Why Did My Plywood Supplier Go Ballistic on Me??

Welcome here Mr. Pirate!

And bye bye, if all your posts will be of that quality!

 

Strength, yes, but what about the very real possibility of delamination (of the plywood itself)?

I've seen so many catamarans (foam core) delaminated. I went to FL a couple years ago to buy a catamaran and the only one (except a Kelsall) that wasn't delaminating was the one I bought: A very old, solid glass Catalac. I looked at over a dozen boats and every one of them, except the solid glass Catalac, had delamination issues. I hope to avoid that with this catamaran.

What do you make of that issue?

 

In reply to your Question

Sorry for the delay in answering your question. I've been in Ensenada all day trying to fix all the problems a boat builder did on a 27 fishing ponga for a friend of a friend sort of deal so we can splash her on Wednesday.

Ok first of all delamination is more of a fresh water issue than salt water. Delamination happens depending on a wide range of variables.

Hawthorne has built plywood boats with one coat of fiberglass on the outside that are still in service over 40 years later that I captain on fishing charters (salt water). We have experienced bubbles/blisters that we address that are due to the fasteners used at the time which were aluminum not silicon bronze or stainless. So the saltwater turns the aluminum into a white oxide or in short aluminum rust. By drilling out these fasteners and treating with a west system and micro baloons we stay on top of this problem and the hull looks slick even after 40 years.

Understand that a catamaran has many stress points because you have 2 hulls working independently with a platform in between. These stress points will cause stress fractures over time, it's inherent with the design no way around it you'll have to deal with that. These stress fractures allow moisture in which in time will start delam around the fractures. Mono hulls don't have this problem.

So with the right choice of marine plywood, fasteners and the correct curing of your resins you'll be ok. Curing of your resins is critical. Dont mis match make sure all your resins are compatible with each other.

I also recommend that you research Smiths penetrating resins for your plywood prior to fiberglassing. I've had very good success with this.

Hope this helps. Sent some pics of myself, Captain Morgan (yes it my real name) explaining work in Spanish to my foreman. I've been doing this stuff for over 40 years so if you need any other questions answered let me know.

 

After 40 years of boating you could know better.

Well after 40 years of building, you would...............

Regards
Richard

 

I am wondering too, Capt Morgan. How can you say delamination is a freshwater issue? Of the 12+ production, foam core catamarans I looked at a couple of years ago, nearly all were suffering delamination, but none had ever been in fresh water. I'm not understanding this distinction about fresh water.

My understanding is delamination can come from water incursion to the core as well as from mechanical separation of various laminates.

 

In reference to fresh water issue

Lets start with the basics water is water it doesn't matter if its salt or fresh on a foam core. On wood fresh water can start forming dry rot.

If its just wood in salt water it does not grow bacteria and can last longer. Fresh water sets up a bacteria growth in cellulose.

The fresh water I was refering to is from rain water, wash down water etc.

Basically, boats breath. When they are hot as in normal sunlight the surfaces heat up causing any trapped moisture inside the wood or foam core to start gassing off. The gassing off process will push these gasses through to points of penetration ie screws or stress fractures etc. If the gasses cant find a venting hole they will start making surface blisters.

You can't prevent this unless your temperatures are always constant this is simple thermal dynamics.

For instance a hot boat has a cold thunderstorm come over it, thunderstorm unloads downpour cools boat, boat sucks in water fresh as well as salt water on any of its hot surfaces that have been penetrated by screws, stress fractures, impact fractures etc. which is the beginning of the natural deterioration process of any boat.

If your going to be using your boat a lot just stay on top of the maintenance.

 

This is Re Epoxy Sealer

This is for APEX If you haven't tried it don't knock it. Check it out it works.

As far as betting my life on fasteners I'd take stainless over aluminum any day.

Heres the URL Best Regards Captain Morgan

http://www.smithandcompany.org/CPES/index.html

Clear Penetrating Epoxy Sealer™ (CPES™) consists of a tough, flexible resin system in a solvent blend which dissolves the sap, oil and moisture found in wood. The resin system is derived from natural wood resin and develops a chemical adhesive bond to the wood fibers themselves.
The wood is strengthened while allowing normal expansion and contraction with changes in temperature and humidity.
When repairing wood that has mild dry rot, the CPES will migrate along the abnormal porosity which dry rot fungus creates within the wood, as long as it continues to be fed in. Impregnation of wood with CPES changes the cellulose of wood (which fungi and bacteria find tasty and easily digestible) into epoxy-impregnated cellulose which resists further attack by fungi and bacteria while reinforcing the wood, accomplishing restoration.

