole new boat. Three decades is not a bad go for non-marine plywood, but had I known of CPES I think she'd have done better.

One thing to remember about epoxy encapsulation is that epoxy is vapor permiable. It's well to use finishes that don't trap vapor between themselves and the epoxy/wood as this will at the least weaken the bond with the finish. If it traps enough moisture, it could cause sweet water build-up further in the wood than the epoxy barrior. CPES's solvents travel amazingly deeply and should prevent that moisture from being a breeding ground for rot, but it's still not desirable.

I love WEST as a glue. Despite it's brittleness in thick build up, it will flex with wood when used as a glue. However, the brittleness has always alarmed me when using WEST as a surface finish, whether on spars or decks. On spars I go CPES and then varnish. On decks, coachhouses, hulls and such I like GluvIt, with or without glass, as that has some serious flexability and tenacious leak stopping power.

Please note that I'm not a pro and for that reason have limited my arsenal of goos to a small number that I get to know well. I'm sure real pros can get somewhat better performance from a greater range of products using them selectivly. For me, a broad range of acceptable performance trumps trickier decisions which I've not the background to make.

[JimD]

I’m certainly not going to argue with Oughtred on this matter

Oh, by all means, argue with him. Lots of other people do.

[Stu Fyfe]

I like the best of both. On my 1982 strip plank, the builder used epoxy and cloth on the outside and epoxy without cloth on the inside. As I continue the upkeep of her, I find myself scraping away the inside epoxy as it develops cracks and just using CPES. Am I wrong in thinking that the CPES will provide some sealing without letting water get trapped as epoxy would? Does epoxy and cloth on the outside and CPES on the inside make sense to anybody else?

[Thorne]

Like Ian, I'm a fan of CPES as a primer/sealer, but have much less boatbuilding experience.

As for an alternative to epoxy for the lapestrake, that is getting much riskier == you'd be betting the farm...er...boat on an unproved construction material/method.

We **are** starting to see PL Premium tube glue being used instead of epoxy in some applications in some small boat designs -- several are listed in the Duckworks plans pages. That is not to say that the boats in question don't use epoxy at all, but some joints or fillets are being made with PL Premium rather than epoxy.

PL Premium sets up fairly hard -- not quite sandable in my experience but close -- so it is not the same as a flexi sealant like Sitkaflex or Vulkem116. Note the difference between glues like epoxy and PL Premium, and sealants like Sitkaflex and Vulkem116: the former stick things together (primarily) and the latter seal working/flexing joints or gaps (primarily).

I've done a little bit of testing with PL Premium and so far, so good. But when I need to edge-glue oak planks for a rudder or something that completely depends on the glue to hold, I still stick (grin) with epoxy.

[Cuyahoga Chuck]

The basic premis is this. An unbroken coating of epoxy on all sides of a piece of wood will limit the intrusion of air and water to levels that wood eating microbes cannot tolerate. Since epoxy is also a glue it adheres to wood much better than conventional surface treatments.
If the epoxy barrier is broken and microbes get in, damage can be limited if the wood is dried sufficiently to allow the entry point(s) to be re-epoxied. The microbes are entombed and will die off. The amount of damage depends on the time interval before the remedy is applied.
The glue guy on this site is Bob Smalzer. Search out his glue postings. What I got from him is that epoxy is a powerful waterproof glue. It has the broadest range of application of any glue. It can be used over itself and most other glues. That can't be said of competitive glues.
The idea of using flexible glues has also been chewed on numerous times. Their failing seems to be "creep". A glue joint under continuous stress, like a plank flexed into place, or enduring flexation in service, cannot be maintained if the glue can move.
I may have not gotten everything right. Take some time and review Smalzer's postings on the subject.

[Ian McColgin]

CPES is a sealer, not a glue. As I mentioned above, thinned out glue epoxies do not appear to work in the same way that a sealer like CPES does.

The problem among the propriataries, for we non-chemists, is that they don't always make their claims crystal clear. The GoogeBros used to say the S in WEST was "saturation" and we still hear from propriataries competing Smith that CPES is just a pile of solvents, but Smith claims there's more to it - just won't say exactly what. In my experience, Smith is right CPES is a sealer, not a glue. CPES is not just a thinned version of the glue he also makes from many of the same materials.

