Thread: Primary vs. Secondary Bonding

I asked PAR about this a few days ago. In the building subforum ... the thread about "what should I epoxy"

Michael

Originally Posted by Boatmik

I asked PAR about this a few days ago. In the building subforum ... the thread about "what should I epoxy"

Michael

Mik, Clint's a yank, he's probably not used to being 'handballed'

Richard

for the non Oztralians, our weird local game involves passing the ball from one player to another via the 'handball' whereupon you punch the ball with one one hand while supporting it on the other. In the local vernacular, refusing to answer a question by referring it elsewhere is called being 'handballed'

Howdy,

My belief is that it is perfectly fine from both experience and observation of others.

But was PARTICULARLY interested in Paul's (PAR's) experience because he has done so much building over such a long time and also has the chance to see his work again through the years.

He is also a damn fine analyst with few biases as he has used most types of glue and chooses what does the job ... as perfectly as possible. I've learned a great deal from him.

Yes ... I handballed it

G´day all!
Being at home, possibly swine flu, I guess there´s not much more to do than offer a link,
G'luck with PAR's, Daddles' and Mik's advice...
Cheers,
PDJ

P = Pig
D = Disease
J = ?

Hope you are hale and hearty soon.

If you are providing links it can't be toooo bad. Which is great.

So from the other thread

Originally Posted by PAR

Mechanical bonds on a build like this would be nearly as good, so precoating serves well.

In areas where I'm concerned about a good wood to wood, wet bond, I'll take a grinder and plow through the epoxy coating, down to raw wood and butter up the contact areas. In a glue and screw build (like this) it's less important as it's not a true taped seam job.

I use a couple of different flexibility squeegees to do curved surfaces. Brushing is painfully slow and wasteful. Rolling and tipping leaves a nice, uniform coating, but I always feel guilty about the few ounces of goo that the roller needs to wet itself out.

I don't light candles, sing chants, click my heels or bow to the west when I use goo (acolyte), though on occasion, I have prayed things would kick off and set before the rain sets in.

In short, I'd coat chines and stringers before hand just so I don't have to contort myself in some odd position trying to do so in place on the boat. Often when a piece is installed, there remain places you just can't reach with a brush, roller or other goo applying tool. I've had occasions where I wished I had an "epoxy bomb" (low yield of course) that I could place inside and area, let it go off, knowing it would coat every nook and cranny.

Originally Posted by PAR

Ideally, you want chemical bonds on everything, but this isn't practical for the average person, without careful planning.

It does no harm to coat, say the inside of a joint, then come back later and coat the rest of the part. In fact, it's often the only way to really handle things.

Staging and planning is part of the fundamental skills in boat building, which is problem solving. The first few times you use epoxy, you're going to get it all over everything, you're not going to be ready for the goo to hit the fan, so to speak and hopefully you'll manage to get the task done, before the pot smokes. After a few attempts, you'll realize that you need all your clamps and tools handy, not scattered on a work bench and that you might want to think about protecting these clamps or tools from the goo that's surely going to be on your hands when you grab it. Eventually, depending on how hard headed you are (ask your wife, she'll give you an honest acessment) you'll learn to line up your tools near the place you'll be using epoxy, have the cordless drill in a plastic sack to prevent you from having to chip off a half a gallon of dried goo, just so you can pull the trigger again, etc. This is fore thought and planning, a clear indication of problem solving.

In short, you'll have to glue things, so glue them. If the piece is precoated, then scuff up the area that will contact the joint and apply your goo. If the piece isn't precoated, then apply the goo to the joint and worry about finishing the rest of it later, when you have time., Besides, you'll probably have to clean up drips and ooze out, from this gluing session anyway right.

I think there is a very good case in terms of work efficiency to bulk coat and sand the plywood items before they go into or onto the boat.

The only exceptions are usually the outside of the hull, which is so easy to coat anyhow and often has some glassing that can happen at the same time.

Most components I like to coat and sand while they are on the flat. Whether they get masked for further wood to wood gluing or any framing is done with a brush at the same time. Sand ready for painting or varnishing before the item is glued into the boat. HInt do any bevels after the item is coated - that way you create clean surfaces - The plane is the fastest way to remove epoxy.