 

Let's go to the question asked, and not lateral discussions; may I use lauan doorskin made in 2010? The answer is simple: NO. Your provider was right.

The first lauan doorskins were made with waterproof glue (at least those sold in France) and could be used in marine applications if epoxied. The lauan doorskins made now are glued with urea-formol a non waterproof glue, and you have no idea how it will age.

So as Apex pointed out the price of the plywood is a very small fraction of the total cost of the boat so use a plywood made with waterproof glue. Probably you'll use an okoume plywood, as it can be easily found. It's light and easy to bend. The 3 plies must be pratically of equal thickness so you get the ratio 2/3 of the fiber longitudinal and 1/3 perpendicular. That's a thumb rule for multihulls building. You do not need a BS 1088 plywood for this application.

Cylinder mold is a variant of the tortured (or compounded plywood); the method uses rather thin hull skins so a lot of framework is needed to take the stresses.

The cylinder mold is perfectly valuable for multihulls and like any method it has pros and cons. The main con is a clumsy inside with all the stringers.

Mr Hughes is a good architect, with a lot of experience.

 

Thanks Ilan,

captainmorgan

No, it does´nt!
How can one recommend a repair stuff to be used on a newbuild?
This is a completely different application (and a resin with much less strenght, due to the diluent and other additives). And it penetrates the WEAK wood to some extend. It would not go deep into a ply surface or any other solid wood.

The common resins on the market do´nt penetrate wood in deep, thats fact! And they must not, thats another fact.

Regards
Richard

 

You're welcome Richard...I agree with you about the resin.

A good epox for wood boat building have very different requisites compared with the so called rot repair resins (a lot of advertisement claims, some improbable like for some epox pretendly made from wood: it's magical thinking). These resins are very thin and because of the added solvents have no strength nor are waterproof. About the hope of displacing the moisture...let's say that it's more likely that the moisture will be trapped by the hardener of the mix (hardeners are very hydrophile) leading to a weaker resin. And if you don't kill the fungus (hard task) it will start again just close to the resin fixing. When dry rot is visible, you can say that the whole piece of wood has mycelium inside, and that the whole boat is full of spores waiting the good conditions to start again. A prior desinfection is mandatory.

We have already discussed about the requisites of epox for wooden boats in another recent thread. All epoxy resins make a chemical bond with the substrate, as the Nobel price of physics Pierre Gilles de Gennes described it.

The true fixing of a rotten piece of wood is to change it...except if it's a very small spot with no danger of structural integrity.

Besides when you want a thinner resin, the best is to buy one diluted with a REACTIVE SOLVENT, not common solvents like xylene. The second way is to heat; resin applied on a hot surface becomes very thin. There cons also for this method as some woods will release oils and resins when heated...but oily and gummy woods have no place with epox boat building. That is part of the engineering of a epox wooden boat, the choice of the woods.

With epoxy resins it's very simple; keep the solvents for cleaning the tools ... And ask the composition of the stuff you're buying; if you read the words of alcohol, xylene, acetone and other solvents...forget it and buy another resin.

 

Excellent advice. Thank you. I will get the Okoume true marine ply for sure, then.

 

It's a good working boat, simple, rather cheap, and surprisingly durable. No issues.
A small advice from one who made a few boats in compounded plywood and cylinder mold: take the time, make a good straight jig with support legs and tutti quanti, so you'll be able to align the keel joint, the weak point of compounded plywood. An unsupported set of hull panels is a bowl of jelly, so it twists.

Another trick; a "rotating" jig is worth the expense. With a such jig you'll coat with resin while the one of the hull inside is lying flat. And that saves a lot of nervous breakdowns and time. Also precoat and finish all the structural flat panels before installing them.

I think that sanding and coating a panel on a table is easier than doing it in crampy hull inside, the #"¡!&% panel being vertical with the resin running down ...Finishing is the time consuming evil.