Glues lie on the surface bonding with the first very few molecules of wood fiber, depending on surface roughness. CPES will penetrate a visible depth even on surfaces cleaned with a cabinet scraper.

G'luck

[Charles Burgess]

Encapsulation usually indicates the use of fiberglass cloth. If your Caledonia yawl will sit for extended periods in water, then DO NOT encapsulate her hull. If she will mostly sit on a tailer at your home, then encapsulation will work very well (be sure to make a boat cover to keep rain out of her while sitting on a trailer.)

Epoxy is a polymer, thus is vapor and water permeable, albeit at a very slow rate. If the hull sits and soaks in water for more than a week, water will get through. Unless the hull is planked with teak, the wood will move enough to break the epoxy bond...causing all sorts of problems.

[pipefitter]

There is many other considerations as well. The varying results could start with wide variability of wood selections. Buying cheaper, varying grain plywoods for example will have as many different results. I think if most people chose the more stable surfaces of the finer grain cedar/luan type plywoods, that absorb glue more consistently across their entire surface, would see better and more predictable results. Same with painting. If parts of the wood are drinking up the paint and other parts of the grain are not, you can pretty much tell how and why the failures will follow. Douglas fir marine ply is a great example and is a poor choice for epoxy encapsulation or paint only, if you ask me. The raised, harder grain will be the first place paint flakes off and I would expect the same to be true for epoxy.

[Thorne]

I'll admit that I'd seriously consider using CPES, then epoxy and fiberglass or Dynel on the bottom and garboard strake for a CY.

My boating seems to often take me to rocky areas, and beaching on even fairly clear shores can be rough due to powerboat wakes. Currently the solid fir plank sacrificial bottom protects my bottom planks, but the garboard strake keeps getting gouged and scraped.

With my solid wood fir planks these gouges are not a real problem -- just sand them out, coat with CPES, then epoxy fairing compound, then paint. But even with quality marine ply, breaking that external skin is very bad juju and can allow water into the interior of the ply hull.

http://www.luckhardt.com/mendo6.jpg

[Bruce Hooke]

Encapsulation usually indicates the use of fiberglass cloth. If your Caledonia yawl will sit for extended periods in water, then DO NOT encapsulate her hull. If she will mostly sit on a tailer at your home, then encapsulation will work very well (be sure to make a boat cover to keep rain out of her while sitting on a trailer.)

Epoxy is a polymer, thus is vapor and water permeable, albeit at a very slow rate. If the hull sits and soaks in water for more than a week, water will get through. Unless the hull is planked with teak, the wood will move enough to break the epoxy bond...causing all sorts of problems.

This is the sort of statement that always leaves me scratching my head given the number of highly successful and durable boats built using the encapsulation method, including many boats that spend months at a time in the water.

[Todd Bradshaw]

You mean there's bad information floating around out there on the internet? Who would'a thunk it? Sure glad I didn't know this kind of stuff when I epoxy encapsulated several of my own boats and left them on moorings for six months at a time.....

[Ian McColgin]

Granuaile's seams were reefed and routered, soft wood splines epoxied in and she was then was encapsulated inside and out by the prevous owner somewhere in the early '70's. No glass. She lived in the water year round under his and my ownership. The system worked quite well for the over thirty years before a northeaster and a breakwater ended her life.

The Wianno Sr Ardent was sheathed with wood and epoxy and is doing well.

I've seen lots of older boats where attempts at thinnish glassing (not the Viatsas me.thod) were attempted and that failed and lots of examples where glass set in epoxy on new plywood worked quite well and lots of examples where simple CPES under the final finish but no glass worked well on dimensional and plywood.

The only general conclusion I have is that glass however set on an older conventionally planked boat is doom and problematic at best over older, strip or tightseam.

G'luck.

[paladin]

Glass is rigid......Vectra or Xynole fabrics will move with the wood if a minutely elastic epoxy is used.....damn.....you mean my boat will break the skin and start decaying if I leave it in the water for several months..........? (it's now 20 years old and hull is still just as fair......)

[Todd Bradshaw]

As for slathering a Caledonia yawl inside and out with 10 mils of epoxy (which is what it takes and about 5-6, thin, rolled on coats by the way, if you allow for final sanding) it strikes me as though it would be a royal pain in the butt to do and most likely isn't worth the effort. Epoxy doesn't go on particularly flat and neat and if you want it to look decent, you're going to be doing a tremendous amount of hard sanding in places that aren't easy to sand just to get a decent surface to paint or varnish over.