Often with the documentation of a particular design it is possible to know where the frames are going to go. These areas can be masked up quite quickly. Eg chine log positions, frame positions on bottom and side panels. If it takes you all day to work it out it is probably most sensible to go for a secondary bond by dewaxing and sanding the whole surface.

Other tricky ways is the wet on wet then glue scenario. Really useful for closing in decks etc when it is going to be the last time you will see inside. Underside of deck and all framing inside the compartment is given three coats wet on wet (waiting between coats to allow the epoxy to go tacky) and then glue spread on mating surfaces and the deck or compartment face dropped and screwed into place.

But everything PAR said too.

MIK

P = Pig
D = Disease
J = ?

Hope you are hale and hearty soon.

If you are providing links it can't be toooo bad. Which is great.

So from the other thread

Originally Posted by PAR

Mechanical bonds on a build like this would be nearly as good, so precoating serves well.

In areas where I'm concerned about a good wood to wood, wet bond, I'll take a grinder and plow through the epoxy coating, down to raw wood and butter up the contact areas. In a glue and screw build (like this) it's less important as it's not a true taped seam job.

I use a couple of different flexibility squeegees to do curved surfaces. Brushing is painfully slow and wasteful. Rolling and tipping leaves a nice, uniform coating, but I always feel guilty about the few ounces of goo that the roller needs to wet itself out.

I don't light candles, sing chants, click my heels or bow to the west when I use goo (acolyte), though on occasion, I have prayed things would kick off and set before the rain sets in.

In short, I'd coat chines and stringers before hand just so I don't have to contort myself in some odd position trying to do so in place on the boat. Often when a piece is installed, there remain places you just can't reach with a brush, roller or other goo applying tool. I've had occasions where I wished I had an "epoxy bomb" (low yield of course) that I could place inside and area, let it go off, knowing it would coat every nook and cranny.

Originally Posted by PAR

Ideally, you want chemical bonds on everything, but this isn't practical for the average person, without careful planning.

It does no harm to coat, say the inside of a joint, then come back later and coat the rest of the part. In fact, it's often the only way to really handle things.

Staging and planning is part of the fundamental skills in boat building, which is problem solving. The first few times you use epoxy, you're going to get it all over everything, you're not going to be ready for the goo to hit the fan, so to speak and hopefully you'll manage to get the task done, before the pot smokes. After a few attempts, you'll realize that you need all your clamps and tools handy, not scattered on a work bench and that you might want to think about protecting these clamps or tools from the goo that's surely going to be on your hands when you grab it. Eventually, depending on how hard headed you are (ask your wife, she'll give you an honest acessment) you'll learn to line up your tools near the place you'll be using epoxy, have the cordless drill in a plastic sack to prevent you from having to chip off a half a gallon of dried goo, just so you can pull the trigger again, etc. This is fore thought and planning, a clear indication of problem solving.

In short, you'll have to glue things, so glue them. If the piece is precoated, then scuff up the area that will contact the joint and apply your goo. If the piece isn't precoated, then apply the goo to the joint and worry about finishing the rest of it later, when you have time., Besides, you'll probably have to clean up drips and ooze out, from this gluing session anyway right.

I think there is a very good case in terms of work efficiency to bulk coat and sand the plywood items before they go into or onto the boat.

The only exceptions are usually the outside of the hull, which is so easy to coat anyhow and often has some glassing that can happen at the same time.

Most components I like to coat and sand while they are on the flat. Whether they get masked for further wood to wood gluing or any framing is done with a brush at the same time. Sand ready for painting or varnishing before the item is glued into the boat. HInt do any bevels after the item is coated - that way you create clean surfaces - The plane is the fastest way to remove epoxy.

Often with the documentation of a particular design it is possible to know where the frames are going to go. These areas can be masked up quite quickly. Eg chine log positions, frame positions on bottom and side panels. If it takes you all day to work it out it is probably most sensible to go for a secondary bond by dewaxing and sanding the whole surface.

Other tricky ways is the wet on wet then glue scenario. Really useful for closing in decks etc when it is going to be the last time you will see inside. Underside of deck and all framing inside the compartment is given three coats wet on wet (waiting between coats to allow the epoxy to go tacky) and then glue spread on mating surfaces and the deck or compartment face dropped and screwed into place.