Mr Hughes is an able NA, with excellent experience of charter boats (and other also) As he needs to sell plans to make a living, he has tendency to describe the building a bit easier than reality (like all NA selling plans to amateurs).

 

In looking at the cylinder mold build method in detail, I was thinking the same thing about having a good jig. It seems that getting that keel lined up and getting a standard deck jig in place (without legs) would be a nightmare on a 45' boat, even using straps. I was thinking of making a cradle below the hull as well as the deck jig with legs. Good thinking.

Can you be more specific on the "rotating jig?" I'm picturing one from the Gougeon Brothers book where they can rotate an entire hull around in all directions along a horizontal axis that runs fore and aft. Is this the type?

My interactions with Kurt have been (unfortunately for him!) numerous. He took all of my questions in stride and helped me select the right boat from his arsenal of plans. Further, he has helped in my search for a build location and aligned me with a seasoned builder of his boats for "tech support" and some materials sourcing.

The man's reputation is solid and my experience with him has been nothing but good. I had to laugh at the post that said his answers were curt... ha ha. It's true. They are curt, but always helpful. He's actually pretty well know in the States and speaks at all sorts of multihull events. He was in Multihulls magazine a month or two ago. He's known.

 

Thanks for the inputs!

My build, (the 36), will be simpler than a 45 cruising boat, but I do have a special problem with space, and the proper storage of the completed hull panels. Kurt recommends storing them vertically against a wall or something with the curved side down. I have saved the cutouts from the mold panels-- the concave part of the curve, and plan to make a set of vertical braces with them so I can store the panels perpendicular, without giving up any more shop space than I have to. I figure they may also come in handy as cradles at some point.

This guy http://www.dorydesign.com/boat.html tackled that problem my storing his overhead.

Catbuilder, so far I have made up enough panels for one "run". And, so far, I have learned from some mistakes, that it is a very good idea to make a diagram of your panels so that you can keep track of your layout. I wound up labeling each layer,a,b, and c, and numbering each panel a1, a2, a3, etc. This makes it much easier to stagger your vertical panel breaks, and your horizontal breaks as well. (I noticed on the video, that the horizontal scarfs, all lined up. It seems to me that staggered horizontal lines in addition to staggered vertical lines would be better.) Also I put one of those red circles with a mark down the middle (like for "no smoking", etc) on the sides of the panels that will not get any epoxy -- the underside of the first panel, and the topside of the last panel. Hopefully, in the excitement, we wont hit any "sour" notes by painting the wrong side

 

CatBuilder, you're right about the nightmare of aligning correctly a 45 feet hull. Even with a small 18' it can be tricky. Let me the time to make some drawings and to post them, you'll understand immediately about the jig. There is no axis, so it's not exactly the Gougeon's model. It's just a very long "box" you can flip on each side.

I used to make them in steel simple because the pre-painted rolled profiles (mountain? is it the name?) for tin roof, can be welded, bolted and screwed (with the bit-screws for tin roof), are not too heavy, are cheap, are 20 feet long and you can sell them after use. Just straight pieces joined together.
The drawings will be explicit, and my english is too bad for a word description.

Careful planning with good tooling (that includes home made tools like a scarf table) is the key of a successful building. It's worth to spend some time to figure out the whole processus, and define the steps.

There are also a few tricks. For example prefinishing all the flat or almost flat panels that will be used in the boat; bulkheads, benches, cockpit, tables etc...
To save sanding you can use peel-ply (the good one without silicone) strips on the places that will be glued later.
It's impossible to get a good resin coat on corners. So round it, no corners. The stringers, when slim, must be rounded half circle at one side. No more splitting of the corners, easy sanding.
That simpliflies also the notching of the bulkheads: a hole plus 2 straight cuts with the jigsaw or the router. So no corner hard to cut where the concentration of stresses can crack the panel.
There are dozens of tricks useful in boat building...

The beauty of compounded plywood and cylinder mold is that you get smooth fair hulls with little work to finish them. Those who have made polyester sandwich on male mold will understand immediately the meaning of the words smooth and fair while remembering the number of hours sanding the itchy fiberglass, puttying and resanding, re puttying and resanding until getting a fair surface...work that make your life miserable. I remarked that with polyester on male mold you spend more time sanding than actually fiberglassing.