I could probably see fiberglass-sheathing the garboards if you plan to do a lot of beaching on rocks, but not epoxy-coating the entire boat. Unless you're truly planning on abusing it, it just doesn't need it. In normal use, with reasonable care, maintenance, decent off-season storage and timely repairs when needed, you will probably never need to do much more than just touch-up the paint.

I would seriously consider using CPES under the finish in this case as a sealer/primer (as at least this time it's a use that the stuff is actually made for) and then add the paint or varnish of your choice. Plus, I think the boat will look better this way. Epoxy coating gives you three basic choices - a rather drippy surface that's been painted over and looks like crap, a carefully sanded, smooth as a baby's butt surface that, once painted over, tends to look a lot like fiberglass if you're a good painter or three, varnished epoxy coating - which tends to look so thick that it looks fake, like plastic. The CPES sealer might extend the life of your paint without adding any kind of thick-ish buildup that needs to be sanded down using a hunk of sandpaper wrapped around a little block of wood.

[tonydezoc]

I've never worked in the US, and am not sure what CPES is, in the UK and Ireland we generally used WEST system which I always found to be very thick and hard to spread, especially when the temp is a bit low. I now live in Australia and am using International evindure-epiglass which I like a whole lot more and I feel penetrates a whole lot better. I wasn't planning to actually glass at all, just several coats of the aforementioned and then paint. The boat will live on a trailer most of the time. My main worry with ply is not so much water getting into scratches and dings as this can be dealt with as normal maintenance, but the tendency of the edges/endgrain of boards to soak up water like a thirsty camel and I have always felt more secure with this area having a healthy amount of epoxy on it to prevent penetration and help protect against minor scuffs.

[Bruce Hooke]

I basically agree with what Todd said. I do just want to note that if someone does want to encapsulate the plywood on a small boat, one way to go at it is to flow-coat the plywood while it is still in a large sheets and then cut it up into parts. Flow-coating (see the Gougeon Brother's book) is a very effective way of building up a nice smooth coat of epoxy in a hurry. Yes, you waste some epoxy by coating wood you won't end up using, but you save a lot of time. You do, of course, have to go back and deal with the cut edges after the boat is built. One down side of this approach is that it will be a bit more work to plane any laps and similar things, if the plans call for that, because you will be planning epoxy and wood, rather than just wood. However, even without the epoxy you would still have the glue lines in the plywood, which are also harder to plane than wood.

I do also want to note that the Gougeon brothers seem to think that two coats of their epoxy is sufficient, and advise applying three coats to allow for losses resulting from sanding.

All of that said, I agree that for many boats full epoxy encapsulation does not really make sense.

[Bruce Hooke]

CPES stands for Clear Penetrating Epoxy Sealer and I believe it is available in Australia.

[Todd Bradshaw]

Epoxy-coating just the plank edges might not be all that bad. I suppose a small brush and about three coats of resin followed by a little block-sanding to clean it up might be in order. This would be drastically less work than trying to coat the entire hull with resin and would hit the potential problem areas. Back when I built new floor panels for my Avon Rover sportboat I coated the edges of the Brutnzeel plywood panels with WEST epoxy and then just varnished the tops and bottoms and they held up well with no signs of water intrusion.

CPES is a brand of sealer containing epoxy resin, diluted with a lot of solvent. It's quite thin and soaks in well. The solvent evaporates out leaving at least some epoxy deeper down than it would be in a normal resin application. Believers generally think it's able to improve the sealing capabilities, bond and life span of paints and varnishes applied over it.

You can read what Gougeons had to say about diluting WEST epoxy here:
http://www.epoxyworks.com/indexprojects.html
(click on "epoxy techniques and materials" then scroll well down in the topics listed to "Thinning West System Epoxy".

[Dave Gray]

"As for slathering a Caledonia yawl inside and out with 10 mils of epoxy (which is what it takes and about 5-6, thin, rolled on coats by the way, if you allow for final sanding) it strikes me as though it would be a royal pain in the butt to do and most likely isn't worth the effort. Epoxy doesn't go on particularly flat and neat and if you want it to look decent, you're going to be doing a tremendous amount of hard sanding in places that aren't easy to sand just to get a decent surface to paint or varnish over."