I liked Daddles stuff about not getting too frantic about cleaning anything but yourself

Originally Posted by Daddles

As soon as you use a brush, you're wasting epoxy in a BIG way Sadly, that's often the only tool or the best tool for the job at hand but be warned, they lay on far too much goop. Foam rollers are brilliant and have you measuring out the goop in miniscule quantities (well, not quite but they really are the Scotsman's choice ).

What you use depends on the job though. Playing cards make a cheap and effective squeegee. I've tried using the dog's tail and it's not to be recommended. Haunt the 2 dollar shops for cheap brushes and rollers. Don't muck about cleaning things, use and toss the thing out - trying to clean and reuse just has your psychiatrist reaching for the latest BMW brochure.

Epoxy is almost as bad as grease ... only almost because it's easier to get off but be warned, everything you wear (including your undies) WILL have epoxy on it after the job. Hell, I got epoxy on a shirt I'd worn the day before mixing the goop - the stuff slides through worm holes in space and time.

Always keep a bottle of the cheapest vinegar you can buy on hand - it does a ripper job of cleaning things.

BUT NOT BRUSHES - Daddles knows this backwards ... if vinegar hides up in the bristles and gets into the next epoxy job ... the epoxy won't cure. So vinegar is good for cleaning yourself and hard finished items which can dry off perfectly. Brushes can be put in a tin of appropriate solvents - cut the bristles of disposable epoxy brushes to only 25mm (1") long.

But everything PAR said too.

MIK

Vinegar is actually really only good at cleaning up resin (without hardener added) or stopping the reaction of a mix. It does do a fair job at cleaning up people as it's reasonably benign to put on your skin, though you'll smell like a pickle fro the rest of the day. Some residue will remain from vinegar clean up of tools.

I long ago stopped trying to save brushes and use a good quality chip or foam brushes. Both of these brushes need attention before use. Chip brushes are given the "tape" treatment, which is box tape (clear plastic packaging stuff) is wrapped around the bristles, then pulled off with a firm yank. This removes any loose ones. Then I clamp the bristles between two boards and cut them about half their length out of the metal binder. This makes them stiff enough to spread epoxy, rather then slather it about.

Foam brushes can be shaped to suit tasks, like reaching into holes or applying coatings to highly curved surfaces. Both chip and foam brushes come in two varieties, cheap and a little better then cheap. I've managed to find a local big box store that just happens to carry the good foam ones, so I buy them out each time they stock up. If you place the good ones, next to the poor ones, the good foam looks clearly more dense, which much smaller holes. Chip brushes also need to be ferreted out for good ones. Good ones will have twice the bristles and better binders, with less bristles falling out.

West System has technical data on sheering load for both mechanical and chemical bonds. In both cases all the test subjects (bits of wood of varying species) failed in the wood fibers, meaning the bond is sufficient, which ever you choose.

This said, some designs, particular high speed powerboats and high performance sailors will ask much more, in terms of loading on say a structural fillet, then some oak samples in a testing jig. By this I mean, if your mast step on your pocket rocket with a SA/D of 42 and a D/L of 29 (the exact figures of my little 16' hot rod, by the way), is bonded to the hull's centerline seam, which happens to be a large fillet of thickened goo and a 25 knot gust catches you with your paints down, which type of bond would you prefer to have working for you. It's these sudden, unplanned loading situations we try to design for when working up scantlings. High speed power and sail take bigger engineering risks, so the margins are smaller and things can break. If a simple technique can offer a marginal increase in strength, then take it.

Not every joint or bond will need it, but some should be highly recommended. Which ones? Each design is different. Hopefully the plans will tell you, mine do, but this isn't always the case.


As far as coatings, wet on wet is superior for long life and durability. Mechanical bonds can introduce containments or other surface prep "errors" that can challenge the integrity of the layers within the coating. I've seen three coats of mechanically bonded epoxy, flake off after some use. In one recent case, the epoxy was finished bright with good varnish, but the second to last epoxy coat was sanded very fine (600 grit) and insufficient "tooth" was available for the last coat to grab a hold of. The result was UV damaged the top coat enough for it to lift off the coat below. Fortunately, he got at it quickly and I sanded off the top coatings, down to solidly bonded epoxy, then progressed up to 320 grit for the last coats of epoxy. I don't recommend finer grit then this and most can live with 280 or 220 if done properly. A wet on wet approach, literally makes the whole of the epoxy coating, molecularly bonded to itself.