I can attest to the above.

[Charles Burgess]

This is the sort of statement that always leaves me scratching my head given the number of highly successful and durable boats built using the encapsulation method, including many boats that spend months at a time in the water.

I have seen countless boats that were not successful nor durable in the long run. It is usually a few owners down the road before problems become evident...usually in the form of rot just under the FRP skin. I am speaking of just an outer skin of FRP encapsulating the hull.

If you also encapsulate the inside as well as the outside...well things are much better - although you will have problems with oak and similar woods that do not work well with epoxy or nearly any resin. Encapsulating the hull inside and outside will result in a ton of sanding while wearing a respirator-mask.

[Bruce Hooke]

Thanks for the explanation, Charles. Coating on only the outside could, I think, be labeled a "non-standard" procedure, and I can see why it would lead to problems.

I certainly agree that coating on both sides can be a lot of work. There are ways to reduce the amount of work, but to some degree this depends on the type of construction. In any case, the person in charge of the project should weigh the costs and benefits and make their choice...

[tonydezoc]

Well this thread is going well, my only disappointment is that it hasn’t resulted in the bunfight predicted by Bruce at the start, but it has been edifying. As I said my knowledge of epoxies has been shaped by the Googe bros book and also by about 10 years of dealing with the same WEST rep when I lived in the UK, whose advice was always biased naturally, but was consistent and came from the horses mouth so I felt I could trust their product and thereby trust the standard of any job using the product. If you put your name to a job it is best that you are sure about the way it is done regardless of whether someone else thinks they know a quicker-cheaper-faster way. In the light of my newly acquired books plus comments in this thread the plan to coat and sand(flatten) each plank before fitting(much easier than after the boat is built) does seem like a belt and braces approach and I may look at changing this and instead using several coats of everdure ( Internationals equivalent to cpes) and paint but still epoxy plank edges. I recently had to prepare some veneered ply panels for doors and after 3 coats of everdure although the grain of the face veneers seemed to have filled and stopped absorbing the edges continued to soak the stuff up, after 7 coats on the edge grain I mixed some epoxy and coated them with that instead. I think if I go down that path I’ll do the same with the planks.

[Thorne]

Bunfight, eh?

How about this...here are some photos of a friend's boat built from doorskins, fiberglassed inside and out. So far, so good.

Boat is not left in the water very long, but spends the odd weekend pulled up on the beach and fairly damp -- all without any damage so far.

Reason given for using doorskins was budgetary, I guess he had access to free epoxy and glass, as otherwise you could use better marine ply at about the same cost.

http://www.luckhardt.com/holly_bough.jpg
http://www.luckhardt.com/DSCN6467.jpg

http://www.luckhardt.com/DSCN6438.jpg

http://www.luckhardt.com/stnlgn2/stnlgn2-Images/14.jpg

[tonydezoc]

thats a fine lookin boat, my complements to the chef,are those planks ply from doors,were they glassed individually, how are the timbers fixed

[neilm]

http://neilmoomey.com/trips/2007_Port_Townsend/IMG_2207_600.jpg

I have a similar delima. I am currently building this boat, a CLC Skerry. The instructions call for fiberglass and epoxy on the floor and garboard and epoxy coating only above that. Do I follow the instructions or skip the epoxy above the garboards and just use paint and primer? The planking is Okoume. Thwarts and decks are Sapele.

Neil

[Thorne]

Tony -

The planks are doorskins, those thin sheets of ply sold in hardware stores. They were glassed in place after building, not pre-glassed (although that is sure a neat trick!). Boat fastened fairly traditionally otherwise, but planks are just glued and glassed, not riveted.

Here are some building photos -
http://www.amberpost.com/sail/HB/index.html

Neil - Can't say from experience, but I'd be tempted to build to the plan, or use CPES as a primer at the very least.

[paladin]

Tonydzoc.....CPES is available in Oz and NZ...as are M.A.S. epoxies.....M.A.S. are much lower viscosity and will saturate faster, and is especially good if you use Vectra or Xynole fabrics, which are lighter and thinner (but more abrasion resistant) than Fiberglas.
Depending on the size of your boat, and the individual "planks" if using ply planks...a neat trick is to saw a piece of formica down the middle lengthwise, fix them end to end, wax liberally with Johnsons paste wax (floor wax), wipe off, paint with PVA, then paint your ply planks with CPES, let set for 24-48 hours, then use xynole-epoxy on it and while wet turn it face down on the formica, set some cinder blocks or sandbag weights on it, and allo to set overnight. The epoxy goes off leaving a fine glass finish on the planks. Then, attach the planks in the manner that you desire to finish the boat.

[tonydezoc]

Paladin thats an interesting idea, I've done something similar before working with GRP but never thought to try it with epoxy, have you tried this yourself? I have several questions
1 what exactly is the purpose of the pva
2 is there any possibility of a reaction between the wax-pva and the epoxy
3 is Q2 the answer to Q1
4 assuming you use saturated cloth on the outside of the plank, then the inside will need to be epoxied too? would this method work for neat epoxy on the inside to minimise pooling and therefore sanding, or would you use cloth on the inside too
5 how much would this stiffen the plank, for instance would a garboard be more difficult to twist into place
6 with a plank thats 18' long being turned over with wet glass/cloth on one side you can expect a bit of twisting, any danger of the cloth coming unstuck
and (whew) finally 7 when doing several planks, what needs to be done to the formica to prevent sticking, re waxing, on recoating with pva, or just wiping down? Tony.

[tonydezoc]

one more question, would peelply work with that setup. T

[Todd Bradshaw]

Chuck and I seem to be butting heads lately, but I think such a plan is a mistake. The PVA, by the way, is a mold release to keep the epoxy from sticking to the Formica. The CPES adds nothing under the epoxy that the epoxy can't do for itself and isn't needed. I would also be very careful pre-sheathing the outside of your planking as it will stiffen it greatly when you go to bend and twist the planks around the forms. The reason is that you will be putting the fiberglass in tension (or whatever you use, fiberglass being substantially lighter than most of the acrylic/polyester types due to their increased resin absorption). As you go to bend the plank over the forms, you would essentially be trying to stretch the sheathing, and over an 18' long plank the amount that you are trying to stretch something on the outside of a plank can be fairly substantial. Composites don't "do" stretching very well. It tends to fracture them internally. A layer of fiberglass or other resin-saturated fabric that is 18' long when applied and cured, does not later grow to 18' 1" without some damage happening down in the weave and weakening it. This tension will also increase the sheer loads, stressing the bond between the sheathing and the plank, which is not a great formula for getting your composite to stay stuck to the plank without delaminating. Add to this the purely physical problem that you will have made a pretty substantial change in the bendability and twistability of the plank when you go to bend it into place and the external pre-sheathing becomes a pretty risky procedure. If you did want to try something like this, thinness and an absolute minimum of excess, unsupported resin in the cloth or filling the weave (stiff and brittle) is critical (hence the bricks and there better be a lot of them and evenly spaced - vacuum-bagging would probably be better, but requires more equipment.

Pre-glassing the inside of the planks is a bit of a different story and might certainly be a possibility. When you go to bend-on a plank, the fiberglass (or whatever) will be in compression, rather than in tension, and it's also on the inside of the curve (a shorter distance). It doesn't have to move or distort much at all to make the bend. The small amount that it needs to compress both stresses the layup much less and stiffens the plank much less as you're trying to get it to bend around the forms. Here again, you do want a fiber-rich mix with the cloth down tight on the wood and a minimum of excess resin, but it is a much easier and less-stressful bending job that pre-glassing the outside surface would be.

When I built this stripper, I pre-glassed the insides of the side and bottom panels flat on the bench. After curing, I added the little stiffener ribs then bent the panels over the forms, tacked them together and then glassed the outside of the entire boat. That way, the outer glass was applied and cured 'boat-shaped" rather than being highly stressed just by forcing it into a boat shape. Then it was flipped over and the seams inside were taped. Had I tried to glass the outside ahead of time, my clear finish would have also contained lots of tiny white flecks down inside the cloth weave where the fiberglass was stretched and fractured during the bending process.

http://webpages.charter.net/tbradshaw/Sail%20photos/Drift%20A.jpg
http://webpages.charter.net/tbradshaw/Sail%20photos/Drift%20B.jpg
http://webpages.charter.net/tbradshaw/Sail%20photos/Drift%20C.jpg
http://webpages.charter.net/tbradshaw/drift4%20copy.jpg